WO2017016647A1

WO2017016647A1 - Heat transfer tube, heat reservoir and method for producing a heat transfer tube

Info

Publication number: WO2017016647A1
Application number: PCT/EP2016/001220
Authority: WO
Inventors: Heinz Posselt; Manfred Schönberger; Stefan Hübner
Original assignee: Linde Aktiengesellschaft
Priority date: 2015-07-30
Filing date: 2016-06-14
Publication date: 2017-02-02

Abstract

A heat transfer tube (3), in particular a finned tube, for a heat reservoir (1), in particular a molten-salt PCM, said tube comprising: a pressure tube (5) for conveying a fluid (4); a heat transfer element (6) provided on the exterior of the pressure tube (5); a connecting layer (10), arranged between the pressure tube (5) and the heat transfer element (6), for connecting the heat transfer element (6) to the pressure tube (5), the connecting layer (10) being bonded to the heat transfer element (6); and a reinforcing element (11) provided on or in the connecting layer (10), said reinforcing element being designed to prevent heat-induced expansion of the connecting layer (10).

Description

description

Heat transfer tube, heat accumulator and method for producing a

Wärmeübertraqungsrohrs

The invention relates to a heat transfer tube, a heat accumulator with such a heat transfer tube and a method for producing such a heat transfer tube.

Heat storage, especially so-called latent heat storage, have a

Storage medium and a in the storage medium or passed through this heat transfer tube. Through the heat transfer tube, a fluid, such as heated water vapor, is passed. Such latent heat storage use the enthalpy of reversible thermodynamic state changes of

Storage medium, in particular the phase transition from solid to liquid and vice versa. When charging the latent heat storage, the storage medium is melted. During the melting process, the storage medium of the fluid absorbs a large heat energy in the form of the heat of fusion. Due to the

Reversibility of this process, the storage medium gives this heat energy during solidification back to the fluid. To a good heat transfer from the heat pipe to the

To ensure storage medium, the heat transfer tube may have in its longitudinal direction extending ribs. Since aluminum alloys have particularly good heat conduction properties and a filigree rib designs, for example by means of extrusion molding, is possible, with regard to a good

Heat transfer from the heat transfer tube to the storage medium and vice versa, an aluminum material is a suitable material for such

Heat transfer tubes. However, since aluminum alloys at higher

Temperatures have only a limited strength, it is necessary to provide the heat transfer tube with a pressure tube made of a steel alloy to absorb the pressure of the fluid.

WO 201 1/0696693 A1 describes a heat transfer tube with a pressure tube made of a steel alloy and a heat transfer element, the an aluminum alloy is made. Since aluminum alloys have a significantly higher coefficient of thermal expansion than steel alloys, a heat transfer obstructing gap may form when a heat input into the heat transfer tube between the pressure tube and the heat transfer element. To prevent the formation of a gap, the heat transfer element is by means of resilient clamps, the two half shells of the

Clamp the heat transfer element to the pressure tube, attached to the pressure tube. Upon heat input into the heat transfer tube, the clips hold the heat transfer element in contact with the pressure tube.

Against this background, the object of the present invention is to provide an improved heat transfer tube for a heat storage available. Accordingly, a heat transfer tube, in particular a fin tube, for a heat storage, in particular for a molten salt latent heat storage, proposed. The heat transfer tube comprises a pressure tube for conveying a fluid, an outside of the pressure tube provided

Heat transfer element, one between the pressure tube and the

Heat transfer element arranged connecting layer to connect the heat transfer element with the pressure tube, wherein the bonding layer is integrally connected to the heat transfer element and a provided on or in the connection layer reinforcing element, which is adapted to prevent a thermal expansion of the bonding layer.

Under that the reinforcing element is a thermal expansion of the

Prevents connecting layer, is to be understood in the present case that a heat-related expansion of the bonding layer is prevented or reduced so that no gap between the pressure tube and the connecting layer. Due to the cohesive connection of the connecting layer with the

Heat transfer element are the connecting layer and the

Heat transfer element integrally formed. That is more precisely

Reinforcing element adapted to prevent a heat-related formation of a gap between the connecting layer and the pressure tube. Characterized in that the connection layer for connecting the heat transfer element with the Pressure tube is provided, a flat contact of the connecting layer is always ensured with the pressure tube. That is, there is a gap-free contact the

