DE102017007733A1 - Use of a wound heat exchanger as latent heat storage - Google Patents

Abstract

The invention relates to a method for the indirect heat transfer between a fusible salt compound (S) and at least one heat transfer fluid (W), wherein the salt compound (S) is stored in a jacket space (6) of a wound heat exchanger (1), wherein the jacket space (6) is surrounded by a jacket (5) of the heat exchanger (1), wherein the heat exchanger (1) comprises a plurality of tubes (30), each helically wound on a core tube (300) of the heat exchanger (1), which is in the shell space (6) along a longitudinal axis (z) of the jacket (5) extends, so that the tubes (30) form a tube bundle (3) of the heat exchanger (1) having a plurality in the radial direction (R) superposed tube layers (4), wherein the at least one heat transfer fluid (F) is guided in the tube bundle (3), and wherein heat is transferred indirectly (S) between the at least one heat transfer fluid (F) and the salt compound. Furthermore, the invention relates to a latent heat storage. 1

Description

The invention relates to a method for indirect heat transfer between a fusible salt compound and a heat transfer medium and a latent heat storage.

Latent heat storage for molten salts, with which methods of the aforementioned type are feasible, are usually based on tube registers with radially or axially finned tubes, the ribs are e.g. made of aluminum and the tubes are made of carbon steel. Small Wärmeleitstrukturen are very quickly covered by solid salt and are then ineffective, larger Wärmeleitstrukturen are relatively expensive and difficult to work.

On this basis, the present invention is therefore based on the object to provide a method for indirect heat transfer between a fusible salt compound and at least one heat transfer medium and a latent heat storage, and in particular at the same low specific cost of Heizzanzendurchzogenes volume.

This object is achieved by a method having the features of claim 1 and by a latent heat accumulator having the features of claim 10.

Advantageous embodiments of the invention are specified in the corresponding subclaims and are described below.

According to claim 1 thereafter, a method for indirect heat transfer between a fusible salt compound and at least one heat transfer medium is provided, wherein the salt compound is stored in a shell space of a wound heat exchanger, which is surrounded by a jacket of the heat exchanger, wherein the heat exchanger has a plurality of tubes, each helically wound on a core tube extending in the shell space along a longitudinal axis of the shell, so that the tubes form a tube bundle of the heat exchanger having a plurality of superimposed in the radial direction pipe layers, in particular the load of the tube bundle is removed via the core tube wherein the at least one heat transfer medium is guided in the tube bundle, and wherein heat is transferred indirectly between the at least one heat transfer medium and the salt compound.

Through the use of a wound heat exchanger in the method according to the invention or as latent heat storage, the possibility of very long pipes is advantageously given, since pressure losses play a rather subordinate role on the steam side or the side of the heat transfer medium. Corresponding distances for the solidification of the salt compound can be shown. Furthermore, the mechanical flexibility of a wound heat exchanger for phase transitions in the salt compound (especially liquid too strong and vice versa) is sufficient.

Furthermore, in particular, no heat conduction structure is provided on the outside of the tubes of the tube bundle.

Particularly preferably, the salt compound is a so-called phase change material. In such a phase change material (PCM), the latent heat of fusion is much greater than the heat that can store the material due to its normal specific heat capacity (without the phase change effect).

With the aid of the salt compound or the phase change material, the heat of the heat transfer fluid, which may be any process medium or process stream, can be stored or released again at a virtually constant temperature by means of the latent heat (for example, in the liquid-solid phase transition ).

Accordingly, according to an embodiment of the method according to the invention, it is provided that the salt compound is melted during the indirect heat transfer in order to store energy in the salt compound or that the salt compound solidifies during the indirect heat transfer in order to extract energy from the salt compound. Preferably, the energy to be stored is solar energy, that is, energy previously used e.g. was obtained by means of a photovoltaic system or solar thermal system.

As already explained, it is provided according to a preferred embodiment of the invention that the tubes of the tube bundle have a circular cross-section tube wall, wherein the tube wall forms an outer side of the respective tube, which contacts the salt compound located in the shell space. That is, the tubes of the tube bundle have no heat transfer ribs on their outside.

