A heater is a device used for heating air. According to the principle of
operation, it is a heat exchanger that transfers energy from the heat carrier to the flow
of the supply jet. It consists of a frame, inside of which there are dense rows of tubes
connected in one or more lines. A heat carrier — hot water or steam-circulates
through them. The air passing through the frame section receives heat energy from
the hot tubes, so that it is transported through the ventilation system already heated,
which does not create the possibility of condensation or cooling of the premises.
In this paper, tests of heaters are carried out for the purpose of definition valid
heating capacities and their resistance and comparisons of these indicators with
design or catalog data. Exact heat technical and aero-dynamic tests of heaters for the
purpose of definition of surface-area factor and resistance are made in laboratories.
MT-02069964-13.04.01-73-20
Chan page № document Signature Date
Developed. Oshkin S. O
Verified
Maltsev S.A..
Analysis and calculation of heat
Lit.
4
Pages'
85
dissipation process of oscillating air
N. control
Approved
А.Ю.
Lysyakov A.I.
Levtsev A.P.
stream
IME dep. HPS, f/d, 213 group
CONTENT
INTRODUCTION
7
1 Introduction of heater system of engine
8
1.1 Current situation and progress of internal and external research of heater
system of air- heater engine
9
1.1.1 External research situation
9
1.1.2 Internal research situation
12
1.2 Development trends
16
1.3 The literature review of pulsating flow enhanced heat transfer external
research situation
18
1.3.1 Internal research situation
18
1.3.2 Internal research situation
20
1.4 Research content
23
2 The heat transfer enhancement technology
25
2.1 The classification of pulsation source
25
2.2 Pulsating flow enhancement heat transfer mechanism
26
2.2.1 The thinner boundary-layer
26
2.2.2 Increasing turbulence
27
2.2.3 Generating cavitation
28
2.2.4 Introducing forced convection
29
2.2.5 Field synergy principle
29
3 Analysis and calculation of heat dissipation process of air-heater engine
3.1 Analysis of heat transfer process of heater wall
33
33
3.1.1 Heat transfer from the high-temperature working substance to the
cylinder wall
34
3.1.2 Heat conduction from the cylinder inner wall to the outer wall
36
3.1.3 Heat transfer from the outer wall of the cylinder to the cooling air
37
4 The energy chain of the experiment equipment
42
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4.1 The equipment of the experiment
5 The equipment of the experiment
42
51
5.1 The principle of the experiment
52
5.2 The introduction of experimental device
53
5.3 The content and step of the experiment
54
6 The analysis of the experiment results
76
CONCLUSION
82
REFERENCE
83
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INTRODUCTION
The current stage of development of the world economy is directly related to
increasing energy efficiency and reducing energy consumption in all spheres of
activity, due on the one hand to energy security, and on the other-to environmental
factors of nature pollution by waste and greenhouse gases [1].
Energy consumption of buildings and structures depends to a large extent on
indicators that characterize the microclimate of premises and affect the health,
productivity and comfort of people in them. At the same time, a well-designed
heating and ventilation system of the building allows saving up to 40% of the
resources spent on maintaining the micro-climate [2].
Energy-saving measures in relation to them are measures that ensure their
minimum possible consumption of fuel and other energy sources.
To date, various technologies for heating buildings and structures have been
developed and widely used, based on the use of numerous heating devices that differ
in ways of transferring heat to the room air:
- convectors (water, electric, etc.) installed on the walls of rooms (usually
under the window) and designed to heat the room air by using the effect of natural
convection;
- underfloor heating (water, electric, etc.), providing floor heating and intended
for heating the room air both by using the effect of natural convection and by
radiation exchange with surrounding objects and fences;
-fan heaters that provide heating of the air and its artificial convection by
inducing the fan to move;
- infrared heaters installed, as a rule, under the roof and providing radiation
heating of surrounding objects and fences with subsequent convective transfer of heat
to the air of the room, etc.
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1 Introduction of heater system of engine
A heater is a device that serves to heat the air flow in a heating and ventilation
system. It is an indispensable device that can heat large warehouses, offices and
homes. The main advantages are its power and performance. Contemporary heater is
composed of the side flaps (which should be removable), tube sheets and the heattransfer elements.
Heaters are classified into two types:
Air heaters-these include the following types of heaters: water, steam, electric
and oil.
Figure 1.1 – The tubular heat exchanger
Types:
Water heaters are most often used in heating systems of huge premises. Its
main task is to heat the building in a short time. It is also highly safe and economical.
A water heater with a fan is used in heating systems that are installed in greenhouses,
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farms, sports halls and huge stores.
Steam heater-used in air conditioning, ventilation and heating systems. The
temperature of the coolant should not exceed 180 C degrees. Steam heaters are made
of carbon and stainless steel. Electric heaters-have less power than their water
counterparts. These heaters are not suitable for the heating system of large rooms no
more than 100 m2. The electric heat exchanger dries the air very much, but there is
also a positive quality of this device, it is compact and it can be easily installed in a
residential apartment. Freon and water coolers are heat exchangers for supply
ventilation. This equipment is used for air cooling.
Today, industrial heaters and water heaters with a fan are widely used: in
enterprises, factories, warehouses, offices and retail halls, which are installed in
heating and air systems. There are two types of heaters: Industrial steam CPSC;
industrial water Heater. The oil heater is used in heating systems. Use it for heating
small rooms. The advantage of this heater is that it does not dry the air, and dry air is
known to be harmful to health, especially for young children and the elderly. The
disadvantage of such a heater is that it will take more time to heat the room than for
example a thermal convector. Heaters for ventilation are widely used in enterprises
and warehouses in ventilation systems for heating the outdoor air flow, in the winter
season. [3]
1.1 Current situation and progress of internal and external research of
heater system of air- heater engine
1.1.1 External research situation
At this stage, the task is to review modern heat exchange systems. A brief
history of heat exchangers is given. The content of such concepts as heat exchange
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and heat exchangers is revealed. The types of heat exchangers and their principle of
operation are also considered. Heat exchangers are an integral part of our daily life.
They are used where cooling or heating of liquids or gases is necessary. Heat
exchange systems take place in machine, hardware and shipbuilding. Heat
exchangers are also used in the chemical and pharmaceutical industries for heat
treatment of products or for maintaining a constant temperature of process water. In
recent years, the role of heat exchangers in the areas of efficient energy use and the
application of new types of energy has significantly increased. At the end, the
prospects for the development, improvement of heat exchangers and their application
are considered. Keyword: modern heat exchange systems; heat exchange; types of
heat exchangers; prospects for the use of heat exchange systems. All heat exchange
systems are based on the principle of heat exchange. Heat transfer is a self-voluntary
(i.e., performed without compulsion) process of heat transfer that occurs between
bodies with different temperatures. Heat exchangers are devices in which heat is
transferred from one heat carrier to another. The number of heat exchangers and their
technical characteristics is calculated for each system (boiler room, ventilation,
heating, etc.) depending on the required output parameters (required temperature,
operating pressure, average temperature head). There are three ways to transfer heat:
thermal conductivity, convection, and radiation. Let's look at the history of heat
exchangers to understand how they have changed and improved over time. Despite
the fact that the rapid introduction of plate heat exchangers began only in the last
century, the first mention of them were found in frescoes that date back to the sixth
century BC. Heat exchangers of that time were used in ancient Greek baths. Since the
soldiers in the baths were washed together with their lo-shad, it was unacceptable to
cool the water by mixing cold and hot water to exclude the possibility of infection.
The solution to this problem was the use of concave metal sheets that were immersed
in containers with cold water. It is worth noting that even then the Romans were able
to improve the device almost immediately by cutting metal sheets, which accelerated
the cooling process of water. This is because the presence of barriers that cause the
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liquid to mix during its movement has a positive effect on the heat transfer process.
Then, only hundreds of years after the fall of the Roman Empire, the exchangers
returned, only this time to Mongolia, India, and the countries of Tibet. Here, a new
property of the prototypes of heat exchangers appeared. They decided to neglect the
coinage, because they thought it was just a decoration, but instead they introduced
enamel coating, which led to higher anti-corrosion properties of the metals that were
used to construct the plates. Until the end of the thirteenth century, the heat
exchanger consisted of a single plate. The first multi-plate heat exchanger was
manufactured in Russia. The new design made the device more compact and suitable
for transport. Now we should move on to modern heat exchangers. After all, any
production process causes thermal reactions and, consequently, the process of heat
exchange. Therefore, efficient use and energy savings in enterprises are currently an
important area of application of heat exchangers. For example, the use of heat energy
transferred from cogeneration plants and heat production using solar and geothermal
plants. According to the principle of operation, heat exchangers are regenerative,
regenerative and mixing. In recuperative heat exchangers, heat from the hot medium
is transferred to the cold through the dividing wall. Examples of recuperative heat
exchangers are heaters, evaporators, and condensers. In regenerative heat exchangers,
the same surface of a certain body (nozzle) is washed either with a hot or cold
coolant. In the first period, the nozzle is heated by the heating medium, and in the
second – it is cooled, giving previously accumulated heat to the heated medium.
Examples of regenerative heat exchangers: air heaters for blast furnaces and openhearth furnaces, boiler plants, gas turbine plants, heat recovery systems for
ventilation emissions). Mixing heat exchangers are designed for heat and mass
transfer processes in direct contact with heat carriers. These include: hollow, filling
and bubbling scrubbers, foam machines, irrigation chambers of air conditioning
systems, and others. Liquid-liquid, steam – liquid, gas – liquid, steam – steam, steam
– gas, steam – gas, etc. devices are divided according to the phase state of heat
carriers. According to the design features-shell-and-tube, spiral, plate, coil,
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capacitive, pipe-in-pipe, hollow, packing and Poppet columns, special, etc. In the
relative direction of movement of heat carriers-direct – current, counter-current, with
cross and mixed current. According to the mode of operation, there are devices of
continuous and periodic action. In devices of the first type, the flow rates and
parameters of heat carriers at the inlet and outlet are maintained constant in the
established thermal mode. If the parameters and flow rates of heat carriers in such
devices change over time, this mode is called transient. In recuperative devices of
periodic action, one of the heat carriers is first loaded and when the set parameter
values are reached, it is unloaded.
1.1.2 Internal research situation
In 1992, Yang Jianhua, Tang Weixin et al. [5] based on the development of a
new test universal centrifugal fan and vane angle measuring instrument, an
optimizing experimental study on the A type cooling fan vane of model 175 diesel,
and on a B type vane designed in the light of other prototypes as well as an optimum
designed C type vane, has been carried out with variation of vane numbers, inner and
outer diameter ration, inner and outer fitting angle, air blowing pattern as well as air
guiding device. The optimum designed fan and its air guiding device obtained
through the experiments haven been shown thoroughly improved performance. In
comparing with old ones, 27% increase of air blowing capacity, 57% raise of static
pressure, 22% reduction of power consumption and 3dB(A) down of noise have been
achieved. The temperature field contrast test shows that temperature of the engine
cylinder and the cylinder cover have been lowered 8-10 °С and 10-12 °С separately,
which effectively reduced the engine heat load.
