Cascade Refrigeration System 2016

AProject ReportonTHERMODYNAMIC ANALYSIS OF VAPOUR CASCADE REFRIGARATION SYSTEM USING R-12 & R-404A (ALTERNATIVE REFRIGARENT)

Submitted by: Srikanta Biswas, Roll No-11800712053 Biplab Khan, Roll No-11800713067 Somnath Dey, Roll No-11800712051 Sayan Sarbajna, Roll No-11800712049 Shovan Ghosh, Roll No-11800712050Surovita Santra, Roll No 11800713077 Guided by: Santanu Banerjee(Associate Professor)Department of Mechanical EngineeringBirbhum Institute of Engineering & Technology, SURI

CERTIFICATE OF APPROVAL

This is to certify that the project report entitled THERMODYNAMIC ANALYSIS OF VAPOUR CASCADE REFRIGARATION SYSTEM USING R-12 & R-404A (ALTERNATIVE REFRIGARENT), being submitted by Srikanta Biswas (11800712053), Biplab Khan (11800713067), Sayan Sarbajna (11800712049), Shovan Ghosh (11800712050) , Surovita Santra (11800713077) , Somnath Dey (11800712051) in the partial fulfilment of the requirement for the award of the degree of B. Tech in Mechanical Engineering, is a record of bonafide research carried out by them at the Department of Mechanical Engineering, Birbhum Institute of Engineering and Technology, Suri under our guidance and supervision.

------------------------------------------- --------------------------------------Santanu Banerjee Prof. TITOV BANERJEE(Associate Professor) (Head of The Mechanical Department of Mechanical Engineering Engineering Department)

-------------------------------------------Dr. SUBHASISH BISWAS(Director) Birbhum Institute of Engineering and Technology, Suri

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ACKNOWLEDGEMENT

We would like to express our sincere gratitude to our guide Santanu Banerjee for their invaluable guidance and steadfast support during the course of this project work. Fruitful and rewarding discussions with him on numerous occasions have made this work possible. It has been a great pleasure for me to work under his guidance.We would like to express our sincere thanks to all the faculty members of Mechanical Engineering Department for their kind co-operation.We would like to acknowledge the assistance of all my friends in the process of completing this work.Finally, we acknowledge our sincere gratitude to our family members for their constant encouragement and support.

______________________(SRIKANTA BISWAS)ROLL NO. 11800712053

________________________(SOMNATH DEY)ROLL NO. 11800712051

_________________________(BIPLAB KHAN)ROLL NO. 11800713067

_________________________(SUROVITA SANTRA)ROLL NO. 11800713077

______________________(SHOVAN GHOSH)ROLL NO. 11800712050

________________________(SAYAN SARBAJNA)ROLL NO. 11800712049

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CONTENT

TOPICPAGE NO

List of Tables and List of FiguresNomenclature56

CHAPTER 1: INTRODUCTION Refrigeration Refrigerant Classification of Refrigerant Properties of Ideal Refrigerants Designation Few Refrigerants and Their Use Effect of Refrigerant Need of Alternative Refrigerant Alternative Refrigerant COP And TR7-14

CHAPTER 2: VAPOUR CASCADE REFRIGERANT SYSTEM15

CHAPTER 3: LITERATURE REVIEW16-25

CHAPTER 4: MATHEMATICAL FORMULATION Description of proposed model Thermodynamics of the system26-27

CHAPTER 5: RESULTS AND DISCUSSION Values of different parameters Effect of evaporator temperature on COP Effect of evaporator temperature on compressor work Effect of evaporator temperature on refrigerating effect Effect of evaporator temperature on exegetic efficiency.28-29

CHAPTER 6: CONCLUSION AND SCOPE OF FUTURE WORK Conclusion Scope Of Future Work30

CHAPTER 7: REFERENCES31-33

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List of figure

Figure noDescriptionPage no.

1.1T-S Diagram Of Cascade Refrigeration2

1.2P-H Diagram Of Cascade Refrigeration3

1.3Production Of Halogenated Refrigerant8

1.4Ozone Depletion Potential Of Pure CFC And HCFC Refrigeration9

1.5Global Warming Of Pure Cfc And HCFC9

1.6Global Warming Of Pure HCFC Refrigerants9

1.7Global Warming Of HFC Mixtures9

1.8Schematic Diagram Of A Two Stage Cascade Refrigeration System11

5NomenclatureR 12/CFC 12Dichlorodifluoromethane (Freon 12)R22Chlorodifluromethane

