Chapter - 2

Conventional and Alternative Refrigerants - an

overview

There are a variety of factors that affect the choice of refrigerant for new equipment.

These include thermodynamic, chemical, safety and environmental properties, as well

as practical and market implications such as cost, global availability of the fluids and

system components, and technical familiarity of engineers and technicians. In

particular equipment producers tend to consider the offset between GWP and

flammability/toxicity according to the intended product market. Another important

factor for manufacturers adopting new refrigerants are modifications to production

processes, system design and component construction, all of which can impose

significant costs on new RAC equipment. These factors are more relevant to larger,

global manufacturers where they are seen to employ fewer refrigerant types whereas

smaller producers exhibit greater diversification in their choice.

2.1 Refrigerant groups

Apart from the natural refrigerants, the following are the major category of chemicals

which are being used/proposed as refrigerants.

CFCs - chlorofluorocarbons

HCFCs - hydrochlorofluorocarbons

HFCs - hydrofluorocarbons

HCs - hydrocarbons

FCs - fluorocarbon

In organics

HFEs - hydrofluoroethers

FICs - fluoroiodocarbons

HFOs - fluoroalkenes

Blends and Mixtures

In many countries, the most common refrigerant options for new systems are

presently HFCs, HCs, ammonia and carbon dioxide. Table 2.1 lists the specific fluids

15

based on an international assessment report produced under the Montreal Protocol

(UNEP, 2002), and the previously used CFCs and HCFCs are also included for

comparison. It is important to note that older equipment that was produced with

HCFCs and particularly CFCs poses problems when subject to repairs. If it is not

possible to use the existing ODS refrigerant because of restrictions, several options

are considered:

• replacement of old systems with new ones designed with a non-ODS refrigerant.

• "retrofit" where the old refrigerant is replaced with a non-ODS one but accompanies

with oil and material change due to compatibility issues.

• "drop-in" where the old refrigerant is simply swapped with a non-ODS refrigerant.

The first option is the most costly, but offers other benefits such as more efficient

systems and reduced maintenance. The retrofit option may include changing to an

HFC, which requires some time and expenditure to remove all the mineral oil and

certain materials from the system and replace them with those suitable for use with

HFCs. Using a drop-in refrigerant (typically involving mixtures of HFCs with PFCs

and HCs) is the cheapest and most accessible option. It is also possible to drop-in

using pure HCs, but this involves modifications to equipment so that the safety

features required by standards are addressed.

A comprehensive list of refrigerants is provided in Table 2.1, including basic

information on composition, normal boiling point (NBP), safety and environmental

data.

2.1.1 Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons

(HCFCs)

CFCs and HCFCs were the standard refrigerants for most RAC applications, and R12

and more so R22 are the reference fluids for the development of new refrigerants. The

Belgian chemist Frederic Swarts ( 1892 - 1907) described the properties of

synthetically produced CFCs. Later, Thomas Midgley ( 1929) of General Motors

patented the compounds and technical applications begin. CFCs were developed in

the 1930s and R l l , R12 entered in the market as safe, non-flammable and non-toxic

refrigerants. They were widely used for many purposes like in aerosol insecticides,

deodorant sprays, shaving creams, perfumes, paints, cleaning agents in textile and

electrical industries, blowing agents etc., until it was confirmed in the 1980s that

16

they were the main source of harm to the ozone layer. The most common ozone

depleting refrigerants are R12 (CFC) and R22 (HCFC). In 1970 only, the British

scientist James E Lovelock detected the presence of R 11 in atmosphere. The

California University in 1974 published that CFCs could be destroying ozone layer. A

ban was imposed in USA in 1978 for the use of R l 1 and R12 in aerosols except for

pharmaceutical applications. Various companies sell the same CFCs, HCFCs, HFCs

and other products under different names. Freon is a trade name for CFC and HCFC

refrigerants used by DuPont. Technically speaking, Freon is a trademark used by the

DuPont Corporation for their line of refrigerant products. In general, CFCs and

HCFCs have broad compatibility with many materials, adequate solubility with most

types of refrigeration oils (although most often used with mineral oils) and are

relatively tolerant of contaminants in the system. Amongst the various fluids in these

groups, a wide range of pressure/temperature characteristics are available and their

favourable thermo physical properties result in good cycle/system efficiency.

2.1.2 Hydrofluorocarbons (HFCs)

HFCs such as R134a, R404Al and R407C have dominated the replacement of CFCs

and HCFCs, mainly because they broadly possess similar chemical, thermodynamic

and flammability/toxicity characteristics as well as having been extensively marketed

by manufactures. However HFCs are more difficult to apply because of poor

compatibility with construction materials and in particular mineral oils, which has

meant that certain synthetic lubricants, typically polyolesters (POEs) and

polyalkylglycols (PAGs) have to be used instead. Moreover, they are less tolerant to

contaminants within the system. Most HFCs are used in binary or tertiary mixtures,

partially to suit certain desired operating characteristics such as replicating R22.

HFCs tend to have low toxicity and are largely non-flammable, although a couple of

fluids, such as R32 and R152a that are used in several blends are flammable. In terms

of environmental impacts, although HFCs have a negligible ODP they do retain the

high GWP characteristic of most fluorinated refrigerants, hence the introduction of

certain legislation. Of lesser importance are some other environmental impacts

associated with HFC production and emissions, including the release of ozone

depleting substances during their manufacture and the production of trifluoroacetic

acid as a decomposition product which is highly persistent and bio-accumulative may

be harmful to aquatic life.

