Convection heat transfer research of supercritical R134a in mini-channel of tube
The supercritical organic Rankine cycle(SORC)is an ideal new power cycle technology for recovering energy using supercritical organic Rankine cycle.The energy efficiency of the system is significantly affected by the SORC,the supercritical organic working medium,low grade energy recovery,and the heat transfer characteristics of the supercritical organic working medium.At present,it has become a bottleneck that restrict the development of organic Rankine cycle technology.To address this issue,the experimental studies were conducted on the flow heat transfer characteristics of supercritical R134a in a tiny channel with an inner diameter of 2mm).The parameters considered in the study were as follows:heat flux ranging from 60-120kW/(m2·s),mass flow rate from 800-3000kg/(m2·s),pressure from 4.1-5.1MPa,and working medium inlet temperature from 20-100℃.The effects of heat flow density,mass flow velocity,pressure and fluid temperature on the heat transfer characteristics were discussed.The results showed that the heat transfer coefficient initially increased and then decreased with the increase of fluid temperature.It also increased with the increase of mass flow rate but decreased with the increase of heat flux and pressure.According to the experimental data,a prediction accuracy of±10％for R134a in the microchannel was achieved,demonstrating good prediction accuracy.
micro-channelsupercritical R134afluid flow and heat transferorganic Rankine cycleheat transfer correlation
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