Effect of jet-impingement and surface roughness on performance of solar air heater: Experimental study and its optimization

Abstract

The performance of solar air heaters can be improved by either active or passive techniques. In this research manuscript, both active and passive technique is used to enhance the thermal characteristics of the solar air heater. The proposed solar air heater consists of an innovative approach in which an impinging air stream and wired ribs (arranged in the multiple V-pattern over the absorber plate) are used for performance improvement. The impinging air stream is synchronized in such a way that it strikes the ribs to promote local turbulence. The investigation has been performed considering various design parameters like relative width ratio, relative roughness height/pitch, the angle of attack, the stream-wise jet pitch, the span-wise jet-wise pitch, and the jet diameter ratio. The results have shown that the presence of the ribs opposite to the impinging air stream promotes local turbulence over the ribbed surface which ultimately enhances the thermal characteristics of the solar air heater. The proposed design is also been optimized using the surface response methodology and the significance of the various roughness parameters on the thermal characteristics has also been predicted. Additionally, the best performance observed is 3.12 at a relative width ratio of 5, relative roughness height/pitch of 0.043/10, angle of attack of 60˚, stream-wise jet pitch of 0.4, span-wise jet-wise pitch of 0.84, and jet diameter ratio of 0.064.