17

2.1.3 Hydrocarbons (HCs)

HC refrigerants include a broad range of substances (e.g., R600a and R290) that cover

the range of pressure-temperature characteristics of the conventional CFC and HCFC

fluids and they have been used since the evolution of mechanical refrigeration. This

has been recognized as environmentally conscious, whilst energy savings have been

outstanding, about 40 %. Also their good material compatibility and solubility with

lubricants is comparable to that of the CFCs. Certain thermo physical properties do

differ from the fluorinated fluids, particularly in terms of lower density and higher

latent heat. The most significant property associated with HCs is that they are all

flammable (but low toxicity), which means that certain safety measures not normally

applied to refrigeration and air conditioning equipment must be adhered to.

Hydrocarbons are highly flammable and when released, contribute to the lower

atmospheric ozone pollution (photochemical smog). Apart from this issue, their ease

of application, good efficiency and negligible GWP makes them attractive

refrigerants. Hydrocarbons such as isobutene, butane and propane are used in some

small charge systems such as domestic appliances and small air-conditioners.

Chinese refrigerator design and manufacture is being geared to hydrocarbon

technology instead of the American HFC chemical refrigerants. The first Australian

hydrocarbon refrigerator, using 'Greenfreeze' technology was produced by Email in

1995. Greenfreeze has become the dominant refrigerator technology in Europe. Many

models of Greenfreeze refrigerators are now on sale in Germany, Austria, Denmark,

France, Italy, Netherlands, Switzerland and Britain. 'MUSICOOL' is an established

hydrocarbon refrigerant by PT Pertamina - Indonesia. It is used in motor vehicle air­

conditioning, split/window systems, water dispensers and cold storage systems,

mostly in Australia, Canada, Europe, Japan and US. Hydrocarbon based refrigerators

are available in India, also.

2.1.4 Carbon dioxide (R744)

Carbon dioxide (CO2) is another fluid that has been used as a refrigerant in vapour

compression systems of many types for over 130 years, but it is only in the last

decades that inventive minds and modern techniques have found new ways to exploit

the uniquely beneficial properties of this remarkable substance. Carbon dioxide was

probably the cheapest available refrigerant. One system patent even describes it as a

18

by-product of the production of calcium chloride, used as the brine for the ice-maker

[l]. It has good chemical compatibility with common materials and relatively good

solubility with a number of oils. Whilst non-flammable, CO2 is toxic at moderate

concentrations, particularly above 5% by volume in air. Also, CO2 has no ozone

depletion potential, negligible GWP and has no other serious environmental problems

associated with it.

The notable difference between CO2 and other common refrigerants is its pressure

temperature characteristics, and in particular a low critical temperature. This means

that it either operates with a limited (low) condensing temperature, or it must be used

in a "transcritical" or "supercritical" cycle that differs from conventional compression

cycles. In a transcritical cycle the refrigerant in a supercritical state is discharged from

the compressor and enters a "gas-cooler" (rather than a condenser) where its

temperature is reduced before being expanded into a liquid and vapour state, usually

in the evaporator. CO2 also operates at significantly higher pressures and has a very

high latent heat when compared to most conventional refrigerants. The basic

transcritical cycle is potentially less efficient than a conventional compression cycle

because it suffers from larger thermodynamic losses. Higher heat rejection

temperatures result in greater throttling losses and so the theoretical cycle work

increases and refrigerating capacity is reduced. Although the excellent thermo

physical properties of CO2 mean that performance within the heat exchangers and

compressor are generally better than with conventional refrigerants, it is not always

sufficient to overcome the additional losses associated with transcritical operation.

This is manifest in the significant research efforts on means to improve cycle

efficiency, such as development of expanders (instead of expansion valves), ejectors

and interchangers so that losses can be recovered.

2.1.5 Ammonia (R 717)

Ammonia has been used a lot in freezing works and large cold-stores continuously for

many years and is well understood. Unlike HCFC, HFC and HC refrigerants,

ammonia (in the presence of small amounts of contaminants) is incompatible with a

number of materials otherwise commonly used in refrigeration systems, and it is

immiscible with most lubricants. The pressure temperature characteristics of ammonia

are similar to R22, whilst the latent heat is significantly greater than most fluorinated

fluids. Ammonia also possesses favourable thermo physical properties, resulting in

19

good efficiency. There are safety implications with ammonia both in terms of toxicity

(although perceived to be much more severe due to its pungent smell) and moderate

flammability. On the other hand it has negligible environmental impacts, i.e., no ODP

and noGWP.

2.1.6 Mixtures and other fluids

There are a number of available mixtures that may contain various components

including HFCs, HCFCs, HCs, FICs, HFO, and PFCs. These mixtures are generally

produced for the purpose of drop-in or retrofit refrigerants. The inclusion of HCFCs

or HCs is to provide some solubility with the mineral oils that are used in existing

CFC or HCFC systems. In other cases, such mixtures are developed to match

particular characteristics of a specific refrigerant that it is intended to replace, or to

achieve an improvement in cycle efficiency.

Given the possible number of combinations of the various fluids mentioned above, the

extent of different characteristics is vast. Mixtures fall into two categories: azeotropes

(refrigerants with R5XX designation) and zeotropes (with R4XX designation).

Azeotropes behave more or less identically to pure fluids, whereas zeotropes exhibit

certain unique characteristics particularly during change of phase. In flooded systems,

zeotropes will demonstrate a composition change due to the different vapour

pressures of the refrigerant components and a larger difference in vapour pressures

normally causes a greater extent of composition change. As the system operates, the

component(s) with a lower boiling point accumulate within the high pressure side,

and higher boiling point component(s) shift to the low pressure side of the cycle.

Consequently compression ratio increases, refrigerating capacity reduces leading to a

degradation in system efficiency. In flooded systems, the degree of composition

change causes sufficient disruption to the performance of the cycle that they are not

recommended for use.

In direct expansion (DX) systems composition change occurs to a much smaller

extent and instead the range of component vapour pressures is exhibited as a variation

in saturation temperature across the phase change, which is known as "glide".

