Abstract
The condensation of refrigerants outside the tubes of liquefied natural gas (LNG) at low temperatures is the main factor affecting the performance of the LNG intermediate fluid vaporizer (IFV). In this paper, a CFD model is established to investigate the condensation heat transfer characteristics of refrigerants outside a horizontal plain tube at low temperatures over a wide range of wall subcooling. The model, based on the combination of the VOF multiphase model and Lee phase change model, agrees well with the experimental data. The transient condensation heat transfer coefficient is obtained and the periodic dripping characteristics of the condensate are analyzed. Due to the decrease of the interfacial mass transfer with the pressure decreasing, there is a peak of the periodic-averaged heat transfer coefficient with the variation of the saturation temperature, which is different from that of the Nusselt's prediction. The saturation pressures corresponding to the peak values of the periodic-averaged heat transfer coefficients at the subcooling of 10 °C are all in the range of 0.35–0.65 MPa for the four different refrigerants. In addition, the surface tension plays a positive role in the heat transfer process as the condensate film is pulled towards the wall and thinned. In view of the heat transfer performance along the whole LNG tube, dimethylether (DME) and butane can be considered as the intermediate fluids in the future design of the IFV by taking account of the comparison with six different refrigerants.
Published Version
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