R134a1,1,1,2-TetrafluoroethaneR717Ammonia

R143a1,1,1-TrifluoroethaneR1232,2-Dichloro-1,1,1-trifluoroethane

R152a1,1-DifluoroethaneR407CBlend of R32, R125 and R134a

R404ABlend of R125, R143a and R134aR410ABlend of R32 and R125

R417ABlend of R125, R134a and R600R744Carbon Di-Oxide

R161FluorethaneR507Blend of R125 and R143a

R125PentafluoroethaneR718Water

R600ButaneR502Blend of R22 and R115

R290PropaneR11Trichlorofluoromethane

R600aIsobutaneHCFCHydrochlorofluorocarbon

R422BBlend of R125, R134a and R600aHFCHydrofluorocarbons

GWPGlobal warming potentialCFCChlorofluorocarbon

GHGGreenhouse gasUVUltra violet

TRTon of refrigerationODPOzone depletion potential

COPCoefficient of performanceQ1Heat absorbed

Q2Heat rejectedWCCompressor work

P1Condenser pressureP2Evaporator pressure

hEnthalpy in kJ/kgSEntropy in kJ/kg-k

CConstantTTemperature

vSpecific volume in m3/kgXDryness fraction

1Evaporator outlet2Compressor outlet

3Condenser outlet4Expansion valve outlet

0SurroundingsKTemperature in Kelvin

HCHydro carbonsBPRButane-Propane-R134a

m.Mass flow rateeExergy loss

wCompressorVValve

cCondenserEEvaporator

IIExergetic efficiencySCompressor isentropic efficiency

VVolumetric efficiency VCCVCCVolumetric cooling capacity

rReference stateETotal heat loss

6Chapter -1INTRODUCTIONRefrigeration is a process of moving heat from lower temperature to higher temperature in controlled conditions. Refrigeration also can be defined as a process of achieving & maintaining a temperature below that of surroundings. Refrigeration has many applications including them the most important is to preserve foods in a low temperature. It also used in industrial, agriculture and many other purposes.Refrigeration system is based on Clausius statement of the 2nd law of thermodynamics. Clausius statement states that: It is impossible to construct a device that operating a cycle, has no effect other than the transfer of heat from a cooler to a hotter body. The devices that provide this help are called refrigeration units & heat pumps. Refrigerator & Heat pump:The operating system of refrigerator and heat pump are reversed. In refrigerator heat transfer from low temperature region to high temperature region. But in heat pump heat transfer from a low temperature medium to high temperature medium.The objective of a refrigerator to remove heat (QL) from the cold medium and the objective of a heat pump is to supply heat (QH) to a warm medium.The performance of a refrigerator and heat pump is expressed as co-efficient of refrigerant (COP) defined asCOPR=cooling effect/work input= QL/W net inCOPHP= Heating effect / Work input= QH/W net inBoth COPR and COPHP can be larger than 1. Component of a Vapour Compression Refrigeration System:There are four essential part of a refrigeration system i.e., compressor, condenser, expansion valve, evaporator.Compressor: the low pressure and temperature vapour refrigerant from evaporator is drawn into the compressor. In compressor it is compressed to a high pressure and temperature vapour. The high pressure and temperature vapour is discharged in the condenser.Condenser: In condenser high pressure and temperature vapour refrigerant condensed and cooled.Expansion Valve: In expansion valve the high pressure and temperature liquid refrigerant is passed to a controlled rate after reducing its pressure and temperature and makes a liquid vapour refrigerant.7Evaporator: It consists of coils of pipes in where liquid vapour refrigerant is evaporates and converted in low pressure and temperature vapour refrigerant. In evaporating the liquid vapour refrigerant absorbs latent heat of vaporization (water, air or brine) which is to be cooled.T-S Diagram of an Ideal Refrigeration Cycle:Process 1-2 Isentropic compression in low temperature Compressor. Process 2-3 P: Constant pressure Heat Rejection in low temperature circuit Process 3-4: Expansion Under Throttling Process, Isenthalpic Process Process 4-1 P: Constant Heat Addition Process Process 1-2: Isentropic compression in high temperature compressor Process 2-3P: Constant pressure Heat Rejection in high temperature circuit Process 3-4: Expansion Under Throttling Process, Isenthalpic Process Process 4-1P: Constant pressure Heat Addition Process P-h Diagram of Ideal Refrigeration Cycle:Process 1-2 Isentropic compression in low temperature Compressor. Process 2-3 P: Constant pressure Heat Rejection in low temperature circuit Process 3-4: Expansion Under Throttling Process, Isenthalpic Process Process 4-1 P: Constant Heat Addition Process Process 1-2: Isentropic compression in high temperature compressor Process 2-3P: Constant pressure Heat Rejection in high temperature circuit Process 3-4: Expansion Under Throttling Process, Isenthalpic ProcessProcess 4-1P: Constant pressure Heat Addition Process8RefrigerantsA refrigerant is defined as any substance that absorbs heat through expansion or vaporization and losses it through condensation in a refrigeration system. The ideal refrigerant would have favourable thermodynamicproperties, benon-corrosiveto mechanical components, and be safe, including free fromtoxicityand flammability. It would not cause ozone depletionor climate change. Since different fluids have the desired traits in different degree, choice is a matter oftrade off. Classification of refrigerantsRefrigerants are classified as follows: Primary refrigerants are those working mediums or heat carries which directly take part in refrigeration system and cool the substance by the absorption of latent heat e.g., Ammonia, Carbon dioxide, Methyl chloride etc. Secondary refrigerants are those circulating substances which are first cooled with the help of the primary refrigerants and are then employed for cooling purposes, e.g., ice, Carbon dioxide etc. These refrigerant cool substances by absorption of their sensible heat. Properties of Ideal RefrigerantsA refrigerant is said to be ideal if it has all of the following properties: -1. Low boiling point and High critical temperature.2. High latent heat of vaporization and Low specific heat of liquid.3. Low specific heat of liquid and Low specific volume of vapour.4. Low specific volume of vapour.5. Non-corrosive to metal.7. Non-flammable and non-explosive, non-toxic.9. Low cost.10. Easy to liquidate moderate pressure and temperature.I l. Easy of locating leaks by suitable indicator, and12. Mixes well with oil. Designation of Refrigerants: -The international designation committee of refrigerants uses Refrigerant or R as the designation followed by certain numbers (e.g., R-21, R-40, R-30, R-744 etc.)A refrigerant followed by a two-digit number indicates that the refrigerant is derived methane base while a three-digit number represents ethane base. 9The general chemical formula for a compound derived from a saturated hydrocarbon is given by as: CaHbFcCldWhere, b + c + d=2a+2,and, a= Number of carbon atoms,b= Number of hydrogen atoms,c= Number of fluorine atoms,d= Number of chlorine atoms,The complete designation of the refrigerant is given by:R (a-1) (b+1) (c)Example: In case of Dichlorodifluoromethane (CCl2F2):a=1, b=0, c=2, d=2So, the designation is: R (1-1) (0+1) (2) i.e., R-12. Few refrigerants and their useA refrigerant is a substance used for refrigeration. The best refrigerant has good thermodynamic properties, is chemically non-reactive, and is safe. Because some refrigerants can cause severe damage to the ozone layer, it was decided in 1992 to make it illegal to release refrigerants into the atmosphere. Refrigerants used in refrigeration systems are as follows:Refrigerant R11R11 is a CFC refrigerant, which means it is made of chlorine, fluorine, and carbon. R11 is typically used in the refrigerators found in office building and hotel air conditioning systems because it allows large refrigerators to cool large amounts of water at low costs. In the past, when air would leak into R11 systems, that air had to be purged, and usually some of the refrigerant would be lost. Through newer technological advances and better maintenance, less R11 has been lost in these large refrigerators. In view of the global environmental problem resulting from global warming, depletion of the ozone layer, this CFC refrigerant is currently being pursued internationally.Refrigerant R22R22 belongs to the HCFC group of refrigerants, which means it's made of hydrogen, chlorine, fluorine, and carbon. R22 is the most common refrigerant on the market as it is used in most residential and commercial air conditioning systems and even in some large centrifugal refrigerators. R22 is also pursued internationally for its GWP (Global warming potential) and ODP (Ozone depletion potential). Although it is a popular refrigerant, it will be phased out in new refrigeration equipment that is made in 2010, and it will stop being produced in 2020. 10Refrigerant R422BR422B is a refrigerant made by ICOR to be similar to the R22 refrigerant. Like the R22 it is made for residential and commercial air conditioners. R422B is an HFC refrigerant, which means that it is made of hydrogen, fluorine, and carbon. This hydrogen and carbon in refrigerant helps oil return in those refrigeration systems that have mineral oil or alkyl benzene in them. R422B won't mix with these oils, but the hydrogen and carbon allows the oil to thin out and keep moving in these systems.Refrigerant R717R717 is the refrigerant free from any halogen atoms. It is named as ammonia. The ammoniawater absorption refrigerator has been used widely in refrigeration and air-conditioning applications. R717 has a wide range of applications. It is particularly suited to working in the range approximately 0C to -30C and hence is widely used for food preservation. This includes the chilling of liquids such as milk, beer and soft drinks, enlarge cold storage facilities, meat processing and packing plants, large ice-making plants and commercial refrigeration. Other common applications include large air conditioning systems (refrigerators), industrial heat extraction and ice rinks. An advantage of using R717 is its zero ozone depletion potential and zero global warming potential.Refrigerant R718R718 is nothing but water. Water can be used as a refrigerant in refrigerators without any safety measurement which is cheap, environmentally neutral. Its maintenance cost is very low since leakages can be accommodated from the system. There are no extra demands for safety measures or for skilful operators and no special requirements concerning the installations components. But the only disadvantage is higher investment cost (about 200% of a conventional water refrigerator) and bigger overall dimension.

Environmental Effect of RefrigerantsThe halogenated refrigerants are a family of chemical compounds derived from the hydrocarbons (methane and ethane) by substitution of chlorine and fluorine atoms for hydrogen. The emission of this type of halogen atoms (F, Cl etc.) are responsible for huge environment impact. Molina and Rowland [2] first discovered the ozone depleting properties of CFC and HCFC and by their global warming potential led to the Montreal Protocol (1987) and the London and Copenhagen amendments (1990, 1992) [3], which is responsible for the end of production of CFCs by the end of 1995 and of HCFCs by 2030. As figure 1.3 shows, the production of CFCs and HCFCs has fallen dramatically in the last few years.

