Eco-friendly Refrigerants

Dr Alka Bani Agrawal Professor,Mechanical Engg UIT,RGPV

History Of Refrigeration
Refrigeration relates to the cooling of air or liquids, thus providing lower temperature to preserve food, cool beverages, make ice and for many other . Most evidence indicate that the Chinese were the first to store natural ice and snow to cool wine and other delicacies. Ancient people of India and Egypt cooled liquids in porous earthen jars. In 1834, Jacob Perkins, an American, developed a closed refrigeration system using liquid expansion and then compression to produce cooling. He used Ether as refrigerant, in a hand- operated compressor, a water-cooled condenser and an evaporator in liquid cooler.

Refrigerantion Principle
Modern refrigeration and air-conditioning equipment is dominated by vapour compression refrigeration technology built upon the thermodynamic principles of the reverse Carnot cycle. Refrigerant Changes phases during cooling and used again and again.

What is a Refrigerant
Refrigerants are used as working substances in a Refrigeration systems. Fluids suitable for refrigeration purposes can be classified into primary and secondary refrigerants. Primary refrigerants are those fluids, which are used directly as working fluids, for example in vapour compression and vapour absorption refrigeration systems. These fluids provide refrigeration by undergoing a phase change process in the evaporator. Secondary refrigerants are those liquids, which are used for transporting thermal energy from one location to other. Secondary refrigerants are also known under the name brines or antifreezes

What is ChloroFloroCarcons
Todays refrigerants are predominantly from a group of compounds called halocarbons (halogenated hydrocarbons) or specifically fluorocarbons. Chlorofluorocarbons were first developed by General Motors researchers in the 1920s and commercialized by Dupont as Freons.

Halocarbon Refrigerants
Halocarbon Refrigerant are all synthetically produced and were developed as the Freon family of refrigerants.
Examples :
CFCs : R11, R12, R113, R114, R115

Freon Group Refrigerants Application and ODP Values

Refrigerant CFC 11(R11) Areas of Application ODP Air-conditioning Systems ranging from 200 to 1.0 2000 tons in capacity. It is used where low freezing point and non-corrosive properties are CFC 12 ( R 12 important. ) It is used for most of the applications. Air- 1.0 conditioning plants, refrigerators, freezers, icecream cabinets, water coolers, window airconditioners, automobile air conditioners. CFC 13 (R 13) For low temp refrigeration up to 90 C in 1.0 cascade system CFC113 ( R113 Small to medium air-conditioning system and 1.07 ) industrial cooling 0.8 CFC114 ( R114 In household refrigerators and in large industrial 0.34 ) cooling Blend of R22 Frozen food ice-cream display cases and and R115 warehouses and food freezing plants. An (R502) excellent general low temp refrigerant

What is Ozone Layer

Ozone is an isotope of oxygen with three atoms instead of normal two. It is naturally occurring gas which is created by high energy radiation from the Sun. The greatest concentration of ozone are found from 12 km to 50 km above the earth forming a layer in the stratosphere which is called the ozone layer. This layer, which forms a semi-permeable blanket, protects the earth by reducing the intensity of harmful ultra-violet (UV) radiation from the sun.

Ozone Layer Depletion

In the early70s,scientists Sherwood Roland and Mario Molina at the University of California at Irvine were the first to discover the loss of ozone in stratosphere while investigating the ozone layer from highflying aircraft and spacecraft. They postulated the theory that exceptionally stable chlorine containing fluorocarbons could, overtime, migrate to the upper reaches of the atmosphere and be broken by the intense radiation and release chlorine atoms responsible for

OZONE LAYER DEPLETION

N0RMAL REACTION O2 = O + O O 2 + O = O3 But CFC refrigerants leaked during the manufacturing and normal operation or at the time of servicing or repair, mix with surrounding air and rise to troposphere and then into stratosphere due to normal wind or storm. The Ultraviolet rays act on CFC releasing Cl atom, which retards the normal reaction: RETARDED REACTION O3 = O2 + O CCL2F2 = CCLF2 + CL O3 + CL = CLO + O2 O + CLO = CL + O2