In 1994, Lu Meng Li [6] discussed the reliability research of air-cooled diesel
engine, and analyzes and introduces the reliability research of 285F air-cooled diesel
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engine cooling system from the aspects of reliability design and reliability experiment.
It is considered that the cooling system performance of the 285F air-cooled diesel
engine can ensure that the diesel engine can work reliably under high temperature
conditions. It also shows that the diesel air-cooled system has a high reliability
potential and can adapt to the requirements of the 295F diesel engine with a cylinder
expansion.
In 1994, Yan Zhaoda, Hu Zhangqi et al. [7] made a comparison upon the ways
of fan installed on the flywheel on the single cylinder diesel engine. They got the
position of the fan installed on the flywheel has a great influence on the cooling effect,
when the cooling fan is integrated with the flywheel. They find the heat transfer
effect of air intake from the inside flywheel is better than air intake from the outside
flywheel. In addition, the way that air intake from the outside flywheel need enough
larger intake surface.
In 2007, Xiao Henglin [8] invented a new cooling system of an inclined
cylinder engine. Particularly a cooling device for a lubricating oil storage portion of a
small air-cooled diesel engine, The cooling device includes a body, a cylinder head, a
crankcase end cap, a lubrication system, an air guiding system. The purpose of this
invention is that a closed cooling system is provided at the bottom of the body. The
wind shield and the bottom of engine body form a cooling air duct which is a closed
ventilation chamber. When passing compressed air to forced to cool the lubricating
oil which will increase the cooling speed of oil in the oil pool. At the same time, the
cooling effect will be also improved.
In 2010, Wang Benliang [9] and others make an optimized design on the
cooling fan on the air-cooled engine. Aim at the heat load of air-cooled diesel engine
is very difficult to reduce, by syncretizing the merits of suck air cooling manner and
blow air one, the omnipotence fan which can install different shape and size vanes.
Experiments had been operated with the original vanes and the optimized vanes.
Through contrast, the conclusion that the optimized vanes can enhance the air flux by
34%, advance the pressure by 58% can be drawn. Also, the distribution of cooling air
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flow field is much sounder than that of original vanes, and the heat load of the air
cooled diesel engine can be reduced effectively.
In 2011, Zhang Yongjiu [10] investigated experimentally the design and
temperature control of the general engine forced air cooling system. The centrifugal
force air through the structure of the heat sink parameter, the cooling air system and
its subsidiary bodies adjust the experimental data before and after contrast, concluded
a universal approach to design the engine cooling system and method. Study has two
parts, the first part is investigate the distance between a flat plate heat sink module of
the louvers and heat sink C, as well as the root round R on the cooling effect; the
second part of a vertical displacement of 452CC shaft engine-based models to
explore the arrangement of the shroud and different impeller, wind system cooling
effect. By comparing the experimental data, the distance between louvers and the
heat sink will affect the heat sink and thermal distribution of heat flow values, engine
shroud arrangement different ways along the circumference of the cylinder will affect
the temperature distribution and uniformity; and different impeller, wind system will
directly affect the overall. Through this study, data analysis reasonable the distance
between wind deflector and heat sink C, larger heat sink roots round R, a reasonable
layout of the engine shroud and appropriate different impeller, wind system can
effectively reduce engine temperature and the cylinder temperature difference along
the circumference. Improving the general reliability of the engine has an important
role.
In 2013, Xu Gang, Jiang Shuli et al. [11] took single-cylinder air-cooled diesel
engine of X170F as the object. The CFD software called SC/ Tetra software is used
to simulate the three-dimensional numerical of flow in its cooling system. According
to the distribution of cooling air rate on the cylinder head, they improve and
optimized the structure of cylinder head which results in redistribution of the cooling
air on the cylinder head. The result shows that the improved scheme increase the
cooling air flow that loads into the heat area of cylinder head zone and the cooling
flow field is more reasonable to improve the cooling effect of the bottom of the
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cylinder head.
In 2013, Tian Jie an et al. [12] designed the cooling system for air-cooled
engine with CFD, it determines the cooling air flow and the radiating power required
by the engine by the traditional way and sets the preliminary design plan for radiating
fins, analyzes the design reliability of radiating fins using CFD, determines the
relationship between the resistance and flow rate according to the structure of
radiating fins, selects the fan on the basic of the relationship, finally, figures out the
bench test for the design plan under the conditions that the plan meets the CFD
calculation. The results indicate that the combination the theoretical calculation and
simulation can be used well in design of air-cooled engine.
In 2014, Tang Gangzhi et al. [13] Aiming at the problem of too high
temperature in certain locality of cylinder head, they proposed three modification
schemes to intensify its heat dissipation and low its temperature: adding internal
cooling ducts in high-temperature region, adding deflectors in cooling duct, or
changing the size of fins and the structure of outer ribs. 3D fluid-solid coupling
simulation technique is applied to the comparative analyses on the heat dissipation of
modification schemes of cylinder head. Based on the comparison results. The third
scheme is selected as the optimal scheme and a corresponding prototype is built for
carrying out the temperature measurement with far infrared thermography. The
results show that with the best modification scheme the overall heat dissipation
performance of cylinder head is intensified with the temperatures at the most heated
area obviously lowered. The experimental highest temperature of cylinder head falls
from 459.1K to 435.9, lowering by 23.2K. The simulated highest temperature of
cylinder head falls from 456.1K to 436.0 K, lowering by 20.1K; The simulation
results good agree with measured one with the largest error less than 7%.
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1.2 Development trends
It is noticed from the above literature that many scholar hope to improve the
efficiency of air heater methods. The research work was already carried out widely
on cylinder fins with various geometry and material and so on. In the study of heat
transfer, fins are generally placed on the surface that extend from an object to
increase the rate of heat transfer. Thus, adding a fin to an object increases the surface
area and can sometimes be an economical solution to heat transfer problem [14]. So,
many experimental methods are available in literature to analyze the effect of fins on
the heat transfer rate. It is found that present studies on the heat transfer of air cooling
system of engine mainly focus on changing the velocity of the air, the fin geometry
and materials, such as the size of fins, spacing between fins, the numbers of fins and
so on. In addition, as we know there are three basic modes of heat transfer: heat
conduction, thermal convection and heat radiation. The main purpose of enhanced
heat transfer research is to increase the rate of heat transfer, in order to achieve
improved energy efficiency, according to heat transfer basic heat transfer formula:
Q kAT .
(1.1)
It can be found that there are three ways to increase the efficiency of energy
transfer. They are to increase the overall heat transfer coefficient, increase the heat
transfer area, and increase the average heat transfer temperature difference between
hot and cold fluids T .
(1) Expanding the heat transfer area A. Increasing the heat transfer area is one
of the most effective ways to enhance heat transfer. However, it is not simply to
increase the heat transfer area by increasing the volume of the device, but to increase
the heat transfer area by improving the structure of the heat transfer surface. For aircooled engine cylinder, in order to increase the heat exchange area of an air-cooled
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engine cylinder, on the one hand, people add a heat sink to it. On the other hand,
more and more scholars have studied the enhanced heat transfer by changing the
shape of the heat sink. So far, the shape of heat sinks are rectangular, trapezoidal,
triangular, etc.
(2) Increasing the heat transfer temperature difference method T . There are
two methods, one is to provide the temperature of the hot fluid or to decrease the
temperature of the cold fluid. However, in actual projects, the types and temperatures
of the hot and cold fluids are constrained by factors such as the production process
and economy, and cannot be changed. There is another way to change the
arrangement of hot and cold fluid on the heat transfer surfaces to increase the heat
transfer temperature difference. For example, to arrange the hot and cold fluids
counter flow instead of parallel flow to increase the temperature difference.
(3) Improving heat transfer coefficient K. Increasing the heat transfer
coefficient to increase the amount of heat transfer is an important way to enhance
heat transfer, and is also the focus of current research. The heat transfer process of
heat exchange equipment is a complex process composed of three basic methods of
heat transfer. The heat transfer coefficient K reflecting the heat transfer capacity of
the heat exchange equipment is affected by every heat transfer process. In the
absence of fouling in the heat exchange equipment, the heat transfer coefficient of the
heat exchange equipment can be calculated by the following formula:
1 1 1
.
K h1 h2
(1.2)
Where is the thermal conductivity of solid，W/(m·K).
So, except increasing the heat transfer area, we can also enhance the heat
transfer by increasing the heat transfer coefficient. In this paper, i will investigate the
air cooling system of air-cooled engine from view of improving the heat transfer
coefficient. And, recently, some researchers find that pulsating flow can enhance heat
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transfer to some extent by increasing the heat transfer efficiency and do a larger
number of investigation.
1.3 The literature review of pulsating flow enhanced heat transfer,
external research situation
1.3.1 Internal research situation
In 1929, E G Richardson [15] and other people applied hot wire anemometer to
measure the velocity of the tube steady flow and pulsating flow, comparing with the
average velocity gradient theoretical values and measured values in the cross-section
of the tube found that the pulsating speed "annular effect". That is, the velocity of the
fluid at the wall is higher than the tube center and the entire cross-section of the
velocity distribution is more flat than steady flow velocity distribution. This also
marks the beginning of pulsating heat transfer.
In 1980, Robert C. Herndon et al. [16] used two types of pulsator to pulse the
flow in a double-pipe heat exchanger. Condensing stream in the shell was used to
heat water, which flowed in the center pipe at rates corresponding to Reynolds
numbers from 6600 to 28000. The frequency of the pulsations was varied from 50 to
1000 cycles/min, and the results showed that there was an increase in the heat transfer
coefficient on the water side upon pulsing. In addition, they found that there was a
maximum in the average enhancement as a function of the pulsation frequency. At
lower flow rates showed two maximum value in the average enhancement as a
function of the pulsation frequency. However, as the flow rate of the pulsed stream
was increased, the two maximum value disappeared and only one maximum value.
In 1990, M. R. Mackley [17] and other people performed an experimental heat
transfer measurements for the flow of a lubricating oil on the tube side of a shell and
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tube heat exchanger. The investigation are made for the case where there is a steady
net flow through the smooth walled tube and where periodically spaced baffles have
been inserted. The results showed when flow oscillations are superimposed on the net
flow. The Nusselt number increase significant for the system when both flow
oscillation and baffles are present.
In 1997, Moschandreou et al. [18] analyzed the pulsating flow in the circular
pipe full hot development zone of the constant wall temperature heat flux and
concluded that the difference between the average Nusselt number (Nuo) and the
corresponding Nusselt number (Nust) is increasing for the high frequency pulsating
flow .
In 2008, Elsayed A.M. Elshafei et al. [19] investigated the heat transfer
characteristic of pulsating turbulent air flow in a pipe which was heated at uniform
heat flux. The experiments were performed over a ranges of 10 4<Re<4*104 and
6.6≤f≤68Hz. The experiments indicate that Nu is strongly affected by pulsation
frequency and Reynolds number. Its local valve either increases or decreases over
that of the steady flow. The higher valves of the local heat transfer coefficient
occurred in the entrance of the test tube. It is observed also that the relative mean Nu
either increases or decreases, depending on the frequency range. The percentage of
maximum enhancement in ƞm is about 9% at Re=37100, f=13.3 ; and the percentage
of maximum reduction in ƞm is about 12% at detected for Re=13350, f=42.5.
