A numerical model of a horizontal-spiral, two-phase flow

The thermal performance of a horizontal-spiral, two-phase flow with low heat flux and mass velocity is modelled. Refrigerant flows helically in a single plane where the axis of the spiral is horizontal. The focus of this paper is to predict the heat transfer and pressure drop of the refrigerant. The refrigerant two-phase flow is modelled as homogeneous and one-dimensional. Empirical correlations for straight, two-phase flow as well as single-phase, helical flow are used. An equation set of continuity, momentum, energy, and refrigerant's equation of state are presented. The set of first-order differential equations are integrated using a fourth-order Runge-Kutta algorithm, with a local, root-bisection iteration method for determining the local density gradient. Numerical results of the spatial variation of enthalpy, density, velocity, pressure, and temperature are presented, and comparisons are made to show the effect of the curved-tube on the solution. In addition a second law analysis of the flow is made in order to quantify and compare individual losses. It is found that the heat transfer performance at high quality is improved by the helical flow by five percent. Corresponding pressure drop losses also increase by eight percent.