11Ozone layer depletionODP due to artificial chemicals into the atmosphere was the first major environment impact that was the after effects refrigeration process. The stability of chlorine based refrigerants is enough to reach the stratosphere, where the atoms of chlorine act as a catalyst and destroy the stratospheric ozone layer (which protects the earth surface from direct UV rays). About 90% of the ozone exists in the stratosphere layer of earth surface. The first phase out schedule for the harmful refrigerants formulated by the Montreal protocol (1987) and was made stringent during the follow-up international meetings. The ODP values of pure CFC and HCFC refrigerants are shown pictorially in the figure [1.3]

Global warming potentialGWP is the second major environment impact. It is due to the absorption of infrared emissions from the earth, causing an increase in global earth surface temperature. While solar radiation at 5800 K and 1360 W/m2 arrives the earth, more than30% is reflected back into space and most of the remaining radiation passes through the atmosphere and reaches the ground. This solar radiation heats up the earth, which approximately as a black body, radiate energy with a spectral peak in the infrared wavelength range. This infrared radiation cannot pass through the atmosphere because of absorption by GHG including the halogenated refrigerants. As a result, the temperature of atmosphere increases, which is called as the global warming. During the formulation of Kyoto protocol, countries around the world have voluntarily committed to reduce the GHG emissions. HFC refrigerants have relatively large values of atmospheric lifetime and GWP compared to chlorine based refrigerants. The GWP values of pure and mixed refrigerants are illustrated in figure. [3] 12 The Need of Alternative RefrigerantA refrigerant is a substance used in a heat cycle usually for enhancing efficiency, by a reversible phase transition from a liquid to a gas. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulphur dioxide, and non-halogenated hydrocarbons such as propane. R134a is an inert gas used primarily as a high-temperature refrigerant for domestic refrigeration and automobile air conditioners. Contact of R134a with flames or hot surfaces have toxic and hazardous effect on the humans and environment. So in this paper, a review of available alternative refrigerants and their physical and chemical properties have been done. Selection of efficient, eco-friendly and safe refrigerant for future has been attempted in this paper through discussions.It is evident that societies around the globe are demonstrating growing interest and concern for the environment. In the area of automotive air-conditioning systems, the technology has evolved to a reliance on HFC-134a as a stable non-corrosive, non-toxic refrigerant that avoids adverse impact on the ozone layer. More recently, the industry has been involved in assessment of refrigerants other than HFC-134a, motivated primarily by efforts to minimize greenhouse gas emissions. Typical candidates include carbon-dioxide as well as members of the hydrocarbon group (usually, propane and isobutane).The present study was undertaken to assess the relative advantages of these alternative refrigerants, with specific emphasis on carbon-dioxide systems. To do so, the study employs the Total Environmental Warming Impact (TEWI) index as a holistic measure of the system. The analysis was undertaken with carefully defined conditions involving two standard production vehicles representing small and mid-size cars. The simulations were run to represent vehicle and air-conditioning use in six cities around the globe using standard vehicle operation cycles. Key assumptions such as refrigerant emission were made using a range of values cited in references. In the case of CO2 systems, given lack of adequate on-road measurements, the effect of approach temperature was also evaluated with a range of values.Due to several environmental issues such as ozone layer depletion and global warming and their relation to the various refrigerants used, the selection of suitable refrigerant has become one of the most important issues in recent times. Replacement of an existing refrigerant by a completely new refrigerant, for whatever reason, is an expensive proposition as it may call for several changes in the design and manufacturing of refrigeration systems. Hence it is very important to understand the issues related to the selection and use of refrigerants. In principle, any fluid can be used as a refrigerant. Air used in an air cycle refrigeration system can also be considered as a refrigerant. However, in this lecture the attention is mainly focused on those fluids that can be used as refrigerants in vapour compression refrigeration systems only. 13

Coefficient of Performance (COP)The performance of a refrigeration system is expressed as Co-efficient of Performance (COP). It is defined as the ratio of heat absorbed by the refrigerant while passing through the evaporator to the work input required to compress the refrigerant in the compressor; i.e. it is the ratio between heat extracted and work done (in heat units). COP is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions. The COP may exceed 1, because, instead of just converting electricity to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required.C.O.P. = Rn/WWhere, Rn= net refrigerating effect, and W= work expended in the machine during the same interval of time to time.Ton of Refrigeration (TR)A ton of refrigeration or TR is a unit of power used in some countries (especially in North America) to describe the heat-extraction capacity of refrigeration and air-conditioning equipment. It is originated from the rate at which heat is required to be removed to freeze one ton of water and at zero degree centigrade in 24 hours. 1 TR is equivalent to removal of 200 BTU of heat per minute and in S.I. units it is rounded off to 3.5 kJ/s (kW) or 210 KJ/min. Many manufacturers also specify capacity in BTU/hr especially when specifying the performance of smaller equipment.

14 Chapter 2Vapour Cascade Refrigeration SystemCascade system was first used in 1877 by Pick let. Cascade system is just similar to the binary-vapour cycle used for the power plants. In a binary vapour cycle, a condenser for mercury works as a boiler for water as a boiler for water. Similarly, in the cascade system the condenser for low temperature cycle works as an evaporator for the high temperature cycle. In cascade system, a series of refrigerants with progressively lower freezing points is used in a series of a single stage units. A two stage cascade system using two refrigerants is shown in figure and its corresponding p-h and T-s diagram are shown in fig respectively

