Numerical Study on the Effect of Structural Variation of S‐Shaped Flow Channel Absorber on the Thermal Performance of Line‐Focusing Fresnel Lens Solar Collector

ABSTRACT As a clean and renewable energy source, solar energy development and utilization have garnered significant attention. This study investigates the potential of Fresnel lenses to enhance the thermal efficiency of solar collectors by analyzing the effects of water flow channel structure and flow rate on heat gain. A physical module with varying thicknesses and widths was established to examine the influence of structural parameters on outlet temperature and heat gain under different flow rate conditions. The results indicate that at low flow rates, increasing the collector thickness significantly improves heat gain. However, at higher flow rates, the impact of collector thickness diminishes as convective heat transfer dominates. While increasing the flow rate enhances heat gain, marginal effects are observed beyond a certain flow rate, where further increases provide limited improvements. At flow velocities below 0.32 m/s, heat gain decreases with increasing channel width, a trend more evident at lower velocities. Conversely, at flow rates exceeding 0.32 m/s, heat gain initially rises with increasing channel width, then decreases and stabilizes. At the same flow rate, heat gain generally increases with wider flow paths, although at a flow velocity of 0.02 m/s, channel widths exceeding 34.8 mm show a declining trend. Notably, at a flow velocity of 0.92 m/s, increasing the channel width from 34.8 to 44.28 mm results in a substantial enhancement in the heat gain. These findings provide insights into optimizing Fresnel lens‐based solar collector designs by tailoring structural parameters and flow rates to maximize thermal performance.