GB2164439A - Plate heat transfer apparatus - Google Patents

Abstract

A generally rectangular heat transfer plate 1 has ports 5, 6, 7, and 8 adjacent the corners of the plate, bridge zones between the ports 5, 6, 7 and 8 and distribution regions 3 and 4, port recesses 5b, 6b, 7b and 8b to receive gaskets 5a and 8a to isolate the ports from the bridge zones and bridge recesses 5c, 6c, 7c and 8c to receive gaskets 5d and 8d to isolate the bridge zones from the distribution regions 3 and 4. In order to locate gaskets and possibly also strengthen the recesses, the bases 11 of the bridge and/or port recesses which are to receive gaskets may be provided with pressed dimples 12a of less height than the depth of the recess. The dimples 12 extend into the recess in an ungasketed recess, and out of the recess in a gasketed recess so as to abut the strengthen the ungasketed recesses. In order to strengthen the port and bridge areas, the bridge recesses 5c, 6c, 7c and 8c may undulate in and parallel with the plane of the plate towards and away from the associated ports. The port recesses 5b, 6b, 7b and 8b may likewise undulate towards and away from the associated ports. <IMAGE>

Description

SPECIFICATION Plate heat transfer apparatus This invention relates to sealing arrangements for plate heat exchangers and plate evaporators, hereinafter referred to collectively as plate heat transfer apparatus.

In such heat transfer apparatus, heat is transferred between two thin, broad streams, which may be both of liquid or one stream of liquid and one stream of vapour or two streams of vapour. In some cases one or both streams may have mixed liquid and vapour phases. The streams are separated by plates assembled in a spaced face-to-face relationship to provide flow spaces between the adjacent faces of the plates. The boundaries of the flow spaces are enclosed and sealed by flexible or resilient gaskets surrounding the flow spaces between the adjacent faces, and disposed between the flow spaces and entry and exit ports. The ports, in plate heat exchangers usually one at each corner of the plate, are similarly surrounded or part-surrounded by gaskets as appropriate to control the flow to and from the flow spaces.

Each gasket is normally of a one piece construction set within a pressed recess formed in the plate. The manufacture of the gasket is normally carried out in moulds, but according to the size of the plate or the manufacturing techniques used, the gasket may be assembled from two or more smaller components.

The gaskets are normally moulded of an elastomeric material.

The sealing force against the fluid pressure in the flow space is obtained by compression of the gaskets in a direction normal to the plate surface.

In order to prevent deflection of the plates along lines of weakness presented by long and straight lines of bending, the gasket recesses along the sides of the plate, which are effectively long and straight, are frequently provided with complex forms, involving lateral corrugation of one of the side walls of the recesses.

A conventional generally rectangular heat transfer plate with a port near each corner is normally regarded as having a main heat transfer zone covering a majority of the area of the plate. At each end, the plate has a distribution region, which is part of the heat transfer zone, over which the feed fluid is distributed from the port over the width of the plate, or is collected from the width of the plate and directed towards the port. In view of the different functions of the different areas of the plate, the arrangement of corrugations or other formations on them may be markedly different.

One port at each end of the plate is isolated from the flow space by a length of gasketing surrounding the port, which will be referred to hereinafter as the port gasket. Between each port and the distribution region is an area which will be referred to as the bridge zone, and normally the bridge zones associated with the isolated ports are also isolated from the flow space by lengths of gasket, which will be hereinafter referred to as bridge gaskets. The isolated bridge zones are thus doubly isolated and may be used as vented leakage spaces.

The bridge zones are notoriously difficult areas of plate design, along with the associated port and bridge recesses, primarily because, unlike the peripheral gaskets which are provided in every plate and therefore are aligned and in juxtaposition to provide interplate support through the pack, the port and bridge gaskets are only provided at any one port, in alternate plates, which leads to reduced interplate support.

It has long been a source of design difficulty to provide adequate interplate support at these zones to prevent plate deflection which might lead to gasket failure. To this end, recourse has been had to such expedients as welding a castellated strip onto the plate without the gasket to provide interplate support at the bridge gasket zone.

It is a further problem that the port and bridge recesses, which are not supported on both sides by gaskets, are not structurally strong.

It has been proposed in our GB-A-2128726 to overcome this problem by extending the bridge corrugations, at half height, through the port and bridge recesses. However, this has the disadvantage of reducing the depth of the gasket, and therefore its elasticity. Also, the flow passage through the open (ungasketed) recesses is significantly reduced and the partial disappearance of the gasket side wall reduces the lateral support of the gasket in the gasketed recesses.

It is an object of the invention to provide an improved arrangement of the port and bridge gasket regions to improve the mechanical strength thereof.

In accordance with a first aspect of the invention, there is provided a generally rectangular heat transfer plate having ports adjacent the corners of the plate, bridge zones between the ports and distribution regions, port recesses defined by walls and a base to receive gaskets to isolate two of the ports from the bridge zones and to be ungasketed when associated with the other ports, and bridge recesses defined by walls and a base to receive gaskets to isolate two of the bridge zones from the distribution regions and to be ungasketed when associated with the other bridge zones, in which at least the port and/or bridge recesses have their bases provided with localised dimples surrounded by metal of the normal level of the base and of less height than the depth of the recess, those dimples in the recesses to be gasketed being dimpled to increase the depth of the recess to receive convex dimples in the gaskets, and those dimples in the recesses to be left ungasketed being dimpled to decrease the depth of the recess so as to abut the dimples in the gasketed recesses on one adjacent similar plate.

All the bridge and port gasket recesses may be provided with dimples.

