Effect of wind on flow distribution in unglazed transpired-plate collectors

Unglazed transpired-plate solar air heaters have proven to be effective devices for heating air directly from ambient on a once through basis. They have found applications in ventilation-air preheating and in crop-drying. Large collectors are now routinely built that cover the sides of sizeable buildings, and the problem of designing the system so that the flow of the air through the collector face is reasonably uniform and so that there is no ‘outflow’ over part of the collector face has been seen as a challenging one. The flow distribution was analyzed in an earlier study using a computational fluid dynamics (CFD) model, but that study was limited to the case where there is no wind present. The present paper extends the earlier study to the case where there is wind. Various building orientations are examined, at a wind speed of 5 m/s. The wind was found to reinforce those factors that tend to produce outflow, and in light of this study, the recommended minimum suction velocity required to avoid outflow has been raised from about 0.0125 m/s to about 0.03 m/s, depending on the building shape. On the other hand, there are possible strategies that can be adopted to reduce the effect of wind, and these are discussed.