Simplified Model of Contaminant Dispersion in Rooms Conditioned by Chilled-Ceiling Displacement Ventilation System

Abstract

The aim of this paper is to develop and experimentally validate a simplified model to predict carbon dioxide transport and distribution in rooms conditioned by chilled-ceiling displacement ventilation (CC/DV) system for known supply thermal and flow conditions and chilled-ceiling temperature. The transport model of carbon dioxide considers upward convective flow by the rising thermal wall and source plumes, the CO₂ lateral diffusion into plume-adjacent air layers, and vertical CO₂ diffusion in air inside and outside the plumes.

Experiments were performed for different supply air CO₂ concentrations, supply air flow rates, and strengths of heat sources. Experimental measurements of the vertical profile of air temperature, and carbon dioxide concentration compared well with values calculated by the model.

The indoor air quality is assessed based on levels of carbon dioxide concentration in the radiant-cooled space. The model can be put to practical use in finding the maximum acceptable fraction of return air to be mixed with the supply while the air quality in the breathing zone remains acceptable.