Fused salt electric heater

Abstract

The utility model relates to the technical field of heaters, in particular to a fused salt electric heater which comprises an electric heating pipe, an inner-layer shell, an outer-layer shell, a fused salt inlet and a fused salt outlet. The fused salt inlet and the fused salt outlet are close to the two ends of the outer-layer shell respectively and communicate with the cavity of the inner-layer shell, and the electric heating pipe is located in the cavity of the inner-layer shell; and a phase change material is filled between the inner-layer shell and the outer-layer shell. Aiming at the technical problem that the existing fused salt electric heater cannot adapt to thermal shock caused by rapid load change, the phase-change material is utilized to absorb or release heat, and the temperature of a shell of the electric heater is maintained not to change drastically, so that the service life is greatly prolonged, and meanwhile, the electric heater can be prevented from being overheated or frozen and blocked.

Description

Technical Field

[0001] The utility model relates to the technical field of heaters, in particular to a molten salt electric heater. Background Art

[0002] With the increase in the proportion of new energy, my country's power structure is being built towards a new power system with new energy as the main body. However, due to the unpredictability of new energy such as photovoltaics and wind power, it is easy to cause the frequency of the power grid to change, affecting the stable operation of the power grid. The existing molten salt electric heater can adjust the frequency of the power grid by quickly responding to and absorbing the load. However, the rapid load change will cause the existing electric heater to frequently change power or start and stop frequently, which will increase energy loss and reduce thermal efficiency on the one hand, and cause the electric heater to withstand rapid temperature changes on the other hand, resulting in a reduction in life. Utility Model Content

[0003] In view of the technical problem that existing molten salt electric heaters cannot adapt to the thermal shock caused by rapid load changes, the utility model provides a molten salt electric heater, which uses phase change materials to absorb or release heat to maintain the shell temperature of the electric heater from changing drastically, thereby greatly extending the service life and preventing the electric heater from overheating or freezing.

[0004] The technical solution provided by the utility model is: a molten salt electric heater, comprising an electric heating tube, an inner shell, an outer shell, a molten salt inlet and a molten salt outlet; the molten salt inlet and the molten salt outlet are respectively close to the two ends of the outer shell and are connected to the cavity of the inner shell, and the electric heating tube is located in the cavity of the inner shell; the inner shell and the outer shell are filled with a phase change material.

[0005] Optionally, along the direction from the molten salt inlet to the molten salt outlet, the inner shell and the outer shell are divided into n sections of filling space, different phase change materials are arranged in different filling spaces, and the crystallization temperature range of the phase change material increases successively along the direction from the molten salt inlet to the molten salt outlet.

[0006] Optionally, a plurality of baffles are arranged in the inner shell, and the baffles are spaced and staggered to form a curved flow channel.

[0007] Optionally, a guide surface is provided at the connection between the baffle and the inner shell.

[0008] Optionally, the guide surface is an inclined surface or a curved surface.

[0009] Optionally, the phase change material is an alloy, a molten salt or a sugar alcohol.

[0010] Optionally, a corrosion-resistant coating is provided on the inner wall of the outer shell and the outer wall of the inner shell.

[0011] Optionally, a junction box is further included, and the junction box is electrically connected to the electric heating tube.

[0012] Beneficial Effects

[0013] The technical solution provided by the utility model has the following beneficial effects compared with the prior art: in order to address the technical problem that the existing molten salt electric heater cannot adapt to the thermal shock caused by rapid load changes, the utility model utilizes phase change materials to absorb or release heat to maintain the shell temperature of the electric heater from changing dramatically, thereby greatly extending its service life and preventing the electric heater from overheating or freezing. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic structural diagram of a molten salt electric heater proposed in an embodiment of the utility model. DETAILED DESCRIPTION

[0015] In order to further understand the content of the utility model, the utility model is described in detail in conjunction with the accompanying drawings and embodiments.

[0016] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the relevant utility model, rather than to limit the utility model. It should also be noted that, for the convenience of description, only the parts related to the utility model are shown in the accompanying drawings. The words "first", "second", etc. described in the present utility model are set for the convenience of describing the technical solution of the present utility model, and have no specific limiting effect. They are all general references and do not constitute a limiting effect on the technical solution of the present utility model. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments in the present application can be combined with each other. In the description of the present utility model, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between the insides of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances. Multiple technical solutions in the same embodiment, and multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions that do not have contradictions or conflicts, all of which are within the scope of protection required by the present utility model.

