A segmented electric heater

Abstract

The present invention relates to the technical field of molten salt energy storage equipment, and specifically to a segmented electric heater, comprising a low-temperature molten salt bin, a connecting bin and a high-temperature molten salt bin connected in sequence. In view of the technical problems of defects in existing molten salt heaters, the segmented electric heater of the present invention is in a downstream form as a whole. While increasing the flow rate to enhance the heating effect, it uses the connecting bin to mix the temperature and eliminate the unevenness of the molten salt heating temperature; at the same time, the connecting bin has a certain energy storage function, which can make up for the lack of heating capacity of the electric heating pipe when the equipment is cold started, and further heat the molten salt flowing through the connecting bin, so that the molten salt outlet temperature is relatively stable.

Description

Technical Field

[0001] The invention relates to the technical field of molten salt energy storage equipment, and in particular to a segmented electric heater. Background Art

[0002] Molten salt has the advantages of good heat transfer performance, high heat storage density and high heat storage temperature. As a stable and safe heat storage medium, it can be widely used in the field of heat storage and energy storage. When the load of new energy power such as wind power and photovoltaic power fluctuates, the abandoned wind and solar power can be converted into heat energy and stored through molten salt heaters to ensure the stable operation of the power grid and reduce energy waste.

[0003] The energy storage system is designed according to the above energy storage principle, and the energy storage system generally includes a molten salt heater. For a molten salt heater, under the condition of equal power, that is, equal flow, the faster the flow rate of the molten salt inside it, the better the heating effect. Therefore, downstream heating can be selected, that is, the molten salt flows along the length of the electric heating tube, and the cylinder is made more "slender" to ensure that the molten salt flows rapidly throughout the entire process and increase the heat transfer effect. However, when the fluid flows, the flow rate of the fluid close to the wall of the cylinder will be slower than the flow rate at the center due to the effect of viscosity and other factors, which will lead to a higher fluid temperature at the wall of the cylinder. Therefore, the temperature of the molten salt at the outlet will be uneven, and the selection of a slender and downstream structure will aggravate the unevenness of flow and heat transfer in this cross section. Summary of the invention

[0004] In response to the technical problems of defects in existing molten salt heaters, the present invention provides a segmented electric heater, which is in a downstream form as a whole. While increasing the flow rate to enhance the heating effect, it utilizes a connecting bin to mix the temperature and eliminate the unevenness of the molten salt heating temperature. At the same time, by utilizing the energy storage function of the connecting bin, the connecting bin can be used when the equipment is cold started.

[0005] The technical solution provided by the present invention is: a segmented electric heater, comprising a low-temperature molten salt warehouse, a connecting warehouse and a high-temperature molten salt warehouse connected in sequence; a molten salt inlet is arranged on the low-temperature molten salt warehouse, and a first electric heating pipe group is arranged in the low-temperature molten salt warehouse; a second electric heating pipe group is arranged in the high-temperature molten salt warehouse, and a partition is arranged in the high-temperature molten salt warehouse, one end of the partition is fixedly connected to the connecting warehouse to separate the high-temperature molten salt warehouse into a first baffle area and a second baffle area, and the first baffle area and the second baffle area are connected to each other away from the connecting warehouse; a solid domain is arranged in the connecting warehouse, and the upper and lower sides of the solid domain are connected A filling area is provided, in which granular fillers are piled up, and a molten salt outlet is provided on the connecting bin, and the molten salt outlet is connected with the filling area on one side; a first flow channel, a second flow channel and a third flow channel are provided in the solid domain; several inlets of the first flow channel are connected with the low-temperature molten salt bin, and the outlet of the first flow channel is connected with the inlet of the second flow channel through the filling area on one side; several outlets of the second flow channel are connected with the first baffle area, and the second baffle area is connected with several inlets of the third flow channel, and the outlet of the third flow channel is connected with the molten salt outlet through the filling area on the other side.

[0006] Optionally, any one, two or three of a first capillary channel, a second capillary channel and a third capillary channel are provided in the solid domain; the first capillary channel is connected to the first flow channel and the packing area connected to the first flow channel; the second capillary channel is connected to the second flow channel and the packing area connected to the second flow channel; the third capillary channel is connected to the third flow channel and the packing area connected to the third flow channel.

[0007] Optionally, the flow cross-sectional area of ​​each of the first baffle area and the second baffle area is smaller than the flow cross-sectional area of ​​the low-temperature molten salt warehouse.

[0008] Optionally, the first electric heating tube group and the second electric heating tube group both include a flange and a plurality of electric heating tubes, the electric heating tubes are evenly fixed on the flange, and the flange is fixedly connected to the low-temperature molten salt tank or the high-temperature molten salt tank; a plurality of pipe holes are provided on the solid domain, one end of the electric heating tube is inserted into the pipe hole, and a junction box is provided at the other end of the electric heating tube, and the junction box is electrically connected to the electric heating tube.

[0009] Optionally, there is a first gap between the bottom surface of the tube hole and the end of the electric heating tube, and / or there is a second gap between the inner wall of the tube hole and the outer wall of the electric heating tube.

