Experimental Analysis of a Solar Air Heater Featuring Multiple Spiral-Shaped Semi-Conical Ribs

To improve the thermal and hydraulic performance of artificially roughened solar air heaters (SAHs), the current study analyzes the thermal-hydraulic performance or thermal enhancement factor of artificially roughened solar air heaters. In present experimental research on a solar air heater's absorber plate, newly designed spiral-shaped semi-conical ribs have been explored. The spiral-shaped semi-conical ribs have been designed with the aim of reducing the pressure drop across the rib so that thermal performance may be improved with a little increase in pressure drop after integrating the ribs into the SAH mainstream flow. The higher value of thermal-hydraulic performance indicates an increased heat transfer rate with a minimum increase in pumping power. In order to achieve the highest possible thermal enhancement factor, this experimental study intends to analyze the effects of different geometrical parameters on the heat transmission and friction behavior of numerous spiral-shaped semi-conical ribs. Multiple experiments were conducted using different levels of roughness heights to optimize the rib profile parameters. The Reynolds number (Re) ranges from 3358.65 to 18,095.59, the relative roughness height (e/D_h) 0.09 to 0.227, and relative roughness pitch (P/e) 3.7 to 5.5. These multiple spiral-shaped semi-conical ribs give the maximum thermal enhancement factor of 2.85 at (e/D_h) 0.182 and P/e of 4.1 at Reynolds number 18,095.59. It has been found that current rib geometry can increase the thermal performance of solar air heaters with minimum increased pumping power with reference to rib explored by earlier researchers.