Temperature glide for common refrigerants ranges from 0.5 K to about 10 K, and for

a given mixture it gets smaller as the saturation pressure I temperature approaches the

critical point. In DX systems, glide can be suitably accommodated provided that heat

20

exchanger design is addressed. Another impact of the use of a mixture is degradation

of two-phase heat transfer in the evaporator and condenser, occurring because of the

differential rate of phase change between the refrigerant components.

R- Composition NBP (°C) Safety PL LFL

ODP GWP

number group {kg/m3

) (kg/m3)

R-11 R-11 (CFC) 24 A1 0.3 - ·1 3800

R-12 R-12 {CFC) -30 A1 0.5 - 1 8"100

R-1281 R-12B1 (BCFC) -4 - 0.2 - 3 1300h

R-13 R-13 (CFC) -8·1 A1 0.5 - 1 14000

R-138·1 R-1361 (BFC) -58 A1 0.6 - 10 5400

R-14 R-14 (PFC) -128 A1 nfa - 0 6500

R-22 R-22 (HCFC) -41 A1 0.3 - 0.055 1500

R-23 R-23 (HFC) -82 A1 0.68 - 0 11700

R-30 R-30 (HCC) 40 82 0.017 0.417 0 9

R-32 R-32 (HFC) -52 A2 0.061 0.306 0 650

R-50 R-50 (methane) -161 A3 0.006 0.032 1 21

R-113 R-113 (CFC) 48 A1 0.4 - 0.8 4800

R-114 R-114 (CFC) 4 A1 0.7 - 1 9800h

R-115 R-115 (CFC) -39 A1 0.6 - 0.6 7200h

R-116 R-116 (PFC) -78 A1 0.55 - 0 9200

R-123 R-123 (HCFC) 27 81 0.1 - 0.02 90

21

R-Composition NBP (°C)

Safety PL LFL ODP

GWP number group (kg/m

3) (kg/m3)

R-124 R-124 (HCFC) -·12 A1 0.11 - 0.022 470

R-125 R-125 (HFC) -49 A1 0.39 - 0 2800

R-'134a R-134a (PFC) -26 A1 0.25 - 0 '1300

R-141b R-141b (HCFC) 32 B2 0.0'13 0.43 0.11 600

R-142b R-142b (HCFC) -10 A2 0.066 0.329 0.065 '1800

R-143a R-143a (HFC) -47 A2 0.056 0.282 0 3800

R-152a R-152a (HFC) -25 A2 0.026 0.13 0 '140

R-170 R-170 (ethane) -89 A3 0.008 0.038 0 3

R-1150 R-1 ·150 (ethene) -104 A3 0.007 0.036 0 3

R-EHO R-E170 (dimethyl ether) -25 A3 0.013 0.064 0 -

R-218 R-218 (PFC) -37 A1 0.44 - 0 7000

R-227ea R-227ea {HFC) -16 A1 0.49 - 0 2900

R-236fa R-236fa (HFC) -1 A1 0.59 - 0 6300

R-245fa R-245fa (HFC) 15 B1 0.19 - 0 950

R-290 R-290 (propane) -42 A3 0.008 0.038 0 3

R-1270 R-1270 (propene) -48 A3 0.008 0.040 0 3

R-365rnfc R-365rnfc (HFC) 40.'I - - - 0 890

R-43-54.6 A1 0 '1500 10rnee R-43-10mee (FC)

- -

R-C3'18 R-C318 (PFC) -6 A1 0.81 - 0 8700

R-600 R-600 (butane) 0 A3 0.0086 0.043 0 3

R-600a R-600a (isobutane) -·12 A3 0.0086 0.043 0 3

R-601 R-601 (pentane) 36 A3 0.008 0.041 0 3

R-601a R-60'1a (isopentane) 28 A3 0.008 0.041 0 3

R-717 R-717 (ammonia) -33 B2 0.00035 0.104 0 0

R-744 R-744 (carbon dioxide) -78 A1 0.07 - 0 ·1

R-401A R-22/152a/124 -34.4/-28.8 A1 0.3 - 0.037 970

R-40'18 R-22/152a/124 -35.7/-30.8 A1 0.34 - 0.04 '1060

R-401C R-22/152a/124 -30.5/-23.8 A1 0.24 - 0.03 760

R-402A R-125/290/22 -49.2/-47.0 A1 0.33 - 0.02·1 2250

R-4026 R-125/290/22 -47.2/-44.9 A1 0.32 - 0.033 '1960

R-403A R-290/22/218 -44.0/-42.3 A1 0.33 - 0.041 2520

R-403B R-290/22/218 -43.8/-42.3 A1 0.41 - 0.031 3570

R-404A R-125/143a/134a -46.6/-45.8 A1 0.48 - 0 3260

R-405A R-22/152a/142b/C3'18 -32.9/-24.5 A1 0.26 - 0.028 4480

R-406A R-22/600a/142b -32.7/-23.5 A2 0.13 0.302 0 057 '1560

R-407A R-32/125/134a -45.2/-38. 7 A1 0.33 - 0 ·1770

R-4076 R-32/125/'134a -46.8/-42.4 A1 0.35 - 0 2280

R-407C R-32/125/134a -43.8/-36. 7 A1 0.31 - 0 1520

22

R-Composition NBP (°C)

Safety PL LFL ODP

GWP

number group (kg/m3

) (kg/m3

)