Connecting layer with the pressure tube before. Characterized in that the connecting layer is integrally connected to the heat transfer element, the formation of a gap between the connecting layer and the heat transfer element is prevented. The connecting layer is connected to the heat transfer element in particular gap-free. In particular, the reinforcing element also prevents a thermal expansion of the heat transfer element. In the known arrangement only a linear contact is achieved. The fact that the reinforcing element prevents a heat-related expansion of the connecting layer, is to be understood in the present case that a heat-related expansion of the connecting layer is prevented or reduced so that no gap is formed between the pressure tube and the connecting layer. Here is the

Intermediate layer sandwiched between the reinforcing element and the pressure tube. A thermal expansion of the bonding layer is caused by the

Reinforcing element mechanically prevented. The reinforcing element absorbs circumferential stresses resulting from thermal expansion of the connecting layer. An operating temperature of the heat accumulator can be over 300 ° C. At the operating temperature of the heat accumulator a yield strength of the material of the heat transfer element and / or the connecting layer sö low, that they can not absorb force. The absorption of the compressive forces takes place exclusively with the help of the pressure tube. Bonded connections, such as soldered connections, are to be understood as meaning all connections in which the

Connection partners are held together by atomic or molecular forces. They are at the same time non-detachable connections, which can only be separated by destruction of the connecting means.

According to one embodiment, the reinforcing element is adapted to a flat contact of the heat transfer in the heat transfer tube

To ensure bonding layer with the pressure tube.

In particular, the connecting layer is circumferentially resting on the pressure tube. The support surface is preferably cylindrical. According to a further embodiment, a material from which the Heat transfer element and the connecting layer are made, a higher coefficient of thermal expansion than a material from which the pressure tube and the reinforcement are made. This ensures that the connecting layer can expand only as far as it allows the material of the reinforcing element.

According to a further embodiment, the heat transfer element and / or the connecting layer are each made of an aluminum alloy.

For example, the heat transfer element and / or the

Connecting layer of the same or different

Made of aluminum alloys. The aluminum alloys may, for example, have different thermal expansion coefficients.

According to a further embodiment, the pressure tube and / or the

Arming each made of a steel alloy.

For example, the pressure tube and / or the reinforcing element may be made of a stainless steel or a stainless steel alloy.

According to a further embodiment, the pressure tube and the

Arming element made of different steel alloys. For example, the different steel alloys can be different

Have thermal expansion coefficient. For example, the material of the reinforcing element may have a lower coefficient of thermal expansion than the material of the pressure tube. According to a further embodiment, the connecting layer is made of a solder, in particular of an aluminum solder.

The connecting layer can be wound on the pressure tube, for example in the form of a wire. According to a further embodiment, the reinforcing element comprises a perforated or slotted tube, a wire circulating in the pressure tube or a

Wire mesh. The reinforcing element can be pushed onto the connecting layer or wound up. Preferably, the reinforcing element is melted into the connecting layer.

According to a further embodiment, the heat transfer element has at least two shells, between which the pressure tube is arranged.

The shells may be formed, for example, as extruded sections. The mounting of the heat transfer element to the pressure tube is simplified by the use of multiple shells. As a result, the heat transfer tube can also be produced inexpensively. The heat transfer element may have any number of shells. For example, the heat transfer element may comprise two half shells, three third shells or four quarter shells.

According to a further embodiment, the heat transfer element is cylindrical and has radially extending ribs.

The ribs preferably extend in a longitudinal direction of the

Heat transfer tube. The ribs may have a variety of ramifications. This enlarges the surface of the

Heat transfer element, whereby an improved heat transfer is possible.

Furthermore, a heat storage, in particular a molten salt latent heat storage with at least one such heat transfer tube and a storage medium, in particular a molten salt, in which the at least one heat transfer tube is at least partially proposed.

The heat accumulator may comprise a plurality of heat transfer tubes, which are at least partially disposed in the storage medium. The storage medium may be salts or salt mixtures, in particular alkali metal hydrates, nitrates, nitrites, Sulfates, carbonates, chlorides, hydroxides, bromides, thiocyanates, fluorides and / or combinations of these. In particular, the storage medium comprises anhydrous salts or salt hydrates. Further, a method of manufacturing a heat transfer tube,

in particular a fin tube, proposed for a heat storage, in particular for a molten salt latent heat storage. The method comprises the following steps: providing a pressure tube and a

Heat transfer element; Attaching a bonding layer to the pressure tube; Attaching a reinforcing element to the connecting layer; Attaching the heat transfer element to the pressure tube, wherein the connecting layer and the reinforcing element between the pressure tube and the

Heat transfer element are arranged; Reflowing the bonding layer to connect the pressure tube to the heat transfer element; and cooling the heat transfer tube.

