Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Patent
1995-06-29
1998-03-10
Leo, Leonard R.
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
165164, F28D 716
Patent
active
057250510
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a heat exchanger comprising ducts of the first type and ducts of the second type, wherein ducts of both types are at least partly mutually adjacent.
Such heat exchangers are generally known.
An example of a heat exchanger is a recuperator which is used for instance to recover waste heat from a process in order hereby to lessen the heat (or cold) consumption. In a recuperator the media from which heat is extracted, respectively to which it is transferred, are mutually separated. This in contrast to a so-called regenerator wherein the heat is transferred via an intermediate heat capacity by causing both media to flow therethrough alternatingly.
Known heat exchangers are frequently embodied as so-called cross-current heat exchangers, plate heat exchangers or tube and shell heat exchangers, wherein the counterflow principle is applied.
These devices have in common that the required power can only be realized in a large volume. Another drawback lies in the fact that greater flow losses occur. Yet another drawback lies in the fact that the temperature distribution in such known heat exchangers often results in stresses in the material so that the choice of materials is limited. This results generally in increased cost.
Another drawback of the tube and shell heat exchanger is that a large number of pipes must be connected to a manifold, which results in higher costs, while in addition a uniform flow distribution is difficult to obtain on the shell side, whereby the efficiency is adversely affected. Another drawback is that the flow is too turbulent to obtain a sufficiently high heat transfer, whereby a high flow resistance and vibrations are generated.
From GB-A-2170586 a heat exchanger is known, comprising ducts of a first type and ducts of a second type, the ducts of both types having an identical cross-section, being parallel and at least partially mutually adjacent arranged in a housing, and in cross-section arranged in a regular pattern, the ducts being separated by separating walls wherein substantially each of the separating walls is bounded on at least one side by a duct of the first type and by a duct of the second type at the other side, the heat exchanger comprising at least one connecting piece adapted for connecting one end of the ducts of the first type to a first connection and one end of the ducts of the second type to a second connection.
However, in this prior art heat exchanger the ducts of the first type and of the second type have a different configuration.
The object of the invention is to provide a heat exchanger wherein the greatest possible part of the energy is transferred from the heat generating medium to the heat absorbing medium, wherein the above stated drawbacks are obviated.
This object is achieved in that substantially each of the ducts of the first type is at all its sides adjacent to a duct of the second type.
Further it is noted that from GB-A-2 170 586 a heat exchanger is known, in which the ducts of the first and the second types have the same cross-section and in which substantially each of the ducts of the first type is at all its sides adjacent to a duct of the second type. However, the ducts of both types are not connected with connecting pieces making a difference between the ducts of the first and the second types.
As a result of the steps according to the invention the heat transfer coefficient in the laminar flow and the heat transferring area increase considerably at a constant cross sectional area of the device in which the ducts are arranged. Due to the resulting large heat transferring power the temperature differences between the incoming and outgoing gas flows are small as seen in the cross section, so that due to the large heat exchanging surface area the density of the heat flow perpendicularly of the duct wall is low. The temperature gradient therefore extends substantially in the lengthwise direction of the ducts, whereby thermal tensile stresses in the material are avoided.
It has also been found that in the case of laminar flow in
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patent: 4116271 (1978-09-01), DeLepeleire
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patent: 4601332 (1986-07-01), Oda et al.
patent: 4913776 (1990-04-01), Finnemore et al.
Leo Leonard R.
Level Energietechniek B.V.
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