Refrigerants play an extremely important role in many different fields. Especially in the field of thermal engineering, which provides thermal equipment for other fields. Refrigerant appears in most airconditioning equipment, refrigeration systems, and deepcooling equipment such as storage, freezing, making ice,… In those systems, the refrigerant acts as a “blood vessel of the system” together with the compressor is the “heart of the system” and make that system magically control the temperature. It is the key component that helps the system to perform heat transfer, which is the miracle that enables temperature control. As a thermal engineering learner, we need to thoroughly understand refrigerant. We need to know about the classification, how it mumbered, how it works in systems, we also need to know about it’s toxicity, flammablity and it’s consequences on the environment and our health. So that we can choose the refrigerant wisely, suitable for the system and balace between cost and health but minimize as much as possible the natural environment affected . So that is the reason why we choose this topic
Definition and Classification of Refrigerant
Definition
A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle In most cycles it undergoes phase transitions from a liquid to a gas and back again.
The refrigerant acts as a “blood vessel of the system” together with the compressor is the “heart of the system” It is the key component that helps the system to perform heat transfer, which is the miracle that enables temperature control.
Mumbering
The numbering of refrigerants is based on the original numbering system for fluorocarbons, which was developed in the 1930s by DuPont and adopted by the entire field in 1956.
Since then, it has also been accepted in the ANSI/ASHRAE system as part of Standard 34 (Number Designation and Safety Classification of Refrigerants).
The numbering system provides technicians and engineers with an easy way to identify the chemical composition of a refrigerant Each number in the system has its own meaning in the identification of the compounds that form the refrigerant.
The basic structure begins with the “chemical group” of the substance, followed by a dash (-) and a string of numbers and letters The dash is also commonly omitted. For example, HFC-134a consists of the group identifiers “HFC” and “134a”, indicating the chemical composition of the substance Simply the identifying letter
“R” is also often used instead of the chemical group, in which case HFC-134a becomes R-134a.
For example, HCFC-22 is in the “000 series” of refrigerants, meaning it is a methane-based compound R-134a is in the “100 series” of refrigerants, meaning it is an ethane-based compound R-290 is part of the 200 series of propane-based compounds, etc.
Classification
There are thousands of different refrigerants, every year manufacturers nonstop invent new refrigerants to improve the effectiveness.and so there are many ways to classify refrigerants In this report we only mention three common way to classify a refrigerant.
To facilitate the selection of refrigerants, they often classify them into these type:
2 According to Saturated pressure and temperature.
2 According to The flamability and toxicity.
Based on the chemical elements present in the refrigerant, they can be classified into many different types of refrigerants
The most common types of refrigerants in use nowadays:
Halocarbons (or freons) are generally synthetically produced Depending on whether they include chemical elements hydrogen (H), carbon (C), chlorine (Cl) and florine (F) they are named after as follows:
These are substances containing CARBON, FLORINE and CHLORINE chemicals
The CFC refrigerant is now totally banned from use or production within all countries covered by the Montreal Protocol CFCs are generally characterised by a big ODP ( ODP values range from 0 to 1: the closest the ODP value is to 1, the more harmful the refrigerant is for the ozone layer) value, because they contain chlorine, which is accused of heavily contributing to the Ozone Depletion phenomenon As a result, CFCs have been phased out of use nowadays.
These are substances containing HYDROGEN, CARBON, FLORINE and CHLORINE chemicals.
Because of high values of GWP (GWP values range from 0 to several thousands: the bigger the GWP value is, the more harmful the refrigerant is for the global warming effect) In general, HCFC gases are to be banned from virgin use from Jan
2010 The general phase out shall be complete by 2015 unless the dates are brought forward.
These are substances containing HYDROGEN, FLORINE and CARBON chemicals
The HFC gases are used extensively in every day RAC (Refrigeration and Air Conditioning) systems There is no current ban upon these gases but responsible use and equipment inspections is mandatory under the "F gas" (gas contain Florine) regulations
The HFC refrigerants have no ozone depletion potential, but do act as a green house gas Only the chlorine free (zero ozone depletion) HFCs are allowed for use nowadays
A zeotropic mixture, or non-azeotropic mixture, is a mixture with components that have different boiling points For example, nitrogen, methane, ethane, propane, and isobutane constitute a zeotropic mixture Individual substances within the mixture do not evaporate or condense at the same temperature as one substance In other words, the mixture has a temperature glide, as the phase change occurs in a temperature range of about 4 ÷ 7 ( ),℃ rather than at a constant temperature On temperature- composition graphs, this temperature glide can be seen as the temperature difference between the bubble point and dew point For zeotropic mixtures, the temperatures on the bubble (boiling) curve are between the individual component's boiling temperatures When a zeotropic mixture is boiled or condensed, the composition of the liquid and the vapor changes according to the mixtures's temperature-composition diagram.
