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Division of clean room air conditioning system

Jul 30, 2019

(a) purification of air conditioning system division principle

1, cleanliness, temperature, humidity and its accuracy of the same or similar clean room should be divided into a purification air conditioning system.Easy to control cleanliness and temperature and humidity.2. The clean room close to each other should be classified as a system, which can reduce the length of system pipelines and the crossing of pipelines.

3. When conditions permit, the mixed flow purification air conditioning system can be composed of 4, 5 unidirectional flows and 6, 7 and 8 non-unidirectional flows.

4, clean room should not be combined with the general air conditioning room as a system.

5, use the law and use time is not the same as the clean room is not suitable for a purification air conditioning system.

6, dust production, heat, harmful substances, noise room should be designed as a separate system.

7. Rooms that are highly toxic and cause fire and explosion after mixing shall not be combined into one purification air conditioning system.

8, there are highly toxic and inflammable and explosive a, b room should be a separate system, and should not return the air dc system.

9, a purification air conditioning system is not easy to be too large.In general, the purification air delivery volume should not exceed 100,000 m; otherwise, the air treatment equipment is too large, noisy, the return air duct is large, occupies a large space and area, and the use is not flexible.

10, clean air conditioning system division should also consider the air duct, return duct, exhaust duct and water, electricity, gas and other pipelines layout, as far as possible to make a reasonable, short, easy to use management, reduce the intersection and overlap.

11. The heat, humidity and purification treatment of fresh air in the air conditioning system can be centralized or decentralized

The principle of dividing the local exhaust air system of the process equipment

1. The partial exhaust air system of the process equipment should not be too large, and the exhaust air points of each exhaust air system should not be too much, so that the exhaust air management and adjustment are convenient and the exhaust air effect is good.

2. One exhaust air system should not cross two or more purification air conditioning systems.

3. The exhaust air which produces highly toxic, explosive, fire, condensation, crystallization and harmful substances after mixing shall not be combined into one exhaust air system.

4. The exhaust air of different rooms and equipment should not be combined into one exhaust air system.

5.Comparison and selection of air supply type of clean room purification air conditioning system


(a) purification and air conditioning air supply combined air supply type, usually also known as the centralized type of air supply.The scheme of purifying air conditioning units (air handling units AHU) set in air conditioning room, purification of all air conditioning supply air purification were conducted in purifying air conditioning unit and hot, wet processing, and the large supply air duct will all air supply to the clean room condole top, repass is located in the clean room ceiling on the terminal hepa filter or efficient filters to clean indoor air supply outlet filtered, to realize the clean room process required temperature, humidity, cleanliness, and the pressure difference of the room,The return air in the clean room passes through the return air inlet and return air duct, and then is connected to the purification air conditioner unit in the air conditioning room. After mixing with the fresh air, the air purification and heat and humidity treatment are repeated.This scheme can be divided into full fresh air supply scheme (dc system);One air return program;The first and the second air return schemes and the MAU plus FFU schemes are four different air supply types.This air supply scheme is the most widely used air supply scheme for clean rooms, especially non-one-way flow clean rooms.The system division of this air supply scheme is clear, and the air volume, temperature and humidity control and regulation are single.However, when the cleanliness level is higher and the air supply volume is larger, the air conditioning room occupies a large area, the volume of the air supply and return air pipe occupies a large area and space, the air supply and return air pipe is long, the residual pressure of the air supply fan is high, the noise is big, and the air supply consumes a large amount of electricity.Therefore, this air supply scheme is more suitable for the air supply of the lower level non-unidirectional flow clean room, and less economical and reasonable for the air supply of the one-way flow clean room above level 5.


1. Air supply scheme of AHU with fresh air (dc system)

The full fresh air purification air supply scheme is used in special air supply schemes for clean rooms where no return air is allowed.For example, the production of clean room process is classified as class a and class b fire hazard level or the process produces highly toxic and other harmful substances that are not allowed to return air in the clean air supply system.

2. Air supply scheme of AHU primary air return

The air supply scheme of primary air return is usually used in the clean room with large calorific value or moisture yield, and the air supply of indoor residual heat or moisture is greater than, equal to or close to the purification air supply in the non-one-way flow clean room with low cleanliness grade.

