CN109506505B

CN109506505B - Heat pipe with optimized distance design

Info

Publication number: CN109506505B
Application number: CN201811388097.2A
Authority: CN
Inventors: 赵炜; 徐建军
Original assignee: Qingdao Jiyunder And Commercial Trade Co Ltd
Current assignee: Taida textile Taizhou Co., Ltd
Priority date: 2016-07-29
Filing date: 2016-07-29
Publication date: 2020-03-17
Anticipated expiration: 2036-07-29
Also published as: CN107664449A; CN107664449B; CN109506505A

Abstract

The invention provides a heat pipe which comprises a lower pipe box, an upper pipe box, a heat exchange pipe bundle and a return pipe, wherein the heat exchange pipe bundle is communicated with the lower pipe box and the upper pipe box; the return pipe is connected with the positions of the end parts of the two sides of the lower pipe box and the upper pipe box, and the lower pipe box is provided with an electric heating device; the distance from the center of the upper tube box is L, the distance between adjacent heat exchange tubes is M, and then M is S (L), so that the following requirements are met: s' (L) > 0. Through the preferred arrangement, the heat exchange efficiency can be further improved, and the uniformity of heat distribution of heat exchange is increased.

Description

Heat pipe with optimized distance design

Technical Field

The invention belongs to the field of heat pipes, and particularly relates to a coil pipe heat pipe.

Background

The heat pipe technology is a heat transfer element called a heat pipe invented by George Grover (George Grover) of national laboratory of Los Alamos (Los Alamos) in 1963, fully utilizes the heat conduction principle and the rapid heat transfer property of a phase change medium, quickly transfers the heat of a heating object to the outside of a heat source through the heat pipe, and the heat conduction capability of the heat transfer element exceeds the heat conduction capability of any known metal.

The heat pipe technology is widely applied to the industries of aerospace, military industry and the like, and since the heat pipe technology is introduced into the radiator manufacturing industry, the design idea of the traditional radiator is changed for people, the single heat radiation mode that a high-air-volume motor is used for obtaining a better heat radiation effect is avoided, the heat pipe technology is adopted for enabling the radiator to obtain a satisfactory heat exchange effect, and a new place in the heat radiation industry is opened up. At present, the heat pipe is widely applied to various heat exchange devices, including the field of nuclear power, such as the utilization of waste heat of nuclear power.

The heat pipe in the prior art is in a static state in the heat exchange process, only depends on the heat dissipation of the condensation end of the heat pipe, and the improvement of a plurality of inventions is only the improvement of the structure of the enhanced heat transfer of the condensation end. On the other hand, in the prior art, different heating powers are not adopted for different positions of the heat pipe, so that the efficiency of the heat pipe is low.

Aiming at the problems, the invention provides a novel heat pipe, thereby solving the problems of low heat exchange coefficient and uneven heat exchange under the condition of heat exchange of the heat pipe.

Disclosure of Invention

The present invention provides a new heat pipe to solve the above-mentioned technical problems.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a heat pipe comprises a lower pipe box, an upper pipe box, a heat exchange pipe bundle and a return pipe, wherein the heat exchange pipe bundle is communicated with the lower pipe box and the upper pipe box, the lower pipe box is an evaporation end, a condensation end comprises the upper pipe box, fluid is subjected to heat absorption and evaporation in the lower pipe box and is condensed in the upper pipe box, and the condensed fluid returns to the lower pipe box through the return pipe; the return pipe is connected with the positions of the end parts of the two sides of the lower pipe box and the upper pipe box, and the lower pipe box is provided with an electric heating device; the electric heating device is divided into a plurality of sections, and different sections adopt different heating powers.

Preferably, the heating power of the electric heating devices of different sections is continuously reduced from the middle part of the lower pipe box to two ends of the lower pipe box.

Preferably, the heat generating power of the electric heating devices in different sections is continuously reduced to a greater extent from the middle of the lower pipe box 1 to the two ends of the lower pipe box.

Preferably, the electric heating device is an electric heating rod.

Preferably, the electric heating means is located at a position between the middle position and the bottom of the lower header.

