Clean room FFU air conditioner low-temperature fresh air system

Abstract

The invention belongs to the technical field of clean room temperature and humidity control, and particularly relates to a clean room FFU air conditioner low-temperature fresh air system which comprises a fresh air processing unit, a circulating air supply unit, an exhaust unit and a control unit. Wherein the fresh air processing unit independently processes outdoor fresh air to dew point temperature to form low-temperature dry fresh air. The static pressure box is provided with a fresh air inlet and a return air inlet, and it is ensured that return air does not participate in cold and heat treatment. The control unit achieves temperature control through a two-stage adjustment strategy. In the first-stage adjustment, the opening degree of a fresh air variable air volume valve is controlled based on feedback of a temperature sensor, and the low-temperature fresh air feeding amount is adjusted. And when the valve is at the minimum opening degree and the indoor temperature is still low, the auxiliary electric heating equipment is started for accurate compensation in the second-stage adjustment. And meanwhile, the opening degree combination of the fresh air variable air volume valve and the exhaust variable air volume valve is controlled in a coordinated mode, and the constant positive pressure value in the clean room is dynamically maintained. Return air does not participate in cold and heat treatment, the power of a fresh air fan is reduced, dual energy saving is achieved, and the cold and heat offset phenomenon is avoided.

Description

Technical Field

[0001] This invention relates to the field of cleanroom temperature control technology, specifically to a cleanroom FFU air conditioning low-temperature fresh air system. Background Technology

[0002] The two main conventional design schemes for existing cleanroom air conditioning systems are as follows: Option a Fresh air and return air (or 100% fresh air) enter the air conditioning unit, mix, and are then treated for cooling, heating, and humidification before being delivered into the cleanroom through ductwork. The temperature and humidity of the indoor return air (or exhaust air) are used as control points, and the air conditioning unit's hot and cold water valves (or heating and humidifying steam valves) are adjusted to achieve constant temperature and humidity, as well as constant positive (negative) pressure, within the cleanroom.

[0003] This solution has a significant drawback: fresh air and return air are mixed and processed together through cooling, heating, and humidification before being delivered to the room. However, the temperature and humidity of the return air are generally almost identical to the room's required temperature and humidity. Therefore, it is unnecessary to lower the temperature to the dew point for cooling and dehumidification, and then heat it to a suitable supply temperature, just like with fresh air. As a result, cooling and heating cancel each other out, leading to a significant waste of energy.

[0004] Option b Fresh air, cooled or heated by a fresh air conditioning unit, is delivered to the top mezzanine of the cleanroom. Return air from inside the cleanroom, after undergoing sensible heat treatment via a room dry coil, is also delivered to the top mezzanine. The treated fresh and return air mix within the mezzanine before being delivered into the cleanroom through the top FFUs (Fan Filter Units). In this system, a constant positive pressure is maintained indoors (this positive pressure is a fixed value), resulting in a constant fresh air volume.

[0005] This design scheme is generally used in cleanrooms for electronics, characterized by a large circulating air volume, low heat and humidity load, constant fresh air supply, and the handling of the sensible heat load by the room's return air dry coils. As a result, a large return air wall area is required to accommodate the cross-sectional area needed for the dry coils. Simultaneously, the number of dry coils is relatively large, leading to higher investment costs.

[0006] In conclusion, neither of the two commonly used solutions can meet the energy-saving requirements. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a cleanroom FFU air conditioning low-temperature fresh air system, which solves the problem of energy waste caused by the mutual cancellation of cooling and heating.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a cleanroom FFU air conditioning low-temperature fresh air system, comprising a fresh air treatment unit, which includes a coarse filter, a fresh air conditioning box, a fresh air variable air volume valve and an auxiliary electric heating device connected in sequence along the air supply direction, wherein the fresh air conditioning box is configured to treat outdoor fresh air to the dew point temperature.

[0009] The circulating air supply unit includes a plenum chamber and multiple air handling units (FFUs). The inlet of the plenum chamber is connected to the outlet of the fresh air handling unit, the inlet of each FFU is connected to the plenum chamber, and the outlet leads to the clean room.

[0010] An exhaust unit includes an exhaust variable valve, a silencer, and an exhaust fan box connected in sequence along the exhaust direction. The exhaust unit is located on the exhaust side of the clean room.

[0011] The control unit is connected to the temperature sensor, the fresh air variable air volume valve, the auxiliary electric heating equipment and the exhaust variable air valve, which are installed in the clean room.

[0012] The low-temperature fresh air output from the fresh air handling unit, after being treated to the dew point temperature, is sent into the static pressure box, where it is mixed with the return air from the clean room, and then sent into the clean room by the FFU.

[0013] The control unit is configured to: The opening degree of the fresh air variable air volume valve is controlled according to the feedback signal of the temperature sensor to adjust the amount of low-temperature fresh air supplied, thereby achieving indoor temperature control.

