Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Patent
1981-03-09
1983-09-06
Richter, Sheldon J.
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
F28F 306
Patent
active
044023626
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to heat engineering and more particularly to plate heat exchangers.
DESCRIPTION OF THE PRIOR ART
Used as heat exchange surfaces in heat exchangers of the known designs are corrugated heat exchange surfaces formed by passages whose cross-sections are of rectangular and complex trapezoidal profiles and provided with short fins in the direction of flow of a heat carrying medium. From the thermohydraulic standpoint, the most effective mechanism of the heat exchange intensification is realized in the design of corrugated surfaces of this type. When a heat carrying medium flows in the regime characterized by the relationship: Re>Re.sub.c, where Re is the Reynolds number and Re.sub.c is the critical value of the Reynolds number at which the initial loss of stability occurs in the laminar structure of flow of the heat carrying medium, the separation of the heat carrying medium and generation of vortex systems take place in passages of the corrugated surface at the edges of corrugation fins. The vortex systems are commensurate in scale with half the thickness of the corrugation fins and are disposed in a wall boundary layer of the flow at a distance from the wall being commensurate with half the thickness of the fins. Thus the additional energy applied to the flow of heat carrying medium for intensification of the convective heat exchange in the passages of such a surface is spent only for turbulization of the wall boundary layer of the heat carrying medium, but not for turbulization of the flow core.
As a consequence, in a narrow wall boundary layer of a passage, in which the main thermal resistance to heat emission is concentrated, the value of turbulent conductivity and the value of heat flux density are small in magnitude. However, the presence of a vortex system in the wall boundary layer sharply increases the value of turbulent viscosity which leads to a rise in the value of turbulent conductivity and, consequently, to a rise in the value of heat flux density. As a result, these passages when compared with plane passages ensure a high value of the heat extraction coefficient at a moderate increase in consumption of energy for intensification of the convective heat exchange. Accordingly, the aforementioned makes it possible to substantially decrease the volume, mass and the cost of heat exchangers employing the heat exchange surface of such a type.
However, the decrease in the volume and mass of the plate heat exchangers is ensured not only by a highly effective process of intensification of the convective heat exchange realized in the passages of their heat exchange surfaces, but also by the use of highly compact designs of the plate heat exchange surfaces. The known designs of heat exchange surfaces with short fins in the direction of flow of the heat carrying medium do not feature high values of the surface compactness.
Well known in the art is a plate heat exchanger (cf. e.g., French Pat. No. 1,371,493, Cl. F 28d, Sept. 28, 1963), which employs a corrugated heat exchange surface formed by short fins arranged in the direction of flow of the heat carrying medium, corrugations being of rectangular shape. The corrugations are provided with flat crests. The corrugations following in the direction of flow of the heat carrying medium are displaced relative to the preceding ones through half the pitch of the corrugations. The corrugations arranged in succession are rigidly connected to one another through the flat crests.
Thus, there is formed a junction of a rectangular profile having sides equal to the thickness of the corrugation material and to half the base of the corrugation flat crest.
The design of a plate heat exchange surface heretofore described does not ensure the maximum possible compactness which is attained in the surfaces formed by triangular passages.
The surface formed by passages with a cross-section in the shape of an equilateral triangle has twice as great a value of the compactness.
There is also known a plate heat exchanger (cf., e.g., FRG
REFERENCES:
patent: 3079994 (1963-03-01), Kuehl
patent: 3229763 (1966-01-01), Rosenblad
patent: 3313343 (1967-04-01), Ware et al.
patent: 3768149 (1973-10-01), Swaney, Jr.
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