R-4070 R-32/125/134a -39.4/-32.7 A1 0.41 - 0 1420

R-407E R-32/125/134a -42.8/-35.6 A1 0.40 - 0 1360

R-408A R-125/143a/22 -45.5/-45.0 A1 0.41 - 0.026 2650

R-409A R-22/124/142b -35.4/-27.5 A1 0.16 - 0.048 ·1290

R-409B R-22/124/142b -36.5/-29.7 A1 0."17 - 0.048 1270

R-410A R-32/125 -51.6/-51.5 A1 0.44 - 0 1720

R-410B R-32/125 -51.5/-51.4 A1 0.43 - 0 1830

R-41 "IA R-1270/22/152a -39.7/-37.2 A2 0.04 0.186 0.048 "1330

R-41 "1B R-1270/22/152a -41.6/-41.3 A2 0.05 0.239 0.052 '1410

R-4·12A R-22/218/142b -36.4/-28.8 A2 0.07 0.329 0.055 "1850

R-4'13A R-2 ·18/134a/600a -29.3/-27.6 A2 0.08 0.375 0 "1770

R-414A R-22/124/600a/142b -34.0i-25.8 A1 0.08 - 0 045 ·1200

R-4146 R-22/124/600a/'142b -34.4/-26.·1 A1 0.07 - 0 042 1100

R-415A R-22/152a -37.5/-34.7 A1 0.3 - 0 037 970

R-416A R-134a/124/600 -23.4/-21.8 A1 - - 0.009 950

R-417A R-125/134a/600 -38.0/-32.9 A1 0.'15 - 0 '1950

R-500 R-12/152a -33.5 A1 0.4 - 0.74 6000

R-501 R-22/12 -41.0 A1 0.38 - 0.29 3150

R-502 R-22/115 -45.4 A1 0.45 - 0.33 4400

R-503 R-23/13 -88.7 A1 0.35 - 0.6 '13'!00

R-504 R-32/115 -57.0 A1 0.14 - 0.31 4040

R-505 R-12/31 -30.0 A1 0.14 - 0.78 n/k

R-506 R-31/114 -12.0 A1 0.14 - 0.45 n/k

R-507A R-125/143a -46.7 A1 0.49 - 0 3300

R-508A R-23/116 -86.0 A1 0.22 - 0 11860

R-508B R-23/116 -88.3 A1 0.2 - 0 '11850

Table 2.1: Refrigerants with R number designation and selected characteristics [52]

The environmental protection agency EPA through the Clean Air Act is regulating the

production and use of refrigerants. Practically there is no such thing as a perfect

refrigerant. All candidates, although technically efficient with regards to energy

efficiency for example have undesirable intrinsic properties with regards to health,

safety and the environment.

In response to the Montreal Protocol, alternative refrigerants were sought, and this

search gained importance for a number of existing and new potential substances for

applications (where only CFCs and HCFCs were previously used) like

hydrofluorocarbons (HFCs), hydrocarbons (HCs), ammonia and carbon dioxide.

Simultaneously, attention focussed on the issue of climate change. Subsequently, the

23

Kyoto Protocol was developed under the UN in 1997, which prescribes the limitation

and reduction of emissions of a group of anthropogenic "greenhouse gases" (GHGs):

CO2, nitrous oxide (N20), methane (CH4), HFCs, perfluorocarbons (PFCs) and

sulphur hexafluoride (SF6). Many countries have since published legislation to help

meet the Kyoto targets for emissions reduction. In order to quantify the contribution

of these gases to climate change, the discussions on climate change in 1990 adopted

the use of Global Warming Potential (GWP) of the gas (IPCC, 1990). GWP is a

measure of the insulating properties that a gas has on the heat radiating away from the

surface of the earth, and is relative to the effect of one kilogram of CO2 I Rl 1

Ozone depletion potential (ODP) = amount of 03 depleted by the material I amount

depleted by Rl 1 or R12

Global warming potential (GWP) = warming due to unit mass of material emitted I

warming due to unit mass of CO2 or R 11

Ultimately, the political actions have resulted in a drive by the refrigeration and air­

conditioning (RAC) industry to reduce the environmental impact of systems, manifest

as development of new refrigerants and cooling technologies. The related issues like

refrigerant options, characteristics of alternative refrigerants, environmental impact,

efficiency and applications of alternative refrigerants, refrigerant leakage, recent

developments and technical barriers are also to be addressed along with it.

The number of available refrigerants is vast. Out of about 110 designated refrigerants

(excluding CFCs) only a few are being used extensively in industry. In addition there

are several hundred commercially available fluids that have not been allocated an

R-number to date.

2.2 Refrigeration & Air Conditioning - End use categories

The refrigeration and air-conditioning sector includes eight major end-uses:

•

•

•

•

Domestic refrigeration,

commercial refrigeration

motor vehicle air-conditioning (MV AC),

chillers,

24

•

•

•

•

•

retail food refrigeration,

cold storage warehouses,

refrigerated transport,

industrial process refrigeration, and

residential and small commercial air-conditioning I heat pumps .

Each end-use is composed of a variety of equipment types that have historically used

ODSs such as chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs). As

the ODS phase-out is taking effect under the Montreal Protocol, equipment is being

retrofitted or replaced to use RFC-based substitutes or intermediate substitutes (e.g.,

HCFCs) that will eventually need to be replaced by non-ozone-depleting alternatives.

HCFCs are beginning to be replaced with HFCs or other alternative refrigerants. The

eight major end-uses are explained in more detail below.

2.2.1 Domestic Refrigeration

This end-use consists of household refrigerators and freezers. Following the phase-out

of R12, R134a was adopted within the domestic refrigeration sector in the US and

most developing countries but since then R600a has become the established choice

throughout Europe and much of Asia including Japan. This is primarily because it

enables lower noise levels to be achieved, which is an important factor for residential

environments. In addition, R600a offers a slight efficiency improvement over the

competing fluids suitable for this application and despite the minute likelihood of

leakage its negligible GWP is considered an advantage.