The melting of the connecting layer for connecting the pressure tube to the heat transfer element can be carried out, for example, in an oven, wherein the heat transfer tube is baked. In particular, the bonding layer is integrally bonded to the heat transfer element, so that no gap can form between the bonding layer and the heat transfer element.

According to one embodiment, a solder is applied to the pressure tube to form the bonding layer.

The solder can be wound up on the pressure tube. On the solder, the reinforcing element can continue to be wound in the form of a wire. In addition, a further solder layer can be wound onto the reinforcing element. According to a further embodiment, during the melting of the

Connecting layer, the reinforcing element in the connecting layer

melted down.

In particular, the bonding layer in the molten state can flow through the reinforcing element. Further possible implementations of the heat transfer tube, of the heat store and / or of the method also include not explicitly mentioned combinations of features or embodiments described above or below with regard to the exemplary embodiments. The skilled person will also add individual aspects as improvements or additions to the respective basic form of the heat transfer tube, the heat accumulator and / or the method.

Further advantageous embodiments and aspects of the heat transfer tube, the heat accumulator and / or the method are the subject of the dependent claims and the embodiments of the heat transfer tube, the heat accumulator and / or the method described below. In addition, the

Heat transfer tube, the heat storage and / or the method with reference to preferred embodiments with reference to the accompanying figures explained in more detail.

Fig. 1 shows a schematic sectional view of an embodiment of a

Heat storage; FIG. 2 shows a schematic perspective view of an embodiment of a heat transfer tube for the heat accumulator according to FIG. 1; FIG.

FIG. 3 shows a schematic block diagram of an embodiment of a

Method for producing a heat transfer tube according to FIG. 2;

Fig. 4 is a schematic sectional view of the heat transfer tube of Fig. 2; and

FIG. 5 shows a further schematic sectional view of the heat transfer tube according to FIG. 2.

In the figures, the same or functionally identical elements are the same

Unless otherwise indicated. Fig. 1 shows a highly simplified schematic sectional view of a

Embodiment of a heat accumulator 1. The heat accumulator 1 may be a

Diameter of about 50 meters and have a height of 30 meters. Of the

Heat storage 1 is a so-called latent heat storage. The heat storage 1 may be a molten salt latent heat storage. Such latent heat storage use the enthalpy reversible thermodynamic state changes of a process medium or storage medium 2 as a phase transition from solid to liquid and vice versa. Under enthalpy are the energy expenditure of

Phase transformations and the energy content of substances. At the

Charging the heat accumulator 1 is melted in this provided storage medium 2, which may be a phase change material. During the

Melting takes the storage medium 2 a large heat energy in the form of heat of fusion. Due to the reversibility of this process that gives

Storage medium 2 this heat energy when solidifying again.

The storage medium 2 may be a salt or a salt mixture. The

Storage medium 2 comprises alkali metal hydrates, nitrates, nitrites, sulfates, carbonates, chlorides, hydroxides, bromides, thiocyanates, fluorides or combinations of these, in particular anhydrous salts or salt hydrates. For example, that can

Storage medium 2 have a melting temperature of about 300 ° C. Consequently, the heat accumulator 1 can be operated with an operating temperature of over 300 ° C.

The heat storage 1 further comprises one or more heat transfer tube 3, which are designed as so-called fin tubes or can be referred to as fin tubes. The heat transfer tube 3 is at least partially in the

Storage medium 2 arranged and / or passed therethrough. Through the heat transfer tube 3, a fluid 4, such as water vapor can be passed. When melting the storage medium 2, the fluid 4 gives heat to the

Storage medium 2 from. When the storage medium 2 solidifies, this heat is transferred to the fluid 4.

Fig. 2 shows a schematic perspective view of an embodiment of such a heat transfer tube 3. The heat transfer tube 3 comprises a pressure tube 5 for conveying the fluid 4. The pressure tube 5 is made of a steel alloy manufactured. The pressure tube 5 may be made of a stainless steel. On the outside of the pressure tube 5 is a rib body, heat transfer body or

Heat transfer element 6 is provided. The heat transfer element 6 is cylindrical and may have a first circular cylindrical shell 7 and a second circular cylindrical shell 8, between which the pressure tube 5 is arranged. The heat transfer element 6 comprises a plurality of radially extending ribs 9, of which in Fig. 2 only two with a

Reference numerals are provided. The ribs 9 extend in a fin shape out of the half-shells 7, 8. Therefore, the heat transfer tube 3 is also referred to as a fin tube.

