2. Introduction to the 18 Main Components of the Central Air Conditioning System
2.3 Evaporator
The function of the evaporator is to use the principle that the liquid low-temperature refrigerant evaporates easily under low pressure, turns into steam and absorbs the heat of the cooled medium to achieve the purpose of refrigeration.
2.4 Throttling Mechanism
It throttles and reduces the pressure of the high-pressure liquid coming out of the condenser, and lets the liquid refrigerant vaporize and absorb heat at low pressure (low temperature). Therefore, it is an important component to maintain high pressure in the condenser and low pressure in the evaporator.
According to the form, the throttling parts can be divided into capillary tubes and expansion valves. Capillary tubes are used in smaller refrigeration equipment. For example, the capillary tube is installed between the condenser and the evaporator in the refrigerator as a type of throttling mechanism.
Expansion valves are used in larger refrigeration equipment. The throttling mechanism used in large and medium-sized devices is the throttling valve. There are three commonly used throttling valves, namely manual expansion valves, float valves and thermal expansion valves. The latter two are automatically adjusted throttling valves. In addition, there are electronic expansion valves.
2.5 Gas-Liquid Separator
The gas-liquid separator is installed at the inlet end of the compressor. It is mainly to prevent the low-pressure and low-temperature vapor returning to the compressor from carrying too many liquid droplets, and prevent liquid refrigerant from entering the compressor cylinder to avoid liquid slugging. The separator also has the functions of filtering, oil return, and liquid storage.
When using the gas-liquid separator, you should pay attention to the following:
1. Keep it as close to the compressor as possible;
2. In the reversing system, the gas-liquid separator should be installed between the reversing valve and the compressor;
3. Correctly install the inlet (from the evaporator) and outlet (to the compressor suction port);
4. It must be installed upward;
5. The connection port of the gas-liquid separator with appropriate size may not be consistent with the suction port of the compressor.
2.6 Fan
The fan is a combination of an AC single-phase or three-phase induction motor and an impeller.
Fans are divided into axial flow fans and centrifugal fans.
Fans include two major types: fixed speed and variable speed.
Fan blades include metal blades, plastic blades, and metal casting blades, etc., with a variety of blade shapes.
2.7 Liquid Receiver
The high-pressure liquid receiver (also called liquid accumulator, suction accumulator) in the refrigeration system is installed between the condenser and the expansion valve. Its functions include several aspects:
Store the condensate of the condenser: avoid excessive accumulation of condensate in the condenser, which will reduce the heat transfer area and affect the heat transfer effect of the condenser.
Adapt to the demand for the supply due to load changes of the evaporator: when the evaporation load increases, the supply also increases, and the liquid stored in the liquid receiver is used to replenish it; when the load decreases, the supply also decreases, and the excess liquid is stored in the liquid receiver.
As a liquid sealing between the high and low pressure sides of the system: because the liquid outlet pipe is inserted below the liquid surface, it can prevent the vapor and non-condensable gas on the high pressure side from entering the low pressure side. At the same time, the liquid receiver also plays a role in filtering and silencing.
There are many forms of liquid receivers, including one-way and two-way, vertical and horizontal.
2.8 Oil-Gas Separator
The oil-gas separator is installed between the compressor and the condenser.
Its working principle is: the discharge gas of the compressor is a mixed gas of refrigerant and lubricating oil. When the oil passes through the larger chamber of the oil separator and slows down, the mist oil will gather on the impact surface. When it gathers into larger oil droplets, it flows to the bottom of the oil separator and returns to the compressor through the oil return device.
2.9 Filter Drier
The function of the filter is to prevent moisture or impurities in the refrigerant from entering the refrigeration system.
When the high-temperature liquid from the condenser enters the expansion valve, the temperature of the liquid will drop significantly, generally below zero. At this time, if there is moisture in the system, since the cross-section of the expansion valve is very small, ice blockage will easily occur, affecting the normal operation of the system.
2.10 Four-Way Reversing Valve
The four-way reversing valve is suitable for heat pump systems such as central air conditioning units and split heat pumps. It is used to switch the flow path of the refrigerant to achieve the purpose of cooling and heating.
2.11 Water Pump
The water pump is a tool used to accelerate the flow of water to achieve the effect of enhancing the heat exchange of water in the heat exchanger.
2.12 Water Flow Switch
The water flow switch is used to control or cut off the flow of fluid in the pipeline. When the fluid flow reaches the set value, the switch automatically cuts off (or connects) the circuit.
2.13 Pressure Controller
The pressure controller is used for pressure control and pressure protection. The unit has low-pressure and high-pressure controllers to control the working range of the system pressure. When the system pressure reaches the set value, the switch automatically cuts off (or connects) the circuit.
2.14 Differential Pressure Controller
The differential pressure controller is used to control the pressure difference. When the pressure difference reaches the set value, the switch automatically cuts off (or connects) the circuit.
2.15 Temperature Controller
The temperature controller is used to control or protect the unit. When the temperature reaches the set value, the switch automatically cuts off (or connects) the circuit.
2.16 Sight Glass
The sight glass is used to indicate:
1. The condition of the refrigerant in the liquid pipeline of the refrigeration unit;
2. The water content in the refrigerant;
3. The flow condition of the lubricating oil from the oil separator in the return oil pipeline. Some sight glasses have an indicator that indicates the water content in the refrigerant by changing its color. (Green means dry, yellow means wet).
2.17 Expansion Tank
Function of expansion tank:
1. The volume of water changes due to temperature rises, and the expansion tank is used to store this part of the expansion water;
2. It plays a role in stabilizing the pressure of the system;
3. It can replenish the system with some water.
2.18 Cooling Tower
The function of the cooling tower is to allow the cooling water carrying heat to exchange heat with the air in the tower, so that the heat is transferred to the air and dissipated into the atmosphere.
