Flow boiling of R245fa in the brazed plate heat exchanger: Thermal and hydraulic performance assessment

摘要

Present study deals with the flow boiling of R245fa, a commercial working fluid used in organic Rankine cycle, in brazed plate heat exchanger with chevron angle of 45 degree and 60 degree. The effects of the heat flux, mass flux rate of refrigerant, saturation temperature on convective heat transfer coefficients are investigated. The operating conditions of the experiment are as mass flux: 30-40 kg m~(-2) s~(-1) quality at evaporator inlet: 0.1-0.8, heat flux: 2-15 kW nrr~(-2). The heat transfer result suggests a nucleate boiling dominant process in the evaporator. The convective heat transfer coefficient showed a strong dependence on the heat flux and vapor quality at evaporator inlet. Moreover convective heat transfer coefficient show a linear relationship with mass flux of the refrigerant. It is worth mentioning that heat transfer coefficient is higher at higher saturation temperature and chevron angle. Based on the experimental data, empirical correlations were developed for the prediction of heat transfer coefficients and frictional pressure drop of refrigerant R245fa in brazed plate heat exchanger.