Numerical simulation and experimental comparison of the R12, R22 and R134a flow inside straight and coiled helical capillary tubes

This paper presents a numerical simulation for adiabatic condition of the R12, R22 and R134a flow through straight and helically capillary tubes and also an experimental investigation of the R134a flow inside straight and helically tubes. Therefore, the two-phase flow is developed by using Drift flux model (DFM) with proper friction factor for both straight and helical capillary tubes. The conservation equations of the mass, energy and momentum are numerically solved using the 4(th) order Runge-Kutta method. Numerical model is validated by the previously published paper and also by present experimental results. The effect of refrigerant, inlet pressure, inlet temperature, degree of sub-cooling, capillary tube's geometry and dimension are studied. The results show that mass flux increases linearly as degree of sub-cooling increases as well as by increasing of coiled diameter and tube diameter. Moreover, void fraction and vapor quality's variation has same trend along coiled and straight capillary tubes.