[0010] Optionally, a hollow portion is provided in the solid domain, and the hollow portion is located between the first flow channel and the second flow channel, and / or between the first flow channel and the third flow channel.

[0011] Optionally, the particle size of the particle filler is larger than the size at the inlet and outlet of the first flow channel, the second flow channel and the third flow channel.

[0012] Optionally, at least one of the outlet of the first flow channel, the inlet of the second flow channel, and the outlet of the third flow channel is provided with an extension portion, the extension portion extends into the filling area and is connected with the filling area, there is at least one connecting path between the extension portion and the filling area, and the cross-sectional size of the connecting path is smaller than the particle size of the particle filler.

[0013] Optionally, the filling area is not fully filled with the particle filler, but there is surplus space to allow the particle filler to move.

[0014] Optionally, the top and the bottom of the connecting bin are provided with inclined feeding surfaces, and the inclination angle of the inclined feeding surfaces is greater than the stacking angle of the particle filler.

[0015] Beneficial Effects

[0016] The technical solution provided by the present invention has the following beneficial effects compared with the prior art: in response to the technical problems of defects in existing molten salt heaters, the segmented electric heater of the present invention is in a downstream form as a whole. While increasing the flow rate to enhance the heating effect, it uses the connecting bin to mix the temperature and eliminate the unevenness of the molten salt heating temperature; at the same time, the connecting bin has a certain energy storage function, which can make up for the insufficient heating capacity of the electric heating tube when the equipment is cold started, and further heat the molten salt flowing through the connecting bin, so that the molten salt outlet temperature is relatively stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of a segmented electric heater proposed in an embodiment of the present invention.

[0018] Figure 2 for Figure 1 A magnified schematic diagram of center A.

[0019] Figure 3 This is one of the partial structural schematic diagrams of the segmented electric heater proposed in the embodiment of the present invention.

[0020] Figure 4 This is the second schematic diagram of the partial structure of the segmented electric heater proposed in the embodiment of the present invention.

[0021] Figure 5 A schematic diagram of the molten salt flow of the segmented electric heater proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

[0023] 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 inventions, rather than to limit the invention. It should also be noted that, for the convenience of description, only the parts related to the invention are shown in the accompanying drawings. The words "first", "second", etc. described in the present invention are set for the convenience of describing the technical solution of the present invention, 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 invention. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. In the description of the present invention, 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 invention 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 of the present invention. 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 invention 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 without contradictions or conflicts, all of which are within the scope of protection required by the present invention.

[0024] Combined with Figure 1-4 This embodiment proposes a segmented electric heater, comprising a low-temperature molten salt bin 1, a connecting bin 2 and a high-temperature molten salt bin 3 connected in sequence. The low-temperature molten salt bin 1, the connecting bin 2 and the high-temperature molten salt bin 3 constitute a downstream electric heater, wherein the low-temperature molten salt bin 1 and the high-temperature molten salt bin 3 are both used to directly heat the molten salt.

[0025] The low temperature molten salt tank 1 is provided with a molten salt inlet 10, and a first electric heating pipe group 11 is provided in the low temperature molten salt tank 1. Molten salt flows in from the molten salt inlet 10 and can be heated by the first electric heating pipe group 11 in the low temperature molten salt tank 1.

[0026] A second electric heating pipe group 31 is provided in the high-temperature molten salt bin 3, and a partition 32 is provided in the high-temperature molten salt bin 3, one end of the partition 32 is fixedly connected to the connecting bin 2, so as to separate the high-temperature molten salt bin 3 into a first baffle area 33 and a second baffle area 34, and the first baffle area 33 and the second baffle area 34 are interconnected away from the connecting bin 2. When the molten salt flows into the high-temperature molten salt bin 3, it will first flow into the first baffle area 33, then bend at the baffle 32 away from the connecting bin 2, and then flow into the second baffle area 34. The presence of the partition 32 makes the actual flow cross-sectional area of ​​the molten salt in the high-temperature molten salt warehouse relatively smaller, while it is still in the form of downstream flow, thereby making the flow velocity of the molten salt in the first baffle area 33 and the second baffle area 34 faster and the heat transfer capacity stronger, which is conducive to timely taking away the heat of the second electric heating tube group 31 and preventing the second electric heating tube group 31 from overheating (the power of the second electric heating tube group 31 in the high-temperature molten salt warehouse 3 will be relatively larger, that is, it is more likely to overheat, and the fast-flowing molten salt is conducive to timely taking away its heat). In addition, the first baffle area 33 and the second baffle area 34 separated by the partition 32 also guide the molten salt to finally flow to the outlet of the filling area 21 of the connecting warehouse 2.

[0027] A solid domain 20 is provided in the connection chamber 2, and a filling area 21 is provided on the upper and lower sides of the solid domain 20, and granular fillers are accumulated in the filling area 21. The solid domain 20 is located in the core area in the middle of the connection chamber 2, and the granular fillers are accumulated in the filling area 21 at the top and bottom of the solid domain 20.

