A-Type Heat Exchanger Simulation Using 2-D CFD for Airside Heat Transfer and Pressure Drop

A-Type heat exchangers are used to meet required heat load with minimum duct dimensions in air-conditioning applications. This greatly reduces the air-conditioning system footprint in residential and commercial applications. The angle and tube spacing of the A-type heat exchangers should be optimized for minimum duct size and maximum heat load. However, existing air side heat transfer and pressure drop correlations may not be applicable for A-type heat exchangers due to non-uniform air velocity profile and temperature distribution in the heat exchanger. In this paper, a new technique is proposed where a segment-by-segment – NTU based coil model is coupled with automated 2-D CFD simulations of air flow through the heat exchanger. The 2-D CFD simulations are used to calculate the heat transfer coefficient on each tube as well as the inlet air velocity profile on the coil face. The segmented – NTU solver calculates NTU based on the CFD calculated heat transfer coefficient on the airside, the refrigerant side heat transfer (from available correlations), and tube-fin arrangement. In the current investigations, a parametric study was performed by varying the tube pitch, row pitch and the coil angle. The proposed framework is used to automatically generate the mesh and run the 2-D double precision CFD simulations using commercial CFD tools for the different configurations. The – NTU calculations are performed using a validated segment by segment fin and tube heat exchanger model developed by the authors. The simulation results for each coil configuration were compared against the base line heat exchanger configurations. The trade-off between the heat exchanger enclosure volume and material cost is presented.