Natural Convection Heat Flow according to Inclination Angle of Air Layer with Wall Temperature Difference

Purpose: The smart façade system which is under development consists of a curtain wall unit, a heat exchanger unit, and a heat collection unit with a heat storage and circulation. Using the effective thermal conductivity of the air layer in ISO15099 is insufficient to predict the heat transfer of air cavity in the smart façade system. In order to improve the prediction, a heat and flow analysis code instead of effective thermal conductivity is employed. The changes in heat transfer rate and flow characteristics according to the inclination of the device were identified. Method: We developed a thermal flow analysis code to calculate and analysis easily the air layer in the smart façade system. The code employed the Boussinesq approximation for buoyancy, SIMPLE method for imcompressible flow, and unstructred grid system. Result: Calculations were performed for cases where the longitudinal (x-axis) and the width (y-axis) directions were tilted. There was little change in heat flow in the y-axis inclining and there was relatively no significant changes in the x-axis below 10 degrees. However, when the inclined angle exceeded -50 degrees, there is a change in flow characteristics and the heat exchange is significant. Based on the results of the analysis, when installing the smart envelope, it must be within 10 degrees to sustain the designed performance.