Fan coil air conditioning system
A fan coil air conditioning system consists of one or more fan coil units and a cold and heat source supply system. The fan coil unit consists of a fan, a coil and a filter. As the terminal device of the air conditioning system, it is installed in each air conditioning room in a decentralized manner, and can treat the air independently, while the cold and hot water required for the air treatment is It is centrally prepared by the air-conditioning room and supplied to each fan coil unit through the water supply system.
The application of fan coil units in air conditioning projects is mostly combined with the fresh air system that has been treated separately. The structure of the fan coil unit is composed of coil units (that is, surface coolers, generally 2-3 rows) and fans (forward multi-blade centrifugal fans or cross-flow fans), and the air volume is in the range of 250-2500m3/h.
The composition of the fan coil unit: the fan coil unit is composed of a fan, a motor, a coil, an air filter, a room temperature adjustment device and a box.
The working principle of the fan coil unit is: the fan in the unit continuously circulates the air in the room where it is located, so that it is continuously cooled or heated through the coils supplying cold or hot water to maintain the temperature of the room. Among them, the function of the air filter is to filter the dust in the indoor circulating air, improve the sanitary conditions of the room, and at the same time, it can protect the coil from being blocked by dust, and ensure the air volume and heat exchange effect.
The main advantages of the fan coil air conditioning system are: less noise, suitable for hotel rooms; superiority of individual control; easy adjustment and control of system partitions; small size of the fan coil itself, convenient layout and installation.
The main disadvantages of the fan coil air conditioning system are: because the unit is installed indoors, it needs to cooperate effectively with construction and other types of work; the unit is relatively scattered, and its maintenance workload is large; the problem of fresh air must be solved; the static pressure of the fan is small , can not use high-performance filters, making the indoor air cleanliness is not high.
Features of fan coil unit: There are two types of fan coil unit: vertical type and horizontal type. There are two types of installation methods: concealed type and exposed type. From the perspective of the structure of the fan coil unit, its main features are: centrifugal multi-blade fans are often used, the diameter of the impeller is generally below 150mm, the static pressure is below 100Pa, the impeller is made of galvanized steel sheet, aluminum sheet or ABS engineering plastics; motor Generally, capacitive type is used, and the speed of the motor can be changed through the speed control switch to change the air volume of the fan during operation. The ratio of high, medium and low gears is about 1:0.75:0.5; It is made of aluminum sheet. Generally, the outer diameter of the copper pipe is 10mm, the wall thickness of the pipe is 0.35mm, the thickness of the aluminum sheet is 0.12~0.15mm, and the distance between the sheets is 2~2.3mm. The number of rows of coils is two or three; the filter material of the air filter is made of coarse-pored foam plastic, fiber fabric or nylon braid. In practical projects, fan coil units are widely used in guest rooms, offices and other buildings due to their advantages of control flexibility and low noise. The fan coil unit mainly provides indoor heat and humidity load, and the fresh air is centrally processed by other equipment.
The components of the fan coil air conditioning unit are described as follows:
(1) Fan The fan is one of the main components in the fan coil air conditioner, which plays the role of conveying air. At the same time, it is the driving force that causes forced convection heat transfer in the coil and enhances the heat transfer capacity. The fan used in the fan coil unit has two types of multi-blade centrifugal fan and cross-flow fan. (2) Coil coil is a heat exchanger and an important part of the fan coil unit. Nowadays, copper tubes are mostly used in series with aluminum sheets, and the tubes are mechanically expanded to eliminate contact thermal resistance. There are also made of rolled tubes, generally two or three rows of tubes. (3) Air filter The filter material is made of coarse-pored foam plastic or fiber fabric, which can be cleaned or replaced.
(4) Fan motors generally use capacitive circuits and oil-impregnated bearings, and do not usually refuel. Note that if it is not an oil-impregnated bearing, it should be refueled regularly. It usually has a three-speed speed change to adjust the air volume, and the air volume adjustment range is about 50%.
(5) Box The concealed box is usually made of galvanized iron sheet. The surface of the exposed box should be sprayed with paint or plastic, and the iron plate should be treated with pickling, phosphating, etc. before spraying. There must be good thermal insulation measures inside the box, so that the unit can maintain a good thermal insulation effect when running in wet conditions, so as to avoid condensation on the shell.
Single and double coils
The general air-conditioning water system adopts double pipes, that is, the hot water supply in winter and the cold water supply in summer are all carried out in the same system. The fan coil corresponding to this water system is in the form of a single coil. Single coils are available in two rows and three rows for cooling in summer and heating in winter. The advantage of this air conditioning system is that the system is simple and the initial investment is low; the disadvantage is that in the transitional season, when some areas need heating and some areas need cooling, it cannot meet the requirements.
In the four-pipe air-conditioning system, cold water and hot water are transported by two pipes respectively, and the return pipe is also one for cold water and one for hot water. The fan coil unit corresponding to such an air conditioning system is in the form of a double coil unit, which has two coil units, a cold coil unit and a hot coil unit. This kind of system can supply hot and cold water at the same time throughout the year, flexibly adjust the room temperature, and ensure the temperature of indoor air; however, the initial investment is large, the area of the pipe well occupied is large, the water pipe line is complicated, and there are possible cold, Disadvantages of thermal offset. If air is used for air, if air accumulates in the coil, it will affect the heat transfer effect at light level, and it may stop flowing and lose its function in severe case. The return air enters the unit from the bottom, and some are arranged in the lower half of the panel. The air outlet can be opened upwards or sideways, and the direction of the air outlet is also changed.