Zeotropic mixtures have different characteristics in nucleate and convective boiling, as well as in the organic Rankine cycle Because zeotropic mixtures have different properties than pure fluids or azeotropic mixtures, zeotropic mixtures have many unique applications in industry, namely in distillation, refrigeration, and cleaning processes.
An azeotrope or a constant boiling point mixture is a mixture of two or more liquids whose proportions cannot be altered or changed by simple distillation This happens because when an azeotrope is boiled, the vapour has the same proportions of constituents as the unboiled mixture Because their composition is unchanged by distillation, azeotropes are also called constant boiling point mixtures.
Some azeotropic mixtures of pairs of compounds are known, and many azeotropes of three or more compounds are also known In such a case it is not possible to separate the components by fractional distillation There are two types of azeotropes: minimum boiling azeotrope and maximum boiling azeotrope.
Each azeotrope has a characteristic boiling point The boiling point of an azeotrope is either less than the boiling point temperatures of any of its constituents (a positive azeotrope), or greater than the boiling point of any of its constituents (a negative azeotrope).
Typical examples of azeotropic mixtures can be seen below:
Inorganic refrigerants consists of inorganic compounds (which does not contain carbon-hydrogen bond) used primarily as refrigerants such as R-718, 717, and 744. Majority of these refrigerants are non-toxic and are environment friendly, inexpensive and non-flammable The report “Global Inorganic Refrigerants Market” analyzes the inorganic refrigerants market by type with respect to three major types such as ammonia, carbon dioxide, and water.
Used primarily as refrigerants such as:
Depending on whether they include chemical elements hydrogen (H), carbon (C).Hydrocarbon Refrigerants are natural, nontoxic refrigerants that have no ozone depleting properties and absolutely minimal global warming potential The most efficient and environmentally safe refrigerants in the world are the five natural refrigerants which are Air, Water, Carbon Dioxide, Ammonia and Hydrocarbons.
All existing Fluorocarbon Refrigerants will be phased out in some shape or form over the coming years because of their ozone depleting properties or global warming potential
Hydrocarbon Refrigerants are 50% more efficient conductors of heat than Fluorocarbon Refrigerants and their operating pressures are about 20% lower than that of Fluorocarbon Refrigerants These lower operating discharge pressures reduce the work that the compressor has to do thus reducing wear and tear There is less pressure on pipe work, joints, hoses, fittings and the like reducing the likelihood of leaks This can and will extend the working life of your equipment All these advantages equate to an energy saving of between 17% and 54%.
Hydrofluoroolefins (HFOs) are unsaturated organic compounds composed of hydrogen, fluorine and carbon These organofluorine compound are of interest as refrigerants Unlike traditional hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), which are saturated, HFOs are olefins, otherwise known as alkenes.
HFO refrigerants are categorized as having zero ozone depletion potential (ODP) and low global warming potential (GWP) and so offer a more environmentally friendly alternative to CFCs, HCFCs, and HFCs Many refrigerants in the HFO class are inherently stable chemically and inert, non toxic, and non-flammable or mildly flammable Many HFOs have the proper freezing and boiling points to be useful for refrigeration at common temperatures They also show promise as blowing agents, i.e. in production of insulation foams, food industry, construction materials, and others. HFOs are being developed as "fourth generation" refrigerants with 0.1% of the GWP of HFCs.
3.2 According to the Flammability and Toxicity
In fact, there are many standards for flammability and toxicity Here we take The American Society of Heating, Refrigerating and Air-Conditioning Engineers (FSHARE) standards as the standards for flammability and toxicity.
The three main flammability classifications are:
Class 1: No flame propagation: doesn’t show flame propagation in air at a temperature of 60°C
Class 2: Lower flammability: flame propagation shown at 60°C and The lower flammability limit (LFL) > 0.1kg/m3 or heat of combustion < 19,000kJ/kg.
