tracer gas measurement

A VAV (Variable Air Volume) air conditioning system without reheat of the air supplied is generally regarded as energy efficient. Re-heat can be avoided when induction VAV controllers are used instead of conventional controllers since primary airflow can be reduced to about 10−20% of its nominal value without a draught risk.

For the zoning room air conditioning strategy to work properly, it is essential that the supply air is delivered in such a way that it does not block the plumes' way from the lower zone to the upper. The parameter measuring the fulfilment of this condition is the plume penetration. This kind of parameter could be measured by releasing tracer gas into the heat source and measuring the response elsewhere. This was done in our research also, but the tracer gas experiment was supplemented by an alternative method, utilizing small helium-filled soap bubbles instead of gas.

Different measurement procedures are available for the experimental assessment of air change rates inside ventilated enclosures. These mainly consist of tracer gas techniques and can usually be applied to steady-state or moderately transient conditions and when a continuous mixing of the indoor air is assured throughout the test. However, due to the relatively slow response of the gas analysers, none of these procedures can usually be applied to fast transient phenomena that last 15 minutes or less.

It is difficult to evaluate the effect of cross ventilation quantitatively, because the indoor environment under cross ventilation is uneven and changes with the outside conditions. In this paper, the decay process of tracer gas is measured in uneven space under cross ventilation, and the property of spatial unevenness is examined by the concentration decay and velocity distribution.

Methods to measure airflow rates using tracer gas in single air handling units are well known.However, in some buildings, in particular in Singapore, rooms are often ventilated with two ormore units. An adapted methodology that should be used to measure not only the airflow ratesprovided by each unit, but also to determine the inter-units airflow rates and the globalventilation efficiency is presented.

The airtightness of 82 passive solar homes located throughout the United States was studied using tracer gas measurements of air infiltration and pressurization testing. The air infiltration measurements employed the tracer gas decay technique in a low-cost mode employing air sample bags and off-site infiltration determination. The infiltration rates measured under natural conditions ranged from about 0.05 to almost 2 air changes per hour (ACH). The pressurization test results ranged from 1 to more than 30 ACH at 50 Pa, with an average of about 10 ACH.