Heat exchange – With leakage collector
Patent
1994-03-08
1995-08-22
Flanigan, Allen J.
Heat exchange
With leakage collector
165167, F28F 308
Patent
active
054431158
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a plate heat exchanger comprising a plurality of stacked plate elements made of multi-layered sheet material, each of said plate elements having a plurality of holes which, when the plate elements are stacked, are aligned to form distribution channels for cavities formed between the stacked plate elements, with intermediary gaskets arranged between every two adjacent pairs of plate elements at areas which border the cavities and the aligned holes.
Plate heat-exchangers are used in many process fields where a fluid in liquid or gas form is heated or cooled to a suitable temperature during continuous flow through the plate heat exchanger. When a fluid is to be heated, it is caused to flow through a small passage in the plate heat exchanger, said passage having a large thermal contact face exposed to a heat emitting fluid which preferably passes through the plate heat exchanger in counterflow to the fluid for heating. When a fluid is to be cooled, the other fluid in the heat exchanger is heat absorbing.
This structure is well-known, but has some drawbacks since the individual plate elements are usually made of single-layered sheet material. Corrosion could cause the two fluids of the plate heat exchanger to be mixed, which will be inadmissible. It is therefore necessary to inspect the state of the plate elements regularly, which can only be done by disassembling the plate heat exchanger and inspecting each of the plate elements. This necessitates interruption of the process system in which the plate heat exchangers are used, and is also a very labor intensive routine. Furthermore, the fluids passing through the plate heat exchanger are often very corroding, and this disadvantageous property is additionally intensified by the operating temperature. In case of single-layered plate elements it is thus necessary to select the plate material according to the most aggressive of the fluids, which adds considerably to the material costs.
When a plate heat exchanger is used for e.g. cooling marine engine systems, hot engine water is cooled with cold sea water. As is known, sea water is very aggressive even to stainless steel, and extensive use is therefore made of plate elements manufactured from e.g. titanium or titanium alloys. Other uses of plate heat exchangers will e.g. be in the food industry, e.g. for heating fruit juice.
There is thus a need for a plate heat exchanger where through plate defects can be detected before the fluids in the plate heat exchanger contact each other. In recent years it has been endeavoured to use multi-walled plates as plate elements made of multi-layered sheet material, where in particular the double-layered plate elements are of great interest. Although there is substantial metallic contact, a liquid can leak between the respective sheet layers of the plate elements since the layers are only kept together mechanically, and corrosion of one of the plates can hereby be detected at a relatively early time since the liquid leaks from the leakage to the outer side of the-plate heat exchanger where the liquid can be detected after some time by inspection. It will thus be possible to detect a leakage and remedy such damage before the two different liquids in the plate heat exchanger become mixed.
This technique has a considerable drawback, since the plate elements have port holes so when the plate elements are stacked with gaskets between them to form fluid passages transverse to the plate elements, the rim of the port holes will face said fluid passages. There is thus a need for an effective seal of the rim of the port holes so that fluid from the fluid passages is prevented from leaking between the plate layers of the plate elements. This seal is usually obtained by welding the layers of the plate elements together around the port holes. This solution requires individual welding of the holes of the plate element, which adds to the costs even if welding is performed by a machine. For the sheet layers of a plate element to be welded together, they must have substanti
REFERENCES:
patent: 3157229 (1964-11-01), Wennerberg
patent: 4249597 (1981-02-01), Carey
patent: 4372375 (1983-02-01), Bond
patent: 4903758 (1990-02-01), Cowan
patent: 4976313 (1990-12-01), Dahlgren et al.
Bogesvang Soren E.
Pedersen Jorgen
APV Baker A/S
Flanigan Allen J.
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