An Investigation of Heat Transfer on Microchannel Heat Exchanger Flow Arrangement with Gas Heating

The present study investigates the effect of flow arrangement on heat transfer characteristics in two-phase microchannel heat exchangers (MCHEs) with gas heating. The microchannel heat exchangers are developed to utilize the exhaust heat from a high-temperature gas product of a methanol reformer (a part of a reformed methanol fuel cell). Co- and counter-current flow types of MCHE are tested. Working fluids in the hot and cold sides are helium and liquid methanol, respectively. For both single-phase flow regions, the experimental results indicate that the actual effectiveness of the counter-current MCHE is higher than that of the co-current MCHE. Both of the actual effectiveness of co- and counter-current MCHEs significantly increases with an increase of cold side mass flux. Moreover, the actual effectiveness for both types of MCHE is less relationship to the hot-side thermal power in single-phase zone. The highest actual effectiveness is about 0.6 and 0.72 for co- and counter-current MCHEs, respectively.