《制冷与低温原理》课件C第三章 蒸气制冷循环 5 (3.3)07

1、3 Vapor refrigeration cycles3.1 One-stage vapor compression systems3.2 Two-stage vapor compression systems3.3 Cascade vapor compression systems3.4 Vapor absorption systems 第三章 蒸汽制冷循环第一节单级蒸气压缩制冷循环第二节两级蒸气压缩制冷循环第三节复叠式制冷循环第四节 蒸气吸收制冷循环3.3 Cascade vapor compression systems 3.3.1 Introduction3.3.2 Design t

2、ype analysis3.3.3 Operation type analysis3.3.4 Auto cascade systems第三节复叠式制冷循环一、绪论二、设计型分析三、操作型分析四、自复叠制冷循环8/1/202233.3 Cascade vapor compression systems 第三节 复叠式制冷循环 3.3.1 Introduction 一、绪论 Discharge capacity: f（PR） qvsqvt Throttle loss: q0 Q0qmq0 qvtq0 /v1 Discharge temperatureReasons: （pKp0）; PR ( -

3、40 ) 8/1/202243.3 Cascade vapor compression systems 第三节 复叠式制冷循环 3.3.1 Introduction 一、绪论 Freezing point: p0 T0 Ta ( with low Tb )Reasons: （pKp0）; PR ( - 70 ) 3.3 Cascade vapor compression systems3.3.1 Introduction3.3.2 Design type analysis3.3.2.1 Close cycles 3.3.2.2 Open cycles 3.3.2.3 Special struc

4、ture parts3.3.2.4 Thermodynamic calculation第三节复叠式制冷循环一、绪论二、设计型分析（一）闭式循环（二）开式循环（三）特殊结构部件（四）热力计算8/1/202263.3.2.1 Close cycles （一）闭式循环 3.2.2.1.1 Binary systems 二元复叠R22 cycle : tk=30, t0H-36 pkH=1.2MPa, p0H=0.12MPa PRH=10 One-stage + One-stage ( 80 )R23 cycle : tmL=-30 , t0L-80 pkL=10MPa, p0L=1MPa PRL=1

5、0 8/1/202273.3.2.1 Close cycles （一）闭式循环 3.2.2.1.1 Binary systems 二元复叠One-stage + Two-stage ( Two-stage + One -stage ) ( -100 )8/1/202283.3.2.1 Close cycles （一）闭式循环 3.2.2.1.2 Multiple systems 多元复叠One-stage + One-stage + One-stage ( -100 -140 ) Middle temperature refrigerants : R23、R170、R1150 High tem

6、perature refrigerants : R134a、R290、R507、R22 Low temperature refrigerants : R14、R50、R7288/1/202293.3.2 Design type analysis 二、设计型分析 3.3.2.2 Open cycles （二）开式循环The production of dry ice (CO2) 8/1/2022103.3.2 Design type analysis 二、设计型分析 3.3.2.2 Open cycles （二）开式循环x8 qmo /( qmo + qm) qmoqmx8 /( 1- x8)

7、qm1 = qm + qmo qm1qm /( 1- x8)x6 qm1 /( qm1 + qm1) qm1qmx6 / ( 1- x6)( 1- x8) qm2 = qm1 + qm1 qm2qm /( 1- x6)( 1- x8)qm18/1/2022113.3.2 Design type analysis 二、设计型分析 3.3.2.3 Special structure parts （三）特殊结构部件1. Condenser-reboiler 冷凝蒸发器 2. Vapor-liquid recuperator 气-液回热器8/1/2022123.3.2 Design type anal

8、ysis 二、设计型分析 3.3.2.3 Special structure parts （三）特殊结构部件3. Precooler 预冷器4. Vapor-vapor recuperator 气-气回热器8/1/2022133.3.2 Design type analysis 二、设计型分析 3.3.2.3 Special structure parts （三）特殊结构部件5. Expansion tank 膨胀容器mzmx Vdx 、 vd?m1 Vp、vx停机前mzmp Vdx 、 vpm1 + m2 Vp 、vp停机后8/1/202214Homework_1313. 有一低温复叠式制冷

