Distributed heat absorption in a solar chimney to enhance ventilation

Abstract

This study examined an innovative approach to enhancing solar chimney effect of using solar energy for building ventilation. Solar absorbing plates were inserted in a solar chimney to form a distributed heating flux among walls and insertions. Experiments using electrical heating to simulate the solar irradiation showed that adding two insertions increased the mass flow rate by 30%. The experimental data validated a computational fluid dynamics (CFD) model and two analytical models from the literature. Among these models, the plume model predicted the flow rate in the absence of insertions with reasonable accuracy, while the stratified model predicted the theoretical maximum flow rate instead of actual flow rate. The difference in flow rate between the two analytical models represents the potential for enhancement. The CFD simulations indicated that the insertion method could achieve approximately 70% of this potential. This represents a 57% increase in flow rate over the base case without insertions. This was achieved with 15 insertions. Adding more insertions was not advantageous because of the increase in friction. Insertions increase the uniformity of the heat distribution across the chimney channel and reduce the maximum temperature, resulting in a more uniform temperature distribution across the channel and, consequently, an increased buoyancy effect. However, two or three insertions are likely the most cost-effective in practice, as three insertions can realize majority (57%) of the potential enhancement. This study proves the concept of improving the efficiency of a solar chimney by adding transparent glazing insertions in the channel.