GB2110812A - Heat exchanger - Google Patents

Abstract

A cross-contraflow heat exchanger in which the cross-contraflow path is turned internally of the heat exchanger and in which there is a gap 20 between the paths of the cross- contraflow portion. <IMAGE>

Description

SPECIFICATION Heat exchanger This invention relates to heat exchangers and has particular reference to plate fin heat exchangers of the cross-contraflow type.

A plate fin heat exchanger as referred to in this specification is one having a plurality of heat exchange elements which are passage defining members in the form of plates which are located in face-to-face, spaced-apart, superimposed relationship tq define passages between the plates for the flow therethrough of heat exchange fluids, the passages comprising at least a first and second set respectively for the passage therethrough of a first and second fluid. The plates act to separate the passages of the at least two sets to form primary means to allow for heat transfer between the fluids through the plates.Fins, usually of corrugated material, are located between the plates and usually join to them in order to assist in spacing the plates apart, in strengthening the structure, in guiding the fluid flow and in forming secondary means for heat transfer augmenting that transfer by the primary means.

In a simple plate fin heat exchanger of rectangular shape one fluid passes through the heat exchanger from one side to the opposite side and the other fluid passes through the heat exchanger from the third side to the opposite side. Such a heat exchanger is known as a cross flow heat exchanger. An alternative form of heat exchanger is a cross-contraflow heat exchanger. In a cross-contraflow heat exchanger one fluid passes from one side to the opposite side in the manner described above whereas the second fluid passes through the heat exchanger from one side, is turned round within the heat exchanger and passes back to the same side again.

In a simple cross-contraflow heat exchanger a single U-shaped path is provided for the fluid. It will be appreciated, however, that in more complex designs an S- or sinusoidal shape can be provided with the second fluid repeatedly crossing from one side to the other of the heat exchanger.

By the present invention there is provided a cross-contraflow plate fin heat exchanger core comprising a series of plates in spaced, superimposed position to define therebetween at least two flow paths, one of the flow paths extending across the core from one side to the other side, the other flow path having at least one U-shaped portion extending from a third side transversely to the one flow path, being constrained to turn within the area of the plates and returning towards the third side, there being a gap between the legs of the U-shaped portion, the gap being formed in the plates with the one flow path extending from one side to the other side of the core across the gap, there being provided means to prevent fluid in the other flow path from passing into the gap.

Preferably there is provided in the space between the superimposed plates a plurality of fins. The fins are preferably corrugated. The fins in the one flow path extend parallel to that flow path but do not extend across the gap. The fins in the other flow path preferably extend along the legs of the U-shaped portion and are located parallel to the flow path of the one portion at the closed end of the U. There may be provided a sinusoidal flow path in the other flow path. Preferably there is provided an insulating member at the open end of the gap to prevent the egress of the one fluid from the gap to the surroundings of the heat exchanger. There may be provided flanges or distributor tanks on the sides of the heat exchanger and further flanges or distributor tanks at the ends of the other flow path.

The means to prevent fluid in the other flow path passing into the gap may comprise a spacer bar. The heat exchanger may be formed of aluminium alloy or a nickel alloy and may be brazed together. The heat exchanger may be vacuum brazed together.

By way of example only embodiments of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a perspective view of a heat exchanger core in accordance with the present invention; Figure 2 is a plan view of a plate and corrugated fin in one flow path; Figure 3 is a similar plan view of a plate and corrugated fin in a second flow path; Figure 4 is an enlarged detailed view of one corner of the gap in the heat exchanger of Figure 1; Figure 5 is a perspective view of a heat exchanger core provided with tanks and flanges; and Figure 6 is a schematic view of a further form of cross-contraflow heat exchanger in plan form.

Referring to Figure 1 this shows a heat exchanger core in accordance with the present invention. The heat exchanger core indicated generally by 1 is formed of a series of plates 2,3 which are interspersed with a series of corrugated members 4, 5.

Essentially the plates 2,3 define a series of passageways so that one fluid can pass through the heat exchanger in the direction of the arrow 6 and a second fluid can pass through the heat exchanger along a U-shaped path indicated in dotted by the arrow 7. The heat exchanger core is manufactured by assembling a stack of plates, such as plates 3, together with the appropriate corrugations 4 and 5 and the top and bottom of the heat exchanger is completed with single flat plates 2 and a lower plate, not shown in detail.

The form of the corrugations and the plates is shown in more detail in Figures 2 and 3. In Figure 2 a generally U-shaped plate 3 has mounted on it a corrugated member 4 which has a gap 8 corresponding to the gap in the plate. It can be seen that the corrugated member 4 is itself of essentially U-shape.