The dimples will normally be pressed into the metal forming the bases of the recesses during pressing of the plate.

The provision of dimples enhances location of the gasket, which will have corresponding dimples.

The port and/or bridge gaskets and their associated recesses may undulate in and parallel with the plane of the plate towards and away from the associated port.

In this way, the port and/or bridge gasket recesses may be strengthened to resist deflection caused by the rubber loading or by the operating pressure in the heat transfer apparatus of which the plate forms a part.

In accordance with a second aspect of the invention, there is provided heat transfer apparatus comprising a pack of plates according to the invention as set forth above.

The invention will be further described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is an elevation of one form of plate in accordance with the invention, with lateral undulation of the bridge recesses being shown in an exaggerated form; Figure 2 is a sectional and perspective view of a form of dimpled recess to be used without a gasket in a preferred form of the invention; Figure 3 is a view similar to Fig. 2 showing a form of dimpled recess to be used with a gasket; Figure 4 is a cross section taken through the recesses of four successive plates between the dimples: and Figure 5 is a view similar to Fig. 4 with the section taken through the dimples.

Referring first to Fig. 1, the plate 1 illustrated has a main heat transfer zone 2, two distribution regions 3 and 4, and corner ports 5, 6, 7 and 8. A peripherai gasket 9 runs in a recess round the outside of the ports. The ports 5 and 8 are isolated from the flow space zone by port gaskets 5a and 8a also mounted in recesses, and the ungasketed port recesses associated with ports 6 and 7 are shown at 6b and 7b. Each of the ports 5 to 8 has a bridge recess Sc to 8c, and the recesses Sc and 8c are occupied by bridge gaskets 5d and 8d. The zones between the bridge recesses Sc to 8c and the port recesses 5b to 8b are known as bridge zones.

The bridge zones associated with the ports 5 and 8 are isolated from both the port and the flow space zone, and are normally vented.

As so far described, the arrangement is generally conventional, and it will be appreciated that the heat transfer zone 2 and the distribution regions 3 and 4, as well as the bridge zones will normally have a pattern of corrugations or other formations, which contribute to the mechanical strength in addition to the thermal and hydrodynamic efficacy of the plate 1.

In order to strengthen the plate 1 in the region of the bridge recesses Sc to 8c, these are shown as being laterally undulated in and parallel with the plane of the plate towards and away from the corresponding ports 5 to 8. The showing of the undulations in Fig. 1 is exaggerated for clarity of illustration. The bridge gaskets 5d and 8d are designed to fit the corresponding recesses.

Similarly, although not illustrated in this form, similar undulations may be provided for the port gaskets and their recesses 5b to 8b.

Fig. 2 shows a preferred form of ungasketed port or bridge recess 10 having walls 10a of a substantially constant height and a flat base 11 in which localised dimples 12a, of a height less than the depth of the recess, are pressed in at spaced intervals. Dimples of this form are provided in ungasketed recesses, and, as will be seen from Fig. 3, dimples 12b depressed beyond the base 11 are provided in the recesses to be gasketed. The dimples 12a and 12b will all be of the same type in any one recess. It will be seen that each dimple 1 2a or 1 2b is completely surrounded by metal at the level of the plane of the base 11.

It will also be noted that the upper level of each wall 10a, where it starts to turn into the horizontal, may be interrupted by ends of corrugations 17. However, it will also be noted that such interruption does not significantly alter the effective height of the wall 10a.

The dimples 12a and 12b are intended to provide location for gaskets 14, which are only provided in alternate recesses through the plate, as can be seen from Figs. 4 and 5.

To this end, the gaskets have pips 14a and 14b to enter the dimples as shown in Fig. 5.

However, the dimples also provide interplate support in place of the omitted gaskets, and for this purpose the dimples 1 2a in the ungasketed recess will extend into the recess as shown in Fig. 2, and the gasketed recesses of Fig. 3 will have the dimples 1 2b extending out of the recesses in their own plates and extending sufficiently far to abut the underlying dimple 12a in the underlying plate as shown in Fig. 5.

Various other modifications may be made within the scope of the invention as defined in the appended claims.

Claims (7)

1. A generally rectangular heat transfer plate having ports adjacent the corners of the plate, bridge zones between the ports and distribution regions, port recesses defined by walls and a base to receive gaskets to isolate two of the ports from the bridge zones and to be ungasketed when associated with the other ports, and bridge recesses defined by walls and a base to receive gaskets to isolate two of the bridge zones from the distribution regions and to be ungasketed when associated with the other bridge zones, in which at least the port and/or bridge recesses have their bases provided with localised dimples surrounded by metal of the normal level of the base and of less height than the depth of the recess, those dimples in the recesses to be gasketed being dimpled to increase the depth of the recess to receive convex dimples in the gaskets, and those dimples in the recesses to be left ungasketed being dimpled to decrease the depth of the recess so as to abut the dimples in the gasketed recesses on one adjacent similar plate.

2. A plate as claimed in claim 1, in which at least those port and/or bridge recesses which are to receive gaskets have their walls of substantially constant height.

3. A plate as claimed in claim 1 or 2, in which all the bridge and/or port recesses are provided with dimples.

4. A plate as claimed in any of the preceding claims, in which the bridge recesses undulate in and parallel with the plane of the plate towards and away from the associated ports.

5. A plate as claimed in any of the preceding claims, in which the port recesses undulate in and parallel with the plane of the plate towards and away from the associated ports.

6. A heat transfer plate substantially as hereinbefore described with reference to the accompanying drawings.

7. Heat transfer apparatus comprising a pack of plates as claimed in any of the preceding claims.