Modeling Simulation and Optimization of Solar Thermal Collector for Air Heating Systems

Abstract

The exponential rate of industrialization worldwide has resulted in unprecedented energy demand. A projection of the current trends suggests that overall energy use will continue to grow strongly doubling or even tripling by 2050. Currently, there is a lot of focus on renewable energy harvesting. Given the current scenario, solar and wind energy stand at the forefront of this movement among all renewable energy sources. In this regard, to convert solar energy into thermal energy, a novel concept of artificially roughening solar air heater (SAH) using fixed and rotating circular ribs has been employed within a two-dimensional rectangular duct to understand their effects on heat transfer and fluid flow characteristics using computational fluid dynamics (CFD). The effects of design parameters such as roughness height (e), roughness pitch (P), relative roughness height (e/Dh), relative roughness pitch (P/e), and rotational speed (N) of the circular rib are simulated for Reynolds number ranges from 3800 to 18,000 under solar air heater boundary conditions. 54 % increase in Nusselt number is observed for rib height of 1.4 mm, pitch of 10 mm, and circular rib rotation of 10000 RPM at Re = 3800 as compared with fixed ribs. The maximum thermo-hydraulic performance factor of 1.57 is achieved at a Reynolds number of 3800 for the circular ribs relative roughness height of 0.042 and relative roughness pitch of 17.86 rotating counter to flow with 10000 RPM. Significant increase in Nusselt number with rotating and fixed ribs as artificial roughness establishes the potential of this novel approach for SAHs.