Air Conditioning :- For human comfort we need air conditioning system. Air conditioning means not only to mainatain room's temperature but to condition the air as well. Means in air conditioning we maintain comfortable temperature, air purification, control humidity, control odours and maintain level of oxygen by ventilation. Air conditioners are designed to maintain a temprature not below than 16 degree celcius. But human comfort level according to ASHRAE is from 20-24 degree celcius. An air conditioner should not run at temperature below this limit to protect human body's health.
There two Type of Compressors according to their construction :-
1. External Drive compressors
2. Harmetic compressors
1.1. External drive compressor is bolted togather and can be overhauled easily by opening each part. Its crankshaft extends through the crankcase. This compressor is drived by an external motor by a V-belt. This compressor can be a double or four cylinder compressor. This type of compressor were used in the past decade, now a days these compressors have been replaced with harmetic compressors.
2.1. Harmetic compressor is totally sealed by proper welding. The motor is directly connected with compressor inside the body of compressor. Crankshaft is not needed in this type of compressor. The electrical connections to the motor pass through dome by means of an insulated leakproof seal.
In modern air conditioners compressors are integrated with VFDs to reduce the power consumption. A VFD (Variable Frequency Drive) controls the rotation of motor by increasing or reducing the voltage but system never cut offs or cut in like in old compressor units. That is the reason we can now purchase 3 or 4 star rating air conditioners. In old air conditioners, when temperature inside the room reached to desired range, a senor on the evaprotor (indoor unit) made the system to completely shut down and when temperature rises it again put on the system automatically. When a compressor is switched on it need high amperes or power and after some time of running it power consumption reduces to normal. This process increases the power consumption and electricity bills are usually high. But in modern compressors the rotation is controlled and system dont need to cut off or cut in, so the power consumption is very low. These modern compressors can be run on a home inverter too, only that is the reason these are called inverter air conditioners.
There are five basic types of compressors according to working principle. In all compressor original energy source is an electric motor.
1. Reciprocating ( piston-cylinder) compressor.
2. Rotary compressor.
3. Screw compressors.
4. Centrifugal compressors.
5. Scroll compressors.
What is a condenser ?
A condenser works like a heat exchanger in refrigeration and air conditioning systems. Refrigerant from compressor is discharged at a high temperature and high temperature. The condenser condensate the refrigerant to bring its temperature down. A condenser may be of static type which is used in refrigerator and it may be of forced type which is used in air conditioner. A condenser is built from tubes of copper or any other material of high conductivity passing through a set of fins as shown in figure. These fins increase the performance of condenser by increasing the surface contact area with air. Number of fins in a condenser depends upon the usage if its used for air conditioning the number of fins will be more than that we use for a refrigerator. The reason is that refrigerator is used to create cooling for a tiny space and an air conditioner is used to produce cooling effect for a large area.
An expansion valve is used in refrigeration or air conditioning cycle to control the refrigerant flow. To produce cooling effect in evaporator it is necessary to drop the pressure of refrigerant coming from the condenser with low temperature but high pressure. When refrigerant passes through the small dia of expansion valve or capillary tube its pressure drops and suction pressure from compressor makes the refrigerant gas to expand. This expansion causes the cooling effect in the evaporator.
There are three types of expansion valves :-
1. Automatic expansion valve
2. Thermostatic expansion valve
3. Electronic expansion valve
Capillary tube :-
4. Evaporator:-
After passing through the expansion valve the refrigerant with low pressure and low temperature passes throught the evaporator. Where evaporation of refrigerant happens and cooling effect is produced in the conditioned space. As the refrigerant in the evaporator starts to boil and is converted into vapor form. Evaporator is known as cooling coil as well in indoor unit. Evaporator and condenser work same like an heat exchanger and are same in construction with combination of copper tubes and fins, but produce different effects.
Air conditioning and refrigeration has same cycle and four components to produce cooling effect. But main difference between them is, air conditioning is done for human comfort and refrigeration is done to increase the life of eatable products.
