The most common refrigeration method in the market and detailed description

The most common refrigeration method in the market and detailed description

1. Vapor compression refrigeration cycle

　　Using the latent heat generated by the phase change of the working fluid, refrigeration is realized through a closed cycle of compression, condensation, throttling, and evaporation. It is the most widely used refrigeration cycle.

　　 Compressor: Absorb the refrigerant vapor in the evaporator, compress it to the condensing pressure, and then discharge it to the condenser;

　　Condenser: condenses the high-pressure refrigerant vapor from the compressor into a liquid. During the condensation process, the heat released by the refrigerant vapor is taken away by cooling water or air;

　　 Throttle valve: When the refrigerant liquid passes through the throttle valve, the pressure is reduced from the condensing pressure to the evaporation pressure, and part of the liquid flashes into vapor;

　　 Evaporator: The throttled refrigerant liquid evaporates into a gas in the evaporator while absorbing the heat of the object to be cooled. The object to be cooled can be liquid refrigerant or air.

　　1, screw compression refrigerator

Advantages: small size and light weight; simple structure, fewer wearing parts, high reliability; small torque changes, less vibration, and stable operation; can withstand a certain amount of liquid shock; energy can be steplessly adjusted; high compression efficiency, rotor Low exhaust temperature after fuel injection, good air tightness;

　　 Disadvantages: The surface of the rotor parts is curved, and the processing accuracy is high; a huge oil separator is required to separate the oil sprayed into the machine, and the auxiliary equipment is complicated.

　　2, centrifugal compression refrigerator

Advantages: high performance coefficient, large cooling capacity; light weight and small volume per unit power unit; easy to achieve multi-stage compression and throttling; high degree of automation; automatic stepless adjustment of cooling capacity through imported guide vanes or frequency conversion, The adjustment range is wide; the amount of lubricating oil mixed with the refrigerant in the refrigerator is small, and the heat transfer effect of the heat exchanger is small.

