Bài giảng Chapter 5 multi stage system

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Bài giảng Chapter 5: Multi stage system with the goal of helping students can Understand and analyse the basic of multi-stage refrigeration system; calculate multi-stage refrigeration system. Hope the document is useful source of information for the study and research of you.

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Nội dung Text: Bài giảng Chapter 5 multi stage system

CHAPTER 5: MULTI-STAGE SYSTEM Lecturer : ThS. Nguyễn Duy Tuệ 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 1
OBJECTIVES In this chapter, chapter student st dent can : - Understand and analyse the basic of multi-stage refrigeration system - Calculate multi-stage refrigeration system 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 2
REFERENCES [1]. Kỹ thuật [1] th ật lạnh cơ sở - Nguyễn Ng ễn Đức Lợi [2]. Industrial Refrigeration Handbook – Mc Graw Hill 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 3
CONTENT TWO STAGE CYCLE; 1 EXPANSION VALVE, PARTIAL INTERSTAGE DE-SUPERHEAT TWO STAGE CYCLE CYCLE; 2 EXPANSION VALVE VALVE, PARTIAL INTERSTAGE DE-SUPERHEAT TWO STAGE CYCLE; INTERSTAGE DE-SUPERHEAT WITHOUTH LIQUID SUBCOOL TWO STAGE CYCLE; INTERCOOLER WITH LIQUID SUBCOOL 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 4
INTRODUCTION +Investigate this one stage cycle for NH3 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 5
INTRODUCTION +Remark: - Temperature after compression is 140oC - That high temperature can damage oil, or refrigerant… - Compressor work increase 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 6
INTRODUCTION + The reason why to use two stage system: - A significant fraction of industrial refrigeration plants operate with a large difference between evaporating and condensing temperatures temperatures— perhaps 50° to 80° C (100° to 150°F). This large temperature lift imposes both problems and opportunities for the system. - An opportunity is to use multistage compression, i which hi h although lth h increasing i i th first the fi t cost over single-stage compression, also alleviates (solve) some problems and can save on total compressor power. 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 7
Two stage cycle, 1 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + This is the simplest among 2 stage cycles. Compressed vapour from low-stage was cooled by water to condensing temperature 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 8
Two stage cycle, 1 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + Advantage compared to 1 stage cycle: - Low discharge temperature-> more safety,safety reliable, high efficiency - Low compression p work + Disadvantage: - High cost and complex system for performance -> Best B using i forf Freon F refrigerant fi 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 9
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + Principle : G2 (G2-G1) G1 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 10
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + Advantage and disadvantage compared to 1 stage cycle: - a specific refrigeration effect increase - a specific p work of compression p decrease - Low discharge temperature-> more efficiency over one stage cycle + Application: A li i apply l for f Amoniac A i andd Freon F 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 11
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + Refrigeration cycle calculation: Firstly, give Qo, to, tk ; then we must find out mass flowrate of low stage, high stage, condenser heat ejectionQk, COP… Mass and heat balance for intercooler: G2.i7=G1.i10 + (G2-G1).i8 -> G2 = G1.(i (i8-ii10)/(i8-ii7) In order to find out 4 state, we have to use mixing equation: (G2-G1).i8 + G1.i3 = G2.i4 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 12
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat + Diagram often applied in industrial system: a Diagram 1 : a. G2 4 5 G2 –G1 G1 Firstly, giving suction temperature of high stage compressor =>G1, G2 by using mixing equation 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 13
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat b. Diagram 2 : - Give t7, Qo, t8=ttg+3~5K - Find out G1 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 14
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat Xem clip 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 15
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 16
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat Using mass and heat balance for subcool tank: (G2-G1).(i ) (i7-i6) = G1.(i (i5-i8) -> G2 ? Mixingg equation q at 3 p point: (G2-G1).i7 + G1.i2 = G2.i3 -> Find out i3 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 17
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat c. Diagram 3 : 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 18
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat d. Diagram 4: - Give t10=ttg+5K ; liquid-vapour superheat -> t9 ((t8 is saturated vapour p or initially yggiven t8) 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 19
Two stage cycle, 2 expansion valve, partial pa t a interstage te stage de de-superheat supe eat Heat balance equation: + For liquid-vapour heat exchanger: (G2-G1).(i9-i8) = G2.(i5-i6) -> G2/G1 = ((i9-i8))/(i ( 9-i8-i5+i6) ((1)) + For subcooler: G1.(i6-i10) = (G2-G1).(i8-i7) -> G2/G1 = (i8-ii10)/(i8-ii7) (2) (1)&(2) -> i6 =? Note : i6=i7 12/2015 Chapter 5 : Multi-Stage System - ThS.Nguyễn Duy Tuệ 20