In this system a cascade condenser serves as an evaporator for high temperature cascade condenser system and a condenser for the low temperature cascade system the only useful refrigerating effect is produced in the evaporator of the low temperature cascade system. Thus it permits the use of two different refrigerants, with thermodynamic properties favourable for the two temperature ranges. Further, the lubricating oil from one compressor cannot be carried away to another compressor. The temperature difference in low temperature cascade condenser and high temperature cascade evaporator is known as temperature overlap.The low temperature cascade system uses a refrigerant with low boiling temperature (such asR-13 or R-13BI).There are few advantages of cascade refrigeration system. The followings are the advantages of cascade refrigeration systemAdvantages of cascade refrigeration system1. It also reduces the lubricating problems since the lubricant associated with each refrigerant has to withstand a temperature range not more than 60oC, whereas in multistage system, the lubricant can have to be working over temperature range of order of 105oC.2. Performance of cascade system can be improved through reducing temperature difference for heat transfer in the evaporator, condenser and cascade condenser, compare to larger compressors.3. The performance of cascade system can be enhanced by reducing the temperature difference for heat transfer in evaporator, condenser and cascade condenser, and compare to larger compressors.4. It avoids the problem of sub-atomic pressure which will octet in the evaporation if a single fluid is used in both the stages.5. Using a cascade system power consumption can be reduced through about 9.5%. 15 Chapter 3LITERATURE REVIEW[1] Different researchers have been carried out them researches on vapour compression refrigeration system, cascade refrigeration system and used different refrigerants for the performance analysis of the system and the refrigerants. Molina et al clarified stratospheric sink for Chlorofluoromethanes chlorine atom-catalysed destruction of ozone was that the Chlorofluoromethanes were added to the atmosphere in steadily increasing amounts. Those components are chemically inert band may remain in the atmosphere for many years. Two Chlorofluoromethanes CF2Cl2 and CFCl3, have been detected. Both CFCl3 and CF2Cl2 absorbed the radiation of ultraviolet. As a result, they have calculated based on reactions in the gas phase, this research had been supported by the US Atomic Energy Commission.[2] Environmental impacts of Halogenated Refrigerants had been clarified by Sudipta Paul, Achinta Sarkar, and Bijan Kumar Mandal. A certain percentage of the vapour compression based refrigeration, air conditioning and heat pump systems continue to run on halogenated refrigerants due to its excellent thermodynamic and thermo-physical properties along with the low cost.On the other hand, the halogenated refrigerants have adverse environmental impacts such as ozone layer depletion potential and global warming. This paper reviews the various experimental and theoretical studies carried out around the globe with environment friendly alternatives such as hydrocarbons (HC), hydrofluorocarbons (HFC) and their mixtures, which are going to be the promising long-term alternatives.CFCS and HCFCS are used as alternative refrigerant. Natural refrigerant is mainly used. Natural refrigerants are being used for a long time. HC mixtures and R152a are found to be better substitutes for R12 and R134a in domestic refrigeration sector. R290, R1270, R290/R152a, R744 and HC/HFC mixtures are found to be the best long-term alternatives for R22 in air conditioning and heat pump applications.[3] The data summary of the Refrigerant was explained by JAMES M.CALM and GLENN C.HOURAHAN, There were many refrigerants but R-12 was the most useful refrigerant. The chemical formula indicates the molecular makeup of the single compound refrigerants. There were LFT is the lowest concentration which the refrigerant burns in air. The heat of combustion is an indicator of how much energy the refrigerant released at the time of burning. After making the data summary they had decided to change when newer measurement was made for both specific and different chemical.[4] Experimental study of new refrigerant mixtures to replace R12 in domestic refrigerators was clarified by B. Tashtoush, M. Tahat, M.A. Shudeifat. After the experiment they had decided to change the R-12 with the hydrocarbon /hydrofluorocarbon refrigerant mixtures. The results show that butane /propane /R134a mixtures provide excellent performance parameters, such as coefficient of performance of refrigerator compression power, volumetric efficiency, condenser duty, compressor discharge pressure and temperature, relative to a 210 g charge of R12. In addition, the results support the possibility of using butane /propane /R134a mixtures as an alternative to R12 in domestic refrigerators, without the necessity of changing the compressor lubricating oil used with R12. On the experimental study, R12 and BPR(M) mixtures were tested under the same operating conditions using a domestic refrigerator, designed originally to work with R12.As a result it was found that domestic refrigerator originally designed to work with R12, this refrigerant can be replaced successfully by the BPR(80) mixture without changing the lubricating oil or replacing the condenser. 16 [5] Performance of mixture refrigerant R152a/R125/R32 in domestic air-conditioner had been explained by Jiangtao Wu, Yingjie Chu, Jing Hu, Zhigang Liu. The new mixture could be regard end as a most likely drop-in substitute for R22 in many applications. The flammability of this ternary blend was also studied with an explosion apparatus to prove that it could be used safely. For the thermodynamically analysis they determined the optimal mass ratio, the thermodynamic properties and refrigeration performance of the new mixture with different mass ratios range from 1% to 98% of each component on a step of 1% were calculated. According to the measurement procedure described above, the refrigerant performance of R22, R407C and ternary blend R152a/R125/R32 with eight different mass ratios were tested. The intermediate temperature of evaporator, inlet and outlet temperature of compressor, condenser and evaporator were also measured. As a result, we can say that new mixture refrigerant, R152a/R125/R32 with a mass ratio of 48/18/34, was provided in this work as an alternative to R22, which was widely used in domestic air-conditioner nowadays and will be restricted to use in the future.[6] For the The performance of propane/isobutane mixtures in a vapour-compression refrigeration system Mr. R.N.Richardson and Mr. J.S.Butterworth had announced that the Hydrocarbons such as propane (R290, C3Hs) and butane (R600, C4Hao) were used as refrigerants before the advent of CFCs, although in the open systems.If the system is designed such that the saturation pressure is always greater than atmospheric, the danger of a potentially flammable mixture forming within the circuit should not arise. There remains, of course, the possibility of leakage, but a significant loss would be required to produce a flammable concentration in the immediate vicinity of the leak.A fully instrumented experimental apparatus was designed to simulate the operation of a domestic vapour compression system while maintaining controlled evaporation and condensation conditions. For the experiment using of R12, propane and a range of propane/isobutane mixtures with proportions around 50%. The system was purged with dry nitrogen gas and then send it to purging, evacuating.Evacuating the hydrocarbons poses no danger provided a 'dry' diaphragm-type pump is used and the exhaust is vented to atmosphere.[7] On the basis of Simulation of vapour compression Refrigeration cycle using HFAC134 and CFC12 was presented by QIYU CHEN and R.C.Prasad. After analysing the total fact by computer simulation depends upon the fluid property and Thermo-hydraulic property HFC134 and CFC12 ware developed. Result indicated that the COP for HFAC134 is slightly lower than CFC12 system and the power required for a HFAC134.From the simulation of vapour compression Refrigeration cycle we got various thermodynamics properties, thermos physical properties, pressure loss in the evaporator, the condenser and exergy loss for HFAC134 and CFC12 system.The COP of vapour compression Refrigeration cycle is an important system. It expressed by COP=Q/W [Q is the refrigeration effect]. For constant cooling load the cop is inversely proportional to the compressor work W.W=m (h2-h1). [Here (h2-h1) is the enthalpy difference from the actual cycle] mass flow rate (m) is the refrigerant for a given refrigeration effect is obtained from m=Q/ (h2-h1). The exergy loss evaluated the thermodynamics performance of a system. The exergy loss analysis is based on e= (h-h0)-T0(s-s0)Depends upon the COP the power required and exergy loss the system with HFC134a shows slight detrition in comparison to CFC12 system. For the same cooling rate, the 3 % of increasing is effectible. If the cooling rate kept constant. And increased compressor work result in a reduce COP of the using HFC134a. 17[8]. Kim and Kim investigated the performance of an auto cascade refrigeration system using zeotropic refrigerant mixtures of R744/R134a and R744/R290. The performance was evaluated by both experiments and computer simulations for various mass fractions of R744 and several operating conditions. The performance test and simulation showed that the compressor power increased when inlet temperature of the secondary heat transfer fluid to condenser was increased, whereas, the refrigeration capacity and COP decreased and as the mass fraction of R744 was increased, cooling capacity and compressor power increased with the decrease in COP. In their study, they also found that the auto cascade refrigeration cycle has a merit of low operating pressure as low as that in a conventional vapour compression refrigeration cycle. They concluded that natural refrigerants or HFC refrigerants with relatively small amount of charge could be used as a refrigerant in the auto cascade refrigeration system. They also mentioned that lower COP of auto cascade refrigeration cycle was a disadvantage, and the way to improve it should be sought in the future.[9] Kilicarslan et al. presented an experimental investigation and theoretical study of a different type of two-stage vapour compression cascade refrigeration system using R134 as the refrigerant. When the calculated refrigeration mass flow rate of single stage systems RU2 was compared with the experimental result, it was observed that the predictions of theory and experiment results were in close agreement. It was also observed that the coefficient of performance in the cascade system was higher than in the single stage system. There was no benefit from using the cascade system if the economy was taken into consideration, because the different refrigeration systems had to be operated simultaneously and the power to drive both compressors was high.