3. Air supply scheme of purification air conditioning with AHU primary and secondary air return

In order to save energy, eliminate the air heat and heat in the process of heat and humidity treatment offset each other, in the clean room purification air supply capacity is greater than the air supply capacity of the air conditioning to eliminate residual heat and humidity, it is best to use the first and second air return program, the second mixing point design in the system air supply point, this side is the most energy saving, the most economic air supply program.

4.MAU+RAU's air supply scheme for purification air conditioning

This solution for multiple more clean room cleanliness, temperature, humidity, different requirements, the yield of indoor heat and moisture content are also similar, in order to ensure that each of the clean room cleanliness, temperature, humidity and precision requirement, to set up multiple cycle unit, circular air output of the unit is to purify the air output, and within the unit, set up necessary heat, wet processing equipment, used to supplement the shortage of the fresh air unit heat, wet process and ensure that the clean room temperature and humidity precision fine-tuning section.Because the circulation unit is located on the ceiling of the clean room, the residual pressure of the circulation unit's air supply is relatively small, the volume of the unit and the noise and vibration of the unit are also small, and the return air duct is relatively short.However, it is necessary to pay attention to the condensate discharge of the circulation unit.The fresh air units in this scheme are located in the air conditioning room, and all the fresh air needed for these clean rooms is purified by the fresh air units (MAU) and the centralized treatment of heat and humidity.It is then distributed to each cycle unit and mixed with its return air.The fresh air volume of the fresh air unit should not only supplement the exhaust air of each clean room but also ensure the positive pressure of each clean room.The heat and humidity treatment of the fresh air unit had better go to the mechanical dew point of air in a clean room. If the heat and humidity treatment point of the fresh air is lower than the mechanical dew point of the clean room, the fresh air will not only bear the wet load of the fresh air itself, but also eliminate the wet load of the clean room. At this time, the surface cooler in the circulating unit can be a dry surface cooler.

The scheme of purifying air supply and separating air supply from air conditioning is usually called semi-centralized or decentralized air supply scheme.To greatly save the energy consumption of the runtime, will eliminate clean indoor remaining heat and wet air conditioning air output (usually is greatly less than the clean room to purify the air output), by the air conditioner room air unit (MAU) necessary to purify and hot wet processing, and the total of 50 to 90% of the guarantee of the purity of the clean room to purify the air output by the clean room near the circulation unit to purify and added hot, wet processing, or directly use head on the ceiling fan filter units) and dry coil to solve the clean room cleanliness level and temperature of fine-tuning.This air supply scheme, which is separated from air supply by air conditioning, can not only save energy for operation, but also greatly reduce the area of air conditioning room, save the huge air supply and return pipeline, and reduce the space height of clean room.Such purification air supply scheme can be divided into: air conditioning unit (AHU) add fan filter unit (FFU) scheme, fresh air unit (MAU) add cycle unit (RAU) add (FFU) scheme;Fresh air unit (MAU) + fan filter unit (FFU) + dry cold tube


(DC) and other three air supply schemes.

1.Air supply scheme of air conditioning units AHU(MAU) and fan filter units (FFU) in this scheme, all heat and wet loads of the air conditioning system (heat and wet loads generated in the clean room and heat and wet loads of fresh air) are borne by the air conditioning units located in the air conditioning room.At this time, the air supply of the air conditioning unit is the air supply to eliminate the residual heat and humidity of the system (including all fresh air and some return air, but far less than the purification air supply to ensure the cleanliness of the clean room), and it should be able to ensure the constant temperature and relative humidity of the clean room.The cleanliness of the clean room is ensured by a fan filter unit (FFU) on the ceiling of the clean room which circulates and filters the purified air supply.It should be noted in this scheme that the heat generated during the operation of FFU should also be borne by the air-conditioning unit.This scheme is more suitable for mixed flow cleanroom with partial vertical unidirectional flow in large non-unidirectional flow cleanroom.

