Employing rough surfaces and nanofluids in solar heater ducts are recognized as effective techniques to improve thermal performances of these devices. In this paper, the second law of thermodynamics analysis is performed for nanofluid turbulent flow in a solar heater duct with rib roughness on the absorber plate. The effects of different parameters containing rib height, rib wedge angle, rib pitch, Reynolds number, and nanofluid concentration on thermal and frictional irreversibilities are investigated. The results indicated that the thermal entropy generation decreases about 11.1% by using nanofluid with concentration of 0.04. The frictional and thermal entropy generations decrease by increasing the rib pitch. Moreover, the thermal entropy decreases about 21.05% by increasing the rib height in the range of 0.025 to 0.033 for Re=3200. Finally, it is found that the thermal entropy generation decreases by increasing the wedge angle of the rib.

Keywords