The Influence of Temperature, Humidity and Changing Conditions on the Measurement of Mass Transfer Coefficients in Indoor Air
The concentration of reactive indoor pollutants is strongly influenced by the rate at which these species are transported to and from surfaces such as walls and carpet. To parameterize this transport, several methods have recently been developed which quantify the instantaneous and time-averaged transport-limited deposition velocity, vt and v̄t, respectively. These include 1) the DEVS sensor that quantifies vt using a microbalance to continuously measure the evaporation rate of octadecane into a room and 2) the DEVO filter that evaluates v̄t, by quantifying the rate at which ozone deposits on a filter surface. In this investigation, we evaluate how changing conditions, temperature and humidity influence the results from these measurement methods. We find that, if v t changes significantly (e.g. vt, is sinusoidal) the value of v̄t, evaluated by DEVO may deviate from the actual value by nearly a factor of 2. The DEVS device does not suffer from this effect because it measures vt instantaneously. Very low indoor temperatures and humidities may also reduce the apparent value of v̄t derived from DEVO experiments. High temperatures (e.g. >30 C) appears to soften the octadecane coating on the DEVS microbalance. This results in unsteady and difficult to interpret data. Humidity changes appear to change the absolute frequency of the DEVS microbalance, but do not affect the measurement of v t.
G. Morrison et al., "The Influence of Temperature, Humidity and Changing Conditions on the Measurement of Mass Transfer Coefficients in Indoor Air," Proceedings of the 2004 Air and Waste Management Association's Annual Conference and Exhibition, Air and Waste Management Association, Jan 2004.
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Indoor Air; Indoor Air Models; Mass Transfer Coefficient; Microbalance; Pollutant Transport
Article - Conference proceedings
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