In 2012, Zohir [20] investigated the effect of pulsation on the heat transfer rates,
for turbulence water stream with upstream of different amplitudes, in a double-pipe
heat exchanger for both parallel and counter flows. The experiment runs at pulsation
frequency over a range of 140 cpm < f < 260 cpm, Reynolds number: 3855 < Re <
11570, length of stroke: 6 cm < Ls< 18.5 cm. They found the heat transfer of counter
heat exchanger can be higher than that of parallel flow. The results reveal the
enhancement in relative average Nusselt number up to 10 times and 8 times for
higher amplitude and higher pulsation frequencies, respectively, for counter flow and
parallel flow.
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1.3.2 Internal research situation
In 1989, The effect of pulsating flow on the heat transfer of sugar juice and its
mechanism were studied by Deng Xiqun [21], Yang Zhuo and Li Xingren. They
obtained pulsating flow is an effective heat transfer method. It was more suitable to
strengthen viscous fluid. In turbulent region, the effect of pulsating flow on the heat
transfer will be weakened with the increasing of Reynolds number; the intensity of
turbulence increasing, the boundary layer thinning and cavitation are the main
mechanism of pulsating heat transfer.
In 1996, T. S. Zhao and P. Cheng [22] simulated the laminar pulsating heat
transfer in the finite length tube with uniform wall temperature. The four parametersthe pulsating amplitude, the pulsating frequency, the aspect ratio (the ratio of pipe
length to diameter) and Pr are the important factors that affect pulsating heat transfer .
In 2003, Zheng Jun et al. [23] Pulsating flow in a pipe was experimentally
investigated to determine the effect of pulsation on the rate of heat transfer. The
influence of water flow rate, pulsation properties and pressure drop was carefully
studied. In order to adjust the pulsating parameters, a self-oscillator was designed in
which the length of the resonator and the length of outlet nozzle could be adjusted.
The results show that the rate of heat transfer is strongly affected by both the
hydrodynamic parameters and the configuration of the resonator. With the increase of
the water flow rate and the length of the chamber, the heat transfer is enhanced.
When water flow rate G<0.3kg/s, the dimensionless heat transfer factor E<1. When
G>0.3kg/s, E>1, which enhanced the heat transfer. And the maximum valve of the
increment of the dimensionless heat transfer factor ∆E=0.21. When no-dimension
length of the resonator L ranges from 0.25 to 0.30, there is fluctuation of the heat
transfer. When L>0.3, the E is increasing significantly. And the L=0,35, the E reach
to maximum valve. In addition, there exist an optimal length of the outlet nozzle at
which the heat transfer can be enhanced most effectively.
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In 2005, Yu Yielong and Li Zhixin [24] investigated numerical analysis on
convective heat transfer of laminar tube with constant heat flux and constant wall
temperature. The simulation results of constant heat flux boundary condition were in
agreement with the analytical solution very well. The numerical results showed that
the pulsating flow in a circular tube under constant heat flux or under constant wall
temperature conditions can result in the fluctuation of velocity ,temperature of fluid
and Nusselt number around the steady ones, the large pulsating amplitude and the
smaller the pulsating frequency, the large fluctuation will be. But the overall effect
does not strengthen the pulsating flow, the pulsating flow neither strengthen the heat
transfer nor weaken the heat transfer. Their time-averaged are equal to the steady
ones at the same Reynolds number.
In 2009, Gao Hong and Liu Juan-fang [25] performed an experimental study of
heat transfer enhancement by pulsating fluid and designed a self- oscillator where the
continuous flow of the fluid was transferred into pulsation flow. The pulsating flow
water passes through a single pipe heat electrically. They changed the hydraulic
parameters and the length of the resonator and outlet nozzle. The water velocity
ranges from 5.0 m/s to 7.5 m/s; the length of the resonator ranges from 10 mm to 14
mm; the length of outlet nozzle ranges from 12 mm to 25 mm. The experiments
revealed that the scale of the enhancement ratio is 1.01~1.07 and the stable
enhancement ratio ranges from 1.1 to 1.4. In other words, under the appropriate
hydraulic parameters and configuration of the resonator, the heat transfer coefficient
can increase 10%-40% comparing with the normal case when the oscillator was
removed.
In 2011, Xu Jie [26] investigated the pulsating flow on pipe flow heat transfer
by experimental testing and numerical simulation and analyzed the effect of Reynolds
number, the pulsation frequency and amplitude to heat transfer. Reynolds number
ranges from 500 to 3200, the pulsation frequency ranges from 0 to 12 Hz, as well the
distance of the pulser to inlet of the testing tube changes from 0.5 to 1.5m. The results
show that: in the laminar flow, the pulsation flow enhances the heat transfer of the
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pipe flow and the enhancement trend of heat transfer is increasing with the increasing
of the frequency. However, with the increasing of the Reynolds number, the
enhancement trend of the heat transfer weakens. When the flow state is in turbulent
circumstances, the pulsation flow weakens the heat transfer of the pipe flow. With the
increasing of the Reynolds number, the effect is increasing gradually.
In 2013, Li Si-wen, Li Hua, Yang Zang-jian et al. [27] investigated
experimentally pulsating flow in a pipe under turbulent conditions to determine the
effect of pulsation on the rate of heat transfer. The experiments were performed over
a ranges of 16 ≤υ≤40 m/s (4.6·104<Re<11.6·104) and 0≤f≤100Hz. The results show
that the pulsation frequency, pulsation amplitude and Reynolds number have a
significant impact on the heat transfer enhancement. The heat transfer is increasing as
the increasing of Reynolds number and pulsation amplitude. However the
strengthening effect is not infinitely increased. When the flow velocity reaches a
certain degree, the strengthening effect will weaken. At the same time, as the
pulsation amplitude is beyond the certain value which can enhance the heat transfer.
While the best pulsation frequency exists respectively in the range of 0 to 20 Hz and
80 to 100 Hz. The maximum percentage of enhancement heat transfer is 36.1% at
f=10 Hz.
In 2016, Hongsheng Yuan et al. [28] performed a theoretical studies on heat
transfer of pulsating laminar flow in pipes with wall thermal inertia. They found that
pulsating laminar flow can weaken heat transfer and the effects are small under the
high frequency, large Prandtl number, small pulsation amplitude and small heat
capacity. In addition, comparing the result of pulsating flow in circular pipe with in
two parallel plates, the circular pipes have lower temperature but higher temperature
gradient. The maximum temperature gradient of fluid in pipe is away from pipe wall
while the maximum gradient of parallel plates is near the plate wall. The pulsating
effects are a little more remarkable for circular tube which are caused by the distinct
boundary conditions.
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From the literature review. It is found that studies on pulsating flow to some
certain extent could increase heat transfer. Although, some literature have a
disagreement with this point. On the one hand, some of them are caused by the
relatively narrow scope of the parameters. On the other hand, some of them are not.
So far, the mechanism of heat transfer enhancement by pulsed flow is still ambiguous.
However. This supplies a new idea to investigate the influence of heat transfer by
imposing pulsation on the steady flow. So, it is necessary to study the influence of
pulsating flow on the cooling system. In this paper, we will conduct this research to
investigate pulsating heat transfer for the air cooling system of petrol engine.
Meanwhile, this work will be taken up on these aspects to cover the research gaps.
1.4 Research content
This paper is mainly to study the performance of pulsating air heater system.
From the previous literature, we get that the fluctuating flow can affect heat transfer
to some extent and increase the efficiency of heat transfer. Relatively speaking, in the
air heating system of a room with air heating, the air passes through the heater where
it increases the temperature. However, based on the research results, in this paper I
will introduce vibrations in a stationary flow to change the steady flow of air in the
oscillating flow and add a vortex that is expected to reduce the thickness of the
sublayer and increase heat transfer. In this way, the drive and blinds will create air
vibrations before it starts to leave the heating pipe, which will increase heat transfer
and increase the heat transfer coefficient using this method.
The purpose of this study is as follows.
(1) experimentally investigate the effect of heat transfer of the heater by
creating a fluctuating air flow.
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(2) experimentally determine the effect of the frequency of vibrations on the
heat transfer of the air heating system in the ventilation system.
This experiment will be performed by both stationary flow and oscillating flow
using two methods. Comparing a stationary flow with a fluctuating flow, we will
conduct an experimental analysis of the influence of the frequency of vibrations on
heat transfer.
Conclusion
In this present dissertation, I will try to work from the point of view of
improving the heat transfer coefficient. The effect of fluctuating flow on the air
heating system will be experimentally investigated. And work will be done on these
aspects to cover research gaps and present results based on systematic research.
Thus, the purpose of this study is to determine the degree of increasing the
efficiency of heat exchange in the mode of pulsating air flow.
To achieve this goal, the following tasks are set:
- perform an information search for existing ways to increase the efficiency of
heat exchange on the surface of heaters;
- develop a prototype of an experimental installation including a heater and a
device for organizing the fluctuating flow of air, select the required measuring
equipment, assemble and adjust its operating modes;
- develop a mathematical model of the energy chain …;
- select measurement methods and tools;
- perform experimental studies of the operation of an experimental heater with
a fluctuating air flow.
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2 The heat transfer enhancement technology
As a rule, the fan heater operates in several modes. Each is characterized by
water consumption, cooling rate, and air consumption. It is possible to connect to a
European-class Central heating line (60 ° C) and a special 150 ° C steam boiler.
A heater is a device used for heating air. According to the principle of
operation, it is a heat exchanger that transfers energy from the heat carrier to the flow
of the supply jet. It consists of a frame, inside of which there are dense rows of tubes
connected in one or more lines. A heat carrier — hot water or steam-circulates
through them. The air passing through the frame section receives heat energy from
the hot tubes, so that it is transported through the ventilation system already heated,
which does not create the possibility of condensation or cooling of the premises.
In this paper, tests of heaters are carried out for the purpose of definition valid
heating capacities and their resistance and comparisons of these indicators with
design or catalog data. Exact heat technical and aero-dynamic tests of heaters for the
purpose of definition of surface-area factor and resistance are made in laboratories.
2.1 The classification of pulsation source
The pulsation source is divided into self-oscillation and forced pulsation. Selfoscillation is a device that generates pulsation by changing the structural shape of the
pipeline. This pulsation requires no external force. At present, there are selfoscillating sources, including a non-return valve system and a self-oscillation system.
Forced pulsation sources are devices that pulsates fluids by consuming energy. Need
to use extra force, such as mechanical force, electromagnetic force. The more
common forced pulsation source are diaphragm pumps, solenoid valves,
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reciprocating pumps, combined rotary vane valves, etc, (table 1).
Table 1 - Some generating pulsation method used by scholars
Date
Researcher
Pulsation source
Frequency
1943
Martinelli
Reciprocating pump
13-265 cycles/min
1952
West
Reciprocating pump
100 cycles/min
1961
Lemlich
Solenoid valve
0-210 cycles/min
1971
Keil
Positive displacement pump
0.4-1.1Hz
1979
Karamercan
Piston and cylinder
0-300 cycles/min
1980
Robert C. Herndon
Ball valve and shower head
0-1000 cycles/min
2.2 Pulsating flow enhancement heat transfer mechanism
So far, the mechanism of pulsating flow enhancement is not clear, however,
there are some factors that have been recognized by research field.
