The Influence of Solar and Longwave Radiations on the Airflow in Building Spaces B. FARHANIEH S. SATTARI Department of Mechanical Engineering - Division of Energy Conversion Sharif University of Technology Tehran, P.O. Box: 11365-9567 IRAN bifa@sharif.edu Abstract: - The airflow and thermal gain in building spaces are influenced by solar (shortwave) radiation, the environmental longwave radiation and the radiation of the internal walls of the building considered as gray bodies at different temperatures. In this paper an integrated model includes the influence of the above radiations is developed for simulation of the airflow in building spaces. For this purpose, two modeling approaches are used, the zonal network method for modelling of the building segments and the Computational Fluid Dynamics (CFD) solution for modelling of the inner airflow. A synchronize solution process is also used for the building and CFD equation-sets. Key-Words: Energy Simulation - Integrated Modelling - CFD - Radiation - Solar – Longwave 1 Introduction The building sector plays a significant role in global energy consumption. Since energy production is extensively based on using fossil fuels, the building sector has a clear connection to environmental issues. These environmental and economical reasons increase the pressure to design and build better residential and commercial buildings in the future. To this end, more research is needed to better understand the behavior of buildings, and particularly to quantify the interaction between indoor air quality and energy consumption. Energy simulation and CFD provide important and complementary information for building energy and indoor environment design. In recent years the synchronized solution of the existent building simulation and CFD programs to achieve more accurate results is increased. Bartak et al. [1], Morrison [2, 3] and Hensen [4] have investigated on the integrated building and airflow simulations. A coupled energy simulation and CFD simulation can eliminate many assumptions employed in the separate energy simulation and CFD computations and thus provide more accurate results [5]. The gain of energy from the sun has major effects on thermal behavior of airflow in the building. Many researchers have investigated to calculate the gain of solar radiation which receives at earth’s surface [6-8]. The total radiation incident on an exposed surface with arbitrary inclination and azimuth angles has three components, direct solar beam, ground reflected and sky diffuse. In order to calculate of these values some data on local solar time, solar position and climate modeling are necessary. Bring and et al. [9] have gathered some different models for building indoor climate and energy simulation. Atheanassouli and Massouros [10] obtained an explicit relation for the thermal flux from the environment to an opaque external wall. Hong et al. [11] have reviewed the state-of-the-art on the development and application of computer-aided building simulation. They have provided also some information sources to the building simulation community. In this paper an integrated model is developed for simulation of the airflow in building spaces. The influence of the solar and longwave radiations on airflow is investigated using this developed model. For this purpose a 2D building space surrounded with multi-layer walls and a window is considered (Fig.1). Since different numerical methods are employed in walls and CFD modelings, we employed an iterative procedure in order to achieve the convergence and stability in corresponding solution. 2 Airflow (CFD) Modelling CFD has the potential to predict the details of airflow and temperature fields within particular zone by solving the flow’s governing equations. In the last two decades, CFD has been successfully applied to the indoor airflow analysis [5]. Proceedings of the 3rd IASME/WSEAS Int. Conf. on HEAT TRANSFER, THERMAL ENGINEERING AND ENVIRONMENT, Corfu, Greece, August 20-22, 2005 (pp214-220)