AN HOMOGENEOUS MODEL FOR ADIABATIC CAPILLARY TUBES

This paper presents a homogeneous two-phase how model, CAPIL, which is designed to study the performance of adiabatic capillary tubes in sma ll vapour compression refrigeration systems, in particular household r efrigerators and freezers. The model is based on the fundamental equat ions of conservation of mass, energy and momentum that are solved simu ltaneously through iterative procedure and Simpson's rule. The model u ses empirical correlations for single-phase and two-phase friction fac tors and also accounts for the entrance effects. The model uses the RE FPROP data base where the Carnahan-Starling-DeSantis equation of state is used to calculate the refrigerant properties. The model includes t he effect of various design parameters, namely the tube diameter, tube relative roughness, tube length, level of subcooling and the refriger ant flow rate. The model is validated with earlier models over a range of operating conditions and is found to agree reasonably well with th e available experimental data for HFC-134a. (C) 1997 Elsevier Science Ltd.