Common scheme electronic dust-free plant clean air conditioning works Compare
At present, there is no uniform level of air cleanliness or production environmental control requirements for electronic products uniform provisions, it is generally based on "clean plant design specifications" (GB50073-2001) and practical experience in electronic product manufacturers, etc. to determine the electronic plant Requirements cleanliness levels and temperature and humidity.
1. The indoor air parameters required
(1) temperature and humidity requirements: temperature is generally 24 + 2 ℃, relative humidity of 55 + 5%.
(2) Large fresh air. Because within this type of workshop, more staff may be taken following the best value according to the following
Value: 10 to 30% of total non-unidirectional flow clean room air volume; fresh air ventilation and indoor compensation required to maintain the interior pressure value; the amount of fresh air per hour to maintain indoor ≥40m3 / h.
(3) air volume. In order to meet the clean toxic dust-free workshop within a few heat and moisture balance, it requires a large amount of wind, on 300 square meters of shop floor, ceiling height of 2.5 meters, if it is ten thousand, the air supply is required 300X2.5X30 = 22500m3 / h of air volume (ACH, is ≥25 times / h); if it is one hundred thousand, and the air supply is required 300X2.5X20 = 15000 m3 / h of air volume (ACH, is ≥15 times / h).
2. Comparing the selection of air conditioning program
(1) air handling units + chiller + HEPA
    This is one of the most traditional design clean air conditioning systems. Modular air handling units contains various functional segments, such as mixing section, the early effect filter section, cooling section, secondary air segment (or intermediate), the heating section, humidification section, in effect filter section, fan section and so on. Its cold source chillers offer.
Advantages:. A good air treatment effect, due to air through centralized processing, in the process of being lower air pollution levels. Air temperature, humidity control more precise;. B is more appropriate to have a centralized cooling source or a larger plant;. C air conditioning cold and heat sources can be combined or independent air-conditioning system in the plant common cold and heat source; D maintenance. lower frequency, E. Low noise workshop.
The disadvantage: A need for supporting the freezing room or outdoor space to place the heat pump. Another need to place air conditioning room air handling units, such as the 25000m3 / h of air handling units, common dimensions around 6450X1850X2250mm. For the old plant transformation project, it is rather difficult to vacate an air-conditioned room 20-30m2 of; B high cost. Features: A proposed new wind through centralized processing, then mixed with return air, thus reducing the processing load on the table cold section; C Such programs generally can be applied to a higher cleanliness as one hundred, one thousand or ten thousand. one hundred thousand and other lower purification clean workshop.
(2) pressurized water-cooled units + cabinet + HEPA air
Compared with the first option, which is relatively simple air conditioning program. It can greatly reduce the engine room area, water Guiji may be arranged in accordance with the specific situation within a small room or purifying workshop, pressurized air cabinet may be arranged in the engine room or hanging in the room or in a sandwich.
Advantages:. A better air handling and air treatment after the process of being low in air pollution levels. Supply air temperature and humidity control effect can be achieved better control. The main control in the air handling units (pressurized air cabinet) years;. B flexible arrangement. Comes the cold source;. C size plant, the old and new factories are applicable;. D low frequency of maintenance;. E low floor noise.
The disadvantage: A .. need a small area of the room. The need for cooling towers, the placement of the cooling water pump;. B air conditioning units and air handling units to concentrate arrangement;. C low cost. Features: This program may be a return air can also be secondary air, as per the size of the workshop situation to be; such programs are generally applicable to the cleanliness of 1,000, 10,000, 100,000 and other purification clean plant.
2. Split air condition + FFU delivery outlet
This is the easiest one air conditioning program. It is directly arranged split air condition in the workshop, and with the color steel envelope up in Guiji back again in the Color panel outlet open return air (with the early effect of the filter); FFU arranged uniformly in suspended ceiling. This program is suitable for indoor temperature and humidity less precision clean room.
