Geometric Effects on the Transient Cooling of Thermoelectric Coolers
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Geometric Effects on the Transient Cooling of Thermoelectric Coolers Ronggui Yang1, Gang Chen1, G. Jeffrey Snyder2 and Jean-Pierre Fleuriel2 1
Mechanical Engineering Department, Massachusetts Institute of Technology, Cambridge, MA 02139 2 Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 277-207, Pasadena, CA 91109 ABSTRACT Transient thermoelectric cooling effect has been known since 1960s. Most of the previous studies focus on the minimum temperature achievable for free standing thermoelectric elements. Practical thermoelectric coolers have a passive mass load, which affect the minimum temperature achievable. This is particularly true for thermoelectric micro coolers because the object to be cooled is comparable to the micro coolers in size. In this paper, we present the performance analysis of the integrated system made of the cooling object and thermoelectric element, and establish the criterion for the utilization of transient cooling effect based on the analysis of the time constants. Effects of thermoelectric element shape on the transient thermoelectric cooling effect are also studied. Key Words: Transient Cooling, Thermoelectric, Thermal Management 1. Introduction After Stilbans and Fedorovich [1] first reported the transient cooling effect in thermoelectric (TE) elements, the phenomenon has been extensively investigated [2-8] and some ideas have been explored to obtain larger transient cooling temperature difference, which is measured by the additional temperature drop at the cold junction caused by the transient current that is several times as large as steady state optimum current, such as applying non-square transient current [3], using TE elements with variable cross-sectional area [9] and surface junction [10]. Recent developments in the fabrication of thermoelectric microcoolers make it possible to place the TE coolers near the high heat flux producing regions of electronic or optoelectronic devices that need to be cooled [11-14]. This will enable a compact and more effective design of thermal system for device and package level cooling. The transient cooling effect in thermoelectric coolers might be employed to further improve the performance of these devices. Results of previous mentioned studies are not directly applicable to the microcoolers because those studies are extensively for free standing thermoelectric elements and most of them only focused on the maximum transient temperature difference, i.e., the minimum temperature achievable. Several issues that are particular for micro devices need to be addressed. First of all, the object to be cooled is a passive mass load for the thermoelectric coolers and it will affect the minimum temperature achievable because the object to be cooled is comparable to the micro coolers in size. Furthermore, several time constants are very important for the characterization and the utilization of the transient cooling effect since the transient cooling effect can only be sustained for limited time. In this paper, we present t
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