Heat transfer enhancement in a solar air heater utilizing novel rotating spiral baffles

Abstract

This study presents a substantial enhancement in the performance of solar air heaters (SAH) through the introduction of innovative rotating spiral-shaped baffles on the absorber plate, designed to optimize airflow within the duct and improve heat transfer. The results underscore the critical importance of fine-tuning geometric parameters, including relative roughness height (e/H: 0.4–1) and relative roughness pitch (P/e: 4–10), as well as the Reynolds number (Re: 4000–12 000), to achieve superior thermal efficiency. The optimization of these parameters is essential for maximizing performance while effectively managing flow resistance and turbulence. Experimental testing, conducted under a solar simulator (EN-12975-2 standard: irradiance uniformity of 10.47%, average solar irradiance of 955 W/m2), identified the configuration of P/e-8, e/H-0.8, and Re-12000 as the optimal combination. This setup yielded a maximum reduction of 17.29% in plate temperature (Tp), a 7.48% increase in outlet temperature (To), 63.33% augmentation in useful heat gain (Qu), and a 64.86% improvement in thermal efficiency (η) compared to a smooth duct. These findings provide key insights for advancing the design and operational efficiency of SAH systems. A field study to evaluate the practical applicability of this modification is recommended as the next step for further investigation.