Method and plate apparatus for dew point evaporative cooler

• US 20030209017A1
• Filed: 03/25/2003
• Published: 11/13/2003
• Est. Priority Date: 09/27/2000
• Status: Active Grant

• Current Assignee: FF Seeley Nominees Pty Ltd.
• Original Assignee: Idalex Technologies, Inc.
• Inventors: Gillan, Alan D., Gillan, Leland E., Maisotsenko, Valeriy, Heaton, Timothy L.
• Granted Patent: US 7,197,887 B2
• Time in Patent Office: Days
• US Class Current: 62/121
• CPC Class Codes: F24F 1/0007 Indoor units, e.g. fan coil units self-contained units F24F1/02
• CPC Class Codes: F24F 1/0071 with means for purifying supplied air perfuming or deodorising means F24F1/008
• CPC Class Codes: F24F 2003/144 by dehumidification only
• CPC Class Codes: F24F 2203/1036 Details
• CPC Class Codes: F24F 2203/1056 comprising a reheater
• CPC Class Codes: F24F 2203/1068 comprising one rotor
• CPC Class Codes: F24F 2203/1084 comprising two flow rotor segments
• CPC Class Codes: F24F 3/1411 by absorbing or adsorbing water, e.g. using an hygroscopic desiccant
• CPC Class Codes: F24F 3/1423 with a moving bed of solid desiccants, e.g. a rotary wheel supporting solid desiccants
• CPC Class Codes: F24F 5/0035 using evaporation
• CPC Class Codes: F28D 5/02 in which the evaporating medium flows in a continuous film or trickles freely over the conduits
• CPC Class Codes: Y02B 30/54 Free-cooling systems

Abstract

An improved method and apparatus for indirect evaporative cooling of a fluid stream to substantially its dew point temperature. Plate heat exchanger has perforations 11 and channels 3, 4 and 5 for gas or a low temperature for liquids on a dry side and wet side. Fluid streams 1 flow across the dry side 9, transferring heat to the plate. Gas stream 2 flows across the dry side and through perforations to channels 5 on wet side 10, which it then cools by evaporative cooling as well as conductive and radiative transfer of heat from plate. A wicking material provides wetting of wet side. In other embodiments, a desiccant wheel may be used to dehumidify the gas, air streams may be recirculated, feeder wicks 13 and a pump may be used to bring water from a water reservoir, and fans may be used to either force or induce a draft. The wicking material may be cellulose, organic fibers, organic based fibers, polyester, polypropylene, carbon-based fibers, silicon based fibers, fiberglass, or combinations of them. The device may be operated in winter months to scavenge heat from exhaust gases of a space and thus pre-heat fresh air, while simultaneously humidifying the fresh air.

Claims

1. A plate for heat exchange and indirect evaporative cooling of at least one fluid stream, the plate comprising:

a) a dry side having low permeability to an evaporative liquid; and

b) a wet side designed to have its surface wet by an evaporative liquid;

wherein the dry side of the plate forms at least one first channel to guide a working gas stream and second channels, generally aligned with the first channel, to guide a product fluid stream;

and wherein the plate further forms at least one perforation through the plate in the working stream channel to allow the working stream to transfer to the wet side of the plate.

2. The plate of claim 1, further comprising third channels on the wet side of the plate oriented in a direction other than parallel to the first channel on the dry side of the plate.

3. The plate of claim 2, wherein the second channels are oriented at an angle to the third channels, such that the direction of flow of fluids across the dry side of the plate is substantially perpendicular to the direction of flow of gases across the wet side of the plate.

4. The plate of claim 3, wherein the plate comprises a material having a low rate of heat transfer, but with a thin cross-section that allows heat to be readily transferred from the dry side to the wet side, even with the low rate of heat transfer of the material.

5. The plate of claim 2, wherein the channels aid laminar flow across at least one side of the plate.

6. The plate of claim 2, wherein the channels are formed by a plurality of ribs extending parallel to the direction of gas flow across the plate.

7. The plate of claim 2, wherein the channels are provided by corrugations of the plate.

8. The plate of claim 1, wherein the perforation is one of the shapes belonging to the group consisting of:

round and polygonal having rounded corners.

9. The plate of claim 1, wherein the plate is oriented so as to slope at an angle of from −

10 to +10 degrees from the horizontal.

10. The plate of claim 9, further comprising a reservoir of water, wherein the lowest edge of the plate is in contact with the water.

11. An indirect evaporative cooler comprising:

a) a plate having dry and wet sides, the wet side designed to be at least partially wet by an evaporative liquid, the plate further forming at least one first channel to guide a working gas stream across the dry side of the plate, second channels to guide a product fluid stream across the dry side of the plate, and third channels to guide the working gas stream across the wet side of the plate; and

b) a perforation through the plate in the area of the working stream channel on the dry side, wherein the working stream can flow through the perforation from the dry side to the wet side and flow across the wet side;

wherein, in use, the plate transfers heat to the working gas stream on the wet side by direct evaporative cooling and cools the plate and the product flow and working gas streams flowing on the dry side.

