The present invention relates to a heat exchanger according to the preamble of the independent claim.

Background of the invention

Heat exchangers are devices that mediate the exchange of heat between two moving media. The media are separated by one or more partitions that transfer heat to the colder medium. In conventional heat exchangers, a large surface area on the heat transfer walls is desired. However, this often leads to the heat exchangers becoming large. As the temperature of the heated medium increases, it expands and is forced to move faster and faster through its conduit, which impairs the heat transfer.

One object of the invention is therefore to provide a compact heat exchanger that gives a more effective heat transfer. This and other objects are attained by a heat exchanger according to the characterising portion of the independent claim.

Summary of the invention

The invention relates to a heat exchanger comprising a casing 4, 4a-b, 11-12 with an internal cavity, where a heat transfer element is situated. This consists of an inclined wall 1 with connected heat conduction fins 2a-b on a heat output side as well as a heat supply side. The inclined wall generates cavities on the heat output side and the heat supply side which grow in cross-sectional area in the flow direction and are advantageously adapted for an expanding gas. The large surface of the fins provides an efficient heat transfer.

Fluid is supplied to the heat output side through a nozzle 6 into the cavity 3b. Heat is supplied to the heat supply side through a burner nozzle 5 to the cavity 3 a. The output of fluid from the heat exchanger is emitted through the output opening 7.

In an advantageous embodiment of the invention, the inlet on the heat output side is arranged at the top of the cavity on the heat output side, and the inlet on the heat supply side is arranged at the bottom of the cavity on the heat supply side. This advantageously provides the cavities which grow in cross-sectional area and are adapted for an expanding gas.

Typically, the inlet on the heat output side is disposed above the inlet on the heat supply side to optimize the heat transfer through a countercurrent flow. Due to the thickness of the wall 1, an efficient and even distribution of heat is achieved as well as a heat accumulating effect, which gives an even heat transfer even at varying flows.

The heat exchanger can be used as a steam generator for producing water vapour to power e.g. a steam turbine and thus replace a steam boiler. By varying the supply with the nozzle 6 and the heat supply with the burner nozzle 5, it is easy to regulate the steam production for varying power requirements. With pressurized and preheated water supplied to the inlet, the heat exchanger should be able to produce superheated steam.

Brief description of the drawings

Fig. 1 shows a first embodiment of the heat exchanger heat transfer element without casing viewed at an angle from the side.

Fig. 2 shows in partial cross-section the first embodiment of the heat exchanger as seen from the side.

Fig. 3 shows a cross section along the line A- A through the first embodiment of the heat exchanger with casing seen from above.

Fig. 4 shows a first half of a casing for a second embodiment of the heat exchanger seen from above at an angle.

Fig. 5 shows the first half of the casing with a heat transfer element according to a second embodiment of the heat exchanger viewed from above at an angle, from that side the first half of the casing faces away from.

Fig. 6 shows a second half of a casing for the second embodiment of the heat exchanger viewed at an angle from above.

Fig. 7 shows the second embodiment of the heat exchanger as seen straight from the side

Fig. 8 shows a cross section through the second embodiment of the heat transfer element as seen from the side.

Fig. 9 shows the second embodiment of the heat transfer element viewed at an angle from above, from the side the first half of the casing faces against.

Fig. 10 shows the second embodiment of the heat transfer element seen at an angle from below Description of preferred embodiments

The invention relates to a heat exchanger which is normally provided with a casing and is typically connected to surrounding components. The heat exchanger itself extends in a cylindrical cavity with a centre axis or in a cuboid cavity, the cavity being surrounded by a casing defining the cavity. In order to facilitate the understanding of the figures, only heat exchanger elements 1, 2a-b of the heat exchanger are shown in figure 1. The cylindrical cavity is typically arranged with the centre axis extending vertically and the cuboid shaped cavity correspondingly, so the heat exchanger is also illustrated in the figures in this way.

Fig. 1 shows a first embodiment of the heat exchanger heat transfer element 1, 2a-b viewed at an angle from the side. The casing of the cylindrical cavity is here removed, so the periphery of the cavity is not illustrated, but this is largely the periphery of the heat transfer element. The heat transfer element has an inclined wall 1 which defines a right heat supply side as well as a left heat output side in the cavity.

With the exception of the cavities 3a-b, vertical disc-shaped fins 2a-b are connected to the wall. The fins are flat, parallel, and spaced evenly apart on both sides of the inclined wall 1. Between the fins, disc-shaped vertical openings extend through which fluids can flow downward and upward, respectively. The fins are connected to the inclined wall 1, so that heat flowing through the inclined wall is effectively conveyed to the fins.

