Design and application of honeycomb porous-bed solar-air heaters

Abstract The honeycomb-porous bed concept is shown to be an effective means for solar air heating. Design considerations require knowledge of the best cell dimensions, and wall coating thickness accounting for collector tilt, time of year, maximum heated air temperature and ambient air temperature. Previous studies have been extended to determine the values of cell depth to spacing ratio, width to spacing ratio, and wall coating thickness that minimize the cost per useful energy collected at various times of year and for various tilt angles, ambient air temperatures and exit air temperatures. For all conditions investigated, the cost per useful energy collected was minimized for values of wall coating thickness between 0·4 and 0·8 mil, cell depth to spacing ratios between 4 and 10, and cell width to spacing ratios between 7 and 10. A design study of a solar-air heater farm crop-drier system demonstrates a method for the determination of the best values for air temperature, air flows and solar heater area, to minimize the cost per lb of moisture removal.