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In this part of Full HVAC course, we are going to learn about refrigerants in details.
Refrigerants
There are many different refrigerants around today that are being used in HVAC systems. There was once only one kind of coolant in use, called Freon. If we talk about the history of refrigeration, we find out that the first refrigerated food was actually ice cream. Ice cream is frozen milk. So what happened? We started using refrigerators to keep our foods fresh. As time passes, refrigerators evolved and they became more sophisticated. A refrigerator uses two types of refrigerants; R-22 and R-410A.
- R-22
R-22 is a hydrochlorofluorocarbon (HCFC). HCFC’s were created back in the 70’s and 80’s. These gases have been replaced by much safer alternatives. R-22 is considered safe to humans and animals, however, it is not considered good for the environment. One thing to note about R-22 is that if it leaks near water, it may damage the ozone layer. If you want to know more about R-22, read this article. - R-410A
R-410A is a hydrofluoroether. It’s a type of refrigerant that is commonly used in commercial air conditioners. R-410A is considered very effective at cooling down homes and offices. In fact, it's the most effective among the air conditioning gases. However, R-410A is even more dangerous than R-22. Because it doesn’t destroy the ozone layer, R-410A could pose a threat to the planet’s climate. Fortunately, R-410A does not harm the human body. But the problem is that it has high global warming potential. To learn more about R-410A, check this link. If you would like to learn more about refrigerants, click here. - What Are Refrigerants Used For?
You might be wondering what these different refrigerants are used for. Well, refrigeration is mainly used to keep food cold or keep the temperature of the room down. Food is sometimes kept in fridges and freezers, and also some rooms need to stay cooler. That’s where this technology comes in. Refrigerators help us preserve food longer, and keep things colder. Freezers allow you to store food in low temperatures without spoiling. And these refrigerants are necessary!
Why use refrigerants?
- Refrigeration is often the first step for air conditioning systems, providing cooling before heating is even considered.
- A properly functioning system is essential for maintaining a comfortable temperature inside the home.
- Refrigerants have many different uses, including keeping food fresh, eliminating odors, and removing moisture from air.
What refrigerants are commonly used today?
- R-22 (Freon)
- R-134A (Freon)
What should I be aware of if using a refrigerant?
- Keep refrigerant out of reach of children, pets, and animals.
- Never allow refrigerants to enter the environment via rainwater runoff, seepage, or any other means.
- Avoid breathing refrigerant fumes and never eat or drink products containing these chemicals.
- Do not remove insulation from the condensate drain pan.
- Always wear protective equipment when handling refrigerant.
Most refrigeration systems use ammonia as the working fluid. Refrigerants in air conditioning systems work by absorbing heat at low temperatures and releasing it as they warm. Ammonia absorbs heat and releases it as water vapor. The rate of cooling increases as the temperature rises above the boiling point of water. When the refrigerant reaches its saturation pressure, the gas expands, pushing out the absorbed heat. As it cools down, the expanding gas causes the refrigerant to contract again, returning to its original liquid state. This cycle repeats itself until the system stops operating.
Working Fluids
As mentioned earlier, refrigerants in air conditioning systems use ammonia as their working fluid. The refrigerant evaporates when heated, absorbing heat, and condenses back into a liquid as it cools. The refrigerant then returns to its gaseous state, absorbing more heat and repeating the cycle. There are two types of working fluids: non-azeotropic and azeotropic. Non-azeotropic fluids have different densities at different temperatures. Azeotropic fluid has identical densities at different temperatures (or ratios). You may not know if a particular product is azeotropic or not, but if it isn't, it may still perform well enough for your application.
Non-Azeotropic
R134a is an example of a non-azeotropic refrigerant. R134a is a mixture of propane and butane, and has a density of approximately 1.058g/cm³ at 20ºC. At higher temperatures, its density decreases, causing it to expand. In contrast, R12 is a non-azeotropic, mono-flouropropane refrigerant. Its density changes little at high temperatures. The expansion of R12 is less than for R134a, making it a good choice for applications where heat dissipation is less critical.
