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 2 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≠To Unconvertible energy-internal energy in surrounding 上游充通大 April 8,2018 7 SHANGHAI JIAO TONG UNIVERSITYApril 8, 2018 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