Harmful consequences of ozone depletion

For Humans skin cancer

Increase in

snow blindness cataracts Less immunity to infectious diseases malaria herpes

For plants

smaller size lower yield increased toxicity altered form

For marine life Reduced

plankton juvenile fish larval crabs and shrimps

MONTREAL PROTOCOL
SIGNED IN 1987 UNDER THE UNEP, AFTER MUCH DISCUSSIONS MORE THAN 170 COUNTRIES HAVE RATIFIED

INDIA RATIFIED ON SEPT 17,1992

ONE OF MOST SUCCESSFUL EXAMPLE OF INTERNATIONAL COOPERATION IN UN HISTORY

Montral Protocol- Control Schedule

ozone depleting substance CFCs developed countries developing countries

Montreal protocol- Control Schedule

phased out end of 1995

phased out end of 1993 total phase out by 2020

total phase out by 2010

total phase out by 2010 total phase out by 2040

halons

HCFCs

CFC Phase-out in India

What is to be phased out? CFC-11, CFC-12 & CFC-113a. How much and when? 1999 22,588 MT 2005 11,294 MT 2010 o MT How to achieve the target? Production is controlled through a production quota allocated to each producer every year. The Ozone Cell conducts audits twice a year to monitor the production. How much has been Phaseout? CFC has been completely phased out as on 1st August, 2008 Year

Vapor compression refrigeration System

In 1834 an American inventor named Jacob Perkins obtained the first patent for a vapor-compression refrigeration system, it used ether in a vapor compression cycle. Joule-Thomson (Kelvin) expansion Low pressure (1.5 atm) low temperature (10 to +15 ) inside High pressure (7.5 atm) high temperature (+15 to +40 ) outside

Components
Refrigerant Evaporator/Chiller Compressor Condenser Receiver Thermostatic expansion valve (TXV)

Circulation of Refrigerant

Compressor cold vapor from the evaporator is compressed, raising it temperature and boiling point adiabatic compression T, b.p. ~ P work done on the gas Condenser hot vapor from the compressor condenses outside the cold box, releasing latent heat isothermal, isobaric condensation (horizontal line on PV diagram) high temperature T (hot) latent heat of vaporization Q (hot) Expansion valve (throttling valve) hot liquid from the condenser is depressurized, lowering its temperature and boiling point adiabatic, isochoric expansion (vertical line on PV diagram) T, b.p. ~ P no work done W = 0 Evaporator cold liquid from the expansion valve boils inside the cold box, absorbing latent heat isothermal, isobaric boiling (horizontal line on PV diagram) low temperature T (cold) latent heat of vaporization Q (cold)

Importance of Refrigerant
The thermodynamic efficiency of a refrigeration system depends mainly on its operating temperatures. However, important practical issues such as the system design, size, initial and operating costs, safety, reliability, and serviceability etc. depend very much on the type of refrigerant selected for a given application. Due to several environmental issues such as ozone layer depletion and global warming and their relation to the various refrigerants used, the selection of suitable refrigerant has become one of the most important issues in recent times.

Refrigerant selection criteria

Selection of refrigerant for a particular application is based on the following requirements:
i. Thermodynamic and thermo-physical properties ii. Environmental and safety properties Iii. Economics

Thermodynamic and thermo-physical properties

The requirements are: a) Suction pressure: At a given evaporator temperature, the saturation pressure should be above atmospheric for prevention of air or moisture ingress into the system and ease of leak detection. Higher suction pressure is better as it leads to smaller compressor displacement b) Discharge pressure: At a given condenser temperature, the discharge pressure should be as small as possible to allow lightweight construction of compressor, condenser etc. c) Pressure ratio: Should be as small as possible for high volumetric efficiency and low power consumption d) Latent heat of vaporization: Should be as large as possible so that the required mass flow rate per unit cooling capacity will be small

Thermodynamic and thermo-physical properties

In addition to the above properties; the following properties are also important: e) Isentropic index of compression: Should be as small as possible so that the temperature rise during compression will be small f) Liquid specific heat: Should be small so that degree of subcooling will be large leading to smaller amount of flash gas at evaporator inlet g) Vapour specific heat: Should be large so that the degree of superheating will be small h) Thermal conductivity: Thermal conductivity in both liquid as well as vapour phase should be high for higher heat transfer coefficients i) Viscosity: Viscosity should be small in both liquid and vapour phases for smaller frictional pressure drops The thermodynamic properties are interrelated and mainly depend on normal boiling point, critical temperature, molecular weight and structure.