2.2.1 The thinner boundary-layer
Convection heat transfer mostly refers to the heat transfer between the fluid and
the solid wall, and its heat transfer rate is closely related to the fluid properties and
the condition of the boundary layer. The temperature difference is very large in this
thin layer next to the wall. Meanwhile, the thermal resistance of convection heat
transfer is mainly concentrated in a thin layer. In this thin layer, the fluid maintains
the characteristics of laminar flow and is therefore called the viscous laminar flow
bottom layer. It is generally conceded that the heat transfer through the laminar film
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occurs by means of conduction. The fluid in the viscous laminar bottom layer has a
large temperature gradient. Once the heat passes through the layer, it is easily carried
away by the core fluid. Therefore, the heat transfer strength mainly depends on the
thickness and characteristics of the viscous laminar bottom layer. As we found in the
case of turbulent flow, the heat transfer intensity is much greater than the heat
transfer intensity in the case of laminar flow. Because the turbulence can thin the
boundary layer to a certain extant. So the greater the turbulence of the fluid, the better
the heat transfer effect, the thinner the viscous laminar flow bottom layer, the smaller
the convection heat resistance.
2.2.2 Increasing turbulence
With the development of the boundary layer and the increase in the thickness
of the boundary layer, the relative viscous force of the inertial force in the boundary
layer will gradually increase, resulting in loss of stability in the flow in the boundary
layer, from laminar flow to turbulent flow. It has been found that pulsating flow is
associated with a periodic pressure gradient reversal, which causes an increase in
radial and longitudinal mixing during part of the pulse cycle which in turn decreases
the film thickness in the pulsed stream. The disturbance and mixing of fluids reflect
the degree of turbulence. The increase of turbulence intensity will increase the
convective heat transfer efficiency, and the turbulence velocity has a close
relationship with the velocity shear layer. The radial mixing has an important
influence on the convection heat transfer to a large extent. It is the presence of flow in
the radial direction of the fluid motion that causes the heat exchange between the side
wall and the fluid core and takes away the heat. The flow of the pulse causes the
pressure of the fluid at various locations in the tube flow to change periodically as the
flow rate changes. When the flow is strengthened, the fluid will intensity turbulence
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in the direction of movement and in the diameter direction. At the same time, the
Reynolds number instantaneously increases in the direction of movement, so the
turbulence intensity also increases. When the flow weakens, the rate of change of
pressure and velocity in the direction of motion will change significantly, which will
also increase the turbulence intensity of the flow. When this theory is applied to the
laminar flow of tubes, it will have a relatively large effect on the heat transfer. When
the laminar flow of tubes is posed to pulsating, the heat transfer enhancement effect is
most obvious. However, this state does not continue. When the Reynolds number
increases to a certain extent, the pulsating flow will reduce the strengthening of the
pipe flow. This is due to the fact that the increased turbulence of the flow and the
originally high turbulence partially cancel each other out. Therefore, the pulseenhanced heat transfer is most effective for laminar flow, and transitional flow and
turbulent flow are worse. For the Reynolds number-large flow, the effect of pulsation
is not obvious.
2.2.3 Generating cavitation
Some scholars found the pulsations can cause the fluid next to the tube wall to
cavitate in the water cooling system. And they claim cavitation is very important
factor to enhance heat transfer for pulsating flow. Cavitation is the formation of many
small bubbles on the tube surface of the heat exchanger during the low-pressure
portion of the pulsation cycle, the flow is suddenly interrupted or forced to change
direction which result to the pressure in fluid pressure drops below the vapor pressure
of the fluid in the boundary layer next to the tube wall [4]. So the bubbles will
originate where the pressure drops below the vapor pressure and occur cavitation.
The bubbles act as carriers of latent heat by moving toward the bulk and giving up
their latent heat as sensible heat upon collapsing. The periodic formation and collapse
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of these bubbles agitates the boundary layer and thus increases the rate heat transfer.
Lemlich [29] has also proposed that cavitation increases heat transfer by
transferring the heat of vaporization necessary to produce the vapor bubbles from the
tube wall. The bubbles then detach from the tube wall and travel into the bulk of the
fluid stream where they collapse, giving up their latent heat.
Therefore, it is believed that cavitation is able to increase heat transfer in the
laminar sub-layer next to the tube wall and enter the main fluid stream they distrupt
the laminar sub-layer, causing mixing to occur in the layer and the renewable of
laminar sub-layer. This may be an additional mode of energy transfer occurring as a
result of cavitation in the pulsating flow [27].
2.2.4 Introducing forced convection
In steady flow, the heat transfer is conduction rather than convection in the
boundary layer. However, when imposing the pulsation to steady flow, the pressure
periodic variation produce forced circulation in the fluid and increase the effective
heat transfer by promoting the formation of eddies, thus introducing convective in the
boundary layer [4].
2.2.5 Field synergy principle
In 1998, professor Guo [30] from Tsinghua university proposed a novel
concept that heat exchange between fluid and wall has a close relationship with the
included the angle between the velocity filed and temperature gradient vectors. When
the velocity field and temperature gradient filed reach full field coordination, the heat
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transfer gets optimal result. The Nusselt number exists the upper and lower limit,
respectively, Nu=Re·Pr and Nu=0, depending on the coordination degree of the
velocity filed and temperature gradient filed. Generally, the heat transfer efficiency is
between the upper and lower limit. This theory is called field synergy principle. This
theory compares the process of convection heat transfer to the addition of an internal
heat source in the heat transfer and compares the fluid flow with an equivalent heat
source. The theory shows that the strength of the convection heat transfer is directly
proportional to the strength of the equivalent heat source. It is not only related to the
temperature difference between fluid and the pipe wall surface, the speed of the fluid
flow, and the fluid's own medium characteristics. It is also related to the angle
between the fluid flow velocity and the heat flow vector. Because the value of the
equivalent heat source is indefinite, the flow can not only enhance the heat transfer
effect, but also weaken the heat transfer effect.
Generally, the energy equation:
T
T
T T T T
k
k
v
w
k
q.
y
z x x y y z z
x
Cp u
(2.1)
The energy conservation equation of 2-D boundary-layer steady flow:
T
T T
k
.
v
y y y
x
Cp u
(2.1a)
The energy conservation equation of 1-D steady-state heat conduction with
heat sources:
q
T
k
.
y y
(2.1b)
It is easy to find that the convective term in the energy equation for the
boundary layer flow corresponds to the heat source term in heat conduction equation.
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The integral of the equation(2.1a) over the thermal boundary layer thickness
leads to
t
0
T
T
T
dy k
v
.
y
y
x
Cp u
(2.2)
The equation (2.2) may be rewritten with the convection term in the vector
form:
t
T
T
T
dy k
v
.
y
y
x
Cp u
0
(2.3)
Where the thermophysical properties , Cp are assured constant.
Introducing the non-dimension array
U
T
, T
,
U
T Tw t
U
U x
Cp
1
U T dy
y
y
t
, T Tw ,
(2.4)
T
T Tw y
0
x.
(2.5)
The non-dimensionalization of equation (2.3) leads to
1
Re x Pr U T dy Nu x .
0
1
Re x Pr U T dy Nu xU T U T cos .
0
(2.6)
(2.7)
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1
Re x Pr U T cos dy Nu x ,
0
(2.8)
where β - is the included angle between the dimensionless velocity and
temperature gradient vector.
From the view of equations above, we can see the strength of convection heat
transfer is not only related with Re and Pr, but also related with the included angle
between the dimensionless velocity and temperature gradient vector. When β<90 ̊, the
smaller the β, the more the strength of convection heat transfer. When β=0, there are
maximum strength of convection heat transfer.
So, there are three ways to raise the strength of heat sources/convective terms,
and consequently to enhance the heat transfer [42]:
(1) Increasing Reynolds number and / or Prandtl number;
(2) Increasing the fullness of dimensionless velocity and / or temperature
profiles;
(3) Reducing the included angle between the dimensionless velocity and
temperature gradient vector (when β < 90 ̊ ).
Conclusion
There are many ways to enhance the heat transfer, we can choose suitable
method according to the specific experiment condition. So far, the mechanism of the
pulsating flow enhance the heat transfer is not completely clear. However, the above
five statements have been universally recognized. From the existing research
mechanism, we obtain the some new ideas to enhance heat transfer and get a deeper
understanding of heat transfer enhancement.
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3 Analysis and calculation of heat dissipation process of air-heat engine
Using these devices, the room temperature is controlled. In mathematical
modeling of air conditioning systems, non-linear models should not be neglected
properties of heating installations, as this will inevitably lead to inadequacy the
resulting model and the inaccuracies of the synthesized automatic control system.
Given the large number of types of heaters, a variety of implementation schemes air
conditioning systems and methods for managing heat transfer were highlighted in the
work main types of disturbing and controlling effects for air conditioning systems
air's. Based on the block diagram of the generalized supply air conditioning system
systems of the equation of heat and mass balance of the heat carrier and the air that
most accurately reflects all the processes taking place. The properties of heating
installations that change dynamically over time were shown in a wide range of
coolant flow control in heat exchanger tubes. Recommendations on the choice of the
method of hydraulic strapping of the heater are also formed. Air conditioning systems
in terms of improving the regulator setting and increasing the accuracy of the
automatic control system
3.1 Analysis of heat transfer process of heater wall
For an air-heat engine, the process of heat transfer of a high-temperature
working fluid through the wall of the heat exchanger to the cooling air is a more
complex and heat-transfer process, as shown in figure 3-1.to enhance heat transfer,
air-heat engines are equipped with radiators-heat exchangers. The entire heat transfer
process includes the following three aspects.
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Figure 3.1 - The heat transfer process of the air heat engine
3.1.1 Heat transfer from the high-temperature working substance to the
cylinder wall
When the engine is in operation, the high-temperature working fluid in the
cylinder continuously flushes the peripheral wall of the cylinder with different
temperatures, and strong convection heat transfer is performed between the two.
Convection heat transfer.
The heat flow calculation of the convection heat transfer, currently using
Newton cooling formula, its mathematical expression is:
Qc h1' (T f 1 Tw1 ) F1 ,
(3.1)
where h' - is the average convection heat transfer coefficient;
1
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T f 1 is the instantaneous average temperature of the working medium in the
cylinder, K, which is a function of the crank angle, can be determined by using the
gas state equation according to the engine indicating diagram;
Tw1 is the average temperature of the wall, K;
F1 is the heat exchange surface area in contact with the working medium, m 2,
which is also a function of the crank angle.
Radiation heat transfer.
The radiation heat exchange between the high temperature working medium in
the heater and the wall has two phenomena: gas radiation and flame radiation. The
radiant heat flux is the sum of the two.
Qr Qs Q f ,
(3.2)
where Qs - is the heat of gas radiation, W.
Q f is the heat of flame radiation, W.
