Trasmissione del calore nei letti fluidizzati con liquidi

Research output: Chapter in Book/Report/Conference proceedingChapter


[automatically translated] The study of phenomena related to the hydrodynamics and heat transfer in fluidized beds is of great interest industrial nell'Energetica. In fact it is necessary for their understanding propose reliable models for the design and simulation of the operation of many devices in which they are manifested. In many industrial processes the contacts and interactions between fluids, whether liquid or gas, and solid particulates allow a great variety of useful applications. This is the engineering field of fluidization, which has aroused widespread interest since the implementation, during the Second World War, the fluidized bed reactors for the catalytic cracking of petroleum. The engineering of the fluidization covers a wide range of uses and these include: - Applications of fluidized beds with gas for combustion, gasification of fuels and solid residues, the heating and drying of the particles, the chemical industry, the catalytic and thermal cracking of petroleum, etc .; - Fluid beds of applications with liquids in the chemical industry and in heat-exchange equipment as in the case of recovery systems for the waste heat, direct use of geothermal fluids, etc. The technical interest fluidized beds are of two types: - fluidized beds with liquid - fluidized beds with gaseous. The first type is based applications in which the support fluid is a liquid within which there is the presence of a solid particulate, often heterogeneous, which can be inert or can chemically react with the support fluid or with some components of the same particulate. The second type is based applications in which the support fluid is a gaseous substance instead within which there is the presence of solid particulate, also here often heterogeneous, which can be inert or may react in a way contrary said. More complex applications are the chemical industry and are not covered by this report; it is instead dedicated to its most mechanical engineering applications, which affect the thermal exchange between the fluid bed and an exchange surface in contact with the bed. They are issues that concern the design and verification of heat exchangers in fluid bed in which interesting the heat exchange between a dirty fluid (which is the support fluid) and a surface of the fluid bed exchange (as in geothermal applications ), the freezing of legumes and vegetables, drying of cereal grains, etc., the combustion of coal in a fluid bed or the wood processing residues and also of waste difficult to burn. In the literature of the past two decades it has a significant number of papers published by magazines that report the results of various experimental researches both on its hydrodynamics phenomena on phenomena relating to the thermal exchange. There are also a few books on the above topics. The models proposed in the literature, both for the prediction of the hydrodynamic behavior of the heat transfer coefficients, they are complex. It follows that the methods of correlation of the experimental data of the heat exchange between the fluidized bed and an immersed surface in it are equally complex and typically differ for the various series addressed; It is not so easy to extend its application to cases different from those for which they were obtained. Then the situation is even more uncertain when you want to address the questions of heat exchange relative to radiation, from which you can not ignore when in bed you can reach and exceed temperatures of 600 ° C. The models proposed in the literature can be essentially divided into two categories:
Original languageItalian
Title of host publicationRicerche sulle applicazioni della fluidizzazione in energetica industriale
Number of pages178
Publication statusPublished - 2007

Cite this