Also hydrocarbon (HC) refrigerant, especially isobutane (R600a) is dominating much

of the European market and continuing to grow in market share. HC systems are

about 40 percent smaller than R 134a (HFC) systems. The equipment has an

expected lifetime of 20 years. This end-use is one of the largest in terms of the

number of units in use; however, because the charge sizes are small and the units are

hermetically sealed (and, therefore, rarely require recharging), emissions are relatively

low. Thus, the potential for reducing emissions through leak repair is small. In most

Annex I countries [47], where regulations are in place that require the recovery of

refrigerant from appliances prior to disposal, the retirement of old refrigerators is not

expected to result in significant refrigerant emissions. Refrigerant emissions at

25

disposal from developing countries, where refrigerant recovery 1s not generally

required, are expected to be greater.

2.2.2 Commercial refrigeration

Commercial refrigeration means the retail food refrigeration systems which include

stand-alone units such as vending machines, ice cream freezers, bottle coolers,

refrigerated equipment found in supermarkets, convenience stores, restaurants, and

other food service retail outlets. Charge sizes range from 6 to 1,800 kilograms, with a

lifetime of about 15 years. Convenience stores and restaurants typically use

standalone refrigerators, freezers, and walk-in coolers. In contrast, supermarkets

usually employ large parallel systems that connect many display cases to a central

compressor rack and condensing unit by means of extensive piping. Because the

connection piping can be miles long, these systems contain very large refrigerant

charges and often experience high leakage rates. During the earlier phases of the CFC

phase-out in developed countries, the use of HCFC-22 in retail food refrigeration was

expanded considerably. Retail food equipment is being retrofitted with HCFC based

blends, although HFC blends are also used as a retrofit refrigerant. Integral units

generally use R134a (mainly for medium temperature applications) and R404A

(mainly for low temperatures). The HFC blend R-404A is the preferred refrigerant in

new retail food equipment in developed countries, while R-507 A is also used

extensively in the market. In developed countries, both distributed and centralized

systems that use HFCs, HCs, ammonia, and carbon dioxide are being developed (both

with and without secondary loops). More recently, the use of R290 and CO2 and to a

smaller extent R600a have been adopted. Remote systems that employ condensing

units or a central multi-compressor pack have become limited to R404A because of

established industry practice.

However, a number of alternative concepts such as indirect and cascade systems are

being installed with increasing frequency, and these allow for the use of HCs, CO2

and ammonia since the various safety implications can be handled in a relatively

straight-forward manner. Stationary air conditioning systems includes small window

and split units, multi-split systems and central chillers that provide cooling water to

air handlers. Most integral and split systems previously used R22 until R407C was

introduced, but the larger manufacturers are now adopting R410A due to smaller

components and marginal gains in efficiency. R290 is also being used because of its

26

favourable environmental characteristics and good efficiency, and for similar reasons

systems using CO2 are being investigated. Although the efficiency of CO2 in a split

type air conditioner has been demonstrated to match that of an R410A system under

most conditions, the technology required to achieve comparable efficiencies at higher

ambient temperatures (i.e., in the transcritical cycle) are likely to be costly. Multi­

split systems are following the trend of shifting from R407C to R410A for much the

same reasons, but HCs are not viable because the significantly higher refrigerant

charges invoke impractical safety measures prescribed by standards. Most chillers for

air conditioning within Europe are positive displacement machines, using

reciprocating, scroll or screw compressors. R22 had been the primary choice for these

chillers, but the most common refrigerants are now R134a and R407C. Some

manufacturers offer chillers using R290, R1270 and ammonia since their installation

outside buildings means that conformity to safety requirements is easier. Heat pumps

are used for heating occupancies and also to produce domestic hot water, and are in

common use in central and northern Europe. These systems had almost exclusively

used R22, but recently most manufacturers have offered units with a selection of

refrigerants including R290, R407C and lately R410A.

2.2.3 Motor Vehicle Air Conditioning (MV AC)

The global warming issue has led the auto industry to take steps to reduce the

emission of green house gases into the atmosphere. But aside from a vehicles IC

engine, it also poses a threat to the environment due to the refrigerants they use on

automobile cooling units. Currently, automobile air conditioning systems uses HFC

134a. The said refrigerant poses a serious threat to the environment because of its

comparable GWP.

The quantity of refrigerant contained in a typical large capacity car air conditioner is

approximately !kilogram-generally from 1 to 1.2 kilograms for vehicles containing

CFC-12 systems, and an average of approximately 0.8 kilograms for vehicles

containing HFC-134a systems - although this varies by car and region. Because of

concerns over the environmental impact of refrigerants, the average charge size of

MV ACs-as well as associated leak rates-have been reduced over time; this trend is

expected to continue. The expected lifetime of MVACs is approximately 12 years.

Refrigerant use in this sector is significant because more than 700 million motor

vehicles are registered globally. In developed countries, CFC-12 was used in MVACs

27

until being phased out of new cars in 1992 through 1994. Since then, all air

conditioners installed in new automobiles use HFC-134a refrigerant. HFC-134a is

also used as a retrofit chemical for existing CFC-12 systems.

CFC-12 availability in developing countries and in some developed countries

(e.g., the United States) has resulted in its use for servicing older MV ACs that were

originally manufactured as CFC-12 systems. A variety of refrigerant blends are

approved for use in the United States by the USEPA as replacements for CFC-12 in

MV ACs. However, these blends have not been endorsed by vehicle or system

manufacturers. Globally, these blends have captured only a small and declining share

of the retrofit market.

