Dehumidification system
The present invention relates to dehumidification equipment and more particularly, to a dehumidification system and method for use in hazardous locations. In particular, there is provided a desiccant wheel assembly for use in a dehumidification system. The desiccant wheel assembly includes a cabinet and a desiccant wheel rotatively mounted within the cabinet. The desiccant wheel has a core impregnated with a desiccant material and an electrically conductive outer shell surrounding the core. Means are provided for driving rotation of the desiccant wheel within the cabinet. The desiccant wheel assembly further includes a static control device connected to a ground and associated with the desiccant wheel for discouraging the build-up of electrostatic charges on the desiccant wheel during rotation thereof. A dehumidification system comprising such a desiccant wheel assembly is also described along with a method for dehumidifying air in an enclosed space using a desiccant wheel dehumidification system.
1. A desiccant wheel assembly for use in a dehumidification system, the desiccant wheel assembly comprising:
a cabinet;
a desiccant wheel rotatively mounted within the cabinet, the desiccant wheel having a core impregnated with a desiccant material and an electrically conductive outer shell surrounding the core;
means for driving rotation of the desiccant wheel within the cabinet; and
a static control device connected to a ground and associated with the desiccant wheel for discouraging the build-up of electrostatic charges on the desiccant wheel during rotation thereof.
2. The desiccant wheel assembly of claim 1 wherein the core is fabricated from extruded paper fibers.
3. The desiccant wheel assembly of claim 2 wherein the extruded paper fibers measure at least 5 microns in diameter.
4. The desiccant wheel assembly of claim 1 wherein the desiccant material is a solid, non-granular desiccant material.
5. The desiccant wheel assembly of claim 4 wherein the desiccant material is selected from the group consisting of: (a) lithium chloride; (b) silica gel; and (c) molecular sieve.
6. The desiccant wheel assembly of claim 1 wherein the outer shell is made of aluminium.
7. The desiccant wheel assembly of claim 1 wherein the driving rotation means includes a motor designed to be explosion-proof.
8. The desiccant wheel assembly of claim 7 wherein the motor is selected from the group consisting of: (a) an electric motor; (b) a hydraulically-driven motor; and (c) a pneumatically-driven motor.
9. The desiccant wheel assembly of claim 1 wherein the static control device is connected to the outer shell of the desiccant wheel.
10. The desiccant wheel assembly of claim 9 wherein the static control device is fixed to one of the desiccant wheel and the cabinet.
11. The desiccant wheel assembly of claim 1 wherein the cabinet includes a plurality of walls defining a space for accommodating the desiccant wheel, the static control device being disposed within the space.
12. The desiccant wheel of claim 11 wherein:
the plurality of walls includes a bottom wall and a pair of spaced apart, first and second walls extending upwardly from the bottom wall; and
the desiccant wheel has an axis of rotation disposed longitudinally between the first and second walls.
13. The desiccant wheel assembly of claim 12 wherein the static control device is fixed to one of the plurality of walls of the cabinet.
14. The desiccant wheel assembly of claim 13 wherein the static control device is fixed to the first wall of the cabinet.
15. The desiccant wheel assembly of claim 14 wherein the static control device includes:
a grounding member for engaging the outer shell of the desiccant wheel;
a biasing member for biasing the grounding member against the outer shell; and
a mounting block for carrying the grounding member.
16. The desiccant wheel assembly of claim 15 wherein the static control device further includes a bracket for attachment to the first wall of the cabinet, the bracket supporting the mounting block.
17. The desiccant wheel assembly of claim 16 wherein the bracket is L-shaped.
18. The desiccant wheel assembly of claim 17 wherein the bracket has a first leg secured to the first wall of the cabinet and a second leg supporting the mounting block.
19. The desiccant wheel assembly of claim 15 wherein the biasing member is a spring.
20. The desiccant wheel assembly of claim 15 wherein the grounding member is a disc.
21. The desiccant wheel assembly of claim 20 wherein the disc is axially mounted within the mounting block.
22. The desiccant wheel assembly of claim 12 wherein the static control device is urged to rotate about the axis of rotation during rotation of the desiccant wheel.
23. The desiccant wheel assembly of claim 22 wherein:
the outer shell is a tubular body, the tubular body having an inner surface and an outer surface; and
the static control device is mounted onto the outer surface of the outer shell.
24. The desiccant wheel assembly of claim 12 wherein:
the outer shell is a tubular body, the tubular body having fore and aft rims; and
the static control device is connected to the tubular body at one of the fore and aft rims.
25. The desiccant wheel assembly of claim 24 wherein the static control device includes a grounding member, the grounding member being disposed between one of, the fore rim and the first wall, and the aft rim and the second wall.
26. The desiccant wheel assembly of claim 25 wherein the grounding member includes at least one ball bearing.
27. The desiccant wheel assembly of claim 1 wherein the static control device includes a grounding member.
28. The desiccant wheel assembly of claim 20 wherein the grounding member is made of steel.
29. The desiccant wheel assembly of claim 28 wherein the grounding member includes a brush member with metallic bristles.
