A molten salt storage tank electric heating device for enhancing heat transfer and a method of using the same

Abstract

The application discloses a molten salt storage tank electric heating device for enhancing heat transfer and a use method thereof. The molten salt storage tank electric heating device comprises a shell, a molten salt inlet, a molten salt outlet and a plurality of electric heating pipes, a shell side of the shell is divided into upper and lower parts by a shell side baffle arranged in the shell, the electric heating pipes are inserted into the shell, the molten salt inlet is connected with the inside of a molten salt storage tank through an inlet pipeline, a molten salt pump is arranged on the inlet pipeline, a molten salt adjusting valve is arranged between the molten salt pump and the molten salt inlet, the molten salt outlet is connected with the inside of the molten salt storage tank through an outlet pipeline, and a temperature measuring element is arranged on the outlet pipeline. The molten salt storage tank electric heating device utilizes three means of adding fins, molten salt external circulation and replacing intermediate heat transfer medium, enhances the heat transfer efficiency between the molten salt storage tank electric heating device and molten salt, improves the thermal stress of a contact surface between the molten salt storage tank electric heating device and the molten salt storage tank and reduces the leakage risk of the storage tank.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, and in particular to an electric heating device for molten salt storage tanks with enhanced heat transfer and its usage method. Background Technology

[0002] Molten salt thermal energy storage, as a medium-to-high temperature heat transfer and storage method, is widely used in new energy fields such as solar thermal systems, peak shaving and frequency regulation, and green electricity consumption. The electric heater in the molten salt storage tank is a key device for ensuring system stability and preventing molten salt solidification during system shutdowns; its heat exchange performance determines the long-term operational feasibility of the molten salt thermal energy storage system.

[0003] The most widely used type of heater in existing molten salt thermal storage systems is the submerged electric heater, which transfers heat from the electric heating element to the heated medium, raising its temperature to the required process temperature. However, submerged electric heaters rely on air as an intermediate medium for heat exchange, and air's low thermal conductivity reduces the overall heat transfer efficiency of the heater and increases the risk of the heating element overheating and tripping. Furthermore, submerged electric heaters require welding pipes to the bottom of the tank wall, and the significant temperature difference between the heater's outer wall and the tank wall leads to substantial thermal stress at the contact surface, increasing the risk of tank leakage. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose an electric heating device for enhancing heat transfer in a molten salt storage tank and its method of use.

[0006] On one hand, the present invention proposes an electric heating device for molten salt storage tanks to enhance heat transfer, comprising:

[0007] A shell, wherein a shell-side partition is provided inside the shell, the shell-side partition dividing the shell side of the shell into upper and lower parts;

[0008] Multiple electric heating elements are inserted inside the housing;

[0009] A molten salt inlet is located at the lower right of the shell. The molten salt inlet is connected to the inside of the molten salt storage tank through an inlet pipeline. A molten salt pump is installed on the inlet pipeline, and a molten salt regulating valve is installed between the molten salt pump and the molten salt inlet.

[0010] The molten salt outlet is located on the upper right side of the shell. The molten salt outlet is connected to the interior of the molten salt storage tank through an outlet pipeline, and a temperature measuring element is installed on the outlet pipeline.

[0011] In some embodiments, the molten salt flowing in from the molten salt inlet first flows from right to left along the wall of the electric heating tube located below the shell-side partition, then flows from left to right along the wall of the electric heating tube located above the shell-side partition, and finally flows out from the molten salt outlet into the molten salt storage tank.

[0012] In some embodiments, a plurality of ribs are uniformly arranged on the exterior of the housing.

[0013] In some embodiments, the opening degree of the molten salt regulating valve is adjusted according to the temperature of the temperature sensing element.

[0014] In some embodiments, the temperature sensing element is one of a thermocouple sensor, a bimetallic thermometer, an expansion thermometer, or a contact temperature sensor.

[0015] In some embodiments, the electric heating element is a U-shaped electric heating element.

[0016] In some embodiments, a wiring cavity is further included, wherein one end of the electric heating tube for connecting to an external wiring connection is inserted into the wiring cavity.

[0017] In some embodiments, a plurality of the electric heating devices for the molten salt storage tanks are evenly arranged around the circumference at the bottom of the molten salt storage tanks.

[0018] In some embodiments, a portion of the molten salt in the molten salt storage tank is drawn out by the molten salt pump, and the molten salt enters the electric heating device of the molten salt storage tank through the molten salt regulating valve to enhance heat exchange. After heat exchange, the molten salt returns to the molten salt storage tank from the molten salt outlet.

