THERMOELECTRIC COOLINGTHERMOELECTRIC COOLING

1.1. INTRODUCTIONINTRODUCTION

2.2. BASIC PRICIPLES OF THERMOELECTRIC BASIC PRICIPLES OF THERMOELECTRIC

MODULES MODULES

3.3. BASIC MECHANISM OF THERMOELECTRIC COOLINGBASIC MECHANISM OF THERMOELECTRIC COOLING

4.4. THERMOELECTRIC COOLING MODULESTHERMOELECTRIC COOLING MODULES

5.5. HEAT SINK CONSIDERATIONSHEAT SINK CONSIDERATIONS

6.6. PERFORMANCE GRAPH OF THERMOELECTRIC MODULEPERFORMANCE GRAPH OF THERMOELECTRIC MODULE

7.7. APPLICATIONS OF THERMOELECTRIC COOLERSAPPLICATIONS OF THERMOELECTRIC COOLERS

8.8. ADVANTAGES OF THERMOELECTRIC COOLINGADVANTAGES OF THERMOELECTRIC COOLING

9.9. THERMOELECTRIC COOLING VERSUS TRADITIONAL THERMOELECTRIC COOLING VERSUS TRADITIONAL

REFRIGERATIONREFRIGERATION

CONTENTS

1. INTRODUCTION1. INTRODUCTION

A thermoelectric (TE) cooler, sometimes called a

thermoelectric module or Peltier cooler, is a

semiconductor-based electronic component that

functions as a small heat pump. By applying a low

voltage DC power source to a TE 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.

2. BASIC PRICIPLES OF THERMOELECTRIC 2. BASIC PRICIPLES OF THERMOELECTRIC MODULESMODULES

THERMOELECTRICITY IS BSED UPON THREE THERMOELECTRICITY IS BSED UPON THREE

BSIC PRINCIPLESBSIC PRINCIPLES

1.1. SEEBECK EFFECTSEEBECK EFFECT

2.2. PELTIER EFFECTPELTIER EFFECT

3.3. THOMSON EFFECTTHOMSON EFFECT

SEEBECK EFFECTSEEBECK EFFECT

VO = AXY * (TH - TC)VO = AXY * (TH - TC)

Where: Where:

VO :- VO :- is the output voltage in volts. is the output voltage in volts.

AXY :- AXY :- is the differential Seebeck coefficient between the is the differential Seebeck coefficient between the

two materials, x and y, in volts/K .two materials, x and y, in volts/K .

TH TH and and TC,TC, are the hot and cold thermocouple temperatures, respectively are the hot and cold thermocouple temperatures, respectively

PELTIER EFFECTPELTIER EFFECT

QQCC or Q or QHH =P =PXYXY * I * I Where: Where: PPXYXY is the differential Peltier coefficient between the two is the differential Peltier coefficient between the two

materials, x and y, in volts .materials, x and y, in volts .I I is the electric current flow in is the electric current flow in amperesamperes. Q. QCC, , QQHH is the rate of cooling and heating, is the rate of cooling and heating, respectively, in watts.respectively, in watts.

THOMSON EFFECTTHOMSON EFFECT

When an electric current is passed through a When an electric current is passed through a

conductor having a temperature gradient over its conductor having a temperature gradient over its

length, heat will be either absorbed by or expelled length, heat will be either absorbed by or expelled

from the conductor. Whether heat is absorbed or from the conductor. Whether heat is absorbed or

expelled depends upon the direction of both the expelled depends upon the direction of both the

electric current and temperature gradient. This electric current and temperature gradient. This

phenomenon is known as the Thomson Effect phenomenon is known as the Thomson Effect

3. BASIC MECHANISM OF 3. BASIC MECHANISM OF THERMOELECTRIC THERMOELECTRIC

N-TYPE SINGLE SEMICONDUCTOR N-TYPE SINGLE SEMICONDUCTOR PELLETPELLET

P-TYPE SINGLE SEMICONDUCTOR P-TYPE SINGLE SEMICONDUCTOR PELLETPELLET

ELECTRICALLY AND THERMALLY ELECTRICALLY AND THERMALLY PARALLEL MULTIPLE PELLETSPARALLEL MULTIPLE PELLETS

THERMALLY PARALLEL AND ELECTRICALLT THERMALLY PARALLEL AND ELECTRICALLT IN SERIES MULTIPLE PELLETSIN SERIES MULTIPLE PELLETS