　　 Disadvantages: high speed, must be suitable for large flow occasions, not suitable for small refrigeration capacity; the inherent low-load surge phenomenon of centrifugal compression refrigerators can not be effectively solved. 　　3, piston compression refrigerator 　　Advantages: the earliest model; high thermal efficiency, high speed; multi-cylinder, adjustable energy; suitable for multiple refrigerants, easy to manufacture, low price, easy to operate and manage 　　 Disadvantages: complex structure, many vulnerable parts, short maintenance period; large inertia of reciprocating motion, discontinuous air delivery, pulsation of exhaust pressure, and greater equipment vibration. Applicable cooling capacity is small 　　4, scroll compression refrigerator 　　 Compared with the reciprocating piston type, it has the characteristics of high efficiency, low noise, fewer parts, light weight, small size, energy saving, and low vibration. 　　 5. Ice storage Advantages: The system can realize peak shifting and valley filling, combined with electricity price differences in different periods, and can save a lot of operating costs; especially for projects where air conditioning loads appear during the day and do not require cooling at night, and the electricity price difference is large, its advantages are even more obvious. 　　 Disadvantages: increase initial investment; occupy a large area of ​​the computer room; complicated control. 　　Commonly used ice storage methods: refrigerant coil storage ice, completely frozen ice storage, container ice storage 　　6, water storage 　　Advantages: Can use conventional chillers or absorption chillers to operate in an economical state; suitable for the transformation and expansion of conventional systems; low technical requirements, convenient maintenance, can use fire-fighting pools and original water storage facilities for water storage 　　 Disadvantages: When the cold storage capacity is less than 600*104Kcal/H or the cold storage volume is less than 760m3, the economics of water storage is not reflected; it takes up a large space and is complicated to control 　　 Commonly used water cold storage methods: natural stratified cold storage, multi-tank cold storage, labyrinth cold storage, diaphragm cold storage 　　7. Heat pump: 　　The heat pump is a kind of equipment that has developed and applied rapidly in recent years. A heat pump is a device for cooling in summer and heating in winter. Due to its advantages in energy saving and environmental protection, it soon became an important cold and heat source equipment for central air conditioning. 　　 There are many types of heat pumps, such as: air source heat pump, water source heat pump, ground source heat pump, water loop heat pump, gas heat pump, etc. 　　7.1, air source heat pump (air-cooled heat pump) 　　 Air source heat pump (also known as air-cooled heat pump) is a kind of electric drive heating and cooling equipment that does not need water source and only exchanges heat with air. Its function is to extract heat at low temperature and release heat to the high temperature part. It is a kind of heat (or cold) exchange equipment. The electricity consumed is not used to generate heat, but to overcome Mechanical resistance, so its energy efficiency ratio (COP coefficient) is higher, and the COP can reach more than 1:4.5. It is an energy-efficient product. 　　 The atmosphere is the exothermic side in summer, and the atmosphere is the endothermic side in winter. 　　The main applicable cities in China: Shanghai, Nanjing, Wuhan, Chongqing, Changsha, Hefei, Nanchang and other places. With the improvement of the unit's own performance, it has been applied in northern areas such as Beijing and Tianjin. In the north, heat pump units are selected based on the best energy balance point, which are mainly used in hotels, office buildings, etc., while shopping malls, theaters, etc. are not applicable. 　　7.2, water source heat pump 　　 water source heat pump is a heat pump type integral water-air air conditioning device that can perform a cooling/heating cycle with water as the heat source. It uses water as the heat source during heating and water as the exhaust heat source during cooling. 　　Water source heat pumps can be divided into three categories: groundwater heat pump systems, surface water heat pump systems, and closed loop surface water heat pump systems; 　　Advantages: the quality of water has large heat capacity, good heat transfer performance, less water required to transfer a certain amount of heat, and small heat exchanger size; there is no problem of frost on the surface of the evaporator; Disadvantages: limited by area, it needs to be in an area where the temperature is relatively stable and the water volume is easy to obtain; the water system is complicated; it also needs to consume the power of the water pump; if the water hardness is large, it will cause the surface of the heat exchanger to foul and improve the heat transfer performance Decrease; if it contains chloride ions, it will also cause corrosion of the equipment; before using the water source heat pump, a comprehensive assessment of geology, hydrology, and water quality must be carried out. 　　7.3, ground source heat pump Ground source heat pump, also known as ground-coupled heat pump, ground-source heat pump, underground heat exchanger, geothermal heat pump, etc., is a new air-conditioning cold and heat source method. Ground-source heat pumps pass from shallow soil through vertical and horizontal buried pipes. The pipe or the serpentine buried pipe takes heat and discharges heat to it. 　　Advantages: No need to drill wells to extract groundwater, but directly exchange heat from the soil; it is not affected by geological conditions, the amount of well water, ground subsidence and groundwater pollution, etc. 　　 Disadvantages: large area required for heat exchange soil; difficult construction; difficult maintenance of concealed projects and high maintenance costs; such as unbalanced heating and cooling in winter and summer, it is easy to form a "heat island" problem 　　7.4, water ring heat pump 　　 water loop heat pump system uses a circulating water path as the heating source and exhaust heat source. When the temperature of the water in the loop exceeds a certain value, the water in the loop will release heat to the atmosphere through the cooling tower. 　　 When the temperature of the water in the loop is lower than a certain value, a heating device is usually used to heat the circulating water. In buildings equipped with air conditioners with multiple water ring heat pumps, some operate in cooling mode, and some operate in heating mode, and the function of the control system is to keep the circulating water temperature in the loop within a certain range. 　　7.5, gas heat pump 　　 All types of heat pumps above are electric heat pumps, and the driving energy of gas heat pumps is gas. The working principle is a gas engine driven compression 　　The machine works, compared with the above types of heat pumps, it runs more economically and has the characteristics of good heating effect in winter. 　　 2. Absorption refrigeration cycle 　　A refrigeration solution is composed of an absorbent and a working fluid, driven by thermal energy, through a closed cycle of generation, condensation, evaporation, and absorption. At present, the most common z* is a water-lithium bromide absorption refrigerator, which is widely used in air conditioning projects. 　　 Evaporator: The refrigerant-water evaporates in it and absorbs the heat of the refrigerant. 　　 Absorber: In the absorber, the concentrated absorption liquid absorbs the vapor generated in the evaporator, so that the evaporator evaporates continuously. 　　 Generator: Heat the dilute absorbing liquid after absorbing steam to increase the concentration of the absorbing liquid. 　　Condenser: The steam evaporated from the generator is condensed into a liquid state in the condenser, and this part of the steam is added to the evaporator. 　　1, direct-fired lithium bromide absorption chiller and warm water unit Advantages: Energy is the fuel, which can use oil, natural gas, city gas and other fuels; dual-purpose cooling and heating, which can realize summer cooling and winter heating; based on the primary energy source, it emits more harmful gases than centrifuges, screw machines, etc. Less equipment, environmental protection; power saving, environmental protection; quiet operation, safe use; wide cooling adjustment range, strong adaptability to changes in the external environment 　　 Disadvantages: high air-tightness requirements; large volume and large floor space compared to electric refrigerators; 　　2, steam type (hot water type) lithium bromide absorption chiller Advantages: Use waste heat steam and waste heat for cooling to realize comprehensive utilization of energy; realize energy balance in winter and summer, realize the use of rich steam in summer, and improve energy utilization; save power consumption, environmental protection; quiet operation and safe use; cooling adjustment range Wide, adaptable to changes in the external environment 　　 Disadvantages: high air-tightness requirements; large volume and large floor space compared to electric refrigerators; 　　3, flue gas bromine chiller, ammonia absorption chiller and absorption heat pump 　　 3. Commercial air conditioning system 　　Commercial air-conditioning is an emerging air-conditioning method, which is generally used in commercial buildings, office buildings and apartment buildings. Generally, there is no refrigerating machine room. Instead, the refrigeration host and condenser are installed in a box and placed outdoors (that is, outdoor unit), and the evaporator is directly installed indoors (ie, indoor unit). 　　 There are many classification methods for commercial air conditioners, which can be based on function or control method Major manufacturers: Daikin (VRV), McQuay (MCC), Hitachi Hisense (RAS-FS), Midea (MDV), Gree (GMV), Little Swan (SMV-M), Haier (C-MRV), LG (Frequency conversion Multi) etc. VRV system: The full name of VRV air conditioning system is Varied Refrigerant Volume, or VRV for short. It adjusts the cooling capacity by changing the refrigerant flow rate. It is a refrigerant type air conditioning system that uses refrigerant as the transport medium and the outdoor host exchanges heat from the outdoor side. It is composed of air cooler, compressor and other refrigeration accessories, and the end device is an indoor unit composed of direct evaporative heat exchanger and fan. One outdoor unit can deliver refrigerant liquid to several indoor units through pipelines. By controlling the refrigerant circulation of the compressor and the refrigerant flow into the indoor heat exchangers, the indoor cooling and heating load requirements can be met in a timely manner. The VRV system has many advantages such as energy saving, comfort, and stable operation, and each room can be independently adjusted , Can meet the needs of different air conditioning loads in different rooms. However, the control of the system is complicated, and the requirements for pipe material, manufacturing process, field welding, etc. are very high, and its initial investment is relatively high.