PREFACE
Downloaded by 80.82.77.83 on January 8, 2018 | http://pubs.acs.org Publication Date: November 11, 1983 | doi: 10.1021/bk-1983-0235.pr001
OVER THE YEARS, PROMINENT THERMODYNAMICISTS
have advocated second law analyses for properly evaluating energy conversion processes on the basis of available energy. The concept of available energy, now also called exergy and essergy, originated with Maxwell and Gibbs. Unfortunately, it has not taken hold in engineering practice or in managerial decision making. Many practitioners still view energy as the commodity of value, as the "potential to cause change," and therefore produce confusing and erroneous analyses. For example, we know from the first law of thermodynamics that energy is not consumed in a process; therefore, whatever energy is supplied with fuel must end up somewhere—if not in the desired product, then in some waste. Consequently, effluent wastes are grossly overestimated in value while consumptions within processes—the major inefficiencies—are overlooked completely. The second law of thermodynamics makes a distinction between the total energy, which remains constant, and the exergy or available energy, which is consumed as it drives a process. The key to resolving inaccurate or inconsistent process efficiency analyses is simply to recognize that exergy is the proper measure. With exergy analysis, which involves the same calculational procedures as energy analysis, engineers can determine the true inefficiencies and losses, and only then make valid decisions concerning design and operation parameters. The concept of exergy is crucial not only to efficiency studies but also to cost accounting and economic analyses. Costs should reflect value; because the value is not in energy but in exergy, assignment of cost to energy often leads to large misappropriations. Management should also use exergy content as a basis for pricing products and evaluating their profits. An earlier book, ACS Symposium Series No. 122, "Thermodynamics: Second Law Analysis," is an introduction to the direct application of the second law of thermodynamics to (1) process efficiency analysis and (2) cost accounting in energy conversion systems and chemical/metallurgic processes. Since the publication of that volume, there has been a steady growth in the interest in applying these methods, and hence, more applications that encompass a greater realm of processes have surfaced. The purpose of this sequel is to present these new applications—in particular those that shed additional light on the theory and practice of the subject. The reader may wish to refer
ix Gaggioli; Efficiency and Costing ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
to the first volume for further elaboration of the fundamentals and the details of application procedures. The table of contents of the earlier book is presented on page 461. Exergy analyses not only avoid many misconceptions resulting from energy analyses but also point out the way to economic energy conservation.
RICHARD A. GAGGIOLI The Catholic University of America School of Engineering and Architecture Washington, D.C.
Downloaded by 80.82.77.83 on January 8, 2018 | http://pubs.acs.org Publication Date: November 11, 1983 | doi: 10.1021/bk-1983-0235.pr001
August 1983
x and Costing Gaggioli; Efficiency ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
