Experimental analysis of air flow patterns in perfomance of flat plate solar collectors

Abstract

Solar drying is one of the promising methods of reducing post-harvest losses in rural areas. Studies have shown that, heat transfer mechanisms in a solar collector influences the performance of solar dryers. This study aims at improving heat transfer in flat plate solar collectors by designing different air flow patterns inside the collector. Three flat plate solar collectors were constructed by using Pterocarpus timber (Mninga) and tested for their effect in heat transfer at various flow patterns. Three different flow patterns namely: single duct front pass, double duct parallel flow and double duct counter flow were designed and tested. Experimental results show that collector efficiency of single duct front pass, double duct front pass and double duct counter flow were 30.6, 36.1 and 38.2% respectively. It was found that, double duct flow gives improved performance compared to single duct flow due to the increased heat transfer area. In additional, double duct counter flow showed superior performance compared to double duct parallel flow due to extended heat transfer area and the advantage of air preheating at the inlet which reduces heat losses through glazing. Through this study, it was concluded that, solar collector designs with double duct counter flow can improve collector performance for up to 8.3% compared to single duct front pass.

Three-Dimensional Numerical Simulation of a Flat Plate Solar Collector with Double Paths

“…Ramadhani et al [22] present a study to improve the heat exchange in the solar drier, the authors carried out a comparative study between a flat air solar collector with a single passage, salary collector with double passage (flow parallel) and a solar collector with double passage (flow against current), the results show that the latter model gives better thermal efficiency. So, they noticed that the value of the efficiency of the double duct countercurrent sensor equals 38.2% i.e., an improvement of 8.3% compared to a single duct sensor, they concluded that the double duct counter-current sensor has a large exchange surface therefore an increase in the heat exchange between the absorber and the heat transfer fluid.…”

Intensification of a flat solar collector efficiency

“…The properties of the glass cover are also important; thus, a high transmittance and low reflectance in the visible range and low absorbance and transmittance in the infrared range must characterize the glazing material. Generally, increasing the glass thickness or the number of glass sheets leads to the reduction of the transmittance [9]. The effects of the number of glass sheets and the glazing properties on the thermal performance of a solar collector were also considered in references [10][11][12][13].…”