[10] Xuan and Chen experimentally tested HFC161 mixture (HFC161, HFC125 and HFC143a (10/45/ 45 wt. %)) as an alternative refrigerant to R502. Their results revealed that the new refrigerant could achieve a high level of COP than R404A and R507 and could be considered as a promising retrofit refrigerant to R502.[11] Wongwises and Chimres presented an experimental study on the application of hydrocarbon mixtures to replace HFC134a in a domestic refrigerator. The author used a refrigerator designed to work with HFC134a in the experiment. The investigated hydrocarbons used in the work were propane (R290), butane (R600) and isobutane (R600a). The experiments were conducted with the refrigerants under the same no load condition at a surrounding temperature of 25C to record consumed energy, compressor power and refrigerant temperature and pressure at the inlet and outlet of the compressor. The same experimental data as well as the distributions of temperature at various positions in the refrigerator were analysed. The experiment was carried out by dividing the refrigerant mixtures into three groups of the mixture of three hydrocarbons, the mixture of two hydrocarbons and the mixture of two hydrocarbons and HFC134a. It was concluded from the result that the mixture of propane and butane of 60% and 40% was the most appropriate alternative refrigerant to HFC134a.[12] Wongwises et al experimentally investigated the application of various hydrocarbon mixtures such as propane (R290), butane (R600), and isobutane (R600a) to replace HFC134a in automotive air conditioners. From the experimental results they concluded that the investigated mixture could successfully replace HFC134a in automotive air-conditioner.[13] Arora and Kaushik made an energy and exergy analysis of R502, R404A and R507A in an actual vapour compression cycle. They observed that the COP and the exergetic efficiency for R507A were better than that for R404A at condenser temperatures between 40C and 55C. Both the refrigerants showed 4-17% lower values of COP and exergetic efficiency than R502 for the same condensing temperature. It was also noted that the increase in dead state temperature had a positive effect on exergetic efficiency. COP and exergetic efficiency of both R404A and R507A improved by sub cooling of condensed liquid refrigerant and the reversed happened when effectiveness of liquid vapour heat exchanger was increased from 0 to 0.1.In that case R507A had better performance compared to R404A.[14] Mohanraj et al developed a computer program in which evaporator temperature, condensing temperature, compressor specifications and properties of various refrigerants were considered for investigation as an input data. They found that except for flammability, R152a, R600 and R600 with negligible GWP compared to R134a were best alternative option. They also stated that R290 and R1270 could not be used as alternatives due to their high operating pressures compared to R134a. R152a will reduce the indirect global warming due to its higher energy efficiency. R152a offer many desirable characteristics such as low operating pressure, mass flow rate, and higher COP by about 9%, 40% and 79% respectively. R152a had approximately the same volumetric cooling capacity (VCC) with respect to R134a.[15] Dalkilic et al theoretically studied a traditional vapour-compression refrigeration system using different refrigerant mixtures (HFC134a, HFC152a, HFC32, HC290, HC1270, HC600, and HC600a) for various ratios and their results were compared with possible alternatives (CFC12, CFC22, and HFC134a). Based on various evaporating temperatures, the effects of refrigerant type, degree of sub cooling, and superheating on the refrigerating effect, coefficient of performance and volumetric refrigeration capacities were also investigated. Theoretical results showed that the alternative refrigerants have a slightly lower performance coefficient (COP) than CFC12, CFC22, and HFC134a for the condensation temperature of 50 C and evaporating temperatures ranging between 30 C and 10 C, while the refrigerant blends of HC290/HC600a (40/60 by wt. %) & HC290/HC1270 (20/80 by wt. %) were found to be the most suitable alternatives tested for R12 and R22 respectively. For a constant condensing temperature in this analysis it was found that with increasing in evaporating temperature the COP of the system increases.[16] Reddy et al performed exergetic analysis of a vapour compression refrigeration system. The effect of condenser temperature, evaporator temperature, vapour liquid heat exchanger effectiveness, sub cooling and superheating on several refrigerants were determined taking COP and exergetic efficiency of the system as parameters. During the analysis, it was found that the condenser and evaporator temperatures have considerable effects on COP and exergetic efficiency of the system. It was also found that R407C refrigerant has poor performance, whereas R-134a has the highest performance in all respect. The results have similarities with reports presented by Mohan raj et al. (2008) & Sen can et al (2006).[17] Bolaji et al compared the exergetic performance of a domestic refrigerator using two eco- friendly refrigerants (R134a and R152a) with the harmful refrigerant R12. The effects of evaporator temperature on the coefficient of performance (COP), exergy flow destruction, exergetic efficiency and efficiency defect were experimentally investigated. The COP obtained using R152a was very close to that of R12 with only 1.4% reduction, while that of R134a was significantly low with 18.2% reduction. Higher exergetic efficiency and consistently better (lower) overall efficiency defect were obtained in the case of R152a in the system. The highest efficiency defects were obtained using R134a as refrigerant. The experiment showed it is better using R152a than using R12 and R134a as working fluids.[18] Bolaji et al worked on the performances of a vapour compression refrigeration system using three ozone-friendly refrigerants (R32, R152a and R134a). It was found that R152a has zero Ozone Depletion Potential (ODP) and very low Global Warming Potential (GWP) & could be used as a replacement for R134a. The average COP of R152a is higher than those of R134a and R32 by 2.6 and 17.6%, respectively. The vapour pressure of R134a was nearly the same with R152a but lower than that of R32 by 37.2%. 19Heavy compressor is required for using R32 as the mean pressure ratio of R32 was found 25.8% higher than that of R134a, while R152a had 2.6% lower than that of R134a. It was also found that the condenser heat load of R152a is close to that of R134a and the VCC of R32 is lower than that of R134a by 25.2%.[19] K Mani et al improved a vapour compression refrigeration system by using a new refrigerant mixture (R290/R600a) as drop-in replacement of CFC12 and HFC134a. It was found that R290/R600a (68/32 by wt %) mixture was higher in refrigerating capacity than R12 in the range of 19.950.1% in the lower evaporating temperatures and 21.228.5% in the higher evaporating temperatures and it was also higher in the range 28.687.2% in the lower evaporating temperatures and 30.741.3% in the higher evaporating temperatures than R134a. Energy consumption of R290/R600a (68/32 by wt %) mixture was higher in the range 6.817.4% than R12 and 8.9 20% than R134a. He also showed that the discharge temperature and discharge pressure of R290/ R600a (68/32 by wt %) mixture was nearly equal to those of R12 and R134a.[20] Hammad et al studied the performance parameters of a domestic refrigerator using four ratios of propane, butane and isobutane (100% propane; 75% propane, 19.1% butane, 5.9% isobutane; 50% propane, 38.3% butane, 11.7% isobutane and 25% propane, 57.5% butane, 17.5% isobutane.) As possible alternatives to the R-12 refrigerant. The parameters investigated are the evaporator capacity, the compressor power, the coefficient of performance (COP) and the cooling rate characteristics. It was found that the 50% propane mixture is most suitable alternative to R-12 based on both COP and saturated curve match characteristics. No changes were needed and no defects are detected to the refrigerators designed for R-12.[21] Jerald et al used five different configuration of capillaries of diameters 0.033, 0.036, 0.044, 0.050 and 0.30 on a vapour compression refrigeration system retrofitted with zeotropic blend of refrigerant R404a (alternative refrigerant) to identify the optimum diameter of capillary which could be used in the system to give the best performance. The involved parameters were the Evaporator load (Qe), Coefficient of Performance (COP), Work done by the compressor (Wc) and Refrigeration Effect (RE). The results revealed that using the zeotropic blend R404a provided better cooling capacity, faster pull down time and better miscibility of oil than R134a which resulted in the better efficiency in the system. For zeotropic blends the amount of refrigerant charged was just 600 Gms. When compared to 1kg of R134a to attain the same cooling capacity of the system and the energy consumed was also 20% less than that of R12 and R134a. Out of the five capillaries employed in the system, the cooling was comparatively quick with the capillary having the diameter 0.030 (double) than others. The same experimental set up of vapour compression system could be operated with hydrocarbons like propane in future to get better results.[22] This paper firstly presents the ternary near-azeotropic mixture of HFC-161 as an alternative refrigerant to R502. The physical characteristics of this refrigerant is similar to R502. It is eco-friendly. Its ODP is zero & GWP is smaller than those R502, R404A, and R507. In this case a reciprocating compressor is used to perform a vapour compression refrigeration. That reciprocating compressor is used for R404A and it plays a major role in R502. No extra modification is made in the system. By two different working method the experimental result shows that the pressure ratio is nearly equal to the R404A. Under lower evaporative temperature, its COP is almost equal to that of R404A and its discharge temperature is slightly higher than that of R404A, while under higher evaporative temperature, its COP is greater than that of R404A and its discharge temperature is lower than that of the latter. This new refrigerant can achieve a high level of COP and can be considered as a promising retrofit refrigerant to R502.The physical properties of this new mixture such as boiling point, critical temperature, critical pressure and saturation vapour pressure are similar to those of R502. So it can be used as a retrofit refrigerant.

