US 2687876 A
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Aug. 31, 1954 R. P. HYTTE PLATE TYPE HEAT EXCHANGER Filed Oct. 1'7, 1951 IN VEN TOR.
m WEW f w. v L m m o M M Patented Aug. 31, 1954 PLATE TYPE HEAT EXCHANGER Robert Pontus Larsson Hytte, Lund, Sweden, as-
signor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application October 17, 1351, Serial No. 251,689
This invention relates to plate heat exchangers and has for its principal object the provision of an improved exchanger of this type which provides a better heat transfer than is provided by conventional plates and yet is of simple construction.
In order to ensure good heat transfer through the wall separating a heat-yielding and a heatreceiving medium in a pasteurizer or other plate heat exchanger, it is important to keep the media on both sides of the wall in lively motion, so that all particles of the two media come into contact with the wall as much as possible. It is therefore desirable to produce a turbulent flow in the channels which the plates form for the respective media on each side of the aforesaid separating wall. In order to cause turbulence, however, the rate of flow must exceed a certain value. A turbulent motion is also promoted by suitable formation of the channel. If its form causes frequent changes in the direction of the flow, the tendency toturbulence is increased, and this is also the case when the cross sectional area of the channel varies rapidly in the direction of flow.
The average value of the cross section of the flow-passage is dependent on the average distance between adjacent plates, and a lower limit for the average distance is set by the gauge of the marginal gasket between adjacent plates. To obtain secure sealing and for other reasons, the gasket should have a certain minimum gauge or thickness which is generally not below 4 to 5 mm. On the other hand, to produce the desired turbulence, the plates should preferably not be spaced apart more than 2 mm. It is therefore important to form the plates in such a way that maximum turbulence is ensured at the given average thickness of the liquid layer. It has been endeavored to fulfill this requirement by so corrugating or otherwise forming the plates that they form between them comparatively wide chambers communicating with one another by comparatively narrow passages. This improves the conditions for turbulence, but it is not a matter of indifierence how the channels and passages are 9 formed.
According to the invention, the plates forming the flow courses are so corrugated that substantially triangular spaces are formed between the plates. These spaces communicate with one another through passages which, at their minimum cross-section, are bounded on one side by a fiat wall and on the other side by a wall broken by the corrugations, where the corrugation line limits the minimum cross-section. With this formation of the flow courses, the rate of flow will vary considerably at the same time as eddies are formed in the triangular spaces, causing a good. heat transfer. In addition, the corrugation of the plates is simple and permits of easy cleaning. The aforesaid flow spaces, which are triangular in section, can be formed by simply corrugating the plates in zig-zag. Two types of plates are required, having somewhat different corrugations, or in any event the corrugations should be displaced in relation to one another along the plate. As an alternative, the plates may be identical but alternate plates reversed end for end A suitable form of corrugation is one where the corrugations have the form of stairs with one side of each step being about twice as long as the other side. When two consecutive ridges of a plate corrugated in this way are connected by a straight line, a right-angled triangle is formed, one perpendicular of which is twice as long as the other. By juxtaposing two corrugated plates in such a manner that the long sides of the steps of one plate slope one way (for example, to the left) and the corresponding long sides of the steps of the other plate the other way (that is, to the right), a suitable triangular form of the flow spaces with suitable passages therebetween will result. The proportion between the two sides of the steps may vary in wide limits, and the angle between the two sides of the steps may also vary. By suitably selecting and combining these factors, flow spaces forming, in section, isosceles or equilateral triangles may be obtained.
With regard to the direction of flow of two adjacent liquid layers, the two streams may have either opposite main directions or the same main direction. The main direction of flow is preferably at right angles to the corrugations of the plates, but as an alternative it may be more or less obliquely directed in relation to these corrugations.
In the accompanying drawing, the single illustration is a schematic longitudinal sectional view of one embodiment of the invention. Referring to the drawing, the heat exchange plates I 2 and 3 are preferably rectangular and form together two juxtaposed flow spaces for the heatexchanging fluids. On either side of the plates are other identical plate (not shown) forming with those illustrated a complete set of plates for the heat exchanger. the usual sealing gaskets (not shown) are arranged between adjacent plates at their marginal portions, which preferably are not corrugated, and
It will be understood that the flow spaces for the respective fluids are connected in series or in parallel by throughfiow openings in corner portions of the plates, in the conventional manner. Two fluids flow in the spaces in the directions indicated by the arrows. The drawing shows the plates in a section taken at right angles to the lines along which the corrugations: extend; The plate I is: corrugated to form steps, one side 4 of which; in' cross-section; is about twice as long as the other side 5. Consequently, a longitudinal section of the corrugated plate forms azig-zag line havingv nearly right. angles between the sides of the steps. The corrugations of the plate 3 are identical with those of the plate I, whereas the plate 2is similarly cor-- rugated but with the corrugations displaced l'ongi tudinally (vertically in the drawing) in.rela.tion2 to those of the plates I and 3 and having the long sides 4 and short sides 5 sloping in opposite directions as compared with the corresponding sides; of the corrugations of the adjacent plates land 3.
