AND ITS MANUFACTURING METHOD

DESCRIPTION

Technical Field

The present invention relates to a heat exchanger, e.g. a thermal radiator, and more particularly to a method of manufacturing a heat exchanger.

Technical Background

Compact thermal radiators with metal fins are commonly used to heat boats, motorhomes, caravans and other vehicles such as public transport. Each metal fin has a central aperture therethrough which enables each metal fin to be pushed onto a metal pipe. The metal fins are either separate components or are joined together with folds which ensure registration of the respective central apertures. However, achieving regular spacing of the metal fins on the metal pipe may be time-consuming, and the metal fins are easily bent out of shape, hindering efficient heat transfer to ambient surroundings. The present invention seeks to address such limitations.

Summary of the Invention

In accordance with a first aspect of the present invention, there is provided a method of manufacturing a heat exchanger, e.g. a thermal radiator, comprising:

providing an expandable body comprising a plurality of flexible sheets stacked in a first direction, with adjacent pairs of flexible sheets joined together by a plurality of spaced-apart, elongate joins which extend in a second direction perpendicular to the first direction, and with elongate joins between each pair of flexible sheets staggered relative to respective elongate joins with contiguous flexible sheets such that open cells form between flexible sheets when the expandable body is expanded in the first direction;

inserting a pipe through an aperture extending through the expandable body in the first direction, the aperture being configured such that opposing surfaces of the aperture in a plane perpendicular to the second direction are spaced from the metal pipe; and

expanding the expandable body in the first direction along the pipe so that said opposing surfaces of the aperture engage the pipe. The present applicant has appreciated that expanding the expandable body in the first direction along the pipe, leads to a contraction of the expandable body in a third direction perpendicular to both the first and second directions due to flexure of the flexible sheets. Such a contraction effectively pulls said opposing surfaces of the aperture together, until they engage the pipe. Such engagement ensures good thermal transfer between the pipe and the flexible sheets. In this way, thermal energy (e.g. from heated fluid flowing through a bore in the pipe or an electrical resistance heating element housed in the pipe) may readily be transferred from the pipe to the flexible sheets in a heating configuration. Equally, thermal energy (e.g. from a refrigerant flowing through the bore of the pipe) may readily be transferred from the flexible sheets to the pipe in a cooling configuration.

The flexible sheets and the elongate joins therebetween may be configured to form a honeycomb-like structure when the expandable body is expanded in the first direction. In such a honeycomb-like structure, the open cells may be substantially polygonal, and may even be approximately hexagonal. However, the open cells do not need to have a precise geometrical shape.

The method may further comprise forming the aperture in the expandable body when the expandable body is in a non-expanded configuration, for example by punching or drilling. Forming the aperture in the expandable body may comprise forming a substantially elliptical aperture in the expandable body when the expandable body is in the non-expanded configuration. The substantially elliptical aperture may have a major axis and a minor axis perpendicular thereto, with the dimension of the substantially elliptical aperture along the major axis being greater than that along the minor axis. The substantially elliptical aperture may be formed in the expandable body with the major axis of the substantially elliptical aperture substantially perpendicular to the second direction.

The pipe may have a circular cross-section.

The pipe may be a relatively loose fit in the substantially elliptical aperture when the expandable body is in a non-expanded configuration. For example, the dimension of the substantially elliptical aperture along the minor axis may be up to about 2% greater than the diameter of the pipe, for example about 1% greater, and the dimension of the substantially elliptical aperture along the major axis may be up to about 10% greater than the diameter of the pipe, for example about 5% greater.

The method may further comprise maintaining engagement between said opposing surfaces of the aperture and the pipe by resisting compression of the expandable body once expanded in the first direction. For example, maintaining engagement may comprise bonding at least one panel to at least one face of the expandable body once the expandable body has been expanded in the first direction. Alternatively or additionally, maintaining engagement may comprise coupling one or more flexible sheets of the expandable body to the pipe once the expandable body has been expanded in the first direction. Such coupling may comprise applying an adhesive or providing at least one protuberance on the pipe.

The pipe may be formed of a metal, e.g. copper or aluminium. The flexible sheets may be self- supporting and may be resilient, and may also be formed of a metal, e.g. aluminium. The pipe and the flexible sheets may be formed of the same or similar metals, e.g. aluminium.

In accordance with a second aspect of the present invention, there is provided a heat exchanger, e.g. a thermal radiator, comprising:

a body having a honeycomb-like structure with open cells formed between a plurality of flexible sheets stacked in a first direction, with adjacent pairs of flexible sheets joined together by a plurality of spaced-apart, elongate joins which extend in a second direction perpendicular to the first direction, and with elongate joins between each pair of flexible sheets staggered relative to respective elongate joins with contiguous sheets; and

a pipe inserted in an aperture extending through the body in the first direction, with opposing surfaces of the aperture in a plane perpendicular to the second direction engaging the pipe.

