1. Types of Air Conditioning Systems
1.1 According to the Cooling Method of the Condenser
1. Air cooling: The condenser uses forced air convection for heat exchange, and home air conditioning units are basically of this type. Air-cooled air conditioning units are divided into two types: cooling only type and heat pump type. As the name suggests, the cooling only type can only cool in summer, and the heat pump type can cool in summer and heat in winter.
2. Water cooling: The heat emitted from the condenser is cooled by water flow. In order to save water, the cooling water from the condenser is pumped to the cooling tower by the water pump, and then returns to the condenser after heat exchange with the air. Water cooling AC systems can generally only cool.
1.2 According to the Type of the Compressor
● Piston compressor (reciprocating compressor): The compressor that was commonly used in early ACs is rarely used now because of too many parts, high failure rate, high production cost, poor operating stability, and poor anti-liquid slugging ability of the compressor.
●Scroll compressor: A type of compressor that is currently used frequently. It consists of four major parts: fixed scroll, orbiting scroll, motor, and body. The biggest features of it are few parts, high operating stability, and long service life. It is widely used in small refrigeration units, etc.
●Screw compressor: It is the most frequently used compressor on large air-conditioning units. Its characteristics are few parts, high stability, long service life, and convenient maintenance. Another important point is that the energy efficiency ratio of it is very high. For the same cooling capacity, it saves more than 25% energy than the piston compressor. Screw compressors are divided into single screw and twin screw compressors.
●Centrifugal compressor: The appearance of the centrifugal compressor looks like a large centrifugal water pump, and its structure is also similar to that of the water pump. Centrifugal compressors are often used on air-conditioning units with relatively large power. They are characterized by large cooling capacity per unit, simple structure, reliable performance, and stable operation. Due to its high requirements for production technology, only a few large international companies, such as Trane and York, can produce and sell them on a large scale.
●Rotary compressor (rolling piston compressor): Rotor compressor has its inherent comprehensive advantages in small-capacity air-conditioning systems. Because the vibration of a single rotary compressor is particularly large when the system capacity is large, twin rotary compressors are generally used for larger capacity. Since the two rotors work at the same time, the operating capacity is increased. During the compression process of the compressor, the symmetrical operation of the rotors offset the effect of eccentricity, and make the operation relatively stable and low-noise.
1.3 According to the Type of the Indoor System
Fluorine system: The indoor unit and the outdoor unit are connected by copper pipes in which the refrigerant runs. The refrigerant evaporates and absorbs heat directly in the indoor unit. It is commonly used in home air conditioners and commercial air conditioners. Due to its characteristics, the system cannot be made very large.
Water system: The indoor system and the main unit are connected by water pipes in which the low-temperature water (7℃) runs. The low-temperature water absorbs heat from the indoor unit (fan coil) and flows back to the main unit. It is most widely used in large air-conditioning systems.
Air system: The air is directly processed to the required temperature by the air handling unit, and is sent to the required room through the air duct. The characteristic is that it is easy to bring fresh air into the room. There are certain requirements for the height of the space in installation, and it is less economical.
2. Introduction to the 18 Main Components of the Air Conditioning System
2.1 Compressor
●According to its principle, the compressor can be divided into positive displacement compressor and dynamic compressor.
Positive displacement compressors can be divided into two categories: reciprocating and rotary. The rotary type can be divided into rolling piston type, vane type, single screw type, twin screw type, and scroll type. Dynamic compressors include centrifugal type.
●From the perspective of compressor structure, it can be divided into open type, semi-hermetic type and hermetic type.
The main shaft of the open compressor extends out of the body and is connected to the prime mover through a transmission device (transmission belt or coupling).
The structure of the hermetic compressor is that the motor and the compressor are connected as a whole and installed in the same body, so the shaft seal device can be eliminated, avoiding the possibility of refrigerant leakage.
2.2 Condenser
The function of the condenser is to cool the high-temperature and high-pressure refrigerant superheated vapor discharged from the compressor into liquid or a gas-liquid mixture. The heat released by the refrigerant in the condenser is taken away by the cooling medium (water or air). According to its cooling medium and cooling method, the condenser can be divided into three types: water cooled, air cooled, and water-air cooled.
Water-cooled condenser: The heat of the refrigerant in the condenser is taken away by the cooling water, which can flow through once or be recycled. When recycled, a cooling tower or cooling water pool is required. Water-cooled condensers are divided into shell and tube type, tube-in-tube type, brazed plate type, spiral plate type and other types.
Air-cooled condenser: The heat released by the refrigerant in the condenser is taken away by the air, and the refrigerant condenses in the tube. This type of condenser includes natural convection and forced convection air-cooled condensers.
Water-air cooled condenser: The heat released by the refrigerant in the condenser is taken away by cooling water and air at the same time. When the cooling water sprays and evaporates outside the tube, it absorbs the latent heat of vaporization, cooling and condensing the refrigerant in the tube, so the water consumption is small. This type of condenser includes spray condenser and evaporative condenser.