Advantages: A does not require room area, layout is very flexible; B meet air cleanliness; C lowest cost.... As 300m2 of clean workshop takes about 400,000 initial investment;. D good air uniformity.
Disadvantages: A poor temperature and humidity control; B meet the cleanliness of the air; C.FFU of high maintenance frequency.
  to sum up
   For conventional electronic factory clean room air-conditioning design, it should be based on the production process requirements and economic conditions Party to choose which electronic factory air-conditioning design programs to meet the requirements of the production process as a prerequisite. Eradicate past experience, for demanding air conditioning program can choose to focus on modular air handling units; for less demanding, but also to the initial investment, you can choose Guiji + FFU. In short, the specific program selected according to specific circumstances.
On the selection of electronic purification plant air conditioning mode
Abstract: This paper is relatively new air unit + mixed air unit + high efficiency filter with the new air unit + dry coil + FFU both clean air-conditioning mode features, from the initial investment and energy consumption were analyzed, described the new air unit + stem coil + FFU clean air conditioning this is a realistic way, and summarizes some of the problems in the design process should be noted that based on practical experience.
Keywords: clean air-conditioning mode; the initial investment; energy consumption; realistic
Clean room environment parameters of the current electronic factory cleanroom rating majority in 1000 (ISO6 level) -10,000 level (ISO7 level), with its considerable number of ventilators on average 25-60 times / H, the required comparison strict majority requirements for the indoor temperature 22 ± 2 ℃, relative humidity of 55 ± 5%, the clean room technology equipment heat, part of the process to exclude the amount of exhaust heat required equipment is also great. Due to the requirements of high heat, resulting in consumption electronic factory clean room air conditioning system is very amazing, so early in the design of clean room air-conditioning system for the way the choice would need to be carefully considered.
According to the author's practical experience, most factories have been built in electronics, air conditioning systems clean room generally using conventional cleaning air conditioning mode --- fresh air unit + mixed air unit + high efficiency filter (HEPA), while another The new clean air conditioning mode --- + dry air unit coil + FFU (FFU is the abbreviation, called FanFilter Unit, Chinese meaning for the fan filter unit) are relatively rare, because: (1) conventional purification has been in use, do not want Update change; (2) part of the business that the new clean air conditioning system + dry air unit coil + FFU approach is used to project high purity (≥100 level) requirements, the worry for 1000 -10,000 level project will cost high. Therefore, this article focuses on the characteristics and energy consumption were two ways of analyzing air conditioning investigate, explain the new air conditioning system clean dry coil units + + FFU manner in electronic factory is indeed feasible, and summarizes this approach in the design of clean air conditioning Some problems need attention in the process.
One or two ways of analysis and comparison of clean air-conditioning
1.1 The new air unit + mixed air unit + high efficiency filter (HEPA) air conditioning way of introduction
The air-conditioning mode refers to the outdoor fresh air after a new air unit process into the mixed air unit, mixed air units the return air and fresh air are mixed and processed into the air parameters required for direct use of air duct to each terminal efficiency filter ( HEPA), usually the new air unit will handle new to indoor air enthalpy, does not bear the indoor load, bear only new wind load borne by the mixed air unit indoor moisture load and sensible heat load, air-conditioning mode is shown in Figure 1.