In summary, the amount of heat transfer Qw from the high-temperature working
medium to the peripheral wall of the cylinder is the sum of the convection heat
transfer amount Qc , the gas radiation heat exchange amount Qs and the flame
radiation heat exchange amount Q f .
Qw Qc Qs Q f
h1 (T f 1 Tw1 ) F1.
(3.3)
where Tw1 - is the average temperature of the cylinder wall, K. Experiments have
shown that the magnitude of its change over time is very small and can be
approximated as a fixed value;
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h1 - is the average heat transfer coefficient, W/(m2.K).
Since there are many factors affecting the heat transfer process of the working
fluid to the peripheral wall of the cylinder, when the heat transfer calculation is
actually carried out, the complexity of the heat exchange process and the difficulty in
calculation are comprehensively concentrated on the average heat transfer coefficient.
The engine heat transfer data are comprehensively considered. Since the radiation
heat transfer quantity is much smaller than the convection heat transfer quantity, in
order to facilitate, the radiation heat transfer is often calculated by increasing the
convection heat transfer coefficient.
3.1.2 Heat conduction from the cylinder inner wall to the outer wall
Assuming that the cylinder height and the circumferential direction have the
same temperature, the heat flow only changes in the radial direction. In fact,
regardless of the temperature of height or circumferential direction are different, the
heat flow consists of radial, axial and tangential heat flow. However, under normal
circumstances, the sum of the latter two is less than 1/5-1/10 of the former and can be
ignored. Secondly. The ratio of the inner diameter and the outer diameter of the
cylinder is generally not more than 1/2, and it can be treated as a flat wall conduction
heat. The error does not exceed 1%. Therefore, the flow of heat transfer through the
peripheral wall of the cylinder can be obtained according to the law of heat transfer
proposed by Fourier in 1882, that is, the heat flow is proportional to the wall area F1
perpendicular to the direction of heat flow and the temperature difference of the outer
wall surface and inner wall surface (Tw1-Tw2). It is inversely proportional to the wall
thickness δ(m). which is
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Qw
Tw1 Tw 2
F1 ,
(3.4)
where the scale factor λ [W/(m·K)] - is called thermal conductivity. For each
substance, λ has a specific value obtained by checking documents, which is generally
determined experimentally.
3.1.3 Heat transfer from the outer wall of the cylinder to the cooling air
The heat transfer between the cooling fins of the outer wall of the cylinder and
the cooling air is a convective heat transfer process in which the fluid directly
contacts with the solid wall with different temperatures. Since the temperature of the
heat sink is not high, the radiation to the surrounding environment is negligible.
Therefore, the amount of heat transfer can be calculated according to Newton's
cooling formula, which is
Figure 3.2 - The heat transfer of heat sinks with cooling air
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Qw h2 (Tw 2 T f 2 ) F2 ,
(3.5)
where h2 - is the average heat transfer coefficient of heat sink and cooling air;
Tw 2 - is the temperature of the heat sink wall;
T f 2 - is the average temperature of the cooling air;
F2 - is the surface area of the heat sink wall, [m2], is the sum of the surface area
of the root between the two heat sinks F0 and the surface area of the heat sink
Ff .
If the engine is running under a stable load and speed, the entire heat transfer
process can be considered as a stable heat transfer process, and the energy
conservation law should be
Qw h1 (T f 1 Tw1 ) F1
(T T ) F h2 (Tw 2 T f 2 ) F2 .
w1 w 2 1
(3.6)
Assuming that the temperature of the entire fin surface is equal to the base
surface temperature, ie, the fin efficiency f is equal to 1.
T f 1 Tw1
Qw
.
h1 F1
Tw1 Tw 2
Qw
Tw 2 T f 2
(3.7)
.
(3.8)
Qw
.
F2 0
(3.9)
F
1
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T f 1 - T f 2 Qw (
1
1
1
).
h1 F1 F F2 h2
1
(3.10)
Qw
Tf 1 - Tf 2
.
1
1
1
h1 F1 F F2 h2
1
(3.11)
Rib effect coefficient is the ratio of ribbed surface to smooth surface area, ie.
F2 F1 .
Qw F1
Tf 1 - Tf 2
.
1 1
1
h1 h0
(3.12)
(3.13)
The larger rib effect coefficient , the small the thermal resistance, the larger
heat transfer coefficient.
F2 F0 F f ,
(3.14)
where F0 - is the root area between fins and fins;
F f - is the area of the protruding fins.
When the temperature of the entire fin surface is not equal to the base surface
temperature, ie, the fin efficiency f is not equal to 1.
Qw h1 (T f 1 Tw1 ) F1 ,
(3.15)
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Qw
(T T ) F ,
w1 w 2 1
Qw h2 (Tw 2 T f 2 ) F0 h2 (Tw 2 T f 2 ) F f f h2 (Tw 2 T f 2 ) F2 0 ,
0
F0 F f f
F2
.
(3.16)
(3.17)
(3.18)
So
Qw F1
T f 1 -T f 2
,
1 1
1
h1 h2 0
(3.19)
where f - is fin efficiency;
0 is overall fin surface efficiency;
is the rib effect coefficient;
is the conduction resistance;
1 h1 is the heat exchange resistance between high temperature fluid and
cylinder;
1 h2 0 is the heat exchange resistance between heat sinks and cooling air.
Due to 1 , the thermal resistance of the finned surface 1 h2 t is smaller
than the thermal resistance without finned surface. This is the reason that putting fins
on the side where the heat transfer coefficient is small can enhance the heat transfer
when there is a large gap between h1 and h2 . To increase the coefficient of rib effect
coefficient, in principle, two approaches can be followed: one is to use thin ribs,
narrows the spacing of the fins to increase the number of fins, and the second is to
use long fins to enlarge the surface area of each fin. However, the thinner, denser, and
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higher fins of the design, will bring more difficulties to the processing of the heat
sinks, and too dense heat sinks will hinder the flow of air between the heat sinks and
even make the flow dead zone, which will weaken the heat transfer effect.
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4 The energy chain of the experiment equipment
4.1 The equipment of the experiment
In this paper, we consider the influence of the pulse mode of the coolant flow
on the heat transfer "heater-environment". To study this issue, the main thermal
scheme of the experimental installation is shown in Figure 4.1.
Convention: 1– boiler, 2– heat exchanger, 3– fan, 4– blinds, 5 – closer, 6 –
sump, 7 – pump, 8 – crane.
Figure 4.1– Schematic diagram of the experimental setup
The unit is designed to heat the air using a heat exchanger in which the heat
carrier circulates, hot water.
The installation works as follows: cold water enters the boller 1, where it is
heated to a certain temperature and enters the circuit, a heat exchanger 2 is installed
in the circuit, which is blown by a hair dryer 3. The pulse mode of hot water supply
to the heat exchanger and the cleanliness of the opening and closing of the blinds 4
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will help us to increase efficiency. With the closer 5, we adjust the opening of the
blinds, a sump 6 and a circulation pump 7 are installed in the circuit for rust, and we
use a crane 8 to stop the operation of the circuit.
Experimental research includes: design and construction of the air tube. In
which thermodynamic processes will take place. the main task will be to find the
optimal frequency of opening and closing blinds and pulse supply of coolant. There
will be similar optimal parameters: the speed of the coolant, pressure, temperature,
and length of the pipeline. In the course of the study, for a better understanding of the
scheme, it was decided to study 2 characteristics of hydraulic and thermal, in order to
better understand the nature of the forces arising and to more accurately determine
the required parameters on the obtained model.
In the first power circuit the hydraulic characteristic at the moment of closing
of the shock valve is considered. The main interest is the energy converter
throughwhich the pressure is converted into force, and the flow rate in the flow
velocity.
Figure 4.2– Energy circuit 1
Considered the second energy diagram, the backward wave surge with the
opening of the valve.
The resulting circuit of the first stage is divided into links. Next, at each level
we find the values that affect the basic parameters and change them depending on
various factors.
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Figure 4.3– Energy circuit with variable parameters
We get links in the energy circuit 1. For each we make a system of equations.
For the first link:
1.
Step
p r1v m v1 r2v12 p3
2
.
v l p1 v1
2.
Step
p3 p3 p30
;
v1 v1 v10
p1 m v1 r2v10 2r2v10 v1 p3 p30
2
;
p1 m v1 2r2 v10 v1 p3
p 2lr1v10 m v1 (m 4lr1r2v10 ) v1 (2r1v10 2r2v10 ) v1 r1v10 2r1lv10 p3 p3 p30
2
2
.
v lm v1 2lr2v10 v1 lp3 v10 v1
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3.
Step
p 2lr1v10 m v1 (m 4lr1r2v10 ) v1 (2r1v10 2r2v10 ) v1 r1v10 2r1lv10 p3 p3 p30
2
2
a1 v1 a2 v1 a3 v1 a4 b1 p3 b2 p3 b3
(a1 p 2 a2 p a3 1)v1 ( p ) (b1 p b2 1) p3 ( p ) .
4.
Step
p3 ( p)
a1 p 2 a2 p a3 1
Z ( p)
.
v1 ( p)
b1 p b2 1
5.
Step
a12 a2 j a3 1
Z ( j )
;
b1 j b2 1
Z ( j)
a1b22 a12 a2b12 a3b2 a3 b2 1 (a1b13 a2b2 a2 a3b1 b1) j
b122 (b2 1)2
a1b22 a12 a2b12 a3b2 a3 b2 1
Re ( j)
;
b122 (b2 1)2
a1b13 a2b2 a2 a3b1 b1
I m ( j )
j .
b122 (b2 1)2
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We obtain the amplitude-frequency function of the energy circuit:
A( j) Re ( j)2 I m ( j)2 .
Get the phase-frequency function of the energy circuit:
( j) arg tg
I m ( j )
Re ( j) .
The resulting circuit of the first stage is divided into links. Next, at each level
we find the values that affect the basic parameters and change them depending on
various factors.
Figure 4.4 – Heat transfer circuit
1.
Step
t r1q r2 q1 t2
q l t1 q1
.
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2.
Step
t2 t20 t2
q1 q10 q1 ;
t1 r2 q1 t2
.
t1 r2 q1 t2
3.
Step
q l t2 lr2 q1 q1 q10
a1 t2 b1 q1 b2 q1 b3
;
a1 pt2 ( p) (b1 p b2 1)q1 ( p) ;
Z ( p)
4.
t2 ( p )
b p b2 1
1
q2 ( p )
a1 p
.
Step
Z ( j )
b1 j b2 1 b1 (b2 1) j
a1 j
a1
.
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5.
Step
b1
a1 ;
Re ( j)
I m ( j)
6.
(b2 1) j
a1
.
Step
A( j) Re ( j)2 I m ( j)2
( j) arg tg
I m ( j )
Re ( j)
;
.
Table 4.1 – The parameters of the energy chain.
