Patent Application
20090000762
This invention generally relates to heat exchangers. In particular, the present invention relates to seals for rotary regenerative heat exchangers.
A regenerative heat exchanger (regenerator) uses a heat transfer matrix which is rotated through a hot and a cold stream consecutively to transfer heat from the former to the latter. The device call also be used to transfer mass between two fluids differing in concentration in a targeted constituent and the exchange (be it mass and/or heat) can involve any number of flows greater than one.
Each of the hot and cold flows is typically carried to and from the matrix by a conduit. The flows enter and exit the matrix through a face of the matrix, and a configuration of seals is located between the conduits and the rotating matrix face to prevent leakage of the flows from the conduits into the environment or from one flow into another. Two types of seals are generally used, non-contact seals or contact seals. With non-contact seals (which do not contact the matrix face), it is a major challenge to properly adjust a gap between the matrix face and the non-contact seal minimizing leakage to maximize efficiency of the heat exchanger. Contact seals (which do contact the matrix face) ensure lower leakage which improves efficiency of the regenerator as compared to non-contact seals. Use of contact seals, however, causes increased seal wear and also reduces efficiency of the regenerator due to the increased function between the contact seal and the matrix that must be overcome in the rotation of the matrix. Additionally, rubbing of the contact seals on the regenerator matrix can over time produce solid material (either from the matrix or the seals) which will contaminate the flow and might lead to clogging in a porous matrix.
The present invention solves the aforementioned problems by providing a regenerative heat exchanger including a brush-seal configuration to prevent mixing of fluid flows. The regenerative heat exchanger includes a regenerator matrix, and at least two conduits, each conduit having a matrix end abutting a face of the regenerator matrix. At least two conduits carry at least two fluid flows which pass through the regenerator matrix. The regenerative heat exchanger includes a plurality of brush-seals. Each brush-seal is located at a matrix end of each conduit without contacting the matrix, thereby sealing around a periphery of each conduit to prevent mixing of fluid flows.
A method for establishing a minimal gap between a regenerator matrix of a regenerative heat exchanger and a plurality of brush-seals is disclosed. The method includes installing the plurality of brush-seals such that a bristle end of each brush-seal contacts a face of the regenerator matrix. The regenerator matrix is rotated at a desired speed about an axis substantially perpendicular to the face of the regenerator matrix. During rotation, friction between the bristle end and the face causes material to be removed from the bristle end. The rotation is stopped when a power required to rotate the regenerator matrix at the desired speed reaches a predetermined level. This stops the removal of material from the bristle end and establishes a minimal gap between the bristle end and the face of the regenerator matrix.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of preferred embodiments when considered in light of the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Shown in
The matrix 12 is connected to a drive motor 18. The drive motor 18 causes the matrix 12 to rotate about a matrix axis 20 and transfer heat from the hot fluid stream carried through second conduit 16 to the cold fluid stream carried through first conduit 14. Because the matrix 12 moves relative to the first conduit 14 and the second conduit 16, a configuration of seals is required on a face 22 of the matrix 12 to prevent leakage, including leakage from the conduits 14 or 16, and leakage between the first conduit 14 and the second conduit 16.
Sealing between the face 22 and each of the conduits 14 and 16 is accomplished by a brush-seal configuration 24. The brush-seal configuration 24 between first conduit 14 and the face 22 is substantially identical to the brush-seal configuration 24 between second conduit 16 and the face 22, so only the brush-seal configuration 24 between first conduit 14 and the face 22 will be described herein. The brush-seal configuration 24 may be made from a variety of materials including metal, super alloys, ceramics, etc., and is chosen depending on thermal and chemical requirements of the application. As shown in
The seal holder 26 is secured to a casing 34 by a plurality of casing screws 36. The casing 34 extends circumferentially around the first conduit 14, and is fixed relative to the first conduit 14. The casing screws 36 are inserted in a radial direction through axially-slotted holes 38 in the seal holder 26 and into threaded casing holes (not shown) in the casing 34, thereby securing the seal holder 26 to the casing 34. The slotted holes 38 allow the position of the seal holder 26 to be adjusted relative to the casing 34, and thus the position of the brush-seal 24 relative to the face 22 can be adjusted. Initially, the brush-seal 24 is positioned so the bristles 40 are in contact with the face 22. It is to be appreciated that the attachment scheme of the blush-seals 24 described herein is only an example. Other attachment schemes including, for example, adhesive attachment, are contemplated within the scope of this invention.
When the blush-seals 24 are installed, a break-in process is employed to establish a minimal gap between the blush-seals 24 and the matrix 12 at the faces 22. In one embodiment, a necessary power, Pref, for rotation of the matrix 12 at a desired rotation speed is determined prior to installing the brush-seals 24. The brush-seals 24 are installed so the bristles 40 contact the matrix 12 as described above. The matrix 12 is rotated to the desired rotation speed, and a power required to rotate the matrix 12, Pin, is monitored. Initially, because of the contact between the bristles 40 and the matrix 12, Pin>Pref. During this break-in process, the regenerator 10 is run under normal wordings conditions, i.e. the flows passing through the regenerator will be at the temperatures of the flows during normal operation. The friction between the bristles 40 and the matrix 12 during the break-in process increases the temperature of the bristles 40 and the matrix 12, and thus will cause slightly increased thermal expansion of the matrix 12 and the bristles 40 over that which would occur during normal operation.
As the break-in process progresses, material is worn off of the bristles 40 and/or the face 22. As material is worn off, friction between the bristles 40 and the matrix 12 is reduced. Because of the reduced friction, the temperature of bristles 40 and the matrix 12 are reduced slightly, reducing thermal expansion of the bristles 40 and the matrix 12, thus creating a slight gap between the bristles 40 and the matrix 12. The reduced friction also reduces Pin required for the matrix 12 to rotate at the desired speed. Pin is monitored until Pin=Pref, at which point the break-in process is completed, leaving the desired gap between the bristles 40 and the matrix 12.
While embodiments of the invention have been described above, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
