Advanced_Thermo_for_Engineers


 

When reviewing, or contemplating writing, a textbook on engineering thermodynamics, it is necessary to ask what does this book offer that is not already available? The author has taught thermodynamics to mechanical engineering students, at both undergraduate and post-graduate level, for 25 years and has found that the existing texts cover very adequately the basic theories of the subject. However, by the final years of a course, and at post-graduate level, the material which is presented is very much influenced by the lecturer, and here it is less easy to find one book that covers all the syllabus in the required manner. This book attempts to answer that need, for the author at least.

The engineer is essentially concerned with manufacturing devices to enable tasks to be preformed cost effectively and efficiently. Engineering has produced a new generation of automatic ‘slaves’ which enable those in the developed countries to maintain their lifestyle by the consumption of fuels rather than by manual labour. The developing countries still rely to a large extent on ‘manpower’, but the pace of development is such that the whole world wishes to have the machines and quality of life which we, in the developed countries, take for granted: this is a major challenge to the engineer, and particularly the

thermodynamicist. The reason why the thermodynamicist plays a key role in this scenario is because the methods of converting any form of energy into power is the domain of thermodynamics: all of these processes obey the four laws of thermodynamics, and their efficiency is controlled by the Second Law. The emphasis of the early years of an undergraduate course is on the First Law of thermodynamics, which is simply the conservation of energy; the First Law does not give any information on the quality of the energy. It is the hope of the author that this text will introduce the concept of the quality of

energy and help future engineers use our resources more efficiently. Ironically, some of the largest demands for energy may come from cooling (e.g. refrigeration and airconditioning) as the developing countries in the tropical regions become wealthier – this might require a more basic way of considering energy utiiisation than that emphasised in current thermodynamic texts. This book attempts to introduce basic concepts which should apply over the whole range of new technologies covered by engineering thermodynamics.

It considers new approaches to cycles, which enable their irreversibility to be taken into

account; a detailed study of combustion to show how the chemical energy in a fuel is converted into thermal energy and emissions; an analysis of fuel cells to give an understanding of the direct conversion of chemical energy to electrical power; a detailed study of property relationships to enable more sophisticated analyses to be made of both high and low temperature plant; and irreversible  thermodynamics, whose principles might hold a key to new ways of efficiently converting energy to power (e.g. solar energy, fuel cells).

The great advances in the understanding and teaching of thermodynamics came rapidly towards the end of the 19th century, and it was not until the 1940s that these were embodied in thermodynamics textbooks for mechanical engineers. Some of the approaches used in teaching thermodynamics still contain the assumptions embodied in the theories of heat engines without explicitly recognising the limitations they impose. It was the desire to remove some of these shortcomings, together with an increasing interest in what limits the efficiency of thermodynamic devices, that led the author down the path that has

culminated in this text.

I am still a strong believer in the pedagogical necessity of introducing thermodynamics through the traditional route of the Zeroth, First, Second and Third Laws, rather than attempting to use the Single-Axiom Theorem of Hatsopoulos and Keenan, or The Law of Stable Equilibrium of Haywood. While both these approaches enable thermodynamics to be developed in a logical manner, and limit the reliance on cyclic processes, their understanding benefits from years of experience – the one thing students are lacking. I have structured this book on the conventional method of developing the subject. The other

dilemma in developing an advanced level text is whether to introduce a significant amount of statistical thermodynamics; since this subject is related to the particulate nature of matter, and most engineers deal with systems far from regions where molecular motion dominates the processes, the majority of the book is based on equilibrium thermodynamics; which concentrates on the macroscopic nature of systems. A few examples of statistical thermodynamics are introduced to demonstrate certain forms of behaviour, but a full understanding of the subject is not a requirement of the text.

The book contains 17 chapters and, while this might seem an excessive number, these are of a size where they can be readily incorporated into a degree course with a modular structure. Many such courses will be based on two hours lecturing per week, and this means that most of the chapters can be presented in a single week. Worked examples are included in most of the chapters to illustrate the concepts being propounded, and the chapters are followed by exercises. Some of these have been developed from texts which are now not available (e.g. Benson, Haywood) and others are based on examination questions. Solutions are provided for all the questions. The properties of gases have been

derived from polynomial coefficients published by Benson: all the parameters quoted have been evaluated by the author using these coefficients and equations published in the text – this means that all the values are self-consistent, which is not the case in all texts. Some of the combustion questions have been solved using computer programs developed at UMIST, and these are all based on these gas property polynomials. If the reader uses other data, e.g. JANAF tables, the solutions obtained might differ slightly from those quoted.

 

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