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Description of  Measurement techniques in heat transfer

Foreword Textbooks on heat transfer u'sually concentrate on the analysis of heat transfer processes and either devote only a small amount of space to the discussion of measurement techniques or exclude this subject completely. On the other hand, special problems are encountered in heat transfer measurements and experience is required when accurate results are desired. course on "Measurement Techniques in Heat Transfer" was held in June, 1968, at the University of Minnesota, organized by its Extension Division with lectures presented by the staff of the Thermodynamics and Heat Transfer Division of the School of Mechanical and Aerospace Engineering at the University of Minnesota, and by speakers from other organizations who are specialists in the subjects of their lectures. Papers based on these lectures have been collected at the suggestion of the Advisory Group for Aerospace Research and Development and form the content of this book. For this reason, a special summer Temperature measurements in a heat transfer situation should not be considered without a check on possible systematic errors caused by conduction, radiation or, in an unsteady situation, heat capacity effects. Section 1 discusses these errors and the means to calculate them. Section 2 discusses resistance thermometers, thermocouples, and pyrometers, their calibration and use for temperature measurements. G. W. Burns of the Heat Division, Institute of Basic Standards, National Bureau of Standards. requires special techniques for temperature measurements which are discussed in Section 3. Optical techniques have the advantage that they do not disturb the temperature field in which the measurements are to be made. in index of refraction are reviewed in Section 4. scopy can be used as a diagnostic tool and this technique is discussed in Section 5. A very useful tool for the measurement of the enthalpy in a high temperature gas stream is the enthalpy probe discussed in Section 6. The measurement of heat flux poses special difficulties as illustrated by the techniques described in Section 7. one hand, and mass transfer, on the other, makes it possible to obtain information on a heat transfer process by measurements in an analagous mass transfer situation. This offers an advantage where mass transfer experiments are simpler to perform or where clearly defined boundary conditions are required. chemical method offers, in addition, the advantage that it requires only electrical measurements and that local and instantaneous measurements can be performed. Section 8 discusses such analogy measurements. Thermal radiation as a means of heat transfer has increased in importance in recent years because of the trend in engineering systems towards higher temperatures and because it is the only mechanism for heat transfer from vehicles movingthrough space outside the atnios - phere. in Section 9. Knowledge of thermodynamic and transfer properties is required to calculate heat transfer in specific engineering problems as well as to generalize the results of heat transfer measurements with the use of dimensionless parameters. ments of such properties are often performed concurrently with heat transfer investigations and the techniques used for such measurements are discussed in Sections 10 and 11. The measurement of fluid velocity is often fundamental to measurements of convective heat transfer. The corresponding lecture at the summer course was given by Experimentation of heat transfer processes under cryogenic conditions Optical systems based on variations At high temperatures spectro- The close analogy between heat transfer, on the The electro- Techniques used for the investigation of thermal radiation are discussed Measure- The laser-Doppler method described in Section 12 permits 12 velocities to be inferred from the frequency shift of a scattered laser beam. light beam, unlike a normal velocity probe, does not affect the flow field. measurements which are usually performed by hot wires at low temperatures require special instruments when they are to be performed at higher temperature levels. Such instruments are discussed in Section 13. The authors wish to acknowledge the assistance of W. T. Pennell in the preparation of the manuscript for publication and of D.R. Pedersen in the preparation of the index. We hope that this volume will be useful for those in the various branches of science and engineering who have to perform heat transfer measurements. The Velocity E. R. G. Eckert and R. J. Goldstein Minneapolis, Minnesota November, 1968 * Publisher: [Distributed by Technical Press] * Number Of Pages: 521 * Publication Date: 1970 * ISBN-10 / ASIN: 0851020267 * ISBN-13 / EAN: 9780851020266 * Binding: Unknown Binding