Experimental investigation of thermohydraulic performance of solar thermal collector for sustainable built environment

Abstract

Solar heating is a low-cost option for heating buildings, which help in the development of a sustainable built environment as it can fulfil the building heating demand. For this purpose, solar air heater (SAH) can be employed, however, insignificant performance of a typical solar air heater (SAH) restrict its applications for warming a building. Artificial roughness is the most promising way to enhance the significant performance of SAH. In this regards, novel artificial rib roughened absorber surface has been proposed and design in such a way to improve the heat transmission capability without any adverse effect. With this aim, gaps in multi open trapezoidal ribs (MOTRG) are introduced to take the benefit of secondary flow to be released through gaps concerning to high rate of convective the heat transmission and release of the enough pressure leading to low friction factor. The SAH with proposed MOTRG has been scrutinised experimentally. The distinct roughness parameter of the proposed rib configurations such as relative rib height (e/Dh = 0.023–0.054), relative gap width (g/e = 1–5), relative limb length (L/w = 0.2–1.0), relative roughness pitch (p/e = 6–12), relative width ratio (W/w = 6) and angle of attack (α = 60°), have been encompassed and tested for the Reynolds number (Re = 2000–16000). It has been noted that rib gaps significantly improved the Nusselt number (Nu) and marginally reduced the friction factor. As results, range of thermohydraulic performance has been discovered to be 3.40 to 3.99. The mathematical correlations of Nu and friction factor induced by the MORTG have been formulated as function of flow and non-dimensional roughness parameters.