工程热力学与传热学(英文) 第4章 热力学第二定律.pdfVIP

Thermodynamics Chapter 4 The Second Law of Thermodynamics Chapter 4 The Second Law of Thermodynamics Contents  The second law of thermodynamics which asserts that processes occur in a certain direction and that energy has quality as well as quantity;  The Carnot cycle and Carnot principles;  Entropy;  The Increase of Entropy Principle in Isolated System;  Exergy: A measure of work potential. 4-1 The Second Law of Thermodynamics 4-1-1 Direction of Processes 1. The spontaneous Processes （自发过程） （1）The transfer of heat and work （功热转化） •Work is done on the gas by the paddle wheel •The internal energy of the A gas is increased •The reverse process, raising the mass by transferring heat from the fluid to the paddle wheel, does not occur in nature. B （2 ）Heat transfer across a finite temperature difference （有限温差传热） Higher- Lower- temperature Temperature medium medium Qout pump Qin W （3）Free expansion （自由膨胀） Gas evacuated •No work is done （4 ）Mixing （混合过程） Gas A Gas B 2. Irreversibility of Spontaneous Process （不可逆性） •All the spontaneous processes are irreversible •The reverse process is impossible to make both the system and the surrounding to their initial states. 1st law 2nd law