第一章制冷与低温的热力学基础 4 (1.2)_2015_09_29

1、1 Thermodynamic fundamentals of refrigeration and cryogenic engineering1.1 Methods of refrigeration1.2 Thermodynamic analysis of refrigeration cycles (First Law of thermodynamics)第一章 制冷与低温的热力学基础第一节 制冷的方法第二节 制冷循环热力学特性分析（热一律）7/20/20222Cooling and refrigeration cycle制冷与制冷循环Normal Boiling PointCritical

2、PointInversion PointTb（K）Tb（）Tc（K）Tc（）Tmax（K）tmax（）N274.4-198.8126.3-146.9604331H220.4-252.833.3-239.9204-69He4.3-268.95.3-267.946-2270.01atm0.83K7/20/20223Refrigeration cycle制冷循环RefrigeratorTHTLHigh temperature heat source高温热源Low temperature heat source低温热源1.2 Thermodynamic analysis of refrigeratio

3、n cycles (First Law of thermodynamics)1.2.1 Reversed Carnot cycle 1.2.2 Reitlinger cycle 1.2.3 Lorents cycle1.1.4 Heat pump cycle 1.1.5 Heat driven refrigeration cycle 1.1.6 Gas liquefaction cycle第二节 制冷循环热力学特性分析（热一律）一、逆卡诺循环四、热泵循环二、瑞特林循环五、热能驱动制冷循环三、洛仑兹循环六、气体液化循环7/20/202251.2.1 Reversed Carnot cycle一、

4、逆卡诺循环RefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature heat source低温热源7/20/202261.2.1 Reversed Carnot cycle一、逆卡诺循环7/20/202271.2.1.1 Cycle analysis based on the cycle （一）循环内部分析法q0=T0 (s1-s4)=TL (s1-s4)qk= Tk (s1-s4)= TH (s2-s3)w0=qk - q0=(TH-TL)(s2-s3)RefrigeratorTHTLw0qkq0High te

5、mperature heat source高温热源Low temperature heat source低温热源7/20/202281.2.1.2 Cycle analysis based on the heat source （二）循环外部分析法RefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature heat source低温热源7/20/20229Reversed Carnot cycle with temperature differences 具有传热温差的卡诺型制冷循环q0=T0 (s1-s4) TL

6、 (s1-s4)qk= Tk (s1-s4) TH (s2-s3)w0=qk - q0=(Tk-T0)(s2-s3)w0qkq0RefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature heat source低温热源7/20/202210Reversed Carnot cycle with temperature differences 具有传热温差的卡诺型制冷循环w0qkq0RefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature

7、 heat source低温热源7/20/202211Refrigeration ? ( Cooling ?)Refrigeration = Obtaining artificial cold sources热量从温度较低的物体转移到温度较高的物体热量从温度较高的物体转移到温度较低的物体Refrigerant冷源的获取冷环境的获取制造人工低温环境7/20/202212Refrigeration ? ( Cooling ?)冷环境的获取Heat sourceCold source (Heat sink)SurroundingsSecond refrigerantRefrigerationHeat

8、 transfer (cooling)7/20/2022131.2.2 Reitlinger cycle and constant temperature heat source二、瑞特林循环和等温热源THTLRefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature heat source低温热源7/20/2022141.2.2 Reitlinger cycle and constant temperature heat source等温热源和变温热源冰箱内空气有限大等温热源 等温热源：热源的温度在整个传热面上的

9、温度均相等； 变温热源：热源的温度在整个传热面上的温度不完全相等。 有限大热源：热源的热容量是有限值，其温度分布随换热率的大小而变 无限大热源：热源的热容量无限大，其温度分布不随换热率的大小而变空调内空气有限大变温热源冰箱外空气无限大等温热源空调内电热丝无限大变温热源7/20/2022151.2.3 Lorents cycle and variable temperature heat source三、洛仑兹循环和变温热源TH (TK)TL (T0)qKq0w0THmTLmRefrigeratorTHTLw0qkq0High temperature heat source高温热源Low tem

10、perature heat source低温热源7/20/202216Lorents cycle and Reitlinger cycle洛仑兹循环和瑞特林循环TH (TK)TL (T0)qKq0w0THTL在热源温度变化的条件下，由两个和热源之间无温差的热交换过程及两个等熵过程所组成的逆向可逆循环（洛仑兹循环），是制冷系数最高的循环。7/20/2022171.2.3 Lorents cycle and variable temperature heat source三、洛仑兹循环和变温热源THTLTHmTLmTkT0THTLTHTLRefrigeratorTHTLw0qkq0High tem

11、perature heat source高温热源Low temperature heat source低温热源在热源温度变化的条件下，由两个和热源之间无温差的热交换过程及两个等熵过程所组成的逆向可逆循环（洛仑兹循环），是制冷系数最高的循环。7/20/2022181.2.4 Heat pump cycle四、热泵循环Heat pumpTHTLHigh temperatureAmbient temperature环境温度RefrigeratorTHTLAmbient temperature环境温度Low temperaturew0qkq0w0qkq07/20/2022191.2.4 Heat pu

12、mp cycle四、热泵循环Heat pumpTHTLHigh temperatureAmbient temperature环境温度w0qkq07/20/202220小型风力驱动冷却法获取淡水装置Cold endHot end7/20/202221小型风力驱动冷却法获取淡水装置ColdHot7/20/2022221.2.5 Heat driven cycle五、热能驱动制冷循环CompressorHeatCompressor7/20/2022231.2.5 Heat driven cycle五、热能驱动制冷循环TLTHTHHRefrigeratorTHTHHTL7/20/2022241.2.6

13、 Gas liquefaction cycle六、气体液化循环CompressedLiquefiedgasified?wmin = qk - q0 = T1(s1-s0) - (h1-h0) 7/20/202225Energy indexes of a refrigeration cycle制冷循环的能量指标 性能系数 (Coefficient of performance)热力完善度(Thermodynamic perfect degree)制冷量 (Cooling capacity)(J)制冷率 (Cooling capacity rate)(W)RefrigeratorTHTLw0qkq0High temperature heat source高温热源Low temperature heat source低温热源7/20/202226Homework_4-64. Please try to derive the expression of COP for the Lorents cycle based on the heat sources. 5：寻找一种合适的比喻给没