NATURAL CONVECTION IN AN ASYMMETRICALLY-HEATED OPEN-ENDED CHANNEL: A THREE-DIMENSIONAL COMPUTATIONAL STUDY

Buoyancy-driven flows in an asymmetrically heated open-ended channel which occur in facade and roof building-integrated photovoltaic systems were investigated using large-eddy simulation. The channel inclination angle was varied from 300 to 90 to the horizontal, whereas the channel height-to-width aspect ratio remained at 20. In each case, a uniform heat flux was applied along the top wall whereas the bottom wall was assumed to be adiabatic. It is shown that typical dynamics of large-scale structures in the flow and thermal fields of natural convection in the channels are successfully modeled numerically by the use of LES. The effects of varying the inclination angle on the heat transfer in the channel are explored by examining the mean flow fields and in addition, the effects of radiation have been considered. Both experimental and numerical results show that open-ended channels with low inclination angles are characterized by a low chimney effect which leads to a decreased flow rate and a delay in transition to turbulence, thereby decreasing the heat transfer coefficient and leading to higher temperatures on the heated wall. A correlation describing the local Nusselt number in the channel is also developed in order to characterize the global heat transfer behavior.