[0028] In this embodiment, the solid domain 20 preferably uses non-metallic solid materials, including but not limited to refractory bricks, concrete, etc., which are characterized by good temperature resistance, high specific heat capacity, and heat storage function. The granular fillers accumulated in the filler area 21 preferably use non-metallic granular materials, including but not limited to ceramic particles, pearl sand, etc., which are characterized by good temperature resistance and good flowability. In addition, the materials used in the solid domain 20 and the filler area 21 have good compatibility with molten salt, which can ensure that no physical and chemical changes occur during long-term operation.

[0029] The connecting bin 2 is provided with a molten salt outlet 22, which is communicated with a filling area 21 on one side. In addition, a filling port is also provided on the upper side and the lower side of the connecting bin 2 for filling and unloading the filling area 21.

[0030] In the solid region 20 of the present embodiment, a first flow channel 201 , a second flow channel 202 and a third flow channel 203 are provided in the solid region 20 for realizing the flow of the molten salt in the connecting chamber 2 .

[0031] Among them, several inlets of the first flow channel 201 are connected to the low-temperature molten salt warehouse 1, and the outlet of the first flow channel 201 is connected to the inlet of the second flow channel 202 through the filler area 21 on one side. Several outlets of the second flow channel 202 are connected to the first baffle area 33, and the second baffle area 34 is connected to several inlets of the third flow channel 203. The outlet of the third flow channel 203 is connected to the molten salt outlet 22 through the filler area 21 on the other side.

[0032] It can be understood that the particle size of the particle filler should be larger than the size of the inlet and outlet of the first flow channel 201 , the second flow channel 202 and the third flow channel 203 to prevent the particles from entering the solid domain 20 .

[0033] Based on the above structural description, one flow direction of the segmented electric heater is as shown in the attached Figure 5 As shown by the arrows in: First, the molten salt flows downstream along the extension direction of the first electric heating pipe group 11 in the low-temperature molten salt warehouse 1 to the solid domain 20. The molten salt from the low-temperature molten salt warehouse 1 flows into the first flow channel 201 located on the right side of the solid domain 20 through several inlets of the first flow channel 201, and passes through the lower filling area 21 to complete the first temperature mixing, and then flows into the second flow channel 202. The molten salt in the second flow channel 202 will continue to flow into the first baffle area 33 at the bottom of the high-temperature molten salt warehouse 3, and after being fully heated by the second electric heating pipe group 31 in the first baffle area 33, it will flow into the upper second baffle area 34, and continue to be fully heated by the second electric heating pipe group 31 in the second baffle area 34. Then the molten salt will flow through the third flow channel 203 and the filling area 21 located on the upper side. After completing the second temperature mixing in the filling area 21 located on the upper side, the molten salt will finally flow out from the molten salt outlet 22 connected to the upper filling area 21.

[0034] In addition to the above description, as attached Figure 5 In addition to the molten salt flow direction shown, it can also flow in the following direction: the molten salt from the low-temperature molten salt warehouse 1 flows into the first flow channel 201 located on the right side of the solid domain 20 through several inlets of the first flow channel 201, and completes the first temperature mixing through the upper filling area 21, and then flows into the second flow channel 202. The molten salt in the second flow channel 202 will continue to flow into the first baffle area 33 at the top of the high-temperature molten salt warehouse 3, and after being fully heated by the second electric heating pipe group 31 in the first baffle area 33, it will flow into the second baffle area 34 at the bottom, and continue to be fully heated by the second electric heating pipe group 31 in the second baffle area 34. Then the molten salt will flow through the third flow channel 203 and the filling area 21 located at the bottom. After completing the second temperature mixing in the filling area 21 located at the bottom, the molten salt will finally flow out from the molten salt outlet 22 connected to the lower filling area 21. It is understandable that the flow direction of the molten salt may be determined according to specific working conditions, and the location of the molten salt outlet 22 should be adapted to the flow direction of the molten salt.

[0035] For the connection warehouse 2, since there are several inlets of the first flow channel 201, the fluidity of the molten salt in the connection warehouse 2 can be guaranteed. At the same time, the main part and several inlets of the first flow channel 201 are distributed in the solid domain 20 of the connection warehouse 2. When the molten salt flows through the first flow channel 201, it can transfer heat to the solid domain 20 near the first flow channel 201 and the filler area 21 connected to the first flow channel 201, so as to increase the internal temperature of the connection warehouse 2 and achieve the energy storage effect. Similarly, when the molten salt flows through the second flow channel 202 and the third flow channel 203, it will also transfer heat to the solid domain 20 and the filler area 21 near the second flow channel 202 and the third flow channel 203. Therefore, based on the layout of the flow channel in the solid domain 20, the temperature of the corresponding area of ​​the connection warehouse 2 can be raised to the same temperature as the molten salt flowing there.

[0036] In any of the above-mentioned molten salt flow forms, the molten salt will flow through the filling area 21 on both sides of the connecting bin 2, and granular fillers are piled in the filling area 21. The granular fillers are, for example, spherical particles. When the molten salt flows into the filling area 21, it will flow into the pores between the granular fillers to form seepage. The molten salt fluids in all directions and with uneven cold and hot temperatures are constantly broken up and reorganized, and finally mixed into the same temperature, and the granular fillers are also heated to the salt temperature.

