EXCHANGER

TECHNICAL FIELD

The present disclosure generally relates to heat exchangers. In particular, it relates to a heat exchanger made by additive manufacturing and to a method of manufacturing a heat exchanger using additive manufacturing.

BACKGROUND

As in most fields of technology, manufacturers of heat exchangers strive to find cost efficient and simple production methods. For example,

JP2004132589 discloses a heat exchanger which comprises corrugated sheets. The corrugations form flow channels of the heat exchanger. Every second channel of a sheet is an open channel and the remaining channels are closed channels. The closed channels are obtained by adhering lids to originally open channels of the sheet. Two such sheets are then stacked and laminated to form a plurality of closed channels.

A disadvantage with the heat exchanger disclosed in JP2004132589 is that the lamination of the sheets requires additional process steps. In addition to the lamination step, a process step of surface activation of the sheets to enable lamination may also be necessary. Moreover, adhesives are expensive and may be hazardous to the environment. Furthermore, the lamination step also complicates changes in the production line. Different applications may require different sheet material which in turn may need to be laminated with different types of adhesives. Thus, if the sheet material is changed, considerations concerning a suitable adhesive and surface activator for that material will also need to be taken into account.

SUMMARY

There have been previous attempts of manufacturing heat exchangers using additive manufacturing methods to simplify their production. For this purpose, fused deposition modelling (FDM), or equivalently, fused filament fabrication (FFF), has for example been used. These known attempts of manufacturing heat exchangers by means of additive manufacturing have not resulted in feasible products, both because the time of manufacturing each heat exchanger, which is substantial for each unit produced, and also because the heat exchangers have been far from fluid tight. This gives rise to high losses and low efficiency.

In view of the above, an objective of the present disclosure is to provide a heat exchanger which solves or at least mitigates the problems of the prior art. Another objective is to provide a method of manufacturing a heat exchanger.

There is hence according to a first aspect of the present disclosure provided a heat exchanger comprising: a channel layer comprising a circumferentially closed channel, wherein the channel layer is monolithic and has been made by means of digital light processing 3D-printing, and wherein the channel layer is made from a resin.

By means of digital light processing (DLP) 3D-printing using a resin, which is in fluid form during the manufacturing process, and which is cured using for example ultraviolet (UV) light, there will not arise any voids or air pockets during the manufacturing process. This ensures that the efficiency of the heat exchanger will be optimal and without leakage. This effect may be obtained because of the inherent differences in using DLP 3D-printing compared to e.g. FDM. The former typically uses a resin bath where for each layer of building an object, the top layer of the liquid resin is cured using for example UV light. For each curing step, this top layer is moved downwards into the liquid resin to thereby form a new top layer to be cured. This ensures that there will be no air gaps formed between the layers.

A continuous process is also possible where there may be no pause between layers and the light is never turned off during the manufacturing process. A heat exchanger made by means of DLP 3D-printing will have a recognisable structure in that it will be completely without voids. This is a unique feature provided by DLP 3D-printing. Furthermore, the solidified resin will typically contain traces of a curing agent. DLP 3D-printing is also called continuous liquid interface production (CLIP). DLP 3D-printing thus differs from for example FDM where molten polymer is ejected by a nozzle tracing layer upon layer, which result in air bubbles between the layers that form an object, for example a heat exchanger. An FDM-made heat exchanger will therefore not be inherently fluid tight. Additionally, the speed of manufacturing can be greatly increased by additive manufacturing using a resin, which makes it commercially viable to mass- produce a heat exchanger using DLP 3D-printing.

According to one embodiment the channel layer comprises a plurality of circumferentially closed channels. One embodiment comprises a plurality of channel layers, each comprising a plurality of circumferentially closed channels, each being made by means of DLP 3D-printing and each being made from a resin, the channel layers being arranged in a multi-layer configuration by means of DLP 3D-printing, thereby forming a single monolithic structure. According to one embodiment the channel layer comprises a fluid inlet and a fluid outlet, the fluid inlet and fluid outlet having been made by means of DLP 3D-printing.

According to one embodiment the channel layer comprises a channel dividing sheet which divides the circumferentially closed channel and which is made of a membrane or porous material.

