Establishing and Verifying Minimum Variable-Air-Volume Airflow Rates

Abstract

For a given indoor source of contaminants, the resulting indoor concentration is largely a function of the building ventilation rates. Outside air taken into an occupied zone of a building cannot be assumed to be perfectly mixed with the indoor air, as this mixing is affected by several variables including the supply and return air distribution circuits, the rates of circulation, the outside airflow, the mode of operation (e.g. cooling or heating), and the presence of indoor partitions, equipment and occupants. The objective was the development and installation of appropriate measurements and control methods capable of determining the rates of delivery of outside, recirculated, filtered and cleaned return air. These constitute the ventilation air of a typical variable-air-volume air distribution system. This should result in specification of a measurement and analysis methodology, together with a description of instrumentation which will be capable of measuring minimum interior and exterior space cool ing and maintaining temperatures for typical cooling load scenarios and asso ciated space contaminant levels.