Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Reexamination Certificate
1999-11-09
2001-09-18
Flanigan, Allen (Department: 3743)
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
C165S164000, C165SDIG003, C029S890030
Reexamination Certificate
active
06289978
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to coiled heat exchangers having a spiral configuration. In these types of heat exchangers, heat transfer fluids enter, circulate, and exit the heat exchanger in a counterflow manner in a direction substantially parallel to the coil's longitudinal axis.
BACKGROUND OF THE INVENTION
Though numerous applications utilize coiled heat exchangers, the gas turbine recuperator is among the most demanding. In any application, and especially when used as a gas turbine recuperator, the heat exchanger should be compact, efficient, reliable, and relatively inexpensive to manufacture. By designing the primary heat transfer surface with small hydraulic diameters and counterflow circulation of heat transfer fluids, a relatively compact and efficient heat exchanger can be obtained. Furthermore, providing the heat exchanger with relatively large cross-sectional flow areas reduces load losses. Achievement of large cross-sectional flow areas in coiled heat exchangers requires circulating heat transfer fluids in the axial, as opposed to tangential, direction. Additionally, production costs can be lowered by minimizing the number of elements used to make the heat exchanger and by forming and coiling the heat exchanger in a continuous process. Another design consideration, especially when used as a gas turbine recuperator, includes resistance to thermal shock. Heavy thermal loads often result from the transient operation of turbines. Therefore, to ensure reliable performance and operation, the heat exchanger should have high resistance to
Various known heat exchangers are made from coiling a pair of sheets between which heat transfer fluids circulate in a counterflow manner in directions substantially parallel to the longitudinal axis of the coil. For example, U.S. Pat. No. 5,797,449 pertains to an annular heat exchanger formed by a pair of sheets welded together and coiled, with openings cut through the sheets through which heat transfer fluid passes.
German patents DE 1121090 and DE 3234878 describe spiral heat exchangers having axially circulated fluid flows, in which the fluids enter and exit through alternating angular sectors. In DE 1121090, sectors for circulating the heat transfer fluids are formed by cutting evenly-spaced openings in borders that close the edges of a pair of sheets coiled to form the heat exchanger. After the borders are cut, the two sheets are coiled to form the heat exchanger. DE 1121090 additionally discloses the fabrication of the spiral heat exchangers with external headers.
In DE 3234878, the sectors are formed by glueing blocking segments on the two faces of the coiled heat exchanger.
Finally, in French patent document FR-A-231 9868, borders are closed by the direct welding of adjacent sheets.
A particular difficulty in heat exchangers having a coiled configuration includes the distribution of the single incoming flow into the myriad of small heat transfer passages and the collection of the same into a single outgoing flow after the heat transfer has taken place. Preferably, this distributing and collecting should not result in excessive head losses, nor should it cause mechanical stresses due to large thermal gradients. Another difficulty arises from blockages to the heat transfer fluids that exist on the core face as the result of the particular construction used for the heat exchanger.
For instance, in one known example, the sheets are constructed and cut such that one sheet has openings only for one fluid and the other has openings only for the other fluid. This leads to a relatively high amount of fluid being blocked at the core faces, thus reducing gas flow passage and overall efficiency of the heat exchanger.
Stacked plate heat exchangers often include openings cut in the plates to distribute and collect the heat transfer fluids. The edges of these openings generally are either brazed or welded together during assembly of the heat exchanger (for example in U.S. Pat. No. 4,073,340) or are fitted with a gasket (for example in Alfa-Laval plate heat exchangers). Other stacked plate heat exchangers do not include such openings (see SAE 851254. “Development, Fabrication, and Application of a Primary Surface Gas Turbine Recuperator”, E. L. Parsons), but the sides of the plates must be provided with sealing bars.
Also important in constructing a coiled heat exchanger is the connection of the external headers with the core. The header-to-core connection must be sealed to prevent leakage of heat transfer fluids being passed to the heat exchanger core. Furthermore, headers should have the strength to resist forces tending to pull them away from the core due to the relatively high pressures experienced as fluids are collected and distributed and to inertial forces resulting from supporting the core weight. Additionally, temperature gradients occurring between the core and the header can result due to sudden transient temperatures in one of the heat transfer fluids combined with the relative thermal inertia of the core and the headers. Such gradients may cause thermal expansion forces on headers. Therefore, construction of the heat exchanger needs to account for these effects as well.
SUMMARY OF THE INVENTION
The advantages and purpose of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purpose of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention includes a heat exchanger formed by coiling a pair of sheets. The heat exchanger includes a first sheet having an edge and a second sheet having an edge. The first and second sheets are connected to each other along their respective edges such that the edges form a substantially flat wall. The wall formed by connecting the first and second sheet edges includes a first set of openings formed by cutting the wall and a second set of openings formed by flattening the wall.
Another aspect of the present invention includes a method for forming a coiled heat exchanger. The method includes providing a first sheet and a second sheet and connecting the sheets to each other along edges of the sheets such that the edges form a substantially flat wall between surfaces of the sheets. The method further includes reducing a thickness of the wall along periodic intervals of the length of the connected sheets. The sheets are then coiled to form a cylindrical core, with the core having a face formed by the wall. Finally, the method includes removing portions of the wall on the face of the core.
REFERENCES:
patent: 2663549 (1953-12-01), Otten
patent: 3507115 (1970-04-01), Wisoka
patent: 3854530 (1974-12-01), Jouet et al
patent: 3893509 (1975-07-01), Satchwell et al.
patent: 4073340 (1978-02-01), Parker
patent: 4089370 (1978-05-01), Marchal
patent: 4124069 (1978-11-01), Becker
patent: 4546826 (1985-10-01), Zitzmann
patent: 5273106 (1993-12-01), Drake
patent: 5505255 (1996-04-01), Viessmann
patent: 5797449 (1998-08-01), Oswald et al.
patent: 588741 (1933-11-01), None
patent: 11 21 090 (1962-01-01), None
patent: 32 34 878 (1984-03-01), None
patent: 0 798 527 (1997-10-01), None
patent: 1058090 (1954-03-01), None
patent: 2 319 868 (1977-02-01), None
patent: 2559249 (1985-09-01), None
patent: 291593 (1928-06-01), None
patent: 892962 (1962-04-01), None
patent: 98/05916 (1998-02-01), None
E. L. Parsons, Solar Turbines, Inc., San Diego, California; SAE Technical Paper Series 851254; “Development, Fabrication and Application of a Primary Surface Gas Turbine Recuperator,”; Government/Industry Meeting & Exposition, Washington, D.C., May 20-23, 1985.
Ateliers de Construction de Thermo-Echangeurs SA
Finnegan, Henderson, Farabow, Garett & Dunner, L.L.P.
Flanigan Allen
LandOfFree
Coiled heat exchanger and a method for making a coiled heat... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coiled heat exchanger and a method for making a coiled heat..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coiled heat exchanger and a method for making a coiled heat... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2512448