Numerical investigation on the influence of geometric parameters on turbulent flow and thermal performance in the roof solar chimney

Abstract

The geometric parameters of solar chimneys directly affect the heat absorption area and channel cross-sectional area, significantly influencing economic costs and system performance. This study employs mathematical design calculation and numerical simulation methods to investigate the turbulent flow and thermal performance of roof solar chimneys under different Rayleigh numbers and different geometric parameters, including cavity gap-to-width ratios and channel cross-sectional areas. The configurations of ventilated rooms connected to solar chimneys significantly affect the velocity distribution, turbulent flow patterns, and vortex dynamics. Increasing the cavity gap and width reduces upward flow velocity and turbulent kinetic intensity. A higher cavity gap-to-width ratio enhances ventilation rates at lower costs. The discrepancies between the ventilation rates calculated by the mathematical design calculation and those obtained from numerical simulations are analyzed to optimize the geometric design methodology. Thermal efficiency declines with the expanding channel cross-sectional area. Disparities in ventilation and thermal performance intensify with a higher ratio of channel cross-sectional area to window opening area (A_R), indicating the increased system response to buoyancy forces. For A_R ≤ 0.25, increasing cavity gap and width similarly enhances ventilation rates. However, for A_R > 0.25, the enhancement effect of increasing cavity gap diminishes, while the increase in cavity width maintains a steady growth rate for ventilation. These findings provide a theoretical basis and practical guidance for solar chimney technologies and sustainable design research.