《制冷原理与技术》讲座 1.What is a p-h diagram? 在如-/图上表示制冷循环 陈 上海交通大学制冷研究所 bm比 一个临界点 六条等值线 2. How to draw a refrigeration cycle on a 2. Refrigeration Cycle in p-h diagram Refrigerant I Temperature Temperature/ before the Suction Gas Evaporating Condensing emperature otice: Conditions may be given as follows. Meanings of both are the same. Specific Entha py W/ke Point I to 2. Refrigerant change = Point 3 to 4: Refrigerant change through an expansion valve R22 1.192MP5℃s℃ Point 4 to 1: Refrigerant change in an evaporator 3. For complex system ()Drawa 释了 距计1 在lgp-h图上表示制冷循环 陈江平 上海交通大学制冷研究所 《制冷原理与技术》讲座 1.What is a p-h diagram? 一个临界点 两条饱和线 三个状态区 六条等值线 2. Refrigeration Cycle in p-h diagram Point 1 to 2: Refrigerant change in a compressor Point 2 to 3: Refrigerant change in a condenser Point 3 to 4: Refrigerant change through an expansion valve Point 4 to 1: Refrigerant change in an evaporator 2.How to draw a refrigeration cycle on a p-h diagram Refrigerant Evaporating Temperature Condensing Temperature Liquid Temperature before the Expansion Valve Suction Gas Temperature R22 -15℃ 30℃ 25℃ -10℃ Notice: :Conditions may be given as follows. Meanings of both are the same. Refrigerant Evaporating Pressure Condensing Pressure Subcool Superheat R22 0.296 MPa 1.192 MPa 5℃ 5℃ (1) Draw a line for a condenser (2) Draw a line for an evaporator (4) Draw a line through an expansion valve (3) Draw a line for a compressor A specific volume and specific enthalpies at each point Specific volume ｖ1=0.08 m3/kg、 Specific enthalpy h1=403 kJ/kg, h2=438 kJ/kg, h4=230 kJ/kg You can calculate a performance of a refrigerating machine by using these values. 3. For complex system MA B 蒸 发 器 气 液 分 离 器 热交换器 过冷器 冷 凝 器 压缩机 G F E K C D H A H B BS C E D K F G M lgp h 状态点 温度 焓（kj/kg） M 403.499 K 194.176 E 20 224.084 D 38 247.042 C 40 249.686 BS 53 438.305 已知出蒸发器制冷剂干度为0.9，才 能保证系统连续运转。其循环参数见 下表。已知QK=19.7KW，压缩机指示效 率0.85，压缩机容积效率λ＝0.8， 吸气点A的比容υA＝0.0595 m^3/kg。 i B A B A h h h h s =η − − hA hM 1hH = 0.9 + 0. hH = hK + (hD − hE )*10