Indirect evaporative cooling heat exchanger

Abstract

A heat exchanger including a header having a plurality of header openings with rigid tubes that may be made of plastic are inserted in the openings. The tubes are sealed to the header to prevent leakage between the header and the tubes to prevent water and air leakage between the wet, scavenger air stream flowing through the tubes and a dry air stream flowing around the tubes. A method of making the heat exchanger includes providing the openings with a flange and uses an interference fit between the rigid heat exchange tubes and the header openings. A self-leveling sealant may be used to seal the heat exchanger tubes to the header using, for example, a paint roller and/or a paint sprayer.

What is claimed is: 
     
       1. A method of sealing a plurality of rigid tubes to a metal header having a plurality of openings therethrough, comprising:
 forming a flange into each of the openings in the header; 
 inserting the rigid tubes into the openings in the header, the header having an exterior surface and an interior surface and the rigid tubes having a top portion and a bottom portion, the rigid tubes are inserted with the bottom portion first, and are placed into the openings of the header so that the top portion of the rigid tubes are substantially flush with the exterior surface of the header; and 
 applying a sealant to the exterior surface of the header and the inserted rigid tubes by an absorbent applicator and/or a spray applicator. 
 
     
     
       2. The method of  claim 1 , wherein applying the sealant includes rolling an adhesive over the header. 
     
     
       3. The method of  claim 1 , wherein at least one groove is provided in the tubes. 
     
     
       4. The method of  claim 1 , wherein an end surface of the rigid tubes is angled with respect to a bottom end portion of the rigid tubes. 
     
     
       5. The method of  claim 1 , wherein an end surface of the rigid tubes has a compound angle with respect to a bottom end portion of the rigid tubes. 
     
     
       6. The method of  claim 4 , wherein the end surface of the rigid tubes is angled at approximately 20 to 30 degrees from the horizontal. 
     
     
       7. The method of  claim 1 , wherein the sealant is a self-leveling adhesive. 
     
     
       8. The method of  claim 1 , wherein the flange extends in a direction perpendicular from the exterior surface of the header. 
     
     
       9. The method of  claim 1 , further comprising providing each of the openings with a flange before inserting the rigid tubes,
 wherein the flange extends in a direction perpendicular from the substantially uniform exterior surface of the header. 
 
     
     
       10. The method of  claim 1 , further comprising providing each of the openings with a flange before inserting the rigid tubes,
 wherein the flange extends in a direction perpendicular from the substantially planar exterior surface of the header. 
 
     
     
       11. A method of operating a heat exchanger, comprising:
 evaporatively cooling a plurality of rigid tubes by contacting the rigid tubes with water and a first air stream to cause water evaporation;   cooling air by contacting a second air stream with the evaporatively cooled rigid tubes to cool the air of the second air stream; and   causing the rigid tubes to expand and contract within a predetermined range to separate solid deposits accumulating on the rigid tubes as a result of water evaporation by changing a pressure of the rigid tubes by varying a speed of air contacting the rigid tubes,   wherein ends of the rigid tubes are sealed in a leak tight manner to openings formed within a header of the heat exchanger.   
     
     
       12. The method of claim 11, further comprising:
 collecting solid deposits separated from the plurality of rigid tubes in a sump; and   flushing the solid deposits from the sump.   
     
     
       13. The method of claim 11, wherein the plurality of rigid tubes are formed from a plastic material. 
     
     
       14. The method of claim 13, wherein the plastic material comprises polyvinylchloride. 
     
     
       15. The method of claim 11, wherein the plurality of rigid tubes comprise corrosion resistant polymers having a fire and smoke retardant rating that meets or exceeds UL94 V-O or V-l rating. 
     
     
       16. The method of claim 11, wherein the expansion and contraction of the plurality of rigid tubes within the predetermined range is caused by changes in an internal pressure of the plurality of rigid tubes. 
     
     
       17. The method of claim 16, wherein the changes in the internal pressure of the plurality of rigid tubes are caused by varying a speed of the air flowing through an interior of the plurality of rigid tubes. 
     
     
       18. The method of claim 16, wherein the changes in the internal pressure of the plurality of rigid tubes are in a range of up to 0.5 inches of water column pressure. 
     
     
       19. The method of claim 11, wherein the predetermined range is up to 0.025 inches. 
     
     
       20. The method of claim 11, wherein the plurality of rigid tubes have a wall thickness of about 0.020 inches. 
     
     
       21. The method of claim 11, wherein the plurality of rigid tubes have an internal web structure to flexibly maintain tube dimensions, and to maintain the expansion and contraction of the plurality of rigid tubes within the predetermined range. 
     
     
       22. The method of claim 11, wherein the plurality of rigid tubes are sealed to the header by an adhesive. 
     
     
       23. The method of claim 11, wherein the plurality of rigid tubes are sealed to the header by a self-leveling liquid. 
     
     
       24. The method of claim 11, wherein the plurality of rigid tubes include grooves formed on the internal surface to provide increased surface area and reduce thermal resistance. 
     
     
       25. The method of claim 11, wherein individual tubes of the plurality of rigid tubes have openings at both ends. 
     
     
       26. The method of claim 11, wherein the water and first air stream flow in opposite directions. 
     
     
       27. The method of claim 11, wherein the plurality of rigid tubes are non-cylindrical tubes. 
     
     
       28. The method of claim 27, wherein the non-cylindrical tubes are ovoid tubes. 
     
     
       29. The method of claim 11, wherein the method is performed within an evaporative cooling unit including the heat exchanger, and the evaporative cooling unit provides water and air to the heat exchanger. 
     
     
       30. The method of claim 29, wherein the evaporative cooling unit is an indirect evaporative cooling unit. 
     
     
       31. The method of claim 29, wherein the evaporative cooling unit is an indirect/direct evaporative cooling unit that comprises a direct cooling stage.