TWO PHASE FLOW CFD ANALYSIS OF REFRIGERANTS IN A CONDENSER PIPE FOR PREDICTION OF PRESSURE DROP AND PUMPING POWER

Abstract

With the ever growing need of achieving optimum cooling at chip level at the expense of low input pumping power and keeping in check the Global Warming Potential (GWP) & Ozone Depletion Potential (ODP) has given rise to “two-phase on chip cooling” with nature friendly refrigerants. Currently, “air-cooling” and “single-phase water on-chip cooling” using copper micro-channel coolers are being used but “two-phase on chip cooling” with refrigerants have a very large scale & long lasting advantages over the prior. However, due to the perceived complexity of modelling two-phase flow, this solution is not yet well understood. Modelling of two phase flow, particularly liquid – vapor under diabatic conditions inside a horizontal tube using CFD analysis is difficult with the available two phase models in FLUENT due to continuously changing flow patterns. This study is an attempt at modelling a two-phase flow for various refrigerants for the proper prediction of pressure drop and pumping power. In the present analysis, CFD analysis of two phase flow of refrigerants inside a horizontal condenser tube of inner diameter, 0.0085m and 1.2m length is carried out using homogeneous model under adiabatic conditions. The refrigerants considered here are R134a, R407C and the newly developed Du-Pont/Honeywell R1234yf. The analysis is performed at saturation temperature to evaluate the local frictional pressure drop. Using Homogeneous model, average properties are obtained for each of the refrigerants that is considered as single phase pseudo fluid. The so obtained pressure drop data is compared with experimental data and the separated flow models available in literature.