The number of ribs 9 is arbitrary. As shown in FIG. 2, that can

Heat transfer element 6 eight ribs 9 have. The ribs 9 extend in a longitudinal direction L of the heat transfer tube 3 and radially out of the

Half shells 7, 8 out. The ribs 9 can have a multiplicity of branches or ramifications, not shown in FIG. 2. This can be a

Surface of the heat transfer element 6 are increased, which the

Heat transfer from the heat transfer tube 3 to the storage medium 2 and vice versa improved. The heat transfer element 6 is made of a

Made of aluminum alloy. By using an aluminum alloy for the heat transfer element 6, this can be made particularly delicate and has due to the high specific thermal conductivity of aluminum compared to the steel alloy used for the pressure tube 5 good heat conduction properties.

At high temperatures, such as at temperatures above 300 ° C, the yield strength of aluminum alloys drops dramatically compared to steel alloys, so that a force transmitting structure with aluminum alloys at high temperatures is not possible. Therefore, only the pressure tube 5 is supplied with the fluid 4 and the heat transfer element 6 is not mechanically loaded with the internal pressure.

Between the pressure tube 5 and the heat transfer element 6 is a

Interlayer or tie layer 10 for bonding the

Heat transfer element 6 is provided with the pressure tube 5. The Bonding layer 10 is also made of an aluminum alloy. The bonding layer 10 may be made of an aluminum solder. The

Connecting layer 10 may be made of the same material as that

Heat transfer element 6. The material of the heat transfer element 6 and the connecting layer 10 has a higher coefficient of thermal expansion than the material of the pressure tube 5. The connecting layer 10 is materially connected to the heat transfer element 6. Bonded connections, such as soldered connections, are to be understood as meaning all connections in which the

On or in the connecting layer 10, a reinforcing element 11 is provided, which is adapted to prevent a thermal expansion of the connecting layer 10 and the heat transfer element 6. The reinforcing element 11 is provided on the outside of the connecting layer 10 and / or in this

melted down. The connecting layer 10 is sandwiched between the pressure tube 5 and the reinforcing element 1 1. The material from which the reinforcing element 1 1 is made, has a lower coefficient of thermal expansion than the material of the heat transfer element 6 and the connecting layer 10th

As a result, a heat-related expansion of the connecting layer 10 is prevented. In an operational heat input into the heat transfer tube 3, the connecting layer 10 by means of the pressure tube 5 and the

Reinforcing element 1 1 acted upon by radially acting pressure forces.

The reinforcing element 11 is made from a steel factory off. For example, the pressure tube 5 and the reinforcing element 11 may be made of the same steel alloy. Alternatively, the pressure tube 5 and the reinforcing element 11 may be made of different steel alloys. More precisely, that can

Pressure tube 5 and the reinforcing element 11 may be made of steel alloys having different thermal expansion coefficients. For example, the material of the reinforcing element 11 a smaller

As a result, it is always ensured that, when heat is introduced into the heat transfer tube 3, a circumferentially planar contact of the connecting layer 10 with the pressure tube 5 is achieved is guaranteed. The reinforcing element 11 may comprise a slotted or perforated tube, a wire surrounding the pressure tube 5 or a wire mesh.

With a heat input into the heat transfer tube 3, the

Connecting layer 10 due to their arrangement between the pressure tube 5 and the reinforcing element 1 1 does not extend so far that forms a gap between the pressure tube 5 and the connecting layer 10. This is always a good one

Heat transfer from the pressure tube 5 ensures the heat transfer element 6. Due to the cohesive connection of the connecting layer 10 with the heat transfer element 6 can also be between the

Heat transfer element 6 and the connecting layer 10 form no gap. The reinforcing element 11 receives at a heat input into the heat transfer tube 3 circumferential stresses resulting from a thermal expansion of the bonding layer 10.

Figs. 3 to 5 show an embodiment of a method of manufacturing such a heat transfer tube 3. In a step S1, the pressure tube 5 and the heat transfer member 6 are provided. The heat transfer element 6 may have the two half shells 7, 8, which may be formed as extruded profiles. In a step S2, the bonding layer 10 is attached to the pressure pipe 5. In this case, an aluminum solder can be wound onto the pressure tube 5.

In a step S3, the reinforcing element 11 is attached to the bonding layer 10. The reinforcing element 11 may be in the form of a tube over the

Connecting layer 10 are pushed. Alternatively, the reinforcing element 11 can be wound onto the bonding layer 10 in the form of a wire. In a step S4, the heat transfer element 6 with the two half shells 7, 8 is attached to the pressure tube 5, wherein the connecting layer 10 and the

Reinforcing element 11 between the pressure tube 5 and the

Heat transfer element 6 are arranged. FIG. 4 shows the pressure tube 5 after step S4.