[0017] Example 1

[0018] Combined with Figure 1 This embodiment proposes a molten salt electric heater, including an electric heating tube 7, an inner shell 5, an outer shell 2, a molten salt inlet 9 and a molten salt outlet 6; the molten salt inlet 9 and the molten salt outlet 6 are respectively close to the two ends of the outer shell 2 and communicated with the cavity 8 of the inner shell 5, and the electric heating tube 7 is located in the cavity 8 of the inner shell 5; the inner shell 5 and the outer shell 2 are filled with a phase change material 3. It also includes a junction box 1, which is electrically connected to the electric heating tube 7.

[0019] A molten salt electric heater of the present embodiment fills a phase change material 3 between an inner shell 5 and an outer shell 2, and utilizes the phase change material 3 to absorb or release heat to ensure thermal balance and maintain the temperature of the inner shell 5 and the outer shell 2 of the electric heater from changing dramatically, thereby greatly extending the service life and preventing the molten salt electric heater from overheating or freezing.

[0020] Among them, the phase change material 3 is located between the inner shell 5 and the outer shell 2 to buffer the thermal shock. The phase change material 3 is generally selected according to the specific molten salt type, or according to the operating temperature of the molten salt electric heater. The temperature of the electric heater remains basically unchanged during operation. In order to maintain the temperature of the inner shell 5 and the outer shell 2 unchanged, the starting crystallization temperature and the crystallization completion temperature, or the temperature range, of the selected phase change material 3 can be adapted to the operating temperature of the inner shell 5 and the outer shell 2, that is, when the electric heater is working normally, it is sufficient to ensure that the selected phase change material 3 is in a solid-liquid two-phase state. Based on the above selection principles, the optional phase change material 3 includes low melting point alloys, such as tin, bismuth, aluminum, silicon and other alloys, or molten salts of other components, or some sugar alcohols.

[0021] In this embodiment, the outer shell 2 is used as the shell of the molten salt electric heater as a whole, and is used to separate the phase change material 3 from the external environment. The inner shell 5 is used to separate the phase change material 3 from the molten salt, and is the main pressure-bearing shell. The cavity 8 of the inner shell 5 is the molten salt flow space. The molten salt inlet 9 and the molten salt outlet 6 are used to connect the cavity 8 with the external system, and the molten salt flows into and out of the molten salt electric heater. The junction box 1 can be set on one side of the outer shell 2, and is used to connect with the electric heating tube 7 to achieve access to an external power supply. The electric heating tube 7 is located in the inner shell 5 and is the main heating element. After power is turned on, the molten salt is heated by the Joule effect. As a result, the molten salt can be heated when it flows in the inner shell 5.

[0022] Based on the preliminary description of the above structural functions, a molten salt electric heater of this embodiment has the following working principle: under normal conditions, the phase change material 3 is in a solid-liquid two-phase state, and the heated medium, i.e., the molten salt, flows into the cavity 8 from the molten salt inlet 9, and as it flows, it fully exchanges heat with the electric heating tube 7, gradually rises to a high temperature, and finally the molten salt gathers at the molten salt outlet 6 and flows out from there. When the molten salt electric heater adjusts the frequency of the power grid, its own power rises and falls rapidly, and the molten salt flow rate or flow rate has not been timely regulated, that is, the molten salt does not flow out in time, resulting in heat accumulation, or the molten salt flows out quickly, resulting in a rapid drop in temperature, the heat released by the electric heating tube 7 will not match the temperature requirement of the molten salt. At this time, the phase change material 3 in the solid-liquid two-phase state can absorb or release heat accordingly to ensure thermal balance, and maintain the temperature of the inner shell 5 and the outer shell 2 without drastic changes, thereby reducing the temperature change rate of the shell, and playing a role in maintaining temperature balance.

[0023] It can be seen that, compared with the prior art, the molten salt electric heater of this embodiment, because it is provided with a phase change material 3, cleverly utilizes the heat storage capacity of the phase change material 3 in a solid-liquid two-phase state to achieve heat buffering, avoiding the influence of temperature changes caused by power and flow changes on the life of the molten salt electric heater, and can extend the service life. In addition, in extreme cases such as power outages, the molten salt electric heater has no heat source input, and the cold salt will have a risk of freezing and blocking. At this time, the phase change material 3 can release the heat energy stored therein to heat the molten salt, thereby avoiding freezing and blocking.

