Air Conditioning is the action of cooling. And in practice this requires removal of heat and discarding it at a higher temperature. Thus it is therefore the science of moving heat from low temperature to high temperature. In addition to chilling and freezing applications, we use this technology in air conditioner and heat pumps.
What is Air Conditioner ?
An air conditioner is an electromechanical device. It gives cool air inside our home or enclosed space by actually discarding heat and humidity from the indoor air. It gives back the cooled air to the inside space, and sends the unwanted heat and humidity outside world.
By removing heat and humidity from inside space it makes it comfortable for us. So that we can do our work easily. Now a days air conditioner is an important part of our life.
Types Of Air Conditioners Used in Our Life.
Air Conditioners are of various types such as
1- Window Air Conditioner 2- Split Air Conditioner
3- Central Air Conditioner 4- VRV & VRF
VRV- Variable Refrigerant Volume
VRF– Variable Refrigerant Flow
5- HVAC-Heating, Ventilation, and Air Conditioning
6- AHU-Air Handling Unit 7- Tower Air Conditioner
Main Parts Of Various Kinds Air Conditioner ?
1- Compressor 2- Evaporator Coil 3- Condenser Coil
4- Expansion Valve 5- Blower 6- Fan 7- Fan Motor 8- Blower
Motor 9- PCB (Printed Circuit Board) 10- Contactor 11- Air Filter
12- Cooper Pipe 13- Capillary 14- Insulation 15- Complete
Housing With Hanger & Stand 16- Refrigerant 17- Other Control Units etc.
How Does An Air Conditioner Work ?
When the system is on. The liquid refrigerant inside the evaporator coil changes into gas. Heat from the inside air is taken by the refrigerant. Thus air conditioner makes the air cool as the air passes over the coil. The blower fan of indoor unit pushes the cooled air back into the various living areas. Thus an air conditioner cools any enclosed space.
Refrigerants used in Air Conditioner
IDEAL PROPERTIES FOR A REFRIGERANT
These are following
1- Latent heat of vaporization should be good
2- High suction gas density
3- Positive but not excessive pressures at evaporating and condensing conditions
4-Critical temperature and triple point well outside the working range
5- Chemically stable, compatible with construction materials and miscible with lubricants
6- Non-corrosive, non-toxic and non-flammable
7- High dielectric strength
8- Environmentally friendly
9- Low cost
10-Needless to say, no single fluid has all these properties, and the choice of fluid for any particular application will always be a compromise.
Use Of R134a and R407C In Air Conditioner
Engineers use these refrigerants for air conditioning in the place R22 in many applications. R134a has a relatively low pressure. And therefore about 50% larger compressor displacement. When compared to R22, and this can make the compressor more costly. It uses very successfully in screw chillers. Where short pipe lengths minimize costs associated with larger tubing. R134a also uses where needs extra high condensing temperatures. R407C is a zeotropic mixture. It consists of 23% R32, 25% R125 and 52%R134a. It has properties close to those of R22. Its glide and heat transfer properties generally penalize the system performance. Although counter flow heat exchange can deliver some benefit with plate heat exchangers.
Use Of R410A In Air Conditioner
This fluid looks discouraging at first. Because of its poor theoretical performance. It has low critical temperature and high pressure. However. The refrigerant side heat transfer is about 35% better than with R22. Whereas for R407C and R134a it is poorer. The pressure drop effect in equivalent heat exchangers is 30% less. Research has shown that systems optimized for R410A can deliver up to 5% better system COP than R22 equivalent systems. Whereas R407C systems tend to be about 5% poorer. Many air-conditioning suppliers are switching to R410A, especially for direct expansion type systems.
Use Of R404A in Air Conditioner
R404A is an HFC. It has been designed for commercial refrigeration. Where it is now widely applied. It has superior performance to the other HFCs in low temperature applications. It also exhibits low compressor discharge temperatures. Which makes it suitable for single stage compression avoiding the need for inter-stage cooling
Use Of R717 Ammonia in Air Conditioner
We use Ammonia as a refrigerant for industrial applications. The engineering and servicing requirements are well established to deal with its high toxicity and low flammability. Technical developments are extending the applications for ammonia. We cannot use Ammonia with copper or copper alloys. So refrigerant piping and components have to be steel or aluminium. Where copper has been the base material for piping and plant. One property that is unique to ammonia compared to all other refrigerants is that it is less dense than air. So a leakage of ammonia results in it rising upwards and into the atmosphere. If the plant is outside or on the roof of a building. The escaping ammonia can drift away without harming occupants. We can detect Ammonia by its characteristic odour at very low concentrations. This acts as an early warning signal.
Use Of R290 Propane and Other Hydrocarbons
Hydrocarbons such as propane and butane are being successfully used in new low-charge systems. Where CFCs and HCFCs have previously been employed. They have obvious flammable characteristics which must be taken into account. There is a large market for their use in sealed refrigerant systems such as domestic refrigeration and unitary air conditioners.
Use Of R744 Carbon Dioxide
R744 Refrigerant is again attracting much interest. It has high latent heat & good heat transfer coefficient combined with high pressure. The density under operating conditions results in the ability to produce large amounts of cooling with very small displacement compressors and small diameter pipelines. Its main disadvantage is its low critical temperature. This is also a disadvantage with HFC refrigerants, but carbon dioxide is much worse. In these cases the counter flow gas cooler is a good solution. Much work has also been done on the use of carbon dioxide for vehicle air conditioning. Another aspect of the R744 transcritical cycle is the ability to revert to a conventional vapour compression cycle in low ambient conditions. Good average seasonal efficiency may be achieved in locations where heat can be rejected at temperature well below 30°C.