[0037] In this embodiment, the filling area 21 is located on the upper and lower sides of the solid domain 20. The purpose of this arrangement is that when the segmented electric heater is shut down and no molten salt flows through, the filler particles are in a stacked state and air pores naturally exist, resulting in poor overall thermal conductivity and natural heat dissipation capacity of the filling area 21. Therefore, the arrangement of the filling area 21 at the upper and lower parts of the solid domain 20 can "wrap up" the solid domain 20, thereby minimizing the area of ​​heat dissipation of the solid domain 20 to the outside and ensuring the thermal insulation of the entire connecting warehouse 2.

[0038] That is, the connecting chamber 2 can achieve the functions of temperature mixing and energy storage, and the mechanisms of temperature mixing and energy storage are as follows: (1) Temperature mixing: When the molten salt is heated along the first electric heating tube group 11 and the second electric heating tube group 31 in the low-temperature molten salt chamber 1 and the high-temperature molten salt chamber 3, due to the effects of viscosity and other factors, the molten salt flow rate in the central area is the fastest, while the molten salt flow rate close to the shell wall is slow, and the flow in the entire shell cross section is uneven, which leads to a higher molten salt temperature at the side wall, a lower molten salt temperature at the center, and an uneven outlet salt temperature. However, after the molten salt reaches the filler area 21, it will flow into the pores between the particle fillers to form seepage, and the molten salt fluids in all directions and with uneven cold and hot temperatures are continuously dispersed and reorganized (it is worth mentioning that the existence of the first flow channel 201, the second flow channel 202, and the third flow channel 203 can also disperse and reorganize the molten salt fluid), and finally mixed into the same temperature, and mixed flow occurs to make the temperature re-mixed. (2) Energy storage function: When the segmented electric heater operates normally, the molten salt will heat the solid area 20 and the filler area 21 in the connecting bin 2 to the corresponding salt temperature for energy storage. However, due to the instability of wind and solar power with segmented electric heaters, the molten salt equipment is prone to shutdown. At this time, the accumulated filler particles in the filler area 21 can play a role in heat preservation. At the next startup (the system temperature drops after shutdown, which can be regarded as a cold start), since the first electric heating tube group 11 and the second electric heating tube group 31 must heat up first after being energized, their heating of the molten salt has a certain hysteresis, so that the molten salt cannot rise to the set temperature at first. At this time, the connecting bin 2 releases the stored energy through heat exchange with the molten salt, ensuring the stability of the temperature parameters of the molten salt outlet 22, that is, it can reach or basically approach the preset required outlet temperature.

[0039] Combined with Figure 3 In a preferred embodiment, any one, two or three of the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 are provided in the solid domain 20. The first capillary channel 2041 is connected to the first flow channel 201 and the packing area 21 connected to the first flow channel 201; the second capillary channel 2042 is connected to the second flow channel 202 and the packing area 21 connected to the second flow channel 202; the third capillary channel 2043 is connected to the third flow channel 203 and the packing area 21 connected to the third flow channel 203.

[0040] In this embodiment, the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 may exist at the same time, or only one or two of them may exist. When the molten salt flows through the first flow channel 201, the second flow channel 202 and the third flow channel 203, it will diffuse into the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 at the same time, thereby increasing the contact area between the molten salt and the solid domain 20, thereby heating a larger range of the solid domain 20 more evenly to the salt temperature, thereby further strengthening the energy storage function of the connection chamber 2. In addition, in the process of the molten salt diffusing into the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 and flowing out, the temperature mixing of the molten salt will be further achieved. It can be understood that when the solid domain 20 is used to heat the molten salt flowing in after shutdown, the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 can also make the heat exchange between the molten salt and the solid domain 20 more sufficient, thereby further improving the heating efficiency of the molten salt and ensuring that the temperature of the molten salt is more uniform.

[0041] The connecting chamber 2 in this embodiment is used to provide a heat preservation effect to improve the cold start machine condition. During normal operation, the temperature of the molten salt flowing from the low-temperature molten salt chamber 1 to the connecting chamber 2 is inconsistent with the temperature of the molten salt flowing from the high-temperature molten salt chamber 3 to the connecting chamber 2. Therefore, it can be understood that if the shutdown time is too long, the temperature of the solid domain 20 in the connection area between the high-temperature molten salt chamber 3 and the connecting chamber 2 will gradually decrease due to the heat conduction inside the solid domain 20, and the temperature of the solid domain 20 in the connection area between the low-temperature molten salt chamber 1 and the connecting chamber 2 will increase. At this time, although the solid domain 20 can still use its own temperature to replenish the molten salt during the cold start machine, the temperature of the molten salt flowing from the high-temperature molten salt chamber 3 to the connecting chamber 2, that is, the outlet temperature, cannot be restored to the temperature under normal operating conditions, which in fact shortens the shutdown insulation time of the solid domain.

