Heat source boundary conditions study for numerical simulation of performance of flat-tube and multi-louvered fin heat exchangers

In the previous studies on heat transfer performance of the flat-tube and multi-louvered fin heat exchangers, most of the numerical studies generally select a heat transfer unit as the computational domain for the effective realization of CFD (Computational Fluid Dynamics). The majority of the numerical studies usually simply treated the flat-tube water side as fixed wall temperature or convective heat transfer boundary conditions without checking thermal equilibrium. The present study tries to demonstrate the differences of boundary condition settings based on thermal equilibrium between the flat-tube water side and the air side of the whole heat exchangers. Revised numerical method is presented with corresponding judging error and amended parameters for fixed wall temperature and convective heat transfer boundary conditions. And computations with two types of boundary conditions are also compared. The results indicate that the heat transfer performances are nearly the same for both boundary condition amendments. Nevertheless, it is necessary to modify the boundary condition parameters of the flat-tube water side based on thermal equilibrium of the whole multi-louvered fin heat exchangers, for accurately calculating heat transfer quantities of the heat exchangers.