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CHAPTER (1)

INTRODUCTION

HCFC22 has been predominantly used in residential air conditioners

and heat pumps for the past few decades and its sales volume has been the

largest among various refrigerants. Even though the ozone depleting potential

of HCFC22 is not as high as CFCs, it still contains ozone depleting chlorine.

Due to its ozone depleting effect, Montreal Protocol and its amendments have

set the phase-out deadlines on HCFC22in different countries and areas.

The Montreal Protocol sets limits (cap) for the HCFC consumption,

defined as production plus imports less exports and specified destruction: in

1996 (freeze at calculated cap), 2004 (65% of cap), 2010 (25%), 2015 (10%),

and 2020 (0.5%) with full consumption phase-out by 2030 in non-Article 5

countries. Aprea et al ( 2011) reported that the schedule for Article 5 countries

like Egypt begins with a freeze of the amount of HCFC in 2013 (based on

2010 production and consumption levels) with declining limits starting in

2015 (90%), 2020 (65%), 2025 (32.5%), and 2030 (2.5%) followed by phase-

out in 2040. Exports from Article 5 countries into non-Article 5 countries are

effectively restricted to meet the more stringent non-Article 5 schedules to

avoid separate domestic and export products and to exploit newer

technologies derived from joint ventures and licensing agreements.

Park and Jung (2006) sated that various alternatives for HCFC22 have

been proposed and tested in an effort to comply with the Montreal protocol in

the past years,. At this time, HFC refrigerant mixtures such as R-410A and R-

407C are used in some countries to replace R-22. R-410A is a near azeotropic

mixture with a gliding temperature difference (GTD) of less than 0.2C. Its

vapor pressure is roughly 50% higher than that of HCFC22 and hence the

capacity increases significantly with R-410A. Due to high pressure,


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compressors need to be redesigned completely and also the heat exchangers

needs to be optimized to accommodate lower volumetric flow rates associated

with the use of R-410A. Even though a simple thermodynamic cycle analysis

shows that the cycle COP of R-410A is somewhere lower than that of

HCFC22, the actual energy efficiency of R-410A is similar to that of

HCFC22 due to the improved compressor efficiency and reduced energy

losses in some components of the refrigeration system. On the other hand,

R407C is a non-azeotropic refrigerant mixture (NARM) whose GTD is

roughly 6 C. Its vapor pressure is similar to that of HCFC22 and hence it is

expected that R-407C may be used in existing equipment without major

changes. Since it is a NARM, however, fractionation may occur in case of the

leak in the system. At the same time, many companies expend much effort to

develop their own alternatives for R-22. Especially, refrigerant mixtures

composed of environmentally safe pure refrigerants have gotten a special

attention from the industry with the expectation of possible energy efficiency

without major changes in the system.Limitations of both R-410A and R-407c lead many researchers to

search about the best R-22 replaced refrigerant in both for old equipment and

new one. Strategy of R-22 replacement has three mechanisms available to

eliminate this substance. First, especially for old equipment with remaining

life, a drop-in process is recommended. This involves the pure exchange of

the refrigerant without any modifications to the refrigerating plant and

keeping the existing lubricant oil. The second option is to undertake a

retrofitting process. This is understood as an active adaptation of the

refrigeration plant to the new refrigerant, which could also entail the

replacement of the lubricant oil, the expansion valves and certain other

elements of the system. Finally, the last option, although only possible for

new equipment, is to design new plants with long-term refrigerants, such as


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hydrocarbons, ammonia or carbon dioxide as reported by Mohanraj et al

(2009).

A number of R-22 alternatives for vapor compression residential air

conditioners and heat pumps systems have been proposed in the literature

based on thermodynamic property data. Thus, the objectives of the present

work are studying investigation the performance characteristics of water

chiller work with R-22, R-438A and R-422A respectively. Comparison

between performance characteristics of the air conditioning system using

R-22 and its alternatives. Indicate the best drop-in replacement refrigerant for

old systems.

The present thesis consists of six chapters and five appendices. Chapter

(1) gives a brief introduction. Chapter (2) deals with an overview of the

literature related to performance characteristics of compression residential air

conditioners and heat pumps working with R-22 alternatives. Chapter (3)

describes the experimental test rig including instrumentation, test procedure

and data reduction. Results of experimental investigations are discussed inChapter (4). Conclusion of experimental investigations are given in Chapter

(5). Specification of water chiller system components, specification of the

instrumentation devices, instruments calibration and uncertainty analysis are

given in appendices (A), (B), (C), and (D), respectively.


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CHAPTER (2)

LITERATURE SURVEY

2.1 Introduction

R-22 has been widely used for many decades in vapour compression

refrigeration system. It is generally accepted and most suitable refrigerant for

air-conditioners and in medium and low temperature applications for

commercial and industrial refrigeration. Unfortunately, it belongs to the

family of hydro-chlorofluorocarbon (HCFC) refrigerants, which considered as

harmful working fluids to the environment. Due to their stratospheric ozone

layer depletion, they are now being controlled substances by the Montreal

protocol. Montreal Protocol and its amendments have set the phase-out

deadlines on R-22 in different countries and areas. EU and Japan have banned

the import of R-22 systems since 2004, and the USA has prohibited the use of

R-22 as refrigerant in new equipment from 2010. In accordance with the

Montreal Protocol, all developing countries will freeze R-22 consumption at

its level in 2015, and will ban the use of R-22 in A/C industry from 2030.

With increasingly understanding the consequences caused by the ozone

depletion, many countries and areas have accelerated the phase-out process of

R-22.

2.2 Environmental Impacts

In general, the atmosphere is divided into five layers, which are defined

by distance above the surface of the earth. They are; troposphere (0-15km);

stratosphere (15-50km); mesosphere (50-85km); thermosphere and

ionosphere (above 85km).

HCFC 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 chlorine and fluorine atoms


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present in HCHC refrigerants is responsible for the major environmental

impacts. The two important ones are ozone depleting and greenhouse.