30. The desiccant wheel assembly of claim 29 wherein:
the cabinet includes a plurality of walls defining a space for accommodating the desiccant wheel, the static control device being disposed within the space;
the plurality of walls includes a bottom wall and a pair of spaced apart, first and second walls extending upwardly from the bottom wall;
the desiccant wheel has an axis of rotation disposed longitudinally between the first and second walls;
the brush member is mounted to the bottom wall of the cabinet with its bristles extending upwardly toward the outer shell of the desiccant wheel, the bristles being positioned to brush against the outer shell during rotation of the desiccant wheel.
31. The desiccant wheel assembly of claim 27 wherein:
the cabinet includes a plurality of walls defining a space for accommodating the desiccant wheel, the static control device being disposed within the space;
the plurality of walls includes a bottom wall and a pair of spaced apart, first and second walls extending upwardly from the bottom wall;
the desiccant wheel has an axis of rotation disposed longitudinally between the first and second walls;
the grounding member includes a flap hingedly mounted to one of the plurality of walls of the cabinet, for engaging the outer shell of the desiccant wheel.
32. The desiccant wheel assembly of claim 31 wherein the flap is biased against the outer shell.
33. The desiccant wheel assembly of claim 1 wherein the desiccant wheel is supported on caster assemblies, at least a portion of the caster assemblies defining the static guard device.
34. The desiccant wheel assembly of claim 1 further comprising a central shaft connected to a ground, the desiccant wheel being axially mounted for rotation about the central shaft, and the static control device connecting the central shaft to the outer shell of the desiccant wheel.
35. The desiccant wheel assembly of claim 1 wherein the ground includes an electrical ground.
36. The desiccant wheel assembly of claim 1 wherein the cabinet is supported by a frame and the frame serves as the ground.
37. A system for dehumidifying air in an enclosed space comprising:
a desiccant wheel assembly having:
a cabinet;
a desiccant wheel rotatively mounted within the cabinet, the desiccant wheel having a core impregnated with a desiccant material and an electrically conductive outer shell surrounding the core, the core of the desiccant wheel having a process section and a reactivation section defined therein;
means for driving rotation of the desiccant wheel within the cabinet; and
a static control device connected to a ground and associated with the desiccant wheel for discouraging build-up of electrostatic charges on the desiccant wheel during rotation thereof;
first blower means for drawing a supply air stream from the enclosed space and urging the supply air stream to flow through the process section wherein moisture in the supply air stream is removed by the desiccant material;
an outlet located downstream of the process section for exhausting the dehumidified supply air stream into the enclosed space;
a reactivation system for heating a reactivation air stream;
second blower means for drawing the reactivation air stream from outside the enclosed space through the reactivation system and urging the reactivation air stream to flow through the reactivation section wherein moisture retained in the desiccant material is released into the reactivation air stream; and
a reactivation air outlet located downstream of the reactivation section for exhausting the reactivation air stream outside the enclosed space.
38. The system of claim 37 wherein the static control device is connected to the outer shell of the desiccant wheel.
39. The system of claim 38 wherein the static control device is fixed to one of the desiccant wheel and the cabinet.
40. The system of claim 37 further comprising a frame for supporting the cabinet, the frame serves as the ground.
41. The system of claim 37 wherein the driving rotation means includes a motor designed to be explosion-proof.
42. The system of claim 41 wherein the motor is selected from the group consisting of: (a) an electric motor; (b) a hydraulically-driven motor; and (c) a pneumatically-driven motor.
43. The system of claim 37 wherein each of the first and second blower means includes a suction blower driven by a motor designed to be explosion-proof.
44. The system of claim 43 wherein the motor is selected from the group consisting of: (a) an electric motor; (b) a hydraulically-driven motor; and (c) a pneumatically-driven motor.
45. The system of claim 37 wherein the reactivation system heats the reactivation air stream using a reactivation process selected from the group consisting of: (a) electrical reactivation; (b) steam reactivation; and (c) gas fired reactivation.
46. The system of claim 37 wherein the reactivation system includes at least one duct heater.
47. The system of claim 46 wherein the at least one duct heater is an electric duct heater.
48. A method for dehumidifying air in an enclosed space using a desiccant wheel dehumidification system, the method comprising:
providing a rotatable desiccant wheel having a core impregnated with a desiccant material and an electrically conductive outer shell surrounding the core, the core of the desiccant wheel having a process section and a reactivation section defined therein;
providing a static control device connected to a ground and associated with the desiccant wheel;
driving the desiccant wheel to rotate;
urging the static control device to contact the desiccant wheel to thereby discourage the build-up of electrostatic charges on the desiccant wheel during rotation thereof;
drawing a supply air stream from the enclosed space and urging the supply air stream to flow through the process section wherein moisture in the supply air stream is removed by the desiccant material in the core;
exhausting the thus dehumidified supply air stream into the enclosed space; and
regenerating the desiccant material in the core.
49. The method of claim 48 wherein regenerating the desiccant material includes:
drawing a reactivation air stream from outside the enclosed space and urging it to flow through the reactivation section wherein moisture retained in the desiccant material is released into the reactivation air stream; and
exhausting the reactivation air stream outside the enclosed space.
50. The method of claim 49 wherein drawing the reactivation air stream includes heating the reactivation air stream.