Effect of relative roughness pitch on the performance evaluation of a solar air heater roughened with chamfered rib and groove roughness on the surface plate using CFD technique

Abstract

The heatt transfer enhancement in solar air heater (SAH) over surface can be improved by placing rib roughness element embedded on the absorber surface. The present work is concerned with the technique of enhancing the heatt transfer by providing chamfered rib along with grooved roughness on the absorber plate surface of solar air heater (SAH) was analysed by CFD based ANSYS FLUENT 16.2 commercially available software. The 2-D numerical study was performed on CFD model of solar air heater system and the analysiss has been done to get the outcome of relative roughness pitch (Pi/e of 4.5,6,8,10) on heatt transfer and frictionn factor (fr) keeping all the dimensionless parameter constant i.e. relative groovee position (g/Pi) of 0.4, relative roughness height (e/D) of 0.04 and chamfered angle (ϕ) of 18° at different Reynoldss number ranges from 3000-20000. The simulated results of mathematical modeling using renowned Reynolds averaged Navierr Stokes equations (RANS) turbulence model is validated and compared similitude the results with those of existing experimental values under similar conditions. The results implies that the value of average Nusseltt number increases with increasing the relative roughness pitch (Pi/e) and attain its maximum at Pi/e of 6 mainly due to strong reattachment location between the ribs, furthermore increase of Pi/e values from 8 to 10 the Nusseltt number found to decrease declined for all value of Reynoldss number. Thus, it emphasizes that the chamfered rib roughness at Pi/e of 6 is the strong function of Nusseltt number achieving its optimum value of heatt transfer.