2.2.1 Ozone depletion

Ozone (O3) is a triatomic allotrope of oxygen composed naturally

through a process called photochemical analysis where the sunlight has an

impact on oxygen molecules, the ozone exists throughout the year over the

equatorial belt, and moves toward the polar regions by the movements of air

in the stratosphere that is filled by ozone on the altitudes ranging from 20 to

35 kilometers, Its thickness ranges between 2 to 8 km as reported in (MSEA-

EEAA, 2009).

It is an extremely rare component of the Earths atmosphere; in every

ten million molecules of air, only about three are ozone. Most of the ozone

(90%) is found in the upper atmosphere (UNEP, 2000).

HCFCs, CFCs and halons are stable chemicals, which persist for many

years in the atmosphere. They eventually break down in the stratosphere torelease halogens; chlorine in the case of HCFCs, CFCs and bromine in the

case of halons. Chlorine and bromine can destroy ozone but are not destroyed

themselves during this process. Thus one halogen atom can destroy thousands

of molecules of ozone.

Ozone layer is the natural filter and preventive shield surrounding Earth

to protect all creatures against harmful UV-B rays effects coming from the

sun to earths surface. Effects include human skin cancer and eye cataract;

effect on photosynthesis in green plants, reducing plant growth and affecting

agricultural crops; and impact on marine ecosystems, all of which leads to an

unbalanced general system of nature and life on earth, which, in turn, affects

the global climate change; hence, threatening human health and environment

safety.


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2.2.2 Greenhouse

The greenhouse effect is caused by absorption of long wave radiation

from earths surface by carbon dioxide, and the other naturally occurring

"greenhouse gases", in the troposphere (0-15 km). Short wave radiation from

the sun has most of its harmful components filtered out by the ozone layer.

The rest of the short wave radiation heats the surface of the earth and the seas.

These surfaces give off long wave radiation, which can be trapped by a

variety of greenhouse gases, which act like an insulating blanket. There is

thus a tendency for global warming.

The environmental effects are measured by ozone depletion potential

(ODP), global warming potential (GWP) and total equivalent warming impact

(TEWI). ODP is a relative index indicating the extent to which a chemical

may cause ozone depletion. The reference level of 1 is the potential of R11 to

cause ozone depletion. GWP is also a relative index indicating the extent to

which a chemical may cause greenhouse effect. To combine the impact ofdifferent greenhouse gases released into the atmosphere, TEWI has been

defined as the equivalent amount of carbon dioxide (CO2) that would give

approximately the same integrated radiative forcing over a particular

integration time horizon (ITH). TEWI takes into account contributions from

the substance itself (direct) and the data on energy consumption of the

equipment during its operation (indirect) that may contribute to global

warming.

TEWI is expressed as the sum of contributions from direct and indirect

global warming potentials as:


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TEWI = (GWP x Lx n)+ (GWP x m (1- (recovery) +(n x Eannual x)

Leakage Recovery losses Energy consumption-

direct global warming potential indirect global

Warming potential

Where, GWP is the global warming potential (CO2-related), L is the leakage

rate per year (kg), is the system operating time (years), m is the refrigerant

charge (kg), recovery is the recycling factor, E annual is the energy

consumption per year (kWh) and is the CO2-emission per kWh. The ODP

values of pure CFC and HCFC refrigerants are shown pictorially are shownpictorially in Fig. 2.1.The GWP values of pure and mixed refrigerants are

illustrated in Fig. 2.2 and Fig. 2.3 .

Fig. (2.1) Ozone depletion potential of pure CFCs and HCFCs refrigerants

(Calm and Hourahan, 2001).

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

R11 R12 R113 R114 R115 R22 R123 R124 R141B R438A R422A

1

0.82

0.90.87

0.40.36

0.03

0.08 0.11

0 0

ODP

Refrigerants


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Fig. (2.2) Global warming of pure CFC and HCFC refrigerants (Calm and

Hourahan, 2001).

Fig. (2.3) Global warming of HFC mixtures (Dupont,2009)

0

2000

4000

6000

8000

10000

12000

R11 R12 R113 R114 R115 R22 R123 R124 R141B R142B

4800

10900

6000

9700

6800

2000

400

1000 1100

2200

GWP

Refrigerants

0

500

1000

1500

2000

2500

3000

3500

4000

R404A R407A R407B R407C R438A R410A R410B R417A R422D R422A

3650

2000

2600

1750 1684

2100 2200

2300

2729

2530

GWP

Refrigerants


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2.3 International Efforts

The efforts can be sorted in two directions.

2.3.1 Ozone layer depletion

Molina and Rowland studied of ozone layer depletion since 1974 for

first time then the scientific confirmation of the depletion of the ozone layer

prompted the international community to establish a mechanism for

cooperation to take action to protect the ozone layer. This was formalized by a

treaty called the Vienna Convention for the protection of the ozone layer,

which was adopted and signed by 28 countries on 22 March 1985 in Vienna.

This led in September 1987 to the drafting of the Montreal Protocol on

substances that deplete the ozone layer. The Protocol was signed by 24

countries and by the European Economic Community and entered into force

on 1 January 1989. The treaty states that the Parties to the Montreal Protocol

recognize that worldwide emissions of ozone-depleting substances (ODSs)

significantly deplete and otherwise modify the ozone layer in a manner that islikely to result in adverse effects on human health and the environment. The

Parties previously agreed to an extended phase-out schedule, with final phase-

out in developed countries by 2030 and in developing countries by 2040.

These schedules have now been brought forward. The September 2007

adjustments to the Montreal Protocol oblige Article 5 countries to take action

as soon as possible to freeze their baselines in respect of HCFC production

and consumption levels (average consumption and average production for the

years 2009-2010) in 2013, and as a first step, to reduce their production and

consumption of HCFCs by 10 per cent by 2015 ( UNIDO,2009).


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2.3.2 Climate change

The United Nations Framework Convention on Climate Change

(UNFCCC) was agreed in 1992 in Rio de Janeiro and ratified thereafter.

Many countries joined the international treaty to begin to consider what could

be done to reduce global warming and to work on adaptation strategies to

cope with whatever temperature increases are inevitable. More recently, a

number of nations approved an addition to the treaty, the Kyoto protocol,

which has more powerful (and legally binding) measures. The UNFCCC

secretariat supports all the institutions involved in the international climate

change political process. The Kyoto protocol is an international agreement

linked to the United Nations framework convention on climate change. It was

adopted in Kyoto, Japan, on 11 December 1997, and entered into force on 16

February 2005. To date, 180 nations have ratified the treaty. The detailed

rules for the implementation of the Protocol were adopted at the Seventh

Conference of the Parties in Marrakesh in 2001 ( UNIDO,2009).

