1. Introduction to Common Purification Room Air Conditioning Systems
For purification room air conditioning systems with a relatively high cleanliness level (above Class 5), they usually consist of three main parts: FFU (Filter Fan Units), cooling coils, and fresh air handling units. Among them:
The function of FFU is to purify the air. It is an integrated unit composed of a high - efficiency filter and a fan. The fan is a high - efficiency silent fan, preferably with variable - frequency control. In this way, by adjusting the fan speed, the initial resistance and the final resistance of the filter can be balanced, so that the outlet air speed of the FFU always remains constant.
The cooling coil is used to control the temperature of the purification room.
The fresh air handling unit is used to control the humidity and pressure difference of the purification room. For purification rooms with high requirements for temperature and humidity, the fresh air handling unit must also be equipped with a dehumidifier and a humidifier. Moreover, in order to accurately control the pressure difference of the purification room, the fan in the fresh air handling unit usually needs variable - frequency control, and the pressure difference of the purification room is balanced by adjusting the fan speed. A schematic diagram of the common air flow in the purification room is shown in Figure 1.
2. Method of Producing Medium - temperature Water by Conventional Plate Heat Exchangers
The air - conditioning temperature in the clean room is usually controlled by the cooling coil. The air in the clean room passes through the return air duct and then exchanges heat with the cold water in the cooling coil to achieve the cooling effect. For high - level clean rooms, due to the relatively large heat load generated by production equipment, lighting, FFU, etc. in the clean room, refrigeration is required throughout the year. Therefore, there is usually only cold water in the general cooling coil and no hot water is needed. A good design scheme not only requires the temperature of the purification room to be accurately controlled and operate stably, but also requires energy conservation.
Usually, when designing a purification room, due to the limited height of the original factory building, after the construction of the purification room, there are various pipes, cable trays, air ducts, FFU and other equipment in the ceiling. So the limited ceiling space becomes even smaller. In order to facilitate maintenance and prevent dust accumulation in the ceiling, it is usually required that the fewer pipelines in the ceiling, the better. Therefore, it is best not to install condensate pipes and condensate water collection trays for the cooling coil, which requires that the cooling coil should not produce condensate. In order to prevent the cooling coil from producing condensate, the temperature of the chilled water entering the cooling coil should not be too low. Generally, medium - temperature water of 12 - 17°C is required. However, refrigerators usually can only provide chilled water at 5 - 10°C. Therefore, most design schemes produce medium - temperature water through plate heat exchangers.
However, plate heat exchangers have the following disadvantages:
Large water resistance: The water resistance of plate heat exchangers is large (generally around 100 kPa), which will increase the head of the primary chilled water circulation pump and the secondary medium - temperature water circulation pump, invisibly increasing the power of the water pumps and resulting in considerable energy consumption.
Large energy loss in the heat - exchange process: A considerable part of the energy of the chilled water and medium - temperature water is lost in other ways during the heat - exchange process and cannot be fully converted.
High maintenance cost: Due to the complex pipe structure inside the plate heat exchanger, it is very easy to be blocked. Therefore, the water quality requirements are high, and regular maintenance and cleaning are required.
Need to add a make - up water pipe: Since the two sides of the plate heat exchanger are the secondary medium - temperature water circulation system and the primary chilled water circulation system, they are independent of each other.
Suzhou Pharma Machinery Co.,Ltd.
2025/08/11
Gino
