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International Journal For Emerging Trends in Engineering and Management Research (IJETEMR) –Volume II
Issue 1- 21st January 2016
Cooling System for Industrial and Commercial
Purpose Using Thermoelectric Module
Pavan Hood#1
1
Mtech Scholar & ETC Department RTMNU
JHULELAL INSTITUTE OF TECHNOLOGY – Lonara Nagpur
[email protected]
Abstract— Air cooling is significantly important in relatively
humid countries. So there is a need to bring down the humidity.
Different types of cooling systems are available in the market.
They can be classified as air cooled, water cooled, refrigerated,
and thermoelectric cooled.
Although Thermoelectric (TE) property was discovered
about two centuries ago thermoelectric devices have only been
commercialized during recent years. The applications of TE vary
from small refrigerators and electronics package cooling to
Avionic instrumentation illumination control and thermal
imaging cameras. Lately a dramatic increase in the applications
of TE coolers in the industry has been observed. It includes water
chillers, cold plates, portable insulin coolers, portable beverage
containers and etc. The research paper is basically focused on
how to overcome demerits of HVAC system in industries by
thermoelectric cooling system.
Keywords– HVAC, TEC, Peltier effect, Seebeck effect.
I.
Introduction
Thermoelectric refrigerator sometimes called a thermoelectric
cooler module or Peltier cooler is a semi conductor based
electric component that functions as a small heat pump. By
applying a low voltage direct current (DC) power source to a
thermoelectric cooler module, heat will be moved through the
module from one side to the other. One module face,
therefore, will be cooled while the opposite face
simultaneously is heated. Both thermoelectric refrigerators
and mechanical refrigerators are governed by the same
fundamental laws of thermodynamics and both refrigeration
systems; although considerably different in form, function in
accordance with the same principles. In a mechanical
refrigeration unit, a compressor raises the pressure of a
refrigerant and circulates the refrigerant through the system.
In the refrigerated chamber, the refrigerant boils and in the
process of changing to a vapor, the refrigerant absorbs heat
causing the chamber to become cold. The heat absorbed in the
chamber is moved to the condenser where it is transferred to
the environment from the condensing refrigerant. In a
thermoelectric cooling system, a doped semi-conductor
material essentially takes the place of the refrigerant, the
condenser is replaced by a finned heat sink, and the
compressor is replaced by a Direct Current (DC) power
source. The application of Direct Current (DC) power to the
thermoelectric cooler modules causes electrons to move
through the semi-conductor material. At the cold end of the
semi-conductor material, heat is absorbed by the electron
movement, moved through the material, and expelled at the
hot end. Since the hot end of the material is physically
attached to a heat sink, the heat is passed from the material to
the heat sink and then in turn, transferred to the environment.
II.
Literature Survey
Thermoelectric phenomenon was discovered nearly two
hundred years ago. Since last sixty years the practical
applications from thermoelectric had been exploited.
The first breakthrough that would eventually be used to form
the thermoelectric effect was discovered in 1820. Several
other breakthroughs in the field were discovered over the next
few decades but their relationship was not realized for a full
38 years. William Thomson discovered that heat is absorbed
or produced when current flows in material with a certain
temperature gradient and that the heat is proportional to both
the electric current and the temperature gradient. His
publication linked all the discoveries from the preceding
decades.
Kryotherm, (2007) Studies based on thermoelectric cooling
unit for thermostatic body on refrigerated trucks were
conducted by Bulat and Nekhoroshev (2003). In this study a
comparison between the thermoelectric cooling units with
vapour-compression installations was also made, where it
showed that cost price of thermoelectric unit is four-five times
cheaper than vapour-compression cooling units. The cooling
power obtained for TE cooling was same when compared to
compression cooling units.
McStravick, et.al (2009) had invented a medical travel pack
with cooling system. The invention has helped people
suffering from chronic disease to travel with proper supply of
medicine kept at proper temperature. These insulated
container using TE modules comprises of a cold plate, heat
sink, fan and a temperature sensor.
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International Journal For Emerging Trends in Engineering and Management Research (IJETEMR) –Volume II
Issue 1- 21st January 2016
III.
Thermoelectric Effects
A. Peltier Effect
In 1834, a French watchmaker and part time physicist, Jean
Charles Athanase Peltier found that an electrical current
would produce heating or cooling at the junction of two
dissimilar metals. In 1838 Lenz showed that depending on the
direction of current flow, heat could be either removed from a
junction to freeze water into ice, or by reversing the current,
heat can be generated to melt ice. The heat absorbed or
created at the junction is proportional to the electrical current.
The proportionality constant is known as the Peltier
coefficient.
If we modify our thermocouple circuit to obtain the
configuration shown in fig, it will be possible to observe an
opposite
it was an electrical current that is induced, which by Ampere's
law deflects the magnet. More specifically, the temperature
difference produces an electric potential (voltage) which can
drive an electric current in a closed circuit. Today, this is
known as the Seebeck effect.
The voltage produced is proportional to the
temperature difference between the two junctions. The
coefficient, and often referred to as the thermoelectric power
or thermopower. The Seebeck voltage does not depend on the
distribution of temperature along the metals between the
junctions. This is the physical basis for a thermocouple, which
is used often for temperature measurement.
Fig. 1 Peltier Effect
Fig. 2 Seebeck Effect
If a voltage (Vin) is applied to terminals Tl and T2 an
electrical current (I) will flow in the circuit. As a result of the
current flow, a slight cooling effect (Qc) will occur at
thermocouple junction A where heat is absorbed and a heating
effect (Qh) will occur at junction B where heat is expelled.
Note that this effect may be reversed whereby a change in the
direction of electric current flow will reverse the direction of
heat flow. The Peltier effect can be expressed mathematically
as:
Qc or Qh=pxy x I
Where: pxy is the differential Peltier coefficient between the
two materials, x and y, in volts I is the electric current flow in
amperes Qc, Qh is the rate of cooling and heating,
respectively, in watts Joule heating, having a magnitude of I x
R (where R is the electrical resistance), also occurs in the
conductors as a result of current flow. This Joule heating
effect acts in opposition to the Peltier effect and causes a net
reduction of the available cooling.
– Tc)
As shown in figure 2 the voltage difference, V,
produced across the terminals of an open circuit made from a
pair of dissimilar metals, A and B, whose two junctions are
held at different temperatures, is directly proportional to the
difference between the hot and cold junction temperatures,
Th - Tc. To illustrate the Seebeck Effect let us look at a simple
thermocouple circuit as shown in fig. The thermocouple
conductors are two dissimilar metals denoted as Material x
and Material y.
B. Seebeck Effect
In 1821 Thomas Johann Seebeck found that a circuit made
from two dissimilar metals, with junctions at different
temperatures would deflect a compass magnet. Seebeck
initially believed this was due to magnetism induced by the
temperature difference. However, it was quickly realized that
Fig. 3 Temperature Measurement of Thermocouples
In a typical temperature measurement application as shown in
figure 3, thermocouple A is used as a "reference" and is
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International Journal For Emerging Trends in Engineering and Management Research (IJETEMR) –Volume II
Issue 1- 21st January 2016
maintained at a relatively cool temperature of Tc.
Thermocouple B is used to measure the temperature of
interest (Th) which, in this example, is higher than
temperature Tc. With heat applied to thermocouple B, a
voltage will appear across terminals Tl and T2. This voltage
(Vo), known as the Seebeck emf, can be expressed as: Vo =
axy x (Th - Tc)
IV.
Construction
AC
B
L
O
W
E
R
FANS
HEAT
SINK
DUCT
TECs
Fig. 5 Implementation of Thermoelectric Cooling System
CLUSTER OF
COLD SIDE
HEAT SINK
TEC POWER
SUPPLY
Fig. 4 Basic Block Diagram of Thermoelectric Cooling
System
The thermoelectric cooling fan design was performed based
on certain mechanical and electrical calculations. The fan’s
design was compromised on the availability of parts in the
market and budget of the project. As shown in figure 4 the
prototype assembly starts with a main fan which is used to
blow the ambient air through a circular duct The duct is
attached to a blower fan and leads towards a group of four
heat sink. The air which is passed through the duct goes into
the cluster of four heat sinks which are united together. This
heat sinks act as a channel for the air to pass through, there are
six TECs that are sandwiched between a long black heat sink.