There are number of alternative refrigerants from which to choose. One is R-134a,

which is the only alternative refrigerant currently approved by all vehicle

manufacturers for retrofitting older R-12 NC systems. The vehicle manufacturers say

R-134a will cool reasonably well in most R-12 NC systems provided the proper

retrofit procedures are followed. They also recommend R-134a because it is a single

component refrigerant, unlike most of the alternatives which are actually blends of

two to more ingredients. Blends can sometimes undergo "fractionation." This is when

the individual ingredients in a blend separate for various reasons. Fractionation can be

caused by chemical differences between the refrigerants (lighter and heavier elements

do not want to stay mixed), different rates of leakage through seals and hoses (smaller

molecules leak at a higher rate than larger ones), and different rates of absorption by

the compressor oil and desiccant. Fractionation is a concern because it can change the

overall composition of the blend once it is in use, which can affect the performance

characteristics of the refrigerant. Fractionation also makes it difficult to recycle a

blended refrigerant because what comes out of the system may not be the same mix

that went into the system.

2.2.4 Chillers

Chillers are used to regulate the temperature and reduce humidity in offices, hotels,

shopping centers, and other large buildings, as well as in specialty applications on

ships, submarines, nuclear power plants, and other industrial applications. The four

primary types of chillers are centrifugal, reciprocating, scroll, and screw, each of

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which is named for the type of compressor employed. The majority of operating

chillers will remain in service for more than 20 years, and some will last 30 years or

more. A wide variety of chillers is available, with cooling capacities from 7 kilowatts

to over 30,000 kilowatts. The charge size of a chiller depends mostly on cooling

capacity and ranges from less than 25 kilograms (reciprocating) to over 2,000

kilograms (centrifugal). HCFC-123 has been the refrigerant of choice as a retrofit

option for newer CFC-11 units, and HFC-134a has been the refrigerant of choice

as a retrofit option for newer CFC-12 units. The replacement market for CFC-12 high­

pressure chillers and CFC-11 low-pressure chillers is dominated by both HCFC-123

chillers and HFC-134a chillers in developed and developing countries. Following

phase-out of the production of HCFCs (in 2030 for developed countries and 2040 for

developing countries), recycled, recovered, and reclaimed HCFCs will continue to be

used in most countries. This trend is not the case, however in the European Union,

where there are restrictions on the use of HCFCs in new equipment, the production of

HCFCs is not permitted beyond 2010, and recycled HCFCs may not be reused beyond

2015. In the European Union, HFC-134a will be an important option for chillers, but

because of its global warming impact, ammonia chillers are being used as an

alternative in some countries.

Additionally, HFC-245fa is a potential refrigerant for new low pressure chillers. High

pressure chillers that currently use HCFC-22 will ultimately be replaced by several

HFC refrigerant blends and HFC-134a chillers. Likewise, existing CFC-11 chillers

have been converted to HFC-236fa or replaced with HFC-134a chillers, for use

primarily in special applications (e.g., on ships and submarines, and in nuclear power

plants). Recently, the commercial feasibility of the use of water vapour as refrigerant

for vapour compression chillers with a capacity of 1000 TR has been studied in detail

by Brandon et al. [6].

2.2.5 Cold Storage Warehouses

Cold storage warehouses are used to store meat produce, dairy products, and other

perishable goods. The expected lifetime of a cold storage warehouse is 20 to 25 years,

and although charge sizes vary widely with system size and design, a rough average is

about 4,000 kilograms. Warehouses in developed countries have historically used

CFC-12 and R-502 refrigerants and currently use HCFC-22, R-404A, and R-507 A.

The latter two refrigerants are expected to replace HCFC-22 in new warehouses.

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Retrofits are also possible; for example, existing CFC-12 cold storage warehouses can

be retrofitted with R-401A, and existing R-502 warehouses can be retrofitted with

R-402A. Not all cold storage warehouses use halocarbon refrigerants. Many facilities,

for example, use ammonia in secondary loop brine systems.

2.2.6 Refrigerated Transport

The refrigerated transport end-use includes refrigerated ship holds, truck trailers,

railway freight cars, refrigerated rigid vans/trucks and other shipping containers.

Although charge sizes vary greatly, the average charge sizes are relatively small

(7 to 8 kilograms). The expected lifetime of a refrigerated transport system is 12

years. Trailers, railway cars, and shipping containers using CFC-substitute

refrigerants are commonly charged with HFC-134a, R-404A, and HCFC-22. Ship

holds, on the other hand, rely on HCFC-22 and ammonia. In addition to HFC-134a,

R-404A can be used in new equipment. Existing equipment can be retrofitted with

R-401A, R-402A, R-404A, R-507 A, and other refrigerants. In addition, refrigerated

transport equipment includes systems that operate based on the evaporation and

expansion of liquid CO2 or nitrogen.

2.2.7 Industrial Process Refrigeration

Industrial process refrigeration includes complex, often custom-designed refrigeration

systems used in the chemical, petrochemical, food processing, pharmaceutical, oil and

gas, metallurgical industries; in sports and leisure facilities; and in many other

applications. Charge sizes typically range from 650 to 9000 kilograms, and the

average lifetime is approximately 25 years. Ammonia, HCs, HCFC-123, and

HFC-134a are expected to be the most widely used substitute refrigerants for new

equipment in the near future. Upon completion of the HCFC phase-out, HFC-134a,

R-404A, and R-507 A are expected to be the primary refrigerants used in this end-use.

2.2.8 Residential and Small Commercial Air-Conditioning and Heat

Pumps

Residential and small commercial air-conditioning (e.g., window units, unitary air

conditioners, and packaged terminal air conditioners) and heat pumps are another

source of HFC emissions. Most of these units are window and through-the-wall units,

ducted central air conditioners, and non-ducted split systems. The charge sizes of the

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equipment in this sector range from 0.5 to 10 kilograms for residential systems, and

about 10 to 180 kilograms for commercial systems based on cooling capacity

requirements. The average lifetime of this type of equipment is 15 years. Residential

and commercial air-conditioning has been relying almost exclusively on HCFC-22

refrigerant. R-410A, R-407C and HFC-134a are currently used to replace HCFC-22 in

some new equipment for most end-uses, and this trend is expected to continue as

HCFC-22 is phased out. In particular, R-410A is expected to dominate the U.S.

residential market in the future, whereas R-407C is expected to replace HCFC-22 in

retrofit applications and some new residential and commercial equipment. Other

countries may experience different patterns of R-410A and R-407C use.