Preferably, the heat exchange tube bundle is a coil, each coil comprises a plurality of arc-shaped heat exchange tubes, the end parts of the adjacent heat exchange tubes are communicated, the plurality of heat exchange tubes form a serial structure, and the end parts of the heat exchange tubes form free ends of the heat exchange tubes

Preferably, the distance between the center line of the electric heating device and the center line of the lower tube box is 1/4-1/3 of the inner radius of the lower tube box.

Preferably, the central lines of the plurality of circular arc-shaped heat exchange tubes are circular arcs of concentric circles.

Preferably, the concentric circles are circles centered on the center of the cross section of the upper header.

Preferably, the number of the coil pipes is multiple, and the multiple coil pipes are in a parallel structure.

Preferably, the lower tube box has an inner diameter of R1, the upper tube box has an inner diameter of R2, the heat exchange tubes have an outer diameter of D, and the distance between the center lines of the adjacent heat exchange tubes is L, so that the following relationships are satisfied:

10 (R1/R2) = a-b Ln (5D/L), where Ln is a logarithmic function, a, b are coefficients,

wherein 17.03< a <18.12,9.15< b < 10.11;

55mm<R1<100mm；95mm<R2<145mm；

25mm<D<80mm；40mm<L<120mm；

0.45<R1/R2<0.88；

0.5<D/L<0.7。

preferably, a =17.54 and b = 9.68.

Preferably, the return pipe connects both side end portions of the lower header tank and the upper header tank.

Preferably, the pipe diameter of the lower pipe box is smaller than that of the upper pipe box.

Preferably, the inner diameter of the lower tube box is R1, and the inner diameter of the upper tube box is R2, so that 0.45< R1/R2< 0.88.

Preferably, the distance between the adjacent heat exchange tubes becomes larger as it becomes farther from the center of the lower header.

Compared with the prior art, the plate heat exchanger and the heat exchange pipe wall thereof have the following advantages:

1) the heating efficiency is further improved and the heat exchange efficiency of the heat pipe is improved by the change of the segmented heating power of the electric heating rod.

2) Through setting up controlling means for can satisfy actual need more in the use of heat pipe, the user can control the application temperature of heat pipe as required, has avoided the overheated or the supercooling phenomenon that traditional heat pipe's unable fine temperature control produced, has further realized the automation of heat pipe equipment and the extensive of application.

3) The invention provides a novel electric heating heat pipe, which is characterized in that an electric heating device is arranged in the heat pipe, and heat exchange is carried out by utilizing electric energy, so that the single application range of the traditional heat pipe and the limitation of a heat source are avoided, the application field of the heat pipe is wider, the purposes of environmental protection and energy saving can be achieved, and the utilization efficiency of the heat pipe is improved.

4) The invention provides a coil pipe type heat pipe structure for the first time, and through the arrangement of the coil pipe, the heat exchange fluid can generate volume expansion after being heated, and the free end of the coil pipe is induced to generate vibration. Thereby causing the surrounding fluid to form further turbulent flow and further enhancing heat transfer.

5) The invention further improves the heat exchange effect of the heat pipe by setting the pipe diameter of the heat exchange pipe of the coil pipe and the distance change of the pipe interval from the central line of the lower pipe box.

6) The invention optimizes the optimal relationship of the parameters of the heat pipe through a large number of tests, thereby further improving the heat exchange efficiency.

Drawings

Fig. 1 is a schematic front view of a heat pipe apparatus.

Fig. 2 is a cross-sectional view a-a in fig. 1.

Fig. 3 is a dimensional schematic of the structure of fig. 2.

Fig. 4 is a schematic structural view of the arrangement of the electric heating apparatus of fig. 1.

Fig. 5 is a schematic diagram of the optimized structure in fig. 4.

Fig. 6 is a schematic view of the structure of an electric heating apparatus in a parabolic cross-sectional shape.

In the figure: 1. the device comprises a lower pipe box 2, an upper pipe box 3, a coil pipe 4, a heat exchange pipe 5, a return pipe 6, a free end 7, a free end 8, an electric heating device 9, a vacuumizing device 10 and a power supply.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings.

In this document, "/" denotes division and "×", "denotes multiplication, referring to formulas, if not specifically stated.