[0042] In order to improve the defects caused by internal heat conduction in the solid domain 20, Figure 4 An improved implementation is listed, in which a hollow portion 209 is provided in the solid domain 20, and the hollow portion 209 is located between the first flow channel 201 and the second flow channel 202, and between the first flow channel 201 and the third flow channel 203. In this implementation, the solid domain 20 is divided into a left half and a right half by the hollow portion 209, and the left and right halves of the solid domain 20 are isolated from each other. The hollow portion 209 can be regarded as a hollow structure such as a groove or a seam existing in the solid domain 20, and there is air therein. Since air is a poor heat conductor, the setting of the hollow portion 209 can delay the heat conduction between the left and right parts of the solid domain 20, so that the temperature of the solid domain 20 near the molten salt outlet 22 can still be maintained at the temperature value under normal operating conditions for a long time, thereby achieving an extension of the shutdown insulation time of the solid domain 20.

[0043] The number and arrangement of the hollow parts 209 are not limited to the following. Figure 4 The situation shown, attached Figure 4 It is shown that there is a whole hollow portion 209 in the middle of the solid domain 20 along the vertical direction. In other embodiments, there may also be other layout forms. For example, the hollow portion 209 can also constitute a segmented hollow part. The core is to isolate the heat transfer between the first flow channel 201 and the second flow channel 202 in the solid domain 20, and to isolate the heat transfer between the first flow channel 201 and the third flow channel 203 in the solid domain 20.

[0044] The hollow portion 209 is generally not connected to the filling area 21. One configuration form of the hollow portion 209 is a structure formed by partially hollowing out the solid domain 20. The molten salt in the filling area 21 generally does not flow into the hollow portion 209. It should be noted that the hollow portion 209 does not destroy the integrity of the solid domain 20, that is, the hollow portion 209 only exists in the solid domain 20 in the form of hollowing, and the hollow portion 209 does not cause the solid domain 20 to split into multiple parts, so as to avoid the filling areas 21 on both sides from being connected to each other due to the existence of the hollow portion 209.

[0045] In a preferred embodiment, the flow cross-sectional area of ​​each of the first baffle area 33 and the second baffle area 34 is smaller than the flow cross-sectional area of ​​the low-temperature molten salt bin 1. As a result, the actual flow cross-sectional area of ​​the molten salt in the high-temperature molten salt bin 3 is smaller than that of the low-temperature molten salt bin 1, so that the flow velocity of the molten salt in the first baffle area 33 and the second baffle area 34 is faster and the heat transfer capacity is stronger, which is conducive to taking away the heat of the second electric heating pipe group 31 and preventing the second electric heating pipe group 31 of the high-temperature molten salt bin 3 from overheating.

[0046] The first electric heating tube group 11 and the second electric heating tube group 31 in this embodiment are both used to directly heat the molten salt. In a preferred embodiment, the first electric heating tube group 11 and the second electric heating tube group 31 both include a flange 4 and a plurality of electric heating tubes, and the electric heating tubes are evenly fixed on the flange 4, and the flange 4 is fixedly connected to the low-temperature molten salt warehouse 1 or the high-temperature molten salt warehouse 3. A plurality of tube holes 205 are provided on the solid domain 20, one end of the electric heating tube is plugged into the tube hole 205, and a junction box 5 is provided at the other end of the electric heating tube, and the junction box 5 is electrically connected to the electric heating tube. Based on this embodiment, the tube hole 205 on the solid domain 20 can be inserted with the electric heating tube to provide support for the electric heating tube, and the fixed connection between the flange 4 and the low-temperature molten salt warehouse 1 or the high-temperature molten salt warehouse 3 can realize the rapid assembly of the first electric heating tube group 11 and the second electric heating tube group 31. When the first electric heating tube group 11 and the second electric heating tube group 31 need to be repaired, the flange 4 can be directly removed, and the electric heating tube can be pulled out as a whole to achieve rapid repair.

[0047] Combined with Figure 2In a further embodiment, there is a first gap 206 between the bottom surface of the tube hole 205 and the end of the electric heating tube. The electric heating tube is not completely inserted to the bottom, but a certain space is left between the electric heating tube and the side wall. When the segmented electric heater is running at high temperature, the electric heating tube will generate axial thermal expansion after being heated and will extend into the tube hole 205. The first gap 206 can be used as a remaining margin space to cope with this extension, thereby avoiding damage to the electric heating tube.

[0048] And, combined with the Figure 2 In another embodiment, the diameter of the tube hole 205 is larger than the diameter of the electric heating tube, so that there is a second gap 207 between the inner wall of the tube hole 205 and the outer wall of the electric heating tube. In this embodiment, the diameter of the tube hole 205 is designed to be slightly larger than the diameter of the electric heating tube, and a certain matching gap, i.e., the second gap 207, is left between the two in the circumferential direction to accommodate thermal expansion and contraction or circumferential movement of the electric heating tube.

[0049] It should be noted that the first gap 206 and the second gap 207 described in the aforementioned embodiment refer to the gap between the electric heating tube and the tube hole 205 when the electric heating tube is not started. When the electric heating tube is working, due to the axial and radial thermal expansion of the electric heating tube, the first gap 206 and the second gap 207 will shrink or may be completely filled.

