Boiling Heat Transfer and Pressure Drop Characteristics of R245fa in Microchannel
Experimental study on the boiling heat transfer and pressure drop characteristics of R245fa in a horizontal copper tube with a microchannel inner diameter of 1.83 mm and a heat-ing length of 170 mm.The effects of heat flux,mass flux,and inlet subcooling on boiling heat transfer at T5(axial position z=130 mm along the heating length of the test section)and total pres-sure drop were analyzed.Experimental parameters included heat fluxes of 40 and 50 kW·m-2,mass fluxes of 530,830 and 1130 kg·m-2·s-1,inlet subcoolings of 10 and 15 K,and saturation pressure of 177.79 kPa.The results show that the single-phase flow,subcooled boiling,and saturated boiling appear successively in the tube as heat flux increased step by step in process of boiling flow.Specif-ically,the heat transfer mechanism of subcooled boiling and saturated boiling stages is nucleate boiling.The heat transfer coefficient increases with the increase of heat flux,and the mass flux determines the heat flux at which saturated boiling begins.The effects of heat flux,mass flux,and inlet subcooling on single-phase flow heat transfer and two-phase flow heat transfer are different,and the impact on pressure drop is mainly determined by the magnitude of frictional pressure drop and accelerational pressure drop inside the tube.
microchannelR245faboiling heat transferpressure drop
NETL
NSTL
万方数据
