Integrated fused salt steam generator

Abstract

The utility model relates to the technical field of heat exchange equipment, in particular to an integrated fused salt steam generator which comprises a fused salt pipeline and a shell, the fused salt pipeline is communicated with the shell, the shell is provided with a water supply inlet and a steam outlet, a lower header is arranged in the shell and close to the water supply inlet, and the steam outlet is communicated with the lower header. An upper collecting box is arranged in the shell and close to the steam outlet, a middle collecting box is arranged between the upper collecting box and the lower collecting box, a plurality of upper heat exchange pipes are arranged between the upper collecting box and the middle collecting box, a plurality of lower heat exchange pipes are arranged between the lower collecting box and the middle collecting box, a steam-water separator is arranged in the middle collecting box, and the steam-water separator is arranged in the middle collecting box. And a heat exchange cavity is formed between the upper header and the lower header. Compared with an existing structure that a steam generator and a steam pocket are separated, the steam generator is integrally designed, the structure is simpler, manufacturing is easy, and the occupied area is smaller; the vertically-arranged heat exchange tube is shorter than a coil tube, and the problem that the water vapor flow resistance is too large in the high-temperature environment is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of heat exchange equipment, in particular to an integrated molten salt steam generator. Background Art

[0002] Molten salt steam generators exchange heat between high-temperature molten salt and water to produce hot water or steam. In the field of solar thermal power generation, these generators supply the steam generated to steam turbines or other equipment. Molten salt steam generators are core equipment for solar thermal power generation and molten salt energy storage, providing clean energy steam.

[0003] The commonly used molten salt steam generator system at present is mainly composed of a variety of heat exchange main equipment and auxiliary equipment such as preheater, evaporator, steam drum, superheater, and water, steam and molten salt pipelines. The evaporator and steam drum are mostly separated. The high-temperature molten salt is heat-exchanged step by step in the above-mentioned heat exchangers to achieve preheating, evaporation and superheating of water.

[0004] For example, Chinese patent publication number CN102966935A discloses a molten salt steam generator consisting of a steam drum, a steam generator tank, and a lower header. The steam drum is located at the top of the molten salt steam generator, the steam generator tank is located in the middle of the molten salt steam generator, and the lower header is located at the bottom of the molten salt steam generator, below the steam generator tank; the lower header supports the molten salt steam generator. The steam drum consists of a steam drum head, a steam drum shell, a steam outlet, a pressure port, and a safety valve port; the steam generator tank consists of a steam generator tank outer shell, a steam generator tank inner shell, a hand hole, and a steam generator head. The steam generator tank inner shell is connected to the steam drum via a steam riser. The lower header consists of a lower header inlet, a lower header outlet, a lower header shell, a lower header head, auxiliary heat exchange medium pipelines, and phase change energy storage materials. The above disclosure adopts a structure in which the steam generator tank is separated from the steam drum, which is relatively complex, occupies a large area, and has high manufacturing costs. Utility Model Content

[0005] In response to the problems of current molten salt steam generators such as complex structure, large footprint and high manufacturing cost, the utility model proposes a molten salt steam generator with a relatively simple structure. Its structure is relatively simple, the manufacturing cost is low, and the heat exchange tubes are shorter than the heat exchange tubes of the currently commonly used molten salt steam generators. The problem of high steam-water flow resistance in a high temperature environment caused by excessively long heat exchange tubes will not occur.

[0006] In order to achieve the above technical effects, the present invention proposes:

[0007] An integrated molten salt steam generator comprises a molten salt pipeline and a shell, the molten salt pipeline being connected to the shell, the shell being provided with a water supply inlet and a steam outlet, a lower header being provided in the shell near the water supply inlet, an upper header being provided in the shell near the steam outlet, a middle header being provided between the upper and lower headers, a plurality of upper heat exchange tubes being provided between the upper and middle headers, a plurality of lower heat exchange tubes being provided between the lower and middle headers, a steam-water separator being provided in the middle header, and a heat exchange cavity being formed between the upper and lower headers.

[0008] An upper header, a middle header and a lower header are provided in the shell. The lower header is used for water intake and storage, the middle header is provided with a gas-liquid separator, and the upper header is used to discharge high-temperature water vapor; an upper heat exchange pipe is provided between the upper header and the middle header, and a lower heat exchange pipe is provided between the middle header and the lower header. The upper heat exchange pipe and the lower heat exchange pipe are used to conduct steam and water and exchange heat with the high-temperature molten salt in the heat exchange cavity.

