Response Coefficient: A New Concept to Evaluate Ventilation Performance with ''Pulse'' Boundary Conditions

Abstract

Releasing a ''pulse'' tracer contaminant at a given point, either in the air supply or in the indoor space, and monitoring its transient distribution in a steady-state flow field, allows the performance of the air distribution to be evaluated. Two nondimensional indices have been defined, Response Coefficient to Supply Air (RCSA) and Response Coefficient to Contaminant Source (RCCS), to characterize spatial and temporal distribution under different air distribution patterns. To demonstrate their characteristics a 2D ventilated room was numerically analyzed. The results show that RCSA at each location (except the inlet) and RCCS at each location in the room (except the contaminant source) initially increase, then decrease, and become zero when time is long enough; RCSA ``records'' the characteristics of the flow field. There will be only one maximum response coefficient value under a piston flow field, while under a flow field with recirculation, there will be several, which may be used to evaluate the airflow pattern; RCCS contains information on the contaminant source position under a specific flow field. The relative positions of the contaminant source and the monitoring points determine response curves, which may be used to judge the position of a contaminant source; accumulation of RCSA and RCCS will become constant when time is long enough. The accumulation value of RCSA at any location indoors is 1, while accumulation values of RCCS at different locations differ from each other, but are determined by the relative position of the contaminant source and the location.

Keywords

indoor air quality (IAQ)ventilation efficiency passive contaminant air distribution evaluation index

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