FOUNDATIONS OF HEAT TRANSFER

So far, we have learned the foundations of heat transfer. We are now ready to proceed to individual problems controlled by conduction, which is the simplest of the... 

Thus, the quest for knowledge of heat transfer continued, and by the early part of the twentieth century, the foundation of heat transfer theory was established with proven laws and principles. With the progress of the twentieth century, those fundamental theories of heat transfer were gradually applied in thermal engineering and other engineering disciplines for the benefits of mankind. 

Convective heat transfer has become a subject of very wide extent and the selection of material for inclusion in a book of the present type requires careful consideration. In this book, heat transfer during boiling and solidification have not been considered. This is not in any way meant to suggest that these topics are of lesser importance than those included in the book. Rather, it is felt that the student needs a good grounding in the topics covered in the present book before approaching the analysis of heat transfer with boiling and solidification. The book thus lays the foundation for more advanced courses on specialized aspects of convective heat transfer. 

The basic aim of the book is to present a discussion of some currently available methods for predicting convective heat transfer rates. The main emphasis is, therefore, on the prediction of heat transfer rates rather than on the presentation of large amounts of experimental data. Attention is given to both analytical and numerical methods of analysis. Another aim of the book is to present a thorough discussion of the foundations of the subject in a clear, easy to follow, student-oriented style. 

Based on the above three models, a dynamic model to scale-up the vacuum pyrolysis process was developed, which correlates the temperature and the mass of feedstock at any position on top of the heating plates inside the reactor, as a function of heat transfer, panicle flow and pyrolysis kinetics phenomena. The energy conservation in the reactor is the foundation of the model. It assumes i) steady flow, ii) one dimensional terr erature variation and, iii) feedstock thermal properties vary as a function of temperature T. 

Kutateladze, S. S., Foundations of the Theory of Heat Transfer, Atomizdat, Moscow, 1979 [in Russian],... 

The foundations of an engineering discipline may be best understood by considering the place of that discipline in relation to other engineering disciplines. Therefore, our first concern in this chapter will be to determine the place of heat transfer among engineering disciplines. Next, we shall proceed to a review of the general principles needed for heat transfer. Finally, we shall discuss the three modes of heat transfer— conduction, convection, and radiation—and introduce a five-step methodology for an inductive formulation. 

It is appropriate here to make some remarks on the physical foundations of thermal conductivity. The dependence of thermal conductivity on temperature has been experimentally recognized. However, there is no universal theory explaining this dependence. Gases, liquids, conducting and insulating solids can each be explained with somewhat different microscopic considerations. Although the text is on the continuum aspects of heat transfer, the following remarks are made for some appreciation of the microscopic aspects of thermal conductivity. 

There have been a great many studies of heat transfer in fluidized beds of large particles, which are important for the design of fluid-bed boilers. The maximum coefficients are lower than with type A solids, and some experiments show a gradual decrease in h with increasing dp and a minimum hat dp = 2 3 mm [28]. Extensive data are presented in books [29,30] and in the proceedings of the Engineering Foundation Conferences on Fluidization. 

The theory behind the third law of thermodynamics was initially formulated by Walther Nemst in 1906, which was known as Nemst theorem (https //www.sussex. ac.uk/webteam/gateway/file.php name=a-thermodynamicshistory. pdf site=35). The third law of thermodynamics was conceived from the fact that attaining absolute zero temperature is practically impossible. Lord Kelvin deduced this fact from the second law of thermodynamics with his study of heat transfer, work done, and efficiency of a number of heat engines in series. Kelvin s work was the foundation for the formulation of the third law. It can be stated as follows Absolute zero temperature is not attainable in thermodynamic processes. Another noted scientist, Max Planck, put forward the third law of thermodynamics from his observations in 1913. It states that The entropy of a pure substance is zero at absolute zero temperature. Plank observed that only pure, perfectly crystalline stmctures would have zero entropy at absolute zero temperamre. All other substances attain a state of minimum energy at absolute zero temperature as the molecules of the substance are arranged in their lowest possible energy state. 

The classic description of heat transfer in a combusting composite laminate or plane slab has been provided by Henderson, [1], and this remains the foundation for practically all variations of mass and energy balances attempted since then, (see equation 14.1). The terms of this equation are included in Figure 14.2. to illustrate the locations within the slab where they are relevant. 

Molems, O., and Schweinzer, J., Prediction of Gas Convective Part of the Heat Transfer to Fluidized Beds, pp. 685-693, Fluidization IV, Eng. Foundation, New York, USA (1989)... 

Ozkaynak, T. F., Chen, J. C., and Frankenfield, T. R., An Experimental Investigation of Radiant Heat Transfer in High Temperature Fluidized Bed, Fluidization, Fourth International Conf. on Fluidization, pp. 371— 378, Engineering Foundation (1983)... 

Xavier, A. M., and Davidson, J. F., Heat Transfer to Surfaces Immersed in Fluidized Beds, Particularly Tube Arrays, Fluidization, Proc. of Second Eng. Foundation Conf., pp. 333-338, Cambridge Univ. Press (1978)... 

Denn, Polymer Melt Processing Foundations in Fluid Mechanics and Heat Transfer Duncan and Reimer, Chemical Engineering Design and Analysis An Introduction Fan and Zhu, Principles of Gas-Solid Flows Fox, Computational Models for Turbulent Reacting Flows... 

As a principal investigator for research sponsored by the Atomic Energy Commission, National Science Foundation, NASA, and the Environmental Protection Agency, he has published extensively in such journals as Industrial and Engineering Chemisty, International Journal of Heat and Mass Transfer, Journal of the Aerospace Sciences, and others. 

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