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Purification engineering HVAC system design principles
2023/9/12
As an important part of the clean room control system, the HVAC system mainly through the control and monitoring of the air temperature, humidity, suspended particles, microorganisms, etc. of the production environment to ensure that the environmental parameters meet the quality requirements, avoid the occurrence of air pollution and cross-pollution, and provide a comfortable environment for the operator. In addition, the HVAC system can also reduce and prevent the adverse effects of products on operators during the production process, and protect the surrounding environment. For clean rooms, a clean and safe space environment is a key factor that must be considered in the design of air conditioning systems.
First, the role of HVAC system
1, to provide a user environment that meets the requirements of cleanliness, temperature and humidity, wind speed, noise and other parameters;
2. Remove all microbial particles in the air supply through air filtration;
3. Air flow technology makes the room sterile and dust-free;
4, positive pressure control to achieve orderly pressure gradient distribution throughout the clean room;
5, the appropriate temperature and humidity regulation to inhibit bacterial reproduction, reduce the amount of human bacteria.
Second, the composition of HVAC system
1, air treatment equipment: including initial effect filter, medium effect filter, high efficiency filter, dehumidifier, humidifier, silencer and static pressure box, etc., Chengquan clean project often uses imported brand AAF high efficiency filter and Duolexin dehumidifier and humidifier.
2. Air conveying equipment: including fans and air ducts, etc., the air ducts connect the air handling equipment, fans and the room to be adjusted. Chengquan clean project often uses imported brand AAF fan.
3, air distribution device: including supply air outlet and return air outlet. The organization form of air flow directly affects the effect of air conditioning, therefore, it is necessary to reasonably arrange the location of the supply and return air outlet in the room to be adjusted, and reasonably determine the air supply speed and air supply volume. Indoor air flow type has up to down, up to up, down to back and nozzle centralized air supply. The types of air supply ports are orifice, grille air supply port, shutter air supply port, slit air supply port, diffuser and air supply hole plate, etc.
4, cold source and heat source: including central air conditioning, energy-saving ice storage air conditioning, purification air conditioning, water cooling and air cold and heat recovery air conditioning units; Heat source: including heating boiler, heat pump equipment, electric heater, etc. The cold source equipment commonly used in Chengquan clean project is the international first-class brand Daijin's first level variable frequency air duct air conditioner.
The task of the dynamic control device is to keep the temperature, humidity and other air state parameters of the adjusted room in the allowed fluctuation range; Ensure the safe operation of air conditioning equipment; To realize the economical operation of air conditioning system; Reduce the workload of operational staff.
Third, the design principles of HVAC system
1, strict implementation of mandatory norms: fire protection, environmental protection, occupational health and safety, energy saving and emission reduction; The general specification of the design needs to focus on the above specifications to meet the requirements of drawing review.
2, it is understood that most of the domestic experts and scholars have been inclined to the fresh air treatment alone, which is more conducive to the control of pressure difference, conducive to the flexible use of operating rooms, conducive to the control of clean room temperature humidity, can prevent the air in the purification system and other problems caused by the centralized fresh air treatment of all the wet load.
3, humidity priority is mainly to prevent long-term high humidity in the system mildew, system design protection is essential. However, for the temperature and humidity regulation in the room requires it to be achieved at the same time, the real constant temperature and humidity controller can do this, not the pipe humidity pipe temperature, the above statement only in the control system temperature, humidity controller is a separate two controllers or a controller within two independent process control procedures have a certain sense.
4, winter still need to purify the air conditioning system to provide chilled water, but the chiller is not always refrigeration, only when the outdoor environment temperature is higher or the indoor heat load is larger will work automatically.
5, summer purification air conditioning is best to have hot water. Because in high temperature weather, the unit gives priority to dehumidification and makes the air too cold, and needs heat compensation to achieve constant temperature and humidity and reduce the relative humidity of the air. Although the unit is equipped with electric heating compensation, the general design value is small, and even the graded start can not be as easy to control the size of the heat as hot water, which will affect the stability of the air supply temperature.
6, by controlling the new and return air mixed temperature and humidity, can not avoid the cold coil too cold and heat balance caused by the energy consumption problem of the unit operation can only be dictated by a set of temperature and humidity sensor system, this sensor system can only be used to sense the temperature and humidity in the room, because stable control of the temperature and humidity in the room is our ultimate goal. If the sensor is placed in the new return air mixing place, the temperature and humidity in the room is bound to be disturbed, any air conditioning system is to maintain the dynamic balance of temperature and humidity in a specific service area, it is impossible to appear two balance points before and after the heat exchanger.
7, each professional closely cooperate, do a good job of integration, not only the pipe in the ceiling should be integrated, but also under the ceiling should be integrated, all professions should be integrated, if which professional to pass from other professional rooms, to seek the consent of other professionals, for example, the internal drainage pipe from the substation, to ask the power supply professional opinions; Construction professionals do ramp, ramp through the foundation beam, to ask the height of the structural professional foundation beam, whether it is feasible; Professional design of steel structure reinforcement cable-stayed support, to consider whether the professional door is blocked; Leave holes in the exterior wall, depending on whether the building elevation is beautiful.
