tailieunhanh - Mechanical Engineer´s Handbook P58

CHAPTER 4 1 THERMODYNAMICS FUNDAMENTALS Adrian Bejan Department of Mechanical Engineering and Materials Science Duke University Durham, North Carolina 41,1 INTRODUCTION 1 3 3 1 THE FIRST LAW OF THERMODYNAMICS FOR CLOSED SYSTEMS 1 3 3 3 THE SECOND LAW OF THERMODYNAMICS FOR CLOSED SYSTEMS 1 3 3 5 RELATIONS AMONG THERMODYNAMIC PROPERTIES IDEAL GASES INCOMPRESSIBLE SUBSTANCES 1 3 3 9 1 4 3 1 1 4 3 4 TWO-PHASE STATES 1 4 3 4 THE LAWS OF ANALYSIS OF ENGINEERING THERMODYNAMICS FOR SYSTEM COMPONENTS 1 4 3 7 OPEN SYSTEMS 1 3 3 8 INTRODUCTION Thermodynamics has. | CHAPTER 41__ THERMODYNAMICS FUNDAMENTALS Adrian Bejan Department of Mechanical Engineering and Materials Science Duke University Durham North Carolina INTRODUCTION 1331 RELATIONS AMONG THERMODYNAMIC THE FIRST LAW OF THERMODYNAMICS FOR PROPERTIES 1339 CLOSED SYSTEMS 1333 IDEAL GASES 1341 THE SECOND LAW OF INCOMPRESSIBLE THERMODYNAMICS FOR CLOSED SYSTEMS 1335 SUBSTANCES 1344 TWO-PHASE STATES 1344 THE LAWS OF THERMODYNAMICS FOR ANALYSIS OF ENGINEERING OPEN SYSTEMS 1338 SYSTEM COMPONENTS 1347 INTRODUCTION Thermodynamics has historically grown out of man s determination as Sadi Carnot put it to capture the motive power of fire. Relative to mechanical engineering thermodynamics describes the relationship between mechanical work and other forms of energy. There are two facets of contemporary thermodynamics that must be stressed in a review such as this. The first is the equivalence of work and heat as two possible forms of energy exchange. This facet is encapsulated in the first law of thermodynamics. The second aspect is the irreversibility of all processes changes that occur in nature. As summarized by the second law of thermodynamics irreversibility or entropy generation is what prevents us from extracting the most possible work from various sources it is also what prevents us from doing the most with the work that is already at our disposal. The objective of this chapter is to review the first and second laws of thermodynamics and their implications in mechanical engineering particularly with respect to such issues as energy conversion and conservation. The analytical aspects the formulas of engineering thermodynamics are reviewed primarily in terms of the behavior of a pure substance as would be the case of the working fluid in a heat engine or in a refrigeration machine. In the next chapter we review in greater detail the newer field of entropy generation minimization thermodynamic optimization . .