化工热力学 热力学第二定律--第五章熵的定义概念5.6-1

Chapter 5 THE SECOND LAW OF THERMODYNAMICSThe amount of heat transfer is known to depend on the path of the process. However, if the heat is divided by the temperature at which the transfer takes place, the sum of such quantities for the cycle is independent of the path .It is important to remember that this conclusion is valid for reversible processes only.

Chapter 5 THE SECOND LAW OF THERMODYNAMICS Up to this point (在此之前) only a special type of reversible process has been considered, viz, one in which heat transfer has occurred at constant

temperature. We can readily extend our conclusions to any cyclical process as represented schematically by Fig.5.4.

Chapter 5 THE SECOND LAW OF THERMODYNAMICSChapter 5 THE SECOND LAW OF THERMODYNAMICS First divide the enclosed area by a

series of adiabatic curves (shown

dashed) sufficiently close together so that each element, such as 1 to 2 or 7 to 8, can be considered isothermal. Then the cyclical process ADBCA is equivalent to the summation of the elemental cycles.