As you would appreciate, modern-day indoor comfort is heavily reliant on having conditioned air. Our air conditioners have become indispensable parts of our lives; we use air conditioners on a daily basis. However, the vast majority of us do not have an idea of the various components that make up the air conditioner. With this in mind, herein we will explore the refrigerant, delving into what it is, the various types of refrigerants, and most importantly, its purpose in the air conditioning system.
Refrigerant: What Is It?
A refrigerant is a chemical fluid that readily absorbs heat and transports the heat from one place to another within an enclosed system that is the HVAC system. Effective and efficient refrigerants are not only able to absorb heat, but they must also readily shift from gaseous state to liquid state and vice versa in a process called phase transition. An ideal refrigerant should undergo phase transition without the need to apply enormous amounts of energy.
Other properties of importance to air conditioner designer include being non-toxic, being non-corrosive, and having a low Global Warming Potential and Ozone Depletion Potential. Furthermore, the fluid should have a relatively high density in its gaseous state and a low density in its liquid form to be effective at its purpose.
The Various Types Of Refrigerant In Use
There are numerous refrigerants in use today such as those from Bluonenergy.com. However, it is important to note that there are some refrigerants that are being phased out. These include HCFCs and HFCs such as R-22, better known as Freon. As such, even though they are available and in use today, they are being phased out in a process that is intended to last from 2010 to 2020. Beyond the deadline date, R-22 will not be manufactured and used as a refrigerant in the U.S. anymore.
Other refrigerants that are in use today include carbon dioxide, which is renowned for having a stellar heat transfer coefficient, ammonia, and hydrocarbon chemicals. These are the alternatives to the popular R-22 that has been in use for decades. The chemicals have been chosen to replace the HCFs and HCFCs due to it’s the thermodynamic properties but also the safe for the environment and nontoxic attributes.
The Purpose Of Refrigerant In Our Air Conditioning System
Regardless of the particular refrigerant in use, its function is same: to transfer heat from one part of the system (in this case, your indoor environment) to another part of the (the outdoors), thereby conditioning the target area. In other words, the refrigerants are used to absorb the heat from your home and dump the absorbed heat outdoors. To understand how refrigerants are able to achieve this, and, therefore, understand their purpose, we will delve into the entire process of refrigeration.
The vast majority of the residential air conditioners (as well as many industrial and commercial air conditioner) use the vapor-compression cycle refrigeration system to achieve air conditioning. The refrigerant begins its cycle inside the compressor of the air conditioner. At this part of the cycle, the refrigerant experiences a reduction in volume and is therefore compressed. Upon exiting the compressor, the refrigerant is superheated, usually to a temperature of about 150°F and also attains more pressure to become a high-pressure gas.
The gas is then moved to the condenser. The condenser is located in the outdoor unit of the HVAC system. In this part of the cycle, the condenser first removes the superheat from the vapor. This is achieved by moving outdoor air over the condenser coil. While the outdoor air tends to be warm, it is still cooler than the vapor in the condenser coil. As such, when air passes over the coil, it absorbed the heat from the vapor and dumps it to the environment. The refrigerant cools down to about 100°F.
Another consequence of the heat transfer from the refrigerant to the outdoor air is condensation. The refrigerant loses the heat energy that sustains the fluid in gaseous form and, therefore, it is converted to a liquid. All the while, the pressure in the condenser is kept constant for efficient heat transfer.
The next part of the cycle is the throttle valve or the expansion valve. The expansion valve causes the pressure of the gaseous refrigerant to suddenly drop. Consequently, the refrigerant experiences flash evaporation, allowing the liquid to lose even more heat. Furthermore, the sudden expansion causes auto-refrigeration of refrigerant, where less than half of the gaseous refrigerant turns to a liquid form. Importantly, this process also causes the refrigerant to experience a drop in temperature and pressure. As such, the end of the expansion valve, you end up with a mixture of gaseous and liquid refrigerant that has a temperature of about 20°F.
Thereafter, the refrigerant is passed through the evaporator coil. At this stage, the refrigerant is warmed and completely evaporated as it absorbs heat from the warm temperature that is blowing over the evaporator coil. This warm is supplied from the room you are cooling. As such, by absorbing the heat that is being supplied to the evaporator coil, you cool the air indoor, thereby “conditioning” the air. At this stage of the cycle, the refrigerant temperature is about 50°F. The refrigerant is thereafter taken to the compressor to start the cycle all over again.
All through the cycle, the refrigerant does not exit the copper tubes. The entire process takes place with the HVAC system in its charged state. It is important to note that the process of cooling your indoor environment does not “consume” the refrigerant; it remains at a constant level.
It is important to note that there are HVAC systems that utilize different cycles such as the vapor absorption cycle, the gas cycle, the reversed Carnot cycle, and the Stirling cycle. However, in most cases, the other cycles tend to be less efficient than the vapor compression cycle. Nonetheless, all these heat transfer mechanisms make use of a refrigerant.
In a nutshell, the purpose of a refrigerant in an AC system is to actually transfer the heat throughout the system. It is the medium through which heat is moved from the indoor environments to the outdoor atmosphere.