It is an object of the present invention to provide an electrically heated heat pipe, such as shown in fig. 4-6.

A heat pipe comprises a lower pipe box 1, an upper pipe box 2, a heat exchange pipe bundle and a return pipe 5, wherein the heat exchange pipe bundle is communicated with the lower pipe box 1 and the upper pipe box 2, the lower pipe box 1 is an evaporation end, the condensation end comprises the upper pipe box 2, fluid is subjected to heat absorption evaporation in the lower pipe box 1 and is condensed in the upper pipe box 2, and the condensed fluid returns to the lower pipe box 1 through the return pipe; the return pipe is connected with the end parts of the two sides of the lower pipe box 1 and the upper pipe box 2, and an electric heating device 8 is arranged in the lower pipe box 1; the heat pipe also includes a temperature control system for controlling the temperature of the vapor within the heat pipe.

The lower tube box 1, the upper tube box 2 and the heat exchange tube bundle of the heat pipe form a channel for fluid circulation. The upper pipe box 2 is provided with a vacuumizing pipe 9, the vacuum pump vacuumizes the inner cavities of the lower pipe box 1, the upper pipe box 2 and the heat exchange pipe bundle through the vacuumizing port pipe 9, then a proper amount of heat transfer fluid is filled through the vacuumizing pipe 9, and the heat transfer fluid finally flows into the lower pipe box 1. And after the injection amount of the thermal fluid to be transmitted reaches the standard capacity, sealing the vacuumizing tube 9.

Preferably, the lower header 1 is provided with an electric heater 8, and the fluid in the lower header 1 is heated by the electric heater 8. The fluid absorbs electric heat to evaporate in the lower pipe box 1, after heat exchange is carried out between at least one part of the coil pipe 3 and the upper pipe box 2, the fluid is condensed in the upper pipe box 2, and the condensed fluid returns to the lower pipe box 1 through the return pipe 5.

Preferably, the electrical heating means 8 are preferably circular in cross-section.

Preferably, the electric heating means 8 is an electric heating rod.

Preferably, the electric heating device 8 is located below the middle position of the lower tube box 1, i.e. between the middle position and the bottom of the lower tube box.

Preferably, the distance between the center line of the electric heater 8 and the center line of the lower tube box is 1/4-1/3 of the inner radius of the lower tube box 1.

Experiments show that the position can achieve the optimal heating effect, so that the optimal heat exchange effect is achieved.

Preferably, the heat pipe further comprises a temperature control system for controlling the temperature of the vapour within the heat pipe. And a temperature sensor is arranged in the heat exchange tube bundle and is used for measuring the temperature of steam generated in the coil. The heating rod is electrified for heating, and the heated fluid is rapidly atomized in a vacuum state and is filled in each heat exchange tube bundle, the upper tube box 2 and the lower tube box 1. When the temperature measured by the temperature sensor reaches a preset first temperature, the temperature controller controls the heating device to stop heating, and when the temperature measured by the temperature sensor is lower than a preset second temperature, the temperature controller controls the heating rod to heat.

Preferably, the first temperature and the second temperature are the same.

Preferably, the first temperature is 5-20 degrees celsius higher than the second temperature. Preferably 8-13 degrees celsius.

Preferably, the electric heating device 8 continuously reduces the heat generation power from the middle part (e.g. M position in fig. 5) of the lower pipe box 1 to the two ends (e.g. E, F position in fig. 5) of the lower pipe box. Namely, the heating power of the middle part of the electric heating device 8 is the highest, and the heating power of the two ends is the lowest.

Preferably, the heat generation power of the electric heating device is continuously reduced from the middle part of the lower pipe box 1 to the two ends of the lower pipe box to be larger and larger.

Through the optimized design, the heat exchange efficiency can be further improved. Through the experiment discovery, can improve heat exchange efficiency through above-mentioned setting.

Preferably, the electric heating device 8 is divided into a plurality of sections, and the heat generation power of the electric heating devices of the different sections is continuously reduced from the middle part (for example, M position in fig. 5) of the lower pipe box 1 to the two ends (for example, E, F position in fig. 5) of the lower pipe box. Namely, the heating power of the middle part of the electric heating device 8 is the highest, and the heating power of the two ends is the lowest.