1.2 The new air unit + + FFU dry coil air conditioning way of introduction
The so-called dry coil, because in such a system freeze coil sensible heat load to bear only its chilled water inlet temperature is generally above 13 ℃, which means that the indoor air temperature above the dew point, the coil is generally impossible to produce condensate, below dry condition, so it is called dry coil, while chilled water 13 ℃ commonly used method of preparation for the use of water - water plate heat exchanger of the chiller 7 ℃ / 12 ℃ chilled water conversion over . The so-called FFU, Chinese meaning for the fan filter unit, or rather is a self-powered, highly efficient modular filtering end blowing means, many purification equipment manufacturers have detailed description of FFU, not repeat them here . New air handling units + dry coil + FFU air conditioning mode refers to the outdoor fresh air after a new air unit process fed into the ceiling technical dissection of the clean room, dry coil handles air to the required parameters, and then use the FFU to circulate the air so as to achieve ventilation cleanliness requirements, usually the new air unit will handle new air to the indoor dew point temperature, undertake new wind load and indoor moisture load, dry indoor coil sensible heat load to bear, FFU and filter the air circulating load. That humidity from the new air unit responsible for the dry coil temperature is responsible responsible for the cleanliness of the FFU

 
1.3 Both the initial investment relatively clean air conditioning mode
Some companies believe that the new air unit + dry coil + FFU purification purify air conditioning than the initial investment in conventional manner to be higher, we are compared as follows:
(1) Due to the dry coil and FFU manufacturing technology development and popularization of the manufacturer of rapid growth, prompting their prices have dropped significantly compared to previous years, the brand choice is much more open, not only to foreign imported products, And many domestic manufacturers of new products also can choose;
(2) The new air unit + dry coil + FFU purification compared to conventional purification methods, the air conditioning wind cabinet specification only small new air handling units, air units are not vague, so air conditioning wind cabinet housing area can be reduced accordingly, saving the architectural space, and the new cleanroom ceiling duct occupy less space, saving the ceiling space;
(3) compared to conventional purification methods, new air unit + dry coil + FFU purification technology the use of mezzanine ceiling, so its price in the envelope structure will be slightly higher;
(4) Compared to conventional purification methods, new air unit + dry coil + FFU purification due to less overall electrical power, so its use in smaller air conditioning power distribution wire and cable type, switch and inverter, etc. can also narrow model, cost decrease;
The amount of air pipe (5) new air unit + dry coil + FFU of purification needed is very small, only fresh air units new wind pipe, and pipe the amount of air required in the conventional purification on a lot, which includes The new wind blowing tube unit, mixed air unit air duct and a return duct (both large-size duct). Overall, the new wind generating units + dry coil + initial investment FFU of purification with initial investment of conventional purification was essentially flat.
1.4 Both energy consumption relatively clean air conditioning mode
Comparison of energy consumption is mainly reflected in terms of electricity consumption, including new air unit + dry coil + FFU purification of electricity include: fresh air units, FFU, dry coil pump three areas. The conventional purification methods using electricity including: new air unit, mixed air units. As can be seen, the two systems is that the comparison between the FFU + pump and mixing dry coil air handling units, you can clearly see that the mixed air unit's electricity consumption will be much higher, because the power of the individual FFU at around 0.2kw , while dry coil pump is a small water pump, power is not large, the two devices combined electricity consumption much. The mixed air units of conventional purification treatment cycle air volume due to the need of the whole system, but also the burden of end resistance high efficiency filter, return air duct of resistance, which will have tens of kilowatts of power easily, so run a conventional purification methods cost is considerably higher than the new air unit + dry coil + FFU purification methods. Generally believed that new air unit + dry coil + operating costs of FFU purification is about 60% of the conventional purification methods --- 80%.


Second, the new wind generating units + dry coil + FFU clean air conditioning way of practical feasibility
From the above comparison, we can see: The new air unit + dry coil + FFU clean air-conditioning mode of the initial investment is not necessarily better than fresh air unit + mixed air unit + high efficiency filter high initial investment is the conventional way of cleaning air conditioning, If properly designed, the initial investment is often flat and conventional purification methods, but then consider electronic purification plant in the share of electricity consumption in air-conditioning system is great, a purification of air-conditioning mode selection emphasis should be placed on energy consumption at the number of classes and the use of the clean room is basically the number of classes of continuous, clean air-conditioning equipment are long-running, so choose low-energy purification methods are realistic, often a low-power purification within two to three years You can put up that part of the initial investment back completely save. Therefore, the new wind generating units + dry coil + FFU clean air conditioning this way is worthy of promotion and practiced.