[0009] The upper header has an upper header baffle, and the lower header has a lower header baffle. The upper header baffle is provided with a steam hole, and the lower header baffle is provided with a water supply hole. The internal space of the shell between the upper and lower header baffles constitutes the heat exchange cavity. Water enters the heat exchange cavity through the water supply hole, and steam is discharged from the heat exchange cavity through the steam hole.

[0010] One end of the upper heat exchange tube is connected to the steam hole, and the other end is connected to the end surface of the middle header close to the upper header. One end of the lower heat exchange tube is connected to the water supply hole, and the other end is connected to the end surface of the middle header close to the lower header.

[0011] The molten salt pipeline includes a molten salt inlet and a molten salt loop. The molten salt inlet includes a first branch and a second branch. The first branch is provided with four to six molten salt inlets surrounding the outer side of the shell, and the second branch is provided with four to six molten salt inlets surrounding the outer side of the shell. The molten salt loop is provided with four to six molten salt outlets surrounding the outer side of the shell. The molten salt inlet, heat exchange chamber, and molten salt loop constitute the entire high-temperature molten salt circuit. High-temperature molten salt enters the heat exchange chamber from the molten salt inlet and returns to the molten salt loop from the molten salt outlet. The molten salt inlet is divided into two branches.

[0012] The molten salt inlet connected to the first branch is located between the upper and middle headers and is close to the upper header. The molten salt inlet connected to the second branch is located between the lower and middle headers and is close to the middle header. The molten salt outlet is located between the lower and middle headers and is close to the lower header. The first branch delivers high-temperature molten salt to the upper heat exchange tube, and the second branch delivers high-temperature molten salt to the lower heat exchange tube. After heat exchange, the high-temperature molten salt enters the molten salt circuit through the molten salt outlet.

[0013] The steam-water separator includes a cyclone separator and a shutter separator.

[0014] The heat exchange chamber is equipped with a plurality of baffles, one located between the upper and middle headers, and the other between the lower and middle headers. Baffles form baffled flow paths between the baffles. The baffles are staggered within the heat exchange chamber to form baffled flow paths, ensuring a more uniform flow of the high-temperature molten salt and increasing its contact time with the upper and lower heat exchange tubes.

[0015] The baffle is provided with a plurality of heat exchange tube through holes, the upper heat exchange tube is passed through the heat exchange tube through holes, and the lower heat exchange tube is passed through the heat exchange tube through holes.

[0016] The upper heat exchange tube and the lower heat exchange tube both have expansion bends, which prevent the upper and lower header baffles from being squeezed by deformation of the upper and lower heat exchange tubes in a high-temperature environment.

[0017] The beneficial effects of the utility model are:

[0018] Compared with the current structure in which the steam generator and the steam drum are separated, the structure of the utility model is simpler, occupies a small area, is easy to manufacture, and shortens the manufacturing cycle; the heat exchange tubes are arranged vertically and are shorter than the coils, avoiding excessive water vapor flow resistance in high temperature environments; the molten salt inlet is divided into two layers to ensure the heat exchange temperature difference between the high-temperature molten salt and water. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the integrated molten salt steam generator in Example 1.

[0020] Figure 2 Schematic diagram of the structure of the baffle in Example 1.

[0021] Figure 3 This is a schematic structural diagram of the integrated molten salt steam generator in Example 2.

[0022] Figure 4 Schematic diagram of the structure of the baffle and the lower heat exchange tube in Example 2.

[0023] Figure Number:

[0024] 1. Shell; 2. Molten salt pipeline; 3. Heat exchange chamber; 4. Baffle; 5. Insulation layer; 6. Expansion bend; 7. Molten salt regulating valve; 11. Water inlet; 12. Steam outlet; 13. Upper header; 14. Middle header; 15. Lower header; 16. Upper heat exchange tube; 17. Lower heat exchange tube; 21. Molten salt inlet; 22. Molten salt circuit; 23. Molten salt inlet; 24. Molten salt outlet; 41. Heat exchange tube through-hole; 131. Upper header baffle; 132. Steam hole; 141. Gas-liquid separator; 151. Lower header baffle; 152. Water inlet; 211. First branch; 212. Second branch. DETAILED DESCRIPTION

[0025] The following describes the implementation of the present invention through specific embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0026] The utility model provides an integrated molten salt steam generator. The preferred embodiment of the integrated molten salt steam generator is described below.