[0050] The design of the above-mentioned tube hole 205, and the design of the first gap 206 and the second gap 207, enable the solid domain 20 to serve as a support for the electric heating tube and form a soft connection with the electric heating tube, eliminating traditional connection structures such as tube sheet baffles, making the maintenance of the electric heating tube quick and convenient, and at the same time avoiding the problem of cracking caused by molten salt freezing at the traditional connection structure.

[0051] Combined with Figure 3 In other embodiments, at least one of the outlet of the first flow channel 201, the inlet of the second flow channel 202, and the outlet of the third flow channel 203 is provided with an extension 208, the extension 208 extends into the filler area 21 and is connected to the filler area 21, there is at least one connecting path between the extension 208 and the filler area 21, and the cross-sectional size of the connecting path is smaller than the particle size of the particle filler. The extension 208 can be a metal mesh structure, the mesh of the metal mesh is the connecting path between the extension 208 and the filler area 21, there are multiple meshes, and the size of the mesh is smaller than the particle size of the particle filler. Obviously, it is difficult for the particle filler to simultaneously close all the meshes on the metal mesh, thereby ensuring the flowability of the first flow channel 201, the second flow channel 202, and the third flow channel 203.

[0052] Furthermore, the extension 208 can also be a pipe structure, but the pipe structure is densely covered with through holes, which are the communication paths between the extension 208 and the filler area 21. There are multiple through holes, and the size of the through holes is smaller than the particle size of the particle filler. Obviously, it is difficult for the particle filler to simultaneously close all the through holes on the pipe structure, thereby ensuring the fluidity of the first flow channel 201, the second flow channel 202, and the third flow channel 203. Furthermore, the pipe structure can be bent, curved, and lengthened as appropriate, so that there are always a number of through holes on the pipe structure that cannot be closed by the particle filler, thereby effectively ensuring the fluidity of the first flow channel 201, the second flow channel 202, and the third flow channel 203.

[0053] Or in another preferred embodiment, the filling area 21 is not filled with granular fillers, but there is a surplus space that allows the granular fillers to move. That is, the filling area 21 is not completely filled with granular fillers, and there is still a certain amount of space, so that the granular fillers can be pushed away when disturbed by the impact of the molten salt. The surplus space is the redundant activity space of the granular fillers, so that the molten salt can rely on the kinetic energy in the flow process to push away the granular fillers at the inlets and outlets of the first flow channel 201, the second flow channel 202 and the third flow channel 203 to avoid blockage.

[0054] In addition, regarding the structure of the connecting bin 2, in a preferred embodiment, the top and bottom of the connecting bin 2 are provided with inclined discharge surfaces, and the inclination angle of the inclined discharge surface is greater than the accumulation angle of the particle filler. Therefore, when the particle filler is discharged by its own gravity, the particle filler can slide down the inclined discharge surface naturally to achieve discharge, and is not prone to obstruction, which can make the discharge cleaner and more thorough.

[0055] In summary, in view of the technical problems of defects in existing molten salt heaters, the segmented electric heater of this embodiment has the following advantages: the segmented electric heater of the present invention is in a downstream form as a whole, and while increasing the flow rate and enhancing the heating effect, the connection chamber 2 is used for temperature mixing to eliminate the unevenness of the molten salt heating temperature. At the same time, the connection chamber 2 has a certain energy storage function, which can make up for the lack of heating capacity of the electric heating pipe when the equipment is cold started, and further heat the molten salt flowing through the connection chamber 2, so that the temperature of the molten salt outlet 22 is relatively stable.

[0056] Based on the above embodiment, a working example of a segmented electric heater is given here. In this working example, the filler in the connecting bin 2 of the segmented electric heater uses ceramic particles with a particle size of 6 to 8 mm. The physical property test shows that the stacking angle is 30°. Therefore, the inclination angles of the inclined feeding surfaces at the top and bottom of the connecting bin 2 are designed to be 35°, and the inner diameters of the first flow channel 201, the second flow channel 202 and the third flow channel 203 in the solid domain 20 are designed to be 5 mm, and the inner diameters of the first capillary channel 2041, the second capillary channel 2042 and the third capillary channel 2043 are designed to be 2 to 3 mm.

[0057] The working examples are divided into "stable operating conditions" and "start-up conditions when wind and solar power fluctuate" to illustrate the operation of the segmented electric heater.

[0058] 1. Stable operating conditions:

[0059] 1) The junction box 5 is powered on, and the electric heating tube begins to generate Joule heating. At this time, 300°C low-temperature molten salt flows into the low-temperature molten salt bin 1 from the molten salt inlet 10, and then begins to be heated downstream along the first electric heating tube group 11. Due to the effects of viscosity and other factors, the flow rate of the molten salt close to the bin wall will be lower than the flow rate in the central area, resulting in uneven heating of the molten salt. The overall average temperature of the molten salt flowing into the connecting bin 2 at the end of the low-temperature molten salt bin 1 is about 400°C, but the salt temperature in each area is uneven.

