Experimental Investigation of Compact Evaporators for Ultra Low Temperature Refrigeration of Microprocessors

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1853/7198

Title: Experimental Investigation of Compact Evaporators for Ultra Low Temperature Refrigeration of Microprocessors
Author: Wadell, Robert Paul
Abstract: It is well known that microprocessor performance can be improved by lowering the junction temperature. Two stage cascaded vapor compression refrigeration (VCR) is a mature, inexpensive, and reliable cooling technology that can offer chip temperatures down to ?? C. Recent studies have shown that for a power limited computer chip, there is a non-linear scaling effect that offers a 4.3X performance enhancement at ?? C. The heat transfer performance of a compact evaporator is often the bottleneck in sub-ambient heat removal. For this reason, the design of a deep sub-ambient compact evaporator is critical to the cooling system performance and has not been addressed in the literature. Four compact evaporator designs were investigated as feasible designs - a baseline case with no enhancement structures, micro channels, inline pin fin arrays, and alternating pin fin arrays. A parametric experimental investigation of four compact evaporator designs has been performed aiming at enhancing heat transfer. Each evaporator consists of oxygen free copper and has a footprint of 20 mm x 36 mm, with a total thickness of 3.1 mm. The micro channel evaporator contains 13 channels that are 400 um wide by 1.2 mm deep, and the pin fin evaporators contain approximately 80 pin fins that are 400 um wide by 1.2 mm tall with a pitch of 800 um. Two phase convective boiling of R508b refrigerant was investigated in each evaporator at flow rates of 50 - 70 g/min and saturation temperatures of ??to ??C. Pressure drop and local heat transfer measurements are reported and used to explain the performance of the various evaporator geometries. The results are compared to predictions from popular macro- and micro-channel heat transfer and pressure drop correlations. The challenges of implementing a two stage cascade VCR systems for microprocessor refrigeration are also discussed.
Type: Thesis
URI: http://hdl.handle.net/1853/7198
Date: 2005-07-18
Publisher: Georgia Institute of Technology
Subject: Microprocessor
Thermal management
Vapor compression refrigeration
Compact evaporator
Flow boiling
Electronic apparatus and appliances Thermal properties
Evaporative cooling
Department: Mechanical Engineering
Advisor: Committee Chair: Yogendra Joshi; Committee Co-Chair: Andrei Fedorov; Committee Member: Paul Kohl
Degree: M.S.

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