Abstract
To utilize the exhausted heat produced from a methanol reformer (a part of a reformed methanol fuel cell) effectively, the development of a highly effective microchannel heat exchanger (MCHE) is of critical importance. This design could not only reduce the temperature of the hydrogen released from a reformer but also transfer the heat to the liquid methanol. Following our previous researches on the co- and counter-flow MCHEs, the two-phase flow boiling heat transfer characteristics in a cross-flow MCHE is investigated in the present work. The MCHE is made from 4-inches silicon wafer prepared through microfabrication processes with a dimension of 20 mm × 20 mm. Eighteen microchannels are etched on each side, and covered with Pyrex 7740 glass by anodic bonding. The channel depth on both cold- and hot-side is 200 μm, and the thickness of the wall between is the same of 200μm. To make the boiling flow more stable, the microchannels in the cold side employ a diverging design, as suggested in our previous studies. Liquid methanol is used as the boiling fluid, while hot helium gas is employed to simulate hydrogen. From the experiment results, it indicates that in the efficiency with methanol boiling in the cold side gradually increases with an increase in hot-side thermal power. Moreover, the efficiency increases significantly with an increase in the mass flux. The highest efficiency could achieve about 0.91 and the transferred cooling power is around 50 kWm-2.