[0027] Example 1

[0028] like Figure 1As shown, an integrated molten salt steam generator includes a molten salt pipeline 2, which includes a molten salt inlet 21 and a molten salt loop 22. The molten salt inlet 21 is provided with two branch inlets; it includes a shell 1, which is in the shape of a capsule as a whole and is made of 316L stainless steel. An insulation layer 5 is provided on the outside of the shell 1, and a water inlet 11 and a steam outlet 12 are provided at both ends of the shell 1. The water inlet 11 is used to connect to a water source, and the steam outlet 12 is used to discharge the generated steam and connect to other equipment to send the steam out; a lower header 15 is provided near the water inlet 11 inside the shell 1, and the lower header 15 has a lower header baffle 151. The lower header baffle 151 is located in a circumferential plane inside the shell 1, and the lower header 15 is formed by the lower header baffle 151 and the inner wall of the shell 1 near the water inlet 11. The lower header 15 is used to store the water source from the water inlet 11; the shell 1 is provided near the steam outlet 12 The upper header 13 has an upper header baffle 131, which is located in a circumferential plane inside the shell 1. The upper header 13 is formed by the upper header baffle 131 and the inner wall of the shell 1 near the steam outlet 12. The upper header 13 is used to store steam and process the steam for delivery through the steam outlet 12; a middle header 14 is provided between the upper header 13 and the lower header 15. The middle header 14 is box-shaped and independent of the shell 1. A support plate is provided inside the shell 1, which is fixed to the inner wall of the shell 1. The middle header 14 is fixedly connected to the support plate. A gas-liquid separator 141 is provided inside the middle header 14 for gas-liquid separation of steam; a cyclone separator is selected as the gas-liquid separator; a heat exchange cavity 3 is formed inside the shell 1 between the upper header 13 and the lower header 15. The heat exchange cavity 3 contains high-temperature molten salt, and heat exchange between the molten salt and water is carried out in the heat exchange cavity 3.

[0029] The upper header baffle 131 is provided with a steam hole 132, and the lower header baffle 151 is provided with a water supply hole 152; a plurality of upper heat exchange tubes 16 are provided between the upper header 13 and the middle header 14, and the upper heat exchange tubes 16 are vertically arranged in the heat exchange cavity 3, the upper end of the upper heat exchange tube 16 is connected to the steam hole 132, and the lower end is connected to the top of the middle header 14; a plurality of lower heat exchange tubes 17 are provided between the lower header 15 and the middle header 14, and the upper heat exchange tubes 17 are vertically arranged in the heat exchange cavity 3, the upper end of the lower heat exchange tube 17 is connected to the bottom of the middle header 14, and the lower end is connected to the water supply hole 152. The steam hole 132 is used to pass steam into the upper header 13, and the water supply hole 152 is used to pass water into the lower heat exchange tube 17; the upper heat exchange tube 16 and the lower heat exchange tube 17 are both made of 316L stainless steel, and each of the upper heat exchange tube 16 and the lower heat exchange tube 17 has an expansion bend 6.

[0030] The molten salt pipeline 2 includes a molten salt inlet 21 and a molten salt loop 22. Both the molten salt inlet 21 and the molten salt loop 22 are provided with a molten salt regulating valve 7 for regulating the flow of high-temperature molten salt. The molten salt inlet 21 is provided with two branches, including a first branch 211 and a second branch 212. The molten salt inlet 21 is provided with eight molten salt inlets 23 around the outer side of the shell 1, which are four molten salt inlets 23 connected to the first branch 211 and four molten salt inlets 23 connected to the second branch 212. The first branch 211 is provided with a molten salt inlet 23 connected to the second branch 212. The four molten salt inlets 23 connected to the branch 211 are evenly surrounded on the circumferential side of the shell 1 of the heat exchange cavity 3 close to the upper header baffle 131, and the four molten salt inlets 23 connected to the second branch 212 are evenly surrounded on the circumferential side of the shell 1 of the heat exchange cavity 3 close to the bottom surface of the middle header 14; the molten salt circuit 22 is provided with four molten salt outlets 24 around the outer side of the shell 1, and the molten salt outlets 24 are provided between the lower header 15 and the middle header 14 and close to the circumferential side of the shell 1 of the lower header 15.