The open cells of the honeycomb-like structure may be substantially polygonal, and may even be approximately hexagonal. However, the open cells do not need to have a precise geometrical shape.

The pipe may have a circular cross-section. The heat exchanger may further comprise at least one member configured to maintain engagement between said opposing surfaces of the aperture and the pipe by resisting compression of the body in the first direction. For example, the at least one member may comprise a panel bonded to at least one face of the expandable member to maintain open cell formation. Alternatively or additionally, the at least one member may comprise a coupling between the pipe and one or more flexible sheets of the expandable body.

The flexible sheets of the expandable body may comprise a metal, and may be formed of aluminium. For example, the metal flexible sheets may have a thickness of between 35 pm and70pm. The metal flexible sheets may be joined together with an adhesive, such as an epoxy adhesive. The pipe may comprise a metal, and the metal may be aluminium.

The metal pipe may typically have an outer diameter which is in the range 10mm to 30mm, such as 15mm or even 22mm. The invention has applications beyond use as a radiator fitted to a wall or bulkhead. Metal pipes (wet or dry systems) may be incorporated into an expandable body which will form an aluminium honeycomb panel when expanded. These panels have an application anywhere efficient transfer of heat is needed as they will distribute heat evenly, so for example a bulkhead in a boat, caravan or other recreational vehicle may be heated easily and very efficiently. The principal of heated panels using the invention can also be reversed. If a refrigerant is pumped through the honeycomb radiator panel it would be an alternative to the pipes on the back of refrigerators for example. Brief Description of the Drawings

An embodiment of the invention will now be described by way of example and with reference to the accompanying figures:

Figure 1 is a schematic illustration of a first step in manufacturing a heat exchanger, e.g. a thermal radiator, according to one embodiment of the present invention;

Figure 2 is a schematic illustration of a second step in manufacturing the heat exchanger according to one embodiment of the present invention;

Figure 3 is a schematic illustration of a third step in manufacturing the heat exchanger according to one embodiment of the present invention; and

Figure 4 is a schematic illustration of a fourth step in manufacturing the heat exchanger according to one embodiment of the present invention. Description of Specific Embodiment

Figures 1-4 illustrate schematically stages in manufacture of a heat exchanger, e.g. a thermal radiator, in accordance with an embodiment of the present invention. Figure 1 shows schematically an expandable body 10 in a non-expanded configuration, comprising a plurality of flexible metal sheets 12 stacked in a first direction 14. Adjacent pairs of metal sheets 12 are joined together by a plurality of spaced-apart, elongate joins 16 which extend in a second direction 18 perpendicular to the first direction 14. Furthermore, elongate joins 16 between each pair of metal sheets 12 are staggered or off-set relative to respective elongate joins 16 with contiguous metal sheets 12. In this way, open cells form between metal sheets 12 when the expandable body 10 is expanded in the first direction 14, as shown in more detail in Figure 4.

Figure 2 shows schematically the expandable body 10 in the non-expanded configuration, with an elliptical aperture 20 formed therethrough and extending in the first direction 14. The elliptical aperture has a major axis 22 and a minor axis 24, with the dimension of the elliptical aperture 20 along the major axis 22 being greater than that along the minor axis 24. The major axis 22 is aligned substantially perpendicular to the first direction 14 and the second direction 18.

Figure 3 shows schematically the expandable body 10 in the non-expanded configuration, with a metal pipe 30 inserted through the elliptical aperture 20. The metal pipe 30 has a circular cross-section, with an outer diameter“D” being slightly less than the dimension of the elliptical aperture 20 along the minor axis 24. At either end of the major axis 22, opposing surfaces 32 of the aperture 20 in a plane perpendicular to the second direction 18 are spaced from the metal pipe 30. In this way, the metal pipe 30 is a loose fit in the elliptical aperture 20, whilst the expandable body is in the non-expanded configuration. The outer diameter “D” of the metal pipe 30 is a similar size to the spacing“S” between adjacent elongate joins 16 between a pair of pair of metal sheets 12.

Figure 4 shows schematically the expandable body 10 expanded in the first direction 14 into an expanded configuration with a honeycomb-like structure 40 with open cells 42 formed between metal sheets 12 and elongate joins 16. Expanding the expandable body 10 in the first direction 14 causes the metal sheets 12 to bend as the open cells 42 form, leading to a contraction in a plane perpendicular to the first direction 14. This contraction causes the opposing surfaces 32 of the aperture 20 to move towards each other in the direction of arrows “A” and engage the metal pipe 30, and even grip the metal pipe 30 securely. Such engagement will ensure good thermal transfer between the metal pipe 30 and the metal sheets 12. Once fully expanded, the expandable body 10 may be maintained in the expanded configuration by bonding a metal panel (not shown) to exposed edges 44 of the metal sheets 12 on an upper, lower or side surface of the expandable body 10.