Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Patent
1990-06-06
1992-06-16
Rivell, John
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
165167, F28F 304
Patent
active
051217929
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a counterflow heat exchanger having exchange areas which are made of plates and are arranged between inflow channels narrowing in the inflow direction and outflow channels widening in the outflow direction.
In heat exchangers, even in counterflow heat exchangers, the problem occurs that heat exchange takes place only near the surfaces of a heat exchanger. Therefore heat exchange takes place only within a relatively small zone, namely inside the boundary-layer thickness. The medium which is thus cooled or heated then mixes with the medium which is not cooled or heated. Since this mixing action is irreversible, a significant deterioration in the efficiency takes place overall. On account of the conventional, relatively large distances between the heat-exchanger areas, the heat exchangers then also have a considerable size, which in turn leads to stability problems if the heat exchangers are to be used at high pressures.
A previously known heat exchanger in which the distances between the heat-exchanger areas are relatively small (U.S. Pat. No. 4,042,018) is manufactured from plates folded in a zigzag shape. This heat exchanger is of relatively complicated construction and has the disadvantage that the fluids do not sweep uniformly over the exchange areas but seek the shortest path (broken arrows on the left in FIG. 1 of the citation) so that no optimum heat exchange takes place.
The object of the invention is to create a heat exchanger of simple construction which is very effective.
The solution according to the invention consists in the panels being arranged in stacks of individual plates, in the exchange areas being arranged at an oblique angle relative to the stack direction, and in two adjacent plates each, on both sides of the stack, enclosing channels which alternately form on one side outflow channels and inflow channels and on the other side in each case the corresponding inflow channels and outflow channels.
Since the heat exchanger is manufactured from stacks of individual plates, it can be assembled from these individual plates in different form according to requirement. Since the exchange areas are arranged at an oblique angle relative to the stack direction, the channels here have a smaller width than corresponds to the distance between the plates in the stack direction. Better heat exchange is thereby obtained. Since the inflow and outflow channels are arranged on opposite sides of the stack, the fluids flow completely through the stack from one side to the other so that the entire heat-exchanger areas are swept over. Since the channels narrow in the inflow direction or widen in the outflow direction, optimum flow conditions are obtained. In the rear part of the channels, where only a little flow takes place, these channels can be smaller than in the front part where greater fluid quantities flow.
In order to obtain the same flow resistance overall, the inflow and outflow channels on one side expediently have a maximum cross-section which is equal to the flow cross-section of the channels between the exchange surfaces, the channels on the opposite side narrowing down to zero cross-section.
Manufacture is particularly efficient if the heat exchanger consists of plates which are identical but are assembled alternately with different orientation. Thus only one press for one type of plate needs to be manufactured, which plates are then assembled in such a way as to be alternately orientated relative to the heat exchanger.
In an advantageous embodiment, the channels between the exchange surfaces, viewed in the inflow or outflow direction, have a V-shaped cross-section. In this case, an inflow channel and the corresponding outflow channel face one another on opposite sides of the heat exchanger.
If the exchange surfaces are corrugated, the heat-exchanger area is increased on the one hand. If the corrugations still touch each other, the plates are mutually supported, as a result of which the overall size can likewise be reduced and thinner plates can be selected.
REFERENCES:
patent: 1710818 (1929-04-01), Fosbury
patent: 2429508 (1947-10-01), Belaieff
patent: 3403724 (1968-10-01), Gutkowski
patent: 3525390 (1970-08-01), Rothman
patent: 4512397 (1985-04-01), Stark
patent: 4556105 (1985-12-01), Boner
patent: 4586565 (1986-05-01), Hallstrom et al.
Leo L. R.
Rivell John
SITA Maschinenbau- und Forschungs GmbH
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