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Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University

ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Peltier Heat Pump. Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University E: magicarrow2@live.com; F: (435)797-3054 (ECE Dept.). 3/9/2012. Outline. Reference list

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Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University

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  1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Peltier Heat Pump Prepared by: Jared Schmidt Dept. of Electrical and Computer Engineering Utah State University E: magicarrow2@live.com; F: (435)797-3054 (ECE Dept.) 3/9/2012

  2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations • Purchasing information ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  3. Reference list • “Thermoelectric cooling”; Wikipedia.org; en.wikipedia.org/wiki/Thermoelectric_cooling • “Thermoelectric effect”; Wikipedia.org; en.wikipedia.org/wiki/Thermoelectric_effect •  Duckworth, Henry E.; Electricity and Magnetism; pp. 181-182; New York: Holt, Rinehart and Winston (1960) • “Peltier effect”; The Encyclopedia of Science; www.daviddarling.info/encyclopedia/P/Peltier_effect.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  4. To explore further (survival pointers of web references etc) • “Thermoelectric Devices: Solid-State Refrigerators and Electrical Generators in the Classroom”; Edmund J. Winder, Arthur B. Ellis, and George C. Lisensky; Journal of Chemical Education; 1996; 73 (10), 940 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  5. Major applications • Instrument cooling • CPU cooling • Beverage cooling/heating • Refrigeration • Fiber optic laser cooling • Thermistor cooling Thermoelectric USB beverage cooler Photo from Wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  6. Major applications • In general thermoelectric cooling is used for: • Cooling in limited spaces • Cooling small devices • Cooling in devices requiring quiet or silent operation Peltier Heat Pump Photo from Wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  7. Major applications • Since Peltier heat pumps create a temperature difference and not an absolute temperature, they are sometimes stacked serially to get larger temperature differences between the ends of the stack. Three stage Peltier cooler from www.Ferrotec.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  8. Basic Working Principle • “The Peltier effect is the presence of heat at an electrified junction of two different metals” (Wikipedia) Example From Duckworth, Electricity & Magnetism, p 181 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  9. Basic Working Principle • The Peltier effect is related to the Seebeck effect and the Thompson effect. • Seebeck effect says that a temperature difference between dissimilar junctions will create a voltage difference. • Thompson effect says a current carrying conductor with a temperature difference on it between two points will absorb or expel heat. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  10. Basic Working Principle • The conduction occurs in the levels of the highest energy electrons the atom has. For different elements, this energy level is slightly different. • When electrons are forced to move through the junction of two dissimilar metals, the electrons have to overcome an energy level difference to move through junction. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  11. Basic Working Principle • An electron going from a lower energy level to a higher energy level (across a junction) needs a boost of energy. • In order to do this, the electron borrows energy from its surroundings, which removes heat from the junction. This is why the cold junction gets cold. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  12. Basic Working Principle • An electron going a higher energy level to a lower energy level (across a junction) expels some energy. • In order to do this, the electron sheds some energy into its surroundings, which generates heat in the junction. Thus the hot junction gets hot. • By reversing the current, the electrons go the opposite direction which switches which junction is hot and which junction is cold. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  13. Basic Working Principle • Often, semiconductors that have been doped with impurities are used to make solid state heater/coolers. • Doped semiconductors work as well as or better than dissimilar metals at generating a temperature difference between junctions. • Semiconductors don’t conduct heat as well as metals. • This allows solid state heat pumps to be made smaller. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  14. Common Heat Pump Construction Semiconductor Heat Pump “Peltier element schematic. Thermoelectric legs are thermally in parallel and electrically in series.” Courtesy of Wikipedia.org ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  15. Sample Configuration • The picture to the right shows a heat sink attached to the hot side of two Peltier heat pumps. • The cold plate can be mounted to: • a chip • a circuit board • another heat sink • anything that needs to be cooled Peltier cooler assembly from http://sctbnord.com/article_124.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  16. Major Specifications • Max voltage • Max current draw • Temperature difference between hot and cold sides • Size • Max heat flux (speed of heat absorption/rejection) • Price ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  17. Example Specifications • Max voltage: 3.8V • Max current draw: 6A • Max temperature difference between hot and cold sides: 68°C @ 27°C • Size: 20mm x 20mm x 4mm • Max heat flux: 13W @ 27°C • Cost: $14.57 From www.digikey.com Part Number: 102-1676-ND Description: Peltier Mod 20x 4mm 6.0A INP ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  18. Limitations • Very low efficiency • 10% of Carnot efficiency or less • Heat pump cannot often be a stand-alone device • Saturation can occur quickly when heat starts moving from the hot junction to the cold junction. • Hot side must be coupled with a heat sink or some other method of heat removal. • Overheating of the heat pump can occur quickly if heat is not removed from the hot side. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  19. Considerations • When using Peltier heat pumps to cool electronics, condensation is a concern. • The temperature of the cold side is usually below ambient room temperature and can result in condensation on the electronics, which may damage them. Photo from www.dansdata.com Photo from www.penguinslab.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  20. Purchasing Information • Many companies sell Peltier heat pumps. • A few examples are: ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

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