20[23] Exergy analysis was applied to investigate the performance of a domestic refrigerator. Originally manufactured to use 145 g of R134a. The highest exergy destruction occurred in the compressor followed by the condenser, capillary tube, evaporator, and superheating coil. There is a method called Taguchi method, which was applied to design experiments to minimize exergy destruction while using R600a. Taguchi parameters were selected by the obtained results from R134a and an experiment using 60 g of R600a, which indicated similar results as R134a. For the design, based on the outcomes R600a charge amount, condenser fan rotational velocity and compressor coefficient of performance were selected. At the optimum condition, the amount of charge required for R600a was 50 g, 66% lower than R134a, but that not brings economic advantages. Compressor modification is strongly recommended to enhance the system. Furthermore, the amount of total exergy destruction in optimum condition (0.025 kW) is 45.05% of the base refrigerator one (0.05549 kW) which confirms the enhancement of the cycle for 54.95%.By using Taguchi design, the optimum condition was found to be R600a charge amount of 50 g, compressor coefficient of performance of 1.82 and condenser fan rotational velocity of 1800. The amount of total exergy destruction in optimum condition is 45.05% of the base refrigerator one.

[24] R134a is the most widely used refrigerant in domestic refrigerators. In India, about 80% of the domestic refrigerators use R134a as refrigerant due to its excellent thermodynamic and thermos physical propertiesR134a has high GWP of 1300. The higher GWP due to R134a emissions from domestic refrigerators leads to identifying a long term alternative to meet the requirements of system performance. In the present work, an experimental investigation has been made with hydrocarbon refrigerant mixture (composed of R290 and R600a in the ratio of 45.2:54.8 by weight) as an alternative to R134a in a 200 l single evaporator domestic refrigerator. The tests were continuously performed under different ambient temperatures (24, 28, 32, 38 and 43 C), while cycling running (ON/OFF) tests were carried out only at 32 C ambient temperature. The results showed that the hydrocarbon mixture has lower values of energy consumption; pull down time and ON time ratio by about 11.1%, 11.6% and 13.2%, respectively, with 3.253.6% higher coefficient of performance (COP).Temperature variation in the evaporator is found to be within 3 K. The miscibility of HCM with POE was found to be good. HCM also reduce the indirect global warming due to its higher energy efficiency. Thus, the reported results prove that the above HCM can be used as an alternative to phase out R134a in domestic refrigerators.

[25] Refrigeration plays a very important role in industrial, domestic, and commercial sectors for cooling, heating, and food preserving applications. This article presents a detailed experimental analysis of 2TR (ton of refrigeration) vapour compression refrigeration cycle for different percentage of refrigerant charge using exergy analysis. Here R22 is used as a working fluid for different operating condition. The calculations are made for COP, exergy destruction, and exergetic efficiency for variable quantity of refrigerant. The present investigation has been done by using 2TR window air conditioner. The losses in the compressor are more pronounced, while the losses in the condenser are less pronounced as compared to other components. The total exergy destruction is highest when the system is 100% charged & it becomes least when it is 25% charged. The average COP is highest when the system is 50% charged and this is because of higher refrigerating effect and reduced compressor work.This is an important tool in explaining the various energy flows in a process and in the final run helps to reduce losses occurring in the system. The system comprises of four components, i.e., compressor, a capillary tube (expansion device), a condenser, and an evaporator and is having a cooling capacity of 24K BTU. The exergy efficiency of the system varies from 3.5 to 45.9% which is mainly due to the variation of evaporator temperature. When the actual requirements are less, the system should be operated with variable refrigerant flow so as to achieve optimum balance between the exergy efficiency and energy saving.

[26] In this study, exergy analyses of vapour compression refrigeration cycle with two-stage and intercooler using refrigerants R507, R407c. Here R404A is carried out. The coefficient of performance, exergetic efficiency and total irreversibility rate of the system in the different operating conditions for these refrigerants were investigated. All these are calculated by Solkane program. Its observed that COP increases when evaporator temperature increases for all refrigerants and COP decreases when the condenser temperature increases. 21Irreversibility values attained due to variation of evaporator temperature have reached the highest values in the evaporator when condenser temperature has been kept constant at 35 C in the system which uses each three alternative refrigerants. However, when evaporator temperature has been kept constant at -10 C, irreversibility values calculated due to variation of condenser temperature have reached the highest values in evaporator in each system using R507, R407c and R404a alternative refrigerants. It is observed that total irreversibility rate depends on evaporator temperature change. The procedure applied in this study can be carried out for a number of other refrigerants and actual cycles. So, its concluded that the best way to improve irreversibility can be achieved with determination of optimum operation conditions.

[27] In this paper, the influence of the main operating variables on the energetic characteristics of a vapour compression plant, based on experimental results, is addressed. The experimental tests are performed on a single-stage vapour compression plant using three different working fluids, R134a, R407C and R22. Main experimental results obtained by the performance characteristics followed to analyse the energetic performance are the refrigerating capacity and the power requirements of the reciprocating compressor, presenting and discussing in this work. The evaporating pressure, condensing pressure and superheating degree of the vapour on the energetic performance of an experimental refrigeration plant using three different working fluids has been studied. It follows that the mass flow rate evolution is mainly governed by the compression ratio, and especially by the evaporating pressure.Analysing the refrigerating capacity, and considering the negligible modifications of the specific refrigerating effect, it reaches the conclusion that the mass flow rate evolution becomes the most important influence on the refrigerating capacity behaviour. The refrigeration plant consumption working with R22 tends to decrease more slowly with increasing compression ratios than using the other working fluids. This fact is transferred to the COP, obtaining a smaller value of the COP using R22 than using R407C for high compression ratios.

[28] This paper provides a comparison of the operating performance of three alternative refrigerants for use in a vapour compression refrigeration cycle. The refrigeration capacity and COP of R401A, R290 and R134A were compared with those of R12 when used in a propriety vapour compression refrigeration unit initially designed to operate with R12. The performance of R134a is very similar to that of R12 justifying the claim that it is a drop in replacement for R12 but of the refrigerants tested it gave the poorest performance. When viewed in terms of greenhouse impact however R290 showed the best performance. The cooling capacity of R290 (propane) was the largest of the refrigerants tested, and higher than the original refrigerant R12.R290 represents an attractive alternative to existing CFCs in small domestic refrigerators, subject to correct technical application of operational and safety factors. The refrigerant R401a displayed a level of performance for both capacity and COP. The substitution of this refrigerant would allow the original R12 to be disposed of in an environmentally sensitive way but an economic analysis of a retrofit must compare the projected lifetime service and maintenance costs for the system with the original R12 and R401. R134a is considered to be the preferred HFC replacement for R12. The lubrication requirements make the substitution of this refrigerant less straightforward than the case with R290 and R401a so it would not be the preferred choice unless other circumstances prevented the use of the other refrigerants.

