Discussion on the design of clean air conditioner in Class 100 clean room

1. Clean air conditioning system design, clean air conditioning air exchange times

Class 100: The number of air changes is 400 times / hour (section wind speed 0.36m / s)

Class 1000: The number of air changes is 80 times / hour

Class 10000: The number of air changes is 40 times / hour

Class 100000: The number of air changes is 25 times / hour

2, clean room cooling load

Summer cooling load includes envelope load, personnel load, lighting load, production equipment load, fan load in air conditioning unit, fresh air load, etc. Among them, the production equipment is provided by Party A to provide the power of the equipment and the displacement of the equipment. After calculation, the main clean room area index is 1170W/m2, and the cleaning room area index is 1220W/m2.

3. Fresh air volume and air supply volume in clean room

The fresh air volume takes into account the air volume required for personnel hygiene, the air volume of the production equipment, and the air volume required to maintain the positive pressure of the clean room. The air supply volume of the Class 100 clean room air conditioner is calculated from the cold load and the enthalpy difference. In addition to the calculated values of the cooling load and the enthalpy difference, the air conditioning air supply volume of the clean room below 1000 is also considered to be the minimum number of clean air exchanges. The reason why it is different from the Class 100 clean room is due to the different air conditioning methods.

4, 100-level main clean room (including cleaning room) air conditioning

PAHU+AHU+FFU air-conditioning mode, among which: PAHU is a fresh air treatment unit, AHU is an air treatment unit, FFU is a high-efficiency filter system with a fan and PAHU is added, and the clean room positive pressure is controlled by the PAHU fan motor frequency conversion. The influence of changes in the outdoor environment on the clean room is reduced, which is beneficial to the temperature and humidity control of the clean room. Each workshop is an independent air conditioning system. The air-conditioning unit AHU will mix the return air drawn from the indoor air with the fresh air treated by the new fan unit PAHU. After filtering, cooling, humidifying, etc., it will be sent to the space on the ceiling of the clean room, and then returned to the wall by the return air technology. The indoor air mixture to the ceiling is sent to the room via the FFU. The local exhaust of the production equipment is discharged to the outside by the exhaust fan.

The clean room airflow is sent up and down one-way flow, the ceiling is basically covered with FFU air supply, the floor adopts an elevated floor with an opening ratio of 18%, and some floors have regulating valves to adjust the flow pattern of the airflow.

5, 1000 level dressing room and small washing room

The auxiliary clean room uses air conditioning with AHU and end efficient filters. When the calculated air-conditioning air volume is less than the calculated value of the air-conditioning frequency, the secondary air return is used to control the temperature and humidity of the clean room, and the initial investment of the air-conditioning unit is reduced.

6, air treatment

The fresh air in the clean room is filtered by the primary and intermediate effects of PAHU, and then sent to the AHU after cooling coil treatment. The cooling function of the cooling coil is achieved by the chilled water supplied by the central cold source when the fresh air needs to be dehumidified.

The new and return mixed air is filtered, cooled, heated and humidified by AHU:

a. Cooling: The chilled water is supplied from the central cold source to flow through the AHU coil to achieve cooling.

b. Filtration: The air is filtered through the primary and intermediate filter placed in the AHU, and then sent to the chamber through the end high efficiency filter.

c. Heating: The heating function is realized by an electric heater installed in the air supply duct, and the electric heater only plays an auxiliary role in this system.

d. Humidification: The dry steam humidifier is humidified into the air through a steam nozzle installed in the air supply duct. The humidifier is electrothermal and its water supply is RO water.

7, cold source setting and air conditioning water system

The air-conditioning equipment used in the project uses a screw-type chiller, the refrigerant is R134a, and the chilled water supply back water temperature is 7 °C / 12 °C. The air conditioning water system is a primary pump variable water system. According to the change of the water volume of the system, the number of pumps is controlled to realize the economic operation of the system. At the same time, the pressure difference bypass control is provided between the supply and return water mains to ensure the supply and return of water. The pressure differential is constant and there is enough water to flow through the chiller's evaporator.

8, automatic control system

The fan motor of the engineering new fan group adopts the frequency conversion automatic control. Under the premise of ensuring hygiene, the frequency converter is adjusted according to the static pressure of the clean room, so that the static pressure of the clean room does not change with the change of the exhaust air volume of the production equipment, and at the same time, it plays an energy-saving role. The project requires high temperature and humidity. In summer, the cooling and dehumidification are realized by the cooler. Therefore, the maximum control method of temperature and humidity PID output is adopted. The chilled water volume of AHU and PAHU is controlled by an equal percentage two-way electric control valve. The main clean room has a large area for each AHU, so each AHU is equipped with 2~3 temperature and humidity sensors for average control of temperature and humidity. The dehumidification of the air conditioning system is mainly done by PAHU.