The Working Principle Of An Air Conditioning System
WORKING PRINCIPLE OF AN AIR CONDITIONING SYSTEM
First, an air conditioning system serves several purposes. We do have air-conditioners in our homes, offices, cars and elsewhere, used for providing a cool and dry atmosphere. Although the air conditioning process provides cool air, its primary purpose, as the term describes, is for conditioning the air (or atmosphere) to a state that is comfortable for humans.
Air conditioning has evolved with time. Aforetimes, men invented various mechanisms for the aim of accomplishing this purpose. Modern air-conditioning works with the principle of thermodynamics. They literally helps in the transfer of heat within areas. This article provides information on the working principle of the air-conditioning system.
A very basic air-conditioner constitutes some components working in a cycle to achieving the aim. This parts function to actualizing the operation. Proper understandings of the role they play enable one to correctly determine the principles of the working of an air-conditioner.
There are three Key parts in the AC unit.
These include the;
- compressor
- condenser
- evaporator.
The units compressor and condenser are typically located in the outside part of the air conditioning system. The evaporator is usually found inside the house. Nonetheles, it is important at this point to note that it is at a low pressure gas that the cooling fluid gets to the compressor of the air conditioner making the compressor to squeeze this gas/fluid and the molecules become packed closely together. Likewise is is necessary to point out here that the closer the compressor forces these molecules together, then the higher the temperature and energy rise.
Then, the working fluid leaves the compressor as a high-pressure (hot gas) moving it to the condenser. The outside unit of an air conditioning system which is the condenser has metal fins all around the housing. The function of the fins is to perform the function of the radiator on a vehicle, thereby helping to dissipate heat more quickly.
When the fluid leaves the condenser, it is much cooler and it changes from gas to liquid because of the high pressure affording the fluid to make way into the evaporator via a minute/narrow hole. However, by the time the liquid reaches the side of the passage, a drop in pressure is experienced making the fluid to evaporate into gas and the heat is removed from the surrounding air. Nonetheless, the heat talked about here is what is needed to dissociate the molecules of the liquid into gas. There is also a metal fin on the evaporator which is used to exchange energy (thermal) with the surrounding air.
When the refrigerant leaves the evaporator, it is once again a low-pressure chillled gas. The process begins all over again when it goes back to the compressor. However a fan is usually connected to the evaporator which assists in spreading air around where the air conditioner is set to provide cooling as well as around the evaporator fins . So what's next, it is the turn of the air conditioner to sucks air into the ducts via a vent and this air is then used in cooling the gas in the evaporator, and as the heat is removed from the air, it becomes cool. The ducts then blow air back into the house.
This process continues until the inside air of your home or business reaches the desired temperature. However, you may still be wondering why the air conditioner goes off at times! It is because it has a thermostat which notifies it whenever the room attains the desired temperature. When the room heats up again, the thermostat turns the air conditioner back on until the preferred ambient temperature is achieved again”.
Now that we understand the general operations of an air-conditioning system. Next, we will establish the definitions and workings of each of its basic components. These include:
- evaporator
- compressor
- expansion valve
- condenser.
The evaporator
From its name, the evaporator is where the refrigerant fluid evaporates. The evaporator is situated in the interior unit. It mostly constitutes tubular pipes that are wound to several layers. This tubes serves as a passage for the very cold refrigerant liquid.
The essence of this is to absorb heat (latent heat of vaporization) from the inside which vaporizes this liquid into a very cool gas. The evaporator does not necessarily increase the temperature of the refrigerant but it definitely changes its phase (liquid to gas). By so doing the evaporator performs two functions.
First by removing heat it cools the atmosphere of the interior. And secondly, since the temperature of the refrigerant is well below that of the freezing point of water, it implies that the water vapour in the atmosphere loses thermal energy and changes its phase to liquid and then to solid ice which appears as a white coating on the evaporator tubes. This function reduces relative humidity and therefore causes a drier atmosphere inside.
The evaporator gets its cold refrigerant liquid from a suction port that is connected to the expansion valve and delivers the cold gas the compressor in the exterior unit. There is a fan or blower just behind the evaporator that increased the kinetic energy of the air around the evaporator, this ensures convectional heat transfer to ensure that the purpose of air-conditioning is speeded.
Compressor
A compressor is the device that increases the pressure and temperature of a gas by increasing the molecular motion of its particles. The compressor gets cool refrigerant gas from the evaporator and releases very hot and pressurized gas to the condenser. The purpose of the compressor is to ensure that the heat got from inside is well energized before it is dissipated to the surrounding atmosphere.
It comprises of reciprocating mechanism which is driven by an electric motor and this mechanism is what increases the pressure of the gas by compression. The general gas law states that for every increase in the pressure of an ideal gas at constant volume there is a proportional increase in the temperature.