2.4 Egyptian Strategy for Phasing Out Use of HCFCs Substances

Egyptian Meteorological Authority (EMA) measures ozone for

monitoring ozone layer change above Egypt, especially above Aswan (above

the tropical area where ozone is naturally generated). Figure (2.4) show that

Ozone measurement changes above Cairo and Aswan Straight lines

demonstrate that there is no clear tendency for change.

MSEA is currently conducting an amendment and updating legislations and

regulations related to the use and importation of HCFC substances; in

addition to developing a strategy for phasing out use of such substances in

various fields. Table (2-1) shows the timetable of phasing out the use of the

ozone depleting HCFCs in "Article 5" countries (including Egypt) that applies

to Montreal Protocol (Egypt State of Environment Report, 2009).


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Table (2.1): Timetable for phasing out use of HCFCs (UNIDO, 2009)

Substance Base Level Production/Consumption Rate Control

First Group

HCFC

substances

Average

Consumption

Rate in

2009-2010

Freezing production/consumption

levels (1st January, 2013)

10% reduction (1st January ,2015)

35% reduction (1st January , 2020)

67.5% reduction (1st January ,2025)

100% reduction (1st January, 2030) with a

possible exemptions for necessary uses.

Fig. (2.4) Ozone measurement changes above Cairo and Aswan (MSEA-

EEAA.,2009)


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2.5 R-22 Replacement

From precession R-22 must be phased-out and it must be replaced in

both for old equipment and new one. Strategy of R-22 has three mechanisms

available to eliminate this substance, which are schematized in Fig. (2.5).

First, especially for old equipment with remaining life, a drop-in process is

recommended. This involves the pure exchange of the refrigerant without any

modifications to the refrigerating plant and keeping the existing lubricant oil.

The second option is to undertake a retrofitting process. This is understood as

an active adaptation of the refrigeration plant to the new refrigerant, which

could also entail the replacement of the lubricant oil, the expansion valves and

certain other elements of the system. Finally, the last option, although only

possible for new equipment, is to design new plants with long-term

refrigerants, such as hydrocarbons, ammonia or carbon dioxide.

Fig. (2.5) Mechanisms and some refrigerant options to substitute R22 in

medium and low temperature applications. (Llopis et al., 2012)


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2.6 Experimental and Theoretical Studies

A large number of experimental and theoretical studies are found in literature

pertaining to HC, HFC and their mixtures as alternatives to halogenated

refrigerant by researchers from various parts of the world. A brief summary of

these results is given in the following sections

(Mohanraj et al., 2009)

2.6.1 Hydrocarbons refrigerants as R22 alternatives

Choi et al. (1996) evaluated the performance of flammable refrigerants

as R22 alternative for water-to-water residential heat pump applications at

different compressor speeds. The results showed that based on the capacity

R32/R152a was found to be the best performer due to good glide matching in

the heat exchangers and have good thermodynamic and transport properties.

The HC mixture (R290/R600a) is found to have the highest COP with a loss

in the system capacity.Purkayastha and Bansal (1998) experimented with R290 and LPG

(R290 98.95%, R170 1.007%, R600a 0.0397%) as substitute for R22 in

a 15 kW heat pump. It has been reported than COP of HC refrigerants (R290

and LPG mixture) were respectively 18% and 12% higher compared to that of

R22. However volumetric refrigeration capacity and condenser are highly

lower by 16% and 14% and 13% and 10%.

Chang et al.(1999) measured the performance characteristics of heat

pump system using hydrocarbon refrigerants (propane, isobutane, butane and

propylene) and binary mixtures of propane/ isobutene and propane/butane as

alternative to R-22 They concluded that The cooling and heating capacities of

R290 are slightly smaller than those of R-22 with a slightly higher COP than

that of R-22. The capacity and COP of R-1270 are slightly greater than that of


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R-22, which is an indication of a possible alternative for air conditioning and

heat pumping applications. When zeotropic refrigerant mixtures of R-290=R-

600a and R-290=R-600 are used, the cooling and heating capacities increase

almost linearly with respect to mass fraction of R290. COPs for the mixtures

are higher than linearly interpolated values based on those of pure

components. The COP of hydrocarbon mixtures for the cooling condition is

higher than that of R-22 for a wide range of the mixture compositions.

Hydrocarbon refrigerants have a higher thermal conductivity and a lower

viscosity in the liquid phase than R-22, which is a potential for higher heat

transfer coefficients in the evaporator and condenser. When considering

average heat transfer coefficient, it is concluded that hydrocarbons heat

transfer performance is comparable to R-22. Zeotropic mixtures show heat

transfer degradation due to composition difference between vapor and liquid

phases.One thing to keep in mind is the flammability of hydrocarbon

refrigerant. Leak-free design of a system, or indirect heating or cooling design

using the secondary heat transfer fluid can be a possible solution. Safetyshould be considered when using hydrocarbon as a refrigerant.

Chang et al. (2000) investigated with R290, R1270, R600, and R600a

and binary mixtures of R290/R600a and R290/R600 as R22 alternatives in a

heat pump. It has been reported that cooling and heating capacity of R290

were smaller and COP was slightly higher than that of R22. The capacity and

COP of the R1270 were slightly greater than R22. The COP of the zeotropic

mixture R290/R600a with 50% mass percentage of R290 was enhanced by

7% and R290/R600 at composition of 75:25 (by mass percentage) showed

11% improved performance. It has been found that system is degraded for

zeotropic HC mixtures due to composition variation in phase change.

Granryd (2001) reviewed the HC refrigerants for different

applications. He compared R290 with R22 and reported that R290 gave lower


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capacity by 315% than that of R22. The heat transfer coefficient of R290 in

condenser was also found to be lower than that of R22.

