two-phase, cfd, phase change, numerical methods, simulation
The use of computational fluid dynamics (CFD) tools is gaining popularity in the analysis of flow phenomenon in components used in air-conditioning and refrigeration systems. However, simulation of two phase (e.g., gas and liquid or oil and refrigerant) and phase changing (evaporation or condensation) flow is still unfeasible in many engineering problems. In this review, the development and status of direct numerical simulation of two-phase phase changing flow is discussed. The scope of this review is primarily focused on the boiling and evaporation methods that are most frequent in HVAC&R applications but generally relevant to all phase change simulations. The phase change method fundamentally depends on the properties and capabilities of its underlying multiphase methods and all studies of multiphase methods have been a naturally followed by their extension to phase change problems. Thus a comprehensive review on both multiphase and phase change numerical method is presented with a particular focus on the front capturing methods. Although developments of numerical methods for direct multiphase and phase change methods have shown promising results in solving simple phase change problems, applications to larger scale problems such as coiled tubes and heat exchangers unit still seems rough and has not been as successful. There are still major obstacles to overcome such as the mesh resolution requirement, higher order discretization schemes on unstructured grids, the nucleation sites, sharp interface properties and the associated accuracy and stability issue among others. Review of some large scale simulations and the underlying challenges are presented.