V0
0,27
r1
111
m
1
P0
0,01
l
0,000009
r2
111
Table 4.2 – The output parameters of the energy chain 1
Re( j)
1
2
3
4
5
6
7
8
9
10
-59,4398
-59,4393
-59,4385
-59,4374
-59,4359
-59,4341
-59,4319
-59,4295
-59,4267
-59,4236
Im( j)
-0,59889
-1,19777
-1,79665
-2,39554
-2,99442
-3,5933
-4,19218
-4,79106
-5,38994
-5,98882
A( j)
59,44285
59,45141
59,46567
59,48563
59,51127
59,54261
59,57962
59,62229
59,67062
59,72459
( j)
-0,01008
-0,02015
-0,03022
-0,04028
-0,05034
-0,06039
-0,07042
-0,08044
-0,09045
-0,10044
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A( j)
Figure 4.5 – Amplitude-frequency function of the energy circuit 1
( j)
Figure 4.5 – Phase-frequency function of the energy circuit 1
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Table 4.3 – Выходные параметры энергетической цепи
№
Re( j)
Im( j)
A( j)
( j)
1
-111
222222,2
222222,2
1,570297
2
-111
444444,4
444444,5
1,570547
3
-111
666666,7
666666,7
1,57063
4
-111
888888,9
888888,9
1,570671
5
-111
1111111
1111111
1,570696
6
-111
1333333
1333333
1,570713
7
-111
1555556
1555556
1,570725
8
-111
1777778
1777778
1,570734
9
-111
2000000
2000000
1,570741
10
-111
2222222
2222222
1,570746
A( j)
Figure 4.6 – Amplitude-frequency function of the energy circuit 2
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( j)
Figure 4.7 – Phase-frequency function of the energy circuit 2
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5 The equipment of the experiment
This chapter will present the experimental principle of a heater with a
fluctuating air flow, as well as an experimental circuit diagram, basic tests and
devices. The device, connection, and pyrometer will be described, as well as
experimental methods and procedures. At the same time, a method for processing
experimental data is described.
5.1 The principle of the experiment
In this installation, cold air will flow through the vent holes and blow into the
space of the air tube, then it will pass through the walls of the heated calorimeter and
increase the temperature, at the exit we will get heated air with a changed temperature,
the air flow at the exit will be regulated by means of blinds with a drive.
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5.2 The introduction of experimental device
In this paper, we consider the influence of the pulse mode of the coolant flow on the
heat transfer "heater-environment". To study this issue, the main thermal scheme of
the experimental installation is shown in Fig. 5.1.
Convention: 1 – electric boiler, 2 – hydraulic accumulator, 3 – pressure gauge,
4 – electromagnetic flow converter, 5 – manual balancing valve, 6 – circulation
pump, 7 and 16 – thermal resistance converters designed to measure the temperature
of the coolant after and before the heater, 8 – fan of the heater block, 9, 11 and 13 –
thermal resistance converters designed to measure the temperature of the air flow at
different points of the heater block, 10 and 12 – water - air heat exchangers of the
heater block 1st and 2nd heating stages, 14 – air damper, 15 – electric air damper.
Figure 5.1 – Experimental setup diagram
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5.3 The content and step of the experiment
The experimental installation consists of a block of a heater, a source of
thermal energy-an electric boiler and a measuring complex (figure 5.2). The heater
unit is a frame-panel construction unit that includes a fan that provides air flow in the
range of 50-350 m3/h and two water-air heat exchangers installed in series. The
coolant flow is selected according to the counter-current scheme.
Figure 5.2 – Photo of the appearance of the heater unit and the complex,
including a circulation pump, a hydraulic accumulator, a balancing valve and an
electromagnetic fluid flow сonverter.
The measuring complex consists of an electromagnetic pre-educator of the
liquid flow Masterflow 4, thermal converters of the resistance 7 and 16 for measuring
the temperature of the coolant after and before the heat exchangers of the heater and
9, 11 and 13 for measuring the temperature of the air flow at different points of the
heater block (figure 5.3).
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Figure 5.3 – The part of the appearance of the experimental installation
To enure the circulation of the heated medium, the circuit has a Wilo 6 pump.
Changing the flow rate of the heated medium is possible with the help of a manual
balancing valve 5. Smoothing possible hydraulic shock in the system is perceived by
the membrane of the hydraulic accumulator 2, also included in the scheme (figure
5.4).
Figure 5.4 – The part of the appearance of the experimental installation
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Creating a fluctuating air flow through the section of the heater block is
organized by us using a standard ventilation grate and an electric drive, the frequency
of which is set by the setpoints of the operating periods and the time relay. The
electrical power supply diagram of the electric drive is shown in figure 5.5.
Convention: 1 – DC power supply 12 V, 2 and 5 – voltage relay, 3 – electric
drive, 4 – time relay RVC-1M
Figure 5.5 – Electrical power supply diagram for the ventilation grid electric
drive
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Figure 5.6 – General view of measurement sensors
DS sensors are designed for continuous temperature measurement of liquid,
vapor and gaseous media, bulk materials and solids in various industries, as well as in
heating, ventilation and air conditioning systems.
There are two types of thermal converters: General industrial and specialized.
The sensors can be cable-connected or with a switching head, in various design
versions that allow them to be mounted on a pipe, on a wall, immersed in the
medium, etc.
Sensors convert a change in temperature into a change in electrical resistance
to direct current. They consist of one or two sensing elements (hereinafter CE)
connected to the switching head or cable terminal and placed in a protective
armature. Depending on the measured temperature range, the PE can be: platinum
wire 100 P or platinum film Pt 100 (Pt 500, Pt 1000), copper wire 50 M or 100 M.
The main technical characteristics of the DTS XX4 and DTS XX5 type of sensors are
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shown in table 5.1.
Operating conditions of switching units: rooms with non-regulated climatic
conditions and (or) sheds, at atmospheric pressure from 84 to 106.7 kPa, with a
temperature in the range of at least minus 40 to plus 85 °C and a relative humidity of
no more than 95 % at +35 °C and lower temperatures without condensation.
Table 5.1 – Main technical characteristics of DTS XX4 and DTS XX5 sensors
Value
Characteristic
DTSHX4
1
2
Nominal static characteristic
(NSC)
50М;
100М
Measured temperature range,
-50…+150
°C
Class of admission
В; С
The index of thermal inertia
Number of sensitive elements,
PCs.
The performance of the sensor
relative to the housing
The execution of the switching
head
Type of threaded connection
Material
of
protective
reinforcement
Degree
of
protection
(according to GOST 14254)
Average time to failure, 1 hour,
at least
Average service life, years, not
less
3
50P;
100P;
Pt 100
Pt 500
Pt 1000
4
50М;
100М
5
50P;
100P;
Pt 100
Pt 500
Pt 1000
-50…+250
-50…+180
-50…+500
А; В; С
В; С
А; В; С
10…30
1
2
two-wire
three-wire
four-wire
The scheme of internal
connections of the conductors
Cable output length
DTSHH5
isolated
0.2 m-standard
up to 20 m-on request
-
-
plastic,
metal
metric thread,
pipe thread
steel 12X1810T
steel 12X1810T
brass
IP54; IP65
35000
8
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We accept as a means of measuring the temperature of the supply air and the
circulating coolant temperature Converter DTS035-50 M. B3. 60 (figure 4). To
measure the temperature of the cooling medium, we will use a thermal Converter
DTS314-50 M. B3. 40/2 (figure 5.7).
Figure 5.7 – General view of the dts035-50M thermal Converter.V3. 60
Figure 5.8 – General view of the dts314-50M thermal Converter.V3. 40/2
To measure the flow of coolant in the system, the scheme includes a primary
flow Converter-an electromagnetic Converter " mA-sterflou "(modification with a
current output of 4...20 mA) produced by NPO"Prompribor". The Converter converts
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the liquid flow rate to an analog signal of 4.20 mA in the range of 0.020. 5.0 m3 / h
(figure 5.9).
Figure 5.9 – Photo of the appearance of the Masterflow flow Converter
To input analog signals to a personal computer, we used the MVA 8 input
module (figure 5.10). It can also be used to build automatic systems for monitoring
and regulating production and technological processes in various areas of industry,
transport, agriculture, utilities and other sectors of the national economy.
The housing contains a printed circuit Board on which the elements of the
device's circuit are located.
On the front panel of the device there are two LEDs that serve to indicate the
power connection and indicate the operation of the RS-485 network interface.
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Figure 5.10 – Input module analog measuring MVA 8
The device performs the following main functions:
- measurement of physical parameters of the object controlled by input primary
converters;
- digital filtering of the measured parameters from industrial im-pulse
interference;
- correction of measured parameters to eliminate errors of primary converters;
- formation of an alarm signal when a fault is detected in the primary
converters;
- transmitting information to the computer about the values of the values
measured by the sensors or the values obtained after converting these values;
- changing the values of its programmable parameters using the configuration
program;
- saving the set programmable parameters in non-volatile memory when the
power supply voltage is switched off MVA 8;
- reading of position sensors (resistive and current type) and contact discrete
sensors.
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Operating conditions:
- closed explosion-proof rooms without aggressive vapors and gases;
- ambient temperature from + 1 °C to + 50 °C;
- upper limit of relative humidity-80 % at 25 °C and lower temperatures
without condensation;
- atmospheric pressure - from 86 to 106.7 kPa.
Primary transducers (sensors) are designed to control the physical parameters
of an object (temperature, pressure, flow, etc.) and convert them into electrical
signals that are optimal for further processing.
As input sensors of the device can be used:
- thermal resistance converters;
- thermocouples (thermoelectric converters);
- active converters with an analog output signal in the form of a constant
voltage or current;
the position sensors of the actuators;
- dry contacts of the relay or switch.
Thermal resistance converters (hereinafter referred to as TS) are used for
measuring the ambient temperature at the sensor installation site. The principle of
operation of such sensors is based on the existence of a reproducible and stable
dependence of the active resistance on temperature for a number of metals. As a
material for manufacturing vehicles in the industry, specially processed copper (for
TSM sensors), platinum (for TSP sensors) or Nickel (for TSN sensors) wire is most
often used.
The output parameters of the vehicle are determined by their nominal static
characteristics (hereinafter NSC), standardized by GOST R 50353-92. The main
parameters of the NSC are: the initial resistance of the sensor R0, measured at 0 °C,
and the temperature coefficient of resistance W100, defined as the ratio of the
resistance of the sensor, measured at 100 °C, to its resistance, measured at 0°C. Due
to the fact that the NSC of thermal resistance converters are non – linear functions
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(for TSM in the region of negative temperatures, and for TSP in the entire range), the
device provides means for linearization of readings.
In order to avoid the influence of the resistances of the connecting wires on the
results of temperature measurement, the sensor should be connected to the device
using a three-wire circuit. With this scheme, two wires connecting it to the device are
connected simultaneously to one of the terminals of the vehicle, and a third
connecting wire is connected to the other terminal. To fully compensate for the
influence of connecting wires on the measurement results, it is necessary that their
resistances are equal to each other (it is sufficient to use single wires of equal length).
In some cases, it is necessary to connect the vehicle using a two-wire scheme
rather than a three-wire one, for example, in order to use existing communication
lines on the object.
Thermoelectric converters (hereinafter referred to as TP) as well as thermal
resistance converters are used for temperature measurement. The principle of
operation of thermocouples is based on the Seebeck effect, according to which the
heating of the junction point of two dissimilar conductors causes the appearance of an
electromotive force at the opposite ends of this chain-Ter – moeds. The value of the
thermal EMF is initially determined by the chemical composition of the conductors
and also depends on the heating temperature.
