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Physical causes for draft - some new findings

: Mayer, E.

American Society of Heating, Refrigerating and Air Conditioning Engineers. Transactions 93 (1987), Nr.1, S.540-548 : Abb.,Lit.
ISSN: 0891-8295
Fraunhofer IBP ()

This paper deals with some laboratory and field researches to elucidate the physical causes for draft. By the use of some new instruments, the correlation between air velocity and the convective surface-heat-transfer coefficient of a heated artificial head was measured. It could be shown that this coefficient results directly from the thickness of the temperature boundary layer. From these preliminary measurements it is concluded that there is a parabolic correlation between the product of mean air velocity and turbulence degree on the one side and the coefficient on the other. Using the dry heat balance of a heated body and the inclination of the human surface temperature for feeling cold discomfort, a simplified comfort equation reveals the mutual relation of the coefficient and air temperature with respect to draft. These statements are in accordance with the results of some fields measurements of air velocities and inquiries in different ventilated buildings. (IBP)