- Author
-
Pitts, W. M.
|
McCaffrey, B. J.
- Title
- Response Behavior of Hot-Wires and Films to Flows of Different Gases.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Journal
-
Journal of Fluid Mechanics,
Vol. 169,
465-512,
1986
- Sponsor
- Air Force Systems Command, Washington, DC
- Report
-
NBSIR 85-3203,
July 1985,
123 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
accommodation coefficients
|
convection
|
cylindrical bodies
|
heat transfer
|
hot wire anemometry
|
molecular effects
|
reynolds number
|
vortex shedding
|
prandtl number
- Abstract
- Measurements of the voltage output for hot-wire and film anemometers placed in flows of nine different gases have been made as a function of flow velocity. It has been possible to correlate the measurements quite accurately by treating the data in terms of suitably defined Reynolds and Nusselt numbers. In order to obtain these correlations it has been necessary to consider and correct for the effects of probe end conduction losses, temperature dependencies of gas molecular properties, flow slip at the probe surfaces, and gas accommodation. with the exception of the results for helium (for which accommodation effects are strong), the most important correction is shown to be that for the different temperature dependencies of the gas molecular properties. This finding is contrasted with previous studies which have assumed that the largest effect among different gases was due to variations in the Prandtl number. The importance of the nature of the flow over the cylindrical devices to the heat transfer behavior is described. A previously unreported hysteresis in the heat transfer behavior for Re~44 has been characterized and attributed to the presence or absence of eddy shedding from the heated cylinder.