The TECs were installed between the heat sinks using thermal
grease, which increases the thermal conductivity by balancing
irregular surface of the heat sinks. When the TECs are in
operation cold side of the TEC cools down the heat sink
channel. Air which is coming out from the channel is chilled
air which is lower than the ambient. The cold side heat sinks
rests on wooden base. There are two fans fitted on top of the
hot side heat sink. They blow air towards the hot heat sink to
cool it down when the TECs are in operation. The hot air is
channeled away from the user using panels. The whole
assembly of the cold side heat sink, hot side heat sink, TECs
and the wooden base are fitted tightly with the help of metal
clips. These metal clips are tightened together with screws and
nuts. The whole assembly is enclosed with sheets or panels.
Assembly of TEC
The ambient air blown from the blower is channelled into
goes a group of four heat sinks which acts a rectangular duct
as discussed earlier. It was decided to remove maximum
amount heat from the point when the air started to enter the
first heat sink. Keeping that in mind the first heat sink was
installed with two TECs in series and the second one also was
installed with another two TECs in series. This will help to
remove more heat from of the air when air enters the duct.
The third and fourth heat sinks were installed with one TEC
each and they were connected in series also. All the two series
connected TECs were connected in parallel. Figure 6
illustrates a top view of the connection of TECs as explained
above. The arrow indicates direction of air flow.
D
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Fig. 6 Layout of the TECs
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International Journal For Emerging Trends in Engineering and Management Research (IJETEMR) –Volume II
Issue 1- 21st January 2016
Conclusion
Each of the TEC will be acting as loads. In other words the
layout above can also be termed as three parallel groups of
two TECs in series electrically. Figure 7 shows simpler
redrawn electrical connection of the TECs.
Fig. 7 Electrical connection of the TECs
Total required current and voltage for the all the joined TE
modules are 12A and 24V respectively. Therefore a 300W
power supply was enough for the cooling system. The
electrical power input was greater than cooling power of the
TECs and also higher than the calculated Qc.
( 300W  226W  222W ).
Thermoelectrics and thermoelectric cooling are being studied
exhaustively for the past several years and
various
conclusions have been conceived regarding the efficient
functioning of thermoelectric refrigerators.
Thermoelectric refrigerators are greatly needed,
particularly for developing countries, where long life, low
maintenance and clean environment are needed. In this aspect
thermoelectrics cannot be challenged in spite of the fact that it
has some disadvantages like low coefficient of performance
and high cost. These contentious issues are the frontal factors
hampering the large scale commercialization of thermoelectric
cooling devices.
The solution to above problems can only be resolved
with the development of new techniques. There is a lot of
scope for developing materials specefically suited for TE
cooling purpose and these can greatly improve the C.O.P. of
these devices. Development of new methods to improve
efficiency catering to changes in the basic design of the
thermoelectric set up like better heat transfer, miniaturization
etc. can give very effective enhancement in the overall
performance of thermoelectric refrigerators. Finally, there is a
general need for more studies that combine several
techniques, exploiting the best of each and using these
practically.
References
RESULT
Final testing of TECs for the completed assembly for about 30
mins. Temperature measured at different locations is shown in
table 1. Here we can see that as time increases, temperature at
outlet decreases. Within 30 minute temperature decreases
from 31.5 to 25.1.
Time
Temp
at cold
side
heat
sink 1
Temp
at cold
side
heat
sink 2
Temp
at cold
side
heat
sink 3
Temp
at cold
side
heat
sink 4
Temp
at hot
side
heat
sink
Outlet
temp
0
5
10
15
20
25
30
31.5
31.2
31.0
31.2
31.4
31.6
31.4
31.5
30.9
30.0
30.1
29.7
29.6
29.8
31.5
28.1
27.9
28.1
27.8
27.6
27.8
31.5
27.0
26.7
26.7
26.2
26.1
25.9
31.5
52.0
50.5
52.0
51.0
50.1
51
31.5
25.5
25.5
25.6
25.7
25.6
25.1
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Dallas, Texas.
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Dallas, Texas.
[8] Melcor 2010, Thermoelectric Handbook, Laird Technologies.
[9] Hyeung,SC, Sangkook, Y & Kwang-il, W 2007, Development of a
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[10] Bulat, L & Nekhoroshev, Y 2003, Thermoelectric cooling-heating unit
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international conference on thermoelectrics.
Table 1. Time vs Temperature
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