There is according to a second aspect of the present disclosure provided a method of manufacturing a heat exchanger, wherein the method comprises: creating a channel layer comprising a circumferentially closed channel by means of digital light processing 3D-printing , using a resin to form the channel layer, wherein the channel layer is monolithic.

According to one embodiment the channel layer comprises a plurality of circumferentially closed channels. One embodiment comprises creating a plurality of channel layers by means of digital light processing 3D-printing, using a resin to form the channel layers, each comprising a plurality of circumferentially closed channels, the channel layers being arranged in a multi-layer configuration using digital light processing 3D-printing, thereby forming a single monolithic structure. One embodiment comprises creating a fluid inlet and a fluid outlet for the channel layer, wherein the fluid inlet and the fluid outlet is created using additive manufacturing.

One embodiment comprises arranging a channel dividing sheet to separate the circumferentially closed channel before the circumferentially closed channel has been fully built up, the channel dividing sheet being made of a membrane material.

There is according to a third aspect of the present disclosure provided a heat exchanger obtainable by means of the manufacturing method according to the second aspect presented herein. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, etc., unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. l shows an example of a heat exchanger comprising a single channel layer;

Fig. 2 shows an example of heat exchanger comprising a plurality of channel layers forming a single monolithic structure; Figs 3 and 4 show cross-sectional views of different potential configurations of the heat exchanger in Fig. 2;

Fig. 5 shows a perspective view of another example of a heat exchanger; and Fig. 6 shows a flowchart of a method of manufacturing a heat exchanger.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying

embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

The present disclosure relates to a heat exchanger and to a method of producing a heat exchanger. The heat exchanger is a monolithic structure made by additive manufacturing and comprises a resin. In particular, any portion of the heat exchanger that is made by additive manufacturing is made from a resin.

The heat exchanger comprises a channel layer comprising at least one circumferentially closed channel. The channel layer is monolithic. In case the channel layer comprises a plurality of circumferentially closed channels, these channels may for example be arranged in a row, or in any other suitable configuration made possible due to the additive manufacturing technology used to manufacture the heat exchanger. The channel layer is made using additive manufacturing and it is made from a resin.

It should be noted that the heat exchanger presented herein may have a vast number of different shapes and configuration, of which only a few examples are provided herein.

Fig. l shows a perspective view of one example of a monolithic heat exchanger. The exemplified heat exchanger l-i comprises a channel layer 3 including a circumferentially closed channel 5. The channel layer 3 is monolithic. The exemplified circumferentially closed channel 5 has a top surface and a bottom surface which are undulating in the direction of the x- axis, i.e. in a direction from a first lateral end 7a of the channel layer 3 to a second lateral end 7b thereof. This undulating structure can better be seen in Figs 3 and 4, which shows a plurality of channel layers 3 arranged in a multilayer configuration, forming a single monolithic structure. The channel layer 3 has a first end 9 a which defines an opening of the circumferentially closed channel 5, and a second end 9b which defines an opening at the other end of the circumferentially closed channel 5. Fluid flow can thus be provided through the channel layer 3, between the first end 9a and the second end 9b. The channel layer 3 may also comprise lateral elongated openings 11 arranged on opposite lateral sides of the channel layer 3, and extending parallel with the z-axis. These openings 11 are configured to allow cross-current flow with respect to the circumferentially closed channel 5 when a plurality of channel layers 3 are arranged in a multi-layer configuration to form a multi-layer monolithic heat exchanger, as shown in Fig. 2. This configuration is also shown in Fig. 3, which is a cross-section of the heat exchanger 1-2 in Fig. 2.

The channel layer 3 may according to one example be seen as a building block for a larger heat exchanger, for example the heat exchanger 1-2 shown in Fig. 2. The heat exchanger 1-2 comprises a plurality of channel layers 3, each comprising one circumferentially closed channel, arranged in a multi-layer configuration or fashion. The channel layers 3 are all formed or made by additive manufacturing in particular DLP 3D-printing, and comprise a resin and they form a single monolithic structure in their multi -layer configuration.

The heat exchanger 1-2 shown in Fig. 2 comprises a plurality of lateral elongated openings 11 defining the mouths of cross-extending or transverse channels with respect to the longitudinal extension of the circumferentially closed channels 5 extending along the z-axis. The cross-extending channels instead have an extension from their oppositely arranged openings along the x-axis. Each of these cross-extending channels is arranged between two circumferentially closed channels 5 of two adjacent channel layers 3. In this manner, cross-current flow may be provided, with one flow direction through the circumferentially closed channels 5 and another flow direction at 90 degrees angle through the cross-extending channels.

