Freon gases and their comparison in refrigeration systems

Introduction

Freon refrigerant is a substance that is gaseous at normal room temperature, but when cooled and compressed, it changes state and becomes a liquid. Freon gas has the characteristics of non-flammable, colorless and odorless. One of the salient features of this gas is that it does not corrode metals even when combined with moisture; The smell of freon gas is similar to the smell of ether. Freon is actually a brand name for a group of chemicals (known as chlorofluorocarbons or CFCs) so it is used as a refrigerant or air conditioner in the air conditioning system.

Freon refrigerant is a working fluid used in the refrigeration cycle of air conditioners and heat pumps. Early air conditioners and refrigerators traditionally used fluorocarbons, especially chlorofluorocarbons (CFCs) such as ammonia, sulfur dioxide, methyl chloride, or propane, as refrigerants, which were toxic or flammable gases that They are obsolete due to their toxicity, flammability and contribution to ozone depletion and climate change.

In this article, we intend to discuss Freon gas, its types, applications of Freon gas, effects of Freon gas and its application in refrigeration system.

History of Freon Refrigerant

In 1928, Thomas Jr. created the first non-flammable, non-toxic chlorofluorocarbon gas, the Freon R-12. Following the discovery of better synthesis methods, CFCs such as R-11-R-12-R-123 and R-502 dominated the market.

In the early 1980s, scientists discovered that CFCs damage the ozone layer, which protects the earth from ultraviolet light and ozone holes in the Arctic. This led to the signing of the Montreal Protocol in 1989, which aimed to phase out CFCs and HCFCs. Using HCFCs such as R-22 and R-123 have ozone depleting potential (ODP).

In the 1990s and 2000s, hydrofluorocarbons (HFCs) such as R-134a, R-143a, R-407a, R-407c, R-404a, and R-410a replaced CFCs and HCFCs. HFCs do not degrade ozone but have heating potentials. Global GWP is thousands of times more than atmospheric CO2, which can last for decades.

Use of Hydrocarbon and HFO (hydrofluoroolefin) R-32, R-290, R-600a, R-454b, R-1234yf, R-514A, R-744 (CO2), R-1234ze R-1233zd refrigerants since 2010. It started with both zero ODP and lower GWP. Hydrocarbons and CO2 are sometimes called natural refrigerants because they are found in nature.

Types of Freon gas and their application

Freon refrigerant gas is divided into the following types in terms of composition and application:

Refrigerant R22

R-22 gas has characteristics such as stability, non-toxicity, without oxidizing effect and non-flammable.

Freon R-22 refrigerant is one of the most well-known HCFC (hydrochlorofluorocarbon) Freon gas. After the ban on the use of CFCs, it has found great application in the field of air conditioning and refrigeration, which have a low degree of evaporation. As in the past, due to its high compressibility and greater refrigeration properties, this gas has been used in the construction of almost all air conditioning systems and refrigeration equipment, including gas coolers, compression and air conditioning chillers, duct splits, home refrigerators, etc. Is .

R-22 gas is used in rapid freezing devices to maintain their temperature between 20 and 40 degrees Fahrenheit. R-22 is used only in reciprocating compressors and its operating pressure is such that to achieve low temperatures, No need to work at pressures lower than atmospheric. Its latent heat per pound is 5 degrees Fahrenheit 93/21 BTU. The normal pressure of the compressor head at 86 degrees is 172/82 pounds per square inch.

Also, due to the R-22’s greater desire for water, more dehumidifiers are needed to dry it. R-22 dissolves in oil at a temperature of 16 degrees Fahrenheit, after which the oil begins to separate and because it is lighter than liquid, it accumulates on its surface.

But in addition to the unique properties of R22 gas, we must also mention the negative effects of this gas. The production and use of this Freon refrigerant has been banned since 2010 due to environmental reasons such as ozone depletion and global warming, and has been replaced by R410A refrigerant gas. However, the use of R22 gas in refrigeration equipment is allowed until its storage is not completed.

RefrigerantR134a

Refrigerant gas R134a, which replaces Freon 12 and 11, is heavier than air, has the chemical formula CH2FCF3, has a molecular weight of 103.03 and has good thermodynamic properties. This gas is non-toxic and has a purity of 99.95. Contains synthetic oil (polyester) and does not mix with natural oils. It has no chloride atoms and has no negative effect on the ozone layer. Compared to R-12, it has better thermal conductivity, more latent heat and higher heat transfer. R134 gas is more absorbent than R12 and R134 compressors should never be used to test ambient air that is on for more than 30 seconds, as it compresses the oil absorption air and disrupts the refrigeration cycle. This is an acceptable environmental gas that can be used well in the construction of home refrigerators and car air conditioners.

Refrigerant R290

This refrigerant is better known as high purity propane. With the chemical formula of C3H8, it is one of the natural gases that due to its high cooling capacity and consequently lower consumption compared to gases, R290 refrigerant gas is a suitable alternative to R22 and R12 gas and has been considered by the world’s refrigeration industry in the construction of refrigerators. Freezers and gas coolers are used.

