Simulation and experimental studies of R134a flow condensation characteristics in a pump-assisted separate heat pipe

We combine experimental research and numerical simulations to investigate the complex and unknown flow condensation heat transfer process in a pump-assisted separate heat pipe (PASHP) employing R134a. The Chen model and Müller-Steinhagen-Heck model coincide with the experimental pressure drop and heat transfer, respectively, after comparing three correlations of the pressure drop and four correlations of the heat transfer. After analysing the establishment and selection of a model to simulate the flow condensation characteristics in a PASHP, we conclude that the turbulence model, multiphase flow model, and heat and mass transfer model can be described using the SST k-ω model, VOF model, and Lee model, respectively. The phase transformation factor r = 3000, the simulation results and the Chen correlation are all consistent. The pressure drop and heat transfer coefficient increases with increasing mass flow and vapour quality. The simulation results of the pressure drop and heat transfer coefficient are compared with those of the Chen and Muller-Steinhagen-Heck correlations, respectively, showing satisfactory agreement between the simulated and the calculated values. This research provides a theoretical reference for the selection of the pump, design of the heat exchanger, optimization of the system and study of two-phase flow.