Third, the new wind generating units + dry coil + FFU purification of air conditioning way some of the issues in the design process that need attention
New air handling units + dry coil + FFU clean air conditioning mode with the design in a conventional manner substantially the same, whether it is indoor load calculation, decontamination cycle air volume selection, positive pressure air volume selection, humidification choices are similar, there are many papers In this regard the design details, the author focuses on a number of issues here to mention the need for special attention:
(1) new wind new air handling unit enthalpy difference is large, the air temperature is lower after treatment, run under cold water temperature is usually necessary to increase the number of rows of coils to increase the heat transfer area, so the new air unit coil exhaust pipe exhaust pipe coil number than the number of conventional ways to be more, and post-processing low air temperature, insulation thickness insulation thickness of new housing units and new air duct than the thickness of a conventional manner to be thick;
(2) run dry coil dry conditions when the water temperature is to be based on room air dew point temperature is determined, not a fixed value, the actual temperature and humidity need to follow the requirements of the clean room is determined, and in different conditions under cold dry coil it is varied, but most coil manufacturer of the product specification standard conditions only mention cold, but dry coil operation is in non-standard conditions, so pay special attention to the amount of dry cooling coil values, can be calculated by the method of presentation of the relevant papers, or to provide non-standard conditions of cold magnitude by the coil manufacturer;
(3) Use this clean air conditioning mode, if partial purification zone room temperature and humidity conditions are different, or different partial heat process equipment in the room, it must cut off the local separate room, and then set a separate air-conditioning system independent temperature and humidity control, so set up and running to help control energy saving precision temperature and humidity;
(4) According to the design theory, dry coil is running in the dry conditions, there will be no condensation of water, but a purification of the room when the air conditioner just getting dry coil entering the normal dry conditions within that period of time before the operation in wet condition, even if the condensation of water rarely, it is recommended to set the condensate drain pan and ensure that no drip leakage, and if dry coil needs to be cleaned or emptied, there are drainage Facilities available to set the condensate drain pan and the cost is not high, so try to consider setting the condensate pan and drain;
(5) When a large area of the room using the new air purification unit + dry coil + when FFU clean air-conditioning mode, FFU use than more, separately one by one to manage control is very convenient, in order to facilitate the management, we recommend using FFU group control This new management techniques, which can be observed on the computer to run the FFU, stop, fault and other state, can also be open stop, speed and other control on the computer, it can greatly reduce the management of FFU the amount.
IV Conclusion
Due to the rapid development of electronic circuit industry, the use of the clean room will be more extensive, and clean air-conditioning mode selection is especially important, since the conventional system (fresh air unit + mixed air unit + high efficiency filter) exists energy consumption high, building space require large, multi-line cross and other shortcomings, we have reason to recommend the use of new clean air conditioning mode (fresh air unit + dry coil + FFU), the energy saving effect is significantly better than conventional systems, building space requirements, pipeline not much, and the total cost and the cost of conventional systems has been little difference, I believe that in the near future will be lower, so the new air unit + dry coil + FFU clean air conditioning embodiment is as feasible.
With the development of air-conditioning technology, clean air-conditioning design approach inevitably more, as long as we understand the system, and carry out research, I believe that electronic factory clean air-conditioning mode selection will be constantly updated, and can continue to improve, it is possible further to reduce energy costs.
reference
[5] Xu Zhonglin clean air technology principles, the third edition of Beijing: Beijing Science Press, 2003
[6] The design and construction of Beijing Chen Lin new clean room: Chemical Industry Press, 2002
[7] Yan Delong cleanroom technology in some hot spots of current clean and air-conditioning technology, 2002, (4)
[8] Ni Meiqin, PROPULSION, research HVAC cold calculation runtime Xie Zhixiang Dry Coil Condition method 2008 Vol. 38, No. 8
[9] Chang-electronic industry clean dry coil air conditioning systems ---- FFU Building Energy, 2005, (2)
[10] air-conditioning design manual (second edition) Beijing: China Building Industry Press, 2004