The fins are cut off so that cavities 3a-b are formed adjacent to the lower right side of the inclined wall and adjacent to the upper left side of the inclined wall. The left cavity 3b is located above the right cavity 3a. The left cavity 3b constitutes the inlet port on the heat output side, i.e. on the side where the supplied fluid removes heat from the heat exchanger. The right cavity 3a constitutes inlet port on the heat supply side, that is, on the side where the supplied fluid supplies heat to the heat exchanger.

Fig. 2 shows in partial cross-section the first embodiment of the heat exchanger 1, 2a-b with casing 4 and with connected surrounding components 5-6 viewed from the side. The figure clearly illustrates the function of the heat exchanger in a practical case. The casing 4 surrounds the cylindrical heat exchanger heat transfer element 1, 2a-b around its periphery, leaving an opening upward but downwardly forming a closed container with a

hemispherical end cap, and an output 7. Openings extend into the cavities 3a-b through the wall of the casing. To the cavity 3a on the heat supply side extends an opening in which a burner nozzle 5 is arranged. The burner nozzle 5 emits hot burning gas which first flows to die inclined wall 1 and then up between the fins 2a on the heat supply side. The combustion gases supply heat to the inclined wall 1 and the fins 2a so that it cools as it travels upward in the heat exchanger. When it reaches the top of the heat exchanger, it can freely leave it through the upwardly directed opening.

To the cavity 3b on the heat output side extends an opening in which a fluid nozzle 6 is provided. The fluid nozzle 6 can release cold or hot fluid as a fog or in gaseous form. The fluid first flows toward the hot inclined wall 1 and is then forced downwards between the fins 2b on the heat output side. The inclined wall 1 is connected to the inside of the casing 4 and delimits the cavity so that the fluid cannot flow anywhere but down. The inclined wall 1 and the fins 2b supply heat to the fluid so that it becomes hotter as it travels downward in the heat exchanger. When the fluid exits the bottom of the heat transfer element, it is enclosed by the lower closed hemispherical surface of the casing 4 and can only leave the heat exchanger through the output 7.

As the fluid flows downward in the heat exchanger on the heat output side, it transits to gaseous form if it was originally in liquid form and then expands further due to the increase in temperature. Since the heat exchanger on the heat output side downwards has an increasing cross-sectional area, this matches the expansion of the gas well and enhances the efficiency of the heat exchanger.

Fig. 3 shows a cross section along the line A-A through the first embodiment of the heat exchanger as seen from above. The figure illustrates in cross-section the cylindrical casing 4 as a circular ring. The inclined wall 1 extends from one side of the casing 4 interior to the opposite side. The disc shaped fins 2a-b extends orthogonally from the inclined wall and each fin extends to the inside of the casing 4. On the heat supply side as well as on the heat output side, the casing, the inclined wall and the fins define a set of disc-shaped cavities that a fluid can fill and then move upwards respectively downwards, thus in the figure towards or from the viewer.

Fig. 4 shows a first half 4a of a casing for a second embodiment of the heat exchanger viewed at an angle from above. The first half of the casing can be described as a cuboid shaped member cut off at an angle so that in cross-section it forms a right-angled triangle. The surface cut off at an angle is surrounded by a flange 13 and there is also a sealing lip that protrudes from the flange. The first half of the casing is hollow and can into its interior receive a heat transfer element. The first half of the casing is on its lower surface provided with a cylindrical open pipe section, whose downward facing opening forms an output outlet opening 7 for steam on the heat output side. The first half of the casing is also provided with an inlet opening 8 in its upper part to which a fluid is supplied.

Fig. 5 shows the first half of the casing with a heat transfer element according to a second embodiment of the heat exchanger viewed at an angle from above, from that side the first half of the casing faces away from. The heat transfer element comprises a set of fins 2a extending to an inclined wall 1 of the heat transfer element. The inclined wall 1 of the heat transfer element abuts the sealing lip on flange 13 on the first half of the casing. The heat transfer element also exposes an opening to a cavity 3a on the heat supply side of the heat transfer element.

Fig. 6 shows a second half 4b of a casing of the second embodiment of the heat exchanger as seen at an angle from above. The second half of the casing can be described as a cuboid shaped member cut off at an angle so that it in cross-section forms a right angled triangle. The surface cut off at an angle is surrounded by a flange 14 and there is also a sealing lip that protrudes from the flange. Also, the second half of the casing is hollow and can receive the heat transfer element into its interior.

The second half of the casing is provided with an opening 10 facing upwards, through which combustion gases freely can leave the heat exchanger. The second half of the casing is also provided at its bottom with an opening 9 arranged over the opening to the cavity 3a on the heat supply side of the heat transfer element. Through this, gas for combustion is supplied.

