An investigation of the effects of geometry design on refrigerant flow mal-distribution in parallel flow condenser using a hybrid method of finite element approach and CFD simulation

Flow mal-distribution in tubes is an important problem in parallel flow heat exchangers (PFHXs) which should be considered in heat exchanger modeling. In the present study, a hybrid method is developed for flow distribution forecasting based on simultaneous use of computational fluid dynamics (CFD) simulation for 3D analysis of flow in PFHX headers and finite element model for solving flow within tubes. The developed method forecasts are verified against the experimental data of a parallel flow condenser (PFC) performance. The method is then utilized to investigate the effects of tube protrusion depth, inlet tube location, inlet tube diameter and combination of tube protrusion depth and inlet tube location on refrigerant flow mal-distribution. The data indicate flow mal-distribution increment (increase of standard deviation (STD) from 0.51% to 1.77%) by increasing the tube protrusion depth from 1/4 to 3/4 of header diameter which results in about 14% increment in pressure drop and 3.9% decrement in capacity. Also, reduction of flow mal-distribution in cases of increasing the inlet tube diameter and locating the header inlet on the top of the header, a small distance away from the first tube is observed. The presented model and results can be used to accurately design PFCs.