Heat exchange – Conduit within – or conforming to – panel or wall structure – Opposed plates or shells
Reexamination Certificate
2000-07-07
2002-10-08
Flanigan, Allen (Department: 3743)
Heat exchange
Conduit within, or conforming to, panel or wall structure
Opposed plates or shells
C165S133000, C165S906000
Reexamination Certificate
active
06460614
ABSTRACT:
The invention concerns a flat, enameled, pouch-shaped heat exchanger that is useful for many purposes, especially processes involving strong chemicals such as those used in the chemical and pharmaceutical industries.
BACKGROUND OF THE INVENTION
Plate-type, enameled heat exchangers consist of a series of superimposed plates each defining a flat space, through which streams of two liquids of different temperatures flow alternately from one space to the next.
Heat exchangers such as this are described in Patent No. EP No. 0566208 filed by ABB LUMMUS HEAT TRANSFER BV and No. EP 0522360 filed by ROTHEMUHLE BRANDT KRITZLER.
The first invention consists of a block comprising a stack of enameled plates separated from one another by cross pieces, which may be formed in the elements that constitute a set of braces. The plates are enameled first and then joined at the edges or sealed along the perimeters.
The second invention consists of a stack of metal plates or sheets that are alternately flat and undulating. The wavy shape of the undulating metal pieces defines flat, adjacent channels between two successive pieces of metal providing passageways for fluids of different temperatures.
These exchangers are designed primarily for thermal exchange between two gaseous fluids. Their enamel coating provides increased corrosion resistance when potent condensing agents are used.
The condensing agents in these exchangers are neither massive in volume nor highly potent, and for this reason, the exchangers do not require the same degree of protection as those used in the chemical and pharmaceutical industries.
Heat exchangers currently used in the chemical and pharmaceutical industries and therefore subjected to strong chemicals typically consist of bundles of enameled tubes. Chemical exchangers of this type have been described in Patent Nos. FR 2392349 in the name of PFAUDLER and EP No. 0203288 in the name of TYCON Spa. The enameled tubes are either soldered or banded together onto terminal plates. They are also attached to these plates with a gasket seal. The tubes are either coated with enamel before attachment or coated together after attachment to the terminal plates. In the first instance, one seal is required for each tube, which increases the risk of leakage in proportion to the number of seals used.
In the second instance, coating the joined tubes afterwards is complicated by the large number of tubes that must be coated simultaneously.
Heat exchangers with flat elements to contain the fluid are particularly useful because they have a large heat exchange surface, but only one inlet and one outlet.
In addition, a thin, pouch-like shape provides very effective, rapid heat exchange.
Flat elements serving as heat exchangers are made primarily of metal, like a flat radiator. The metal pieces are bent to form a flat half-shell. Then two half-shells are joined at their peripheral edges, generally by electrical soldering, forming a thin longitudinal ridge.
A disadvantage shared by all these exchangers is that there are seams and assembly areas which also must be coated with enamel. For example, not only are there connections between the plate edges and the supporting structure, but there are also seals between the tube extremities and the flanges.
Coating these areas is problematic because of the raised portions and the mechanical properties of the surfaces. Moreover, flat exchangers have multiple connecting points on their lateral surfaces where two plates are joined. This uneven surface is not conducive to applying a regular coat of enamel. On the contrary, there is a considerable risk that a flawed, discontinuous surface will be produced, causing weak points in the enamel which will be quickly attacked in a corrosive environment, thus causing leaks. These difficulties require operators to take many precautions and to be constantly on the lookout for leaky areas.
In addition, larger dimension flat heat exchangers have multiple connection points on their lateral surfaces designed to ensure consistent spacing between the two pieces of metal and to make the entire unit mechanically rigid.
Enameling these areas requires considerable skill and care, and thus, if the exchangers are being mass produced, there is a high risk that the coating will be defective in this area. Only certain carefully selected workers possess the necessary skill and will take the care required, and thus, it is apparent that the enamel coating process increases product cost considerably.
SUMMARY OF THE INVENTION
The object of the present invention is to enamel-coat flat metal exchangers and render them resistant to chemical products, thereby opening up a vast field of industrial applications, especially in the fields of chemistry and pharmaceuticals.
REFERENCES:
patent: 1958899 (1934-05-01), MacAdams
patent: 2877000 (1959-03-01), Person
patent: 4203421 (1980-05-01), Bencic
patent: 4235281 (1980-11-01), Fitch et al.
patent: 4649894 (1987-03-01), Hoeffken
patent: 5174928 (1992-12-01), Cheng et al.
patent: 5465785 (1995-11-01), Adderley et al.
patent: 342254 (1922-06-01), None
patent: 0203288 (1986-12-01), None
patent: 0522360 (1993-01-01), None
patent: 0566208 (1993-10-01), None
patent: 582.898 (1924-12-01), None
patent: 1.324.655 (1963-03-01), None
patent: 2173424 (1973-10-01), None
patent: 2392349 (1978-12-01), None
patent: 80197 (1934-04-01), None
patent: 79/00068 (1979-02-01), None
patent: 91/11252 (1991-08-01), None
Castiglioni Antonio
Hamert Jean-Marie
Davis & Bujold P.L.L.C.
DE Dietrich Process Systems
Flanigan Allen
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