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Falling liquid film thickness measurement by an optical-electronic method (2000)

Zhang, J. T. ; Wang, B. X. ; Peng, X. F.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 71 (2000), S. 1883-1886

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: An optical-electronic method was developed for measurement of falling liquid film thicknesses. The method is based on the postulate that a sheet light beam passing tangentially through a vertical liquid film on a cylinder will be blocked by the falling liquid film. Hence, when the beam is much wider than the film, the output of a photodiode probe which is located on the opposite side of the cylinder from the light source will be reduced by an amount proportional to the film thickness. The shadow of the transient film shape will also appear on a screen behind the falling film. Therefore, the variation of the amplitude of the film waves can be measured from the output of the photodiode and the average film thickness can be measured from pictures of the shadow using computer aided image analysis. The average film thickness measured agrees well with commonly accepted empirical equations. The maximum relative deviation between the experimental and calculated results is 18.5% with a standard deviation of 4.34×10−2 mm. Compared with popular conductance parallel-wire probes, this method has the advantages of convenience, noninvasive, higher spatial and temporal resolution, smaller hysteresis and it does not disturb the model's surface. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1150557

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An advanced study of forced turbulent-flow film boiling for subcooled liquid with high velocity in a circular tube (1987)

Wang, B. -X. ; Peng, X. -F.

Springer

Heat and mass transfer 21 (1987), S. 139-144

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ISSN: 1432-1181

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Description / Table of Contents: Zusammenfassung Es wird über die Weiterentwicklung einer halbempirischen Theorie für den Wärmeübergang bei turbulentem Filmsieden in einer unterkühlten Flüssigkeit berichtet, die mit hoher Geschwindigkeit durch ein Rohr strömt. Auf theoretischem Wege wurde eine neue analytische Formulierung gefunden mit einem theoretisch vorhersagbaren Exponenten der Reynolds-Zahl und der für verschiedene Flüssigkeiten universell gültigen Konstanten 4/5. Zwischenzeitlich stellte es sich heraus, daß der Koeffizientk mitk′ berechnet werden kann und daß der für die Längsanströmung einer Platte gültige Koeffizientk erweitert bzw. angewandt werden kann auf die Strömung in einem Rohr. Die Analyse zeigt, daß der neue analytische Ausdruck mit früher veröffentlichten Ergebnissen [5] übereinstimmt.

Notes: Abstract A further advanced semi-empirical theory for the turbulent film boiling heat transfer of subcooled liquid flowing with high velocity in a circular tube is presented in this paper. A new analytical expression has been obtained theoretically and it is found that the exponent ofRe D in the expression can be predicted analytically with an universal constant value of 4/5 for different fluids. Meanwhile, it is revealed that the coefficientk is correlated withk′, and thatk determined for flowing along plate can be extended to the case for flowing in a circular tube. The analyses show that new analytical expression concides really with the results presented before [5].