N AND P-TYPE PELLETSN AND P-TYPE PELLETS

N AND P-TYPE MULTIPLE PELLETSN AND P-TYPE MULTIPLE PELLETS

THERMOELECTRIC MATERIALSTHERMOELECTRIC MATERIALS The most often used in today's TE coolers is an alloy of Bismuth The most often used in today's TE coolers is an alloy of Bismuth

Telluride (BiTelluride (Bi22TeTe33).). In addition to Bismuth Telluride (BiIn addition to Bismuth Telluride (Bi22TeTe33), there are other ), there are other

thermoelectric materials including Lead Telluride (Pb-Te), Silicon thermoelectric materials including Lead Telluride (Pb-Te), Silicon Germanium (Si-Ge) and Bismuth-Antimony (Bi-Sb) alloys that Germanium (Si-Ge) and Bismuth-Antimony (Bi-Sb) alloys that may be used in specific situations.may be used in specific situations.

Thermoelectric Materials should posses:-Thermoelectric Materials should posses:- Large Seebeck Coefficients (to minimize Joule heating).Large Seebeck Coefficients (to minimize Joule heating). High Electrical Conductivity.High Electrical Conductivity. Low Thermal Conductivity (to retain heat at the junctions)Low Thermal Conductivity (to retain heat at the junctions)

APPROXIMATE FIGURE-OF-MERIT(Z)FOR APPROXIMATE FIGURE-OF-MERIT(Z)FOR

VARIOUS TE MATERIALSVARIOUS TE MATERIALS

4. THERMOELECTRIC COOLING 4. THERMOELECTRIC COOLING

MODULESMODULES

thermoelectric modules ranging in size from thermoelectric modules ranging in size from approximately 2.5-50 mm (0.1 to 2.0 inches) square and approximately 2.5-50 mm (0.1 to 2.0 inches) square and 2.5-5mm (0.1 to 0.2 inches) in height. 2.5-5mm (0.1 to 0.2 inches) in height.

5. Heat Sink Considerations 5. Heat Sink Considerations

A perfect heat sink would be capable of absorbing an unlimited quantity of A perfect heat sink would be capable of absorbing an unlimited quantity of heat without exhibiting any increase in temperature. heat without exhibiting any increase in temperature.

A heat sink temperature rise of 5 to 15°C above ambient (or cooling fluid) A heat sink temperature rise of 5 to 15°C above ambient (or cooling fluid) is typical for many thermoelectric applications.is typical for many thermoelectric applications.

Heat sink performance:- Heat sink performance:- Qs= (Ts-Ta)/QQs= (Ts-Ta)/Q

Where Where

Qs:- Qs:- Thermal Resistance in Degrees centigrade per Watt. Thermal Resistance in Degrees centigrade per Watt. Ts:- Ts:- Heat Heat Sink Temperature in Degrees Centigrade.Sink Temperature in Degrees Centigrade.Ta:- Ta:- Ambient or Coolant Temperature in Degrees Centigrade. Ambient or Coolant Temperature in Degrees Centigrade. Q :- Q :- Heat Input to Heat Sink in Watts.Heat Input to Heat Sink in Watts.

TYPES OF HEAT SINKSTYPES OF HEAT SINKS

NATURAL CONVECTION HEAT SINKSNATURAL CONVECTION HEAT SINKS FORCED CONVECTION HEAT SINKSFORCED CONVECTION HEAT SINKS LIQUID-COOLED HEAT SINKSLIQUID-COOLED HEAT SINKS

Forced Convection Heat Sink System Forced Convection Heat Sink System Showing Preferred Air Flow Showing Preferred Air Flow

6. PERFORMANCE GRAPH OF TE MODULE6. PERFORMANCE GRAPH OF TE MODULE

 

 

7. APPLICATIONS OF 7. APPLICATIONS OF THERMOELECTRIC COOLERSTHERMOELECTRIC COOLERS

Include equipment used by military, medical, industrial, Include equipment used by military, medical, industrial,

consumer, scientific/laboratory, and telecommunications consumer, scientific/laboratory, and telecommunications

organizations. organizations.

