General equation for flow condensation heat transfer coefficient in different orientations of helical coils of smooth tubes using genetic programming

Abstract

There are several experimental studies on heat transfer during condensation in coiled tubes. But there is no well-verified method for calculating of heat transfer coefficient. In this study, a general non-linear correlation for estimation of heat transfer coefficient during flow condensation in different orientations of smooth coiled tubes is proposed. The correlation has been obtained by correlating the Nusselt number with two-phase Reynolds number, reduced pressure, Froude number, tube to coil diameter ratio, and inclination angle of coil axis to horizontal using Genetic programming (GP). This model has been validated with 503 experimental data points from 9 sources, which include different tube diameters, coil diameters, inclination angles, orientations, working fluids, mass fluxes and saturation temperatures. The new correlation predicts experimental data points with an excellent value of average absolute relative deviation (AARD) of 9.20%. The same database is also compared to 9 available correlations for straight and coiled tubes. Their deviations are significantly higher than the present correlation. In addition, impact of each input parameter on heat transfer coefficient in coiled tubes has been discussed.