Preferably, the heat generating power of the electric heating devices in different sections is continuously reduced to a greater extent from the middle of the lower pipe box 1 to the two ends of the lower pipe box 1.

Through the optimized design, on one hand, the processing is convenient, and the heat exchange efficiency can be further improved. Experiments show that the heat exchange efficiency can be improved by about 15% by the arrangement.

Fig. 5 shows a structure in which the electric heating device 8 is divided into a plurality of segments. Different heating powers are used for different sections.

The electric heating device adopts a resistance heating mode.

Preferably, the electric heating device is a rod-shaped resistor. Preferably, the number is one or more.

Preferably, the electric heating device is a resistance wire. Preferably, the number is one or more.

Preferably, the electric heating device (preferably one or more rod-shaped resistors or one or more resistance wires) has an increasingly larger outer diameter from the middle of the lower pipe box 1 to two ends of the lower pipe box, i.e. the electric heating device is increasingly thicker. Namely, the middle part of the electric heating device is the thinnest, and the two ends are the thickest. For example, as shown in fig. 5 and 6, by the above-mentioned optimized arrangement, the heating powers of different positions of the electric heating device are different, thereby improving the efficiency of electric heating.

Preferably, the outer diameter of the electric heating device is increased from the middle of the lower pipe box 1 to both ends of the lower pipe box.

By adopting the change of the outer diameter, the resistance in the middle is the largest, the heating rate is the largest, the fluid is evaporated, the heating rate is gradually reduced towards the two ends, and the cold fluid flows down from the two ends, so that the heat exchange efficiency of the heat pipe is improved.

Experiments show that the optimal arrangement enables the utilization efficiency of electric heating to be highest, enables the heat pipe to achieve the best electric heating utilization efficiency, and can improve the heat utilization rate by about 10%.

Preferably, the external shape of the electric heating device is parabolic, as shown in fig. 6.

Preferably, the fluid is water.

Further preferably, the heat exchange tube bundle is a coil, and the description of the heat pipe with the coil is as follows:

as shown in fig. 1, the heat pipe includes a lower tube box 1, an upper tube box 2, a coil 3 and a return pipe 5, the coil 3 is communicated with the lower tube box 1 and the upper tube box 2, the lower tube box 1 is an evaporation end, the condensation end includes the upper tube box 2 and at least a part of the coil 3, the fluid is evaporated by heat absorption in the lower tube box 1, and after heat exchange is performed between at least a part of the coil 3 and the upper tube box 2, the fluid is condensed in the upper tube box 2, and the condensed fluid returns to the lower tube box 1 through the return pipe 5.

Preferably, the coil 3 is one or more, for example, fig. 1 illustrates a plurality of coils 3.

As shown in fig. 1, the upper header 2 is positioned at an upper portion of the lower header 1.

As shown in fig. 2, each coil 3 comprises a plurality of heat exchange tubes 4 of circular arc shape, the ends of adjacent heat exchange tubes 4 are communicated, the plurality of heat exchange tubes 4 are formed into a serial structure, and the ends of the heat exchange tubes 4 are formed into tube free ends 6, 7.

When the heat pipe works, the heat pipe exchanges heat with other fluids through the upper pipe box 2 and the coil 3. Other fluids may exchange heat with only a portion of the coil 3, e.g. the portion of the coil 3 in fig. 2 connected to the lower header 1 does not participate in the heat exchange.

Preferably, the part not participating in heat exchange is an adiabatic end. That is, the heat pipe includes an evaporation end, a condensation end and a heat insulation end, wherein the evaporation end is the lower pipe box 1, the heat insulation end is a part of the coil 3 connected with the lower pipe box 1, and the rest part is the condensation end.

Preferably, the lower header 1 is used only as the evaporation end, the upper header 2 and the coil are used as the condensation end, and there is no adiabatic end.

