Experimental Study And Numerical Simulation Of Flow Condensation Characteristics Of R134a In A Dynamic Heat Pipe

The pump-assisted heat pipe is a energy transport system of low energy consumption and high density,which can transmit energy at a long distance and have a bright future in the application of energy-efficient.In order to solve the problem that the flow condensation heat transfer process in the pump-assisted heat pipe is complex and unknown,this paper adopts the method of combining experimental research and numerical simulation to study the flow condensation characteristics of R134 a in the pump-assisted heat pipe.The experimental facility about the test of pressure drop in pump-assisted heat pipe was built.The experimental investigation about pressure drop characteristics during flow condensation of R134 a in pump-assisted heat pipe at different mass flux and vapor quality was conducted.The experimental results indicate that pressure drop increases with the increasing vapor quality and the mass flux.The experimental results were compared with three different pressure drop models,and the conclusion that Muller-Steinhagen-Heck model can better predict the characteristics of pressure drop in the process of flowing condensation is obtained.The test section of heat transfer coefficient was added on the experimental facility about the test of pressure drop in pump-assisted heat pipe.The experimental investigation about heat transfer characteristics during flow condensation of R134 a in pump-assisted heat pipe at different mass flux and vapor quality was conducted.The experimental results indicate that heat transfer coefficient increases with the increasing vapor quality and the mass flux.In addition,the growth slope of low vapor quality is higher than that of high vapor quality.The experimental results were compared with four different heat transfer models,and the conclusion that Chen model can better predict the characteristics of heat transfer in the process of flowing condensation is obtained.The flow condensation in pump-assisted heat pipe was simulated.The model of simulation was established and chosen.The conclusion was obtained that SST k-? model was chosen as the turbulent model,the VOF model turbulent was chosen as the multiphase model,the Lee model was chosen as the heat and mass transfer model and3000 was chosen as the phase change factor,which can better describe the flow condensation heat transfer process.The numerical simulation results of flow condensation under different flow rates are analyzed.The results indicated that annular flow is the main flow pattern in the process of condensation,the gas velocity in the center of the tube isfaster than that of the round tube,the liquid phase temperature is lower than that of the gas phase,and the liquid phase has a certain degree of supercooling.The simulate results of the pressure drop are compared with the Muller-Steinhagen-Heck correlation,and the results of heat transfer are compared with the Chen correlation.The results show that the error is within the allowable range.The research provides a theoretical reference for the selection of the pump,the design of the heat exchanger,the optimization of the system and the study of two-phase flow.