Condensation of R-134a inside a helically coiled tube-in-shell heat exchanger

This article presents an experimental investigation of heat transfer and pressure drop characteristics of R-134a condensing inside a horizontal helical coil tube with the cooling water flowing in the shell in counter flow direction. The test runs are performed at vapor saturation temperature 35 +/- 0.5 and 40 +/- 0.5 degrees C for the mass flux varying from 100 to 350 kg m(-2) s(-1) and vapor quality ranging from 0.1 to 0.9. The flow regimes observed during the experiment have been plotted on Taitel and Dukler and mass flux versus vapor quality flow map. The transitions between different flow regimes have also been discussed. The effect of mass flux, vapor quality and saturation temperature on the heat transfer coefficient and pressure drop have been investigated. The experimental results of the helical coil tube are compared to straight tube. The thermodynamic advantage of helical coil over straight tube is evaluated in terms of enhancement parameter. The enhancement parameter is higher than one for mass fluxes lower than 200 kg m(-2) s(-1). The correlations have been developed to predict two-phase Nusselt number and frictional pressure drop multiplier during condensation of R-134a inside horizontal helical coil tube. (C) 2014 Elsevier Inc. All rights reserved.