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 (3) Draw a line for a compressor(4) Draw a line through an expansion valve A specific volume and specific enthalpies at each point Specific volume 　ｖ 1=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 B S C E D K F GM 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 B S 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Q K =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υ A ＝0.0595 m^3/kg。 i AB AB hh hh s η= ? ? HMA hhh 1.09.0 += 10*)( EDKH hhhh ?+= 2 4, Real system with environmental parameters Inputs: Compressor: displacement,work plot Condenser/Evaporator:given HX area,air inlet parameters TXV/Cap. Compressor performance Where to Start… How to close the cycle… lg p 1 2 3 4 1‘ Pe,Tsh Pc Pc/Pe λ,m cm ,W Pe,Tsh T1,v1,T2 由压缩机模型得到 由冷凝器换热计算可 得到 T3， Qc 由蒸发器换热计算可 得到 T1’， Qe h3=h4 m cap 3个假设条件（变量） : Pc\Pe\Tsh 方程数： T 1 ’=T 1 m cap = m cm 充注量 制冷系统的流量平衡 毛细管和压缩机的流量平衡关系 如果节流机构是 TXV？ 如果有储液装置存在，充注量就不敏感，此时怎么办?