The lines of the corrugation run, as illustrated in Figure 2, across the width of the heat exchanger.

This would constrain fluid passing through the space between the plates 3 to go transversely across the gap 8. At the end 9 of the heat exchanger the corrugations extend completely across the width of the plate 3.

By comparison the corrugations in the other flow path are illustrated in Figure 3. Again the plate 3 has a gap 8 and the corrugations are formed in three separate portions as shown clearly in the drawing.

The first portion 9 and the second portion 10 constrain fluid to flow from right to left or left to right as illustrated in the drawing along the length of the plate. The corugated portion 11 does, however, constrain the fluid to flow vertically across the width of the plate. Thus by the provision of suitable external restraining members fluid can be constrained to flow in the direction of the arrows 12, ie along the corrugations 9, around the corrugations 11 and back along the corrugations 10.

Referring to Figure 4 this shows in more detail the construction of the heat exchanger core in the region adjacent the gap. Thus the plate 13 forms a heat exchange plate between a second or U-shaped path on its upper surface and a straight-through or first flow path on its lower surface. A U-shaped channel spacer member 14, which may, if required, be a solid member, is provided in the gap between plate 13 and plate 15. A corrugated member 16 extends across the width of the heat exchanger. Similarly a corrugated member 17 extends along the length of the heat exchanger between plate 15 and plate 18. A similar spacer member 19 is provided in the gap to constrain fluid passing along the U-shaped channel within the het exchanger core.It will be seen, therefore, that fluid passing across the core in the direction of the arrow 6 (Figure 1) can pass across the gap 8 from one open edge to the other but is unable to get into the flow path of fluid passing through the heat exchanger along path 7.

It will be appreciated that there is provided an insulating member (not shown) in the end of the gap as at 20 to restrict the escape of fluid passing along the line of arrow 6.

To complete the heat exchanger utilising the core of the present invention a pair of distribution tanks 21,22 would be welded to the heat exchanger core and flanges 23,24 could also be provided by welding or brazing as required.

It will also be appreciated that a cross-contraflow heat exchanger could be provided with an S- or sinusoidal flow path for a fluid as is illustrated in Figure 6. Thus the other fluid, in the case of a heat exchanger of Figure 6, would pass along the line indicated by arrow 25 and a series of gaps 26,27,28 would be provided to separate the flow paths of the heat exchanger. By turning the flow around within the heat exchanger heat exchange can take place between the fluids in the turn round region. This reduces the overall weight of the heat exchanger.

Claims (11)

1. A cross-contraflow plate fin heat exchanger core comprising a series of plates in spaced, superimposed position to define therebetween at least two flow paths, one of the flow paths extending across the core from one side to the other side, characterised in that the other flow path has at least one U-shaped portion extending from a third side transversely to the one flow path, being constrained to turn within the area of the plates and returning towards the third side, there being a gap between the legs of the U-shaped portion, the gap being formed in the plates with the one flow path extending from one side to the other side of the core across the gap, there being provided means to prevent fluid in the other flow path from passing into the gap.

2. A heat exchanger core as claimed in Claim 1 further characterised in that there is provided in the space between the superimposed plates a plurality of fins.

3. A heat exchanger core as claimed in Claim 2 further characterised in that the fins are corrugated.

4. A heat exchanger core as claimed in Claim 2 or Claim 3 further characterised in that the fins in the one flow path extend parallel to that flow path but do not extend across the gap.

5. A heat exchanger core as claimed in any one of Claims 2 to 4 further characterised in that the fins in the other flow path extend along the legs of the U-shaped portion and are located parallel to the flow path of the one portion at the closed end of the U.

6. A heat exchanger core as claimed in any one of Claims 1 to 5 further characterised in that there is provided a sinusoidal flow path in the other flow path.

7. A heat exchanger core as claimed in any one of Claims 1 to 6 further characterised in that there is provided an insulating member at the open end of the gap to prevent the egress of the one fluid from the gap to the surroundings of the heat exchanger.

8. A heat exchanger core as claimed in any one of Claims 1 to 7 further characterised in that there are provided flanges or distributor tanks on the sides of the heat exchanger and further flanges or distributor tanks at the ends of the other flow path.

9. A heat exchanger core as claimed in any one of Claims 1 to 8 further characterised in that the means to prevent fluid in the other flow path passing into the gap comprises a spacer bar.

10. A heat exchanger core as claimed in any one of Claims 1 to 9 when vacuum brazed together.

11. A heat exchanger core substantially as herein described with reference to and as illustrated by Figures 1 to 5 or Figure 6 of the accompanying drawings.