Numerical study of regenerative evaporative coolers for sub-wet bulb cooling with cross- and counter-flow configuration

•Pre-cooling the working air enhances the wet-bulb effectiveness of IEC.•Counter-flow REC resulted in 30% higher wet-bulb effectiveness in comparing to cross-flow REC.•Increasing the working air to total inlet air ratio resulted in higher wet-bulb effectiveness for counter-flow REC.

In this study, the numerical simulations of Cross- and Counter-Flow Regenerative Evaporative Coolers (REC) and a Cross-Flow Indirect Evaporative Cooler (IEC) are presented, using one set of the governing equations. The governing equations of heat and mass transfer are discretized using Finite Difference Method (FDM) and solved by an iterative method in MATLAB. The numerical results of the presented simulation are validated for Cross Flow IEC, Cross and Counter Flow REC against experimental data, which resulted good agreement between aforementioned simulations and experimental data. The Numerical simulation shows contour plots of two-dimensional temperature across the exchanger for Cross-Flow REC with two directions of air flows in wet channel. The impacts of pre-cooling the working air of REC are investigated and compared to a four-stage IEC, which shows that the Counter-Flow REC can produce the lowest temperature of the inlet air in comparing to both Cross-Flow REC (around 30%higher wet-bulb effectiveness) and four-stage IEC with the same air and exchanger parameters of this study. The impacts of the working air to total air ratio are also investigated for Counter-Flow REC which show that product air temperature decreases (10%–20% higher wet-bulb effectiveness) as the working air to total inlet air ratio increases (0.2 kg/kg–0.9 kg/kg).