[0019] On the other hand, the present invention proposes a method for using an electric heating device for molten salt storage tanks that enhances heat transfer, comprising the following steps:

[0020] When the temperature of the molten salt storage tank decreases, the low-temperature molten salt in the molten salt storage tank flows through the molten salt regulating valve under the action of the molten salt pump and enters the electric heating device of the molten salt storage tank from the molten salt inlet;

[0021] Molten salt first flows from right to left along the wall of the electric heating tube located below the shell-side partition, and then flows from left to right along the wall of the electric heating tube located above the shell-side partition, exchanging heat with the electric heating tube. The molten salt after heat exchange flows out from the molten salt outlet into the molten salt storage tank.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The electric heating device for molten salt storage tank of the present invention utilizes three methods—adding fins, external circulation of molten salt, and replacing the intermediate heat exchange medium—to enhance the heat transfer efficiency between the electric heating device and the molten salt, improve the thermal stress at the contact surface between the electric heating device and the molten salt storage tank, and reduce the risk of tank leakage. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the electric heating device for enhancing heat transfer in a molten salt storage tank according to the present invention.

[0026] Figure 2 A schematic diagram showing the installation method of the electric heating device in the molten salt storage tank;

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Shell; 2. Rib; 3. Electric heating tube; 4. Shell side partition; 5. Molten salt inlet; 6. Molten salt outlet; 7. Wiring cavity; 8. Molten salt pump; 9. Molten salt regulating valve; 10. Temperature measuring element; 11. Molten salt storage tank; 12. Inlet pipeline; 13. Outlet pipeline. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The electric heating device for enhancing heat transfer in a molten salt storage tank according to an embodiment of the present invention and its method of use are described below with reference to the accompanying drawings.

[0031] like Figure 1-2 As shown, the electric heating device for enhancing heat transfer in a molten salt storage tank according to the present invention includes a shell 1, an electric heating tube 3, a shell-side partition 4, a molten salt inlet 5, a molten salt outlet 6, and a wiring cavity 7. The electric heating device for a molten salt storage tank of the present invention is used in conjunction with a molten salt storage tank 11 to heat the molten salt inside the tank 11 and prevent the molten salt from crusting.

[0032] Multiple electric heating tubes 3 are inserted inside the shell 1 of the electric heating device for the molten salt storage tank. One end of the electric heating tube 3 is inserted into the wiring cavity 7 for connecting to the outside. Inside the wiring cavity 7, the electric heating tube 3 is connected to the outside. Current flows through the resistance wire inside the electric heating tube 3 to generate heat, thereby heating the molten salt flowing through its tube wall.

[0033] In some embodiments, the electric heating element 3 is a U-shaped electric heating element. It is understood that the electric heating element 3 can also be other feasible shapes.

[0034] Multiple ribs 2 are provided on the exterior of the housing 1. Preferably, the multiple ribs 2 are evenly distributed on the exterior of the housing 1. The arrangement of the ribs 2 expands the heat exchange area on the exterior of the housing 1 and enhances heat transfer.

[0035] A shell-side baffle 4 is provided inside the shell 1. The shell-side baffle 4 divides the shell side of the shell 1 into upper and lower parts. The setting of the shell-side baffle 4 increases the shell-side flow, which increases the flow of molten salt when it flows through the shell side of the shell 1 for heat exchange, resulting in better heat exchange effect.

[0036] Molten salt inlet 5 is located at the lower right of shell 1. Molten salt inlet 5 is connected to the inside of molten salt storage tank 11 through inlet pipeline 12. Molten salt pump 8 is installed on inlet pipeline 12. Molten salt regulating valve 9 is installed between molten salt pump 8 and molten salt inlet 5.

[0037] Specifically, the molten salt inlet 5 is located at the lower right of the shell 1. The molten salt inlet 5 is connected to the molten salt storage tank 11 via an inlet pipeline 12, meaning one end of the inlet pipeline 12 connects to the molten salt inlet 5, and the other end connects to the interior of the molten salt storage tank 11. A molten salt pump 8 is installed on the inlet pipeline 12, and a molten salt regulating valve 9 is installed between the molten salt pump 8 and the molten salt inlet 5. The molten salt regulating valve 9 is used to regulate the flow rate of molten salt in the inlet pipeline 12. When it is necessary to heat the molten salt in the molten salt storage tank 11, the molten salt pump 8 is started. Under the action of the molten salt pump 8, the molten salt in the molten salt storage tank 11 flows through the molten salt regulating valve 9 and enters the molten salt storage tank electric heating device for heat exchange from the molten salt inlet 5.

