Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Patent
1993-08-04
1995-01-24
Flanigan, Allen J.
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
165167, 165170, F28F 308
Patent
active
053835182
DESCRIPTION:
BRIEF SUMMARY
This invention relates to heat exchangers of the kind generally known as plate-fin heat exchangers are
The fluid passages in plate-fin heat exchangers are defined by partitions of a metal which has a satisfactorily high coefficient of heat transfer, so that when a high temperature fluid is passed through some passages and low temperature fluid is passed through further passages which are adjacent thereto, there results a cooling of the originally high temperature fluid, by heat conduction through the thickness of the partitions into the cool fluid. Efficiency of heat exchange is boosted by inclusion in the fluid flow passages of so-called "fins", which may in fact be corrugated members, dimples, grooves, protuberances, baffles or other turbulence promoters, instead of fins as such.
Plate-fin heat exchangers offer significant advantages over shell-tube heat exchangers in terms of weight, space, thermal efficiency and the ability to handle several process streams --i.e. several streams of heat exchange media--at once. However, most current plate-fin heat exchanger technology is centred on a brazed matrix construction using aluminium components and is therefore limited to low pressure and low temperature operation. Even using other materials, such as stainless steel, operational pressure limits (say, 80-90 bar) apply because of the use of brazing as the method of fabrication.
Our prior patent applications EP90308923.3 and GB9012618.6 disclose alternative ways of manufacturing plate-fin heat exchanger elements which help to avoid the above problems and allow greater flexibility in their design. Among other things, they describe a method of manufacturing heat exchange plate elements in which metal (e.g. titanium or stainless steel) sheets are stacked together and selectively .diffusion bonded to each other before being superplastically deformed to a final hollow shape defining internal passages, which can incorporate integrally formed "fins". Use of superplastic deformation in the manufacturing process enables the generation of high volume fractions of hollowness in a heat exchanger element. For example, if titanium sheets are used as the starting point, the result is a high integrity, low weight heat exchanger element which can operate at internal pressures in excess of 200 bar and at temperatures up to 300.degree. C. Stainless steel elements will operate at higher temperatures and pressures. assembly of heat exchangers incorporating matrices of such superplastically formed/diffusion bonded heat exchanger plate elements. elements. facilitating exchange of heat between at least two process streams, comprises; exchange relationship, the plate elements comprising diffusion bonded sandwich constructions, each such sandwich construction having two outer sheets and a superplastically expanded core sheet structure between the two outer sheets, each core sheet structure providing flow passage means for at least one process stream, adjacent plate elements being in intimate thermal contact with each other over at least most of the areas of their side faces through bonded joints between them, and passing the process streams through the plate elements, the manifold means penetrating the matrix from side-to-side through the thicknesses of the plate elements.
Preferably, for maximum strength and heat and corrosion resistance of the heat exchanger matrix, the bonded joints between adjacent plate elements are metallurgically bonded joints, especially diffusion bonded or activated diffusion bonded joints. If activated diffusion bonded joints are utilised, they are preferably protected from contact with aggressive process stream fluid in the manifold means by autogenous seal welds spanning the joints between the penetrated plate elements.
Further aspects of the invention will be apparent from a reading of the following description and claims.
An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a part-sectional view of a complete heat exchanger a
REFERENCES:
patent: 3512238 (1970-05-01), Canon et al.
patent: 3927817 (1975-12-01), Hamilton et al.
patent: 4484623 (1984-11-01), Rowe et al.
patent: 4603460 (1986-08-01), Yano et al.
Adderley Colin I.
Banks Simon A.
Boardman James E.
Fowler John O.
Flanigan Allen J.
Rolls-Royce and Associates Limited
Rolls-Royce plc
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