A Study on Computational Analysis for Natural Convection in Tall Building – A Macroscopic Approach

Abstract

The development of convective heat transfer in buildings are found to be due to the movement of air with respect to the turbulence in air to the temperature. The heat transferred is observed in 3 levels - the roof exposed floor, the seventh floor and the lower floor of the 14 storey naturally ventilated tall building. This paper discusses the eulerian approach which is a macroscopic approach to understand the temperature in the building since the density stratification occurs in the indoor volume of the building. The volume averaged data is considered to be in eularian approach. The CFD analysis is used to artificially create the environment with the different temperatures and velocities. Heat transfer happens due to convection, hence the boundary conditions - initial outdoor temperature has been kept constant at 30°C and 23°C. The change in the outdoor temperature at the air velocities 10 m/sec at 12 noon were observed as 29.37°C, 29.49°C, 29.89°C at constant temperature 30 with respect to 1st floor, 7th floor and roof. Finally, it is noted that, as the air velocity increases, the outdoor temperature also increases. Conjugate heat transfer analysis is followed in CFD analysis to include the resistance of the exterior concrete wall to transfer the temperature to the control volume. K-omega model is used to resolve the turbulence and to analyse the interior domain with Boussinesq hypothesis in the momentum equation to include the effect of the density difference in heat transfer. It is observed the velocity helps to take the temperature from the exterior domain to the interior part of the building. Hence the results clearly indicate that when the outdoor temperature is higher and the outdoor velocity is also higher, the temperature which enters the indoor environment is also high.