Thermohydraulic performance of hybrid ribs pattern combining V and arc shape ribs in solar air heater

Abstract

ABSTRACT Solar energy is a limitless and ecological-friendly renewable energy source, which can be utilized for varieties of application ranging from heating/cooling, power generation, drying, and in heat-processing industries. Solar air heaters (SAHs) are among the best options for harnessing solar energy for thermal purposes like heating and drying. However, the performance of SAH is not sufficient to take into practical applications. Low performance of SAH is due to its low convective heat transfer capability because of smooth absorber plate. In this regard, an attempt has been made to enhance the heat transfer capability of SAH exploiting hybrid ribs in this paper. Hybrid rib roughness pattern incorporating to V shape ribs and arc shape ribs has been designed and tested experimentally in the SAH duct under the following range of Reynolds number (Re) from 2000 to 16,000. The various roughness patterns, i.e., arc angle (α), angle of attack (β), relative V ribs position (d/w), relative rib pitch (p/e), and relative rib height (e/D), have been exploited in the range of 30º-75º, 30º-75º, 0.2–0.10, 8–10, and 0.023–0.043, respectively. As a result, Nusselt number (Nu) and friction factor (f) have been enhanced significantly. Maximum enhancement in Nu has been found as 3.08 at α = 45º, β = 60º, d/w = 0.65, p/e = 10, and e/D = 0.043. Thermohydraulic performance (TP) parameters have also been evaluated for all set of parameters of hybrid ribs pattern and it found to be maximum 2.18 at α = 30º, β = 60º, d/w = 1.0, p/e = 10, and e/D = 0.043.