Simulation of refrigerants flowing through adiabatic capillary tubes

This paper presents a model for the flow of refrigerants through adiabatic capillary, tubes. The flow of refrigerant is characterized by a subcooled liquid region, a metastable liquid region, a metastable two-phase region, and an equilibrium two-phase region. The mass and momentum conservation equations for each of these four regions are converted into finite difference forms and solved using a 4th order Runge-Kutta method. The calculated results compare well with experimental data on R-22. The predictions from the model are employed to develop correlations for the design of refrigerant 134a through adiabatic capillary, tubes with the tube exit in the choked flow condition.