Impact of the Heat Transfer Coefficient Determination Method on the Simulation of the Operation of Fin-and-Tube Cross-Flow Heat Exchangers at a Non-Uniform Inflow of Mediums

The work deals with a thermodynamic analysis of finned liquid-gas cross-flow heat exchangers. Analyzing such devices, it is important to determine the heat transfer coefficients on the liquid and the gas side. The analysis basic problem is determination of the of the heat transfer coefficient from the finned surfaces to the flowing gas due to a non-uniform flow of gas through the exchanger. The form and the scope of the gas inflow maldistribution were determined experimentally for two different fins, cross-flow heat exchangers with elliptical tubes. Six Nusselt number correlations were selected and were used to calculate the heat transfer coefficients for measured data. The values of heat transfer coefficient were also computed based on numerical simulations using numerical models of repetitive fragments of the tested heat exchangers. The Wilson plot method was also used. The heat transfer coefficient values were put into an in-house computer code and the experiments were simulated numerically. The comparison of experimental and computational data makes it possible to evaluate different methods of the heat transfer coefficient determination. The simplest Berman correlation for the Nusselt number as well as the computational fluid dynamics based approach gave the best results.