GB2127535A - Heat exchanger - Google Patents

Abstract

A heat exchanger principally intended for waste heat recovery comprises a set of cores (2, 3, 4, 5), typically of a plate-fin construction, which are slidably located in a framework (1). Each core may be removed for cleaning or replacing purposes. The cores are retained in the framework by means of flexible sheets (17, 18) secured to the framework and to flanges (21) on the cores, the flexible sheets both sealing the front and back panels of the heat exchanger and allowing expansion of the cores without resultant cracking of the heat exchanger. <IMAGE>

Description

SPECIFICATION Heat exchanger This invention relates to heat exchangers and has particular, but not exclusive, reference to heat exchangers for use in waste heat recovery. The invention has particular reference to modular heat exchanger systems in which the heat exchanger cores are removable for replacement or cleaning purposes.

Modular heat exchanger systems for waste heat recovery have been proposed in which the heat exchanger cores are manufactured from a plurality of plates and fins. Typically a series of aluminium or stainless steel plates are separated by sets of corrugated fins which both space the heat exchanger plates and enhance thermal transfer from one fluid flow path to the other. Side strips are provided along each side of the flow paths to prevent intermingling of fluid from one flow path to the other. Typically the heat exchanger cores would be manufactured by brazing, such as by salt dip brazing or by vacuum brazing in the case of an aluminium core.

By the present invention there is provided a heat exchanger assembly including a framework and a pair of side panels arranged so as to define a first fluid flow path for a first fluid and a second fluid flow path for a second fluid, the two flow paths being arranged at an angle to one another, preferably a right angle, the framework including support means for at least two heat exchanger cores which can be slid into and removed from the framework, a restraining system for the cores comprising a flexible planar sheet which has a number of apertures not less than the number of cores, the sheet being secured to the framework and the periphery of an aperture restraining and locating the periphery of a core.

Preferably the number of apertures is equal to the number of cores.

Preferably the periphery of each aperture is connected to the periphery of a core. The cores may have a flange on each end to which the periphery of the aperture is connected. The connection may be by screws or bolts. There may be a sealing layer between the flange and the periphery of the aperture.

Preferably.the cores are formed by a plate fin construction and each core would include a plurality of plates separated from one another by corrugated fins which are bonded to the plates.

Side strips would be provided by define flow paths in the core.

By way of example 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 in accordance with the present invention; Figure 2 is a detailed front view of the heat exchanger of Figure 1 with a portion of the front plate removed; and Figure 3 is a view of Figure 2 along the arrow III.

Referring to Figure 1 this shows a framework 1 of a waste heat recovery unit incorporating four heat exchanger cores 2, 3, 4 and 5. For reasons of clarity details of core 2 only are shown in the drawing. It will be appreciated that cores 3, 4 and 5 are identical to core 2. The core is made up of a series of plates 6, 7, 8 which are separated by corrugated fins 9, 10. Side spacers 11 and 12 define flow paths within the heat exchanger core as is well known in the art. It will be seen, therefore, that the core permits a first fluid to flow through in the direction of arrow 1 3 and a second fluid to flow through in the direction of arrow 14. Typically the fluid flowing in the direction of arrow 1 4 would be an exhaust gas and the fluid flowing through in the direction of arrow 13 would be air being heated.The framework 1 provides slides by means of which the cores 2, 3, 4, 5 are supported in the framework and may be slid in and removed. To provide a fluid-tight seal at the front and back of the heat exchanger (the side panels 1 5 and 1 6 together with the framework 1 defines the two main flow paths) front and back panels 1 7 and 18 are provided.

Both the front and back panels 17 and 1 8 are essentially both identical in form and, therefore, only panel 1 7 will be described in detail. The panel has four apertures which coincide with the cores 2, 3, 4 and 5. The panel is bolted to the framework by means of bolts 19, 20 and is bolted to flanges 21 on the heat exchanger core by means of bolts 22. If required a sealant may be provided between the periphery of the apertures and the flanges 21.

The use of such a flexible sheet 1 7 enables the expansion of the cores to be accommodated by flexing of the sheet. It also means that the differential expansion of the heat exchanger cores can be accommodated. For example, the upper cores 2 and 3 may operate at a slightly lower temperature than the cores 4 and 5.

