試比較如下幾種水蒸氣、水和冰的有效能(設基態(tài)為298K,0.1MP,其Ex0=0) (1)0.15MPa,160℃過熱蒸汽; (2)0.3MPa,160℃過熱蒸汽; (3)0.07MPa,100℃過熱蒸汽; (4)100℃飽和蒸汽 (5)0.1MPa,100℃飽和水; (6)0.1MPa,0℃冰(此時冰H=-334.4kJ/kg;S=-1.2247kJ/kg.K)