Response behaviour of hot wires and films to flows of different gases

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 behaviour is described. A previously unreported hysteresis in the heat transfer behaviour for Re ≈ 44 has been characterized and attributed to the presence or absence of eddy shedding from the heated cylinder.

On the effects of fluid temperature on hot wire characteristics

“…In other words, the local heat transfer rate q,. This is essentially extending the route of Pitts and McCaffrey (1986) to account for the correction due to the dependence of the Nusselt number on the temperature difference. between the wire and the ambient fluid alone, an observation supported through Fig.…”

A survey of electronic measurement needs below 10 MHz

“…It was discovered that none of these correlations were successful in correlating an extensive series of calibrations performed in ten different gases [11,12]. The most widely quoted correlation for different gases utilized a correction based on the Prandtl number (Pr) to correct for variations in molecular properties [13][14][15] .…”

“…Extensive analysis [11,12] of the data showed that it is necessary to consider the temperature dependence of the molecular properties in order to obtain accurate correlations. Other heat transfer characteristics such as thermal slip and surface accommodation were also investigated during the course of this study [11,12].…”

“…Other heat transfer characteristics such as thermal slip and surface accommodation were also investigated during the course of this study [11,12].…”

Mixing in variable density, isothermal turbulent flow and implications for chemically reacting turbulent flows

“…The manuscripts which resulted from this work [10,11,12] are not only significant for their importance to researchers who wish to utilize HWA in different gases, but are also important for the much wider field of heat transfer.…”