[0031] Eight baffles 4 are provided in the heat exchange cavity 3, five baffles 4 are provided between the upper header 13 and the middle header 14, and three baffles 4 are provided between the lower header 15 and the middle header 14. The baffles 4 are fixedly connected to the inner wall of the shell 1 and have a gap with the inner wall of the shell 1. The arrangement positions of two adjacent baffles 4 are opposite, and a baffle flow channel is formed between the baffles 4, so that the molten salt forms a baffle flow pattern, so that the high-temperature molten salt flows evenly in the heat exchange cavity 3, and prevents the high-temperature molten salt from flowing quickly from the molten salt inlet 23 to the molten salt outlet 24; Figure 2 As shown, a plurality of heat exchange tube through holes 41 are provided on the folding plate. The upper heat exchange tube 16 is passed through the heat exchange tube through hole 41 between the upper header 13 and the middle header 14 , and the lower heat exchange tube 17 is passed through the heat exchange tube through hole 41 between the lower header 15 and the middle header 14 .

[0032] Working process of integrated molten salt steam generator:

[0033] The water supply inlet 11 of the shell 1 is connected to the water source, and the water source enters the lower header 15 and fills the lower header 15. The water source enters the lower heat exchange tube 17 through the water supply hole 152 of the lower header baffle 151; the high-temperature molten salt enters respectively through the two branches of the molten salt inlet 21, and the high-temperature molten salt enters the four molten salt inlets 23 located at the highest point of the heat exchange cavity 3 through the first branch 211, and enters the four molten salt inlets 23 located at the lower end of the middle header 14 through the second branch 212. Under the action of the baffle 4, the high-temperature molten salt forms a baffled flow pattern, and the high-temperature molten salt flows evenly in the heat exchange cavity 3 and enters the molten salt circuit 22 through the molten salt outlet 24 at the bottom of the heat exchange cavity 3; the water in the lower heat exchange tube 17 passes through the lower exchange The heat pipe 17 exchanges heat with the high-temperature molten salt, is heated to boiling and generates steam, completes pre-heat exchange and enters the middle header 14, and the cyclone separator in the middle header 14 separates the steam into gas and liquid and generates water vapor which enters the upper heat exchange tube 16. The separated liquid water continues to exchange heat in the middle header 14 to form steam; the water vapor in the upper heat exchange tube 16 exchanges heat with the high-temperature molten salt through the upper heat exchange tube 16, reaches a superheated state, enters the upper header 13 through the steam hole 132, and is sent out through the steam outlet 12 to enter the subsequent equipment. During this process, the flow rate of the high-temperature molten salt is adjusted by the molten salt regulating valve 7, and the water inlet of the water feed inlet 11 is controlled at the same time to achieve control of the discharge volume of the steam outlet 12.

[0034] Example 2

[0035] Different from the first embodiment, the integrated molten salt steam generator in the second embodiment sets the lower heat exchange tube 17 to an S-bend shape to increase the contact area between the lower heat exchange tube and the high-temperature molten salt, thereby quickly heating the water in the lower heat exchange tube 17.