Class 3: Higher flammability: flame propagation shown at 60°C and The lower flammability limit (LFL) < 0.1kg/m3 or heat of combustion > 19,000kJ/kg.
Some refrigerants classified by Flammability:
Class 1: R-11to R-14, R-113 to R-115, R-134a, R-410a, R-449b, R-1234zd,… Class 2: R-30, R-40, R-142b, R-152a, R-611, R-717,…
There are two classes for toxicity: lower toxicity (Class A) and higher toxicity (Class B):
Properties of Refrigerant
Chemical properties
Toxicity is the important properties of refrigerants The refrigerants should be non poisonous to humans and food stuff The toxicity depends upon the concentration and exposure limits.
The lubricating oils must be soluble in Refrigerants If the oil is not miscible in the refrigerant used and it is heavier it will settle down in the evaporator and reduces the heat transfer Therefore oil separators are to be employed If the oil density is less than the refrigerant used and it if it is immiscible, the oil will float on the surface of the refrigerant Therefore overflow drain is to be provided to remove oil If the refrigerant velocity is not sufficient, then it cannot carry all oil back into the compressor It may accumulate in evaporator This phenomenon is called Oil logging.
Most of the refrigerants form acids or bases in the presence of water This will cause corrosion and deteriorates valves, Seals and Metallic parts Insulation of windings in hermatic compressors will also get damaged The free water apart from the dissolved water in refrigerant freezes below 0 Deg C and chokes the narrow orifice of expansion valve This may also cause bursting of the tubes.
The refrigerants should not react with the materials used in refrigeration cycle like evaporators, condenser tubes, compressors, control valves etc Ammonia reacts with Copper and Cuprous alloys and forms copper complexes CH3Cl reacts with Aluminium Most of the refrigerants form acids with water CCl2F2, CH4Cl can form HCL with water which dissolves the copper from condenser tubes and deposits them on compressor pistons and deteriorates the life of the machinery.
Physical properties
Refrigerants should have low freezing point than the normal operating conditions.
It should not freeze during application Water for example cannot be used below 0Deg C.
The lower the condenser pressure the power required for compression will be lower Higher condenser pressure will result in high operating costs Refrigerants with low boiling points will have high condenser pressure and high vapor density The condenser tubes have to be designed for higher pressures which also give raise to capital cost of the equipment.
If Boiling Point is Low, High Condenser Pressure – Reciprocating Compressor is used Eg: Ammonia, R-22, R-12 etc
If Boiling Point is High, Low Condenser Pressure – Centrifugal Compressor is used Eg: R-11, R-13 & R-114 etc
This is the most important property of refrigerant In a negative pressure evaporator Atmospheric air or Moisture will Leak into the system The moisture inside the system will starts freezing at low temperature zones and clogs and chokes the system.
Atmospheric air ingression into the system will occupy the heat transfer area and results in poor heat transfer rates Presence of air will reduce the partial pressure of refrigerant and the condensation temperature will rise It increasers the condenser pressures and thereby the power consumption for the compressor will also rise.
Atmospheric air ingression inside the system may sometime results in explosions if the flammability values of the refrigerants are in wide range.
Due to the above disadvantages, Positive evaporator pressure is preferred Leak outside the system results in refrigerant loss and it can be identified easily and refrigerant loss can be topped up Moderately high evaporator pressure boosts the compressor suction pressure thus reduces the power costs.
Critical pressure of the refrigerant should be higher than the condenser pressures. Otherwise the zone of condensation decreases and the heat rejection occurs.
Refrigerants with High vapor density/ Low specific volume will require a smaller compressors and velocity can be kept small and so the condenser tubes used will also be in smaller diameter.
In hermetically sealed compressors refrigerant vapor contacts with motor windings and may cause short circuits Therefore dielectric strength should be high to avoid short circuits.
2.7 High Latent Heat of Vaporization.
Higher latent heat of vaporization of the refrigerant will result in lower mass flow rates according to the Heat transfer equation If the mass flow is very small it is difficult to control the flow rates Therefore ammonia cannot be used for small refrigeration systems.
Higher heat transfer coefficient requires smaller area and lower pressure drop.This makes the equipments compact and reduced the operating cost.
commonly used and applications of refrigerants
Some commonly used refrigerant
Refrigerant R-12 or Freon 12 is said to be the most widely used of all the refrigerants being used for different applications The chemical name of refrigerant R12 is dichlorodifluoromethane and its chemical formula is CCl2F2 The molecular weight of R-12 is 120.9 and its boiling point is -21.6 degree F Since R12 has the molecules of chlorine and fluorine, it is called as chlorofluorocarbon (CFC).