The construction of the heat exchanger shown generally in Figure 1 is illustrated in more detail in Figures 2 and 3.

Considering Figure 2 this is a view in more detail of the front face of the heat exchanger with the left hand side of the flexible panel 1 7 removed.

The framework 1 is provided with a series of holes 23 by means of which the flange 24 can be secured into a ducting system. The panel 1 7 is bolted as at 20 to the flange 24 through holes such as 25. The heat exchanger cores 3 and 5 are provided with integral flanges which are bolted to the panel 1 7 via bolts positioned at positions such as 26. If required a reinforcing framework 27 matching the flange (not shown) on the heat exchanger cores can be provided around the periphery of the holes in the panel 17.

The framework includes horizontal members 28 on which are located runners 29 to support the heat exchanger cores. The runners are shown on the left hand side of Figure 2. The left hand side also shows more clearly the flanges 21 around the heat exchanger cores 2 and 4. It can be seen that when the end panel 17 is removed the heat exchanger cores may simply be slid in and out along the runners 29. Once the heat exchanger cores have been positioned in situ in the framework 1 the front panel 17 is located onto the framework 1 and is screwed to it. The panel is also screwed to the flanges 21 to complete the assembly.

Referring to Figure 3 this shows a plan view of the top of a heat exchanger along the arrow Ill of Figure 2. The framework includes vertical corner posts such as 30, 31 to which the runners 28, 29 are connected. The panel 17 may include a sealing washer between the flanger 21 and the panel itself. Such a washer is shown clearly at 32 between the front panel 17 and the end flange 21. It may not be essential to bolt the back of the heat exchanger to the panel 1 8. It may be that sufficient resilience in the panel 17 will firmly locate the heat exchanger against the end panel 18.

The right hand portion of Figure 3, which shows the top of the heat exchanger assembly without any partial removal, as occurs on the left hand side, shows that the upper end of the heat exchanger framework is provided with flanges 32, 33 by means of which the upper end may be located in a suitable duct work.

It will be appreciated that with the design of heat exchanger illustrated in Figures 1 to 3 the cores 2 to 5 may simply be removed fom the framework by unbolting the panel 1 7 and sliding the cores out from the framework 1. Once removed the cores may be cleaned or replaced. It will further be appreciated that the front panel 1 7 not only secures the cores in position but also prevents the build-up of stress in the cores, which may occur on expansion. When this happens the flexible panel 17 will bend to accommodate the expansion of the cores.

It will further be appreciated that the heat exchanger framework may include two cores, three cores or more than four cores. It will also be appreciated that if required a standard framework can be used with some of the apertures blanked off, and thus less than the maximum total of cores need be inserted into the framework. For example, in the framework shown in Figures 1 and 2 only two cores may be used, located at positions 2 and 3, with the apertures which would normally accommodate cores 4 and 5 simply being blanked off.

Claims (9)

1. A heat exchanger assembly including a framework and a pair of side panels arranged so as to define a first fluid flow path for a first fluid and a second fluid flow path for a second fluid, the two flow paths being arranged at an angle to one another, preferably a right angle, the framework including support means for at least two heat exchanger cores which can be slid into and removed from the framework, a restraining system for the cores comprising a flexible planar sheet which has a number of apertures not less than the number of cores, the sheet being secured to the framework and the periphery of an aperture restraining and locating the periphery of a core.

2. A heat exchanger as claimed in Claim 1 in which the number of apertures is equal to the number of cores.

3. A heat exchanger as claimed in Claim 1 or Claim 2 in which the periphery of each aperture is connected to the periphery of a core.

4. A heat exchanger as claimed in any one of Claims 1 to 3 in which the cores have a flange on each end to which the periphery of the aperture is connected.

5. A heat exchanger as claimed in Claim 4 in which the connection is by screws or bolts.

6. A heat exchanger as claimed in Claim 4 or Claim 5 in which there is a sealing layer between the flange and the periphery of the aperture.

7. A heat exchanger as claimed in any one of Claims 1 to 5 in which the cores are formed by a plate fin construction and each core includes a plurality of plates separated from one another by corrugated fins which are bonded to the plates.

8. A heat exchanger as claimed in any one of Claims 1 to 7 in which side strips are provided to define flow paths in the core.

9. A heat exchanger substantially as herein described with reference to and as illustrated by the accompanying drawings.