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.

Description

The tubes 40 may individually have two opposing planar major walls connected to each other by two opposing rounded minor walls. A web 90 may be formed at the center of the chord length. The web 90 is formed transverse to the narrow, elongated portions of the tube 40 and connects the sides of the tube 40 at the center of the cord length. In the exemplary embodiment, the tubes 40 may range in length from about 24 to about 96 inches, with the most common length being about 48 inches in length. In such an exemplary embodiment, the exchanger would have approximately 144-1000 tubes disposed therein. Although this exemplary embodiment includes the description discussed above, tubes 40 having other dimensions are contemplated.

In an exemplary embodiment of the invention, the web 90 aids in maintaining the dimensions of the tube 40 during handling and assembly of the heat exchanger 10. For example, the web 90 aids in maintaining the dimension of the width of the tube 40 as the tube 40 is inserted into the header 30. If the web 90 were not in place, the tube 40 would tend to draw up on its center and result in a tube width of less than the desired 0.375 inches of the exemplary embodiment, thus causing problems with sealing the tube 40 to the header 30. The result of not completely sealing the tube 40 to the header 30 is unwanted air and water leakage between the dry supply second air stream 11 and the wetted, humid exhaust/scavenger first air stream 9.

In an exemplary embodiment of the invention, the tubes 40 may include a plurality of grooves 80 formed on an inner wall surface of the tubes 40. The grooves 80 aid in wetting the inner surface of the tubes 40 by causing the water from the water distribution manifold 8, through the header openings 50, to fully wet the inner surface by capillary action. The grooves 80 also provide a greater surface area from which water may evaporate to aid in increasing cooling efficiency. Additionally, because the grooves 80 are formed in the inner wall surface of the tubes 40, a thinner net wall thickness is achieved through which energy that is to be transferred encounters less thermal resistance to energy flow. The grooves 80 also allow the tubes 40 to have a greater structural rigidity, thereby preventing ballooning or collapsing of the tubes 40 as a result of fan pressure when the air intake fan 4 provides air flow through the exchanger 10.

In an exemplary embodiment of the invention, the walls of the tube 40 are designed with a strength that allows for a determined amount of transverse wall movement, or flex. For example, a determined amount of transverse wall movement, i.e., on the order of 0.025 inches, occurs in the tube wall when the pressure in the tube 40 is raised to 0.5-inches of water column pressure. As a result of such determined transverse movement, any solid deposits, such as mineral deposits or contaminant build-up on the inner surface of the wall, are separated from the wall surface when the pressure changes sufficiently to cause wall flex. For example, a sufficient pressure change may result when the fan 4 that blows air through the heat exchanger 10 is turned on or off. The deposits drop into a water sump (not shown) disposed at the base 2 of the unit 1 and are flushed from the system on a regular basis.

FIG. 8 is a flow chart showing an exemplary method of assembly of an IEC heat exchanger according to the invention. The method of manufacturing a heat exchanger begins in step S1000 and proceeds to step S1010 where rigid heat exchanger tubes made, for example, of a suitable plastic material, are formed. As noted above, in one exemplary embodiment, the tubes have an ovoid shape. Then, in step S1020, a rigid heat exchanger header is formed which has a relatively flat surface containing openings. Next, in step S1030, each opening is provided with a flange to accommodate a rigid heat exchange tube snugly. Next, in step S1040, one or more grooves are provided in the flange. Then, in step S1050, an heat exchange tube is interference fit into each header opening. Next, in step S1060, the edge of each heat exchange tube is made flush with the exterior surface of the heat exchange header. Then, a sealant is applied to the header with inserted heat exchange tubes. Then, the process ends in step S1080. As noted above, a sealant may be applied using a paint roller and/or a paint sprayer, to reduce the manufacturing time of the IEC heat exchanger.

FIGS. 9A-9C show an exemplary embodiment of a tube having an angled bottom portion. In an exemplary embodiment of the invention, the tubes 40 are angled at a bottom end portion so that the tubes 40 may be more easily inserted into the openings 50 of a lower header plate 100 and intermediate spacer plates (not shown). The tubes 40 may be angled both longitudinally and transversely at a cut on the bottom end portion of the tubes 40. By having a compound angle cut on a bottom end of the tubes 40, the tubes 40 may be more easily aligned with openings in the lower header 100 having an opening in its surface that has a perimeter shape of the same dimension as the tubes 40. The compound angle cut allows the tubes 40 to be guided to the openings in the lower header 100 and then press-fit into the lower header 100. The tubes 40 may be cut during or after manufacture of the tubes. In an exemplary embodiment, the tube 40 has an angle that is approximately 20-30 degrees from the horizontal. Tubes having cuts forming other angle measurements are also contemplated by this invention.