[0038] Molten salt outlet 6 is located at the upper right of shell 1. Molten salt outlet 6 is connected to the inside of molten salt storage tank 11 through outlet pipeline 13. Temperature measuring element 10 is installed on outlet pipeline 13.

[0039] Specifically, the molten salt outlet 6 is located at the upper right of the shell 1. The molten salt outlet 6 is connected to the molten salt storage tank 11 via an outlet pipeline 13, meaning one end of the outlet pipeline 13 is connected to the molten salt outlet 6, and the other end is connected to the interior of the molten salt storage tank 11. A temperature sensing element 10 is installed on the outlet pipeline 13 to measure the temperature of the molten salt flowing through the outlet pipeline 13. During operation, the opening of the molten salt regulating valve 9 is adjusted according to the temperature measured by the temperature sensing element 10. When the temperature measured by the temperature sensing element 10 is high, it indicates that the heat exchange efficiency between the molten salt and the electric heating tube 3 in the electric heating device of the molten salt storage tank is high, and the temperature rises quickly. In this case, the opening of the molten salt regulating valve 9 is increased to increase the flow rate of the molten salt in the inlet pipeline 12. When the temperature measured by the temperature sensing element 10 is low, it indicates that the heat exchange efficiency between the molten salt and the electric heating tube 3 in the electric heating device of the molten salt storage tank is low, and the temperature rises slowly. In this case, the opening of the molten salt regulating valve 9 is decreased to reduce the flow rate of the molten salt in the inlet pipeline 12.

[0040] Alternatively, preferably, the end of the inlet pipeline 12 away from the molten salt inlet 5 extends into the molten salt storage tank 11 near the bottom, and the end of the outlet pipeline 13 away from the molten salt outlet 6 extends into the molten salt storage tank 11 near the top.

[0041] The temperature sensing element 10 is one of a thermocouple sensor, a bimetallic thermometer, an expansion thermometer, or a contact temperature sensor. It is understood that the temperature sensing element 10 can also be other suitable types.

[0042] Molten salt flowing in from molten salt inlet 5 first flows from right to left along the wall of electric heating tube 3 located below shell-side partition 4, then flows from left to right along the wall of electric heating tube 3 located above shell-side partition 4, and finally flows out from molten salt outlet 6 into molten salt storage tank 11.

[0043] Specifically, since the shell-side partition 4 divides the shell side of the shell 1 into upper and lower parts, when the molten salt flows in from the molten salt inlet 5, it first flows from the right side to the left side along the tube wall of the electric heating tube 3 located below the shell-side partition 4, and then flows from the left side to the right side along the tube wall of the electric heating tube 3 located above the shell-side partition 4. During the flow, the heat generated by the resistance wire in the electric heating tube 3 heats the molten salt.

[0044] When the electric heating device for the molten salt storage tank is used in conjunction with the molten salt storage tank 11, the electric heating device for the molten salt storage tank is located at the bottom of the molten salt storage tank 11. It is understood that multiple electric heating devices for the molten salt storage tank can be installed at the bottom of the molten salt storage tank 11. Preferably, multiple electric heating devices for the molten salt storage tank are evenly arranged at the bottom of the molten salt storage tank 11 along the circumference.

[0045] When heating the molten salt in the molten salt storage tank 11 using the electric heating device of the molten salt storage tank, a portion of the molten salt in the molten salt storage tank 11 is drawn out by the molten salt pump 8. The molten salt enters the electric heating device of the molten salt storage tank through the molten salt regulating valve 9 from the molten salt inlet 5 to enhance heat exchange. The molten salt after heat exchange returns to the molten salt storage tank 11 from the molten salt outlet 6.

[0046] The method of using the electric heating device for molten salt storage tank with enhanced heat transfer includes the following steps: When the temperature of molten salt storage tank 11 decreases, the low-temperature molten salt in molten salt storage tank 11 flows through molten salt regulating valve 9 and enters the electric heating device for molten salt storage tank from molten salt inlet 5 under the action of molten salt pump 8; the molten salt first flows from right to left along the tube wall of electric heating tube 3 located below shell-side partition 4, and then flows from left to right along the tube wall of electric heating tube 3 located above shell-side partition 4, exchanging heat with electric heating tube 3, and the molten salt after heat exchange flows out from molten salt outlet 6 and enters molten salt storage tank 11.