[0036] like Figure 3As shown, an integrated molten salt steam generator includes a molten salt pipeline 2, which includes a molten salt inlet 21 and a molten salt loop 22. The molten salt inlet 21 is provided with two branch inlets; it includes a shell 1, which is in the shape of a capsule as a whole and is made of 316L stainless steel. An insulation layer 5 is provided on the outside of the shell 1, and a water inlet 11 and a steam outlet 12 are provided at both ends of the shell 1. The water inlet 11 is used to connect to a water source, and the steam outlet 12 is used to discharge the generated steam and connect to other equipment to send the steam out; a lower header 15 is provided near the water inlet 11 inside the shell 1, and the lower header 15 has a lower header baffle 151. The lower header baffle 151 is located in a circumferential plane inside the shell 1, and the lower header 15 is formed by the lower header baffle 151 and the inner wall of the shell 1 near the water inlet 11. The lower header 15 is used to store the water source from the water inlet 11; the shell 1 is provided near the steam outlet 12 The upper header 13 has an upper header baffle 131, which is located in a circumferential plane inside the shell 1. The upper header 13 is formed by the upper header baffle 131 and the inner wall of the shell 1 near the steam outlet 12. The upper header 13 is used to store steam and process the steam for delivery through the steam outlet 12; a middle header 14 is provided between the upper header 13 and the lower header 15. The middle header 14 is box-shaped and independent of the shell 1. A support plate is provided inside the shell 1, which is fixed to the inner wall of the shell 1. The middle header 14 is fixedly connected to the support plate. A gas-liquid separator 141 is provided inside the middle header 14 for gas-liquid separation of steam; a cyclone separator is selected as the gas-liquid separator; a heat exchange cavity 3 is formed inside the shell 1 between the upper header 13 and the lower header 15. The heat exchange cavity 3 contains high-temperature molten salt, and heat exchange between the molten salt and water is carried out in the heat exchange cavity 3.

[0037] The upper header baffle 131 is provided with a steam hole 132, and the lower header baffle 151 is provided with a water supply hole 152; a plurality of upper heat exchange tubes 16 are provided between the upper header 13 and the middle header 14, and the upper heat exchange tubes 16 are vertically arranged in the heat exchange cavity 3, the upper ends of the upper heat exchange tubes 16 are connected to the steam holes 132, and the lower ends are connected to the top of the middle header 14; a plurality of lower heat exchange tubes 17 are provided between the lower header 15 and the middle header 14, and the lower heat exchange tubes 17 are S-shaped and arranged in the heat exchange cavity 3, the upper ends of the lower heat exchange tubes 17 are connected to the bottom of the middle header 14, and the lower ends are connected to the water supply hole 152; a total of 4 lower heat exchange tubes are provided (for easy observation in the figure, Figure 3 Only two are drawn in the figure); the steam hole 132 is used to pass the steam into the upper header 13, and the water supply hole 152 is used to pass the water source into the lower heat exchange tube 17; the upper heat exchange tube 16 and the lower heat exchange tube 17 are made of 316L stainless steel, and each upper heat exchange tube 16 and the lower heat exchange tube 17 have an expansion bend 6.

[0038] The molten salt pipeline 2 includes a molten salt inlet 21 and a molten salt loop 22. Both the molten salt inlet 21 and the molten salt loop 22 are provided with a molten salt regulating valve 7 for regulating the flow of high-temperature molten salt. The molten salt inlet 21 is provided with two branches, including a first branch 211 and a second branch 212. The molten salt inlet 21 is provided with eight molten salt inlets 23 around the outer side of the shell 1, which are four molten salt inlets 23 connected to the first branch 211 and four molten salt inlets 23 connected to the second branch 212. The first branch 211 is provided with a molten salt inlet 23 connected to the second branch 212. The four molten salt inlets 23 connected to the branch 211 are evenly surrounded on the circumferential side of the shell 1 of the heat exchange cavity 3 close to the upper header baffle 131, and the four molten salt inlets 23 connected to the second branch 212 are evenly surrounded on the circumferential side of the shell 1 of the heat exchange cavity 3 close to the bottom surface of the middle header 14; the molten salt circuit 22 is provided with four molten salt outlets 24 around the outer side of the shell 1, and the molten salt outlets 24 are provided between the lower header 15 and the middle header 14 and close to the circumferential side of the shell 1 of the lower header 15.

[0039] Seven baffles 4 are provided in the heat exchange cavity 3, five baffles 4 are provided between the upper header 13 and the middle header 14, and two baffles 4 are provided between the lower header 15 and the middle header 14. The baffles 4 are fixedly connected to the inner wall of the shell 1 and have a gap with the inner wall of the shell 1. The arrangement positions of two adjacent baffles 4 are opposite, and a baffle flow channel is formed between the baffles 4, so that the molten salt forms a baffle flow pattern, so that the high-temperature molten salt flows evenly in the heat exchange cavity 3, and prevents the high-temperature molten salt from flowing quickly from the molten salt inlet 23 to the molten salt outlet 24; the baffle between the upper header 13 and the middle header 14 is provided with a plurality of heat exchange tube through holes 41 (the same as in Example 1), and the upper heat exchange tube 16 is passed through the heat exchange tube through hole 41 between the upper header 13 and the middle header 14; as shown Figure 4 As shown, the two lower heat exchange tubes 17 with longer horizontal sections bypass the baffle 4 at the bend, and the two lower heat exchange tubes 17 with shorter horizontal sections directly pass through the gaps on both sides of the baffle 3.