[0014] When the fresh air variable air volume valve is at its minimum opening and the indoor temperature is still lower than the set value, the auxiliary electric heating equipment is activated.

[0015] The opening degrees of the fresh air variable air volume valve and the exhaust air variable air volume valve are coordinated and controlled to maintain the positive pressure value in the clean room.

[0016] In some embodiments, the fresh air conditioning unit separately cools and dehumidifies the outdoor fresh air, and the return air from the clean room enters the static pressure box directly without any cooling or heating treatment.

[0017] In some embodiments, the auxiliary electric heating device is located on the downstream duct of the fresh air variable air volume valve.

[0018] In some embodiments, the control unit is configured to adjust the opening of the fresh air variable air volume valve based on the return air temperature or exhaust air temperature signal fed back by the temperature sensor.

[0019] In some embodiments, the static pressure box is located at the top of the cleanroom, forming the air supply jacket of the cleanroom.

[0020] In some embodiments, the exhaust variable air valve and the fresh air variable air volume valve are linked under the control of the control unit to dynamically balance the supply and exhaust air volume of the clean room.

[0021] In some embodiments, the fan of the fresh air conditioning unit only needs to overcome the air supply duct resistance between the coarse filter and the static pressure box.

[0022] In some embodiments, the cleanroom is an electronics-type cleanroom, which does not have dry cooling coils for handling return air.

[0023] Compared with the prior art, the present invention provides a cleanroom FFU air conditioning low-temperature fresh air system, which has the following beneficial effects: A cleanroom FFU air conditioning low-temperature fresh air system, through innovative architecture and intelligent control logic, achieves comprehensive optimization of energy efficiency, control precision and investment cost, demonstrating significant advantages over traditional solutions.

[0024] In terms of energy efficiency, this invention fundamentally eliminates the energy waste caused by "cold and heat offsetting" in scheme a of the prior art. The system uses low-temperature fresh air as a "cold carrier" to eliminate indoor sensible heat load, while the return air undergoes no cooling or heating treatment before entering the plenum. This not only avoids unnecessary energy consumption, but also significantly reduces the power demand of the fan itself because the fan of the fresh air conditioning unit only needs to overcome the resistance of the fresh air duct, rather than the resistance of the large-volume mixed air duct. Thus, extreme energy saving is achieved at both the source and the flow.

[0025] In terms of control performance, the system abandons the indirect temperature control mode of Scheme B, which relies on dry coils to handle return air, and instead adopts a two-stage regulation strategy of "variable air volume low-temperature fresh air as the main source and electric heating as an auxiliary source". This design achieves high-precision and high-response control of indoor temperature, overcoming the shortcomings of traditional systems such as lag and large fluctuations.

[0026] In terms of economic efficiency and space utilization, the advantages of this invention are particularly prominent. It eliminates the need for ineffective reheating of the return air as in scheme a, and completely avoids the expensive facilities such as large-area return air walls and numerous dry coils required by scheme b. This directly translates into considerable savings in initial investment and frees up more valuable space for production process layout.

[0027] In summary, this invention successfully integrates the advantages of existing technologies while cleverly avoiding their inherent defects, providing a novel solution for cleanroom environmental control that surpasses existing solutions in both technical indicators and economic benefits. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall workflow of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Please see Figure 1 This embodiment describes a cleanroom FFU (Fan Filter Unit) air conditioning low-temperature fresh air system, comprising a fresh air handling unit: this unit serves as both the "cold source" and "humidity source" of the system. Its inlet is connected to the outdoor environment, and a coarse filter is installed at the inlet to remove large particulate pollutants from the fresh air. Next is the fresh air conditioning unit, whose core function is to deeply cool and dehumidify the fresh air through a surface cooler, ensuring it is treated to the dew point temperature (e.g., 10-15°C). This step fixes the moisture content of the air supplied to the cleanroom. Following this are a fresh air variable air volume valve and auxiliary electric heating equipment. The outlet of this unit is connected to the fresh air inlet of the plenum chamber via an air supply duct.

[0033] Circulating air supply unit: This unit is the main pumping unit of the system. Its core is the plenum, which is typically located above the ceiling of the cleanroom, forming an air supply jacket. Multiple FFUs (Fan Filter Units) are evenly distributed at the bottom of the plenum. The plenum has two main inlets: one connects to the fresh air duct from the fresh air handling unit; the other is a return air inlet, connected to the bottom of the cleanroom via a return air grille, forming a complete airflow circulation path.