Refrigerant R404

One of the industrial refrigerants, which is a combination of three other refrigerant gases, is called R404. Freon gas compounds R404 are R12, R22 and R502 gases. The point about composite refrigerants is that they must have a liquid refrigerant to charge them. R404A gas is a non-destructive ozone layer gas and a good alternative to R502 and R22 at low and medium temperatures, ie evaporation temperature. It is lower than zero degrees Fahrenheit.

Due to the production of this gas for low temperature applications (evaporator temperature -20 degrees Celsius) and medium temperature applications (evaporator temperature -5 degrees Celsius) is used in the design of store freezers, food trucks and storefront refrigerators and ice makers.

Refrigerant R410a

R410a gas is a composite gas that is prepared by combining two other gases. The compounds of freon gas are R410a, 50% of gas R125 (pentafluoroethane) and 50% of gas R32 (difluoromethane).

R410a gas has a negative boiling point of -51.4 degrees, which is much higher than R22 gas, which has a boiling point of -40.8 degrees, and is compatible with the ozone layer, which has a very good cooling capacity and one It is one of the most widely used gases in domestic and industrial sectors. R410 is currently the best choice for use in chiller cooling systems and small heat exchangers such as inverter and low-consumption gas coolers.

It should be noted that refrigerants R11 and R12 are the first generation of freon refrigerant gases, which have become obsolete due to their destructive effect on the ozone layer.

The following table lists the characteristics of these refrigerants along with their advantages, disadvantages and applications.

Freon gas effects

Refrigerant poisoning is one of the most important issues that people should pay close attention to. Refrigerant gases are an important application in the cooling process of refrigeration appliances and cooling devices such as refrigerators and air conditioners. But it should be noted that in addition to the important applications that these gases have, they can also have negative and harmful effects on human health and the environment.

Refrigerant poisoning with freon gas (containing chemicals called fluorine hydrocarbons) in refrigerants is rare, but occurs by inhaling or eating a chemical called freon, and occurs when a person is exposed to chemicals. Used to cool devices and are all important transferees who use this substance as a psychotropic drug. Exposure to small amounts of freon in the open, such as: Contact with small amounts of freon or skin or a small leak in the home environment usually does not cause serious damage. But it does damage to the body. But when inhaled deeply, it can cut off vital oxygen to cells and lungs. If you notice any signs of freon poisoning, you should see a doctor or emergency room immediately. However, if inhaled in high concentrations of freon gas, it can be dangerous and cause damage to the human body, including:

Respiratory problems

Fluid growth in the lungs

Limb injury

sudden death

Freon gas in refrigeration systems

Refrigerants, or freons, are very diverse, each with unique characteristics and signs, such as Freon 12, Freon 11, Freon 114, and Freon 113, which are types of Freons. But of all the Freons, R22 is the most famous and well-known. R22 gas is mostly used in the refrigeration and cooling process of refrigeration equipment, therefore it is one of the most widely used refrigerant gases. The main difference between freons is mostly due to the number of constituent atoms, and the number of chlorine or fluorine or carbon indicates the type of freon you want.

The operating temperature of the freons is different. For example, the required temperature of the Freon 114 can be as high as -100 and operate in cycles. But the most ideal temperature required for a refrigerant in a refrigeration cycle is a maximum of -50. Freons do not cool the ice by themselves, but increasing and decreasing the pressure in a cycle can determine the temperature of the freon, and it should be noted that some freons can have a working temperature of up to +15 degrees.

In the refrigeration cycle, two important elements are the coils and the compressor. First, the compressor is responsible for compressing and compressing the freon gas. After doing this and according to the laws of thermodynamics, the temperature and pressure of freon gas rises and heats up. Then the process of liquefaction of refrigerant gas takes place and passes through coils to become liquid and somehow loses its heat in the condenser. . The temperature of the refrigerant in the liquid state is still lower than the ambient temperature, and as a result, heat is transferred from the environment to the refrigerant inside the evaporator, and this time the environment loses its heat and becomes cooler.

This heat is absorbed until the freon gas evaporates to a relative equilibrium with room temperature. This gas re-enters the compressor and the cycle is repeated until the temperature inside the space reaches a certain value and remains constant in the same state.

One of the drawbacks of using these refrigerants is their leakage, which either occurs spontaneously or occurs during system repair or installation and changes. This causes a change in the efficiency of the cooling system. Also, this leakage for the environment, especially The ozone layer is very destructive and harmful. For this reason, manufacturers thought of replacing cheaper and more usable refrigerants.

Conclusion

Refrigerant systems are always needed to build refrigeration systems such as refrigerators, air conditioners, car air conditioners, and so on. In the past, ammonia was used as a refrigerant, but with the discovery of Freon 12, this gas quickly replaced the old refrigerants and shook the world’s refrigeration industry. However, due to the geothermal effects of Freon 12 and refrigerant 22, their use has been limited over time and they have been replaced by other refrigerants. The criteria for selecting gases are suitable thermodynamic properties and low GWP index. Today, most combined refrigerant gases are used in the manufacture of refrigeration equipment.