Azeotropic
Sulfur dioxide is an azeotropic refrigerant. Sulfur Dioxide has similar properties to Freon refrigerants, except that it doesn't require any oil to lubricate. Sulfur dioxide has a lower viscosity than Freon refrigerants, however, and therefore requires slightly smaller compressors. Other azeotropes include hydrocarbon mixtures, carbon dioxide, nitrous oxide, and ammonia. Hydrocarbons (like benzene, toluene, xylene, pentanes, hexanes, heptane, octenes, etc.) don't mix well with each other (at least none I've ever heard of doing), so they can only be mixed with other materials that aren't azeotropic with them (e.g., Freon). Carbon dioxide is also a zeotropic refrigerant, meaning that it's both miscible and immiscible with many different substances. However, carbon dioxide behaves differently depending on its concentration, therefore it's not considered to be an ideal refrigerant. Nitrous oxide and ammonia are both very flammable gases, and therefore should never be used as refrigerants. However, they're not very expensive, so they're sometimes used.
Primary and secondary Refrigerants
Primary refrigeration is cooling using a liquid refrigerant. A compressor takes in gas and turns it into a high-pressure vapor. Then, the pressurized vapor is passed through a condenser where it cools down dramatically. As the gaseous mixture passes through the condenser coil, the refrigerant drops back down to its liquid state. In this stage, the liquid moves through the expansion valve and then returns to the evaporator coil, absorbing heat and causing it to become a superheated vapor. On the return trip across the evaporator coil, the air passing over the surface absorbs heat and becomes cold. A fan blows the air inside.
Secondary refrigeration is cooling using a gas instead of liquid. Secondary refrigeration includes all types of commercial refrigeration including chiller systems, room air conditioners, and other technologies. These processes use carbon dioxide gas, ammonia gas, propane gas, and others instead of the traditional R22 or Freon gases.
- When choosing between primary and secondary refrigeration, consider your budget, application, and future maintenance requirements.
Freon
Freon is a class of refrigerants commonly used in household air conditioners (HVAC). This material was discovered in 1938 and was originally produced by DuPont Company. Many people mistakenly think that freon is not toxic since it doesn't break down easily. However, freon leaks out of devices and contaminates the environment. It has a high global warming potential. Freon has been phased out of production since 2001 due to environmental concerns.
Hydrofluorocarbons
Hydrofluorocarbons, or HCFCs, were developed in the 1970s as alternatives to CFCs and have similar characteristics and uses. HCFCs were introduced initially as replacements for CFCs and then gradually replaced them. HCFCs are now being phased out. There are currently no legal restrictions on HCFC usage. According to the Environmental Protection Agency, HCFCs do not deplete the ozone layer and pose no threat to humans or ecosystems. However, some studies suggest they may deplete the stratospheric ozone layer.
Chlorofluorocarbons (CFCs)
Chlorofluorocarbon compounds were first developed in 1929 by the German chemists Walter Wüstner and Hans Schlesinger. They were intended to replace ozone-depleting substances, including halons. The best known compound is trichlorofluoromethane, or CCl3F, or R-12. CFCs are effective at killing insects and algae. They are also used in industry and agriculture. But some CFCs react with sunlight and chlorine atoms to form ground-level ozone. Ozone is responsible for smog and is a major contributor to climate change. On October 16, 1987, the Montreal Protocol was signed in order to eliminate the use of these chemicals. At that time, over 100 million tons of CFCs had already been manufactured. Scientists estimate that it would take centuries before CFCs are completely removed from the atmosphere.
Propane
Propane is a commonly used home heating fuel. It is often referred to as propylene gas, which is a mixture of two hydrocarbon gases, propylene and ethane. As a refrigerant, it has similar characteristics to R-22, meaning it does not produce much condensation or frost buildup in the evaporator coil. It is also safe to use around children and pets, and can easily be stored at room temperature. However, it's flammability requires proper ventilation while using it.
Selection of Refrigerant in HVAC
Refrigerants are classified based on their chemical structure and their boiling point. Hydrocarbons, fluorocarbons, and sulfur compounds are commonly used and have been studied extensively for their environmental impacts. These chemicals may cause damage to the ozone layer if released into the atmosphere. Thus, alternatives to traditional refrigerants are being researched.
