Modelling of fin-and-tube evaporators considering non-uniform in-tube heat transfer

This paper is devoted to the presentation of a new model for fin-and-tube evaporators, focusing on the solid core simulation and its integration with a quasi-homogeneous two-phase flow model for the in-tube refrigerant flow. Special attention is given to separated in-tube flow patterns (stratified, stratified-wavy), because of their importance in liquid overfeed and domestic refrigerator evaporators and the impact on the solid core temperature distribution. The paper presents the solid core formulation and numerical method, the in-tube two-phase flow model, and describes the proposed integration algorithm between them. A selected single-tube baseline case is analysed in full detail, showing the impact of stratified flow on the fin-and-tube temperature distributions. Additional studies are finally presented analysing different flow transitions (single phase to stratified flow, stratified-wavy flow to annular flow, annular flow to partial dry-out) and several operating parameters (flow regime, tube material, tube thickness). Special attention is given to the influence of the flow pattern on the fin-and-tube core temperature profiles.