[29] Xu and Clodic conducted an exergy analysis on a vapour compression refrigeration system using R12, R134a and R290 as refrigerants. This experiment was done developing a mathematical model for carrying out exergy analysis. This exergy analysis had been done by the refrigerants or freezers i.e. R12, R134a, and R290 to illustrate various exergy losses in various components and for potential improvements. By this analysis method they had been localized the exergy losses in refrigeration system and reduced them. The exergy losses were mainly occurred in compressor and evaporator in this system. Finally, they got the results that R134a refrigerator is almost efficient than R12 but for freezers R134a and R290 is less efficient than R12. These two refrigerants had some problem i.e. they could not achieve same performance like R12. 22[30] Padmanabhan and Palanisamy conducted an experiment in vapour compression refrigeration system of an air conditioner to replace the refrigerant R22 with few environment friendly refrigerants R134a, R290 & R407c. It is observed that R290 is best refrigerant among the others but it highly flammable. So R407c could be used to replace R22. They also observed that the COP of the system when refrigerant R290 is used was higher than that of other refrigerants and the total irreversibility of the system is higher when R134a is used as main working fluid in the system. They also found that the EE of system is maximum when R290 is used. It had been also observed that those refrigerants are cheaper with zero ODP & moderate GWP compared to R22. But R290 had a better potential. For being highly flammable, R290 cannot be used in a safe manner in refrigeration system & air conditioning purpose and for this R 407c could be used.[31] Lee and SU had been done an experiment on domestic refrigeration system by used isobutane (R600) as a refrigerant. This experiment was done by an experimental set up of vapour compression refrigeration system. The expansion & heat transfer components of the system were capillary tubes & plate heat exchangers respectively and the refrigeration temperature was set about 4C to 10C to simulate the situations of the two applications; one is cold storage and another is freezing.In cold storage application used two capillary tubes in parallel that gave better performances than single tube. So COP is higher in cold storage than freezer application. In normal condition Refrigeration capacity (QRC) increases with inlet temperature of brine (TBi) but the volumetric rate flow of the brine (VB) is decreases but in extreme condition variations are slight. Naturally it found that in freezing application QRC decreases with increasing inlet temperature of cooling water (TC). But in cold storage with single tube the effect was reversed but if two tubes were used the effect was as same as freezing application. In cold storage application QRC also decreases with length of capillary tubes (L) while single tube used but when two tube used the effect would be reversed and similar effect showed on freezing application. Ultimately they found that cold storage application performed better than freezing when two tubes was used.[32] Baskaran and Koshy experimentally analysed the performance of vapour compression refrigeration system by using eco-friendly refrigerants and compared with the performance of the system when R134a used. This experiment was done developing a simulation model in software CYCLE_D4.0. The alternative refrigerants used in this analysis were HFC152a, HFC32, HC290, HC1270, HC600a and RE170. Among those refrigerants RE170, R152a and R600a gave a higher performance coefficient than R134a in a specific temperature of condenser and evaporator. They concluded that RE170 was the alternative refrigerant of R134a. They found that refrigerant type, degree of sub cooling degree of superheating has some effect on refrigerating effect, COP and volumetric refrigeration capacity for various evaporating temperatures. So ultimately they concluded that RE170 was most suitable refrigerant comparison to R134a for better COP, pressure ratio and also evaporating impacts of ozone layer depletion and global warming.[33] Soni and Gupta numerically simulated theoretical vapour compression refrigeration cycle using R404A, R407C and R410A as refrigerants.

23They developed a computational model based on exergy analysis. They concluded that the COP and exegetic efficiency of R407C were better than that of R404A and R410A. It was found that COP and exergy efficiency improved when sub cooling of high pressure condensed liquid refrigerant was done. They also concluded that if dead state temperature increased exegetic efficiency will increase and exergy destruction ratio will reduce while coefficient of performance will remain constant. With the increase in effectiveness of liquid vapour heat exchanger, COP and exegetic efficiency decreased though exergy destruction ratio increased as reported by the authors.[34] Parekh and Tailor conducted a thermodynamic analysis on cascade refrigeration system using R12-R13, R290-R23, R 404-R23 refrigerant pairs. This analysis is performed by two-stage cascade refrigeration system with some thermodynamic assumptions. The operating parameters varied in that analysis are evaporator temp, condenser temperature, temperature difference in cascade condenser and low temperature condenser which had an effect on performance parameters such as COP, exegetic efficiency and refrigerant mass flow rate. They observed that COP of system when R290-R23 refrigerant pair was used is maximum when evaporating temperature varied from -80C to -60C. They found that COP decreases when condenser temperature varied from 25C to 45C. Similar trend is found when temperature difference in cascade condenser varied from 2C to 6C. They also mentioned that COP of the system increases when condenser temperature varied from -5C to -35C in lower temperature cycle.[35] Fiori and Linba presented a paper on a thermodynamic analysis of a cascade refrigeration system using the refrigerant pair R22-R404a where R22 worked as working fluid in high temperature circuit and R404a in low temperature circuit. This analysis obtained an optimal value for COP of the cycle considered the temperature of LT. The operating parameters was evaporation temperature, condensing temperature and difference between condensing temperature of LT & evaporating temperature of HT. It had been obtained that the COP had a maximum value at the intersection of COP curves of each circuit. But it was not possible to get maximum COP because the intermediate temperature was very low.[36] Alhamid et al. conducted an Energy and Exergy analysis on cascade Refrigeration system using carbon dioxide and ethane-propane as refrigerant (R-744 + R170-R290). They assumed that compression process was non isentropic, isenthalpic expansion and negligible changes in kinetic and potential energy. They also took the dead state temperature at 25C and 101.3 kPa, mechanical efficiency of each compressor is 0.95 and difference between refrigerated space temperature and evaporating temperature is 5C. They found that an optimal temperature of cascade condenser can obtained for a specific system and in operating conditions in energy exergy optimization methods. They also evaluated COPmax and mass flow ratios using multi linear regression method.[37] Tripathy et al. conducted a numerical simulation on a cascade refrigeration system using refrigerants as carbon dioxide and Ammonia (R744, R717) as the main working fluid in the system. They assumed that condenser and cascade condenser at subcooled state and that of evaporator at superheated state. 24In this work they found two co-relations of optimum condensing temperature and COPmax with condensing temperature, evaporating temperature and temperature difference between cascade condensers by these two relations they determined the optimum condensing temperature and copmax .[38] Sachdeva et al. investigated for the best substitute of R-12 on vapour compression cascade refrigeration system. Refrigerants runs in high temperature circuit are Ammonia (R717), Propane (R290), Propylene (R1270) R404A and Dichlorodifluoromethane (R12) and in low temperature circuit Carbon dioxide (R744) is used as working fluid. They assumed that the compressors isentropic efficiency will be given for both high and low temperature compressors. They neglected the pressure loss in pipe networks and changes in kinetic and potential energy. After the end of their investigation they found Ammonia is the best alternative of Carbon dioxide.[39] Xu et al. presented a project on novel low absorption compression refrigeration system using mixture of refrigerants. In this experiment they assumed that suction temperature, condensing temperature and temperature of top and bottom outlets of rectification column were specified. They neglected the pressure losses and the heat losses. They also specified volumetric efficiency and isentropic efficiency off the compressor. They obtained the cooling range between - 60 C to -140C.[40] Yamaguchi et al. investigated the dry ice blockage in an ultra-low temperature of cascade refrigeration with working with carbon dioxide (R744). They found in this visual experiment that dry ice sedimentation occurs in low flow velocity and dry ice is responsible for complicated behaviour of CO2.[41] Yan et al. conducted a research on performance of an internal auto cascade refrigeration system (IARC) using R290/R600 or R290/R600a as refrigerants. They assumed the isentropic efficiency of the compressor is related to its pressure ratio. They also neglected the pressure drop and heat losses. They also assumed isenthalpic throttling in capillary tubes and irreversible compression in the compressor. They concluded that there is a 7.8 to 13.3% increase in efficiency for IARC then conventional refrigeration system when R290/R600a is used.

