Predicting steady two-phase flow of refrigerants under variable heat flux

Abstract

Two phase flow of refrigerants during evaporation and condensation subjected to variable heat flux is being studied. Several types of refrigerants (R134a, R12, R22, R32 and R143a) are being studied as the internal fluid of the heat exchanger with major emphasis on R134a while water is assumed to be the outer fluid. Parallel and counter flows are both being studied where results show the favorability of parallel flow heat exchangers over counter flowheat exchangers unlike the results of single phase heat exchangers. Numerical analysis of refrigerant flow is investigated using finite volume method where both thermodynamic and hydrodynamic refrigerants properties are being calculated and checked at each control volume to assure convergence of iterations. Axial heat conduction through the inner pipe is being studied for constant heat flux and variable heat flux. Results have shown that neglecting the significance of axial heat conduction where constant heat flux is applied could over predict the heat exchanger size while under predict it in the variable heat flux case.