Heat exchange – Expansion and contraction relieving or absorbing means – Relieving or absorbing means supports temperature modifier...
Patent
1992-10-20
1994-08-02
Rivell, John
Heat exchange
Expansion and contraction relieving or absorbing means
Relieving or absorbing means supports temperature modifier...
168145, 168160, F28F 700
Patent
active
053336810
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a design concept of a plate-type heat exchanger. Generally speaking, plate exchangers differ from shell-and-tube exchangers in that the fluids in a heat-exchange condition flow longitudinally on each side of plates placed in juxtaposed and parallel relation.
As described, for example, in French patent No. 2 471 569 or in French patent Application No. 88 13883, heat exchangers of this type have a stack of parallel flat plates made up of thin corrugated sheets which are mostly of stainless steel. By means of their corrugated surfaces, said sheets are in contact with each other and serve to establish the circulation of the fluids from one end of the heat exchanger to the other in the longitudinal direction (usually in countercurrent flow) while setting up turbulences, these turbulences being conducive to the heat exchanges which take place between the fluids through each plate. Along their longitudinal edges, the plates are welded to each other by means of small tongues or frames forming spacer members which maintain the spacing between two successive plates. The stack of plates is surrounded by two metallic sheets of relatively substantial thickness, thus transferring the weight of the stack to a support.
The thickness of the exchanger plates depends on whether or not it is necessary to endow the stack with mechanical strength by ensuring rigidity of the plates themselves.
In this type of heat exchanger, one encounters specific problems of operational safety and durability other than those for which a solution has been found in the case of tube-type exchangers, especially those in which the heat-exchange elements are mounted so as to form a bundle of parallel cylindrical tubes, the ends of which open through transverse plates to which they are welded.
To reconcile thermal expansion phenomena with mechanical stresses therefore demands radically different solutions. In particular, the high efficiency sought by the use of heat exchange elements consisting of thin metallic sheets of large size and especially of substantial length which are applied against each other by means of corrugations providing passageways for the circulating fluids is concomitant with low mechanical strength of these elements. At the same time, any connections between the stack of thin sheets and structural elements which have sufficient thickness to possess high mechanical strength give rise to differences in thermal inertia and hence to sensitivity to temperature variations.
In conventional designs of plate exchangers to which the invention is preferentially directed, the sheets of substantial thickness and mechanical strength which surround the stack of heat exchange plates serve to support the entire assembly within a vessel or shell which affords resistance to the pressure of fluids. Said sheets are rigidly fixed to the shell in the central portion of the heat exchanger by means of lateral coupling plates.
The need to use framing sheets of sufficient thickness to withstand all the mechanical stresses to which the stack is subjected and to transfer the stresses by means of brackets or other supports to the vessel itself gives rise to difficulties in regard to the connections with the thin sheets of the stack since the welded joints formed are sensitive to thermal phenomena. Furthermore, the stack exhibits a deplorable tendency to undergo a bending moment at the level of the longitudinal faces not equipped with thick support sheets in the median support zone.
While overcoming these disadvantages, the invention proposes a plate exchanger corresponding to a novel mode of assembly of the stack within its vessel which meets practical requirements more effectively than plate exchangers of the prior art, especially in regard to convenience of manufacture, costs and operational safety.
The invention is directed to a plate-type heat exchanger comprising a stack of plates for heat exchange between fluids which circulate between each other, said stack being placed within a pressure vessel, characterized in
REFERENCES:
patent: 3596638 (1971-08-01), Michel
patent: 3930537 (1976-01-01), Wolowodiuk
patent: 4267882 (1981-05-01), Gralton
patent: 4441549 (1984-04-01), Vasiliev et al.
patent: 4548260 (1985-10-01), Stachura
patent: 4807698 (1989-02-01), Kohnen et al.
Couillard Yves
Jullien Claude
Leo L. R.
Packinox SA
Rivell John
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