In a step S5, the connecting layer 10 is melted to connect the pressure tube 5 with the heat transfer element 6. Here is the

Reinforcing element 11 fused into the connecting layer 10. This can be the Heat transfer tube 3 are baked in an oven. In a step S6, the heat transfer tube 3 is cooled. FIG. 5 shows the heat transfer tube 3 after the step S6. Before the melting of the connecting layer 10, as shown in FIG. 4, the half-shells 7, 8 are arranged slightly spaced from each other. Between the half-shells 7, 8, a gap 12 may be provided. After the melting of the connecting layer 10, the reinforcing element 1 1 is melted into the connecting layer 10 and the heat transfer element 6 is materially connected to the connecting layer 10. When the bonding layer 10 melts, the gap 12 closes.

Although the present invention has been described with reference to embodiments, it is variously modifiable.

For example, instead of two half shells 7, 8, the heat transfer element 6 may comprise three third shells or four quarter shells. The number of bowls is arbitrary.

Used reference signs

1 heat storage

2 storage medium

3 heat transfer tube

4 fluid

5 pressure tube

6 heat transfer element

7 half shell

8 half shell

9 rib

10 connection layer

11 reinforcing element

12 gap

L longitudinal direction

51 step

52 step

53 step

S4 step

55 step

56 step

Claims

claims

1. heat transfer tube (3), in particular fin tube, for a heat storage (1), in particular for a molten salt latent heat storage, with a

A pressure tube (5) for conveying a fluid (4), a heat transfer element (6) provided on the outside of the pressure tube (5), a connecting layer (10) arranged between the pressure tube (5) and the heat transfer element (6) for connecting the heat transfer element (6) ) With the pressure tube (5), wherein the connecting layer (10) cohesively with the

Heat transfer element (6) is connected to and on or in the

Connecting layer (10) provided reinforcing element (11) which is adapted to prevent a thermal expansion of the connecting layer (10).

2. Heat transfer tube according to claim 1, wherein the reinforcing element (1 1) is adapted to ensure a surface contact of the connecting layer (10) with the pressure tube (5) at a heat input into the heat transfer tube (3).

3. Heat transfer tube according to claim 1 or 2, wherein a material from which the heat transfer element (6) and the connecting layer (10) are made, has a higher coefficient of thermal expansion than a material from which the pressure tube (5) and the reinforcing element (11). are made.

4. Heat transfer tube according to one of claims 1 - 3, wherein the

Heat transfer element (6) and / or the connecting layer (10) are each made of an aluminum alloy.

5. Heat transfer tube according to one of claims 1 - 4, wherein the pressure tube (5) and / or the reinforcing element (1 1) are each made of a steel alloy.

6. Heat transfer tube according to claim 5, wherein the pressure tube (5) and the

Reinforcing element (11) are made of different steel alloys.

7. Heat transfer tube according to one of claims 1-6, wherein the connecting layer (10) is made of a solder, in particular of an aluminum solder.

8. Heat transfer tube according to one of claims 1-7, wherein the

Armierungselement (1 1) a perforated or slotted tube, a pressure tube surrounding the wire or a wire mesh comprises.

9. Heat transfer tube according to one of claims 1-8, wherein the

Heat transfer element (6) at least two shells (7, 8), between which the pressure tube (5) is arranged.

10. Heat transfer tube according to one of claims 1-9, wherein the

Heat transfer element (6) is cylindrical and has radially extending ribs (9).

1 1. heat storage (1), in particular molten salt latent heat storage, with

at least one heat transfer tube (3) according to any one of claims 1-10 and a storage medium (2), in particular a molten salt, in which the at least one heat transfer tube (3) is at least partially arranged.

12. A method for producing a heat transfer tube (3), in particular a fin tube, for a heat store (1), in particular for a molten salt latent heat store, with the following steps:

Providing (S1) a pressure tube (5) and a heat transfer element

(6);

Attaching (S2) a connection layer (10) to the pressure tube (5);

Attaching (S3) a reinforcing element (1 1) to the connecting layer (10); Attaching (S4) the heat transfer element (6) to the pressure tube (5), wherein the connecting layer (10) and the reinforcing element (11) between the

Pressure tube (5) and the heat transfer element (6) are arranged;

Reflowing (S5) the joining layer (10) to connect the pressure tube (5) to the heat transfer element (6); and

Cooling (S6) the heat transfer tube (3).

13. The method of claim 12, wherein a solder is applied to the pressure tube (5) to form the compound layer (10).

14. The method according to claim 12 or 13, wherein during the melting of the

Connecting layer (10) the reinforcing element (10) in the connecting layer

(10) is melted down.