GB2063450A - Plate Heat Exchanger - Google Patents

Abstract

A heat exchanger of the plate type having a number of rectangular plates 7 and 10 superimposed one upon the other, each plate having flanges 8, 9 and 11, 12 respectively on opposed sides which co-operate to define alternate passageways for fluids, particularly gases, the plates being held in a frame 3, with blanking plates 4, 5 to define the entries to the passageways. No fins are provided in the passageways, but non-coincident dimples may be formed in the plates for mutual support and improved heat transfer. The assembly may be bonded using e.g. an epoxy resin. <IMAGE>

Description

SPECIFICATION Heat Exchanger This invention relates to a heat exchanger for exchanging heat between two fluids, particularly between two gas streams.

A known form of heat exchanger comprises an assembly of thin metal sheets arranged parallel with each other and forming the walls of fluid conducting channels, and secondary heat conducting surfaces formed by corrugated metal sheets or strips (known as gills) located between and attached at their ridges to the walls. One form of such a heat exchanger is disclosed in United Kingdom Patent No. 818 603.

The present invention relates to an effective but easily constructed heat exchanger in which sheets of conductive material are used without intervening gills.

According to the invention a heat exchanger has a core consisting of an assembly of stacked four-edged plates forming fluid passageways between the plates, the plate edges having flanges extending perpendicular to the plates, each plate having on two opposite edges a first pair of flanges which extend on one and the same side of the plate only, and having on the other two opposite edges a second pair of flanges which extend on the other side of the plate only, each plate having its first pair of flanges in sealing engagement with a corresponding pair of flanges on an adjacent plate on one side and its second pair of flanges in sealing engagement with a corresponding pair of flanges on an adjacent plate on the other side, so that adjacent fluid passageways in the assembly extend in crossed directions the passageways being empty of corrugated strips of gills.

The plates in the heat exchanger core may be of thermally conductive material, a wide choice of material being possible because welding or other form of metallurgical bonding is not a necessary feature of the construction.

Square or diamond-shaped plates are preferred, and rectangular plates are especially preferred for a reason which will be explained later.

Conveniently, sealing engagement between flanges may be made by closely fitting a pair of flanges of one plate inside a co-operating pair of flanges of an adjacent plate. For some purposes, for example when the heat exchanger is to be used with air streams in which a small leakage can be tolerated, a seal produced in this way may be satisfactory, but if desired the seal may be improved by treatment with a liquid sealant, eg an epoxy resin, and this may also have an anticorrosive effect. In cases where easy dismantling of the exchanger is not required a bonding agent may be used.

In a preferred feature of the invention flanges which fit inside the flanges of an adjacent plate have inwardly directed feet which engage the said adjacent plate. Thereby correct assembly is facilitated, and the feet also conbribute to sealing efficiency when a liquid sealant is applied.

Production of such feet by inwardly turning the edge of the flange also provides a ready means of controlling flange height.

Alternatively, the close fit between the flanges of adjacent plates may be relaxed to allow space for the edges of the flanges to be turned outwardly rather than inwardly.

In a further preferred feature the surfaces of the plates in the assembly are contoured. The contours may be to provide fluid flow guidance in preferred paths through the fluid passageways.

They may add strength and/or stiffness to the plates. They may provide spacing between adjacent plates. They may confer strength to the assembly of plates. They may increase the surface area of the plates for heat transfer. Conveniently such contouring may be effected by dimples in the plates.

The heat exchanger may further comprise end plates parallel with the core plates, and tie members linking the end plates. Such tie members may take the form of corner angle strips linking the end plates at each of their four corners respectively and abutting the corners of the core plates. By this means the assembly may be clamped firmly together.

As a further feature the heat exchanger may comprise baffle plates partially blocking a fluid entrance and exit to diminish the angle between the effective flow paths of the two fluids. Thus in the case where the core plates are rectangular the longer sides may be partially blocked by baffle plates positioned to produce an overall fluid flow verging towards a diagonal direction.

By means of baffle plates the fluid flow configuration may be made to approximate to counterflow. By suitable location of such baffles and/or plate surface contours, the heat exchanger may be made to approximate to cross, counter or parallel flow or multi-pass combinations of any of these configurations.

Compared with known forms of heat exchangers in which both plates and intervening gills are used the heat exchanger of the invention is economically advantageous. Besides being simpler and cheaper to construct it provides a greater degree of heat interchange per unit weight of metal, since virtually all of the metal of the core portion transmits heat directly between the two fluids.

A specific embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective drawing of a heat exchanger; Figure 2 is a perspective drawing of two core plates; Figure 3 is a perspective drawing of two core plates of a modified form; and Figure 4 is a perspective drawing of an alternative form of core plates.

As shown in Figure 1, the heat exchanger has thick rectangular base and top plates 1 and 2 respectively, spaced apart by four corner angle strips 3 which are secured to the base and top plates by screws, bolts, rivets or other convenient means depending on whether or not the facility for easy dismantling is required. Baffle plates 4 and 5 are similarly fixed to the longer sides of the structure in non-alignment. Stacked between the base and top plates is a series of rectangular core plates indicated generally by the numeral 6.

The core plates in the series 6 are alternated correspondingly to those shown in Figure 2.

