Thermal-hydraulic performance of small scale micro-channel and porous-media heat-exchangers

Fluid flow and forced convection heat transfer in micro-heat-exchangers with either micro-channels or porous media have been investigated experimentally. The influence of the dimensions of the micro-channels on the heat transfer performance was first analyzed numerically. Based on these computations. deep micro-channels were used for the experimental studies reported here. The measured performance of both micro-channel and porous-media micro-heat-exchangers are compared with those of similar heat-exchangers tested by other researchers. It is shown that the heat transfer performance of the micro-heat-exchanger using porous media is better than that of the micro-heat-exchanger using micro-channels, but the pressure drop of the former is much larger. Over the range of test conditions, the maximum volumetric heat transfer coefficient of the micro-heat-exchanger using porous media was 86.3 MW/(m(3) K) for a water mass flow rate of 0.067 kg/s and a pressure drop of 4.66 bar. The maximum volumetric heat transfer coefficient of the micro-heat-exchanger using deep micro-channels was 38.4 MW/(m(3) K) with a corresponding mass flow: rate of 0.34 kg/s and a pressure drop of 0.7 bar. Considering both the heat transfer and pressure drop characteristics of these heat-exchangers, the deep micro-channel design offers a better overall performance than either the porous media or shallow micro-channel alternatives. (C) 2001 Elsevier Science Ltd. All rights reserved.