CHAPTER 8 



INTRODUCTION TO THERMODYNAMICS 



The shipboard engineering plant may be 

 thought of as a series of devices and arrange- 

 ments for the exchange and transformation of 

 energy. The energy transformation of greatest 

 importance in the shipboard plant is the produc- 

 tion of mechanical work from thermal energy, 

 since we depend largely upon this transformation 

 to make the ship move through the water. On 

 steam-driven ships, steam serves the vital pur- 

 pose of carrying energy to the engines. The 

 source of this energy may be the combustion of 

 a conventional fuel oil or the fission of a radio- 

 active material. In either case, the steam that is 

 generated is the medium by which thermal energy 

 is carried to the ship's engines, where it is 

 converted into mechanical energy which propels 

 the ship. In addition, energy transformations 

 related directly or indirectly to the basic pro- 

 pulsion plant energy conversion provide power 

 for many vital services such as steering, light- 

 ing, ventilation, heating, refrigeration and air 

 conditioning, the operation of various electrical 

 and electronic devices, and the loading, aiming, 

 and firing of the ship's weapons. 



In order to acquire a basic understanding of 

 the design of shipboard engineering plants, it is 

 necessary to have some understanding of certain 

 concepts in the field of thermodynamics. In the 

 broadest sense of the term, thermodynamics is 

 the physical science that deals with energy and 

 energy transformations. The branch of thermo- 

 dynamics which is of primary interest to engi- 

 neers is usually referred to as applied thermo- 

 dynamics or engineering thermodynamics ; it 

 deals with fundamental design and operational 

 considerations of boilers, turbines, internal 

 combustion engines, air compressors, refrig- 

 eration and air conditioning equipment, and other 

 machinery in which energy is exchanged or 

 transferred in order to produce some desired 

 effect. 



This chapter deals with certain thermody- 

 namic concepts that are particularly necessary 



as a basis for understanding the shipboard 

 engineering plant. The information given here 

 is introductory in nature; obviously, it is not in 

 any sense a complete or thorough exploration 

 of the subject. Insofar as possible, we will 

 depend upon verbal description rather than 

 mathematical analysis to develop our under- 

 standing of the laws and principles of energy 

 exchanges and transformations. 



It should perhaps be noted that many of the 

 terms used in this chapter— including such basic 

 terms as energy and heat — have more specialized 

 and more precise meanings in the study of ther- 

 modynamics than they do in everyday life or 

 even in the study of general physics. This is 

 only to be expected; thermodynamics is a highly 

 specialized branch of physics and, like any other 

 specialty, it requires a certain refinement of 

 terminology. If any difficulty arises from the 

 fact that familiar terms are used in a somewhat 

 unfamiliar sense, the difficulty can be largely 

 minimized by paying particular attention to the 

 exact meaning of each term, as defined here, 

 rather than depending upon a general knowledge 

 for an understanding of the terms. 



ENERGY 



Although energy has a general meaning to 

 almost everyone, it is not easy to define the 

 word in a completely satisfactory way. Energy 

 is intangible and is largely known through its 

 effects. Because energy is so often manifested 

 by the production of work, energy is commonly 

 defined as "the capacity for doing work." How- 

 ever, this is not entirely adequate as a defini- 

 tion, since work is not the only effect that is 



The student who has the mathematical background 

 required for further study of thermodynamics will find 

 it profitable to consult thermodynamics texts to am- 

 plify the information given in this chapter. 



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