12. The indirect evaporative cooler of claim 11, further comprising a second plate, the second plate including:

a) a plate having dry and wet sides, the wet side designed to be at least partially wet by an evaporative liquid, the plate further forming at least one first channel to guide a working gas stream across the dry side of the plate, second channels to guide a product fluid stream across the dry side of the plate, and third channels to guide the working gas stream across the wet side of the plate; and

b) a perforation through the plate in the area of the working stream channel on the dry side, wherein the working stream can flow through the perforation from the dry side to the wet side and flow across the wet side;

wherein, in use, the second plate transfers heat to the working gas stream on the wet side by direct evaporative cooling and cools the plate and the product flow and working gas streams flowing on the dry side;

wherein the second plate is aligned in parallel with the first plate, spaced apart therefrom, and oriented so as to have wet sides of the first and second plates opposing, and further wherein, in use, the working gas stream from the dry side of both the first and second plates flows through the perforations to the space separating the plates on the wet sides; and

wherein, in use, the product fluid passes across and is cooled on the dry sides of both the first and second plates.

13. The indirect evaporative cooler of claim 12, wherein the spacing between the plates is chosen to minimize the pressure drop of the gases flowing between the plates.

14. The indirect evaporative cooler of claim 13, wherein the spacing between the plates is further chosen to be between 1.5 and 3.5 millimeters.

15. The indirect evaporative cooler of claim 14, wherein the spacing between the plates is further chosen to be in one of the ranges in the group consisting of:

1.50 to 1.85 millimeters, 2.00 to 2.35 millimeters, 2.10 and 2.90 millimeters and 3.10 and 3.50 millimeters.

16. The indirect evaporative cooler of claim 12, wherein at least one perforation through each plate is offset from a perforation through another plate.

17. The indirect evaporative cooler of claim 12, wherein one or more channels on the dry side are oriented at an angle to one or more channels on the wet side such that the direction of flow of fluids across the dry sides of the plates is substantially perpendicular to the direction of flow of gases across the wet side of the plates.

18. The indirect evaporative cooler of claim 12, further including an element for dehumidifying the product stream and the working stream prior to flowing across the dry sides of the plates.

19. The indirect evaporative cooler of claim 12, further including a desiccant humidifier and means for passing at least one of the streams, the product stream or the working stream, through the desiccant dehumidifier prior to flowing across the plates.

20. The indirect evaporative cooler of claim 12, wherein the product stream is recirculated from the space to be cooled to be reused as the working stream and/or the product stream.

21. The indirect evaporative cooler of claim 12, further comprising a barrier dimensioned and configured to prevent the working stream from exiting the indirect evaporative cooler prior to passing through the perforations.

22. The indirect evaporative cooler of claim 12, wherein the channels comprise a plurality of ribs extending parallel to the direction of fluid flow across the sides of the plates and the opposing surfaces of adjoining plates.

23. The indirect evaporative cooler of claim 12, wherein the channels comprise corrugations of the plates.

24. The indirect evaporative cooler of claim 12, usable in either cooling a space or assisting in warming and humidifying the space, further comprising:

a cycle control damper having first and second positions such that when the cycle control damper is in the first position, the working gas stream is expelled into the atmosphere and the product stream is directed to cooling the space, and when the cycle control damper is in the second position, the product stream is expelled into the atmosphere and the working stream is directed to warm and humidify the space.

25. The indirect evaporative cooler of claim 12, further comprising at least one fan arranged so as to cause the motion of the product fluid and working gas streams.

26. A method of indirect evaporative cooling comprised of the following steps:

a) providing a heat transfer surface having perforations;

b) wetting one portion of the heat transfer surface with an evaporative liquid, thereby forming a wet portion;

c) having gas pass through the heat transfer surface from the remaining dry portion to the wet portion;

d) passing a working stream across the dry portion of the heat transfer surface where there are perforations;

e) passing a product fluid stream across the dry portion of the heat transfer surface to be cooled and used;

f) flowing the working stream through the perforations in the heat transfer surface to the wet portion of the heat transfer surface;

g) cooling the heat transfer surface by evaporating the evaporative liquid into the working stream on the wet portion of the heat transfer surface; and

h) cooling the product stream and working stream by contact with the cooled heat transfer surface in the dry portion.

27. The method of claim 26 further comprising the following steps:

a) utilizing a plate for the heat transfer surface;

b) providing two or more plates adjacent, spaced apart, and generally parallel to each other;

c) positioning adjacent plates with their opposed surfaces being of the same type, such as both wet surfaces;

d) providing guides in the dry space between adjacent plates and guiding the fluid of the product stream and the working stream therein, keeping the product stream separate from the working stream;

f) providing guides in the wet space between adjacent plates, the wet space guides nonparallel to the dry space guides, and guiding the working stream therein after it has passed through the perforations.

28. The method of claim 27 further including the step of distributing the liquid for the wet surfaces via a wicking layer on the wet side of the plates.

29. The method of claim 28 further including the step of providing a layer on the dry side that is impermeable to the evaporative liquid.

30. The method of claim 28 further including the step of furnishing evaporative liquid to the wick layer of the plates via a feeder wick.

31. The method of claim 30 further including the steps of providing a reservoir and furnishing evaporative liquid to the feeder wick from the reservoir.

32. The method of claim 31 further including the step of locating the reservoir on top of the feeder wick.

33. The method of claim 32 further including the step of locating the reservoir at the bottom of the feeder wick.

34. The method of claim 30 further including the step of placing the wet side of the plates closest to the perforations in liquid communication with the feeder wick.

35. The method of claim 30 wherein the feeder wick is a plate.

36. The method of claim 35 where the feeder wick plate comprises a sandwich of two different materials, the outside having less porosity than the inside material.

37. The method of claim 35 further including the step of providing means in the feeder wick to disburse evaporative liquid quickly to the edges of the feeder wick furthest from the reservoir.

38. The method of claim 26 where the guides on the dry side run parallel to the side of the plate closest to the perforations.

39. The method of claim 26 where the guides on the wet side run in a direction other than parallel to the guides on the dry side.