2.Fresh air unit (MAU) plus (he) cycle unit and fan filter unit (head) to purify the air conditioning air supply scheme, this scheme for multiple more clean room cleanliness, temperature, humidity, different requirements, the yield of indoor heat and moisture content are also similar, in order to ensure that each of the clean room cleanliness, temperature, humidity and precision requirement, to set up multiple cycle unit, circular air output of the unit is to purify the air output, and within the unit, set up necessary heat, wet processing equipment, used to supplement the shortage of the fresh air unit heat, wet process and ensure that the clean room temperature and humidity precision fine-tuning section.Because the circulation unit is located on the ceiling of the clean room, the residual pressure of the circulation unit's air supply is relatively small, the volume of the unit and the noise and vibration of the unit are also small, and the return air duct is relatively short.However, it is necessary to pay attention to the condensate discharge of the circulation unit.The fresh air units in this scheme are located in the air conditioning room, and all the fresh air needed for these clean rooms is purified by the fresh air units (MAU) and the centralized treatment of heat and humidity.It is then distributed to each cycle unit and mixed with its return air.The fresh air volume of the fresh air unit should not only supplement the exhaust air of each clean room but also ensure the positive pressure of each clean room.The heat and humidity treatment of the fresh air unit had better go to the mechanical dew point of air in a clean room. If the heat and humidity treatment point of the fresh air is lower than the mechanical dew point of the clean room, the fresh air will not only bear the wet load of the fresh air itself, but also eliminate the wet load of the clean room. At this time, the surface cooler in the circulating unit can be a dry surface cooler.

When more than one in the clean room has a number of level 1, 10, 100 high purification level of vertical uniflow cleanroom, in order to reduce the burden of the circulation unit (he) and to send and return air duct section, the circulation unit only solve the uniflow clean room air conditioning air output, to ensure clean room temperature, relative humidity and the cleanroom positive pressure, and for the most part accounts for more than 90% of the delivery is located in the clean room ceiling panels on the head to burden, to ensure the high level of cleanliness of clean room.3.Fresh air unit (MAU) plus fan filter unit (head) and dry cold tube (DC) of purifying air conditioning air supply plan is the fresh air will be fresh air crew to clean room hot wet than line and relative humidity below 95% line intersection, fresh air moisture load of the crew will not only itself, but also burden clean indoor moisture load, fresh air units to ensure that the relative humidity of the clean room need.The dry cooling load of the insufficient part of the heat treatment of the fresh air unit will be supplemented by the dry surface cooler located on the ceiling of the clean room (or in the tunnel).Because the dry table cooler is located on the suspended ceiling or in the tunnel through which the FFU circulating air passes, the dry cooling load made up by the dry table cooling is brought to the clean room by the circulating air.The fresh air treated by the fresh air unit is sent to the air supply static pressure box in the clean room by means of pipelines which can be most evenly mixed with the FFU circulating air.FFU is arranged on the ceiling of the clean room. The circulating air mixed with fresh air is filtered by FFU and sent to the clean room after being filtered by hepa filter to ensure the cleanliness of the clean room.The specifications of FFU are mainly 1200mm×600mm and 1200mm×1200mm, whose section wind speed should be ≥0.45m/s, residual pressure should be ≥120Pa, and noise should be ≤50dB(A).FFU fan air volume should be adjustable, high efficiency filter should be replaceable.The dry cold coil is generally composed of two rows. In order to reduce the spacing between the aluminum fins of the resistance ≥3mm, the resistance loss should be 30~40Pa. The surface wind speed of the circulating wind through the dry coil is < 2m/s, and it is better to be 1.5m/s.The inlet water temperature into the cold water of the dry coil should be 2℃ higher than the dew-point temperature of the clean room, usually referred to as medium chilled water.Although it is called a dry coil, condensate may be generated during initial operation, so the dry coil should also have a condensate drip tray and drainage measures.

In this scheme, the relative humidity of the clean room is guaranteed by the fresh air unit (MAU), the temperature of the clean room is guaranteed by the dry cold coil, and the cleanliness of the clean room is guaranteed by FFU.The MAU plus head and purification of DC air conditioning air supply plan, at present in our country and foreign microelectronics (IC) industry, optoelectronic (TFT - LCD, LCD, LED, etc.) industry and so on in the large area, high cleanliness grade clean workshop become widely available, it has convenient adjustment, energy-saving significantly, to adapt to the process of upgrading, and greatly save non-production area and the advantages of non-production space.Moreover, with the continuous development and progress of clean technology and clean equipment, the efficiency of FFU fan is continuously improved, the power consumption is continuously reduced, and the overall price is continuously reduced. The initial investment is basically the same as other types of air supply schemes, but the operating cost is greatly saved.



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