In 2001 Devotta and Waghmare use NIST CYCLED has been used for

the comparative thermodynamic analysis for the comparative thermodynamic

analysis. and they found that the characteristics of HC 290 are very close to

those of HCFC-22, and compressors require very little modification.

Therefore, HC-290 is a potential candidate provided the risk concerns are

mitigated as had been accomplished for refrigerators.

Urchuegua et al. (2004) reported the experimental characterization of

two commercial scroll and reciprocating compressors working with R22 and

R290 with same mineral oil as lubricant. His experiments reported that the

refrigerating capacity in both types of units was reduced 1320% due to the

use of propane but at the same time COP was increased by 13%.

Chaichana et al. (2003) studied the options of using natural working

fluids (R717, R744, R290, R600, R600a and R1270) as substitutes for R22 in

solar boosted heat pumps based on thermo-physical properties and the thermalperformance. Their results indicate that R744 is not suitable for solar boosted

heat pumps because of its low critical temperature and high operating

pressure values. R717 seems to be more appropriate in terms of operating

parameters and performance which requires major changes in the system.

Condensing pressure values of R600 and R600a are 5070% less than R22.

Hence R600 and R600a cannot be used as drop in substitute for R22. R290

and R1270 have close saturation pressure values compared to that of R22.

The performance of R22, R290 and R1270 was comparable. Hence, R290 and

R1270 were identified as direct drop in substitutes for R22.

Thermodynamic analysis of refrigerant mixtures for possible replacements

for CFCs by an algorithm compiling property data was reported by

Arcaklioglu et al (2006). To achieve this aim the point properties of the


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refrigerants are obtained from REFPROP where appropriate. According to his

calculations using the current systems the best mixtures, which can either fit

or provide better performance for the CFC based refrigerants, are as follows

For R12, R290/R600a (56/44) mixture provides 0.4% better COP. For R-22,

R32/R125/R134a (32.5/5/62.5) mixture provides 0.8% better COP. For R502,

R32/R125/R134a (43/5/52) mixture provides 2% better COP.

Park and Jung. (2006) studied the thermodynamic performance of two

hydrocarbon refrigerants and seven mixtures composed of R1270, R290,

RE170 and R152a as alternatives for R22 in residential air conditioning

applications. It has been reported that all the pure and mixed fluids tested

have low GWP of 358 as compared to that of R22. Also their test results

showed that expect R1270, all the other refrigerants have higher COP with

lower discharge temperature and similar refrigeration capacity.

Park and Jung. (2007) studied performances of two pure

hydrocarbons and seven mixtures composed of propylene, propane,

HFC152a, and dimethylether were measured to substitute for HR-22 inresidential air-conditioners and heat pumps. The pure and mixed refrigerants

tested have greenhouse warming potentials (GWPs) of 358 as compared to

that of CO2 and the mixtures are all near-azeotropic having the gliding

temperature difference (GTD) of less than 0.6 0C .The following conclusions

were drawn. COPs of these fluids are similar to, or better than, that of R-

22.45%R1270/ 40%R290/15%DME mixture showed the highest COP which

is 5.7% higher than that of R-22.Capacities of propane (R-290) and

20%R1270/80%R290 are lower than that of R-22 by 11.5 and 6.6%,

respectively, while other fluids showed a similar capacity to that of R-

22.Compressor-discharge temperatures of all fluids tested were lower than

that of R-C22 by 1117 0C. This indirectly indicates that these fluids would

show long-term stability and reliability. The refrigerant charge for all


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refrigerants tested was reduced up to 55% as compared to R-22 due to their

lower density.

Thermodynamic performance of R-433A (30% propylene and 70%

propane)and R-22 is measured in a heat pump bench tester under air

conditioning and heat pumping conditions was studied by Park et al

(2008).He concluded that The COP of R-433A is 4.97.6% higher than that of

R-22.The capacity of R-433A is 1.05.5% lower than that of R-22.The

compressor discharge temperature of R433A is 22.627.9 _C lower than that

of R-22.The amount of charge for R-433A is 57.057.7% lower than that of

R-22 due to its low density.R-433A is a good long term environmentally

friendly alternative refrigerant to replace R-22 in residential air-conditioners

and heat pumps due to its excellent thermodynamic and environmental

properties with minor changes.

Ki-Jung Park (2009) back to study thermodynamic performance of R-

432A (80% propylene (R1270) and 20% dimethylether (RE170)) and R-22 is

measured in a heat pump bench tester under both air-conditioning and heatpumping conditions. He concluded that the COP of R-432A is 8.58.7%

higher than that of R-22.The capacity of R-432A is 1.96.4% higher than that

of R-22.The compressor discharge temperature of R432A is 14.1 17.3oC

lower than that of R-22.The amount of charge for R-432A is 50% lower than

that of R-22 due to its low density.R-432A is a good long term drop-in

environmentally friendly alternative refrigerant to replace R-22 in residential

air conditioners and heat pumps due to its excellent thermodynamic and

environmental properties.

Cleland et al. (2009) studied the using of hydrocarbons as drop-in

replacements for R-22 in on-farm milk cooling equipment and he concluded

that Drop-in replacement of R-22 by the hydrocarbon refrigerant Care-50 in a

farm milk silo refrigeration system gave about 6% lower energy use, and had


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no noticeable effect on milk cooling capacity. The conversion was very

simple and potentially cost-effective because, apart from the change in

refrigerant (and associated labeling and documentation), no other alterations

or adjustments to the system were made. Both the laboratory and farm trials

showed that hydrocarbons are attractive alternatives R-22 for on-farm milk

cooling equipment.

Teng et al (2012) studied investigates the feasibility of replacing R-22

window air conditioners with hydrocarbon refrigerants (propane, R290) for

various charged masses (25 70%), and analyzes the performance at different

outside air temperatures (26, 29, 32 oC)Results show that the best charged

mass for replacing R-22 with R290 refrigerant is approximately 50 55% of

the R-22 refrigerant for various outside air temperatures. In addition, a

comparison of R-22 and R290 refrigerants shows that the EER of R290

refrigerant exhibits an upward trend as the outside air temperature increases,

improving the EER by approximately 20% in the ideal situation. The

refrigerant in a window air conditioner can be changed from R-22 toR290refrigerant, and the ODP and GWP differences are negligible. Results

show that R290 refrigerant is suitable for use in higher outdoor temperature

and higher EER values of R290 air conditioner, and simultaneously helps

combat global warming and reduce carbon emissions.

