Heatmetry by Sergey Z. Sapozhnikov & Vladimir Yu. Mityakov & Andrey V. Mityakov

Author:Sergey Z. Sapozhnikov & Vladimir Yu. Mityakov & Andrey V. Mityakov
Language: eng
Format: epub
ISBN: 9783030408541
Publisher: Springer International Publishing

The processing of our experimental data has yielded the similarity equation

Comparison shows that comparable temperatures and Reynolds numbers, the average heat transfer coefficient is lower by 10...20% at the isothermal cylinder’s surface than at the surface of the cylinder with constant (on average over the surface) heat flux. This is consistent, in particular, with the conclusions of the known studies [19].

There is an increasingly high demand for computations’s verification in modern numerical experiments [20–22]. It is especially important to obtain experimental data on the velocity characteristics, temperature and heat flux in turbulent flows. Experience of numerical experiments shows that it is impossible to use modern turbulence models without verification at , and the confidence for numerical simulation data is significantly reduced at smaller Re values.

Methods of hot-wire anemometry [10] have found wide use as a verification instrument and are successful for recording temperature fluctuations near the surface. These data are considered to be the most reliable, since the wire diameter of a hot-wire anemometer is about 10 m and the response time is equal to 10 s.

To examine the correlation between heat transfer coefficient and velocity fluctuations, a hot-wire anemometer was placed at a distance of 1.5 mm from the GHFS and at the same angle . Its signals were recorded simultaneously with those for heat flux fluctuations. Although the signal from the hot-wire anemometer was affected by temperature fluctuations of air, this effect appeared to be insignificant because of high temperature of the wire.

At first, it is interesting to compare the fluctuation characteristics measured by the hot-wire anemometer and the GHFS. Secondly, it is important to specifically use the heat flux fluctuations for verification of numerical experiments (since the GHFS’s response time is less than that of the best modern hot-wire anemometers by several magnitude).

The equipment described in Sect. 2.​4 allows to convert analog GHFS signal to digital one with a frequency up to 30 kHz. All measurements were taken times with a frequency of 2 kHz. Experimental data were processed using the criterion for the heat flux fluctuation’s intensity [23, 24]

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