[0034] Exhaust Unit: This unit acts as the system's "pressure regulator." Its inlet connects to the interior of the cleanroom via an exhaust grille, and then, along the exhaust direction, it is sequentially connected to an exhaust variable valve, a silencer, and an exhaust fan housing. This unit systematically exhausts indoor air, working with the supply air unit to maintain dynamic pressure balance within the room. The exhaust unit is connected in parallel with the recirculating air supply unit.

[0035] Control Unit: This unit is the "brain" of the system. It establishes a two-way signal connection with the temperature sensor, fresh air variable air volume valve, auxiliary electric heating equipment, and exhaust variable air valve through control circuits, collects data, and issues control commands.

[0036] After the system starts, it will run according to the following process and logic: Fresh air handling and delivery: Outdoor fresh air is drawn in and, after preliminary purification by a coarse filter, enters the fresh air conditioning unit. Here, the fresh air is deeply cooled, and excess moisture condenses on the surface of the cooling coil, thus achieving cooling and dehumidification to the preset dew point temperature. Subsequently, the low-temperature fresh air flows through a variable air volume valve, the opening of which is dynamically adjusted by the control unit. Finally, this rigorously treated, low-temperature, dry fresh air is constantly delivered into the plenum chamber.

[0037] Airflow mixing and circulation: Inside the plenum chamber, the low-temperature fresh air from the fresh air handling unit is thoroughly mixed with the cleanroom return air, which enters through the return air grille and has not undergone any cooling or heating treatment. The mixed air is then efficiently filtered by the FFU fan and delivered into the cleanroom as a uniform vertical airflow.

[0038] Temperature control: This is the core control component of the system, employing a two-stage regulation strategy. Level 1 Regulation (Variable Air Volume Regulation): The control unit receives signals from temperature sensors installed in the cleanroom's return or exhaust air ducts. When the indoor temperature is higher than the set value, the control unit increases the opening of the fresh air variable air volume valve to increase the cooling input; conversely, it decreases the opening to reduce the cooling input.

[0039] Secondary regulation (auxiliary heating): When the indoor sensible heat load is very low and the fresh air variable air volume valve is closed to its minimum opening (at this time, the fresh air volume only meets the hygiene and positive pressure requirements), if the temperature is still too low, the control unit will activate the auxiliary electric heating equipment to precisely heat and compensate the already cooled fresh air. This design completely avoids the energy waste caused by the traditional "cooling first and then heating" approach.

[0040] Positive pressure control: The control unit monitors the pressure value inside the cleanroom in real time and compares it with the set positive pressure value. By coordinating the opening combinations of the fresh air variable air volume valve and the exhaust variable air volume valve, it ensures that the air volume supplied to the cleanroom is always slightly greater than the exhaust air volume, thereby stabilizing the positive pressure inside the room. This is a dynamic, closed-loop feedback control process.

[0041] The fresh air conditioning unit is a modular unit, containing a pre-filter, a cooling coil (for cooling and dehumidification), and a fan. Its control precision directly determines the humidity control level of the cleanroom.

[0042] To achieve efficient heating, both the fresh air variable air volume valve and the exhaust variable air valve are electric valves with fast response and high control precision. The auxiliary electric heating equipment is preferably a PTC (positive temperature coefficient) electric heater due to its self-limiting temperature characteristics and higher safety. It is recommended to install it on the supply air duct after the fresh air variable air volume valve to ensure direct and efficient heating.

[0043] The external control unit uses a PLC (Programmable Logic Controller) or DDC (Direct Digital Controller) as the core processor and writes corresponding control algorithms to achieve fast, stable and coordinated control of multiple parameters such as temperature and positive pressure.

[0044] In this embodiment, the coarse filter is a G4 pre-filter bag filter, which is installed at the air inlet of the fresh air conditioning unit to filter larger particles in the air and protect downstream equipment.

[0045] The core function of the fresh air conditioning unit is cooling and dehumidification. The unit contains, in sequence, a surface cooler, a baffle plate, and a reheater (optional, but in this embodiment, it primarily relies on subsequent electric heating). In this embodiment, the surface cooler uses chilled water supplied at 7℃-12℃ to ensure that the fresh air under various outdoor weather conditions is treated to the required dew point temperature, such as 12℃. This process fixes the moisture content of the fresh air, thus laying the foundation for humidity control in the cleanroom. The treated low-temperature fresh air is then delivered through air supply ducts.

[0046] The fresh air variable air volume valve is a pressure-independent electronic valve, whose actuator is linked to the control system. It is installed on the supply air duct after the fresh air is treated by the fresh air conditioning unit.

[0047] The auxiliary electric heating equipment uses armored electric heating tube heaters to ensure safety. This equipment is installed on the downstream duct of the fresh air variable air volume valve to avoid affecting the valve's normal operating temperature range. The power of the electric heater is selected based on the maximum heat load of the cleanroom and features multi-stage adjustment or multi-level control for precise heating.

