Where is it better to position the evaporative cooler, upstream or downstream of the dry filters …?
The wetted media evaporative cooler is a very effective and efficient filter. It will trap 87% (prox) of particulate down to 10 micron size. The face area required to control air velocity is another important consideration. For these 2 reasons, it is far better to position the wetted media type evaporative cooler upstream of the dry filters. Dry filter useful life is also greatly extended and maintenance costs are likewise reduced when using the evaporative cooler as a pre-filter as well as a cooler. Moisture carryover is not a consideration because there will be no raw moisture entrained in the air stream from a properly designed and sized wetted media cooler. Mechanical installation of the system on retrofits is also simplified. Conversely there are disadvantages in downstream placement of the cooler. It is difficult to control air velocities uniformly across the face area of the media and the advantages of pre-filtering are lost.
