Last Updated on November 2, 2021 by Shawn Lee
I.Definition of Air Conditioning:
Air conditioning is the abbreviation of air conditioning, which uses equipment and technology to adjust the temperature, humidity, cleanliness and airflow speed of indoor air, so as to meet people’s comfortable requirements for the environment or production process requirements for the environment.
Comfort air conditioner: it mainly meets the comfort requirements of human beings or other creatures;
Process air conditioner: air conditioner mainly used to meet the operation requirements of process production process and equipment Refrigeration capacity: the heat removed from the room by the air conditioner under nominal refrigeration condition in unit time.
Heating capacity: the heat released into the room by the air conditioner under nominal heating conditions per unit time.
II.The air-cooled cold water system
Air-cooled cold water system is widely used, and the radiator is built-in fan, which mainly consists of refrigerant circulation system, water circulation system and electrical automatic control system. The transmission medium of the unit is usually water. It produces air-conditioning cold water through outdoor main engine, which is delivered to indoor terminal devices by pipeline system, where the cold water exchanges heat with indoor air, thus eliminating room air conditioning load.
III.Multi-connected system (VRV)
Variable refrigerant flow is a one-to-many air conditioning system, which is suitable for office places. One outdoor unit of VRV system can deliver refrigerant liquid to several indoor units through pipelines. By controlling the refrigerant circulation of the compressor and the refrigerant flow into each indoor heat exchanger, the requirements of indoor cold and heat loads can be timely met. VRV system has many advantages such as energy saving, comfort and stable operation, and each room can be independently adjusted to meet the requirements of different air conditioning loads in different rooms.
IV. Water chiller (centrifugal)
Centrifugal chillers use electricity as the power source, and Freon refrigerant evaporates and absorbs the heat of coolant water in the evaporator for refrigeration. Freon wet steam after evaporation and heat absorption is compressed by the compressor into high-temperature and high-pressure gas, which is condensed by the water-cooled condenser and then becomes liquid, which is throttled by the expansion valve and enters the evaporator for recycling. So as to prepare 7-12 DEG C frozen water for air conditioning at the end of the air conditioner.
V. Chillers (screw type)
The compressor adopts screw type, and the refrigerant in the state of gas from the evaporator of the unit; After adiabatic compression by compressor, it becomes high temperature and high pressure state. Compressed gas refrigerant is cooled and condensed under equal pressure in a condenser, and then changes into liquid refrigerant after condensation, and then expands to low pressure through a throttle valve to become a gas-liquid mixture. Among them, the liquid refrigerant at low temperature and low pressure absorbs the heat of the cooled material in the evaporator and becomes the gaseous refrigerant again.
VI. Main equipment and principle of air conditioning system for water-cooled units
- Refrigeration host;
- Cryogenic pump;
- Cooling pump;
- Expansion tank;
- Terminal equipment;
- Cooling tower.
Working principle: After the air conditioner is powered on, the low-pressure steam of refrigerant in the refrigeration system is sucked by the compressor and compressed into high-pressure steam, which is then discharged to the condenser. At the same time, the cooling water passes through the condenser to take away the heat released by the refrigerant, so that the high-pressure refrigerant vapor condenses into high-pressure liquid. After passing through the filter and throttling mechanism, the high-pressure liquid is sprayed into the evaporator and evaporated at the corresponding low pressure. At the same time, the chilled water enters the evaporator for heat exchange, thus continuously circulating and flowing to achieve the purpose of cooling.
Chilled water pump: the chilled water cooled by the refrigeration main engine is sent to the central air conditioning terminal (fan coil, air cabinet) and other components for heat exchange to cool the environment, and the exchanged chilled water is returned to the refrigeration main engine for continuous circulation.
Cooling water pump: the cooling water cooled by the cooling tower is sent to the condenser of central air conditioner through the transmission pipeline for heat exchange, which cools the condenser, and the exchanged cooling water returns to the cooling tower for heat dissipation, thus continuously circulating.
Expansion tank: it is an important component of central air-conditioning waterway system, and its function is to contain and compensate water. Generally installed at the highest point of the end system.
Air-conditioning terminal: Generally, there are fans and surface coolers. Fans are used to circulate indoor air. The air exchanges heat with the surface cooler (chilled water) to lower the air temperature and raise the water temperature in the surface cooler to complete the refrigeration process.
Air conditioning box: there are suspended ceiling, horizontal and vertical units.
Cooling tower: the cooling water is pressurized to the water distributor of the cooling tower by a water pump, and the water is evenly spread on the filler through the small holes on the water distributor. The air enters the tower through the bottom air inlet network under the action of a fan. When the hot water flows through the filler surface, it forms a water film to exchange heat with the air. The hot air with high humidity and high Han value is pumped out from the top, and the cooled water drops into the bottom basin and flows into the host through the outlet pipe.
VII.Turn-on and turn-off process of central air conditioner
Check whether the three-phase power supply of the main air conditioner, cooling, chilled water pump and cooling tower is normal (whether there is no phase, whether the voltage is under-voltage or over-pressure).
Check whether the water level of cooling tower and automatic water replenishing valve are normal.
Check whether the manual butterfly of main engine, chilled water pump, cooling water pump and cooling tower are open, and check the opening indication of valves.
Check whether the oil level and oil temperature of the main engine are normal and the normal range of oil temperature is 60℃~70℃.
Press the “Shutdown” soft key for 1S or toggle the switch to the stop position for normal shutdown, and the compressor will be shut down according to the normal shutdown procedure. After shutdown, the cooling and chilled water pumps should run for at least 10 minutes before stopping the pumps and corresponding valves. Under normal circumstances, emergency shutdown is not allowed.