Influence of architectural features of buildings on heat losses from their facades

In the heat balance of buildings, the main heat loss occurs through enclosing structures. Determining the heat transfer coefficients on the exterior facades of buildings is not an easy procedure, as they depend on a wide range of parameters: wind speed in the surface atmosphere, wind direction relative to the orientation of facades, surface orientation relative to wind, surface angle relative to the ground plane, type terrain, the impact of adjacent buildings, surface texture, surface and air temperature differences, surface size and aspect ratio, etc. The paper presents the results of a numerical study of heat transfer from the outer surfaces of separately located structures in the surface layer of the atmosphere. Schematic models of the building have the same heat transfer surface area, but different heights and lengths. CFD-modeling of heat transfer of buildings in the wind flow in a three-dimensional setting allowed to establish some features of heat transfer of enclosing structures depending on the height of the building and the characteristics of the wind flow. In particular, it is shown that the average surface values of heat flux density increase with increasing building height. The results of the calculation of the average heat flux density on the surface of buildings indicate its dependence on the height of this building. This dependence is observed only for houses with a height of less than 30 m. For taller houses, this dependence is insignificant. The local values of heat transfer coefficients on the windward and leeward facades of the building obtained as a result of modeling indicate incorrect application of heat transfer coefficient values αк = 23 W / (m2 ∙ K) for construction practice for external surfaces of enclosing structures. For windward facades, a polynomial model for the heat transfer coefficient is more suitable, and for leeward ones, the Frank formula for αk.