Upper plate 7 shown in Figure 2 has upwardly extending flanges 8 along its shorter edges and downwardly extending flanges 9 along its longer edges. The lower plate 10 has downwardly extending flanges 11 along its shorter edges and upwardly extending flanges 12 along its longer edges. When assembled, the downwardly extending flanges 9 on the upper plate 7 fit within the upwardiy extending flanges 12 on the lower plate 10. Likewise, downwardly extending flanges 11 on plate 10 fit within upwardly extending flanges of the next lower plate in the series, this plate being identical with plate 7.

Interengagement of flanges in this manner results in blockage of all aiternate passageways between the plates at the two shorter sides, and in blockage of all other passageways at the two longer sides.

The heat exchanger is assembled by placing first a plate 10 (Figure 2) upon the base plate 1, and then positioning a plate 7 with its long flanges 9 fitting within the long flanges 12 of plate 10. Another plate 10 is then positioned with its short flanges 11 fitting within the short flanges 8 of the plate 7 and so on until the requisite number of plates have been assembled. The top plate 2 is then added. A jig may be used to square up the stack and to apply sufficient compression to give the correct stack height. The corner angle strips 3 and baffle plates 4, 5 are then affixed. The assembly may then be treated with a liquid sealant/anti-corrosion fluid, eg an epoxy resin, to assist in holding the flanges together where they meet, or a bonding agent may be used if desired.

In use the two shorter ends of the heat exchanger serve as entry and exit for a first stream of gas, which flows through the alternate open passageways between these ends. The unblanked portions of the longer sides serve as entry and exit for a second stream of gas, which flows in a generally diagonal direction through those passageways which are not taken by the first gas stream.

Figure 3 shows a modified pair of core plates 20 and 21. Both plates are formed with noncoincident dimples to confer strength and support to the plates and structure and to improve heat transfer. The long downwardly extending flanges 22 of the plate 20 are formed with inwardly turned feet 23. In assembly flanges 22 fit within the upwardly extending flanges 24 of plate 21 and the feet 23 contact the upper surface of plate 21. In a similar way the short flanges 25 of plate 21 have inwardly turned feet 26 which in assembly contact the upper surface of the plate immediately below 21.

Figure 4 illustrates a further modification to the core plates. Upper and lower core plates 27 and 28 are provided with flanges such as 29,30, 31 and 32 in which the flanges are provided with external steps such as step 33 on flange 29. The external step then nestles into the walls of the adjacent plate. Thus step 33 nestles against the inside of wall 34. Because the steps are outwardly directed rather than inwardly turned as with the arrangement shown in Figure 3, it is an easier operation to press the core plates. It may not, however, be quite as efficient from a sealing point of view.

Claims (14)

Claims

1. A heat exchanger having a core consisting of an assembly of stacked four-edged plates forming fluid passageways between the plates, the plate edges having flanges extending perpendicular to the plates, each plate having on two opposite edges a first pair of flanges which extend on one and the same side of the plate only, and having on the other two opposite edges a second pair of flanges which extend on the other side of the plate only, each plate having its first pair of flanges in sealing engagement with a corresponding pair of flanges on an adjacent plate on one side and its second pair of flanges in sealing engagement with a corresponding pair of flanges on an adjacent plate on the other side, so that adjacent fluid passageways in the assembly extend in crossed directions the passageways being empty of corrugated strips or gills.

2. A heat exchanger as claimed in Claim 1 in which sealing engagement between flanges is by closely fitting a pair of flanges of one plate inside a co-operating pair of flanges of an adjacent plate.

3. A heat exchanger as claimed in Claim 2 in which the pair of flanges is bonded to the cooperating flanges.

4. A heat exchanger as claimed in Claim 3 in which the bonding is by means of an epoxy resin.

5. A heat exchanger as claimed in any one of Claims 2 to 4 in which the flanges located inside the flanges of an adjacent plate have inwardly directed feet which engage the said adjacent plate.

6. A heat exchanger as claimed in any one of Claims 2 to 4 in which the flanges located inside the flanges of an adjacent plate have outwardly directed feet which engage the said adjacent plate.

7. A heat exchanger as claimed in any one of Claims 1 to 6 in which the surfaces of the plates are contoured to space the plates.

8. A heat exchanger as claimed in Claim 7 in which the contours provide fluid flow guidance in the paths through the fluid passageways.

9. A heat exchanger as claimed in Claim 7 or 8 in which the contours comprise dimples.

10. A heat exchanger as claimed in any one of Claims 1 to 9 in which the plates are rectangular in plan view.

11. A heat exchanger as claimed in Claim 10 in which there is provided end plates parallel with the core plates and tie members linking the end plates.

12. A heat exchanger as claimed in Claim 11 in which the tie members are angled corner strips linking the end plates at the four corners and abutting the corners of the core plates.

13. A heat exchanger as claimed in Claim 1 2 in which there is further provided baffle plates partially blocking a fluid entrance and exit to diminish the angle between the effective flow paths of the heat exchanger.

14. A heat exchanger as claimed in Claim 13 in which the longer sides of the core are provided with baffle plates, one at opposed ends of the side.

1 5. A heat exchanger as claimed in any one of Claims 1 to 14 in which the plates are formed of steel, aluminium or an aluminium alloy.

1 6. A heat exchanger substantially as herein described with reference to Figure 1, Figure 2, Figure 3 or Figure 4 of the accompanying drawings.