An experimental study of in-tube evaporation of R-22 inside a 6.5-mm smooth tube

Abstract

Two-phase flow pattern, friction, and heat transfer characteristics for R-22 inside a 6.5 mm smooth tube are reported in this study. The range of mass flux is between 50 and 700 kg/m(2) s. The flow pattern map proposed by Weisman et al. (Weisman, J., Duncan, D., Gibson, J., Crawford, T., 1979. Effect of fluid properties and pipe diameter on two-phase flow pattern in horizontal lines. Int. J. Multiphase Flow 5, 437-462) gave a satisfactory flow pattern prediction, and the Klimenko and Fyodorov (Klimenko, V.V., Fyodorov, M., 1990. Prediction of heat transfer for two-phase forced flow in channels of different orientation. In: Proceedings of the Ninth International Heat Transfer Conference, vol. 6, pp. 65-70) criterion shows an excellent classification of the stratified and unstratified flow pattern. The two-phase multipliers are strongly related to the flow pattern, and it is found that the two-phase multiplier is dependent upon mass velocities for stratified-wavy flow pattern. In addition, the two-phase heat transfer coefficient for stratified-wavy flow pattern is found to be insensitive to the change of vapor quality, and is approximately proportional to q(0.6-0 7). (C) 1998 Elsevier Science Inc. All rights reserved.