Fig. 7 shows the second embodiment of the heat exchanger as seen from the side. Here, the two halves 4a-b of the casing of the second embodiment of the heat exchanger have been joined together, with the inclined wall 1 of the heat transfer element between the flanges 13-14 on the two halves. The two halves 4a-b joined together this way, with the exception of the openings 7, 8, 9, 10 in the casing, form a closed space with the heat transfer element inside. The two halves 4a-b of the casing of the second embodiment are mounted together with screws not illustrated in the figure. The two halves grasp the flange on the heat transfer element and form a tight joint.

Fig. 8 shows a cross section through the second embodiment of the heat transfer element 1, 2a-b of the heat exchanger viewed at an angle from the side. The casing of the cuboid cavity is here removed. The heat transfer element has an inclined wall 1 which defines a right heat supply side as well as a left heat output side in the cavity. Vertically extending disc-shaped fins 2a-b are attached to the wall 1. The fins are flat, parallel, and spaced evenly apart on both sides of the inclined wall 1. Between the fins, disc-shaped vertical openings extends, through which fluids can flow downwards and upwards, respectively. The fins are connected to the inclined wall 1, so that heat flowing through the inclined wall is effectively conveyed to the fins.

The fins are cut off so that cavities 3a-b are formed adjacent to the lower right side of the inclined wall and adjacent to the upper left side of the inclined wall. The left cavity 3b is located above the right cavity 3a. The left cavity 3b is the inlet port on the heat output side, i.e. on the side where the supplied fluid removes heat from the heat exchanger. The right cavity 3 a constitutes an inlet port on the heat supply side, that is, on the side where the burning gases supplies heat to the heat exchanger.

Fig. 9 shows the second embodiment of the heat transfer element viewed at an angle from above, from the side the first half of the casing would have faced. The first half of the casing is not illustrated in the figure. The half of the heat transfer element facing the viewer is surrounded by interior walls 11 which form part of the heat transfer element. Thus, on this side of the inclined wall 1, the heat exchanger is partially double-walled, with an outer wall constituted by the first half 4a of the casing, and with an inner wall constituted by the inner walls 11 of the heat transfer element.

Fig. 10 shows the second embodiment of the heat transfer element seen at an angle from below from the side the first half of the casing had faced away from. The casing is not illustrated in the figure. The half of the heat transfer element facing the viewer is surrounded by internal walls 12 which form part of the heat transfer element. The heat exchanger is thus on this side of the inclined wall 1 partially double-walled, with an outer wall made up of the second half 4b of the casing, and with an inner wall made up of the inner walls 12 of the heat transfer element.

Description of alternative embodiments

In the disclosed embodiments, the heat exchanger extends in a cylindrical or cuboid cavity surrounded by a cylindrical or cuboid casing. Obviously, the cavity may be differently shaped and, for example, have a polygon-shaped cross-section.

The heat exchanger heat transfer element with inclined wall and fins is preferably manufactured as a solid piece of a heat conducting material, typically copper, but of course it can be made in other ways and of other materials.

In the described embodiments, the inlet on the heat output side is located above the inlet on the heat supply side, this makes the heat transfer in the heat exchanger more effective. In principle, this does not have to be so and the specific distances chosen between the inlets is of course not limiting.

The disc-shaped fins 2a-b and the inclined wall 1 are illustrated as flat, even thickness elements, but obviously they can have curved surfaces or have a thickness varying over their surface. The disc-shaped fins 2a-b are also spaced evenly apart, but this is not necessary either. There may be reason to design the disc-shaped fins and the inclined wall differently or to position the disc-shaped fins 2a-b other than at an even distance from each other, to optimize the fluid flow through the heat exchanger. However, it is typically easier to manufacture a heat exchanger designed in the way it is illustrated in the figures.

In the described embodiments, the fins are terminated at the top and bottom edges of the heat transfer element where the inclined wall 1 connects to the casing 4. In another embodiment, the fins can be extended upwards and downwards respectively and continue past this position to increase the heat transfer surface.

In the described embodiments, the heat is supplied with a burner nozzle. However, the heat can be supplied by any other method e.g. a hot gas.

In the described embodiments, the fluid is supplied though a nozzle. However, the fluid may be supplied by any other method.

In the second embodiment, the heat exchanger is partially double-walled, with an outer wall made up of the casing 4a-b, and with an inner wall made up of the inner walls 11 -12 of the heat transfer element. Obviously, the heat exchanger may be single-walled or have a more complex wall structure, with heat-insulating layers to seal in the heat.