Volume No. 5 Issue No.: 1 Page No.: 53-59 July-September 2010

 

ENHANCEMENT OF HEAT TRANSFER RATIO IN A SOLAR AIR DUCT WITH W-SHAPED ROUGHENED ABSORBER PLATE

 

A.M. Lanjewar*, J.L. Bhagoria and R.M. Sarviya

Department of Mechanical Engineering, M.A.N.I.T., Bhopal-462007 (INDIA)

 

Received on : January 25, 2010

 

ABSTRACT

 

Solar collectors (air heaters) have low thermal efficiency because of low convective heat transfer coefficient between the air and absorber plate, which leads to higher temperature of the absorber plate causing maximum thermal losses to environment. It is therefore necessary to enhance convective heat transfer coefficient for improving the performance of solar air heaters. Artificial roughness has been successfully used for enhancing heat transfer in solar air heaters. Roughness and flow parameters such as relative roughness height (e/Dh), relative roughness pitch (p/e), angle of attack (α) and Reynolds number (Re) have a combined effect on heat transfer enhancement. A term heat transfer enhancement ratio has been defined by the equation Nur/Nus. Experimental investigation has been carried out to study heat transfer enhancement by using W-shape ribs on absorber plate of solar air heater, the roughened wall being heated while the remaining three walls insulated. The roughened wall has relative roughness height (e/Dh) 0.018, relative roughness pitch (p/e) 10, rib height 0.8 mm, angle of attack in the range of 30°

 

Keywords : Solar air heater, Heat transfer enhancement ratio, W-shape ribs, Reynolds number, Absorber plate

 

 

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