Dimensionless correlations of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions

Abstract

Indoor thermal stratification is a prevailing phenomenon in large-space buildings, which poses great pressure on their energy consumption and indoor built environment. This paper revealed the mechanism of indoor thermal stratification in a non-enclosed large-space building under heating and cooling conditions. It can be abstracted as a joint effect of the cold and hot air inflow (i.e., HVAC system and outdoor air infiltration), which are respectively depicted by two newly-defined Archimedes numbers (i.e., Arc and Arh). Then, we developed dimensionless correlations between the indoor thermal stratification (quantified by the dimensionless factor of the vertical temperature profile, CT) and the two streams of air inflow (quantified by Arc and Arh). For application, the dimensionless correlations can be coupled with our previously proposed theoretical model to accurately predict the air infiltration rate in a large-space building. Moreover, the dimensionless analysis reveals a principle of indoor vertical temperature profile control to minimize the buoyancy driving force of air infiltration in large-space buildings: Achieving a vertically uniform indoor thermal environment under heating condition and an effectively stratified indoor thermal environment under cooling condition. These findings help to provide practical guidelines to minimize buoyancy-driven air infiltration in large-space buildings.