Condensation of R-134a inside micro-fin helical coiled tube-in-shell type heat exchanger

Abstract

In this study, condensation heat transfer coefficients and frictional pressure drops of R-134a inside a micro-fin helical coiled tube with the cooling water flowing inside the shell in opposite flow direction are experimentally investigated. The inner tubes comprise of one smooth straight tube and one micro-fin helical coiled tube, which are made of copper. The experimental measurements are carried out at mass fluxes of 75, 115, 156 and 191 kg m−2 s−1 and saturation temperatures of 35° and 45 °C. In addition, the experimental data of a micro-fin helical coiled tube have been plotted on the mass flux versus vapor quality flow map and Tailtel and Dukler flow map. The transitions between different flow regimes inside micro-fin helical coiled tube have also been discussed.Moreover, the effect of mass flux, vapor quality and saturation temperature of R-134a on the heat transfer coefficients and pressure drops are examined. Comparisons between smooth straight tube and micro-fin helical coiled tube are also discussed. The experimental results show that the micro-fin helical coiled tube produces a higher heat transfer coefficient and a frictional pressure drop compared to smooth straight tube. The new correlations have been proposed to predict the Nusselt number and frictional pressure drop multiplier during condensation of R-134a inside micro-fin helical coil tube.