Mechanical Engineering(HVAC)

Air washing?

Do you mean filtration?

Check out: Flanders, american standard air filters, or FARR

http://www.flanders-csc.com/

http://www.americanstandardair.com/HomeOwner/LatestUpdates/AccuClean.aspx

http://www.donaldson.com/en/engine/support/datalibrary/000622.pdf

Air washers function by evaporating water over a wet "wall". Since only the H2O will evaporate, your water will increase in conductivity (dissolved solids) as the run time accumulates. This must be controlled in the same manner as a cooling tower. Consider both pH control and solids control. The pH can be adjusted with acid addition, and "blowing down" or draining high conductivity water and replacing with fresh water at some rate will prevent the media from choking with calcium.

You should limit your air velocity over the media to 400 feet per minute to prevent drift off of the media.

Calculate the volumetric air requirements from your load by using the calculation:

Load (btu/hour) = CFM x 1.08 (adjust based on ambient pressure for altitudes) x Delta-T (air inlet T °F - air out T °F).

You calculate the amount of cooling you'll get by using a psychrometric chart. You must know something about the media efficiency to find out how close to the wet bulb temperature you will actually get. (For example, Munters Glas-dek 8" pads are ~80% efficient, so if you have a potential difference between ambient and wet bulb of 30°F, then your discharge temp will be 24°F lower than the air inlet. If you have a lot of calcium/magnesium, the hardness minerals, then don't use celulose (Cel-Dek) media, it won't stand up to being acid cleaned more than once, use the fiberglass media).

If your humidity is just slightly lower than you need, and the new calculated humidity is too high, you must bypass some amount of ambient air, and this will reduce your 24 degree dry bulb temperature change from the example. Let us know if you would like help on the humidity calculations. For these you must know how much dry air mass is being processed by the system.

Hope this helps.

Don

Great reply Don.

I don't know if it helped the OP; but it sure helped me.

Thanks!

Why, thank you Swellmel.

I only hope it helped solve the originator's problem.

Don