Thermo-hydraulic performance enhancement of solar air heater with double-delta (Δ) triangular finned absorber plate: Experimental investigation and response optimization approach using RSM and Rao algorithm

Abstract

The energy crisis in conventional sources has led to a focus on renewable energy, with solar thermal technology emerging as a key alternative. Solar air heaters (SAHs), which capture solar energy to heat air, address significant issues like space heating and drying crops such as groundnuts, sunflowers, and corn. The performance of SAHs can be enhanced through techniques that improve the heat transfer between the circulating air and the collector. These techniques include adding thermally conductive fins, optimizing the collector’s shape and the inlet/outlet design, and introducing turbulence using obstacles like fins, ribs, or baffles. This research paper presents an experimental study and optimization of a novel SAH design with triangular fins arranged in a double-delta (Δ) pattern to improve thermo-hydraulic performance. It also examines the variation in temperature along the height of the fins attached to the novel-designed absorber plate. An experimental setup was developed at 28.8186°N, 78.6425°E for performance measurement. The fin heat transfer rate, efficiency, and friction factor were evaluated using thermohydraulic relations. The Experimental data and regression modeled response data were optimized in MATLAB R2024b software and MINITAB 22 software using Rao-1 algorithm and Response Surface Methodology (RSM), respectively. For the optimization using response surface design, three input variables were considered: solar flux (400–1000 W/m 2 ), Reynolds number (2000–8000), and fin base to height ratio (0.3–0.9). The responses analyzed included outlet temperature of circulating air, friction factor, Nusselt number, thermal efficiency of fin, exergy efficiency, and thermal performance factor. The optimum operating conditions were identified as solar intensity of 860.606 W/m 2 , Reynolds number of 5272.73, and fin base to height ratio of 0.8879, corresponding to an outlet temperature of 86.272°C, friction factor of 0.22617, Nusselt number of 121.233, fin thermal efficiency of 59.935%, thermal performance factor of 1.51288, and exergy efficiency of 8.2159%.