Numerical Modeling and Experimental Validation of the R-134a Flow through an Adiabatic Helical Capillary Tube

This paper presents a numerical simulation and an experimental validation of the R-134 flow through the adiabatic helical capillary tubes. The two-phase flow was developed by drift flux model for both straight and helical capillary tubes. The conservation equations of the mass, energy and momentum are numerically solved using the fourth order Runge-Kutta method. This model is validated by previously published experimental and numerical results and also by present experimental results. The effect of various inlet conditions such as pressure, temperature, degrees of sub cooling, and capillary tubes geometric parameters such as tube diameter and length and also coil diameter were studied. Moreover, the pressure variation along helical capillary were experimentally obtained using a closed loop experiment apparatus and vapor quality and void fraction by numerical simulation in same conditions. The comparison between the present measured data and the present developed drift flux model results give an absolute error of 7%. The results of our study show that in the same length and condition, mass flow rate through helical capillary tube with coil diameter of 40 mm is 11% less than that of straight capillary tube where helical type reduces the tube length by 24%. This developed model can be used as an effective tool for designing and optimizing air conditioning with helical capillary tube for various refrigerants.

Keywords:

adiabatic , capillary tube , experimental , helical , numerical