The selection of a refrigerant requires consideration of several factors, including cost, efficiency, safety, emissions, and performance.
There are many types of refrigerants, each with varying amounts of carbon, hydrogen, oxygen, and fluorine atoms. The refrigerant's efficiency is determined by the number of carbon atoms and the bond energies of individual carbon atoms. Carbon bonds are weaker than hydrogen bonds, and thus it takes less energy to break them. Hydrogen atoms have the strongest covalent bonds, meaning they take the least amount of energy to break. Therefore, using fewer carbon atoms and stronger bonds makes the refrigerant more efficient.
As the name suggests, the major difference between refrigerants is their boiling points. Higher boiling points mean lower vapor pressures, enabling the refrigerant to evaporate more easily. Boiling points range from -40 degrees Celsius (-40°F) to +200°C (+400°F). The best refrigerants are those with a boiling point below 0°C (-32°F), since they can be liquefied without causing frost. However, some cooling capacities require a refrigerant with a higher boiling point. The ideal refrigerant should be nontoxic, nonflammable, noncorrosive, and able to withstand high pressure.
Cost is another factor that should be considered. Because an HVAC system uses a small fraction of the total electricity produced worldwide, the electrical grid is susceptible to disruptions caused by power outages. If the refrigerant runs out before the system shuts off, the compressor could become damaged. Furthermore, a single refrigerant charge lasts only about 10 years, after which time the refrigerant will need to be replaced.
Safety is yet another concern. A refrigerant leak could contaminate groundwater and pose a risk to humans and animals. Refrigerants are flammable and toxic, and they can react violently with water, metals, and other refrigerants. To reduce the risks associated with refrigerants, safety standards were developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) in 1977. The requirements cover a wide variety of issues, including:
- Designing safe systems
- Ensuring proper installation
- Testing and certifying the equipment
- Reporting leaks and malfunctions
Safety regulations were updated in 1990 to provide guidelines for the replacement of refrigerants containing freon. According to the Environmental Protection Agency, it is illegal to release freon directly into the environment. Instead, it must be disposed of safely and properly. Most industrial facilities are equipped with a recovery unit for recovering leaked refrigerants.
Properties of Refrigerant
Refrigerant is used for many purposes in HVAC systems. It lowers the temperature inside buildings, prevents mildew growth, and removes moisture from air. It also eliminates odors caused by mold and bacteria, and reduces the risk of fires. But what exactly is refrigerant? What are its physical characteristics? How does it work? And how do we use it?
Properties and Uses of Refrigerant
Refrigerants change state between liquid and gas at low temperatures (below 0°C). As they lose their gaseous state, they cool down the surrounding area. The opposite happens when they start to warm up, causing them to vaporize into the surrounding air. Refrigerant is added to the system only after completing the evaporator coil. Refrigerant flows through the system until it reaches the compressor. When compressed, the refrigerant becomes saturated with water and returns to a gas-like state. Once it leaves the compressor, it enters the condenser coil and changes back to a liquid-state. In the condenser coil, it absorbs heat from outside air. After passing over the condenser, it moves to the expansion valve. The pressure drops here, and the refrigerant turns into a gas once again. As it expands, it releases heat to the surroundings. Because it’s now cooled down, it reverts back to a liquid state. At this point, it is ready to flow back to the evaporator coil where it begins the cycle all over again.
Physical Characteristics of Refrigerant Gas
The physical properties of refrigerant determine its suitability for any given purpose. Refrigerant gases have specific characteristics based on the type of material they were originally derived from. That determines the chemical makeup of the refrigerant gas. Different types of materials give off different effects when exposed to heat. Liquids expand when heated, whereas gases shrink in volume. Gases also conduct electricity well, while liquids don’t. This means they react differently in electrical components. Most importantly, they have different densities than each other. One of the best examples of the differences is ammonia and benzene. Ammonia is flammable, while benzene is not.
