Plate heat exchanger

Details Plate heat exchanger Plate heat exchanger

1997-12-17

1999-10-19

Flanigan, Allen

Heat exchange

With repair or assembly means

Guide

165167, 165DIG365, 165DIG367, F28F 308

Patent

active

059672277

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention concerns a plate heat exchanger comprising a plurality of rectangulary plate elements and intermediary gaskets to be held clamped in a stack, wherein the plate elements and gaskets define flow channels for the heat exchanging media flowing through the plate heat exchanger, which flow channels are to be filled via aligned inflow and outflow openings in the plates.


CLOSEST PRIOR ART

The commonly used plate heat exchangers of today generally comprise 4-600 plates in the same stack, but it is not unusual that as many as 1000 plates are clamped together in the same heat exchanger stack.
Due to often high pressures and temperatures in the heat exchanger media during use, it is on the one hand necessary that the plates and intermediary gaskets of the stack are held together by means of high clamping forces, so that tightness of the flow channels is ensured.
But on the other hand, the clamping forces, which can assume very high values on some of the plates in the stack, inevitably apply high lateral forces on the plates in question with the danger of laterally displacing these, so to say out of the stack.
At worst, the result can be subsequent uncontrolled distortion of the plate stack and therefore leakage in the flow channels.
Therefore, experience has shown that it is of the outmost importance that the plates are always properly aligned, both during clamping action and during subsequent use to avoid distortion of the plate stack and thereby undesirable failure of the heat exchanger.
The slightest misalignment of the plates in the stack also cause misalignment of the succeeding intermediary gaskets. The high clamping force will therefore be unevenly distributed from one gasket to the next following gasket in the stack, which gives rise to transverse forces acting between the plates and the intermediary gaskets, involving a risk of leakage in the flow channels. In extreme cases tilting of the gaskets can take place and damage of both the gaskets and the plates can occur as a result thereof.
To avoid misalignment of the plates in the stack, it is known to guide the plates in alignment arrangements of different configurations.
A commonly used alignment arrangement comprises upper and lower guide bars connected at the ends to clamping means. The upper and lower guide bars engage in openings or cutouts symmetrically placed at the upper and lower edges of the plates, respectively.
Owing to the inevitable manufacturing tolerances of the cut-outs, of the depressed plates and of the gaskets disposed therebetween, a uniform action of the high clamping force over the entire plate area, and therefore over the plate periphery, is impossible. Individual plates in the stack are therefore influenced by forces directed transversally to the clamping direction.
With the above-mentioned design, the transverse forces can increase to such an extent that leakage occurs between the plates and the adjacent gaskets, or even such that the plate in question breaks out laterally of the stack with respect to the guide bars.
The transverse forces further give rise to frictional forces acting between the guide bars and the plate material adjoining the cut-outs, whereby the plates are prevented from further sliding on the guide bars when the clamping force is increased even higher.
The frictional forces are therefore accumulated over the length of the plate stack, which inevitably leads to an increase in the clamping force acting on the plate in question, involving the further risk of the plate being pressed laterally out of the stack.
A further aggravating factor giving rise to higher transverse slidability of the plates, is that the opposing surfaces of the gaskets and the plates often comprise frictionally reducing compounds for easier disassembly of the stack.
In order to avoid the above-mentioned problems, several other constructions of heat exchanger plates with alignment arrangements in the form of mutually engaging plate parts have been proposed.
One of these constructions is described in

REFERENCES:
patent: 2550339 (1951-04-01), Eherman
patent: 4373579 (1983-02-01), Jernqvist et al.

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