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Archives of Heat Transfer
1988, Dubrovnik, Yugoslavia

DOI: 10.1615/ICHMT.1988.20thAHT


ISBN Print: 978-0-89116-877-5

ISSN: 0899-5311

THE EFFECTS OF PRESSURE AND TEMPERATURE ON HEAT TRANSFER TO GAS - FLUIDIZED BEDS OF SOLID PARTICLES

pages 397-410
DOI: 10.1615/ICHMT.1988.20thAHT.340
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RÉSUMÉ

A theoretical model for wall-to-bed heat transfer in gas fluidized beds of solid particles has been developed some years ago [1]. The model makes use of some of the fundamental concepts of molecular kinetic theory as applied to solid particles in a fluidized bed. Recently this model has been slightly modified to improve its applicability in a wide range of variables [2,3]- It has been shown, that the predictions of this model are in fair agreement with most experimentally observed phenomena, especially with the characteristic nonmonotonous variations of heat transfer coefficients with particle size and with bed voidage (or gas flowrate) [3-7]. Many applications of fluid bed technology involve high temperatures and sometimes also high pressures. It is the aim of this paper to discuss the effects of pressure and temperature both from the viewpoint of model predictions and the available experimental evidence.
In the first part of the paper (MODEL) the basic ideas and concepts of the theoretical approach as well as the assumptions and hypotheses used to derive the model equations shall be briefly reviewed.
The second part (PARAMETERS) discusses the main dependecies of wall-to - bed heat transfer coefficients on particle size, bed voidage and particle as well as gas properties, as predicted from the model equations in comparison with a few typical sets of experimental data.
The third part (VARIABLES) deals with the influence of pressure (lower as well as higher than atmospheric) and temperature on heat transfer to gas fluidized beds of solid particles.
In the fourth part (APPLICATION) experimental data obtained by Bergbau-forschung, Essen, in a pilot scale allothermal coal gasificaiton plant with both high pressure (up to 40 bar) and high temperature (∼800°C) will be presented and compared to the model predictions.

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