Two-phase R1234yf flow inside horizontal smooth circular tubes: Heat transfer, pressure drop, and flow pattern

Abstract

A literature review on the two-phase flow inside plain tubes, especially for the refrigerant R1234yf, is conducted in this research. The flow boiling, condensation, and visualization of this low GWP refrigerant were examined experimentally to measure the heat transfer coefficients and pressure drop of the refrigerant, and also to present a flow pattern map. The measurements were carried out on smooth circular tubes with internal diameters of 8.2 mm for the mass velocity ranging from 95 to 410 kg m−2 s−1, vapor qualities from 0.12 to 0.92, and saturation temperatures from 26.3°C to 33.5°C. For the range of test parameters, the flow patterns were observed and compared with the work of Wojtan et al. Also, the experimental results were analyzed to evaluate the effect of mass flow and vapor quality. Generally, both parameters increase the heat transfer and pressure drop in the boiling and condensing flows. Also, the experimental results were compared with the existing models proposed to predict the heat transfer coefficient and pressure drop. Two correlations, based on the previous studies, were proposed to improve the accuracy of the heat transfer coefficient prediction. the correlation of Dobson et al. was adapted and resulted in a mean absolute error of 11.9%. Also, the Liu and Winterton model for boiling was modified to reduce its mean absolute error from 25.6% to 13.4%.