Summary Spontaneous process: processes proceed in a certain direction initial condition of the system can be restored,but not in a spontaneous process.Some auxiliary devices would be required (a permanent change in the condition of the surroundings would result.) satisfying the first law does not ensure that the process can actually occur 上游充通大学 Mar/29,Wed,2017 6 SHANGHAI JLAO TONG UNIVERSITY
Mar/29, Wed, 2017 6 Summary Spontaneous process: • processes proceed in a certain direction • initial condition of the system can be restored, but not in a spontaneous process. Some auxiliary devices would be required (a permanent change in the condition of the surroundings would result.). • satisfying the first law does not ensure that the process can actually occur
Relations?:quality of energy -spontaneous Quality degrading spontaneous. Quality upgrading>need compensation. But overall effect:quality degrading. Hot reservoir Hot reservoir T T Wnet Wnet R Q21 Cold reservoir Cold reservoir T2 T2 Fully convertible energy-mechanical /electrical energy Direction of energy conversion energy quality difference Partially convertible energy-heat t T≠To Unconvertible energy-internal energy in surrounding 上游充通大 Mar/29,Wed,2017 7 SHANGHAI JIAO TONG UNIVERSITY
Mar/29, Wed, 2017 7 Relations?: quality of energy – spontaneous Quality degrading spontaneous. Quality upgrading need compensation. But overall effect: quality degrading. Hot reservoir T1 E Cold reservoir T2 Q1 Q2 Wnet Hot reservoir T1 R Cold reservoir T2 Q1 Q2 Wnet Direction of energy conversion = energy quality difference Fully convertible energy—mechanical /electrical energy Partially convertible energy—heat T T0 Unconvertible energy—internal energy in surrounding