Environmental and safety properties

At present the environment friendliness of the refrigerant is a major factor in deciding the usefulness of a particular refrigerant. The important environmental and safety properties are: a) Ozone Depletion Potential (ODP): According to the Montreal protocol, the ODP of refrigerants should be zero, i.e., they should be non-ozone depleting substances. Refrigerants having nonzero ODP have either already been phased-out (e.g. R 11, R 12) or will be phased-out in nearfuture(e.g. R22). Since ODP depends mainly on the presence of chlorine or bromine in the molecules, refrigerants having either chlorine (i.e., CFCs and HCFCs) or bromine cannot be used under the new regulations

Environmental Effects of Refrigerants

Global warming :

Refrigerants directly contributing to global warming when released to the atmosphere Indirect contribution based on the energy consumption of among others the compressors ( CO2 produced by power stations )

Environmental and safety properties

b) Global Warming Potential (GWP): Refrigerants should have as low a GWP value as possible to minimize the problem of global warming. Refrigerants with zero ODP but a high value of GWP (e.g. R134a) are likely to be regulated in future. c) Total Equivalent Warming Index (TEWI): The factor TEWI considers both direct (due to release into atmosphere) and indirect (through energy consumption) contributions of refrigerants to global warming. Naturally, refrigerants with as a low a value of TEWI are preferable from global warming point of view.

Environmental and safety properties

d) Toxicity: Ideally, refrigerants used in a refrigeration system should be non-toxic. Toxicity is a relative term, which becomes meaningful only when the degree of concentration and time of exposure required to produce harmful effects are specified. Some fluids are toxic even in small concentrations. Some fluids are mildly toxic, i.e., they are dangerous only when the concentration is large and duration of exposure is long. In general the degree of hazard depends on:
- Amount of refrigerant used vs total space - Type of occupancy

- Presence of open flames

- Odor of refrigerant, and - Maintenance condition

Environmental and safety properties

e) Flammability: The refrigerants should preferably be non-flammable and non-explosive. For flammable refrigerants special precautions should be taken to avoid accidents. f) Chemical stability: The refrigerants should be chemically stable as long as they are inside the refrigeration system. g) Compatibility with common materials of construction (both metals and non-metals) h) Miscibility with lubricating oils: Oil separators have to be used if the refrigerant is not miscible with lubricating oil (e.g. ammonia). Refrigerants that are completely miscible with oils are easier to handle(R12).

Environmental and safety properties

Ease of leak detection: In the event of leakage of refrigerant from the system, it should be easy to detect the leaks. Economic properties: The refrigerant used should preferably be inexpensive and easily available.

ECO-FRIENDLY REFRIGERANTS

CFC ALTERNATIVES.
HCFC R22,R124 HFC R134a,R152a NATURAL REFRIGERANT NH3, HC'S

Halocarbon Refrigerants
Halocarbon Refrigerant are all synthetically produced and were developed as the Freon family of refrigerants.
Examples :
CFCs : R11, R12, R113, R114, R115 HCFCs : R22, R123 HFCs : R134a, R404a, R407C, R410a

HFCs
Remain a popular choice
especially for R22 phase out

Good efforts at improving leakage performance

e.g. Real Zero project

Interest in R407A to replace R404A

50% reduction in GWP

F Gas Stakeholder Group, 14th October 2009

Slide 30

Inorganic Refrigerants
Carbon Dioxide Water Ammonia Air Sulphur dioxide

HCFC
Transitional compounds with low ODP Partially halogenated compounds of hydrocarbon Remaining hydrogen atom allows Hydrolysis and can be absorbed. R22, R123

HCFC
Production frozen at 1996 level 35% cut by 2005,65% by 2010 90% by 2015,100 % by 2030 10 year grace period for developing countries.

