NATURAL CONVECTION HEAT TRANSFER NEAR A VERTICAL WALL WITH FINITE CAPACITY

摘要

The convection heat transfer coefficients (CHTC) used in building simulations must correspond to phenomena which drive the heat transfer. Studies have been performed to include the effect of turbulence, heating and ventilation of the room, in CHTC correlations. In this paper, a system is developed to study the effect of the wall's thermal properties on the CHTC. The thermal excitation of the system is a variation of the temperature far from the wall. This excitation is realistic in buildings. It is also a boundary condition which can be easily reproduced in experiments. Analytical observations of the system show that the order of magnitude of time variations of the air temperature and velocity is large. This allows using a large time step for transient numerical simulations of the system. A numerical model is presented in the paper. CHTC calculation is performed for the simple case of a 2cm thick gypsum wall. It is found that, after a transient regime, the system is equivalent to a semi infinite vertical wall subjected to a constant heat flux.