This is the reason why a compressor as well increases the temperature of the refrigerant gas. It is necessary for this high temperature gas to be released to the condenser because the outside atmospheric temperature is normally higher in comparison to the interior.
Condenser
The purpose of the condenser is to receive the high-pressure gas from the compressor and convert this gas to a liquid. This it achieves by heat transfer, or the thermodynamic principle that heat goes usually from a warmer place to a cooler place or from a warmer substance to a cooler substance. However, the air passing through the condenser coils takes off the heat thereby making the gas condense. Likewise it is important to quickly take note that the condenser usually looks like the one found in an engine radiator. The condensers used on R-134a and R-12 systems are not interchangeable as the earlier has a different molecular structure and requires a large capacity condenser.
As the compressor subjects the gas to increased pressure, the heat intensity of the refrigerant is actually concentrated into a smaller area, thus raising the temperature of the refrigerant higher than the ambient temperature of the air passing over the condenser coils. It is necessary to avoid clogged condenser fins as they will result in poor condensing action and ultimately decreased efficiency.
Expansion valve
The expansion valve system comprises of very narrow tubes that expand with length. These tubes, known as capillary tubes collect the condensed (liquid) refrigerant from the condenser and takes it through an expansion process (where there is a huge fall in the pressure of the fluid). As a result, there is also a reduction in the temperature of the fluid. This fall in the temperature makes the fluid arrive at the state in which it initially entered the evaporator.
The expansion process can as well be referred to as the throttling process in a thermodynamic cycle. This is because its major aim is to reduce the pressure of the fluid.
Apart from these four basic parts of the air-conditioner, there are several other parts that are important in making the system effective and efficient. The thermostat, high side and low side ports as well as metallic hoses all ensure that there is proper flow of the fluid and as well ensure temperature regulation.
The Thermostat
The hvac thermostat we will be discussing here is a room thermostat. This air conditioning thermostat controls space temperature for comfort purposes.
Air conditioner thermostat works by depending on random air current. Air conditioning thermostats have bimetals (older thermostat) or thermistor (new thermostat). These bimetals or thermistor sense the air current returning to the return ducts or the surrounding air.
The basic operation principle of air conditioning thermostat is it relies on random air current that passing thought it to determine the room temperature. It uses room temperature to compare with the setpoint temperature.
AC thermostat is the device that controls the air conditioner units. It uses to turn the heater or AC unit ON and OFF. Hvac thermostat is a temperature controls. It controls the temperature of specific building.
High and Low side
These terms describe well, their function. The High side of the air-conditioner is the region that connects to the condenser while the low side connects to the evaporator.
The High side is so called, because high temperature and pressure refrigerant gas enters the condenser and high temperature liquid leaves it. The low side has very low temperature liquid refrigerant entering the evaporator and low temperature and pressure gas leaving it.
The Air conditioning system is very similar to the refrigerating system. They operate the same thermodynamic processes. The major differences between these are the refrigerants used and their purpose. In refrigerators, the refrigerants used are different from those used for the air conditioners to ensure that there is efficient performance.
On the other hand the opposite of the refrigerator and the air conditioners is the heat pump. The heat pump operates in an inverted process. While the air conditioner collect heat from the warm inside and releases it to the hotter outside, the heat pump takes heat from the cool outside and supplies it to the inside to keep it warm. The heat pump is used in very cold regions to adequately supply households with heat
With the proper understanding of the working principle of an air conditioning system established, the heat pump’s principle follows a similar path. In this case the process is reversed. The condenser, which is outdoor in the air conditioner, is indoor in the heat pump, while the evaporator, which is indoor in the air conditioner, is outside in the heat pump. Both the compressor and the expansion valve serve the same purpose for both of them.
More about Air conditioners
The air conditioners we have at home, office, in our cars and everywhere else, have to be regularly serviced to ensure optimal operation. Several anomalies may occur if adequate routine maintenance is not carried out on the system. The most common of these is having no cooling or drying effect. When this happens, the most likely of the causes are the following:
- A faulty compressor
- Leakage of refrigerant fluid in the system
- Anomalies in the electrical system such as bad thermostats
Some other possible faults developed on air conditioners are related to the blowers or fans, the type of fluid used and filters used to clean particles in the interior atmosphere.
- https://howardair.com/how-does-air-conditioning-work/
- https://home.howstuffworks.com/ac2.htm
- Teachings from my thermodynamic lecturer in class
It blew my mind when the professor told us if we want to defrost the windows inside our car faster to turn on the a.c. as it helps to condition the air and remove the moisture while having the heat turned on.
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Thanks for the information
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