Air Washer Unit

Air Washer Unit Selection Tips :

An air washer unit is an appliance that sprays water into the stream of air to cool it down. Air washers can be standalone equipment or part of the AHU and other AC systems.

Air washer units are available in both apartment and industrial models and come with horizontal or vertical configurations and air supply directions. They may also be equipped with a heating coil.

Air washers can be used in most regions throughout the Middle East with a dry summer (relative humidity below 40–45%).

Given that the cooling function of air washer units is based on evaporation (similar to evaporative cooling), they are not expected to provide intense cooling, such as with vapor compression, absorption, ducted split, or mini-split systems.

Some manufacturers have recently offered combination systems that couple the air washer with vapor compression cooling according to the requirements of their customers. This design allows for reducing the water temperature and adjusting the output air temperature.

Air Washer Unit Operating Mechanism :

• The hot summer air enters the equipment by the air washer fan. Using their powerful water pumps and nozzles, air washers spray the stream of air with water droplets that remove dust and particulates, supplying a cool, clean flow of air. Dust removal and heat exchange between the air and water droplets provides a clean and cool air supply for the summer.

Important Parts of the Air Washer Unit :

• Air washers can be used as standalone equipment or in combination with other parts of the AC system and consist of the frame, the electric motor, fan, air purification filter, nozzles, water pump, basin, air diffuser, heating coil, and eliminator blades.
  
  

Advantages of the Air Washer Unit :

1. Optimal power consumption and lower utility costs (electricity in the summer and gas in the winter) in comparison to vapor compression systems;
2. Optimal water consumption in comparison to evaporative coolers;
3. Humidification of the air supplied to the building in dry summer weather;
4. Significantly lower maintenance and replacement part costs relative to air conditioning and chiller systems;
5. No need for radiator water risers and pipes running under the floor, and no need for thick flooring, all of which reduce the dead weight;
6. Efficient use of the wasted space above the drop ceiling for distributing air through the duct system;
7. The possibility of installing the air washer as a centralized unit in the wasted building spaces and the facility of access for maintenance;
8. Control over temperature and humidity and using fresh outdoor air in the summer and the winter;
9. Using single-phase power (in particular, for apartment systems) Most vapor compression systems (such as AC) of over 36,000 BTU use three-phase power. That is, for example, for an apartment with over 100 square meters of floor area, three-phase power is required for using mini-split or ducted split systems. However, by using the air washer system, even for apartments as large as 300 square meters there is no need for three-phase power.
10. Low initial investment, especially for large spaces.
11. The larger the building and the space, the wider the difference between air washer (Zent) and vapor compression systems in initial investment and power and energy costs. For example, heating and cooling large spaces—such as mosques, halls, factories, and industrial facilities—using vapor compression systems—such as packaged units or chillers—is highly expensive in both initial investment and operating costs. Meanwhile, implementing an air washer systems of similar capacity will cost as low as one-tenth of a vapor compression system.
12. Air washer units are rapid in providing heating and cooling, that is they are best fit for spaces that are not used continuously (such as schools, mosques). Further, in residential buildings, the system does not require to remain functioning when the occupants leave, which reduces energy consumption. The system is also capable of distributing heated and cooled air evenly throughout the building.
13. Less hassle and reduced maintenance costs thanks to the centralization of several heating and cooling units (radiators and fan coil units);

Disadvantages of the Air Washer Unit :

• The air washer (Zent) unit does not provide as high-quality cooling as air conditioning, ducted split, or chiller systems. In particular, at extremely hot hours during the day or in cities with hot climates, the cooling efficiency of the equipment will be reduced;
• The use of water complicates the maintenance;
• Air washer—and Zent—systems are not suitable for cases with a considerably high latent heat (such as cooking places, crowded environments, or basically, anywhere where water vapor is present);
• The system cannot be expected to provide effective cooling in hot and humid regions (such as the northern and southern Iran);
  
  

When selecting an air washer unit note the following in addition to the capacity (CFM, m³/hr) :

• The required capacity, motor power, and static pressure;
• Horizontal or vertical air supply;
• Horizontal or vertical equipment configuration;
• Whether the system is equipped with a heating coil, its capacity and heat transfer surface area;<
• Location and the installation conditions of the air washer;
• Accurate calculations and the correct implementation of the air washer duct system (consult the descriptions provided under Ducts and Vents section in the Air Conditioning Equipment category).
  
  

Other Technical Aspects of Air Washer units :

Dehumidification: Dehumidification is only possible in air washers when the sprayed water is at a lower temperature than the input air. The colder the water spray, the more efficient it is in dehumidification, and the cooler the air supply.

Corrosion Control in Air Washers: Corrosion control is an integral part of operating systems where both metals and water are present. Carbon dioxide, sulfur dioxide, and other corrosive gases can be detrimental when dissolved in water. Together, these agents produce a dilute, mild acid that results in the corrosion of the unprotected surfaces. One manifestation of this phenomena is pressure drop at the nozzles. To solve this problem, the metal surface is coated with a corrosion inhibitor that increases pH up to nearly 9, thus neutralizing the acid and hindering bacterial growth.

Lint and Oil Vapor Control in Air Washers Oils that are present in the air are generated by the high-speed operation of machinery and interrupt the function of the system. This issue can be resolved by oil separators that separate grease from sludge and dirt, making it afloat to be removed by overflow. If oil remains in the system, it can accumulate to the point of forcing the system to shut down.

Odor Control in Air Washers Air washers exhaust air which will be inhaled by people, as a result, the output air must be clean, pollutant-free, and odorless. Air washers become slimy and odorous very quick. To resolve this problem, low-odor oxidizers such as hydrogen peroxide and bromine are injected into the air washer two times a week.

Conclusion Evaporative systems such as air washers and Zent are suitable for arid climates. The systems are the best fit for large buildings with high ceilings such as mosques and industrial facilities and are more economically efficient in comparison with vapor compression cooling systems (AC and chiller). The power costs are as low as a quarter of that with air conditioners and vapor compression chillers.

Placing an Order and Warranties Air Washer Unit

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1M3 =35.315 Ft.3
1KCal =4 BTU
1 Atm. =14.7 P.S.I
1 GPM X 0.2271 = 1M3/hr
12000 BTU = 1 Ton of Ref.
1M3/hr =0.588 CFM