Effects of Exterior Thermal Transmission Modeling on Air Conditioning Heat Load Prediction of Large Space Buildings Using CFD

The effects of exterior thermal transmission modeling for walls and a roof on the airconditioning heat load prediction for a large space building were analyzed using a coupled simulation of convection based on CFD, radiation and conduction. Three cases were simulated: first, a simplified model using sol-air temperature (SAT) as outdoor boundary conditions; second, a rigorous model where both outdoor and indoor spaces were calculated simultaneously; and, third, using sol-air temperature modified by the results of the second case. Since the evaluation of convective and radiative heat transfer flux at the exterior roof surface was noticeably different between the first two cases, the flow fields, air temperature fields, and distributions of indoor surface temperature differed significantly. Thermal transmission load in the first case was estimated to be fourteen percent higher than in the second case. In the third case, indoor thermal characteristics and air conditioning heat load were found very similar to the corresponding figures to the second case.