Bài giảng Chapter 4: Single stage cycle

Sau khi học xong "Bài giảng Chapter 4: Single stage cycle" sinh viên có thể Analyze and perform cyclic calculations for refrigerati on cycle and others; Analyze and perform cyclic calculations for standard vapou r compressi on refrigeration systems;... Cùng tìm hiểu để nắm bắt nội dung thông tin tài liệu.
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Bài giảng Chapter 4: Single stage cycle CHAPTER 4: SINGLE STAGE CYCLE12/2015 Chapter 4 : Single stage cylce 1 OBJECTIVES After this Aft thi charpter, h t student t d t can : - Analyze and perform cyclic calculations for C Carnot t refrigeration fi ti cycle l andd others th - Analyze and perform cyclic calculations for standard t d d vapour compression i refrigeration fi ti systems - Analyze A l advantage d t and d disadvantage di d t off some refrigeration cycles12/2015 Chapter 4 : Single stage cylce 2 CONTENTS CARNOT REFRIGERATION CYCLE STANDARD VAPOUR COMPRESSION REFRIGERATION SYSTEM (VCRS) SUBCOOLING AND SUPERHEATING CYCLE LIQUID – SUCTION HEAT EXCHANGER12/2015 Chapter 4 : Single stage cylce 3 CONTENTS ACTUAL STANDARD VAPOUR COMPRESSION REFRIGERATION SYSTEM12/2015 Chapter 4 : Single stage cylce 4 REFERENCES [1] . 4O LESSONS ON REFRIGERATION AND AIR CONDITIONING FROM IIT KHARAGPUR. ( Useful t i i training material t i l for f mechanical h i l engineering i i students/college, or reference for engineer ) - Indian I tit t off Technology Institute T h l (IIT) [2]. Kỹ thuật lạnh cơ sở - Nguyễn Đức Lợi12/2015 Chapter 4 : Single stage cylce 5 CARNOT REFRIGERATION CYCLE 1. Definition: Carnot refrigeration cycle is a completely y , hence is used as a model of reversible cycle, perfection for a refrigeration cycle operating p between a constant temperature heat source and sink. It is used as reference against which the real y cycles are compared. p12/2015 Chapter 4 : Single stage cylce 6 CARNOT REFRIGERATION CYCLE 2. Description p : Refer to (page 155, [1]) :-Process P 4-1 4 1 : vaporization i iin evaporator-Process P 1-2 1 2 : compression iin compressor-Process P 2-3 2 3 : condensing d iin condenser-Process P 3-4 3 4 : expansion i iinturbin12/2015 Chapter 4 : Single stage cylce 7 CARNOT REFRIGERATION CYCLE qc − qe = wnet12/2015 Chapter 4 : Single stage cylce 8 CARNOT REFRIGERATION CYCLE Refer (p (page g 155,, [[1]) ]) :12/2015 Chapter 4 : Single stage cylce 9 CARNOT REFRIGERATION CYCLE The Coefficient of Performance ((COP)) is g given by: y - The COP of Carnot refrigeration g cycle y is a function of evaporator and condenser temperatures y and is independent only p of the nature of the working g substance. - From Carnot’s theorems,, for the same heat source and sink temperatures, no irreversible cycle g can have COP higher than that of Carnot COP.12/2015 Chapter 4 : Single stage cylce 10 CARNOT REFRIGERATION CYCLE 3. Practical difficulties with Carnot refrigeration g system: gp - During process 1-2,, a mixture consistingg of liquid q and vapour have to be compressed isentropically in p the compressor -> compressor p will be damaged g - Using a turbine and extracting work from the y system during g the isentropic p expansion p of liquid q refrigerant is not economically feasible, particularly in case of small capacity p y systems. y12/2015 Chapter 4 : Single stage cylce 11 CARNOT REFRIGERATION CYCLE - This is due to the fact that the specific p work output (per kilogram of refrigerant) from the turbine is g given by: y - The specific p volume of liquid q is much smaller compared to the specific volume of a vapour/gas, p from the turbine in case of the liquid the work output q will be small. In addition, the inefficiencies of the turbine -> then the net output p will be further reduced.12/2015 Chapter 4 : Single stage cylce 12 Standard Vapour Compression Refrigeration System (VCRS) In practical p considerations,, the Carnot refrigeration system need to be modified: - Dryy compression p with a single g compressor ...