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Journal of engineering physics

, Volume 22, Issue 6, pp 717–721 | Cite as

Effect of a protective coating on the frequency characteristics of film transducers in thermoanemometers

  • I. L. Povkh
  • D. F. Shtopko
Article
  • 13 Downloads

Abstract

An expression is derived for the thermal characteristic impedance. Equations are obtained for calculating the amplitude-frequency and the phase-frequency characteristics of planarfilm transducers with protective coating.

Keywords

Statistical Physic Frequency Characteristic Protective Coating Characteristic Impedance Film Transducer 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notation

ζ

time constant

ω

radian frequency

f

frequency

T

temperature

Q

thermal flux

k

thermal conductivity

α

heat transfer coefficient

a

thermal diffusivity in solid state

λT

thermal wavelength

l

length of film on sensing element, normal to the direction of the stream

d

width of film on sensing element, parallel to the direction of the stream

lb

thickness of substrate

μg

kinematic viscosity of fluid

Zt

thermal characteristic impedance

RT

thermal characteristic resistance

ϕ

phase-shift angle

Tj

temperature of hot film (°C)

Tc

temperature of protective coating, at distanceLc from the film

Tb

temperature of substrate, at distance lb from the film

lcT, lcT/2, etc.

thickness of protective coating, equal to thermal wavelength, equal to half the thermal wavelength, etc.

Qfc

thermal flux from hot film to protective coating

Qfb

thermal flux from hot film to substrate

Qgc

heat transferred from protective coating to fluid stream

Z′

characteristic impedance of transient heat transfer from film to coating (°C·sec/J)

Z′

characteristic impedance of transient heat transfer from film to substrate (°C·sec/J)

W

relative sensitivity, dB

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Literature cited

  1. 1.
    S. C. Ling, “Measurement of flow characteristics by the hot-film technique,” Ph. D. Thesis, Iowa State University (1955).Google Scholar
  2. 2.
    I. Kidron, “Application of modulated electromagnetic waves for measurement of the frequency response of heat-transfer transducers,” DISI Information Note 4 (December, 1966).Google Scholar
  3. 3.
    R. A. Armistead, Jr. and J. J. Keves, Jr., “Hot-film sensor for the study of boundary-layer turbulence phenomena,” Rev. Sci. Instrum.,39, No. 1 (1968).Google Scholar
  4. 4.
    P. E. Nielsen and C. G. Rasmussen, “Measurement of amplitude and phase characteristics,” DISI Information Note 4 (1966).Google Scholar
  5. 5.
    B. J. Bellhouse and C. G. Rasmussen, “Low-frequency characteristics of hot-film anemometers,” DISI Information Note 6 (1968).Google Scholar
  6. 6.
    I. O. Khintse, Turbulence [in Russian], Fizmatgiz, Moscow (1963).Google Scholar
  7. 7.
    H. S. Carslaw and J. C. Jeager, Conduction of Heat in Solids, Oxford Press (1948).Google Scholar

Copyright information

© Consultants Bureau 1974

Authors and Affiliations

  • I. L. Povkh
    • 1
  • D. F. Shtopko
    • 1
  1. 1.Donetsk State UniversityUSSR

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