NSCS of various types of thermocouples are standardized by GOST R 8.5852001. Since the characteristics of all thermocouples are more or less non-linear
functions, the device provides means for linearization of readings.
The junction point of dissimilar conductors is called the working junction of
the thermocouple, and their ends are free ends or, sometimes, cold junction. The
working junction of the thermocouple is located in the place selected for temperature
control, and the free ends are connected to the measuring device. If it is not possible
to connect the free ends directly to the contacts of the MVA 8 (for example, due to
their distance from each other), then the connection of the thermocouple with the
device must be performed by means of compensating thermoelectric wires or cables,
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with the mandatory observance of the polarity of their inclusion. The need to use such
wires is due to the fact that the EMF of a thermocouple depends not only on the
temperature of the working junction, but also on the temperature of its free ends, the
value of which is controlled by a special sensor located in the device. In this case, the
use of thermoelectric cables allows you to increase the length of the conductors of the
pair and "transfer" its free ends to the terminal block MVA 8.
Active converters with an analog output signal are used in accordance with the
purpose of the sensor for measuring physical parameters such as pressure,
temperature, flow, level, etc. The output signals of such sensors can be either the DC
voltage changing according to a linear law, or the value of the current itself.
Active sensors can be powered either from a built-in DC source with an output
voltage of 24 ± 3 V, or from an external power supply.
Connection of sensors with signal output at a constant voltage (-50,0...50,0 mV
or 0...1.0 volt) may be connected to the device contacts, and sensors with output in
the form of current - only after the installation of shunt resistor 100 Ohm (tolerance
not more than 0.1 %). As a shunt, it is recommended to use highly stable resistors
with a minimum value of the temperature coefficient of resistance, for example, type
C2-9V.
Position sensors are designed to determine the current position (degree of
opening or closing) of shut-off and control valves, valves, scrapers, etc.when
adjusting process parameters.
Resistive position sensors are most commonly used in the industry. In sensors
of this type, an alternating resistance resistor is used as a sensing element, the slider
of which is mechanically connected to the regulating part of the actuator.
The MVA 8 is capable of processing signals from resistive sensors with a
resistance of up to 900 Ohms or 2.0 kOhm.
Sensors are also used that generate an output signal in the form of a linearly
varying current, the value of which depends on the position of the actuator at the
moment.
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The device is capable of processing sensor signals with a current output of 0...5
mA, 0.. .20 mA and 4 ... 20 mA.
Up to 16 discrete sensors, called "Dry contacts", can be connected to the MVA
8. As sensors can be vyklyuchat Lee, button, contact group relay, etc. Each analog
input can be used to connect two discrete sensors.
Any resistors with the same nominal value of 60-90 Ohms can be used as shunt
resistors.
The device can be used simultaneously to work with various types of sensorsresistance thermal converters, thermocouples, etc. In this case, it is not important to
which input of the MVA 8 will be connected to a sensor of one type or another, since
all eight inputs of the device are absolutely identical.
After connection, the sensors are assigned serial numbers of the device inputs
to which they are connected (input 1 corresponds to sensor # 1, input 2-sensor # 2,
etc.). the Type of each sensor is set by the user in the form of a digital code in the in-t
programmable parameter when preparing the device for operation.
During operation, the device monitors the operability of the primary converters
connected to it and sends an error message via the RS-485 network interface if any of
them is detected (figure 5.11).
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Figure 5.11 – RS-85 Network interface
Errors are generated by:
- when working with thermal resistance converters in the event of their failure
or short circuit;
- when working with thermoelectric converters in the event of their break, as
well as when the temperature of the free ends of the thermocouples increases above
90 °C or when it decreases below +1 °C;
- when working with any type of primary transducers, if the measurement
results are obtained that go beyond the limits of the control range set for this sensor.
To program the MVA 8 device, you must connect it via the RS-485 ARIES AC
4 interface adapter to a personal computer and connect power to the device.
Programming of the analog MVA8 input module was performed using the
program "MVA 8 Configurator".
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Programming procedure for the device:
1) Launch the program "MBA Configurator 8".
2) Setting the program connection with the device.
3) Create a new configuration and then open it from the file.
4) Setting the sensor type for each input used, the polling period, and other
characteristics;
5) Setting the upper and lower limits of the measured range of sensors;
6) Recording the configuration in the device.
After starting, the program establishes a connection with the device. The
connection is determined when sending commands to switch to the ARIES Protocol.
The connection is established based on the network parameters that were set when the
program was last launched.
If the connection is established, the Main program window opens. If the
program was not able to establish a connection with the device and transfer the MVA
8 to work using the ARIES Protocol, the window for setting network settings opens
(figure 5.12).
The table (in the upper part of the window) shows information about the
current network settings of the device (a description of the setting, the name of the
corresponding parameter and its value). Parameter values can be set directly in the
table.
When the "Connect" button is clicked, the device search procedure is started to
establish a connection with the device.the search process uses all available
communication protocols at the set network settings and speed. When the device
responds for the first time, the search procedure is stopped.
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Figure 5.12 – Network settings Window
When you click the network Scan button, the network scan procedure starts to
establish communication over all available protocols, with an interruption in
exchange rates, starting from the exchange rate of 2400 and then up to the speed of
115200. Other network settings (parity, data word length, etc.) do not change during
scanning. Thus, the "network Scan" mode is an extended communication setup mode.
The first time the device is clicked, the scan stops.
When the factory network settings button is clicked, the Factory network
settings are set and the connection attempt is repeated.
When you click the "Work offline" button, the program stops trying to
communicate with the device; the main window of the Configurator opens. This
disables the automatic reading of the network parameters.
When you click Exit, the program exits and the window closes.
After the connection is established (immediately or after changing the network
settings), or after the offline mode is selected, the main window of the configuration
program opens (figure 5.13), containing the menu, toolbar, and workspace. In the
workspace, as a hierarchically organized list, the configuration of MBA 8 is
displayed, which contains two main sections (two branches of the program tree):
Device parameters and program Parameters.
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Figure 5.13 – Main window of the Configurator program
The main window includes a title line that shows the "Configurator MVA 8"
and the name of the current configuration of the device, menu and toolbar, the display
area of the list of sections and program settings and device settings (in the left part of
the window) and the display of parameter values (on the right).
The "device Parameters" section includes four folders:
- General parameters of the device-contains non-editable information
parameters (device name, SOFTWARE version, and a message about the reason for
restarting the device);
- network parameters of the device-contains a list of network parameters that
determine the operation of the device via the RS-485 interface;
- inputs-contains 8 subfolders Input #1, Input #2 ... Input #8 with individual
parameters of the MVA 8 inputs and a common CJ -. C parameter for all inputs;
- input polling - allows you to view and save the values measured by the
device. These values are displayed in the program window in a converted form: for
thermal converters and thermocouples, the temperature measured in degrees Celsius
is output; for active sensors, the values are recalculated in accordance with the units
of the measurement range.
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Figure 5.14 – VAZ 2108 stove fan
The centrifugal fan the snail combines reliability of design, excellent indicators
of power and simplicity of operation. The basic purpose of the supercharger consists
in movement of big air masses
Table 5.3.2 – Main technical characteristics of VAZ 2108 stove fan
Parameters
Current values for operation
Rated voltage
Rated power
Maximum current
Rated speed
Weight
12 V
90 W
14.0 A
4100 min -1
1,0 kg
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Figure 5.15 – Copper and aluminum heat exchangers
Recuperative heat exchangers are characterized by the fact that in them
processes of heat transfer from the one environment to another proceed through the
wall separating these Wednesdays. liquid-air heat exchangers, in which the heat
carrier is the hot or cold water In such heat-exchange apparatus, transfer of warmth
from more heated environment to less heated proceeds at the same time through their
change wall. The specified heat exchangers working at hot and cold water.
a)
• Core type: prefabricated
• Core material: aluminum
• The size of the core, mm 200*191*42
b)
• Core type: prefabricated
• Core material: copper
• The size of the core, mm 200*191*42
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Figure 5.16 – Hot water boiler handmade
The boiler in this installation maintains a constant temperature in the circuit.
The heating range is from 0 to 100 degrees. A constant temperature is maintained
using a thermostat. Powered by a 220 V network.
When planning experiments, they are usually divided into active ones, when
the study is carried out at specially set values of input parameters and, as a rule, on a
special experimental installation, and passive ones, when the measurement results are
obtained on working objects, usually without installing additional devices or
assigning special tests. As a result of planning experiments, the number and sequence
of experiments that ensure the achievement of the set research goals with the required
accuracy and reliability is determined. The experimental setup is always specialized,
unique and is built taking into account the specific features of the object and specific
research tasks.
The accuracy of the measurement is determined by the degree to which the
measurement results correspond to the actual value of the measured value. The
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difference between these two values is called the absolute measurement error. The
ratio of absolute error to the true value, expressed as a percentage, is called the
relative error.The reasons for errors are changes that occur during testing, the
temperature of the outdoor air or in the object. Can you name the three sources of
errors:
sensor of the primary measuring signal;
- measuring devices for air temperature and liquid flow in the system;
- the experimenter himself, who, due to various circumstances, may not
correctly take the readings of the devices.
To solve this problem, we will conduct an active experiment with the use of an
experimental installation, the scheme of which is given in the third Chapter. We will
record the results of the experimental study in a table.
An experiment to determine the efficiency of exhaust air heating in pulsating
and continuous modes of air flow was conducted on June 12, 2020, under the
following climatic conditions-internal air parameters in the laboratory: the
temperature varied from 26.0 to 26.3°C, relative humidity - from 28 to 31 %, the
initial temperature of the heated medium varied from 11.6 to 15.7 °C.
The experiment was performed under two operating modes of the fan 226 and
278 m3 / h by means of a switch of operating modes.
The air flow rate through the experimental unit was determined as a result of
measurements of the flow rate in two different modes of operation of the ventilator
using the MES-200A meteometer (figures 5.17, 5.18).
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Figure 5.17 – Photo of the process of measuring the air flow velocity in the section of
the experimental installation
Figure 5.18 – Photo of the air flow speed reading on the MES-200A weather meter
display
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The air flow velocity at the first fan speed was 1.19 m / s, and at the second
speed it was 1.45 m/s. The internal dimensions of the live section of the experimental
unit are 260x205 mm. The calculation determines the air flow rate when working at
the first speed of 226 m3 / h, at the second speed-278 m3/h.
The pulsating air flow mode was created using a standard ventilation grate with
an adjustable live section. The grating has a flap, which, by means of a rigid rod,
makes reciprocating movements by means of an electric drive, thereby opening and
closing the way for air movement.
At the initial stage of the experiment, the unit was switched on with the fan
running at the first speed. The liquid flow regime varied from a minimum flow rate of
50 kg/h to a maximum flow rate of 400 kg/h. Under the same operating conditions of
the fan and the liquid flow mode, the parameters of the air and the heated liquid were
recorded in pulsating and continuous air flows. Then the fan operation was switched
to the second speed and the display was repeated.
