Prediction of Heat Transfer Characteristics of Binary Refrigerant Mixtures in a Falling Film Type Plate-fin Evaporator

Abstract

This paper deals with the characteristics of heat transfer and pressure drop of R 22, R 134a pure refrigerant and R 134a/R123 refrigerant mixtures in a falling film type plate-fin evaporator. The refrigerants have been tested in the ranges of heat flux from 3 to 20 kW/m² and mass velocity from 50 to 100 kg/m²s. It is clarified that heat transfer characteristics of evaporation in the present experimental range are not affected by shear stress. Taking the fin efficiency into consideration, a correlation equation of heat transfer coefficient is proposed. The characteristic of pressure drop is also proposed by modifying friction factor of Soliman's equation. Furthermore, a prediction model for evaporation of mixtures in a plate fin heat exchanger is developed based on the assumption that the phase equilibrium in a cross-section of the refrigerant path is established. The prediction results are in good agreement with the experimental data.