Thermal-hydraulic CFD study in louvered fin-and-flat-tube heat exchangers

Heat transfer performance prediction by CFD codes is of major interest. Usually air-side heat transfer characteristics of fin-and-tube heat exchangers are determined from limited experimental data. The ability of CFD code to predict flow patterns and thermal fields allows determining the heat transfer characteristics by performing ‘numerical experiments’. CFD calculations of a 1-row automotive condenser are compared to experimental results and correlations of the literature matching the fin design and the flow conditions. Calculations are performed for different air frontal velocities. 2D models, with uniformly constant fin temperature overestimate significantly the heat transfer coefficient. 3D models, taking into account tube effects, conjugate heat transfer and conduction through the fin are in better agreement with the experimental results. However, even if an offset in noticed between CFD calculations and the experimental results, the trends are comparable and CFD study permits to reach local information, leading to better understanding of the physical phenomena involved in compact heat exchangers. An attempt for 2D unsteady flow has also been performed. Results are discussed in terms of flow pattern and heat transfer coefficient behaviour.