Heat exchange – With external support
Patent
1998-03-24
2000-08-08
Leo, Leonard
Heat exchange
With external support
165 76, 165167, 165906, F28F 900
Patent
active
060987014
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION AND PRIOR ART
The present invention refers to a plate heat exchanger comprising a stack of heat transfer plates provided between two end pieces and each having an essentially plane extension, each end piece having an inner surface facing said heat transfer plates and an outer surface facing away from said heat transfer plates and extending from one side to another of the end piece, the plate heat exchanger being compressed by means of at least one member extending around the end pieces and the heat transfer plates in such a manner that said member abuts said outer surface of each end piece in order to prevent the retreat of the end pieces from each other.
A conventional plate heat exchanger comprises a stack of heat transfer plates being compressed between two end pieces or end plates by means of two or more bolts or tightening bars. The bolts extend between holes extending through the end plates in their outer regions and outside the stack of heat transfer plates compressed between the end plates. The internal pressure of the heat exchanger acts on the end plates and since the bolts are located outside the pressure-loaded surface of the end plates, there are large bending stresses in the end plates, which may result in a considerable deflection of the end plates. Such a deflection leads to a play in the plate stack, which in turn influences the thermal performance and, to a certain degree, also the fatigue strength of the plates. To compensate for this it is necessary to use end plates having a significant thickness of material already by relatively moderate working pressures. Consequently, the plate heat exchanger becomes heavy and the manufacturing cost is relatively high.
JP-A-62 062 186 discloses a plate heat exchanger of the initially defined type, comprising a stack of heat transfer plates provided between two end plates. Each end plate comprises a planar inner surface, facing the heat transfer plates, a planar outer surface, and edge surfaces connecting the inner and outer surfaces. A compressing member in the form of a belt-type thin sheet extends around the plate heat exchanger. Said sheet is sharply bent around the corners formed by the outer surface and the edge surfaces. Due to this sharply bent corners the inherent stresses in the compressing are not negligible. Moreover, bending stresses will exist in the end plates, resulting in a deflection of the end plates in a central portion thereof. Consequently, the plate heat exchanger disclosed in JP-A-62 062 186 is not able to withstand high internal pressures.
In comparison to this Japanese prior art, JP-A-62 062 187 discloses a somewhat modified plate heat exchanger comprising longitudinal ribs provided on the outer surface of the end plates. The thin sheet of the compressing member extends around the plate heat exchanger and abuts a straight edge surface of the ribs in such a manner that the thin sheet is bent around the ribs. As in JP-A-62 062 186, the thin sheet is sharply bent around the corners of the end plates.
SE-B-343 383 discloses a plate heat exchanger having a stack of heat transfer plates provided between two end pieces, each end piece comprising a curved outer surface facing away from the heat transfer plates and a plane inner surface facing the heat transfer plates. The curved outer surface has a dome-like shape, i.e. it is curved in all directions. Furthermore, each end piece is provided with a circumferentially extending flange having holes through which tightening bolts extend for keeping together the plate heat exchanger stack. In addition, one of the end pieces comprises a plate forming the plane inner surface and being hydraulically movable against the heat transfer plates in order to press these together.
SE-B-413 695 discloses packages of heat exchanger plates, said packages being intended to be placed in chambers of rotating heat exchangers. The heat exchanger packages are temporarily compressed by a band for facilitating the insertion of the packages in the chambers. When the heat exchan
REFERENCES:
patent: 1925475 (1933-09-01), Albohr
patent: 2428880 (1947-10-01), Kintner
patent: 3385353 (1968-05-01), Straniti et al.
patent: 3540531 (1970-11-01), Becker
patent: 3568765 (1971-03-01), Konrad
Alfa Laval AB
Leo Leonard
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