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Description
As one kind of natural refrigerants, R170 and its mixtures can be used to replace R22 and R503 in some refrigerators and heat pump systems. For example, R170 is an important component of mixed-refrigerants for the low-temperature Joule-Thomson refrigerator. With various mixed-components, the system can achieve different performances. Accurate knowledge of the heat transfer of pure fluids is the first process in understanding the behavior of the multi-component mixtures. Thus, in order to appropriate use R170 and its mixtures, the condensation heat transfer data of R170 are very important.
In this work, condensation heat transfer of R170 in a horizontal smooth tube with inner diameter of 4 mm is numerically simulated with VOF model. The vapor and liquid phases are assumed to be turbulent and laminar, respectively. The inlet saturation pressure of R170 is 2 MPa and the average wall heat flux is 60 kW m-2, mass fluxes vary from 100 kg m-2 s−1 to 250 kg m-2 s−1. The simulation results show that the heat transfer coefficient increases with the increasing vapor qualities and the increasing mass fluxes. These numerical heat transfer data agreed well with the previous experimental results. In addition, in this paper, the variation of heat transfer coefficient and liquid film thickness along the tube is also simulated, respectively. Along the flow direction, the heat transfer coefficient becomes smaller, the liquid film thickness at the bottom of the tube increases consistently which means gravity effect shouldn't be neglected in the present work. Furthermore, transition flow, slug flow and plug flow had been numerically observed in this simulation, these flow patterns similar with the previous experimental phenomena.