Furthermore, according to a preferred embodiment of the invention, it is provided that the method is carried out in a system for generating energy from sunlight, in particular in order to store solar energy thus generated in the salt compound or to remove solar energy previously stored in the salt compound.

Furthermore, it is provided according to an embodiment of the invention that are provided between each two adjacent pipe layers along the longitudinal axis extending spacers which abut both sides of the respective pipe layer. The spacers can be welded to the pipe layers.

Furthermore, it is provided according to an embodiment of the method according to the invention that the salt compound has a melting temperature in the range of 250 ° C to 600 ° C.

Furthermore, according to one embodiment of the method according to the invention, it is provided that the salt compound is one of the following salt compounds or has one of the following salt compounds: sodium nitrite, sodium chloride, potassium nitrate, lithium nitrate, sodium hydroxide.

A further aspect of the present invention relates to a latent heat accumulator according to claim 10, which is provided in particular for use in the method according to the invention and in particular according to the features already described above can be further configured.

According to claim 10, a latent heat storage is disclosed, comprising a fusible salt compound, which is stored in a shell space of the latent heat storage, wherein the jacket space is surrounded by a shell of the latent heat storage, wherein the latent heat storage having a plurality of tubes, which are each helically wound on a core tube extending in the shell space along a longitudinal axis of the shell so that the tubes form a tube bundle for conducting a heat transfer fluid such that heat is indirectly transferable between the heat transfer fluid and the salt compound, and wherein the tube bundle has a plurality of tube layers superimposed in the radial direction, wherein in particular the load of the tube bundle is removed via the core tube or via webs which are suspended at the top.

• 1 einen erfindungsgemäßen Latentwärmespeicher in Form eines gewickelten Wärmeübertragers, der eine schmelzbare Salzverbindung zum Speichern von Energie, insbesondere Sonnenenergie aufweist.

Further details and advantages of the invention will be explained by the following description of an embodiment with reference to the figures. It shows:

• 1 a latent heat accumulator according to the invention in the form of a wound heat exchanger, which has a fusible salt compound for storing energy, in particular solar energy.

The 1 shows a latent heat storage according to the invention 1 or the inventive method based on the latent heat storage 1 , The latent heat storage 1 is inventively by a wound heat exchanger 1 formed a coat 5 having a jacket space 6 surrounding with a meltable salt compound S is filled, which is a tube bundle 3 surrounds the heat exchanger. The salt compound is in particular a phase change material (see above).

The tube bundle 3 is exemplary in the 1 shown in a perspective and partially sectioned view. It has several tubes 30 for receiving at least one heat transfer medium (eg water or water vapor) W , where the pipes 30 each helical, ie, helical, on a core tube 300 of the heat exchanger 1 are wound along a longitudinal axis z in the mantle room 6 extends (in particular coaxially to the jacket 5 ), so that the tube bundle 3 several pipe layers 4 which is in a radial direction R of the tube bundle 3 are arranged one above the other. The respective radial direction R stands perpendicular to the longitudinal axis z or the core tube 300 and points away from it or to the outside.

According to 1 is the tube bundle 3 from the particular cylindrical shaped jacket 5 Surrounded by the mantle room 6 limited, in which the tube bundle 3 together with the core tube 300 is arranged.

In the mantle room 6 is for example via neck 52 . 53 the salt compound (eg in the form of a molten salt) can be introduced or possibly from the shell space 6 removable.

The at least one heat transfer medium W will have at least one neck 50 , for example, at the head of the heat exchanger 1 is provided in the tube bundle 3 initiated, and at least one nozzle 51 , which is provided for example at a lower bottom of the heat exchanger, again out of the tube bundle 3 deducted. The at least one heat transfer fluid F and the salt compound S can thus indirectly exchange heat with each other.