[0060] 2) After the molten salt with an average temperature of 400°C enters the connecting chamber 2, it first passes through the first flow channel 201 of the solid domain 20 on the right side, then diffuses into the first capillary channel 2041, and exchanges heat with the solid domain 20. Under stable operation, the solid domain 20 near the first flow channel 201 and the first capillary channel 2041 is also gradually heated to the salt temperature (about 400°C).

[0061] 3) The molten salt continues to flow, and after leaving the solid domain 20 on the right, it enters the filler area 21 located at the bottom of the connecting chamber 2, flows into the pores between the particle fillers to form seepage, so that the uneven cold and hot salt temperatures are mixed to the same temperature (about 400°C), and flows into the solid domain 20 on the lower left side of the connecting chamber 2 through the second flow channel 202 and the second capillary channel 2042; under stable operation, the filler area 21 and the solid domain 20 near the second flow channel 202 and the second capillary channel 2042 are heated as a whole to about 400°C.

[0062] 4) Then, the molten salt flows into the high-temperature molten salt tank 3 through several outlets of the second flow channel 202, and is first heated in the lower cavity of the high-temperature molten salt tank 3, i.e., the first baffle area 33, and then baffled into the upper cavity, i.e., the second baffle area 34. After being heated by the second electric heating tube group 31, the overall temperature of the molten salt reaches about 550°C but is uneven. Then, the molten salt flows into the solid domain 20 on the upper left side through the third flow channel 203 and the third capillary channel 2043, and heats the solid domain 20 near the third flow channel 203 and the third capillary channel 2043 to about 550°C.

[0063] 5) The molten salt then enters the packing area 21 at the top of the connecting bin 2 for temperature mixing, and finally the molten salt with a uniform temperature of 550°C flows out of the segmented electric heater from the molten salt outlet 22.

[0064] 6) Under stable operating conditions, the solid domain 20 on the right half and the solid domain 20 on the lower left half are maintained at 400°C following the molten salt, while the solid domain on the upper left half is maintained at 550°C.

[0065] 2. Start-up conditions when wind and solar power fluctuate (taking startup within 2 hours after shutdown as an example):

[0066] 1) Within 2 hours after shutdown, the segmented electric heater was powered on again, and the cooled first electric heating tube group 11 started to heat again. However, due to the inertia (i.e., hysteresis) of heating, the electric heating tube did not initially rise to the temperature of stable operation. At this time, the molten salt at the end of the low-temperature molten salt tank 1 rose to about 370°C, which was lower than the rated operating temperature of 400°C.

[0067] 2) Then the 370℃ molten salt enters the connecting chamber 2, and after being heated and mixed by the 400℃ solid domain 20 on the right half and the lower left half and the bottom filler area 21, it finally rises to nearly 400℃; during the startup stage, the molten salt gradually utilizes the residual heat in the connecting chamber 2 from right to left, forming a temperature gradient, namely an inclined temperature layer, which is conducive to stable heat exchange.

[0068] 3) After leaving the solid domain 20, it is heated by the high-temperature molten salt tank 3 again. Similarly, due to the inertia of heating (i.e., hysteresis), the electric heating tube does not initially rise to the temperature of stable operation. The salt temperature rises to about 520°C at the end of the high-temperature molten salt tank 3, which is lower than the rated operating temperature of 550°C. Then, it enters the solid domain 20 at 550°C on the upper left side and the top filling area 21 again. After heating and mixing, the salt temperature will further rise to about 550°C of the rated operating condition.

[0069] The above process needs to last for about 15 minutes as the startup condition, until the segmented electric heater can reach the state of normal stable operation, and the connection chamber 2 completes the energy release function. During this period, the stability of the temperature parameters of the molten salt outlet 22 is guaranteed.

[0070] It is understandable that when the shutdown time exceeds 2 hours, the solid domain 20 will gradually decrease from 550°C at the time of shutdown to below 520°C due to the internal heat conduction of the solid domain 20. Correspondingly, the temperature of the remaining solid area 20 will rise by more than 400°C. Therefore, although the solid domain 20 on the upper left side cannot replenish the outlet molten salt from 520°C to 550°C at this time, the solid domain 20 as a whole still has the function of replenishing the molten salt when the machine is started in a cold state.

[0071] Here is an example of an improved working example to delay the process of heat conduction inside the solid domain 20: Figure 4As shown, the solid domain 20 is divided into a left half and a right half by the hollow portion 209. The left and right halves of the solid domain 20 are separated from each other by a certain distance and are not in direct contact. Since air is a poor heat conductor, the setting of the hollow portion 209 can delay the heat conduction between the left and right parts of the solid domain 20. Then, the temperature of the solid domain 20 near the molten salt outlet 22 can still be maintained at the temperature value under normal operating conditions for a long time, thereby extending the shutdown insulation time of the solid domain 20. Taking the aforementioned working example as a reference, the "start-up condition during wind and photovoltaic fluctuations" can be delayed from starting within 2 hours after shutdown to about 4 hours.