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6 The analysis of the experiment results
Figure 6.1 – Fan operation mode-1 speed
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Figure 6.2 – Fan operation mode-2 speed
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Figure 6.3 – Fan operation mode-3 speed
The efficiency of the heater in pulsating and continuous air flows was
determined by the formula:
Е
2 1
100 % ,
t1 1
(6.1)
where is the temperature of the heated medium before the heater, °C;
- temperature of the heated medium after the heater, °C;
- exhaust air temperature at the inlet to the heater, °C.
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The results of calculating the efficiency of a prototype heater with continuous
and pulsating air supply modes are summarized in tables 6.1 and 6.2.
Table 6.1 – Results of calculating the effectiveness of a multi-factor experiment with
a continuous flow of air
A continuous stream of air
L,
m3 /
h
G,
kg /
h
τ1, ℃
τ2, ℃
t1, ℃
t2, ℃
Temperature difference ,
ºС
t3, ℃
226
50
40,8
36
25,2
28,6
34,9
9,70
226
100
46,2
37,8
25,2
28
34,8
9,60
226
150
41,8
38,8
25,3
29,2
37,2
11,90
226
200
49
46,1
25,4
31,6
41,8
16,40
278
50
42,2
33,4
27,1
28,7
30,4
3,30
278
100
49,3
39,2
25,5
28,1
35,8
10,30
278
150
42,7
38,9
25,5
28,8
36,3
10,80
278
200
46,6
42,7
25,5
30,3
39,3
13,80
343
50
46,7
36,9
27,4
29,6
31,6
4,20
343
100
46,3
38,7
27,4
30,1
32,3
4,90
343
150
50,2
42,9
27,7
31,3
34
6,30
343
200
46,7
42,5
27,7
32,5
35,5
7,80
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Table 6.2 – Results of calculating the efficiency of a multi-factor experiment with a
fluctuating air flow
Pulsating air flow
L,
m3 /
h
226
226
226
226
278
278
278
278
343
343
343
343
G,
kg /
h
50
100
150
200
50
100
150
200
50
100
150
200
τ1, ℃
τ2, ℃
40,8
46,2
41,8
49
42,2
49,3
42,7
46,6
46,7
46,3
50,2
46,7
36
37,8
38,8
46,1
33,4
39,2
38,9
42,7
36,9
38,7
42,9
42,5
t1, ℃
25,2
25,2
25,3
25,4
27,1
25,5
25,5
25,5
27,4
27,4
27,7
27,7
t2, ℃
28,7
28,1
29,2
31,6
28,8
28,2
28,9
30,4
29,7
30,2
31,4
32,6
t3, ℃
35,1
34,9
37,3
42
30,5
36
36,5
39,5
31,7
32,4
34,2
35,7
Temperature difference,
ºС
9,90
9,70
12,00
16,60
3,40
10,50
11,00
14,00
4,30
5,00
6,50
8,00
The results obtained are shown graphically in figures 6.4 and 6.5 for illustrative
purposes.
Figure 6.4 – Comparative graph of the heating efficiency dependence in continuous
and pulsating air flows with a valve capacity of 226 – 343 m3/h
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Figure 6.5 – Comparative graph of the heating efficiency dependence in continuous
and pulsating air flows
As can be seen from the results of processing the experiment, the heating
efficiency in the pulsating mode increases slightly from 1.29 to 2.54%.
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CONCLUSION
In this way, the characteristics of the air-conditioning unit will change with
different coolant flow rates and outdoor air temperature. Despite the universal
prevalence of heaters in indoor air conditioning systems and the simplified
mathematical description, for the synthesis of an adequate control system, it is
necessary to take into account clearly nonlinear, dynamically changing over time
parameters of the heater. This circumstance should be mandatory in cases where the
mathematical model is not of a conceptual theoretical nature, but requires practical
testing on an object with a wide range of regulation of the system's heating capacity.
In the course of this work, the problems related to this work, possible ways to
solve it were described. The scheme of experimental installation is developed and its
detailed description and the principle of work is stated. The power circuits of the
installation were composed, and individual links were described. Mathematical
transformations were done with power circuits and complex resistances, frequency
functions, amplitude – frequency and phase – frequency characteristics were
obtained. The frequency characteristics of the circuit are constructed.
Based on the obtained graphs, it is possible to trace the relationship of two
different characteristics. The graphs show that in Ω=1 we get the peak of the
hydraulic characteristic and the minimum of the thermal characteristic. This effect is
due to the fact that at the moment there is a water hammer. And it turns out a surge in
pressure and a decline in heat flow.
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REFERENCE
1) Energy strategy of Russia until 2030 (approved by order of the Government
of the Russian Federation dated November 13, 2009 N 1715-p).
2) Lepesh G. V. energy Saving in life - saving systems. non-provision of
buildings and structures/ G. V. Lepesh – - SPb.: Publishing house FINEC, 2014 – 437
p.
3) All about ventilation and heating seositi.ru: [Electronic resource]. Moscow,
2015-2020. URL: https://seositi.ru/kondicionirovanie/kalorifer.html (date of request:
5.06.2020).
4) Mr. Manir Alam, Assoc. Prof. Mrs. M. Durga Sushmitha, Design and
Analysis of Engine Cylinder Fins of Varying Geometry and Material, International
Journal of Compute Engineering in Research Trends, Vol.3, Issue.2, pp.76-80(2016).
5) Yang Jianhua, Tang Weixin，Experimental Research on Air Cooled Diesel
Engine Cooling System，Tractor, No.5, pp:11-16, 1992.
6) Lu Meng Li, Study on Reliability of Cooling System for 285F Air-cooled
Diesel Engine, Vehicle Engine, Vol 4, pp:50-55, 1994.
7) Yan Zhaoda, Hu Zhangqi, Sheng Hongquan et al. On Technologic Current
Status of the Small Air-cooled Diesel Engines, Neiranji Gongcheng, Vol.15,
No.2,pp:25-33, 1994.
8) Xiao Henglin, Air-cooled Diesel Engine Cooling system, State Intellectual
Property Office of the P.R.C, CN101082294A, 2007.
9) Wang Benliang, Tang Chufeng, Tang Weixin, Optimization Design on
Cooling System Omnipotent Fan of Samll Air-cooled Diesel Engine, Hunan
Agricultural Machinery, Vol.37, No.2, pp:21-24, 2010.
10) Zhang Yongjiu, The Design and Temperature Control of the General
Engine Forced Air Cooling System, Tianjin university, 2011.
11) Xu Gang, Jiang Shuli, Dong Fei, Bai Shu, Design and Investigation on
Cooling System of Single-cylinder Air-cooled Diesel Based on CFD Analysis, Small
Page
MT – 02069964 -13.04.01- 73 -20
Ch.
Page
No document’s Signature Data
83
Internal Combustion Engine and Vehicle Technique, Vol.40, No.6, pp:62-65, 2013.
12) Tian Jiean, Peng Wei, Fei Hongqing et al., Design of Cooling System for
Forced Air — Cooled Diesel Engine, I. C. E & Powerplant, Vol.30, No.2, pp.811(2013).
13) Tang Gangzhi, Zhang Li, Chen Feihu, et al. Improvement of Cooling
System and Liquid-solid Coupling Heat Transfer Simulation of Air-cooling Engines,
Automotive Engineering, Vol.36, No.4, 2014.
14) Chityala Praveen, E.Rama Krishna Rao, Effect of Heat Transfer Rate in
Different Fins with Varying Materials, International Journal of Advanced
Technology and Innovative Research, Vol.08, Issue.15, pp:2986-2994 (2016).
15) E G Richardson, E Tyler. The Transverse Velocity Gradient near the
Mouths of Pipes in Which an Alternating or Continuous Flow of Air is Established.
in:Proceedings of the Physical Society. Landon. 1929.42(231):1-15.
16) Robert C. Herndon, Preston E. Hubble, John L. Gainer, Two Pulsators for
Increasing Heat Transfer, Ind. Eng. Chem. Process Des. Dev, Vol.19, No.3, P:405410 ,1980.
17) M. R. Mackley, G. M. Tweddle and I. D. Wyatt, Experimental Heat
Transfer Measurements Pulsatile Flow in Baffled Tubes, Chemical Engineering
Science, Vol. 45, No. 5, pp. 1237-1242, 1990.
18) Moschandreou T, Zamir M, Heat Transfer in a Tube with Pulsating Flow
and Constant Heat Flux. Int.Heat Mass Transfer, 1997.
19) Elsayed A.M. Elshafei, M. Safwat Mohamed, H. Mansour, M.Sakr,
Experimental Study of Heat Transfer in Pulsating Turbulent Flow in a Pipe ,
International Journal of Heat and Fluid Flow, 29(2008) 1029-1038.
20) A. E. Zohir, Heat Transfer Characteristics in a Heat Exchanger for
Turbulence Pulsating Water Flow with Different Amplitudes, Journal of American
Science, Vol.8, No.2, 2012.
21) Deng XQ, Yang Z, Li H. Effects of Pulse Flow on Heat Transfer of Juice
and Its Mechanism. Journal of Qiqihar University, Vol.5, No.3, pp. 16-22 , 1989.
Page
MT – 02069964 -13.04.01- 73 -20
Ch.
Page
No document’s Signature Data
84
22) T.S.Zhao, P.Cheng. Oscillating Heat Transfer in a Pipe Subjected to
Laminar Reciprocating Flow[J]. ASME Journal of Heat Transfer 1996,118:592-597.
23) Zheng Jun , Zeng dan-ling, Wang ping, Gao hong, Experimental Study of
Heat Transfer Enhancement with Pulsating Flow, Journal of Thermal Science and
Technology, Vol.2, No.3, 2003.
24) Yu Jie-long, Li Zhi-xin, Numerical Analysis on Convective Heat Transfer
of Pulsating Flow in a Circular Tube, Journal of Engineering Thermophysics, Vol.26,
No.2, 2005.
25) Gao Hong, Liu Juan-fang, Experimental Study of Heat Transfer
Enhancement by Pulsating Fluid, Journal of Chongqing University of Arts and
Sciences(Natural Science Edition) , Vol.28, No.2, 2009.
26) Xu jie, Study into Effect of Pulsating Flow on Heat Transfer in a Pipe,
Beijing University Of Civil Engineering And Architecture, 2011.
27) Li Si-wen, Li Hua, Yang Zang-jian et al. Experimental Study on
Influencing Factors of Pulsating Heat Transfer in Turbulent Flow in a Pipe, Journal
of Zhejiang university of technology Vol.41, No.4, 2013.
28) Hongsheng Yuan, Sichao Tan, Jing Wen, Nailing Zhuang, Heat Transfer of
Pulsating Laminar Flow in Pipes with Wall Thermal Inertia, International Journal of
Thermal Science, 99(2016), pp.152-160.
29) Lemlich R., Armour J. C., Enhancement of Heat Transfer by Flow
Pulsations, Chern. Eng. Prop. Symp, 1965, (61):83.
30) Deng XQ, Yang Z, Li H. Effects of Pulse Flow on Heat Transfer of Juice
and Its Mechanism. Journal of Qiqihar University, Vol.5, No.3, pp. 16-22 , 1989.
Page
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