Indirect evaporative cooler

Claim 2

An indirect evaporative cooler comprising: a plurality of heat transfer tubes formed of thin-walled tubing having an internal fin mounted therein with each internal fin formed with accordion-like pleats bonded to an inside wall of the tubing by a distortion fit between a sharp folded edge of the internal fin and compression loads from distorting the thin-walled tubing; means for cascading water over an exterior surface of the heat transfer tubes; means for directing a scavenger air flow through the cascading water for evaporation; and means for directing dry air to be cooled through the heat transfer tubes.

Claim 3

The evaporative cooler as recited in claim 1 and wherein: the heat transfer tubes are assembled in a closely spaced matrix of vertically staggered rows whereby a serpentine flow of scavenger air is provided and reservoirs of water form between adjacent heat transfer tubes.

Claim 4

The evaporative cooler as recited in claim 1 and wherein: each heat transfer tube is formed by distortion fitting an internal fin into a thin-walled tubes by forming the internal fin with pleat lengths greater than an inside diameter of the thin-walled tube and by applying a side load to the plastic tube during assembly.

Claim 5

The evaporative cooler as recited in claim 1 and wherein: the heat transfer tubes are formed of thin-walled plastic tubing with metallic fins therein.

Claim 6

The evaporative cooler as recited in claim 1 and wherein: the heat transfer tubes are mounted and sealed to tube sheets.

Claim 7

In an indirect evaporative cooler, the improvement comprising: a heat exchanger formed of a plurality heat transfer tubes formed in a matrix of vertically staggered rows and including: a. a plurality of thin-walled plastic tubes having an inside diameter; b. a plurality of metallic fins formed with accordion-like pleats having sharp folded edges with the metallic fins having pleat lengths greater than the inside diameter of the plastic tubes and with a compressive load applied to the thin-walled plastic tube during assembly for inserting the metallic fins to produce a compression fit between the metallic fins and plastic tubes whereby a thermally conductive bond is formed between the sharp folded edges of the internal fins and the thin-walled plastic tube.

Claim 8

In an indirect evaporative cooler, the improvement comprising: a heat exchanger formed of a plurality heat transfer tubes formed in a matrix of vertically staggered rows and including: a. a plurality of thin-walled plastic tubes having an inside diameter; b. a plurality of metallic fins formed with accordion-like pleats having sharp folded edges with the metallic fins having pleat lengths greater than the inside diameter of the plastic tubes and with a compressive load applied to the thin-walled plastic tube during assembly for inserting the metallic fins to produce a compression fit between the metallic fins and plastic tubes whereby a thermally conductive bond is formed between the sharp folded edges of the internal fins and the thin-walled plastic tube.

Claim 9

An improved indirect evaporative cooler as recited in claim 6 and wherein: the heat transfer tubes are formed in a matrix wherein air flow is directed between the heat transfer tubes in a serpentine direction and in which the heat transfer tubes are closely spaced to form water reservoirs therebetween.

Claim 10

An improved indirect evaporative cooler as recited in claim 7 and wherein: the internal fins include four pleats for increasing a heat transfer surface by a factor of four.

Claim 11

An improved indirect evaporative cooler as recited in claim 8 and wherein: the internal fins include an arcuate-shape pleat for contacting an arcuate internal surface of the thin-walled plastic tube.

Claim 12

In an evaporative cooler in which dry air is directed through a plurality of heat transfer tubes and water is cascaded over the heat transfer tubes for cooling the dry air, a heat exchanger comprising: a plurality of heat transfer tubes arranged in vertically staggered rows with each tube including an internal fin formed with accordion-like pleats and sharp folded edges; a distortion fit between the heat transfer tubes and internal fins formed by forming the fins larger than an internal diameter of the heat transfer tubes and by deforming the heat transfer tubes by side loading during assembly; whereby a heat conductive bond is formed between the sharp folded edges of the internal fins and the heat transfer tubes.

Claim 13

In an evaporative cooler in which dry air is directed through a plurality of heat transfer tubes and water is cascaded over the heat transfer tubes for cooling the dry air, a heat exchanger comprising: a plurality of heat transfer tubes arranged in vertically staggered rows with each tube including an internal fin formed with accordion-like pleats and sharp folded edges; a distortion fit between the heat transfer tubes and internal fins formed by forming the fins larger than an internal diameter of the heat transfer tubes and by deforming the heat transfer tubes by side loading during assembly; whereby a heat conductive bond is formed between the sharp folded edges of the internal fins and the heat transfer tubes.

Claim 14

The evaporative cooler as recited in claim 10 and wherein: the heat transfer tubes are arranged in a closely spaced matrix in which water reservoirs are formed between adjacent tubes.

Claim 15

The evaporative cooler as recited in claim 10 and wherein: the heat transfer tubes are deformed to a generally elliptical shape with the tubes arranged with a major axis of the ellipse parallel to a direction of scavenger air flow.