Year1
- 型号：
- 齐全
- 规格：
- 标准
- 材质：
- 镀锌板
Fresh air unit control includes supply air temperature control, supply air relative humidity control, antifreeze control, concentration control and various interlocking contents. If the fresh air unit is to be considered to bear the indoor load, such as a DC unit, it must also control the indoor temperature or indoor relative humidity.
Supply air temperature control
Supply air temperature control is the designated outlet air temperature control. Its applicable condition is usually that the fresh air unit is used to meet indoor hygiene requirements rather than bear indoor load. Therefore, the supply air temperature is maintained at a constant value during the entire control time. Since the indoor requirements are different in winter and summer, the supply air temperature in winter and summer should have different requirements. That is to say, when the fresh air unit has fixed supply air temperature control, there are two control values throughout the year, the winter control value and the summer control value. Therefore, the conversion problem of the controller's winter and summer working conditions must be considered.
When controlling the supply air temperature, the water volume of the cold coil is usually controlled in summer, and the water volume of the hot coil or the steam flow of the steam coil is controlled in winter. For the convenience of management, the temperature sensor is usually installed on the air supply duct in the machine room where the unit is located.
Indoor temperature control
For some DC systems, fresh air can not only make the environment meet sanitary standards, but also bear the entire indoor load. Since the indoor load changes, the method of controlling the supply air temperature will inevitably fail to meet the indoor requirements and may cause overheating or undercooling. Therefore, the temperature of the place of use must be controlled. It can be seen that the temperature sensor must be placed in the typical area of the controlled room. Since the DC system usually has an exhaust system, it is also a feasible method to install the temperature sensor in the exhaust duct and consider certain corrections.
Except for DC systems, fresh air units are usually used together with fan coil units. In some projects, due to various reasons, such as the limitation of the dehumidification capacity of the fan coil, the fresh air unit bears part of the indoor load during design. This approach does not pose a problem when the fresh air unit is controlled according to the supply air temperature in the design state. However, when the outdoor climate changes and the indoor reaches a thermal balance, such as during certain periods of the transition season, if the air supply temperature is continued to be controlled, it will inevitably cause the room to be overcooled for cold water supply or overheated for hot water supply. In this case, indoor temperature control should be used. . Therefore, in this case, from the perspective of year-round operation, the joint control method of supply air temperature and indoor temperature should be adopted.
Relative humidity control
The main point of relative humidity control of fresh air units is to select the setting position or control parameters of the humidity sensor, which is related to its humidification source and control method.
Steam humidification
For places with relatively high requirements, the amount of steam humidification should be automatically adjusted according to the requirements of the controlled humidity. This method requires that the steam humidifier should use an adjustable valve and a linear characteristic regulator should use a linear controller. Since this method has better stability, the humidity sensor can be placed on the air supply duct in the computer room.
For high-rise civil buildings with general requirements, position control can also be used. In this way, a positional humidifier can be used with a quick-opening valve and a positional regulator, which is beneficial to reducing investment.
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