In. the drawing, straight corrugation lines between the steps have-been assumed. It: is, how-- ever, sometimes advisable tov form protuberances, such; as bosses or. small corrugations 6 in the material. of the plates in orv close to the corrugation lines, because the turbulenceis then further augmented.
By-forming thev plates in accordance with the invention, it is possible: to make them wider than previously, because with the proposed formation of thev plates a. considerable reduction of the average velocity of. the flow in the channels between: the. plates will result, as compared with conventional designs. At a given throughput rate (that is, amount of fluid per unit-of time through the. channel) this means that the channel or flow space canbe made correspondingly wider; which, inLturn, results in anincrease of the heating-sur face for a given length of channel. As the total areaof the heating. surface is predetermined, this implies that, with a givenmaximum length ofthe channels, a larger plate width can be used and consequently the; number of heat exchange plates inthe. pasteurizer or: other apparatus canbe. reduced. This isv important especially in connection with small throughput rates, because a plate of the conventional construction is very narrow, which means that the marginal gaskets andthereinforcements at the edge occupya rela=-- tively. large percentage of the surface ofthe plate andthus-also of theplate material. As the. mar'- ginal portionsof the plate do not participate in the. heat exchange, it isof. course an. advantage to be able to. make themas small aspossible-and thereby save material. The invention enablesa better saving of material than has previouslybeen possible.
It will be apparent that the corrugations of: adjacent. plates form flow spaces! of. substantially triangular sections between the. plates. These spaces communicate with. each. other through. passages. 8 which. at; their minimum cross-sectional area, are eacln bounded on one side by, a flat wall. andonthe other. side. by a. wall i5 broken to form a corrugation. of the plate where the corrugation linelimitsrthe minimum cross-sectional area of the passage; 8..
1. A plate heat exchanger comprising aseriesof. spaced. heat exchange plates forming flowcourses, corrugations in the plates forming adj acent flow spaces of substantially triangular sections in the flow courses between the plates, each of said spaces communicating with an adjacent space through a passage having a minimum cross-sectional area bounded on one side by a flat wall of one plate and on the other side by a wall. of. another.- plate, said fiat wall forming a wall of" each' of two intercommunicating adjacent triangular flow spaces on each side of said one plate, said wall of the other plate being broken to form a= corrugation of said last plate where the corrugation line limits the minimum cross-secin'onalareaof said passage, the corrugations of each plate" extending general-1y transversely thereof and being offset, longitudinally of the plates',.with1respectto the corrugations of the adjacent plates, the walls forming the corrugations of" eachplate being non-parallel to the walls forming the corrugations of the adjacent plates.
2'. A. plate heat exchanger according to claim lginwhich saidcorrugations are in step-form.
3; A. plate heat exchanger according to claim 1,. in, which said: corrugations are in step-form, each step; in cross-section, having one side which is about twice as long as the other side of the step;
4:. Aplate heat exchanger according to claim 1, inwhich saidicorrugations arein step-form, each step,. inv cross-section, having one side which is about: twice aslong as the other side of the step, the. longer sides of the step-like corrugations of each. platebeing inclined in the opposite directionto said longer sides of each adjacent plate.
5. Aplate heat exchanger according to claim 1, comprising. alsoabosseson the plates in the regions oi the corrugation. lines thereof, to augment the turbulenceiof the fluid passing between adjacent plates;
6.. A plate heat exchanger comprising a series of spaced heat exchange plates forming flow courses, corrugations in the plates forming adjacentfiowzspaces otsubstantially triangular sections=in.the.;fiow courses between the plates, each of said spaces communicating with an adjacent space through a. passage having a minimum cross-sectional:areabounded on one side by a flat wall of; one plate and on the other side by a Wall of another: plate, said flat wall forming a wall; of each: of two intercommunicating adjacent triangulair flhw'spaces oneach side of said one: plate, said: wall of the other plate being brokento. form a. corrugation. of said last plate where the corrugation line limits the minimum crossesectionalz area of. said passage, the corrugations of each. plate being ofiset, longitudinally of. theplates, with. respect to the corrugations of the adjacent. plates, the walls forming the corrugations of each plate being non-parallel to the Walls forming; the: corrugations of the adjacent plates.
References Citedin the file" of this patent UNITED. STATES PATENTS Number; Name' Date 1;,89939882 Ruemelin Mar. 7, 1933 1,992.09! R. Seligman Feb. 19, 1935 FOREIGN PATENTS Number Country Date 548,196 Great.Britain Sept. 30, 1942 551,167 Great Britain Feb. 10, 1943