R22
ODP-0.05, GWP-1700 R22 has 40% more refrigerating capacity Higher pressure and discharge temp and not suitable for low temp application Extensively used in commercial airconditioning and frozen food storage and display cases

R123
ODP-0.02,GWP-90 As a replacement for R11 as similar thermodynamic properties. Very short atmospheric life but classified as carcinogen Retrofit alternative to R11

HFC
Zero ODP as no chlorine atom contains only Hydrogen and Flurodine Very small GWP values No phase out date in Montreal Protocol R134a and R152 a Very popular refrigerants HFC refrigerants are costly refrigerants

R134a
ODP-0, GWP-1300 Used as a substitute for R12 and to a limited range for R22 Good performance in medium and high temp application Toxicity is very low Not miscible with mineral oil

R152a
ODP-0,GWP-140 R152a is another attractive HFC with similar properties to R12. GWP is one order less than HFC134a but it is slightly flammable. Also it has lower energy consumption. Hence the Environmental Protection Agency of Europe prefers HFC152a to HFC134a

Hydrocarbon
Very promising non-halogenated organic compounds With no ODP and very small GWP values Their efficiency is slightly better than other leading alternative refrigerants They are fully compatible with lubricating oils conventionally used with CFC12.

Hydrocarbon Refrigerants
Extraordinary reliability- The most convincing argument is the reliability of the hydrocarbon system because of fewer compressor failures. But most of the hydrocarbons are highly flammable and require additional safety precaution during its use as refrigerants. Virtually no refrigerant losses Hydrocarbons have been used since the beginning of the century and now being considered as long term solutions to environmental problems,

Hydrocarbons
Dominant in domestic market like household refrigerators and freezers Growing use in very small commercial systems like car air-conditioning system Examples:
R170, Ethane, C2H6

R290 , Propane C3H3 R600, Butane, C4H10 R600a, Isobutane, C4H10 Blends of the above Gases
Slide 42

F Gas Stakeholder Group, 14th October 2009

R290
ODP-0,GWP-3 Compatible with copper.Miscible with mineral oil Highest latent heat and largest vapour density A third of original charge only is required when replacing halocarbons refrigerant in existing equipment Energy saving : up to 20% due to lower molecular mass and vapour pressure

R 600a
ODP-0,GWP-3 Higher boiling point hence lower evaporator pressure Discharge temp is lowest Very good compatibility with mineral oil

Flammability
Approximate auto ignition temperatures R22 630 C R12 750 C R134a 740 C R290 465 C R600a 470 C

Modifications of Electrical Equipment

Replaced with solid state equivalents Sealed to ensure that any sparks do not come into contact with leaking gas Relocated to a position where the component would not come into contact with leaking gas

Modifications of Electrical Equipment

Faulty components. Poor, corroded, loose, or dirty electrical connections. Missing or broken insulation which could cause arcing/sparks. Friction sparks, like a metal fan blade hitting a metal enclosure.

Blends & Mixtures

Limited no of pure refrigerants with low ODP & GWP values To try a mixture of pure refrigerants to meet specific requirement

Azeotropic Refrigerants
A stable mixture of two or several refrigerants whose vapour and liquid phases retain identical compositions over a wide range of temperatures.
Examples : R-500 :
R152
73.8% R12 and 26.2%

R-502 : 8.8% R22 and 51.2% R115 R-503 : 40.1% R23 and 59.9% R13

Zeotropic Refrigerants
A zeotropic mixture is one whose composition in liquid phase differs to that in vapour phase. Zeotropic refrigerants therefore do not boil at constant temperatures unlike azeotropic refrigerants. Examples :R404a : R125/143a/134a

(44%,52%,4%) R407c : R32/125/134a (23%, 25%, 52%) R410a : R32/125 (50%, 50%) R413a : R600a/218/134a (3%, 9%, 88%)

Inorganic Refrigerants
Carbon Dioxide Water Ammonia Air Sulphur dioxide

Carbon Dioxide
Zero ODP & GWP Non Flammable, Non toxic Inexpensive and widely available Its high operating pressure provides potential for system size and weight reducing potential.

