Optimizing research on flat-plate solar collector based on field synergy theory

Flat-plate solar collectors are the leading product in the production of low-temperature hot water market, and are also one of the most widely used technologies for utilizing solar energy to generate low-temperature heat. In this study, a specific type of flat-plate collector optimized using field synergy theory was introduced, with the main change being the use of S-bend structure instead of traditional direct current channel. The study applied numerical simulation to analyze and evaluate the performance of the collector. The results showed that introducing an S-bend with a curvature radius of 90 mm can improve the efficiency of a single block collector by 0.1 %, reduce the temperature of the absorption plate by 0.33℃, and drive the angle between the velocity vector and temperature gradient ( β angle) close to zero. Compared with the relatively uniform vortex structure observed in the cavity of the straight tube collector, the S-bend structure generates more complex and irregular vortex patterns. It is worth noting that the introduction of S-bend produces a unique butterfly shaped temperature distribution on the glass surface. The changes that occur in the cavity area are driven by the temperature difference between the upper and lower plate surfaces, and these new phenomena induced by S-bending deserve further in-depth discussion. These findings emphasize the importance of continuous research to develop optimized designs, improve efficiency, and promote wider applications, and provide certain ideas and references for subsequent work. • Optimizing the flow channel of the flat plate collector using field synergy theory. • Improved the efficiency using S-bend flow channel with a 90 mm curvature radius. • The local strengthening occurs at the bend as the synergy angle β is close to 0. • A symmetric and relatively uniform vortex structure appears in the air space.