[0040] The S-bend lower heat exchange tube 17 in Example 2 can also be configured as a half-S-bend and half-vertical arrangement, i.e., the lower heat exchange tube 17 near the lower header 15 is S-bend, while the lower heat exchange tube 17 near the middle header 14 is vertically arranged. This arrangement has the advantage that as the high-temperature molten salt flows toward the bottom of the heat exchange cavity 3, its temperature decreases. The S-bend structure increases the heat exchange area between the water and the high-temperature molten salt, while the vertical arrangement allows water vapor to enter the middle header 14 more smoothly.

[0041] Compared with the molten salt steam generator in the prior art, the integrated molten salt steam generator proposed in the present invention has a simpler structure, lower manufacturing cost, and occupies a smaller area; the heat exchange tube is shorter and vertically arranged, avoiding excessively long heat exchange tubes causing greater flow resistance to water vapor under high temperature conditions; the molten salt inlet is divided into two layers, ensuring the heat exchange temperature difference between the high-temperature molten salt and water.

Claims

1. An integrated molten salt steam generator, comprising a molten salt pipeline, characterized in that: The heat exchange chamber comprises a shell, the molten salt pipeline is connected to the shell, the shell is provided with a water inlet and a steam outlet, a lower header is provided in the shell near the water inlet, an upper header is provided in the shell near the steam outlet, a middle header is provided between the upper and lower headers, a plurality of upper heat exchange tubes are provided between the upper and middle headers, a plurality of lower heat exchange tubes are provided between the lower and middle headers, a steam-water separator is provided in the middle header, and a heat exchange cavity is formed between the upper and lower headers.

2. The integrated molten salt steam generator according to claim 1, characterized in that: The upper header is provided with an upper header baffle, and the lower header is provided with a lower header baffle. The upper header baffle is provided with a steam hole, and the lower header baffle is provided with a water supply hole.

3. The integrated molten salt steam generator according to claim 2, characterized in that: One end of the upper heat exchange tube is connected to the steam hole, and the other end is connected to the end surface of the middle header close to the upper header. One end of the lower heat exchange tube is connected to the water supply hole, and the other end is connected to the end surface of the middle header close to the lower header.

4. The integrated molten salt steam generator according to claim 1, characterized in that: The molten salt pipeline includes a molten salt inlet and a molten salt loop. The molten salt inlet includes a first branch and a second branch. The first branch is provided with 4 to 6 molten salt inlets around the outer side of the shell, and the second branch is provided with 4 to 6 molten salt inlets around the outer side of the shell. The molten salt loop is provided with 4 to 6 molten salt outlets around the outer side of the shell.

5. The integrated molten salt steam generator according to claim 4, characterized in that: The molten salt inlet connected to the first branch is located between the upper header and the middle header and is close to the upper header, the molten salt inlet connected to the second branch is located between the lower header and the middle header and is close to the middle header, and the molten salt outlet is located between the lower header and the middle header and is close to the lower header.

6. The integrated molten salt steam generator according to claim 1, characterized in that: The steam-water separator includes a cyclone separator and a shutter separator.

7. An integrated molten salt steam generator according to any one of claims 1 to 6, characterized in that: A plurality of baffles are provided in the heat exchange cavity. The baffles are located between the upper header and the middle header, and between the lower header and the middle header. Baffle flow channels are formed between the baffles.

8. The integrated molten salt steam generator according to claim 7, characterized in that: The baffle is provided with a plurality of heat exchange tube through holes, the upper heat exchange tube is passed through the heat exchange tube through holes, and the lower heat exchange tube is passed through the heat exchange tube through holes.

9. The integrated molten salt steam generator according to claim 7, characterized in that: The upper heat exchange tube and the lower heat exchange tube both have expansion bends.

10. The integrated molten salt steam generator according to claim 7, characterized in that: A heat-insulating layer is provided on the outer side of the shell.

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