Drawbacks: Operating pressure (high side) : 80 bars Low efficiency

Ammonia A Natural Refrigerant

Ammonia is produced in a natural way by human beings and animals; 17 grams/day for humans.
Natural production Production in factories Used in refrigeration 3000 million tons/year 120 million tons/year 6 million tons/year

Ammonia as Refrigerant
ODP = 0 GWP = 0 Excellent thermodynamic characteristics: small molecular mass, large latent heat, large vapour density and excellent heat transfer characteristics High critical temperature (132C) : highly efficient cycles at high condensing temperatures Its smell causes leaks to be detected and fixed before reaching dangerous concentration Relatively Low price

Some Drawbacks of Ammonia as Refrigerant

Toxic Flammable ( 16 28% concentration ) Not compatible with copper Temperature on discharge side of compressor is higher compared to other refrigerants

Water
Zero ODP & GWP Water as refrigerant is used in absorption system .New developing technology has created space for it for use in compression cycles also. But higher than normal working pressure in the system can be a factor in restricted use of water as refrigerant

Application of New Eco-friendly Refrigerants

Application Eco-friendly refrigerant Domestic refrigeration Commercial refrigeration Cold storage ,food processing And industrial refrigeration Unitary air conditioners Centralized AC (chillers) Transport refrigeration Mobile air conditioner Heat pumps HFCs used Possible R134a,R152a R134a,R404A,R407C R134a,R404A,R507A R410A,R407C R134a,R410A,R407C R134a,R404A R134a R134a,R152a,R404A R407C,R410A HC600a and blends HC blends,NH3 ,CO2 ** NH3 ,HCs,CO2 ** CO2 , HC s NH3 ,HCs,CO2, water ** CO 2, CO2 ,HCs NH3 ,HCs,CO2, water **

Table 3 -Performance Results of R12 and New Proposed Refrigerants using the same compressor as with R12 in Milk Chilling Unit

Refrigerants Mass flow rate kg / min Refrigerating capacity kW Compressor power kW COP Volumetric Refrigeration Capacity(kj/ m3) Discharge Temp C R 32 R 290 R 22 R 12 R 134a R 152a R 124 R 600a R 142b R 600

8.81 4.45 7.45 6.99

General Safety measures for refrigerating plants

Reduction of refrigerant contents: Components with reduced contents Indirect systems with secondary refrigerant: distinction between generation and transport of cold

Scheduled maintenance and leak testing

Governmental surveillance Refrigerant Audits for systems operating with HFCs. Recovery, Stock of used refrigerants, Recycling of refrigerants. For the Netherlands, the combined measures resulted in a leak rate reduction of 35% (1995) to 8% (2001) for R22systems

Survey Of Refrigerants
Refrigerant R11 R12 R22 R134a R404a R410a R507 R717 R744 R290 R600a Group CFC CFC HCFC HFC HFC HFC HFC NH3 CO2 HC HC Atmospheri c life 130 130 15 16 16 16 130 <1 <1 ODP 1 1 .05 0 0 0 1 0 0 0 0 GWP 4000 8500 1500 1300 3260 1720 3300 0 1 8 8

Conclusions
In the aftermath of the Montreal protocole HFCs have predominantly replaced CFCs and HCFCs in RAC equipment. Due to their high GWP, HFCs are not a good replacement solution. The solution are the natural refrigerants : Ammonia, Hydrocarbons and Carbon dioxide System need to have low TEWI factor High efficiency with ammonia and lower power consumption with hydrocarbons

Thank You

Environmental Effects of Refrigerants

Global warming :

Refrigerants directly contributing to global warming when released to the atmosphere Indirect contribution based on the energy consumption of among others the compressors ( CO2 produced by power stations )