[0072] In addition, for any working example, the power of the electric heating tube, especially the power of the electric heating tube in the upper cavity of the high-temperature molten salt tank 3, that is, the second baffle area 34, can be increased within a period of time before the planned shutdown, so that the temperature of the local solid domain 20 near the third flow channel 203 exceeds 550°C, for example, 580°C, thereby further extending the insulation time and improving the energy replenishment effect.

[0073] The present invention and its embodiments are described schematically above, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and creatively designs a structure and an embodiment similar to the technical solution without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A segmented electric heater, characterized in that: It comprises a low-temperature molten salt tank (1), a connecting tank (2) and a high-temperature molten salt tank (3) which are connected in sequence, wherein the low-temperature molten salt tank (1), the connecting tank (2) and the high-temperature molten salt tank (3) constitute a downstream electric heater; The low-temperature molten salt bin (1) is provided with a molten salt inlet (10), and the low-temperature molten salt bin (1) is provided with a first electric heating pipe group (11); A second electric heating pipe group (31) is arranged in the high-temperature molten salt bin (3), and a partition (32) is arranged in the high-temperature molten salt bin (3), one end of the partition (32) is fixedly connected to the connecting bin (2) so as to separate the high-temperature molten salt bin (3) into a first baffle area (33) and a second baffle area (34), and the first baffle area (33) and the second baffle area (34) are connected to each other at a location away from the connecting bin (2); A solid domain (20) is provided in the connection bin (2), a filler area (21) is provided on the upper side and the lower side of the solid domain (20), granular fillers are piled in the filler area (21), a molten salt outlet (22) is provided on the connection bin (2), and the molten salt outlet (22) is connected to the filler area (21) on one side; the molten salt flows in the low-temperature molten salt bin (1) along the extension direction of the first electric heating pipe group (11) and flows toward the solid domain (20); A first flow channel (201), a second flow channel (202) and a third flow channel (203) are provided in the solid region (20); A plurality of inlets of the first flow channel (201) are in communication with the low-temperature molten salt container (1), and an outlet of the first flow channel (201) is in communication with an inlet of the second flow channel (202) via the filler area (21) on one side; Several outlets of the second flow channel (202) are connected to the first deflection area (33), the second deflection area (34) is connected to several inlets of the third flow channel (203), and the outlet of the third flow channel (203) is connected to the molten salt outlet (22) through the filler area (21) on the other side.

2. A sectional electric heater according to claim 1, characterized in that: Any one, two or three of the first capillary channel (2041), the second capillary channel (2042) and the third capillary channel (2043) are provided in the solid domain (20); The first capillary channel (2041) is in communication with the first flow channel (201) and the filler area (21) in communication with the first flow channel (201); The second capillary channel (2042) is in communication with the second flow channel (202) and the filler area (21) in communication with the second flow channel (202); The third capillary channel (2043) is connected to the third flow channel (203) and the filling area (21) connected to the third flow channel (203).

3. A sectional electric heater according to claim 1, characterized in that: The flow cross-sectional area of ​​each of the first baffle area (33) and the second baffle area (34) is smaller than the flow cross-sectional area of ​​the low-temperature molten salt warehouse (1).

4. A sectional electric heater according to claim 1, characterized in that: The first electric heating tube group (11) and the second electric heating tube group (31) both comprise a flange (4) and a plurality of electric heating tubes, the electric heating tubes being evenly fixed on the flange (4), and the flange (4) being fixedly connected to the low-temperature molten salt tank (1) or the high-temperature molten salt tank (3); A plurality of tube holes (205) are provided on the solid domain (20), one end of the electric heating tube is inserted into the tube hole (205), and a junction box (5) is provided at the other end of the electric heating tube, and the junction box (5) is electrically connected to the electric heating tube.

5. A sectional electric heater according to claim 4, characterized in that: There is a first gap (206) between the bottom surface of the tube hole (205) and the end of the electric heating tube, and / or there is a second gap (207) between the inner wall of the tube hole (205) and the outer wall of the electric heating tube.

6. A sectional electric heater according to claim 1, characterized in that: A hollow portion (209) is provided in the solid domain (20), and the hollow portion (209) is located between the first flow channel (201) and the second flow channel (202), and / or between the first flow channel (201) and the third flow channel (203).

7. A sectional electric heater according to claim 1, characterized in that: The particle size of the particle filler is larger than the sizes at the inlet and outlet of the first flow channel (201), the second flow channel (202) and the third flow channel (203).

8. A sectional electric heater according to claim 1, characterized in that: An extension portion (208) is provided at at least one of the outlet of the first flow channel (201), the inlet of the second flow channel (202), and the outlet of the third flow channel (203); the extension portion (208) extends into the filler area (21) and is connected to the filler area (21); there is at least one connecting path between the extension portion (208) and the filler area (21), and the cross-sectional size of the connecting path is smaller than the particle size of the particle filler.

9. A sectional electric heater according to claim 1, characterized in that: The filling area (21) is not filled with the particle filler, but has surplus space to allow the particle filler to move.

10. A sectional electric heater according to any one of claims 1 to 9, characterized in that: The top and bottom of the connection bin (2) are provided with inclined feeding surfaces, and the inclination angle of the inclined feeding surfaces is greater than the stacking angle of the particle filler.

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