A computational and experimental analysis of a hybrid parallel/counter flow double pass solar air heater

The computational and experimental analysis of a solar air heater (SAH) with both counter- and parallel- flow features is presented. The theoretical model is based on the finite volume method (FVM) ANSYS Fluent 14.5 is used. The Solar Load Model (SLM), which incorporates a ray tracing algorithm and the ASHRAE fair weather conditions model, was used to include the effects of solar radiation to mimic actual operating conditions. The flow was modelled using the Reynolds Stress Model (RSM). The experimental test consisted of the evaluation of a hybrid SAH using K type thermocouples and 3D printed Venturi flow meters in order to determine the thermal efficiency. The CFD model was found to over predict temperature values by up to 29.3 °C when compare with experimental results. Alterations to the external convection coefficient and thermal conductivity of the external faces' material brought the difference to within 13.3 °C. Model based temperature contour plots show temperature distributions that are contrary to experimental observations. The SAH should therefore be tested with external insulation and wind speed measurements. Mesh refinement and application of a shell conduction model is required for theoretical work.