2.6.2 Carbon dioxide as an alternative

Brown et al. (2002) compared the performance of CO2 and R-22 in a

residential air conditioning system using semi-theoretical vapor compression

and trans critical cycle models. The simulated R22 system has conventional

component configuration, while CO2 system includes liquid-line/suction-line

heat exchanger. It has been reported that COP of the CO2 system is 10% less

and power consumption is 38% higher than that of R22. The cooling


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capacities of both the systems were identical at 35 o C ambient temperatures

and will decrease linearly with increase in the ambient temperature.

2.6.3 HFC mixtures as alternatives

Knig. (1997) compared propane as R-22 replacements with R-410A,

R-407C. Theoretical comparison of these replacements showed that only

slight difference in terms of COP and capacity.

Jung et al. (2000) studied the performance of HFC and hydrocarbon

mixtures as alternatives to R-22. It has been reported that COP of ternary

mixtures composed of R-32, R-125, R-134a is 45% higher than that of R-22.

The COP of binary mixture composed of R-32 and R134a is 7% higher and

capacities are similar to R-22 and COP of binary azeotrope of R-290 and

R134a is 35% higher than R-22. Compressor dome temperature and

discharge temperature were found to be lower than that of R-22 and hence the

system reliability and fluid stability with these mixtures would be better than

that of R-22.Motta and Domanski (2000) reported the simulation results of R-22

and its alternatives R-410A and R-407C at high outdoor temperatures. Their

results indicate that R-410A has more pronounced performance degradation

than R-22 and R-407C because of low critical temperature. R410A has the

highest COP degradation. The change of COP for R-22 and R-407C is similar

because their critical temperatures are within 10 K of each other. The

presence of liquid-line/suction-line heat exchanger will improve the capacity

and COP of all refrigerants studied.

Devotta et al. (2001) NIST CYCLED has been used for the

comparative thermodynamic analysis. Among the refrigerants studied (HFC-

134a, HC-290, R-407C, R-410A, and three blends of HFC-32, HFC-134a and

HFC-125) and they found that. HFC-134a offers the highest COP, but its


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capacity is the lowest and requires much larger compressors. For retrofitting,

R-407C is probably the best candidate.

Kim (2002) reported an experimental assessment of performance tests

for R-22 and four alternative fluids (R-134a, R-32/134a (30/70%), R-407C,

and R-410A) at operating conditions typical for a residential air conditioner .

The zeotropic mixtures, R-407C and R-32/134a (30/70), have the closest

performance characteristics to R-22, with R-32/134a having a slightly better

COP. The important operating parameters (evaporator and condenser

pressures and compressor discharge temperature) did not deviate significantly

from the R-22 values. Also, the low-pressure R-134a had a COP comparable

to the R- 22 COP, but it had a much lower capacity. The binary near-

azeotrope, R-410A, displayed a 44% higher capacity than R-22 when tested at

the same compressor rpm. At a reduced compressor speed at which R-410A

capacity matched that of R-22, the COP of R-410A was 22% better than the

COP of R-22. However, it has to be realized that this COP improvement

resulted from significantly lower pressure losses (especially in the evaporator,suction line, and at compressor valves), and from reduced friction losses in

the compressor running at a lower speed.

Payne and Domanski (2002) tested with R-410A in a R-22 based split

air-conditioning systems with outdoor temperature ranging from 27 to 55 oC.

The capacity and efficiency of both systems decreased linearly with

increasing outdoor temperature. The capacities of both systems were

approximately equal at 35 oC whereas at 55 oC outdoor temperature, the R-

410A capacity was reduced by 9% compared to that of R-22. The

performance of R-410A was degraded more than R-22 when ambient

temperature gets increased more than 68 0C due to its lower critical

temperature.


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Li et al. (2002) studied the performance of high temperature hot water

heat pump with non-azeotropic refrigerant mixture R-22/R-141b. the results

shows that the coefficient of performance is maximum when the molar

component of R22 is about 75%. It is shown that the maximum pressure of

the system is under 2.5 MPa after taking R-22/R-141b as working fluids, even

though the highest cooling water temperatures is about 80 oC

Rakhesh et al. (2003) experimentally studied the performance of R-

407C and R-407A as alternatives for R-22 in a heat pump. The results

reported that R-22 gives highest overall COP at all condensing and evaporator

temperatures. The overall COP of R-407C is slightly higher than R-407A. At

low evaporator temperature, the performance of R-407C and R-407A are

comparable. The isentropic efficiency is highest for R-22 and lowest for R-

407A. The volumetric efficiency of the compressor is highest for R-22 and

lowest for R-407C. The heating capacity is highest with R-22 followed by R-

407C and R-407A. The variation of cooling capacity is highest with R22 and

lowest with R-407A at all temperatures.Aprea and Greco (2003) reported that Performance evaluation of R22

and R407C in a vapour compression plant with reciprocating compressor. The

investigation has revealed that R22 performs better than R407C mainly

because of a better compression process due to a number of factors, including

the facts that the isoentropic and volumetric efficiencies of the semi-hermetic

compressor are better than that of R407C.

Calm and Domanski (2004) reported that R-410A and R-407C are the

leading replacements for R-22 in unitary air conditioners and heat pump

applications.

Spatz and Motta (2004) made a thermodynamic analysis, comparison

of heat transfer and pressure drop characteristics, system performance

comparisons using a validated detailed system model, safety issues, and


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determination of the environmental impact of refrigerant selection. Three

potential alternatives to the R-22 were studied: two HFCs (R-404A and R-

410A) and one HC (R-290). He concluded that R-410A was shown to be

an efficient refrigerant in this application due in large part to its thermal

properties resulting in improved heat transfer and pressure drop

characteristics .The R-290 systems efficiency was also quite good. Using the

assumptions stated in this paper and in a similar system. The enhanced

R404A system also shows favorable efficiency characteristics especially at

average operating conditions.

