The problem of safe operation of chimney systems in densely populated developments

Abstract

The phenomena of backdraft in chimneys due to meteorological conditions and geometrical parameters of the chimney head in the area of adjacent buildings are fundamentally considered. For the purpose of in-depth analysis of the backdraft phenomena, the meteorological parameters of atmospheric pressure and turbulence were calculated, and the wind speed was determined under operational and extreme conditions of chimney systems. Wind has a role to impact, and its consequences must be assessed to provide the required safety level of chimney systems. The technical conflict between National Norms and European Standards regarding the interpretation and definition of the "wind resistance zone" is considered separately, where the European approach has more mathematical approach. It is proposed to consider and analyse this issue according to more modern approach, using CFD computational fluid dynamic modelling and specialised software for thermal and aerodynamic calculations of chimneys, which makes it possible to assess the functional ability of a chimney, both in terms of design features and wind exposure. This approach has the advantage that the analysis is carried out locally, specifically for an individual chimney, which avoids random or template results. In other words, the interaction of the "atmosphere-chimney-room" system is considered. The ANSYS CFX-Post module analyses the formation of backdrafts for different wind speeds with the same geometric parameters of the chimney head, characterised by the speed changes of flue gas movement, static pressure, temperature field, and the formation of a flue gas plume in the atmosphere. The following factors have been identified in the modelling of the chimney functioning: the use of secondary air through the bypass hole, the temperature of the outside air is taken to calculate the minimum draft 288.15 K, the temperature of flue gases is 345.95 K. The obtained results of CFD computational modelling studies provide the motivation for the development of innovative and effective approaches to eliminate dangerous backdraft phenomena in chimneys.