In this case, for example, the at least one heat transfer fluid F the salt compound in the solid state S melt, with the salt compound S comparatively much heat energy (heat of fusion) absorbs. At a later date, the salt compound S If necessary, be discharged by the salt compound S through a suitably tempered heat transfer medium F is solidified, the salt compound S the previously recorded amount of heat as solidification heat back to that in the respective tube 20 guided fluid F emits, which is heated accordingly.

In particular, there is the possibility of the pipes 30 into several tube groups to divide (in the 1 For example, three tube groups are shown), which can be loaded, for example, with different media.

Like in the 1 is further shown, are preferably between an innermost layer of the tube bundle 3 and the core tube 300 as well as between two adjacent pipe layers 4 of the tube bundle 3 a particular constant plurality of webs 10 provided, with the webs 10 each extend along the longitudinal axis z and in the radial direction R are arranged one above the other.

By means of the spacers, in particular the distance between the individual pipe layers 4 to the phase change material or the salt compound used S be adjusted.

LIST OF REFERENCE NUMBERS

1

Heat exchanger or latent heat storage

3

tube bundle

4

pipe layer

5

coat

6

shell space

10

web

30

Tube

50, 51, 52, 53

Support

300

core tube

S

Salt compound or phase change material

W

Heat transfer fluid

R

Radial direction

Z

longitudinal axis

Claims (10)

Method for indirect heat transfer between a fusible salt compound (S) and at least one heat transfer fluid (W), the salt compound (S) being stored in a jacket space (6) of a wound heat exchanger (1), the jacket space (6) being covered by a jacket (6) 5) of the heat exchanger (1) is surrounded, wherein the heat exchanger (1) has a plurality of tubes (30) which are each helically wound on a core tube (300) of the heat exchanger (1) extending in the shell space (6) along a longitudinal axis (z) of the jacket (5) extends, so that the tubes (30) form a tube bundle (3) of the heat exchanger (1) having a plurality in the radial direction (R) superposed tube layers (4), wherein the at least one Heat transfer fluid (F) in the tube bundle (3) is guided, and wherein indirectly transfer heat between the at least one heat transfer fluid (F) and the salt compound (S) is. Method according to Claim 1 , characterized in that the salt compound (S) is a phase change material. Method according to Claim 1 or 2 , characterized in that the salt compound (S) is melted in the indirect heat transfer to store energy in the salt compound (S), or that the salt compound (S) solidifies in the indirect heat transfer to extract energy from the salt compound (S) , Method according to one of the preceding claims, characterized in that the tubes (30) of the tube bundle (3) have a circular cross-section tube wall, wherein the tube wall forms an outer side of the respective tube (30) which contacts the salt compound (S). Method according to one of the preceding claims, characterized in that the method is carried out in a plant for generating energy from sunlight, and / or that the stored energy is solar energy. Method according to one of the preceding claims, characterized in that between adjacent pipe layers (4) along the longitudinal axis (z) extending spacers (10) are arranged, against which the adjacent pipe layers (4) respectively. Method according to one of the preceding claims, characterized in that the salt compound (S) has a melting temperature in the range of 250 ° C to 600 ° C. Method according to one of the preceding claims, characterized in that the salt compound (S) is one of the following salt compounds or one of the following salt compounds: sodium nitrite, sodium chloride, potassium nitrate, lithium nitrate, sodium hydroxide. Method according to one of the preceding claims, characterized in that the load of the tube bundle (3) over the core tube (300) is removed. Latent heat storage, comprising a salt compound (S), which is stored in a shell space of the latent heat accumulator (1), wherein the jacket space (6) by a jacket (5) of the latent heat accumulator (1) is surrounded, wherein the Latent heat accumulator (1) has a plurality of tubes (30) each helically wound on a core tube (300) extending in the shell space (6) along a longitudinal axis (z) of the shell (5), so that the tubes ( 30) form a tube bundle (3) for guiding a heat transfer medium (W) such that heat is transferable indirectly between the heat transfer medium (W) and the salt compound (S), and wherein the tube bundle (3) has several in the radial direction (R) has superposed pipe layers (4), and wherein in particular the load of the tube bundle (3) on the core tube (300) is removed.

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