Effects of aspect ratio and inlet wind velocity on thermal characteristics of Trombe wall channel under different ventilation strategies: An indoor experiment

Abstract

Due to the air flow channel's “C”-shaped structure with asymmetric thermal boundary conditions, the structural and operating parameters have unique intrinsic impacts on overall performance of Trombe wall. In order to match the engineering practice well, under laboratory conditions, an experimental research platform with adjustable channel width and fans was established to reveal the effects of aspect ratio and inlet wind velocity on thermal characteristics of air flow channel under different ventilation strategies. The results show that under natural ventilation strategy, the air flow channel's thermal performance has an extremum when the aspect ratio is about 0.05. Under forced ventilation strategy, with the growth of inlet wind velocity, the comprehensive average convective heat transfer coefficient rises while thermal efficiency shows different trends under various heat fluxes and reaches the maximum when heat flux is greater than 360 W/m2 and inlet wind velocity is 0.6 m/s. A larger aspect ratio leads to a lower comprehensive convective heat transfer coefficient and a smaller thermal efficiency. Compared with the natural ventilation strategy, except for the air temperature rise, the air flow channel's thermal performance is improved to a certain extent under forced ventilation strategy. The improvement of thermal efficiency is particularly significant when the heat flux is small, indicating that forced ventilation strategy has high application potential in areas with low solar radiation intensity. Finally, the Nusselt number correlations reflecting comprehensive average convective heat transfer performance of Trombe wall channel under two ventilation strategies were obtained for engineering design and performance evaluation of Trombe wall.