Abstract:
In this study, the heat transfer and flow characteristics of refrigerant condensing under forced flow conditions inside horizontal tubes are numerically investigated. An implicit finite difference method is used to solve the continuity, momentum and energy equations of two- phase flow. The results are presented in form of the distributions of wall heat flux, vapor temperature, wall temperature, coolant temperature and pressure along the tube. The results from the predictioil are compared with the measured data reported in the literature. The heat transfer coefficient from the correlation of Lee, Teng and Lu [ll] is used to predict wall heat flux. This correlation is formed from the combination of the single phase forceconvection of superheated vapor term and the saturated condensation term. The saturated condensation term is calculated using the force convectiot~ heat transfer coefficient from the correlation of Azer, Abis and Swearingan [lo], Shah [8] and Cavallini and Zecchin [28]. The results show that the correlations of Azer, Abis andSwearingen [lo] and Shah give good agreement for R12 and R22, respectively. It is found that, the degree of superheat influences the heat transfer and pressure drop characteristics. The wall heat flux and the pressure gradient increase with increasing degree of superheat. The presented model can be used for the efficient design when systems are assigned to utilize alternative refrigerant.