Thorough examinations of all the fluid properties of R-290 lead to the

conclusion that systems employing this refrigerant would have comparable or

slightly better efficiency (


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23

mode operation in order to improve heating capacity. For cooling mode

operation, it is desirable to adjust the refrigerant composition to in order to

obtain the highest COP and to reduce the energy consumption.

The performance of an air to water vapor compression heat pump has

been investigated experimentally. The main purpose of this study was to

investigate the possibilities of using R134a as a working fluid to replace R-22

for vapor compression heat pumps. Pure R-22, pure R134a and some binary

mixtures of R-22/R134a were considered as working fluids by Karagoz

(2004). His results indicated that the COP of pure R134a is higher than that

pertaining to pure R-22.The mixture ratio has the greater effect on the COP

values. Generally, minimum COP occurs at a zero mass ratio of R134a, and as

the concentration of R134a increases, the COP increases until the mixture

ratio of 50/50% R134a/R-22. The maximum COP occurs at a mixture ratio of

around 50/50% R134a/R-22.The COP increases with increasing evaporator

source inlet temperature for the pure refrigerants and refrigerant

mixtures.R134a and zeotropic mixtures of R134a/R-22 can be a substitute forR-22.

Szen et al. (2004) predicted the performance of the heat pump was

using a fuzzy-logic controller under various working-conditions and mixing

ratios of R12/R22 refrigerant mixtures, instead of requiring an expensive and

time consuming experimental. Fuzzy-logics linguistic terms provide a

feasible method for defining the performance of the heat pump. Input data for

the fuzzy logic are mixing ratio, evaporator inlet temperature and condenser

pressure. In the comparison of performance, results obtained via analytic

equations and by means of the fuzzy-logic controller, the coefficient of

performance (COP), and rational efficiency (RE) for all working situations

differ by less than 1.5% and 1%, respectively. The statistical coefficient of

multiple determinations (R2-value) equals to 0.9988 for both the COP and the


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24

RE. With these results, we believe that fuzzy logic can be used for the

accurate prediction of the COP and the RE of the heat pump.

Cabello et al. (2004) reported an experimental evaluation of a vapour

compression plant performance using R-134a, R-407C and R-22 as working

fluids. The conclusion was the mass flow rate evolution becomes the most

important influence on the refrigerating capacity behavior. With reference to

the electrical power consumption, 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.

Aprea et al. (2004) reported An analysis of the performances of a

vapour compression plant working both as a water chiller and a heat pump

using R22 and R417A.The experimental verified experimentally that the COP

and the exergetic efficiency of the plant, when the R22 is used as working

fluid, are higher than the COP and the exergetic efficiency obtainedconsidering as working fluid the R417A, both when the plant operates as a

heat pump and as a water chiller. In particular, the efficiency defects of

R417A are always higher than the defects of R22 of about 6% related to the

valve and the heat exchangers, and of about 10% referring to the compressor.

Moreover, it has been experimentally verified that the COP of R22 is higher

than that of R417A also of about 18% related to the water chiller system and

of about 15% referring to the heat pump.

Because of the potential variation of the fluid composition, lots of

designers are concerned by the use of zeotropic refrigerant mixtures in

refrigeration and air-conditioning systems. Idrissi et al. (2005), reported a

local simulation model of a water-to-water heat pump is proposed by adopting

a modular approach. Thus, the overall model consists of the association of an


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25

elementary model for each basic component, namely the compressor,

condenser, evaporator and receiver. Implemented with a ternary zeotropic

blend R-134a/R-125/R-32. The numerical results show that, compared to the

nominal composition of R-407C (R- 134a/R-125/R-32; 52/25/23%), the

circulating composition in the machine is low in the less volatile component

R-134a (-3% absolute variation) and rich in the most volatile component R-32

(+3% absolute). In the regions of condensation beginning and evaporation

end, the local composition is noticeably different from both the circulating

and nominal compositions. In these regions, the local mass composition of R-

134a increases (+4/+10% absolute) whereas the local mass composition of R-

125 and R-32 are in deficit (-3/-6% absolute).

Devotta et al. (2005) reported that retrofitting R22 systems with

R407C is a better option to extend the life of R22 systems even though the

performance is slightly lower.

Han et al. (2007) investigated with ternary mixture composed of

R32/R125/R161 as an alternative to R407C. It has been reported that,pressure ratio, power consumption are found to be lower than R407C. The

above mixture has high refrigeration capacity and coefficient of performance

compared to R407C. The discharge temperature also was found to be slightly

higher than R407C.

The exergetic method of analysis is a useful tool in explaining the various

energy flows in a process and in the final run helps to reduce losses occurring

in the system. Arora et al. (2008) explained the method of carrying out an

exegetic analysis of an actual vapour compression refrigeration (VCR) cycle.

A computational model has been developed for computing coefficient of

performance (COP), exergy destruction, exergetic efficiency and efficiency

defects for R502, R404A and R507A. The present investigation has been

done for evaporator and condenser temperatures in the range of -50 0C to 0C


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26

and 40 0C to 550C, respectively. The results indicate that R507A is a better

substitute to R502 than R404A. The efficiency defect in condenser is highest,

and lowest in liquid vapour heat exchanger for the refrigerants considered.

Assaf et al. (2011) presented Modelica-based modelling and simulation

of dry-expansion shell-and-tube evaporators working with alternative

refrigerant mixtures. The model is experimentally validated using a standard

shell-and-tube evaporator working with HFC-134a.he It is concluded that the

effect of the temperature profile of any refrigerant mixture can be substantial

on the relative performance of a particular heat exchanger configuration

compared to counter-flow configuration.

An experimental research was carried out to investigate the

performance of R-22 and its ozone-friendly alternative refrigerants (R404A

and R507) in a window air-conditioner by Bolaji (2011). He concluded that

R-22 had the lowest pressure ratio and discharge temperature closely followed

by R507. The average discharge temperature obtained using R507 and R404A

were 4.2% and 15.3% higher than that of R-22, respectively. The lowestcompressor power and energy consumption were obtained from R507

retrofitted system. Also, the highest refrigeration capacity and coefficient of

performance (COP) were obtained using R507 in the system. The average

refrigeration capacities of R507 and R404A were 4.7% higher and 8.4%

lower than that of R-22, respectively, while the average COP of R507

increased by 10.6% and that of R404A reduced by 16.0% with respect to that

of R-22. Generally, the investigation has revealed that R507 can be used

successfully as a retrofitting refrigerant in existing window air-conditioners

originally designed to use R-22 in the event of HCFC phased out.


