TED-AJ03-136 A CARBON FIBER, AIR-COOLED HEAT EXCHANGER FOR HIGH PERFORMANCE ELECTRONICS COOLING

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概要

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• Miniaturization, and the continued improvements in the speed and performance of electronics and other heat-dissipating systems, places and increasing demand on thermal management systems through the increase in power densities. There is a challenge to provide new thermal management technologies that will be able to handle the very large heat fluxes that arise from these improved electronics. Among the candidates for technologies that possess a large heat transfer rate per unit of heat-dissipating surface area is the Brush Heat Exchanger (BHX). The BHX consists of a very large number of air-cooled, small-cross-section, staggered fins of carbon-pitch fiber / epoxy matrix construction packed in a rectangular enclosure. Five BHX units were designed, built, and tested in this effort. As we see in Fig. 1,the peak heat flux for the unit having the best thermal performance (BHX 5) approaches 19 W/(cm)^2 (for a maximum allowable difference of 80 C between the mean base temperature and the inlet air) for an air flow rate of 0.021 m^3/s (45 cfm). The associated thermal resistance for this BHX unit ranges from less than 0.10 K/W to about 0.08 K/W; more than a factor of five better than the average commercial air-cooled heat exchanger, a factor of two better than the best available commercial unit, and a factor of nearly four times better than that of the commercial, aluminum, finned heat sink tested in this work. The peak pressure drop is about 11.3 kPa (1.6 psi) for an air flow rate of of 0.021 m^3/s. Peak inlet air speeds are about 10 m/s. Very little acoustic noise was perceived and no carbon particles from the fiber reinforced composite portions of the BHX were detected in a downstream air filter, even after twelve hours of testing for five different exchanger designs. Results are extremely promising; nevertheless, several key areas have been identified for further improvements including improved manufacturability, and a few design changes.[figure] The design changes would include increasing the number of fins by reducing the fin thickness in the direction of air flow. This effect will increase the heat transfer coefficient between the fins and the air by reducing the mean thermal boundary layer thickness on the fins and increase the flexibility of the fins. The more-flexible fins will oscillate slightly as the air passes over them and cause intermittent break and re-establishment of the thermal and velocity boundary layers at the fiber surfaces. In the limit as the fins approach striking each other, this effect mimics that of a fluidized bed which is known to possess very large heat transfer coefficients.

• 一般社団法人日本機械学会の論文

著者

• Sullivan B.

  Materials Research & Design Inc.

• Jones G.

  Department Of Mechanical Engineering Villanova University

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• TED-AJ03-136 A CARBON FIBER, AIR-COOLED HEAT EXCHANGER FOR HIGH PERFORMANCE ELECTRONICS COOLING

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