While the invention has been described in conjunction with exemplary embodiments, these embodiments should be viewed as illustrative, not limiting. Various modifications, substitutes, or the like are possible within the spirit and scope of the invention. For example, the invention may be used with or without direct evaporative coolers.

Claims

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 heat exchanger for an indirect evaporative cooling unit, comprising:

a header having a plurality of openings penetrating the header; and

a plurality of rigid plastic tubes inserted in the openings in the header, ends of the plurality of rigid plastic tubes being sealed in a leak tight manner to the header,

wherein the plurality of rigid plastic tubes are each configured to expand and contract within a predetermined range to separate solid deposits accumulating on the plurality of rigid plastic tubes.

12. The heat exchanger of claim 11, wherein the solid deposits are the result of evaporation of water on the plurality of rigid plastic tubes.

13. The heat exchanger of claim 11, wherein the separated solid deposits are deposited in a sump that is routinely flushed to remove the separated solids from the heat exchanger.

14. The heat exchanger of claim 11, wherein the expansion and contraction of the plurality of rigid plastic tubes within the predetermined range is caused by changes in an interior pressure of the plurality of rigid plastic tubes.

15. The heat exchanger of claim 14, wherein the changes in the interior pressure of the plurality of rigid plastic tubes are caused by changes in a speed of the air flowing through an interior of the plurality of rigid plastic tubes.

16. The heat exchanger of claim 14, wherein the changes in the interior pressure of the plurality of rigid plastic tubes are in a range of up to 0.5 inches of water column pressure.

17. The heat exchanger of claim 11, wherein the predetermined range is up to 0.025 inches.

18. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes have a wall thickness of about 0.020 inches.

19. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes have an internal web structure to flexibly maintain tube dimensions, and to maintain the expansion and contraction of the plurality of rigid plastic tubes within the predetermined range.

20. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes are sealed to the header by an adhesive.

21. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes are sealed to the header by a self-leveling liquid.

22. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes include grooves formed on an internal surface to provide increased surface area and reduce thermal resistance.

23. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes comprise polyvinylchloride.

24. The heat exchanger of claim 11, wherein the plurality of rigid plastic tubes comprise corrosion resistant polymers having a fire and smoke retardant rating that meets or exceeds UL94 V-O or V-1 rating.

25. An indirect evaporative cooling unit including the heat exchanger of claim 11.

26. An indirect/direct evaporative cooling unit including the heat exchanger of claim 11.

27. A heat exchanger for an indirect evaporative cooling unit, comprising:

a header having a plurality of openings penetrating the header; and

a plurality of rigid plastic tubes that individually have two opposing planar major walls connected to each other by two opposing rounded minor walls, the plurality of rigid plastic tubes being inserted in the openings in the header, and ends of the plurality of rigid plastic tubes being sealed in a leak tight manner to the header,

wherein the plurality of rigid plastic tubes are each configured to expand and contract within a predetermined range to separate solid deposits accumulating on the plurality of rigid plastic tubes.

28. An evaporative cooling unit comprising:

a base;

a frame supported by the base;

a heat exchanger within the frame, the evaporative cooling unit being configured to provide water and air to the heat exchanger;

a fan configured to intake air into the evaporative cooling unit; and

an exhaust configured to exhaust air from the evaporative cooling unit,

wherein the heat exchanger comprises:

a header having a plurality of openings penetrating the header; and

a plurality of rigid tubes inserted in the openings in the header and ends of the plurality of rigid tubes being sealed in a leak tight manner to the header, the plurality of rigid tubes each being configured to expand and contract within a predetermined range to separate solid deposits accumulating on an internal or external surface of the plurality of rigid tubes.

29. The evaporative cooling unit of claim 28, wherein the evaporative cooling unit is an indirect evaporative cooling unit.

30. The evaporative cooling unit of claim 28, wherein the evaporative cooling unit is an indirect/direct evaporative cooling unit that further comprises a direct cooling stage.

31. The evaporative cooling unit of claim 28, wherein the plurality of rigid tubes are open to the environment within the evaporative cooling unit.

32. The evaporative cooling unit of claim 28, wherein the rigid tubes are rigid plastic tubes.