R-12 is a highly versatile refrigerant that is used for wide range of refrigeration and air conditioning applications though in many air conditioning applications it is now replaced by R-22 refrigerant Refrigerant R-12 is used in domestic refrigerators and freezers, liquid chillers, dehumidifiers, ice makers, water coolers, water fountains and transport refrigeration The wide range of applications of the refrigerant are due to its safe properties.
Refrigerant R-12 is nontoxic, nonflammable, and non-explosive This makes it highly popular for the domestic as well as the commercial applications.
R-12 is highly stable chlorofluorocarbon and it does not disintegrate even under the extreme operating conditions However, if it is brought in contact with the flame of fire or the electrical heating element, it disintegrates into the toxic products Thus whenever there is leakage of R-12 refrigerant it is advised to put all the flames off and keep the doors open so that it can escape to the open atmosphere.
3 Suitable for wide range of operating conditions:
R12 has the boiling point of -21.6 degree F (-29.8 degree C) due to which it condenses at the moderate pressures at the atmospheric temperature This means the discharge pressure of the compressor should be only moderate so as to produce the condensation of the refrigerant in the condenser at the atmospheric temperature This helps in using the compressor of low compression ratio that has higher efficiency Due to this property of refrigerant R-12, it is used in wide range of applications like high- temperature, medium temperature and low-temperature applications It can be used will all types of compressors like reciprocating, centrifugal and rotary.
Refrigerant R-12 is miscible with the compressor oil under all the operating conditions There are two advantages of this property of R-12 Firstly, there is no problem of the oil return back to compressor Some particles of the oil from compressor tend to get carried away with the discharged refrigerant, because of the property of miscibility of R-12, these particles return back to the compressor easily. The second advantage of miscibility is that the refrigerant flowing through the condenser and the evaporator is free of the oil particles The oil particles within the refrigerant reduce the heat transfer from it, but such problem does not occur with R-12 refrigerant Due to this the heat transfer capacity of the condenser and evaporator is increased, which ultimately helps increase the efficiency of the refrigeration plant.
1 Low refrigerating effect per pound:
The refrigerating effect of R-12 per pound of its weight is low compared to the other refrigerants However, this is not the major disadvantage as it can be used constructively in some cases In the smaller systems, the greater weight of the R-12 helps controlling the refrigeration system in a better way In the larger systems this disadvantage is offset by the higher vapor density of the refrigerant thus the compressor displacement required per ton of refrigeration with the R-12 refrigerant is not much higher than compared with the other refrigerants The high heat transfer rates in the condenser and the evaporator due to absence of the oil also helps reduce the effects of this disadvantage.
R-12 is the most widely used refrigerant, unfortunately it is the CFC and it has unusually high potential to cause the depletion of the ozone layer R-12 is being replaced by other refrigerants and some of the suggested replacements for R-12 are: R-134a, R-401a, R-401b.
( o C) (bar abs) (m 3 /kg) saturated liquid saturated vapor saturated liquid saturated vapor
(kJ/kg) (kJ/kg) (kJ/kgK) (kJ/kgK)
Table 1: Saturation table of R-12 refrigerant [A]
Figure 3, 4 : R-12 refrigerant and Old generation refrigerator uses R-12 refrigerant [3], [4]
Chlorodifluoromethane is a hydrochlorofluorocarbon (HCFC) This colorless gas is better known as HCFC-22, or R-22, or HClF 2
It is commonly used as a propellant and refrigerant These applications are being phased out in developed countries due to the compound's ozone depletion potential (ODP) and high global warming potential (GWP), although global use of R-22 continues to increase because of high demand in developing countries.
Temp. °C Press bar Enthalpy kJ/kg Entropy kJ/kg K
Figure 5, 6: R-22 Refrigerant and EuroKlimat Air Cooled Modular Chiller
Coming from the HFC (hydrofluorocarbons) family of refrigerants, R-134a is also known as tetrafluoroethane (CH2FCF3) consisting of two carbon atoms, 2 hydrogen atoms and 4 fluorine atoms
The properties of R134a refrigerant gas are discussed below:
R-134a is no-toxic, non-flammable and non-corrosive.