2.3 New refrigerant products

The announcement of the European Commission that refrigerants with a GWP > 150

are to be prohibited from MAC systems has generated the development of a number

of substances not previously considered, in those countries. The current standard

refrigerant for automotive air conditioning is R134a and its high GWP means that it is

subject to this restriction. Automotive applications account for approximately half of

the global HFC sales (UNEP, 2002) and therefore a significant proportion of the HFC

refrigerant business is threatened. Consequently, a number of new synthetic

refrigerants are under development as replacements for R134a, and possible fluids

include hydrofluoroethers (HFEs, low GWP and low pressure), fluoroiodocarbons

(FICs, low GWP and generally toxic) and a group of unsaturated HFCs or

fluoroalkenes (HFOs, low GWP), although little else is known about their other

properties. There are specific fluids and mixtures (including with HFCs) that are

currently under consideration and these include:

• R152a (HFC) and R1311 (FIC)

• R32 (HFC) and R1311 (FIC)

• R1234yf (HFO) and R1311 (FIC)

• R1234ze (HFO) and R1311 (FIC)

• R1234yf (HFO) and R1225yez (HFO)

• R1243zf (HFO) and R1311 (FIC)

Manufacturer's claims vary and to date detailed technical information is scarce, but in

general they are indicated to have GWP < 150 but potential volatile organic

compounds (VOCs), non-flammable, pressure-temperature characteristics and

performance close to existing refrigerants, and can use with conventional lubricants.

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2.4 Legislative requirements

The possible choice of refrigerant for new systems varies globally as a result of

national and regional legislation, but is largely dictated by the requirements of the

Montreal Protocol and subsequent amendments. In general, CFCs have already been

prohibited in developed countries and phase-out of HCFCs is occurring at present.

However, a large number of countries have made national legislation that accelerates

these phase-out schedules. Similarly, national and regional legislation for climate

change mitigation originating from the Kyoto Protocol will also impact on refrigerant

choice.

For example, in Denmark, Norway, Austria and Switzerland the use of high-GWP

refrigerants is being prohibited in a number of different applications and/or a GWP

tax is applied to the purchase of such refrigerants. The UK Government has not

produced any specific legislation, although in their Climate Change Programme they

provide a general policy on HFCs. This states that "HFCs should only be used where

other safe, technically feasible, cost effective and more environmentally acceptable

alternatives do not exist", and that "HFCs are not sustainable in the long term [47].

New European legislation (which was agreed in January 2006) has imposed some

controls on the use of HFCs (the "F-gas" regulation and directive). The main

provisions in the regulation cover:

• containment through responsible handling during use

• recycling and end-of-life recovery

• training and certification for personnel involved in the containment and recovery of

f-gases

• reporting on quantities produced, supplied, used and emitted

• labelling of products and equipment

• certain application specific controls on use

• certain placing on the market prohibitions

The directive (Directive 2006/40/EC relating to emissions from air-conditioning

systems in motor vehicles) will place restrictions on the types of Mobile Air

Conditioning (MAC) systems fitted to vehicles before vehicles are approved for sale,

and specifically:

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• a two-step phase out of MACs that use f-gases with a GWP greater than 150:

1 January 2011 for new types of vehicle, and 1 January 2007 the sunset date for all

new vehicles

• maximum annual leakage limits within the interim period before the phase out

• controls on refilling and retrofitting for these systems

Both the Regulation and Directive will enter into force in 2006 with the main body of

the provisions in the set to apply from one or two years after that date.

2.5 Illegal refrigerants

Another class of alternative refrigerants has also appeared on the global market scene:

illegal refrigerants. Some products that have been introduced (OZ-12, HC-12a, R-176

and R-405a) do not meet the EPA criteria for environmental acceptability or safety.

Flammable refrigerants such as OZ-12 and HC-12a that contain large quantities of

hydrocarbons (propane, butane, isobutane, etc.) have been declared illegal for use in

MV AC applications, but are still turning up in vehicle systems anyway because of

their cheap price.

Flammable refrigerants pose a significant danger to the occupants inside a vehicle,

should a leak occur. A spark from a cigarette or a switch can ignite the leaking

refrigerant causing an explosion and turning the car into a bomb. It takes only a small

quantity of a flammable hydrocarbon refrigerant such as propane or butane to create

an explosive mixture inside a typical automobile passenger compartment. Frontal

collisions can also release the refrigerant if the condenser is damaged, which could

result in a severe under hood fire causing extensive damage to the vehicle. There is

also a risk to service technicians who might encounter leaks while servicing a vehicle

or operating recovery/recycling equipment. Merely topping off an NC system with a

flammable hydrocarbon can make the entire charge of refrigerant flammable if the

amount added exceeds a certain percentage: 10% in the case of an R-12 system and

only 5% with R-134a. That is only a small fraction of hydrocarbon depending on the

overall capacity of the system.

Flammable refrigerants are used in some stationary applications as well as truck

trailer refrigeration units because there is less risk of leakage or fire. Also, the amount

of refrigerant is typically much less.

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2.6 Contaminated refrigerants

The high price of a refrigerant has also lead to an increase in incidences of virgin

refrigerant being adulterated with other less expensive refrigerants. Some suppliers

say they now test every single tank of refrigerant to make sure it contains the proper

refrigerant and that the quality of the refrigerant meets specifications. The primary

threat of contamination is that of accidentally cross-contaminating refrigerants when

vehicles are serviced. Because the law requires all refrigerants to be recovered, there

is a potential risk of contaminating when recovery and recycling equipment is

connected to a vehicle. The problem is compounded by the proliferation of alternative

and illegal refrigerants.

