Experiment on condensation heat transfer of HFC134a in a horizontal single rectangular mini-channel

Herein, a measuring device was constructed to obtain condensation heat transfer characteristics at mass flow rates below 100 kg/(m²·s) for a 1 × 1 mm² flow path constituting a flat multiport heat transfer tube. The condensation heat transfer characteristics of HFC134a were experimentally determined under flow rate conditions including low mass rate of 40 kg/(m²·s). The condensation heat transfer coefficient in a single tube was partly different from that observed in a flat multiport tube. Also, we found that the smaller the flow rate (or the smaller the heat flow rate), the higher the heat transfer coefficient becomes. In the low quality range, as the vapor quality decreased, the smaller the flow rate, the higher the maximum value with high quality. This feature was remarkable when the heat flux was small. Regarding the tendency of the single tube to reach the local maximum value of the heat transfer coefficient in the low quality range, the region where the slug flow occurs corresponds well to the quality region where the condensation heat transfer shows a local maximum, with reference to what has been observed in previous studies.