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Advanced Course in Measurement Techniques in Heat and MassTransfer
1983, Dubrovnik, Yugoslavia

DOI: 10.1615/ICHMT.1985.AdvCourseMeasTechHeatMassTransf


ISBN Print: 978-0-89116-381-7

The Determination of Convective Heat Transfer by the Measurement of Mass Transfer Using a New Optical Technique

pages 155-166
DOI: 10.1615/ICHMT.1985.AdvCourseMeasTechHeatMassTransf.130
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ABSTRAKT

In the past a number of mass transfer techniques have been devised for the purpose of determining heat transfer coefficients by making use of the heat transfer - mass transfer analogy. Examples of these are the sublimation [1] and electrochemical [2] methods. In most applications there are considerable benefits in the reduction of equipment complexity, costs and time taken for the measurements compared with direct measurements of heat transfer coefficients. This paper describes a new technique, both simple and fast, using the measurement of liquid evaporation rates to determine single phase convective transfer rates from surfaces of interest [3]. The technique is based on the observation that the light transmission and reflection coefficients of certain absorbent papers are directly proportional, within limits, to their liquid content. Thus, measurement of the optical coefficients of such a paper attached to a surface of interest during a convective drying process allows a measure of the evaporation, or mass transfer rate of the liquid from that surface. The mass transfer technique may be calibrated in a standard geometry using the heat transfer - mass transfer analogy. In order to do this, mass transfer measurements are made in situations where the heat transfer rates are well documented.
A verification programme has been undertaken in our laboratory in which measured variations in mass transfer rates on a wide variety of geometries have been compared with published heat transfer data. These have included a cylinder in cross-flow and a flat plate with and without a non-transferring length. Good agreement has been obtained between measurements using the new mass transfer technique and published data.

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