Types of Refrigerants
There are four different types of refrigerants in the world today: hydrocarbons (HC), chlorofluorocarbons (CFC), fluorinated hydrocarbons (FH), and hydrofluoro carbons (HFC). Hydrocarbon refrigerants are those that were first invented in the early 1900's. CFC and HC refrigerants date back further still, and are similar in composition to the original hydrocarbon refrigerants. Both CFC and HC refrigerant gases are toxic, flammable, and environmentally harmful. Fluorine makes these gases less harmful, but it also makes them heavier and less dense. Chlorofluorocarbon gases are considered greenhouse gases that contribute to global warming. Fluorinated hydrocarbon gases are slightly less toxic and nonflammable than CFCs, but they are still considered environmental hazards. HFCs are the newest refrigerant gases, and they have minimal environmental impacts. There are several HFCs currently being produced, including R134a, R32, R600a, R507, and R410A. These gases are considered safe alternatives to the older refrigerants.
Advantages of Using Refrigerant Gases
Using refrigerant gases is much safer than using CFC and HC refrigeration. The refrigerant gases perform their duties without harming the environment, unlike the CFC and HC refrigerators. Another advantage is that these gases do not require a phase change to get cold. Instead, they remove heat directly from the surrounding air. Since they aren't subject to phase changes, they won’t damage compressors. Furthermore, unlike the older refrigerants, these gases can be easily recycled. Once they reach their boiling point, they boil away completely. Once removed, they can be returned to the system and reused.
The refrigerant is a chemical (a gas) that is super-cooled to create cold air around the area where the equipment is located. When it comes time to use the air conditioning, it is removed from the compressor and cooled before being released into the room. The refrigerant is then compressed again to make it even colder.
Refrigeration is not just limited to cooling food; refrigerants are used in many different ways in HVAC systems. In some cases, they are used to keep water cool for drinking purposes. As an example, refrigerant is added to a building’s water supply system, which makes the water colder than outside temperatures. Then, people drink the water, which causes them to sweat out moisture and feel refreshed.
There are two types of refrigerants that are commonly used today: R134A and R22. Both of these refrigerants have their own unique uses, pros/cons, safety measures, and costs associated with using them. Below are some details about each type of refrigerant and how they work.
R134A Refrigerant
This particular kind of refrigerant is considered safe and effective at causing water to freeze, making ice cubes, and cooling beverages. However, since it is flammable and toxic, it should only be used if appropriate precautions are taken. Additionally, it cannot be mixed with any sort of oil or lubricating agent, which means that it does not provide a protective layer between the metal parts of the compressor and its internal components. All of this puts consumers at risk of fire and possible death. There are two primary dangers that come with using R134A refrigerant. One is toxicity, which is caused by exposure to high concentrations of refrigerant vapors. Another danger is fire, which happens when the refrigerant gets exposed to oxygen.
Most manufacturers recommend that you keep the refrigerant away from clothing, skin, hair, and eyes. If you work in an area that requires the use of refrigerant, you should wear protective gear to avoid inhaling the vapor. Also, ensure that you do not let children play near appliances that use R134A refrigerant, as they may accidentally ingest it.
The cost of buying refrigerant is $10 per gallon. You can buy refill kits online, but you might need to pay additional fees for shipping charges. It costs anywhere from $100-$400 to get your unit replaced with the right kind of refrigerant.
R22 Refrigerant
This type of refrigerant is also called freon. This particular kind of refrigerant works well for air conditioners that need strong cooling power. Its high capacity and low operating temperature make it ideal for cooling down homes and businesses. It is less expensive than R134A refrigerant and provides a much longer service life. This is great news for homeowners, especially those who are experiencing a seasonal drop in temperature.
Like R134A refrigerant, however, R22 is flammable and poses a threat to humans. Therefore, proper ventilation procedures and caution should always be maintained while using it. Like R134A refrigerant though, R22 refrigerant is not recommended for babies, young children, pregnant women, or pets. If you work in a place where R22 refrigerant is used, you should wear protective clothing and gloves. Otherwise, you could potentially expose yourself to dangerous levels of refrigerant.
When buying replacement units, you will likely find lower prices for R22 refrigerant than R134A refrigerants. A typical fee for getting a replacement unit is $50.
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