R-134a has a boiling point of -15.34 degree Fahrenheit or -26.3 degree Celsius that makes it exist in gas form when exposed to environment This is a desired property as the boiling point of a refrigerant should be below the target temperature.
R-134a has a high heat of vaporization.
Its auto-ignition temperature is 1418 degree Fahrenheit or 770 degree Celsius.
The critical temperature of R-134a is 252 degree Fahrenheit or 122 degree Celsius.
The universally accepted cylinder color code for R-134a refrigerant is light blue.
Its solubility in water is 0.11% by weight at 77degree Fahrenheit or 25 degree Celsius.
It has a moderate density in liquid form.
R-134a has zero Ozone layer depleting properties and hence became popular as an ideal replacement for dichlorodifluoromethane (R-12), which was known to have an adverse impact on the Ozone layer.
This refrigerant has a Global Warming Potential (GWP) of 1300 GWP is a relative measure of the amount of heat trapped in the atmosphere by a greenhouse gas.
The low molecular weight, volatility, lipophilicity and liquid state at room temperature makes the refrigerant as organic solvents in commercial industries.
R-134a has fairly good dielectric properties as it has high thermal stability, low boiling point, and chemical inertness against the construction materials used; and is non-toxic and non-flammable A dielectric substance in its gaseous state can be used to prevent electric discharges.
R-134a refrigerant gas is commonly used across multiple applications as listed below:
Used in the area of centrifugal, rotary screw, scroll and reciprocating compressors as a replacement for R-12 CFC
Used in air conditioning system in newer automotive vehicles
Used in plastic foam blowing in the manufacturing industry
Used as a propellant in the pharmaceuticals industry
Used in gas dusters and in air driers for the purpose of removing moisture from compressed air
Used in particle detectors such as cryogenic particle detectors
SpecificVolume m 3 /kg Enthalpy kJ/kg Entropy kJ/kg # K Liquid Sat. v f × 10 3
Table 3: Saturated properties of R-134a refrigerant [C]
Figure 7, 8, 9: R-134a, Air compressor on car and Sanaky Inverter VH-1009HP3.
R-404a is a safe alternative to R-22 The use of the refrigerant is in refrigeration systems that also require a temperature between -45° C and 15° C This translates to - 49° F and 59° F The wide temperature range makes it useful in industrial and commercial transport industries.
The properties of this refrigerant are similar to R-22 This also offers better performance.
R-404a does not react rapidly with air or water This makes it safe for many uses.
It is also colourless, non-inflammable and odourless.
Users should take adequate safety precautions when using refrigerant Direct contact with R-404a can cause frostbite Exposure to high heat or fire can rupture the refrigerant tank R-404a is available in stores that sell cooling as well as heating products.
Figure 10, 11: R-404a and Alaska Sl-24C4 refrigerator [10], [11]
Temp. °C Pressure kPa spec Enthalpy kJ/kg spec Entropy kJ/kg K liquid gas liquid gas liquid gas
Table 4: Saturated properties of R-404a refrigerant [D]
This refrigerant has thermodynamic properties It is a common replacement refrigerant to retrofit R-22 equipment The mix of hydrofluorocarbons includes a blend of difluoromethane, pentafluoroethane, and also 1,1,1,2-tetrafluoro-ethane. Ductless split systems, packaged air conditioners, and also water chillers use the refrigerant Apart from this, it is also present in direct expansion systems and light air conditioning found in commercial, residential, and industrial properties.
R-407c also works in refrigeration systems with medium temperature Many new appliances use R-407c New appliances that use nitrogen as a holding charge will work best with R-407c This is because it uses polyol ester oil.
R-407c is quite common in new refrigeration systems and appliances R-407c is also present on some R-22 systems The procedure involves an oil change when retrofitting R-407c is an alternative to freon It is safe for the environment.
Figure 12, 13: R-407c and Dunham Bush ACPSH Central Packaged Air
Temp. °C Pressure kPa spec.Enthalpy kJ/kg spec Entropy kJ/kg K liquid gas liquid gas liquid gas
Table 5: Saturated properties of R-407c refrigerant [E]
This refrigerant is a blend of difluoromethane, two hydrofluorocarbon refrigerants, as well as pentafluoroethane R-410a is a non-ozone depleting refrigerant It provides energy efficiency than R-407c and R-22 Chlorine is not even there.