Figs 3 and 4 show two examples of potential cross-sectional configurations of the heat exchanger 1-2. In Fig. 3 it can here be seen that each channel layer 3 comprises a single circumferentially closed channel 5, and that in the multilayer configuration, the cross-extending channels 13a and 13b between adjacent channel layers 3 are circumferentially closed cross-extending channels. Due to the additive manufacturing, all of the channel layers 3, in their multi -layer configuration, form a single monolithic structure, with the outer walls 15 of the heat exchanger 1-2 forming a monolithic and thus seamless boundary thereof.

Fig. 4 shows an example in which the channel layers 3 comprise inner walls 17, or partitioning walls, partitioning the main sinusoidal channel shape in cross-section into a plurality of circumferentially closed channels 5a-5e. The inner walls 17 extend in the z-axis direction, i.e. from the first end 9a to the second end 9b.

Fig. 5 shows another example of a monolithic heat exchanger 1-3. According to this example, the heat exchanger 1-3 again comprises a plurality of channel layers 3 arranged in a multi-layer configuration. Each channel layer 3 comprises a circumferentially closed channel 5. Moreover, between each adjacent circumferentially closed channel 5, there is provided a cross- extending channel 19, which has an inlet and an outlet at an angle relative to the inlets and outlets of the circumferentially closed channels 5. This angle may for example be 90 degrees, but other configurations are also possible, as would be apparent to the person skilled in the art.

Any heat exchanger presented herein may comprise a fluid inlet and a fluid outlet. In particular, according to one example each channel layer 3 may be provided with a fluid inlet and a fluid outlet to direct fluid into the

circumferentially closed channel(s) and out from the circumferentially closed channel(s). The fluid inlets and the fluid outlets may also form part of the monolithic heat exchanger, and the entire monolithic structure may be made by additive manufacturing, in particular DLP 3D-printing. The fluid inlets and fluid outlets may in particular be made from a resin.

According to one variation one or more of the channel layers may comprise a channel dividing sheet which divides the circumferentially closed channel. An example of suitable material for a channel dividing sheet may be a membrane material, for example Gore-Tex® or a cellulose-based material. The channel dividing sheet may be made of impermeable, permeable, or semi-permeable material. The channel dividing sheet may according to one example for example be made of metal, for example stainless steel, aluminium, copper or any other metal suitable for heat transfer, plastic such as PE, PP, PET, PS, PPS, Polycarbonate, nylon, semi-permeable membranes, for example PEMs like Nafion, or any other suitable material for heat exchange or mass transfer applications, for example carbon foam and porous sheets. It is also envisaged that the channel dividing sheet may comprise a mixture of different materials

Fig. 6 is a flowchart of a method of manufacturing any of the heat exchangers 1-1, 1-2 and 1-3 described herein, and in more general a monolithic heat exchanger, by means of additive manufacturing, in particular DLP 3D- printing. In a step Si a channel layer 3 comprising a circumferentially closed channel 5 is created by means of DLP 3D-printing using a resin to form the channel layer 3, which is monolithic.

According to one variation a plurality of channel layers may be created by means of DLP 3D-printing, using a resin to form the channel layers. Each channel layer may comprise a plurality of circumferentially closed channels. The channel layers are in this case arranged in a multi-layer configuration using DLP 3D-printing, thereby forming a single monolithic structure.

According to one variation, the method may comprise creating a fluid inlet and a fluid outlet for each channel layer, using DLP 3D-printing.

According to one variation the method may comprise arranging a channel dividing sheet to separate the circumferentially closed channel before the circumferentially closed channel has been fully built up. The channel dividing sheet may thus in production of the heat exchange be placed on top the thus far built up monolithic structure, e.g. a channel layer. The manufacturing procedure may thereafter continue, and the channel dividing sheet is thus seamlessly integrated with the resin forming the channel layer 3. This procedure maybe repeated for each channel layer in case a heat exchanger with a plurality of channel layers is being manufactured, forming a single monolithic structure.

The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.