Optimal Design of a Thermoelectric Cooling/Heating System ...
THERMOELECTRIC COOLING
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Transcript of THERMOELECTRIC COOLING
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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