The invention provides a heat pipe with a novel structure.A coil pipe is arranged, heat exchange fluid can expand in volume after being heated, so that steam is formed, and the volume of the steam is far greater than that of water, so that the formed steam can flow in the coil pipe in a rapid impact manner. Because of volume expansion and steam flowing, the free ends 6 and 7 of the coil 1 can be induced to vibrate, the vibration is transmitted to the surrounding heat exchange fluid by the free ends 6 and 7 of the heat exchange tubes in the vibrating process, and the fluid can also generate disturbance with each other, so that the surrounding heat exchange fluid forms disturbed flow, a boundary layer is damaged, and the purpose of enhancing heat transfer is achieved.

Experiments show that compared with the heat pipe which is always in a standing state in the prior art, the heat exchange efficiency is improved by 25-35%.

Preferably, the lower header 1, the upper header 2, and the coil 3 are all of a circular tube structure.

Preferably, the return pipe 5 connects both side ends of the lower header 1 and the upper header 2. Therefore, the flow path of the fluid in the upper tube box 2 is ensured to be long, the heat exchange time can be further prolonged, and the heat exchange efficiency is improved.

Preferably, the heat exchange tube 4 is a flexible heat exchange tube. The heat exchange tube 4 is provided with the elastic heat exchange tube, so that the turbulent flow of the free end can be further increased, and the heat exchange coefficient can be further improved.

Preferably, the center lines of the plurality of circular arc-shaped heat exchange tubes 4 are circular arcs of concentric circles.

Preferably, the concentric circles are circles centered around the center of the upper header 2. I.e., the heat exchange tubes 4 of the coil 3 are arranged around the center line of the upper header 2.

As shown in fig. 2, the heat exchanger tube 4 is not a complete circle but a mouth is left, thereby forming a free end of the heat exchanger tube. The angle of the arc of the mouth part is 70-120 degrees, namely the sum of included angles b and c in figure 3 is 70-120 degrees.

Preferably, the pipe diameter of the lower pipe box 1 is smaller than that of the upper pipe box 2.

The inner diameter of the lower tube box is R1, the inner diameter of the upper tube box is R2, preferably 0.45< R1/R2< 0.88.

Through the arrangement, the heat transfer can be further enhanced, and the heat exchange efficiency is improved by 8-15%.

Preferably, the distance between the adjacent heat exchange tubes 4 is greater as it becomes farther from the center of the upper header 2. The distance from the center of the upper tube box 2 is L, the distance between adjacent heat exchange tubes is M, and M is S (L), and the M is a function of L, so that the following requirements are met: s '(L) >0, where S' (L) is the first derivative of S (L).

For example, as shown in fig. 2, the distance between the heat exchange tubes BC is greater than the distance between AB and the distance between the heat exchange tubes CD is greater than the distance between BC in the radial direction with the center of the upper header 2 as the center.

Preferably, the distance between the adjacent heat exchange tubes 4 is continuously increased to a larger and larger extent. The following requirements are met: s "(L) >0, where S" (L) is the second derivative of S (L).

Through the preferred setting, can further improve heat exchange efficiency, increase the homogeneity of the heat distribution of heat transfer. Experiments show that the heat exchange efficiency can be improved by 8-12% by the arrangement.

Preferably, the heat exchange tubes 4 have a larger diameter as they are farther from the center of the upper header 2.

Preferably, the diameter of the heat exchange tube 4 is continuously increased to a larger and larger extent.

Through the preferable arrangement, the heat exchange efficiency can be further improved, and the uniformity of heat exchange is increased. Experiments show that the heat exchange efficiency can be improved by about 10% by the arrangement.

Preferably, as shown in fig. 1, the number of the coil pipes 4 is plural, and the plural coil pipes 4 are in a parallel structure.

It was found in experiments that the distance relationship between the lower channel case 1, the upper channel case 2 and the heat exchange tubes 4 may have an influence on the heat exchange efficiency and uniformity. If the distance between the heat exchange tubes 4 is too big, then heat exchange efficiency is too poor, and the distance between the heat exchange tubes 4 is too little, then the heat exchange tubes 4 distribute too closely, also can influence heat exchange efficiency, and the pipe diameter size of pipe case and heat exchange tube influences the volume of the liquid or the steam that hold, then can exert an influence to the vibration of

free end

6, 7 to influence the heat transfer. Therefore, the diameters of the lower tube box 1 and the upper tube box 2 have a certain relationship with the distance between the heat exchange tubes 4.