9、机，低温系统中（不包括膨胀容器）需充注R23制冷剂2.4kg，工作压力为100kPa。如欲使制冷系统在环境温度为40时允许1.0MPa的平衡压力，停机时进入膨胀容器中制冷剂占充注量（包括膨胀容器）的60%，试求膨胀容器的容积。 （ m2= 0.6mz ）。8/1/2022153.3.2 Design type analysis 二、设计型分析 3.3.2.3 Special structure parts （三）特殊结构部件m1 + mx = m1 + m2+ mp = mzm1=Vp/vxmp=Vdx/vp m1 + m2=Vp/vpmzmx Vdx 、 vd?m1 Vp、vx停机前mzmp

10、 Vdx 、 vpm1 + m2 Vp 、vp停机后5. Expansion tank 膨胀容器8/1/2022163.3.2 Design type analysis 二、设计型分析 3.3.2.4 Thermodynamic calculation （四）热力计算User specified: TH、TL、Q0Designer chosen: TH、TL、 Tm ig、id 、mg 、mdDesign parametersTm 58/1/2022173.3.2 Design type analysis 二、设计型分析 3.3.2.4 Thermodynamic calculation （四

11、）热力计算User specified: TH、TL、Q0Designer chosen: TH、TL、 Tm ig、id 、mg 、mdDesign parameters2. PR ConstTm=(TkTo)0.50.5T+0.125T 2 / (TkTo)0.5(3-77)One-stage + One-stageTwo-stage + Two-stageTm 58/1/2022183.3.2 Design type analysis 二、设计型分析 3.3.2.4 Thermodynamic calculation （四）热力计算Index Low temperature stageH

12、igh temperature stage1Q0Q0LQ0H = QkL+ QH2q0q0L= h1-h5q0H = h6-h103w0w0L = h2-h1w0H = h7-h64qmqmL= Q0L / q0LqmH = Q0H/ q0H5PPL= qmLw0L /elLPH= qmH w0H /elH6QkQkL = qmLqkL = qmL (h2-h4)QkH = qmHqkH = qmH (h7-h9)7COPCOP = Q0 / P = Q0d / ( PL + PH)3.3 Cascade vapor compression systems 3.3.1 Introduction

13、3.3.2 Design type analysis3.3.3 Operation type analysis3.3.4 Auto cascade systems第三节复叠式制冷循环一、绪论二、设计型分析三、操作型分析四、自复叠制冷循环8/1/2022203.3.3 Operation type analysis 三、操作型分析1. Start-up: high temperature stage first ( 1.6MPa)2. The maximum evaporating temperatureOne-stage + One-stageTwo-stage + One-stageOne-

14、stage + Two-stageT0-80-110-110T0max-60-60-903.3 Cascade vapor compression systems 3.3.1 Introduction3.3.2 Design type analysis3.3.3 Operation type analysis3.3.4 Auto-cascade systems第三节复叠式制冷循环一、绪论二、设计型分析三、操作型分析四、自行复叠制冷循环8/1/2022223.3.4 Auto-cascade compression systems 四、自行复叠制冷循环Classical cascade cycl

15、esAuto cascade cyclesMultiple composition cycles8/1/2022233.3.4 Auto-cascade compression systems 四、自行复叠制冷循环Auto cascade cyclesClassical cascade cycles一次分凝循环多次分凝循环8/1/2022243.3.4 Auto-cascade compression systems 四、自行复叠制冷循环Auto cascade cyclesClassical cascade cycles精馏循环多次分凝循环8/1/2022253.3.4 Auto-cascade compression systems 四、自行复叠制冷循环Single composition cycles精馏循环多次分凝循环Multiple composition cyclesNon-azeotropic cycles8/1/202226SummaryTemperature rangeCycle typeTL-40One-stage compression单级压缩Auto cascade compression自复叠压缩-40TL-60Two-stage compression两级压缩-60TL-80Two-stage co