Heat exchange – With first fluid holder or collector open to second fluid
Patent
1991-09-16
1993-07-13
Davis, Jr., Albert W.
Heat exchange
With first fluid holder or collector open to second fluid
165167, 165903, F28F 1308, F28F 308
Patent
active
052264742
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a plate heat exchanger for evaporating a fluid, comprising a package of towards each other abutting rectangular and essentially vertically arranged heat transfer plates, delimiting flow spaces between themselves and being provided with corrugation pattern in the shape of ridges and grooves, said ridges intersectingly abutting each other in at least a part of each flow space and forming a number of supporting points between adjacent heat transfer plates, wherein alternate flow space forms an evaporating passage, which evaporating passage has an inlet for fluid at its lower portion and an outlet for fluid and generated vapour at its upper portion near one of the vertical sides of the heat transfer plates, and remaining flow spaces form passages for a heating fluid, which passages have inlets at their upper portions near the other vertical sides of the heat transfer plates and outlets at their lower portions.
At a known plate heat exchanger of this kind, described in DE-A1 3721132, the main part of the heat transfer portion of each heat transfer plate has one and the same kind of corrugation pattern over its entire surface. This has shown ineffective referring to the heat transfer capacity of the plate heat exchanger.
At the previously known plate heat exchanger an outlet duct for fluid and generated vapour extends further through the package of heat transfer plates, which outlet duct is formed of aligned openings of the heat transfer plates. The openings have been made as great as possible to minimize the flow resistance in the outlet duct for the produced vapour. In practice a large part of the upper portion of each heat transfer plate has been used for such opening. As also an inlet duct, intended for the heating fluid, must extend through the upper part of the package of heat transfer plates, it has not been possible to use the entire width of the heat transfer plates only for the outlet duct. This has resulted in that flow paths of different length have been formed in each evaporating passage between its inlet and its outlet for different parts of supplied fluid and vapour generated therefrom.
Owing to that the known heat transfer plates have one and the same kind of corrugation pattern over their heat transfer portions and thereby in each evaporating passage cause equal flow resistance per unit of length of each flow path for fluid and generated vapour, the total flow resistance will be largest along the longest flow path. Consequently, the smallest amount of fluid and vapour passes this path. This will lead to that not all of the fluid will be exerted to the same heat treatment and that the risk of drying out exists along the longest flow path, above all, near the inlet of the heating fluid.
An object of the present invention is to increase the efficiency of a plate heat exchanger of the introductory described kind, and to provide an uniform quality of the discharged fluid and generated vapour.
This object is obtained according to the invention in that in each evaporating passage, close to its inlet for fluid, at least one heat transfer plate is provided with a number of zones having different corrugation pattern, arranged adjacent to each other between the vertical sides of the heat transfer plate, the ridges and grooves of the heat transfer plates in the area of said zones forming different angles against the main flow direction of the fluid in the evaporating passages, which angles are chosen in such a way that the ridges and grooves in consequence of their different direction cooperate to provide a flow resistance in each evaporating passage, in its main flow direction, which gradually decreases from said one to said other vertical side of the heat transfer plate.
It is previously known that the heat transfer between each of two heat transfer plates and a heat transfer fluid, flowing through a passage between the plates, is influenced of how the towards each other abutting corrugation ridges of the heat transfer plates cross each other and extend in relation to the
REFERENCES:
patent: 2872165 (1959-02-01), Wennerberg
patent: 4307779 (1981-12-01), Johansson et al.
Alfa-Laval Thermal AB
Davis Jr. Albert W.
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