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2.6.4 HFC/HC mixtures as alternative

Kim et al. (1994) experimented with two azeotropic mixtures of

R134a/R290 (45/55 by mass percentage) and R134a/R600a (80:20 mass

percentage). The performance characteristics of the azeotropes are compared

with that of R12, R290, R134a and R22. The cooling and heating capacity of

R290/R134a was greater than that of R22 and COP was found to be lower

than that of R22 and R290. The COP of the R134a/600a mixture is higher

than R12 and R134a. The cooling capacity is also found to be higher than

R134a and R600a. The discharge temperature of the azeotropic mixtures

studied are found be lower than that of R22 and R12.

Maczek et al. (1997) investigated with ternary zeotropic mixture

composed of R744/R32/R134a as an alternative for R22 in a heat pump. It has

been reported that above mixture with mass fraction (7:31:62) showed an

increase in capacity and COP by 18.6% and 2.5% respectively. This mixture

was found to be promising alternative only for low temperature heat pump

applications because of its excessive condensing temperature.Payne et al. (1998) compared the performance of R22, R290 and the

flammable zeotropic mixtures R32/R290 and R32/R152a in a residential

water-to-water heat pump. In cooling mode at constant capacity R32/ R290

(50:50) mixture produced 8% higher COP than R22. In heating mode, the

COP of R32/R290 was 13% lower and the COP of R290 was 1% higher than

that of R22 in the water to air system. R290 shows the best performance

compared to the other fluids due to its zero environmental impacts, thermo

physical properties and oil solubility.

Yang et al. (1999) investigated with HFC/HC ternary mixtures

(R32/R125/R152a and R32/R125/R290) and binary mixtures (R125/R290 and

R32/ R290) as alternatives to R22. Their experimental investigations reported


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that performance of R32/R125/R152a mixture was found to be close to R22

over wide range of operating conditions and also have better efficiency.

Aprea et al. (2004) made performance study of vapor compression

plant working as water chiller and heat pump using R22 and its substitute

R417A. It has been reported that R417A does not require a change of

lubricant and it is quite compatible with mineral oil, alkyl-benzene and ester

oils. The compression ratio of R417A is higher than R22 in both the cases.

The COP of the R22 is higher than that of R417A of about 18% in the case of

water chiller and 15% in the case of heat pump applications. The discharge

temperature of R417A was also found to be lower than R22 in both chiller

and heat pump applications. It is observed that the exergy destroyed in the

components of the plant working with R417A as working fluid are greater

than the exergy destroyed while using R22 on an average of about 14%.

Experimental investigation with R407C with 10% and 20% HC blend

composed of 45% of R290 and 55% of R600a (by weight) as an alternative in

window air conditioners without changing the mineral oil.Jabaraj et al. (2006) it has been reported that 19% increase in

condenser tube length is required to suit the mixtures as compared to R22.

The experimental results reported that R407C with 20% HC blend was found

to be the promising alternative to R22 in window air conditioners without

changing the mineral oil.

Calm (2006) has investigated 28 different pure refrigerants for chiller

applications. The results reported that R123 remains the best current option to

reduce the substantial global warming contributions from chiller and air

conditioning applications. R123 has low ODP and very low GWP, very short

atmospheric lifetime and the highest energy efficiency of all the current

options.


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A review reported by Mohanraj et al. (2009).about the various

experimental and theoretical studies carried out around the globe with

environment friendly alternatives such as hydrocarbons (HC),

hydroflurocarbons (HFC) and their mixtures, which are going to be the

promising long-term alternatives. In addition, the technical difficulties of

mixed refrigerants and future challenges of the alternatives are discussed. The

problems pertaining to the usage of environment friendly refrigerants are also

analyzed. he concluded that the Researchers from various parts of the world

reported the experimental and theoretical results with environment friendly

alternatives. Based on the results regarding the performance, it can be

understood that 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 R-22 in air conditioning and heat pump applications. R123 was found to

be an attractive alternative to R11, R12 and R-22 in chiller applications.

R152a and HC mixtures are found to be a best option for automobile airconditioners. The use of low environmental impact refrigerants like the

natural refrigerants (R290, R1270 and R744) and HC/HFC refrigerants in air

conditioning and heat pump applications play a vital role in the developing

countries India for reducing the environmental impact of halogenated

refrigerants.

Torrella (2010) presented an on-site experimental study of the R-22

replacement by two possible substitutes, the HFC-417A and the HFC-422D,

in a water chiller in which the energy performance was evaluated. This chiller

is part of the centralized HVAC system of a lecture room building at the

Jaume I University of Castellon, Spain. This communication compares and

analyses main operation parameters of the chiller when operating with each

refrigerant in real conditions. From the experimental measurements, it was


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observed that the evaporating and condensing temperatures were different

when working with each refrigerant. Accordingly, this difference in pressures

and compression ratios must be taken into account for more accurate

comparisons. It was observed a drop-in cooling capacity and in compressor

power consumption with regard to the operation with R-22 when the chiller

worked with any of the substitute refrigerants. That fact is also to be

considered in the R-22 substitution process.

An experimental investigation of the global environmental impact of

the R-22 retrofits with R422D by Aprea and Maiorino (2011).They

concluded that the storage investigation have demonstrated that for each test

the R-22 retrofit with R422D leads to an increase of the energy consumption

up to 28.9%.Since the GWP of R422D is much higher than that of R-22 and

even if the charge of R422D is 8% lower than that of R-22, the direct effect of

the R422D is 42% higher than that of R-22.As a consequence of the retrofit

with R422D, the plant investigated has shown an increase of TEWI up to

36.8%.The performance investigation highlighted that the operation withR422D is less efficient than that with R-22. In particular, the difference

between the COP for R-22 and that for R422D is, on average, 20%, and it

grows with the raising of the air temperature of cold reservoir.R-22 retrofit

with R422D leads to an increase of the condensing Pressure, which indicates

that the heat exchange surface of the condenser is insufficient to reject the

thermal power, worsening the efficiency. To improve the energy performance

and then to reduce the indirect effect, we proposed two ways: increasing the

heat exchange surface and adoption of electronic expansion valves. Based on

theoretical considerations it is possible to obtain a 20% reduction of energy

consumption.