The dangers of cross-contamination are the effects it can have on cooling performance

and component reliability. R-12 and R-134a are not compatible refrigerants because

R-134a will not mix with and circulate mineral-based compressor oil (which may lead

to compressor failure). Nor is R-134a compatible with the moisture-absorbing

desiccant called XH-5, which is used in many R-12 systems.

Intermixing refrigerants can also raise compressor head pressures dangerously.

Adding R-22 (which is used in many stationary A/C systems but is not designed for

use in mobile A/C applications) to an R-12 or R-134a system may raise head

pressures to the point where it causes the compressor to fail. Straight R-22 can cause

extremely high discharge pressure readings (up to 400 or 500 psi) when under hood

temperatures are high. R-22 is also not compatible with XH-5 and XH-7 desiccants

used in most mobile A/C systems.

R-134a also requires its own special type of oil: either a polyalkylene (P AG) oil or a

polyol ester (POE) oil. Some compressors require heavier or lighter viscosity oil for

proper lubrication. The aftermarket generally favors POE oil because POE is

compatible with both R-12 and R-134a and unlike PAG oil it will mix with mineral

oil. Mineral oil, as a rule, should still be used in older R-12 systems.

To protect recycling equipment against cross-contamination or bad refrigerant, service

facilities should use a refrigerant identifier to check every system before it is serviced.

Intermixing different refrigerants can cause cooling problems as well as shorten the

life of the A/C compressor.

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2.7 Alternative refrigerants - Indian scenario

The following gives the sector wise application of alternative refrigerants used in

India.

Sub-sector Application Alternative Technology Domestic Household HFC-134a, HFC-152a, Blends and mixtures, Refrigeration Refrigerators and

Freezers

Hydrocarbons (for refrigerants) and HCFC-22, HCFC-22 + 142b, HCFC-141 b, Hydrocarbons for foaming)

Commercial Refrigerated Cabinets HCFC-134a, HFC-152a, Blends and mixtures,

Refrigeration Hydrocarbons (for refrigerants) and HCFC-22, HCFC-22 +142b, Hydrocarbons (for foaming)

Water Coolers HCFC-22, HFC-134a

Ice-candy machines HCFC-22, HFC-134a (refrigerants) and HCFC-14b

(foaming) Walk-in coolers

Industrial Cold Storages HCFC-22, HFC-134a, Ammonia

Refrigeration Process Chillers HCFC-22, HFC-134a, Ammonia

Transport Perishable Transport HCFC-22, HFC-134a, Blends and mixtures Refrigeration

Air Conditioning Chillers, Automotive HCFC-123, HFC-134a,HCFC-22 air-conditioning

HFC-134a, Blends and mixtures

Table 2.2: Application of alternative refrigerants used in India [53]

2.8 Environmental legislations in India - Global Warming, Ozone

Depletion

The following are the major milestones in the past decades, regarding the global

warming and ozone depletion environmental legislations in India.

1. The Air Act 1981, 1987.

2. The Air rules 1982

3. The air rules 1983

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4. The environment (protection) Act, EPA 1986

5. The environment protection rules 1986

6. Environmental Impact Assessment 1994

7. The noise pollution (regulation and control) rules 2000

8. The ozone depleting substances (regulation) rules 2000, subsequent amendments.

2.9 Remarks

The current trend all over the world particularly in industry is "sustainability".

Sustainable development or sustainability is development that meets the needs of the

present without compromising the ability of future generations to meet their own

needs. Refrigeration & Air-Conditioning is no exception to it and it is in the mode of

sustainability in tune with time.

The Montreal Protocol which phases out CFCs and HCFCs initiated the significant

research efforts into refrigerants and refrigeration technology, and subsequent

environmental legislation arising from the Kyoto Protocol to reduce emissions of

GHGs has continued to drive that research. There is an adequate choice of both

synthetic and natural refrigerants available for all types of systems and applications.

HFCs are the most common fluids used in new systems, typically R134a, R404A,

R407C and more recently R410A, and their uptake is largely due to convenience

despite having a high GWP. Non-synthetic refrigerants - primarily ammonia (R717),

carbon dioxide (R744) and HCs (R600a, R290, R1270) - are increasing in use

because of their favourable environmental and performance characteristics. Compared

to CFCs and HCFCs, use of these alternative refrigerants poses greater technical

challenges, mainly including compatibility, efficiency and safety issues. The tendency

until recently had been to adopt new refrigerants that possess similar pressure­

temperature and operating characteristics as the ODSs they replace because of

convenience in using existing system and component designs. However, the

introduction of R600a, R410A and most significantly, CO2, new systems are being

designed in a fashion that departs from the conventional R12, R502 and R22

baselines. Many obstacles exist that have resulted in a slow uptake of certain

alternatives. These include actual technical barriers such as overcoming safety issues

of flammable and/or toxic refrigerants, design of components for high pressure

refrigerants and achieving certain efficiency baselines for refrigerants with poor

thermo physical properties. Another form of barrier arises from the perception of the

36

field-level industry where the consequence of certain characteristics (such as

temperature glide or high operating pressure) is interpreted out of context. Similarly,

market competition means that organisations with interests in a particular technology

use a number of tactics to promote their own alternatives. Finally, the mindset of the

industry as a whole is one that expects a return to a standardised set of a small number

of refrigerants for the majority of applications. However, it appears that the norm is

actually a disparate group of various refrigerants that will continue to evolve over the

next few decades at least.

Trad~ (II IIrm lIarne Marllfat:1Ufef iJJEl); li'omments

Table 2.3: Air-conditioning, Commercial and Residential sector [49]

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