Measurement of heat transfer coefficients in tubes by temperature oscillation analysis

Authors

  • Prof. Dr.-Ing. Wilfried Roetzel

    1. Institut Für Thermodynamik, Universität der Bundeswehr Hamburg, Postfach 70 08 22, Holstenhofweg 85, D-2000 Hamburg 70
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  • Paper presented at the “Jahrestreffen der Verfahrens-Ingenieure”, Hannover, September 21 to 23, 1988.

Abstract

An experimental technique and evaluation method is described for the determination of local heat transfer coefficients in tubes or other ducts. By means of a rotary mixing valve, cold and warm fluid flows are mixed in order to generate an arbitrarily shaped but periodically oscillating inlet temperature profile at the test tube. The propagation of the fundamental harmonic oscillation from the fluid to the outer surface of the tube wall is calculated analytically. Comparison of fluid and wall oscillations yields the heat transfer coefficient to be measured. The inaccurate measurement of fluid bulk temperature in the centre of the cross-section is compensated by an additional correction. Experiments were carried out with turbulent water flow through a copper tube. Measured heat transfer coefficients were compared to values calculated using Hausen's equation and good agreement was obtained.

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