HEAT TRANSFER AND FLUID FLOW IN A WATER-FILLED GLASS LOUVER SUBJECT TO SOLAR IRRADIATION

Numerical studies of fluid flow and heat transfer in a water-filled prismatic glass louver have been carried out to investigate the efficiency of solar thermal energy harvest via the proposed louver that could be deployed in buildings to improve natural lighting to save electrical bills as well as to harvest and store solar energy transformed into thermal energy. One surface of the prismatic louver is adjusted to face the direct solar irradiation. Both direct and diffuse irradiations are incorporated in different air mass models. The distribution of absorbed solar radiation in the louver is precalculated via the Monte Carlo method and input as a heating source. The finite element method based on COMSOL is adopted to simulate the three-dimensional steady-state fluid flow and conjugate heat transfer in the triangular water channel. Temperature-dependence of water property is considered. The prismatic louver is surrounded by ambient air. Emphasis is placed on investigating the effects of flow rate and solar irradiation conditions on water temperature rise and energy harvest. It is found that the outlet water temperature is a strong function of the water flow rate. Most of the absorbed solar energy in the glass can be converted into stored thermal energy in the water through convective heat transfer. The water pumping power consumed is negligible as compared to the energy harvested. When the louver is adjusted to face the direct solar irradiation and the water flow velocity is 0.1 m/s, the overall utilization efficiency of the louver reaches 89.2, 90.3, 89.1, and 87.9% for AM1.0, AM1.5, AM2.0, and AM3.0, respectively.