The high refrigeration capacity and pressure make it more suitable than R-22 This helps in providing better performance.
Applications of Refrigerant
As introduced in Introduction, refrigerants play an extremely important role in many different fields Especially in the field of thermal engineering, which provides thermal equipment for other fields Refrigerant appears in most air-conditioning equipment, refrigeration systems, and deep-cooling equipment such as storage, freezing, making ice,… In those systems, the refrigerant acts as a “blood vessel of the system” together with the compressor is the “heart of the system” It is the key component that helps the system to perform heat transfer, which is the miracle that enables temperature control.
Residential refrigeration equipment usually has small to medium capacity such as air-conditioner, refrigerator, freezer, vehicle air-conditioner, etc …They often use refrigerant such as R-410A, R-32, R-290,… because of their because of the highlights that we specifically mentioned above.
Figure 25: Practical refrigerator and its principle of operation [25]
Figure 26, 27: Practical air-conditioning system and its principle of operation [26],
Figure 28, 29: Euhomy Commercial Ice Maker Machine and its principle of operation [28], [29]
Besides civil refrigeration equipment, industrial refrigeration covers a wide range of applications, from high temperature process chilling, through to very low temperature applications such as those used in medical freezers or LNG liquefaction.
Figure 30, 31, 32, 33: Cool storages and it’s principle of operation [30], [31],
In addition to the applications in thermal engineering, refrigerants are also applied in a number of other fields such as medical, biology, chemistry, physics,
In medical: The medical industry needs professional refrigeration equipment to preserve pharmaceuticals, blood, organs,
In the field of research: Special refrigeration systems are also needed for the preservation of seeds, chemicals and laboratory practices,
2.3 Calculate Circulation amount of refrigerant
Circulation amount of refrigerant : An amount of refrigerant to be evaporated in evaporator to obtain the refrigerating capacity needed It is expressed in the weight by the unit time.
G: Circulation amount of refrigerant (kg/h).
Q: Refrigerating capacity needed (Kcal/h). q e : Refrigerating effect by the refrigerant 1kg (Kcal/kg).
To decide the capacity of compressor, the circulation amount of refrigerant should be converted into the suction gas amount of compressor
V ' : Suction gas amount of compressor (m3/h).
V A : Specific volume of refrigerant at compressor inlet (m3/kg)
The amount of piston extrusion is calculated as follows.
D: Diameter of cylinder (m). n: Rotational speed of compressor (rpm).
GLOBAL ISSUES CAUSED BY REFRIGERANTS AND
As with all human activities, refrigeration and air conditioning applications have an impact upon the environment, contributing to ozone depletion and global warming. There are two main areas of environmental impact:
Direct: The leakage of refrigerant gases into the atmosphere which can cause ozone depletion and contribute to global warming.
Indirect: Refrigeration and air conditioning systems consume energy, which raises CO2 emissions and contributes to global warming.
Use a refrigerant gas with lower environmental impact: Look to use a refrigerant gas with zero ozone depletion potential (ODP) and low global warming potential (GWP) Linde has produced a summary list of refrigerant gases and their environmental impact.
Lower the leak rates of your system: Refrigerants only create direct emissions when they leak to atmosphere Therefore Linde recommend that you ensure that your system is leak-tight, consider fitting leak-detection systems and follow a regular maintenance schedule.
Ensure correct end-of-life treatment of refrigerant gases: Ensure that you recover and dispose of refrigerant gas correctly when maintaining, upgrading or decommissioning a system.
Minimise the power consumption of your refrigeration or air conditioning system: For existing systems, ensure that you are regularly maintaining the system and using the correct refrigerant gas Installing new systems may offer substantial energy savings, via modern technology using next generation refrigerants, including HFOs and natural refrigerants.
Use your refrigeration or air conditioning system less often: Improve insulation, install doors on commercial refrigerators, freezers and display cases, and change the temperature set-points for air conditioning.
Hydro fluorocarbons, such as R-134a, have almost zero ozone depletion potential, since they do not contain chlorine atoms in their chemical structure.They are safe, non inflammable and have vapour pressures similar to that of R-12.Hydrocarbon Refrigerants are natural, nontoxic refrigerants that have no ozone depleting properties and absolutely minimal global warming potential The most efficient and environmentally safe refrigerants in the world are the five natural refrigerants which are Air, Water, Carbon Dioxide, Ammonia and Hydrocarbons.