Let's understand how cooling effect is produced ?
There are four main components of refrigeration or air conditioner.
1. Compressor
2. Condenser
3. Expansion valve or capillary tube
4. Evaporator
Compressors are very important and expensive component of a refrigeration cycle. They are installed to produce a high pressure and high temperature refrigerant. If you look at a reciprocating compressor it will look like a car's engine. It is a combination of cylinder piston but an electric motor is connected to the shaft to move the piston. Lubrication is required same as an engine to minimize the friction of moving parts. If a compressor is out of oil, it will produce significant heat due to friction and parts will start to expand, finally it will seize the compressor. In compressors there is a crank case which is always filled with lubricant.There two Type of Compressors according to their construction :-
1. External Drive compressors
2. Harmetic compressors
1.1. External drive compressor is bolted togather and can be overhauled easily by opening each part. Its crankshaft extends through the crankcase. This compressor is drived by an external motor by a V-belt. This compressor can be a double or four cylinder compressor. This type of compressor were used in the past decade, now a days these compressors have been replaced with harmetic compressors.
2.1. Harmetic compressor is totally sealed by proper welding. The motor is directly connected with compressor inside the body of compressor. Crankshaft is not needed in this type of compressor. The electrical connections to the motor pass through dome by means of an insulated leakproof seal.
In modern air conditioners compressors are integrated with VFDs to reduce the power consumption. A VFD (Variable Frequency Drive) controls the rotation of motor by increasing or reducing the voltage but system never cut offs or cut in like in old compressor units. That is the reason we can now purchase 3 or 4 star rating air conditioners. In old air conditioners, when temperature inside the room reached to desired range, a senor on the evaprotor (indoor unit) made the system to completely shut down and when temperature rises it again put on the system automatically. When a compressor is switched on it need high amperes or power and after some time of running it power consumption reduces to normal. This process increases the power consumption and electricity bills are usually high. But in modern compressors the rotation is controlled and system dont need to cut off or cut in, so the power consumption is very low. These modern compressors can be run on a home inverter too, only that is the reason these are called inverter air conditioners.
There are five basic types of compressors according to working principle. In all compressor original energy source is an electric motor.
1. Reciprocating ( piston-cylinder) compressor.
2. Rotary compressor.
3. Screw compressors.
4. Centrifugal compressors.
5. Scroll compressors.
What is a condenser ?
A condenser works like a heat exchanger in refrigeration and air conditioning systems. Refrigerant from compressor is discharged at a high temperature and high temperature. The condenser condensate the refrigerant to bring its temperature down. A condenser may be of static type which is used in refrigerator and it may be of forced type which is used in air conditioner. A condenser is built from tubes of copper or any other material of high conductivity passing through a set of fins as shown in figure. These fins increase the performance of condenser by increasing the surface contact area with air. Number of fins in a condenser depends upon the usage if its used for air conditioning the number of fins will be more than that we use for a refrigerator. The reason is that refrigerator is used to create cooling for a tiny space and an air conditioner is used to produce cooling effect for a large area.
3. Expansion Valve or capillary tube :-
An expansion valve is used in refrigeration or air conditioning cycle to control the refrigerant flow. To produce cooling effect in evaporator it is necessary to drop the pressure of refrigerant coming from the condenser with low temperature but high pressure. When refrigerant passes through the small dia of expansion valve or capillary tube its pressure drops and suction pressure from compressor makes the refrigerant gas to expand. This expansion causes the cooling effect in the evaporator.
1. Automatic expansion valve
2. Thermostatic expansion valve
3. Electronic expansion valve
Capillary tube :-
4. Evaporator:-
After passing through the expansion valve the refrigerant with low pressure and low temperature passes throught the evaporator. Where evaporation of refrigerant happens and cooling effect is produced in the conditioned space. As the refrigerant in the evaporator starts to boil and is converted into vapor form. Evaporator is known as cooling coil as well in indoor unit. Evaporator and condenser work same like an heat exchanger and are same in construction with combination of copper tubes and fins, but produce different effects.