[0048] The static pressure chamber is enclosed by a metal plate or polymer sheet on the top of the cleanroom, forming a closed cavity. Multiple mounting ports matching the dimensions of the FFU (Fan Filter Unit) are opened at its bottom.

[0049] The FFUs used are standard-sized (e.g., 1175mm x 575mm) and contain high-efficiency particulate air (HEPA) filters. All FFUs are installed at the bottom of the static pressure chamber with a certain full coverage ratio.

[0050] The exhaust unit's variable displacement damper also uses a pressure-independent electronic type. The silencer employs a micro-perforated plate structure to eliminate noise generated by the exhaust fan while meeting the cleanliness requirements of the cleanroom. The exhaust fan housing uses frequency conversion control to adapt to changes in airflow.

[0051] The specific steps for the control unit and system operation are as follows: Temperature control main loop: The control system collects signals from the temperature sensor in real time. When the indoor temperature is higher than the set value (e.g., 23℃), the opening of the fresh air variable air volume valve is increased proportionally to introduce more cooling capacity carried by the low-temperature fresh air, thereby eliminating the indoor sensible heat load.

[0052] Temperature control auxiliary circuit: When the indoor heat load is very low, the fresh air variable air volume valve will close slightly to maintain the minimum fresh air volume. If the temperature is still lower than the set value (e.g., 22℃) at this time, it is determined that adjusting the air volume alone is not enough to meet the requirements, and then the auxiliary electric heating equipment is activated to heat the already treated low-temperature fresh air with equal humidity to accurately compensate for the heat gap.

[0053] Positive pressure control loop: The control system presets a target indoor positive pressure value (e.g., 15 Pa). It monitors the indoor and outdoor pressure difference in real time and coordinates the actions of the fresh air variable air volume valve and the exhaust variable air volume valve. For example, when the positive pressure is low, the opening of the fresh air valve is increased while the opening of the exhaust valve is proportionally decreased until the positive pressure stabilizes. The difference between the fresh air volume and the exhaust air volume is the infiltration air volume required to maintain positive pressure.

[0054] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cleanroom FFU (Fan Filter Unit) air conditioning low-temperature fresh air system, characterized in that, include: The fresh air handling unit includes a coarse filter, a fresh air conditioning unit, a fresh air variable air volume valve, and an auxiliary electric heating device connected in sequence along the air supply direction. The fresh air conditioning unit is configured to process outdoor fresh air to the dew point temperature. The circulating air supply unit includes a plenum chamber and multiple air handling units (FFUs). The inlet of the plenum chamber is connected to the outlet of the fresh air handling unit, the inlet of each FFU is connected to the plenum chamber, and the outlet leads to the clean room. An exhaust unit includes an exhaust variable valve, a silencer, and an exhaust fan box connected in sequence along the exhaust direction. The exhaust unit is located on the exhaust side of the clean room. The control unit is connected to the temperature sensor, the fresh air variable air volume valve, the auxiliary electric heating equipment and the exhaust variable air valve, which are installed in the clean room. The low-temperature fresh air output from the fresh air handling unit after dew point temperature treatment is sent into the static pressure box, where it is mixed with the return air from the clean room, and then sent into the clean room by the FFU. The control unit is configured to: The opening degree of the fresh air variable air volume valve is controlled according to the feedback signal of the temperature sensor to adjust the amount of low-temperature fresh air supplied, thereby achieving indoor temperature control. When the fresh air variable air volume valve is at its minimum opening and the indoor temperature is still lower than the set value, the auxiliary electric heating equipment is activated. The opening degrees of the fresh air variable air volume valve and the exhaust air variable air volume valve are coordinated and controlled to maintain the positive pressure value in the clean room.

2. The cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The fresh air conditioning unit separately cools and dehumidifies the outdoor fresh air, while the return air from the clean room enters the static pressure box directly without any cooling or heating treatment.

3. The cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The auxiliary electric heating device is installed on the downstream duct of the fresh air variable air volume valve.

4. A cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The control unit is configured to adjust the opening degree of the fresh air variable air volume valve based on the return air temperature or exhaust air temperature signal fed back by the temperature sensor.

5. A cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The static pressure box is located at the top of the clean room, forming the air supply jacket of the clean room.

6. A cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The exhaust variable air valve and the fresh air variable air volume valve are linked under the control of the control unit to dynamically balance the supply and exhaust air volume of the clean room.

7. A cleanroom FFU air conditioning low-temperature fresh air system according to claim 1, characterized in that: The fan of the fresh air conditioning unit only needs to overcome the air supply duct resistance between the coarse filter and the static pressure box.

8. A cleanroom FFU air conditioning low-temperature fresh air system according to any one of claims 1 to 7, characterized in that: The cleanroom is a general-purpose cleanroom, which does not have dry cooling coils for handling return air.

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