Uses range from simple food and beverage coolers for an Uses range from simple food and beverage coolers for an

afternoon picnic to extremely sophisticated temperature afternoon picnic to extremely sophisticated temperature

control systems in missiles and space vehicles.control systems in missiles and space vehicles.

No Moving PartsNo Moving Parts Small Size and WeightSmall Size and Weight Ability to Cool Below AmbientAbility to Cool Below Ambient Ability to Heat and Cool With the Same moduleAbility to Heat and Cool With the Same module Precise Temperature ControlPrecise Temperature Control High ReliabilityHigh Reliability Electrically "Quiet" OperationElectrically "Quiet" Operation Operation in any OrientationOperation in any Orientation Spot CoolingSpot Cooling Ability to Generate Electrical PowerAbility to Generate Electrical Power Environmentally FriendlyEnvironmentally Friendly

8. ADVANTAGES OF THERMOELECTRIC 8. ADVANTAGES OF THERMOELECTRIC COOLING COOLING

Limitations of Thermoelectric Cooling Limitations of Thermoelectric Cooling DevicesDevices

Low C.O.P. and efficiencies make them Low C.O.P. and efficiencies make them unsuitable in places where economy is unsuitable in places where economy is concerned.concerned.

There is also a limitation of their use in larger There is also a limitation of their use in larger units.units.

9. THERMOELECTRIC COOLING VERSUS 9. THERMOELECTRIC COOLING VERSUS TRADITIONAL REFRIGERATION TRADITIONAL REFRIGERATION

Solid state design Solid state design No moving parts No moving parts Integrated chip design Integrated chip design No hazardous gases No hazardous gases Silent operation Silent operation

Compact and lightweightCompact and lightweight Low profile Low profile Sizes to match your component footprint Sizes to match your component footprint No bulky compressor unitsNo bulky compressor units

Precise temperature stabilityPrecise temperature stability Tolerances of better than +/- 0.1°C Tolerances of better than +/- 0.1°C Accurate and reproducible ramp and dwell times Accurate and reproducible ramp and dwell times

Cooling/heating mode optionsCooling/heating mode options Fully reversible with switch in polarity Fully reversible with switch in polarity

Localized CoolingLocalized Cooling Spot cooling for components or medical applications Spot cooling for components or medical applications Perfect for temperature calibration in precision detection systems Perfect for temperature calibration in precision detection systems

Rapid response timesRapid response times Instantaneous temperature change Instantaneous temperature change Reduced power consumption Reduced power consumption

DehumidificationDehumidification Efficient condensation of atmospheric water vapor Efficient condensation of atmospheric water vapor

CONCLUSIONCONCLUSION In spite of the fact that it has some disadvantages like low coefficient of performance and In spite of the fact that it has some disadvantages like low coefficient of performance and

high cost, thermoelectric refrigerators are greatly needed, particularly for developing high cost, thermoelectric refrigerators are greatly needed, particularly for developing

countries where long life, low maintenance and clean environment are needed. There is a lot countries where long life, low maintenance and clean environment are needed. There is a lot

of scope for developing materials specifically suited for TE cooling purpose and these can of scope for developing materials specifically suited for TE cooling purpose and these can

greatly improve the C.O.P. of these devices. Development of new methods to improve 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 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 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 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. several techniques, exploiting the best of each and using these practically. 

  

  

  

REFRENCESREFRENCES

http://www.thermoelectrics.com/introduction.htm

http://www.educypedia.be/electronics/thermoelectric.htm

http://www.peltier-info.com/info.html http://www.tellurex.com/12most.html http://www.ferrotec.com/technology/thermoele

ctric/thermalRef01.php

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