Enhancing Convective Heat Loss Reduction in Flat-Plate Solar Collectors by Optimal Integration of Transparent Partitions in the Air Gap

Abstract

In a three-dimensional study, numerical simulations were carried out to quantify the natural convection heat transfer occurring within the air gap between the absorber and the glass cover of a thermal solar collector. The study explored various combinations of partition placement and spacing: partitions glued under the glass cover (PGG model), partitions glued at absorber (PGA model), and partitions suspended between the absorber plate and glass cover (PS model). Simulations were conducted with two partition spacing configurations of 0.14 m and 0.1 m. The primary aim was to identify cost-effective methods for reducing heat losses due to natural convection in the air gap while achieving higher absorption temperatures. The comprehensive numerical analysis included assessing flow patterns, temperature distribution, and heat transfer coefficients for each configuration. The findings revealed that using a partition spacing of 1.4 m resulted in complex and unstable outcomes, making comparisons between models difficult. However, decreasing the partition spacing to 0.1 m enhanced convective resistance, fostering temperature stability within the cavity. Nevertheless, the PGA model transitioned from unstable to stable flow, resulting in a notable temperature rise, making it the most effective configuration for minimizing thermal losses in the collector's frontal section. Additionally, the PGG model configuration exhibited promising performance. Meanwhile, the PS model experienced quasi-periodic cooling due to undulating flow patterns. This study stresses the importance of balancing uniform heating and stable flow in collector systems, highlighting the need for thorough 3D analyses. Strategic adjustments to partition placement and spacing can significantly improve solar collector design.