EXPERIMENTAL INVESTIGATION ON FLOW CONDENSATION HEAT TRANSFER OF METHANE/ETHYLENE MIXTURE INSIDE A HORIZONTAL SMOOTH TUBE

Methane (R50) and ethylene (R1150) are important components in mixed-refrigerant Joule-Thomson (MRJT) refrigeration systems. Among many efforts to improve MRJT refrigerators, the work focusing on the properties of condensing heat transfer in mixtures is essential. Therefore, this paper aims to investigate these characteristics of high-temperature glide mixture R50/R1150 (26.7/73.3% molar fraction) inside a horizontally placed smooth tube. The experiments were done for varying saturation pressures (1.7-2.3 MPa), mass fluxes (101-391 kg m^-2 s^-1), and the entire range of vapor qualities. The results indicate that higher heat transfer coefficients (HTCs) occur at larger mass fluxes and smaller saturation pressures. In addition, the effect of temperature glide was discussed by comparing the HTCs of R50/R1150 with those of R50/R170 reported in the previous literature under the same test condition. It is indicated that higher temperature glide contributes to worse heat transfer performance. Moreover, six existing correlations combined with the equilibrium model were employed to predict the HTCs of R50/R1150. All predictions exhibit an underestimation of the HTCs, and only Dobson and Chato correlation and Shah correlation presented reasonable predictions with a mean absolute relative deviation (MARD) under 30%. Therefore, a new and improved heat transfer correlation was developed based on the pure fluid correlation proposed by Shah. The correlation takes into account the effects of temperature glide and mass transfer resistance and draws on experimental data for hydrocarbon mixtures reported in the existing literature. Comparison with the experimental data shows that the new correlation has good applicability to hydrocarbon mixtures, providing satisfactory predictive values of R50/R1150 with a MARD of 14% and 95.3% of the data within ± 30% deviation.