Objective:The aim of this study is to investigate first law and second law analysis of mechanical vapour compression refrigeration system using various refrigerants based on energy and exergy concept. Various parameters, like COP, required compressor power, total exergy loss, mass flow rate and exergy efficiency are computed in this work. Values of some parameters have been assigned from the literature. The final aim is to choose one or more alternative refrigerants which can replace CFC12 without sacrificing much loss in the performance of the refrigeration system.

25 Chapter 4MATHEMATICAL FORMULATION:1. Description of the proposed model:A vapour cascade refrigeration system is basically consist of a one evaporator, two compressors, one condenser, one cascade condenser and two expansion valve as shown in fig. 1. The quantity of heat, Q1 taken at low pressure, P3 in the evaporator to evaporate the liquid refrigerant by taking heat from surrounding. Then it passed through a compressor of isentropic efficiency, s, where it is compressed by means of mechanical work, Wc1 on the system for increasing the pressure of the vaporized refrigerant from P3 to P4 (condenser pressure). Then, this vaporized high pressure refrigerant goes to cascade condenser and reject heat to the low temperature circuit. From this low temperature refrigerant evaporated and went to the 2nd compressor at pressure P7. Then at compressor by means of mechanical work Wc2 on the system for increasing the pressure P7 to P8 (condenser pressure). Then the refrigerant from compressor to condenser, where it is condensed. Then condensed refrigerant from cascade condenser enters into the expansion valves, where the pressure decreases without any loss in enthalpy. Then the high temperature circuit liquid refrigerant enters again into the evaporator for running the cycle again.

Fig: 1 Schematic diagram of the vapour-cascade refrigeration system2. Thermodynamics of the system:Energy and exergy analysis need some mathematical formulations for the vapour-cascade refrigeration system. In the vapour-cascade refrigeration system, there are five major components namely, evaporator, compressor, cascade-condenser, condenser and expansion valve. Various calculations are done based on this system using alternative refrigerants. Coefficient of Performance (COP) of vapour-cascade refrigeration system is a very important creation for performance indicator. 26It expresses as-COP= Refrigeration effect / Compressor work = Q / WWhere Q is the refrigeration effect and W is the compressor work. This above said two parameters can be calculated asTCC=cascade-condenser temperature,TC= condenser temperature,TE= evaporator temperature From T1 we find that, h1, Sg1Sg1=Sg2+Cpln (T2 / Tc+273)From here we find T2,h2s = hg at Tcc+ Cp (T2-Tc.c), h2 = h1 + (h2s h1) / compressorQ1= (h1-h4),Q2= (h2-hf3),Q2= (h2-hf3) Where = effectiveness, Taking hf3=h4As it is a cascade-condenser then,(h2- hf3) = h5-h8From cascade-condenser temperature (TCC),We get h5, Sg5Sg5=Sg at Tcc+ Cp ln (T6 / Tc+273), H6= hg at Tc+Cpg (T6-Tc)From condenserQ2= h5-h8 and taking h8= hf7, COP= (mhQ1+mlQ2) / (W h+ Wl)Where, Wh= Compressor work done of High Temperature circuit.Wl= Compressor work done of Low Temperature circuit.And taking, mh= ml = m = 1kgRefrigeration Effect (R.E) = mh(h1-h2) + ml (h5-h8)Total Compressor workWcompressor= W h+ Wl= mh(h2-h1) + ml (h5-h6)Efficiency of exergetic energy (exergetic) = Wrev/ Wact

Wrev= QE [(TC / TE)-1] 27 Chapter 5Results and discussion:In this project we calculated the co-efficient of performance, compressor work, refrigerating effect, efficiency of vapour cascade refrigeration system (R12 in high temperature circuit and R404A in low temperature circuit). These results are discussed below. Here is some assumption about some parameters as per given below-Case 1Tevaporator=400C, T cascade=50CCompressor efficiency=65% (for both the condenser) Effectiveness of the cascade heat exchanger=75% And mh=ml=m=1[mh=mass flow rate at high temperature circuit, ml=mass flow rate at low temperature circuit)Case 2Tevaporator=400C, T cascade=100CCompressor efficiency=65% (for both the condenser) Effectiveness of the cascade heat exchanger=75% And mh=ml=m=1[mh=mass flow rate at high temperature circuit, ml=mass flow rate at low temperature circuit).Piping losses, loss in the condenser, cascade heat exchanger neglected in both the cases.Effect of evaporator temperature on COP: Co-efficient of performance is a vital parameter in Vapour cascade refrigeration system. It is expressed the system performance. The variations of COP of the system using refrigerants R-12 in high temperature circuit and R-404a in low temperature circuit against evaporator temperature -10to 00C and the condenser temperature have been shown in figure. It is seen from figure that, as the evaporator temperature increases then COP of the system increases for the investigated refrigerants. If the cascade condenser decreases, then the COP of the system increasesEffect of evaporator temperature on compressor work: Compressor is the heart of mechanical vapour cascade refrigeration system as it circulates the refrigerant the system like the heart of a human being circulating the blood in the body. Input in the compressor is provided to increase the pressure of the refrigerant. As we increase the evaporator temperature from -10c to 0c then the compressor work decreases. It has a relationship with cascade heat exchanger temperature also. As the cascade condenser temperature decreases compressor work increases. The results are plotted in the graphs below. 28Effect of evaporator temperature on refrigerating effect:The refrigerating effect is the main measurement of the total work done by the cascade refrigerator. The refrigerating effect varies proportionally with the evaporator temperature. As the evaporator, temperature increases the refrigerating effect increases. It has an inverse relationship with the cascade condenser temperature. As the cascade condenser temperature increases, the value of the refrigerating effect also increases. The refrigerating effect Vs evaporator temperature curves are plotted be

Effect of evaporating temperature on exergetic efficiency: The exergetic efficiency indicates the utilization capacity of the available energy by the system it permits to identify and calculate the various exergy losses in different components. The exergetic efficiency increases with the evaporator temperature. It has an inverse relationship with cascade condenser temperature. As the cascade condenser temperature decreases the exergetic efficiency increases. 29Chapter 6

Conclusion The coefficient of performance of the cascade refrigeration system (R-12 &R-404a) increases with the decrease in the cascade condenser temperature. The cop of the system decreases with the decrease in the evaporator temperature. The compressor work increases with the decrease in the evaporator temperature. The compressor work decreases with the decrease in the cascade condenser temperature. Refrigerating effect of the system increases with the increase in the evaporator temperature. It also increases with the decrease in the cascade condenser temperature. The exergetic efficiency decreases with the decrease in the evaporator temperature. The exergetic efficiency has an inverse relationship with the cascade condenser temperature. It increases when the cascade condenser temperature decreases. For the 5C decrease in evaporator temperature the COP increases 5.67%. The compressor work increases 2.22% with the 5C increase evaporator temperature. If the evaporator temperature is increased by 5C, then the refrigerant effect will decrease by 1.9%. The exergetic efficiency decreases 3.6% with 5C increase in evaporator temperature.SCOPE OF FUTURE WORK: This work can be extended, future trends and research direction keeping on mind as following acts mentioned below: -1.Develpoment of computer software code to determined different types of refrigerant properties.2. Hunt for the alternative refrigerants without hampering the COP can be added to this work3. Exergy analysis can be done to each components of the system.4. More refrigerants and mixture of refrigerants can be used as the working substance. 5. Actual cycle analysis can be done considering the volumetric efficiency of the compressor and pressure loss in the system.

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