TO-82-05-1 -- Air-Velocity Fluctuations in the Occupied Zone of Ventilated Spaces

Draft can be defined as an undesirable, local, convective cooling of the body. For many years, draft criteria have been based on Houghtons investigations from the 1930s in which ten male subjects were exposed to an air current with a constant (nonfluctuating) velocity directed toward the neck or ankles. In practice, however, velocity is not constant but fluctuating, and Pedersen has shown that it is the fluctuations that cause discomfort and result in people feeling draft at.far lower velocities than the constant velocities in Houghtens investigations. Pedersen exposed his subjects to well-defined periodic velocity fluctuations and found that frequency and amplitude also were important factors.

In practice, however, velocity fluctuations are not periodic but intermittent. Therefore, in order to establish realistic draft criteria, it is necessary to perform supplementary experiments, exposing subjects to intermittent velocity fluctuations as they occur in practice. In order to do this, it is first essential to identify the velocity fluctuations that can actually occur. The purpose of the present project is to identify these velocity fluctuations through measurements in several typically ventilated spaces.

Citation: ASHRAE Transactions, Volume 88, Part 2, Toronto, Canada



Product Code(s): D-TO-82-05-1