Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing in a Vertical Small Diameter Tube

摘要

In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing in a vertical copper smooth tube with 1.0 mm inside diameter. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m~2·s), heat fluxes from 1 to 16 kW/m~2 and qualities from 0 to 1 at evaporation temperature of 10℃. Pressure drops were also measured at mass fluxes of 100 and 200 kg/(m~2·s) for upward flow and of 30, 50, 100 and 200 kg/(m~2·s) for downward flow and qualities from 0.1 to 0.9. Three types of flow pattern were observed in the tube: A slug, a slug-annular and an annular flow. Based on the measurements, the characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified.