Is central air conditioning a brand? What does "central air conditioning" mean? Often confused with air conditioning brands such as Haier and Gree. Please advise if you know, thank you.

[Edit this paragraph] Central air conditioning

The central air conditioning system consists of cold and heat source system and air conditioning system. The refrigeration system provides the required refrigeration capacity for the air conditioning system to offset the cold load of the indoor environment; The heating system provides heat for the air conditioning system to offset the heat load of the indoor environment. Refrigeration system is an important part of central air-conditioning system, and its type, operation mode and structural form directly affect the economy, efficiency and rationality of central air-conditioning system.

[Edit this paragraph] Classification of refrigeration systems

Air conditioning refrigeration technology belongs to the general refrigeration category, and mainly adopts liquid gasification refrigeration mode. (It is mainly used to absorb the specific latent heat in the process of liquid gasification, and the boiling point of liquid is different with different pressure. The lower the pressure, the lower the boiling point. According to the different heat transfer modes from low-temperature objects to high-temperature objects, it can be divided into vapor compression refrigeration and absorption refrigeration.

Vapor compression refrigeration

Refrigeration Principle Gaseous refrigerant (such as Freon) is compressed into high-temperature and high-pressure gas by a compressor, and then enters a condenser to exchange heat with water (air) at the same pressure, and becomes a low-temperature and high-pressure liquid. After the liquid working medium passes through the drying filter to remove moisture and impurities, it enters the expansion valve for throttling and decompression to become a low-temperature and low-pressure liquid working medium, which is gasified in the evaporator. The latent heat of gasification is absorbed in the process of liquid gasification, and the saturation temperature (boiling point) varies with the liquid pressure. The lower the pressure, the lower the saturation temperature. For example, 1kg of water needs to absorb 2488.7KJ of heat when it is gasified at an absolute pressure of 0.00087MPa and a saturation temperature of 5℃. When 1kg ammonia is gasified at 1 standard atmospheric pressure (0. 10 133MPa), it needs to absorb the heat of 1369.59KJ, and the temperature can reach -33.33℃. Therefore, as long as certain low-pressure conditions are created, the required low temperature can be obtained through the gasification of liquid. According to this principle, the gasification process absorbs the heat of frozen water, which reduces the temperature of frozen water (usually 7℃). The refrigerant absorbs heat in the evaporator, and the temperature rises to become superheated steam, which enters the compressor for repeated circulation. The vapor compression refrigeration system is mainly divided into water-cooled and air-cooled systems, as shown in Figure 2- 1 and Figure 2. Compressor refrigeration compressor is an important equipment of vapor compression refrigeration device. There are many forms of refrigeration compressors, which can be divided into two categories according to different working principles: positive displacement refrigeration compressors and centrifugal refrigeration compressors. At present, the commonly used compressors mainly include piston compressor, scroll compressor, screw compressor and centrifugal compressor, as shown in Figure 2-3. The positive displacement refrigeration compressor compresses the periodically sucked quantitative gas by changing the volume of the working chamber. Commonly used positive displacement refrigeration compressors include reciprocating piston refrigeration compressors and rotary refrigeration compressors. Centrifugal refrigeration compressor continuously compresses the sucked gas by centrifugal force. This kind of compressor has high rotating speed and large refrigerating capacity. At present, the refrigeration capacity of Freon centrifugal refrigeration compressor for air conditioning abroad is as high as 30000kw. Refrigerant Refrigerant Refrigerant is the working medium of refrigeration cycle in refrigeration device. Its working principle is that the refrigerant absorbs the heat of the cooled substance in the evaporator and evaporates, and the absorbed heat is transferred to the surrounding air or water in the condenser, and then cooled into liquid, and so on, so as to achieve the refrigeration effect in the form of state change. Commonly used refrigerants are ammonia (R7 17) and freon (R22, R 134a, R404A, etc. Coolant Coolant is an intermediate substance, such as common air conditioning chilled water, which is cooled in an evaporator and then transported for a long distance to cool the cooled object. At present, the commonly used coolant is water. When it is required to be lower than 0℃, it can only be used under the condition of higher than 0℃. Generally, brine, such as aqueous solution of sodium chloride or calcium chloride or aqueous solution of organic compounds such as ethylene glycol and propylene glycol, is used. Absorption refrigeration absorption refrigeration is a form of liquid gasification. Like vapor compression refrigeration, it uses liquid refrigerant to vaporize at low temperature and low pressure to achieve the purpose of refrigeration. The difference is that vapor compression refrigeration transfers heat from a low-temperature object to a high-temperature object by consuming mechanical work (or electric energy), while absorption refrigeration completes this non-spontaneous process by consuming heat energy. Refrigeration schematic diagram Figure 2.4 shows that the absorption refrigerator is mainly composed of four exchange devices: generator, condenser, evaporator and absorber, forming two circulation loops: refrigerant circulation and absorbent circulation. The left half is a refrigerant cycle, which belongs to reverse cycle and consists of condenser, throttling device and evaporator. The high-pressure gaseous refrigerant releases heat to the cooling medium in the condenser, condenses into liquid state, and then cools under reduced pressure through the throttling device and enters the evaporator; In the evaporator, the liquid is gasified into low-pressure gas, and at the same time, the heat of the cooled medium is absorbed, resulting in refrigeration effect. These processes are exactly the same as vapor compression refrigeration. The right half is absorbent circulation (dotted line in the figure), which belongs to positive circulation and mainly consists of absorber, generator and solution pump, which is equivalent to the compressor of vapor compression refrigeration. In the absorber, the low-pressure gaseous refrigerant generated by the evaporator is continuously absorbed by the liquid absorbent to achieve the purpose of maintaining the low pressure in the evaporator; The refrigerant-absorbent solution formed by the absorbent absorbing refrigerant vapor enters the generator after being boosted by the solution pump; The solution is heated and boiled in the generator, and the low-boiling refrigerant is gasified in the generator to form high-pressure gaseous refrigerant, which enters the condenser for liquefaction, and the remaining absorbent solution returns to the absorber to absorb the low-pressure gaseous refrigerant again. The absorbent in absorption refrigerator is usually not a single substance, but a binary solution. The only difference between absorbent solution and refrigerant-absorbent solution is that the former contains less refrigerant with lower boiling point than the latter, or the former contains lower refrigerant concentration than the latter. Binary solutions usually include lithium bromide aqueous solution, ammonia aqueous solution, etc. The choice of central air conditioning refrigeration system should be determined according to various objective conditions such as load, energy supply mode and convenience. Among them, piston refrigeration compressors are mostly medium-sized (standard refrigeration capacity is 60~600KW) and small-sized (below 60KW), but they are rarely used at present because of their high noise and low efficiency. At present, scroll refrigeration compressors are mainly used in small refrigeration systems, and are widely used in small systems such as household air conditioners and commercial VRV. Screw machine has a series of unique advantages, such as simple structure, high reliability, convenient operation and maintenance, mature technology and so on, and has been widely used in air conditioning. Centrifugal compressor has the advantages of simple and compact structure, few moving parts, reliable operation, durability and low operating cost. Generally, it is suitable for refrigeration systems over 500RT, and can realize stepless regulation, so that the unit load can work in the range of 30%~ 100%. Electric refrigeration is usually used, and absorption refrigeration can be used in areas rich in natural gas or coal resources.

[Edit this paragraph] Selection of refrigeration system

The choice of central air conditioning refrigeration system should be determined according to various objective conditions such as load, energy supply mode and convenience. Among them, piston refrigeration compressors are mostly medium-sized (standard refrigeration capacity is 60~600KW) and small-sized (below 60KW), but they are rarely used at present because of their high noise and low efficiency. At present, scroll refrigeration compressors are mainly used in small refrigeration systems, and are widely used in small systems such as household air conditioners and commercial VRV. Screw machine has a series of unique advantages, such as simple structure, high reliability, convenient operation and maintenance, mature technology and so on, and has been widely used in air conditioning. Centrifugal compressor has the advantages of simple and compact structure, few moving parts, reliable operation, durability and low operating cost. Generally, it is suitable for refrigeration systems over 500RT, and can realize stepless regulation, so that the unit load can work in the range of 30%~ 100%. Electric refrigeration is usually used, and absorption refrigeration can be used in areas rich in natural gas or coal resources.

[Edit this paragraph] Common terms of central air conditioning

1. Comfort air conditioning: make the air-conditioned room meet the requirements of people's life, and control the air parameters of the room according to the comfort requirements of human body. 2. Process air conditioning; Also known as constant temperature and humidity air conditioning, it is to control indoor air temperature, humidity, airflow speed, cleanliness and other parameters within a certain range to meet the requirements of production technology. 3. Refrigeration capacity: the heat absorbed by the refrigerant on the low-pressure side of the evaporator in unit time when the air conditioner is in refrigeration operation. Commonly used units are w or KW. 4. Heat pump heating; When the air conditioner is operated with a heat pump (the auxiliary electric heater of the heat pump should be operated at the same time), the heat delivered to a closed space, room or area in a unit time. 5. Performance coefficient: The ratio of the amount of refrigeration (heat) generated in the refrigeration (heat) cycle to the power consumed by refrigeration (heat) is the performance coefficient. When cooling, it is called energy efficiency ratio, which is expressed by EER; When heating, it is called the performance coefficient and expressed by COP. 6. Refrigerant: Refrigerant is the working medium to complete the refrigeration cycle in the refrigeration system. The refrigerant absorbs the heat of the cooled object and evaporates in the evaporator. In the condenser, heat is transferred to the surrounding air or water and condensed into liquid. The refrigerator achieves the purpose of refrigeration by changing the state of refrigerant. 7. Coolant: Coolant refers to the intermediate medium used to transfer cold energy in indirect refrigeration system. After being cooled by the refrigerant in the evaporator, the refrigerant is sent to the cooling equipment for cooling, absorbs the heat of the cooled object or environment, and then returns to the evaporator to be cooled again by the refrigerant, and so on. So as to achieve the purpose of continuous refrigeration. 8. Fan coil unit: It is a common heat exchange equipment in central air-conditioning system, consisting of finned tubes and fans. When the coolant flows through the fan coil (inside the tube), it exchanges heat with the air inside the tube to cool the air. Fan coil unit belongs to air-cooled equipment. 9. Water-cooled chiller: Water-cooled chiller belongs to the refrigeration unit in the central air-conditioning system, and its refrigerant is water, which is called chiller. The cooling of condenser is realized by the heat exchange of water at room temperature, so it is called water-cooled unit. The condenser of air-cooled unit is called air-cooled unit, which is cooled by forced ventilation and heat exchange with indoor air. 10, cooling tower; Special equipment for air cooling water is generally installed at the top of buildings. In refrigeration, electric power, chemical industry and many other industries. The hot cooling water discharged from the condenser and other equipment is cooled by the cooling tower and then recycled. 1 1, VRV system: short for variable refrigerant flow system, namely variable refrigerant flow system. It is in the form of a group of outdoor machines, consisting of functional machines, constant speed machines and frequency converters. By connecting outdoor units in parallel, the refrigeration pipeline is integrated into a pipeline system. According to the capacity matching of indoor units, the appropriate capacity of indoor units can be conveniently selected between 122.5 ~ 1.5 kw, that is, a group of outdoor units can connect up to 30 indoor units. Indoor units include ceiling embedded, wall mounted, floor mounted, etc. Different indoor independent machines can be connected to the refrigeration circuit and can be controlled independently. The minimum capacity of the indoor unit is 0.6KW and the maximum capacity is 3.75KW. The capacity of the indoor unit can be adjusted within the range of 50% to 130% of the outdoor unit capacity. 12. Modular machine: It is developed on the basis of VRV system. 1985, invented by Jiefeng Group of Australia, applied for specialization. It changes the traditional Freon pipeline into a waterway system, combines the indoor unit and outdoor unit into a refrigeration unit, and changes the indoor unit into a fan coil unit. Using the heat exchange of cooling water to realize the refrigeration process, the modular machine is named because it can automatically adjust the number of starting units according to the requirements of cooling load and realize flexible combination. 13. Piston cooler; Piston refrigerator is an integrated refrigeration device that compactly assembles the piston refrigeration compressor, auxiliary equipment and accessories needed to realize refrigeration cycle, and is specially used for air conditioning and refrigeration purposes. The refrigeration capacity of a single piston chiller is between 60 and 900 kW, which is suitable for medium-sized and non-engineering projects. 14. Screw chiller; Screw chiller is a large and medium-sized refrigeration equipment that provides chilled water. It is often used for air conditioning in national defense scientific research, energy development, transportation, hotels, restaurants, light industry, textiles and other departments, as well as chilled water for water conservancy and electric power engineering. Screw chiller is a complete refrigeration system consisting of screw refrigeration compressor unit, condenser, evaporator, automatic control elements and instruments. It has the advantages of compact structure, small volume, light weight, small floor space, convenient operation and maintenance, stable operation and so on, so it has been widely used. Its refrigeration capacity ranges from 150 to 2200KW, which is suitable for medium and large projects. 15. Centrifugal water chiller; It is an integral water chiller composed of centrifugal refrigeration compressor, evaporator, condenser, throttle control device and electric meter. The cooling capacity of a single machine ranges from 700 to 4200KW. It is suitable for large and super-large projects. 16. lithium bromide absorption refrigerator: using heat energy as power, water as refrigerant and lithium bromide solution as absorbent, refrigerant water above 0℃ is prepared, which can be used as cold source for air conditioning or production process. Lithium bromide absorption type is driven by thermal energy, and there are three common types: direct combustion type, steam type and hot water type. Its cooling capacity ranges from 230 to 5800KW, which is suitable for medium-sized, large-scale and extra-large projects.

[Edit this paragraph] Home central air conditioning

Central air conditioning is an air conditioner in which a host computer connects multiple terminals through air pipes or hot and cold water pipes to control different rooms and realize indoor air conditioning. Using duct air supply mode, a host computer can control many different rooms and introduce fresh air, which can effectively improve indoor air quality and prevent the occurrence of air conditioning diseases. The most prominent feature of home central air conditioning is the comfortable living environment. Secondly, from the aesthetic point of view and the best use of space, the use of home central air conditioning makes indoor decoration more flexible and easier to achieve various decorative effects. Even if you don't like the original decoration and redecorate it, the original central air conditioning system can be in harmony with the new decoration as long as it is slightly modified. Therefore, domestic central air conditioning is called a one-step choice that never lags behind. Household central air conditioning (or household central air conditioning, single-regulation central air conditioning) refers to air conditioning that generates cold (hot) source by outdoor machine and then supplies cold (hot) to each room. Which belongs to a (small) commercial air conditioner. Household central air conditioning is divided into air system and water system. The air system consists of outdoor unit, indoor main unit, air supply pipeline, air outlets in each room and regulating valves. The water system consists of outdoor unit, water pipeline, circulating water pump and the end of each room (fan coil unit, surface mounted, etc.). ). The characteristics of home central air conditioning are: 1 The whole family is in a comfortable state, which avoids the human discomfort caused by other split machines; 2. The decoration is good, and there is no exposed pipeline in coordination with the decoration; 3 simple operation, automatic operation and no maintenance; 4 according to the orientation and function of each room, the air supply (heat) can be increased or decreased; 5 can increase fresh air and humidification, and keep the indoor air fresh and hygienic. The limitations of home central air conditioning are: 1 layout: design and installation should be combined with decoration to achieve good comfort and decorative effect; 2 power requirements: the power load is large. Old houses should consider whether the circuit load is enough. Classification of main components: 1. According to the medium used to bear indoor heat and humidity load, it can be divided into: 1. All-air system II. Total water system 3. Air-water system. Coolant system 2. According to the concentration of air treatment equipment, it can be divided into: 1. Centralized 2. Semi-centralized 3. According to the source of treated air, it can be divided into: 1.