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Technical information Air-Conditioning Air filtration

Air filtration

Ambient air contains many of the solids, ranging from grains down to a fine dust, fumes and vapours. The air conditioning system will eliminate some of these funds, depending on the application. There are three reasons for the filtration of air:
  1. To remove impurities, which can harm the process, for example. dust in the computer room bacteria in pharmaceutical packaging room.
  2. For the comfort of the residents and purity documents and furniture.
  3. Keep it inside air conditioning apparatuses and pipelines clean.
Impurities can be classified by size:
  • Pollen 9-80 um
  • Mould spores 3-50 microns
  • Fine ash 0.7-60 microns
  • Bacteria 1-10 microns
  • Tobacco smoke 0.1-7 microns
  • Viruses to 0.1 microns
Filtration apparatus for removal of any size, but very small particles, requiring deep, bulky and expensive filter that sets a high resistance to air flow and, consequently, requires high power of the fan. Practical balance must be achieved to satisfy the requirements of:
  1. To remove the high proportion of impurities in the air.
  2. Spend a great weight of dust, before having to be removed or replaced, so as to reduce the frequency of service to an acceptable level (i.e..

    if maintenance is required too often, it can be neglected).
  3. The filter must be washable or cheap enough to replace.
A high proportion of the mass of dust and lint in the air in large particles, and therefore quite easy to trap. Filters for General-conditioning duties are felt, glass or other fibers used in dry conditions and is characterized as " an attack filters . Air passes through the fibers vibrant, and dust particles strike fibers and stick to them. The filter material can be flat, but, as a rule, grooved, with a view to presenting a large surface area within the specified area of the face. A typical filter in comfort air-conditioning system 50 mm in depth and can collect 95% or more of impurities in the air, up to the amount of 1 hour of the day.

Increased capacity can be obtained by making the filter material in a series of bags, which are usually about 400 mm in depth, but are also made to 900 mm, where the maximum possible preservation of the capacity required. Some of bag filters are shown in Fig. 24.20.

More subtle filtering is possible, down to 0.01 micron. These filters are used only when this process requires a high standard. These filters can clog quickly, with normal size impurities, so they tend to have more coarse filter upstream to take more dust. They are about 300 mm in depth, and require special mounting frames, so the dirty air cannot escape on the edge.

Very fine particles such as smoke can be caught by electrostatic precipitation. High voltage is applied to the plates or wires within the filter Bank, to give a static charge dirt particles. They will be brought to a grounded plates, and stick to them. Impurities usually cleaned off the plates, removing stack and washing.

Electrostatic filters will not detention of large particles, and should be supported by more rough attempt filters for this purpose. As the filter element collecting dust, air resistance through it will grow to the point where the system airflow has been violated. Users must have an objective sign of this limit and all filters except those on small package units must be fitted with pressure gauges (see Fig. 24.2) . On installation, the signs shall be set to indicate the " clean " and " dirty " resistance pressure levels.

Dry blow filters cannot be effectively cleaned and, as a rule, will be replaced when dirty. Fine filters of this type are used on some package air conditioners, and much of the dirt can be removed by shaking or vacuum cleaner. The problem of air filtration on the small complex systems is the low fan power available and the possible neglect of maintenance. Because users will be reluctant to purchase new filters if necessary, some forms of cleanable filter works. One such type is foam. Where replacement filters are used, it is good practice to always have a full set of spare ready to paste, but also order a set when they are used. This allows to avoid the inevitable delays that will occur if the new filters will not told until the case is urgent.

The air filters are not used for cold warehouses, refrigerators, because the air is much cleaner and a small amount of dust is washed away fins condensate or thawed frozen. Air-cooled condensers are not installed filters, as experience shows that they will never be supported properly. In dusty areas, capacitors must be selected with a wide step edges, so that they can be easily cleaned...

 
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