Numerical Model of Capillary Tubes: Enhanced Performance and Study of Non-Adiabatic Effects

Abstract

In the present work a numerical model to simulate the thermal and fluid-dynamic phenomena inside non-adiabatic capillary tubes is presented. It consists of an improved version of the distributed model detailed in Ablanque et al. (2010). The model is based on a pseudo-homogeneous 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 main novelty of the improved algorithm is its enhanced capability to address common convergence issues typically found in distributed models for non-adiabatic capillary tubes (i.e. flow discontinuities caused by the refrigerant re-condensation). In addition, the newest version of the model allows the simulation of both concentric and lateral configurations. This work presents the detailed numerical aspects of the new model, the implementation and validation of the lateral configuration, and a detailed study of its performance when addressing the aforementioned numerical difficulties.