Transport characteristics of dense gaseous contaminants in a large space in the presence of obstacles

Abstract

In industrial buildings, large cross-sections and obstacles lead to relatively low velocity in the large space except in the vicinity of air supply jets. The dimensionless number that represents the dense gas transport characteristics is revised to effectively represent the indoor gaseous contaminant transport mode in the large space. Based on the computational fluid dynamics (CFD) model validated by experimental data, a group of orthogonal design simulations have been conducted to examine the ranges of the dimensionless number for each transport mode. The indoor gaseous transport modes in the vicinity of the source are divided into passive, transitional, and active transport modes, featured by the magnitude of the revised dimensionless number θ. When θ exceeds 29.38, the transport is in active mode, and when θ is less than 13.61, the transport is in passive mode. The critical value of θ from the passive to the transitional stage is in the range of 13.61–19.94. The critical value of θ from the transitional to the active stage is in the range of 20.68–29.38. When the gaseous contaminant is in active transport mode, the contaminants tend to move downward in the vicinity of the source, the dimensionless concentration distribution shows vertical stratification in the overall space, and the overall ventilation efficiency is notably higher than the non-active transport modes.