Abstract
External, mainly solar, load can constitute up to 80% of the energy consumed by Heating, Ventilating and Air-Conditioning (HVAC) systems in buildings. Proportional attention is rarely given by designers to the optimum positioning or orientation of a building with respect to the sun so as to achieve minimal solar load. Even less attention has been given to groups of buildings located within a building complex for potential mutual shading. The general practice is to place them in a row or square formation. In this work, the optimum positioning of three high-rise buildings in close proximity to each other is investigated numerically with respect to solar radiation and potential mutual shading. Specifically, the effect of the relative locations of the buildings is tested with respect to solar radiation direction for a typical summer day in Kuwait City, Kuwait. The transient three-dimensional problem is solved using the Solar Load Model of the Fluent (TM) finite volume computational fluid dynamics code. The solar load model calculates radiation effects from the sun's rays that enter a computational domain transiently based on the selected location. Specifically, the ray tracing approach in the model applies solar loads as heat sources in the energy equations. The solar calculator utility is used to construct the sun's location in the sky for the selected time-of-day, date, and position. As the circle containing the three buildings is rotated, the energy absorbed by the shaded one or two buildings changes significantly. Combined with air flow around the buildings, the interaction between convection and radiation heat transfer rates to the buildings can vary greatly. This variation should be taken into account when sizing HVAC equipment for the individual building. Typical TMY (Typical Meteorological Year) data for Kuwait City, Kuwait, is used to obtain boundary conditions for air velocity and temperature. Mass, momentum and energy conservation equations are solved in conjunction with the radiative Solar Load equations to obtain the combined effect. Results show that there exists an optimum orientation for the group for the selected locale and that the reduction in solar load for the optimum orientation for the group of three buildings and that the orientation effect on the total HVAC energy requirement (represented by the cooling load) is significant. The difference between the best and worst orientations was about 6%. Convection, even though non-negligible, has a somewhat smaller effect on the total heat transfer and thus cooling load. Ongoing work examines the effect of the sensitivity of energy savings to wind direction and convection heat transfer, by altering strength and direction of the breeze.