Experimental evaluation of HCFC-22 replacement by the drop-in fluids

HFC-422A and HFC-417B for low temperature refrigeration applications


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carried by Llopis et al (2011). A double stage vapour compression plant with

sub cooler, in an evaporating temperature range from -31 and 17oC and in a

condensing temperature range from 30 and 48oC was used. The experimental

results showed that when using any of the drop-in fluids there is an important

increment on the refrigerant mass flow rate through the plants, which in some

cases would need to readjust the expansion valves. However, with the

substitutes there is an important reduction of the specific refrigerating effect,

which tends to reduce the cooling capacity. Regarding the energy

performance with the R-22 drop-in fluids it has been measured a reduction in

the capacity in the plant, being this reduction higher than expected from a

theoretical analysis. Furthermore, regarding the COP in medium and low

evaporating temperatures, the reduction with the R-22 substitutes is important

and higher to the values predicted with a theoretical analysis.

La Rocca and Panno (2011). presented an experimental analysis

comparing the performance of a vapour compression refrigerating unit

operating with R-22, and its performance in comparison to a new HFC fluid,R-417A, R-422A and R-422D. Results revealed that R-22 was energetically

more efficient than the other fluids. R-417A, R-422A and R-422D are

characterized by ODP = 0 and in the existing installations they can easily

replace R-22 without having to change the lubricant, or renewing the

refrigeration circuits and the accessories. This makes replacement a

particularly easy operation that can be carried out without any special

technical equipment and at a very low cost. Change in energy performance as

a result of a R-422D retrofit.

An experimental analysis for a vapor compression refrigeration plant

for a walk-in cooler was studied by Aprea et al. (2011). The results

demonstrated that the cooling capacity for R422D was lower than for R-22,

while the electrical power absorbed with R422D was higher than that with


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R-22. As consequence, the COP of R422D was lower than that of R-22.

Furthermore, technical proposals are introduced with the aim of retrofitted

with R422D.

Llopis et al. (2012) R-22 replacement with two drop-in fluids (R-

422A, R-417B) and a retrofit refrigerant (R-404A) in a two-stage refrigeration

plant for low temperature. The experimental measurements showed that when

using any of the substitute fluids there is an important incremental difference

in the refrigerant mass flow rate through the plant, which in some cases would

make it necessary to readjust the expansion valves of the system. An

important reduction in the capacity has been measured when using the drop-in

fluids R4-22A and R-417B, whereas, for the retrofit refrigerant R-404A the

capacity is enhanced to an important degree. Regarding the COP of the plant,

the reduction in COP with any of the tested fluids is important and is greater

than the values predicted by a theoretical analysis.


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2.8 Physical Environmental and Safety Characteristics of R-22 , R-438A and

R-422A

Table (2-2) shows composition and main thermodynamic properties of

R-22 and its substitutes fluids considered in this work R-438A and R-422A

while their p-h diagrams are shown in Fig. (2.6-a) and Fig. (2.6-b),

respectively. The pressure levels of R-43a and R-422A are higher than

corresponding pressures in R-22 higher and medium temperatures. Hence,

R-438A andR-4 22A are better to replace R-22 for air conditioning

applications than lower temperature applications. Furthermore, R-438A and

R-422A have a temperature glide, which makes them unsuitable for flooded

evaporators. Another important difference is that there is an important

reduction in the latent heat of phase change (h fg) as compared to R22, which

will tend to reduce the capacity provided by the plants.


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Table (2.2): Physical Environmental and Safety Characteristics of R-22 , R-

438A and R-422A (Elgendy et al.,2014)

R-422AR-438AR-22

85.1% R-1258.5% R-322CHCIFComposition (%wt)

11.5% R-

134a

45% R-125

3.4% R-60044.2% R-134a

1.7% R-600

0.6% R-610a

113.699.186.47Molecular weight (g mol-1)

-44.03-42.33-40.81Normal boiling point (C)71.7385.2796.14Critical temperature (C)

37.464349.9Critical pressure (bar)

2.466.190Glidea (C)

167.44203.7226.81hfg (T=-30C)

140.6176.9200.9hfg (T = 5C)

104.8140.3166.60hfg (T = 40C)

0.08620.1430.135g (T=-30C) (m3 kg-1)

0.02480.03860.0403g (T=5C) (m3 kg-1)

000.05ODP

310022651810GWP (100 years)

A1A1A1ASHRAE Safety group


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Fig. (2.6-a) Pressure -enthalpy diagram of the R-22 and its drop-in R-438A.

Fig. (2.6-b) Pressure -enthalpy diagram of the R-22 and its drop-in R-422A.

100 200 300 400 500

Specific enthalby (kJ/kg)

1

10

100

Pressure(bar)

R-22

R-438A

T=40C

T=-25C

T=5C


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2.8 Concluding Remarks

The literature survey revealed that although many investigations were

carried out on airconditioner working with R22 alternatives, Both R-410A

and cant be consider as a drop-in and a little work was conducted on an air

conditioner running with R-422A and no investigation was carried for R-

438A to evaluate its performance at various operating conditions. Moreover,

previous investigators did not explore its effect even for water to water chiller

using R-422A and R-438A. However, there is a lack of information on the

performance characteristics of water to water chiller using R-422A and R-

438A.Therefore, the present work aimed at evaluating the performance

characteristics of a vapor compression water chiller for various operating

conditions. A comparison, based on energy points of view, is considered

among R-22 alternatives as working fluids in water chiller. An experimental

apparatus was designed, constructed and equipped with necessary

instrumentation. R-22, R-422A or R-438A is used as a primary working fluid

and water is adopted as the secondary heat transfer fluid at both the condenserand evaporator. Influences of evaporator water inlet temperature, condenser

water inlet temperature and condenser water flow rate on the performance

characteristics of the system is experimentally investigated.

msc in ref

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