Numerical simulation of capillary tubes. Application to domestic refrigeration with isobutane

Abstract

This work presents the implementation and validation of a numerical model that simulates the thermal and fluiddynamic phenomena inside capillary tubes. The algorithm is based on a two-phase flow model where the governing equations (continuity, momentum, energy and entropy) are integrated over the discretized fluid domain and solved by means of a step-by-step scheme. The numerical procedure considers four different transitional regions (subcooled liquid region, metastable liquid region, metastable two-phase flow region and equilibrium two-phase flow region), allows the prediction of both critical and non-critical flow conditions, and evaluates the heat exchanged between the capillary tube and the compressor suction line. The model predictions have been compared against experimental data sets including adiabatic and non-adiabatic conditions. In addition, a parametric study on capillary tubes used in household refrigerators and working with isobutane has been carried out (different geometric conditions were considered).