[0047] Specifically, when the temperature of the molten salt storage tank 11 decreases, the electric heating device, molten salt pump 8, and molten salt regulating valve 9 are activated. The low-temperature molten salt in the molten salt storage tank 11 is drawn out by the molten salt pump 8 and enters the electric heating device through the molten salt inlet 5. The molten salt flows from bottom to top on the shell side. First, the molten salt on the shell side flows from right to left along the wall of the electric heating tube 3 located below the shell-side partition 4, and then flows from left to right along the wall of the electric heating tube 3 located above the shell-side partition 4, exchanging heat with the electric heating tube 3. The molten salt after heat exchange flows back to the molten salt storage tank 11 from the molten salt outlet 6. Current flows through the resistance wire inside the electric heating tube 3, generating heat. This heat is transferred sequentially from the inside to the outside of the molten salt inside the electric heating device, the outer shell 1, and the molten salt inside the molten salt storage tank 11. During the heating of molten salt, the opening of the molten salt regulating valve 9 is adjusted by the temperature feedback of the temperature sensing element 10 arranged on the outlet pipeline 13, thereby controlling the flow rate of molten salt flowing through the molten salt inlet pipeline 5. When the temperature measured by the temperature sensing element 10 is high, the opening of the molten salt regulating valve 9 is increased, thereby increasing the flow rate of molten salt in the inlet pipeline 12; when the temperature measured by the temperature sensing element 10 is low, the opening of the molten salt regulating valve 9 is decreased, thereby reducing the flow rate of molten salt in the inlet pipeline 12.

[0048] The electric heating device for molten salt storage tank of the present invention uses molten salt as the intermediate heat transfer medium and replaces the heat transfer method with forced convection. Compared with natural air convection, it improves the internal heat transfer efficiency of the electric heater and reduces the risk of overheating and tripping of the electric heating tube 3. On the other hand, the ribs 2 are provided on the outside of the shell 1, which increases the internal circulation with the molten salt storage tank 11, reduces the contact temperature difference between the shell 1 and the tank wall of the molten salt storage tank 11, improves the thermal stress of the contact surface between the electric heating device body and the molten salt storage tank 11, and reduces the risk of leakage of the molten salt storage tank 11.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method of using an electric heating device for molten salt storage tank with enhanced heat transfer, characterized in that, include: A shell, wherein a shell-side partition is provided inside the shell, the shell-side partition dividing the shell side of the shell into upper and lower parts; Multiple electric heating elements are inserted inside the housing; A molten salt inlet is located at the lower right of the shell. The molten salt inlet is connected to the inside of the molten salt storage tank through an inlet pipeline. A molten salt pump is installed on the inlet pipeline, and a molten salt regulating valve is installed between the molten salt pump and the molten salt inlet. A molten salt outlet is located at the upper right of the shell. The molten salt outlet is connected to the interior of the molten salt storage tank via an outlet pipeline, and a temperature sensing element is installed on the outlet pipeline. Molten salt flowing in from the molten salt inlet first flows from right to left along the wall of the electric heating tube located below the shell-side partition, then flows from left to right along the wall of the electric heating tube located above the shell-side partition, and finally flows out from the molten salt outlet into the molten salt storage tank. The opening of the molten salt regulating valve is adjusted according to the temperature of the temperature sensing element. Multiple ribs are evenly arranged on the outside of the shell, and multiple electric heating devices for the molten salt storage tank are evenly arranged circumferentially at the bottom of the molten salt storage tank. Includes the following steps: When the temperature of the molten salt storage tank decreases, the low-temperature molten salt in the molten salt storage tank flows through the molten salt regulating valve under the action of the molten salt pump and enters the electric heating device of the molten salt storage tank from the molten salt inlet; Molten salt first flows from right to left along the wall of the electric heating tube located below the shell-side partition, and then flows from left to right along the wall of the electric heating tube located above the shell-side partition, exchanging heat with the electric heating tube. The molten salt after heat exchange flows out from the molten salt outlet into the molten salt storage tank.

2. The method as described in claim 1, characterized in that, The temperature sensing element is one of a thermocouple sensor, a bimetallic thermometer, an expansion thermometer, or a contact temperature sensor.

3. The method as described in claim 1, characterized in that, The electric heating element is a U-shaped electric heating element.

4. The method as described in claim 1, characterized in that, It also includes a wiring cavity, into which one end of the electric heating tube is inserted for connection to an external wire.

5. The method as described in claim 1, characterized in that, The molten salt pump extracts a portion of the molten salt from the molten salt storage tank. The molten salt then enters the electric heating device inside the molten salt storage tank through the molten salt regulating valve to enhance heat exchange. After heat exchange, the molten salt returns to the molten salt storage tank through the molten salt outlet.

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