Abstract
It is requested to develop a small and high performance heat exchanger for small size energy equipments such as fuel cells and CO_2 heat pumps, and so on. In author's previous studies, a high pressure resistant microchannel layers stacked heat exchanger has been developed. The device is manufactured by diffusion bond technique. It can be used under high pressure condition larger than 15MPa. Due to the high pressure resistance, the heat exchanger can be applied for high flow rate condition with boiling and condensation. The objectives of the present study are to estimate the heat transfer performance of the heat exchanger and to investigate the thermal hydraulic behavior in the microchannel. The flow pattern is observed by fabricating visualization system for one channel to observe the flow condensation behavior in microchannel. In the experiment, the microchannel of Pyrex glass is surrounded by the subcooling water. The flow patterns can visualized from the side of the microchannel. Flow patterns observations are conducted for various diameters of the maicrochannel, flow rates and temperatures of the subclooled water. It is observed that the continuous flow transition from annular and injection flow to slug-bubble flow in the microchannel.
