A new heat transfer model for flow boiling of refrigerants in micro-fin tubes

Abstract

Experimental data points of heat transfer coefficient during flow boiling of refrigerants in horizontal micro-fin tubes were collected from literature and our previous experimental work to develop a new general heat transfer model. The database contains 2221 data points covering nine refrigerants, and the involved operation conditions are as follows: mass velocity 47–835 kg m−2 s, vapor quality 0.05–0.98, heat flux 3.9–85.2 kW m−2, and fin-root diameter 2.64–11.98 mm. Six existing general heat transfer correlations for micro-fin tubes were evaluated using the present database. It was found that these correlations were incapable of providing a satisfactory prediction. Among them, the correlation proposed by Mehendale shows the best predictive ability, predicting 70.3% and 91.3% of the database within ±30% and ±50% error bands, respectively. Then a new model based on the present database was generalized by modifying Cavallini et al. correlation, and a good agreement between the new model and the database was obtained. The new model can predict 82.1% of data points within ±30% error bands with a mean absolute deviation of 18.6%, and its parametric-trend predictive ability under varied operating conditions was also verified using several datasets.