Abstract
Due to the current downsizing trend and improvement of cycle efficiency, the demand for the restriction in low flow rate becomes to be expected. In order to enhance the heat transfer in this region, an assessment of the tube geometry has been conducted for an effectiveness of saliences on inner surface. This salience promotes the starting of turbulence and encouragement of heat transfer under the laminar flow region. In the present paper, experimental measurement of convectional heat transfer of tube, where Re = 420 - 1670, has been carried out for 6 different saliences and two channel heights. The effect was evaluated with mean heat transfer coefficient overall obtained by transient measurement with thermos-couples. As a result, case D, which has 4 rows and symmetric small salience, and whose channel height is 0.9mm showed best performance. Furthermore, for case D, Numerical simulation is executed and continuous turbulence structure is seen.
