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The Peltier Effect

The Peltier Effect. Jacob McKenzie, Ty Nowotny, Colin Neunuebel SRJC Engr45 - Fall 2005. History of the Seebeck effect. Discovered by Thomas Johann Seebeck in 1821. He accidentally found that a voltage existed between two ends of a metal bar when a temperature gradient existed within the bar.

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The Peltier Effect

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  1. The Peltier Effect • Jacob McKenzie, Ty Nowotny, Colin Neunuebel • SRJC Engr45 - Fall 2005

  2. History of the Seebeck effect • Discovered by Thomas Johann Seebeck in 1821. • He accidentally found that a voltage existed between two ends of a metal bar when a temperature gradient existed within the bar.

  3. The Seebeck Effect • A temperature difference causes diffusion of electrons from the hot side to the cold side of a conductor. • The motion of electrons creates an electrical current. • The voltage is proportional to the temperature difference as governed by: V=α(Th-Tc) where α is the Seebeck coefficient of the couple

  4. History of Peltier devices • The Peltier effect is named after Jean Charles Peltier (1785-1845) who first observed it in 1834. • The Peltier effect had no practical use for over 100 years until dissimilar metal devices were replaced with semiconductor Peltiers which could produce much larger thermal gradients.

  5. What is a Peltier Cooler? • Thermoelectric heat pumps that will produce a temperature gradient that is proportional to an applied current.

  6. Peltier Effect With Dissimilar Metals • At the junction of two dissimilar metals the energy level of conducting electrons is forced to increase or decrease. • A decrease in the energy level emits thermal energy, while an increase will absorb thermal energy from its surroundings. • The temperature gradient for dissimilar metals is very small. The figure of merit is a measure of thermoelectric efficiency.

  7. Semiconductor Peltier • Bismuth-Telluride n and p blocks • An electric current forces electrons in n type and holes in p type away from each other on the cold side and towards each other on the hot side. • The holes and electrons pull thermal energy from where they are heading away from each other and deliver it to where they meet.

  8. Device Construction • Individual couples are connected in series electrically and in parallel thermally. • Couples are thermally connected by a ceramic that has high electrical resistivity and high thermal conductivity.

  9. Our Peltier:Change in Temperature @ 12v

  10. our peltier:Temperature Gradient Carnot Efficiency Nc @ 12v: =1-Tc/Th =1-283.6/342.3 =17.1%

  11. Applications • Deep space probes • Microprocessor cooling • Laser diode temperature stabilization • Temperature regulated flight suits • Air conditioning in submarines • Portable DC refrigerators • Automotive seat cooling/heating Radioisotopic Thermoelectric Generator (RTG)

  12. Pros and Cons • Pros • Solid state (no moving parts) • No maintenance • Long service lifetime • Cons • Large electrical power requirements • Inefficient compared to phase change cooling

  13. References • http://www.its.caltech.edu/~jsnyder/thermoelectrics/history_page.htm • http://www.tellurex.com/12most.html • http://www.thermoelectrics.com/introduction.htm, Thermoelectric Materials • http://www.digit-life.com/articles/peltiercoolers/ • http://www.heatsink-guide.com/content.php?content=peltierinfo.shtml, THE HEATSINK GUIDE: Peltier Guide, Part 1 • http://saturn.jpl.nasa.gov/index.cfm

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