[0024] Example 2

[0025] Combined with Figure 1 Compared with the technical solution of Example 1, a molten salt electric heater of this embodiment can be improved as follows: along the direction from the molten salt inlet 9 to the molten salt outlet 6, the inner shell 5 and the outer shell 2 are divided into n sections of filling space, different phase change materials 3 are arranged in different filling spaces, and along the direction from the molten salt inlet 9 to the molten salt outlet 6, the crystallization temperature range of the phase change material 3 increases successively.

[0026] When the molten salt flows from the molten salt inlet 9 to the molten salt outlet 6, it will be gradually heated by the electric heating tube 7. Therefore, the temperature of different areas in the molten salt electric heating tube 7 is different, so the equilibrium temperature to be maintained in different areas is different. Therefore, in this embodiment, the filling space of the inner shell 5 and the outer shell 2 for filling the molten salt is divided into n sections, and different phase change materials 3 are filled in the filling spaces of different sections to adapt to the change of the molten salt temperature.

[0027] Taking the molten salt using binary salt as an example, the molten salt needs to increase the temperature from 450°C to 550°C. At this time, the filling space can be divided into three sections. The first section phase change material 3 uses aluminum-magnesium-zinc alloy with a phase change temperature of 430-470°C. The second section uses aluminum-copper alloy with a phase change temperature of about 470-520°C. The third section uses aluminum-silicon alloy with a phase change temperature of 500-550°C, so as to better maintain the temperature balance of the molten salt.

[0028] Example 3

[0029] Combined with Figure 1 Compared with the technical solutions of Embodiment 1 or 2, the molten salt electric heater of this embodiment can be improved as follows: a plurality of baffles 4 are arranged in the inner shell 5, and the baffles 4 are arranged at intervals and staggered to form a curved flow channel. A guide surface 10 is arranged at the connection between the baffle 4 and the inner shell 5.

[0030] In this embodiment, a baffle 4 is further provided, which is located in the inner shell 5 and is used to extend the flow path length of the shell-side medium such as molten salt. The staggered arrangement of the baffles 4 can increase the flow velocity of the shell-side medium and increase its turbulence level, thereby improving the heat transfer effect.

[0031] When the baffle 4 is connected to the inner shell 5, an angle is formed at the connection with the inner shell 5, and a flow dead zone is formed at the angle. In this embodiment, a guide surface 10 is provided at the angle where the dead zone is likely to be formed, so as to reduce the dead zone. It can be understood that the purpose of the guide surface 10 is to improve the fluidity, so the guide surface 10 can be an inclined surface, a curved surface, etc., to eliminate the fluidity problem.

[0032] Example 4

[0033] Combined with Figure 1 A molten salt electric heater of this embodiment, compared with any one of the technical solutions of Examples 1-3, can be improved as follows: a corrosion-resistant coating is provided on the inner wall of the outer shell 2 and the outer wall of the inner shell 5, such as a metal coating, a ceramic coating, an oxide coating such as Al2O3, Cr2O3 and SiO2, a carbide coating such as TiC, Cr3C2, and a nitride coating such as TiN, AlN, CrN.

[0034] The above schematically describes the present invention and its implementation methods, which are not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creative design without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A molten salt electric heater, characterized in that: It includes an electric heating tube, an inner shell, an outer shell, a molten salt inlet and a molten salt outlet; the molten salt inlet and the molten salt outlet are respectively close to the two ends of the outer shell and connected to the cavity of the inner shell, and the electric heating tube is located in the cavity of the inner shell; the inner shell and the outer shell are filled with phase change material.

2. A molten salt electric heater according to claim 1, characterized in that: Along the direction from the molten salt inlet to the molten salt outlet, the inner shell and the outer shell are divided into n sections of filling space, different phase change materials are arranged in different filling spaces, and the crystallization temperature range of the phase change material increases successively along the direction from the molten salt inlet to the molten salt outlet.

3. A molten salt electric heater according to claim 1, characterized in that: A plurality of baffles are arranged in the inner shell body, and the baffles are arranged at intervals and staggered to form a bending flow channel.

4. A molten salt electric heater according to claim 3, characterized in that: A flow guide surface is provided at the connection between the baffle and the inner shell.

5. A molten salt electric heater according to claim 4, characterized in that: The guide surface is an inclined surface or a curved surface.

6. A molten salt electric heater according to claim 1, characterized in that: The phase change material is an alloy, a molten salt or a sugar alcohol.

7. A molten salt electric heater according to claim 1, characterized in that: The inner wall of the outer shell and the outer wall of the inner shell are provided with a corrosion-resistant coating.

8. The molten salt electric heater according to claim 1, characterized in that: It also includes a junction box, which is electrically connected to the electric heating tube.

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