Transverse wedge-shaped rib roughened solar air heater (SAH)-Exergy based experimental investigation

The major challenge faced in heat transfer augmentation in roughened solar air duct is the formation of viscous sublayer near heat transferring surface. The present investigation uses main air supply flow under roughened duct mounted with transverse wedge shaped roughened absorbers for the heated air jet delivery. This technique is prolific as it provides the ambient cool air to the entire absorber plate surface as well as the roughness element on the heated absorber plate that considerably enhances the heat transfer coefficient. Data of everyday was documented under diverse range of parameters viz., Re 3000-18000, rib wedge angle (phi) of 8 degrees, 10 degrees, 12 degrees and 15 degrees, relative roughness pitch (p/e) of 60.17(phi)(-1.0264) < p/e < 12.12 and relative roughness height (e/D-h) of 0.015-0.033. The massflow rate ranges from 0.0174 to 0.0352 kg/s. Maximum exergetic efficiency (eta(II)) observed was 4.95 corresponding to (To-Ti)/I of 0.035 at a massflow rate of 0.0346 kg/s. Also maximum (eta(II)) was 4.14 at p/e = 7.57, e/D-h = 0.033 and at 4 = 10 at a massflow rate of 0.03 kg/s with respect to varying geometrical configuration. Maximum exergy efficiency of 4.95% accomplished justifies that the use of transverse wedge shaped roughness element is prolific for enhancing heat transfer. (c) 2021 Elsevier Ltd. All rights reserved.