Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Patent
1980-12-23
1983-10-04
Richter, Sheldon J.
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
165166, F28F 304
Patent
active
044073577
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a heat exchanger for countercurrent heat exchange between two separated flowing media, consisting of a number of slots with common separating walls of thin sheet metal, preferably aluminium sheet metal, provided with profiles which cross each other on the adjacent separating walls and form spacer means at the points of crossing.
The invention is primarily intended to solve problems of heat exchange between two gaseous media, e.g. air/air, but it can be used to advantage for all types of heat exhange.
Heat exchangers with non-planar heat exchanger surfaces are known per se, e.g. provided with wave-shaped corrugations intended to break the boundary layer occurring during flow past the heat exchanger surfaces preventing or making more difficult the heat transfer. It has, however, been shown that this does not have any significant effect, especially as regards heat exchange between gaseous media.
It is also known to fold an endless metal sheet in 180.degree. folds at even spacing to produce a package which, after being placed in a box and sealed at the ends, forms a heat exchanger with ducts, with every other channel opening towards one longside and every other channel opening against the opposite longside.
A heat exchanger of the type described above does not, however, provide any essential improvement in efficiency as compared with conventional heat exchangers, and as far as is known at the time of the present application there is no heat exchanger which is as highly suited for heat exchange between two gaseous media.
To improve the thermal exchange constant in heat exchange between two gaseous media which flow separated on either side of a common separating wall, the flow must be able to be affected so that boundary layers preventing heat transfer do not occur. Turbulence, however, must not be created since this results in high pressure drop at high heat exchange constants.
The purpose of the present invention is thus to achieve a heat exchanger with a significantly improved temperature efficiency in relation to previously known exchangers and which is especially well suited to heat exchange between gaseous media.
Another purpose of the invention is to achieve a heat exchanger which, with unchanged capacity, can be manufactured at much lower cost and which can be made smaller than conventional heat exchangers.
A more specific purpose of the invention is to achieve a heat exchanger which can be adapted to the desired flow rate so that a flow pattern is obtained which results in the temperature efficiency being significantly higher than in previously known heat exchangers.
This is achieved by means of the heat exchanger according to the invention, which is characterized in that its heat exchanger surfaces are formed by the two sides of the common separating walls for the two media;
that the profiles consist of a ridge and a depression and form an angle relative to the intended direction of flow through the heat exchanger, the profiles in each individual separating wall running parallel with each other with intermediate flat sheet metal portions, and that a ridge on one side of the separating wall corresponds to a depression on its other side;
that the height of the ridges above the flat sheet metal portion corresponds to half the depth of the depressions, measured from the top of one ridge to the bottom of the adjacent depression;
that the distance between the foot of the ridge and its top in the plane of the flat sheet metal portion is the same for the ridges on both sides of the separating wall, whereby the angle which the ridge forms relative to the flat sheet metal portion in the flow direction will be the same on both sides of the separating wall; and
that the portion of the separating wall which extends from the top of the ridge to the bottom of the depression forms an angle with the flat sheet metal portion which is adapted in relation to the Reynolds number at which the heat exchanger is to be used, so that circulation but not turbulence occurs in the depression at sai
REFERENCES:
patent: 2019351 (1935-10-01), Lathrop
patent: 2940736 (1960-06-01), dman
patent: 3151675 (1964-10-01), Lysholm
patent: 3451474 (1969-06-01), Cox
patent: 3640340 (1972-02-01), Leonard et al.
patent: 4254827 (1981-03-01), Forster et al.
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