Abstract
This study deals with the frequency characteristics of a glass-covered thermistor serving as transducer in a thermoanemometer and of a constant-resistance thermoanemometer with such probes.
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Abbreviations
- A:
-
average-in-time coefficient of heat transfer at the glass-fluid boundary, W/m2· °C
- Atot :
-
coefficient of steady-state heat transfer at a bare probe (a fictitious quantity introduced for gauging the heat transfer between a glass-covered probe with the moving fluid), W/m2· °C
- a :
-
thermal diffusivity of glass which insulated the heat sensitive element from the fluid, m2/sec
- CT :
-
total thermal capacity of transducer, W· sec/m2· °C
- H1 :
-
ratio of moduli in the expressions for current and resistance fluctuations in the transducer, dB
- H2 :
-
ratio of moduli in the expressions for heat transfer and resistance fluctuations in the transducer, dB
- I:
-
quiescent current through thermistor, A
- i:
-
transform of fluctuation current through thermistor, A
- Kv :
-
voltage gain of feedback amplifier
- k:
-
frequency parameter, 1/m
- l :
-
thickness of glass layer, m
- N′:
-
intrinsic time constant of thermistor, sec
- N:
-
time constant of constant-resistance thermoanemometer, sec
- M′:
-
intrinsic time constant of thermistor, sec
- M:
-
time constant of constant-resistance thermoanemometer, sec
- p:
-
complex variable in the Laplace transformation
- Q:
-
average-in-time thermal flux from the transducer, W/m2
- q:
-
transform of thermal flux fluctuations in the transducer, W/m2
- R:
-
average-in-time operating resistance of thermistor, ω
- R1 :
-
constant resistance in series with the thermistor in the thermoanemometer circuit, ω
- r:
-
transform of resistance fluctuations in the thermistor, ω
- S:
-
effective surface area of heat transfer from the transducer, m2
- TD :
-
steady-state temperature of hot film, °K
- T:
-
steady-state temperature of insulating glass layer, °K
- TL :
-
temperature of fluid, °K
- u:
-
velocity of oncoming fluid, m/sec
- WT :
-
relation between resistance fluctuations and current in the thermistor, in operator form
- y :
-
space coordinate in the mathematical model of the transducer, m
- α :
-
fluctuation component of heat transfer coefficient, W/m2· °C
- α ρ :
-
temperature coefficient of resistance, 1/°C
- λ:
-
thermal conductivity of insulating material, W/m· °C
- τ d :
-
transform of temperature fluctuations in the hot film, °K
- τ :
-
transform of temperature fluctuations in the insulating glass layer, °K
- ζ :
-
coefficient in the transfer function of a thermistor at high frequencies
Literature cited
B. J. Bellhouse and C. G. Rassmussen, DISA Information Note 6 (1968).
B. J. Bellhouse and D. L. Schultz, J. Fluid Mechan.,29, No. 2 (1967).
É. M. Lyubavin, V. G. Babakin, and V. G. Mishkevich, Trudy LKI [in Russian], Vol. 63 (1968).
O. Krogh Andersen, DISA Information Note 4 (1966).
É. M. Lyubavin, Experimental Ship Hydromechanics [in Russian], Izd. NTO Sudprom, Vol. 12 (1968).
A. G. Shashkov, Thermistors and Their Application [in Russian], Izd. Énergiya, Moscow (1967).
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 6, pp. 1042–1048, June, 1972.
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Lyubavin, É.M. Dynamic characteristics of thermoanemometers with glass-covered transducers. Journal of Engineering Physics 22, 722–727 (1972). https://doi.org/10.1007/BF00822979
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DOI: https://doi.org/10.1007/BF00822979