Evolution of contaminant distribution at steady airflow field with an arbitrary initial condition in ventilated space

Transient contaminant dispersion is of high importance to human comfort, health and safety. Lumped parameter model is usually applied to predict the evolution of contaminant dispersion, which, however, will not be effective when the contaminant distribution is not uniform. When airflow field is steady, the contaminant concentration distribution versus time will be determined by the concentration of supply air, contaminant source and initial concentration distribution in the ventilated space. An analytic expression of distributed contaminant concentration was developed using the accessibility of supply air (ASA), accessibility of contaminant source (ACS) and accessibility of initial condition (AIC). The ASA, ACS and AIC describe the contribution of supply air, contaminant source and initial condition to any point in ventilated space, and are determined by the airflow field if the contaminant sources and initial distribution are given. The analytic expression was validated by the tracer gas measurement in a test chamber. Based on the application of the expression in typical cases, the differences as well as connections between the analytic expression and lumped model were discussed. It is shown that the analytic expression is helpful for the understanding of the contaminant evolution process and may be used to obtain effective ventilation strategy for comfort and emergency.

[1]  Mats Sjöberg,et al.  The use of moments for assessing air quality in ventilated rooms , 1983 .

[2]  Povl Ole Fanger,et al.  Human requirements in future air-conditioned environments: a search for excellence , 2000 .

[3]  Arsen Krikor Melikov.  Local thermal discomfort due to draft and vertical temperature difference in rooms with displacement ventilation , 1989 .

[4]  Qingyan Chen,et al.  A zero-equation turbulence model for indoor airflow simulation , 1998 .

[5]  A. Melikov,et al.  Personalized ventilation: evaluation of different air terminal devices , 2002 .

[6]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[7]  Bin Zhao,et al.  Prediction of transient contaminant dispersion and ventilation performance using the concept of accessibility , 2004 .

[8]  S. Kato.  New Scales for Evaluating Ventilation Efficiency as Affected by Supply and Exhaust Opening Based on Spatial Distribution of Contaminant , 1992 .

[9]  Qingyan Chen,et al.  A critical review of displacement ventilation , 1998 .

[10]  P Wargocki,et al.  Perceived air quality, sick building syndrome (SBS) symptoms and productivity in an office with two different pollution loads. , 1999, Indoor air.

[11]  Xianting Li,et al.  Accessibility: A New Concept to Evaluate Ventilation Performance in a Finite Period of Time , 2004 .

[12]  J. Sundell,et al.  What we know, and don`t know about sick building syndrome , 1996 .

[13]  Xianting Li,et al.  A simplified system for indoor airflow simulation , 2003 .