The invention provides an optimal size relation summarized by test data of a plurality of heat pipes with different sizes. Starting from the maximum heat exchange amount in the heat exchange effect, nearly 200 forms are calculated. The dimensional relationship is as follows:

the inner diameter of the lower tube box is R1, the inner diameter of the upper tube box is R2, the outer diameter of the heat exchange tube is D, the distance between the center lines of the adjacent heat exchange tubes is L, and the following relations are satisfied:

wherein 17.03< a <18.12,9.15< b < 10.11;

55mm<R1<100mm；95mm<R2<145mm；

25mm<D<80mm；40mm<L<120mm；

0.45< R1/R2< 0.88; preferably 0.5-0.8, more preferably 0.59< R1/R2< 0.71;

0.5< D/L < 0.7; preferably 0.58< D/L < 0.66.

Preferably, 17.32< a <17.72,9.45< b < 9.91;

further preferably, a =17.54 and b = 9.68.

Preferably, the number of heat exchange tubes is 3 to 5, preferably 3 or 4.

Preferably, the value of a is continuously increased and the value of b is continuously decreased with the increase of R1/R2. Through the change, the structural parameters of the heat pipe are optimized and reasonable, and the calculated data are accurate.

The distance between the central lines of the lower tube box 1 and the upper tube box 2 is 320-380 mm; preferably 340-.

Preferably, the radius of the heat exchange tube is preferably 10-40 mm; preferably 15 to 35mm, more preferably 20 to 30 mm.

If the diameters of the adjacent heat exchange tubes are different, the diameter D of each heat exchange tube is the average value of the diameters of the adjacent heat exchange tubes.

Further preferably, the central lines of the heat exchange tubes 4 of the same coil are positioned on the same plane. Preferably, the plane is perpendicular to a plane formed by the center lines of the lower and

upper headers

1 and 2. Preferably, the planes formed by the center lines of the different coiled heat exchange tubes 4 are parallel to each other.

Further preferably, the distance between adjacent coils 3 is 2.8-3.6 times the outer diameter of the coiled heat exchange tube 4. The distance between adjacent coils 3 is calculated as the distance between the planes in which the center lines of the coiled heat exchange tubes 4 lie.

Further preferably, if the diameters of the heat exchange tubes of the coil are different, the average value of the diameters of the heat exchange tubes of the same coil is taken as the average diameter of the coil. For example, the average of the heat exchange tubes a-D as shown in fig. 2. The diameter of two adjacent coils 3 is then averaged to calculate the distance of the adjacent coils.

Preferably, the ends of the heat exchange tubes at the free ends 6, 7 of the same side are aligned in the same plane, and the extension of the ends (or the plane in which the ends lie) passes through the midline of the lower header 1, as shown in fig. 3.

Preferably, as shown in fig. 2, the inner heat exchange tubes of the coil 3 have first ends connected to the upper header 2 and second ends connected to one ends of the adjacent outer heat exchange tubes, the outermost heat exchange tubes of the coil 3 have one ends connected to the lower header 1, and the ends of the adjacent heat exchange tubes communicate to form a serial structure.

Preferably, a plane where a line connecting centers of the lower header 1 and the upper header 2 is located is a vertical direction.

As shown in FIG. 3, the plane of the first end 6 forms an included angle c of 40-65 degrees with the plane of the central lines of the lower header 1 and the upper header 2.

The plane of the second end 7 forms an included angle b of 55-65 degrees with the plane of the central lines of the lower pipe box 1 and the upper pipe box 2.

Through the design of the preferable included angle, the vibration of the free end is optimal, and therefore the heat exchange efficiency is optimal.

As shown in fig. 2, the number of the heat exchange tubes 4 of the coil is 4, and the heat exchange tubes A, B, C, D are communicated. Of course, the number is not limited to four, and a plurality of the connecting structures are the same as those in fig. 2.

The number of the coil pipes 3 is multiple, the floating coil pipes 1 are respectively and independently connected with the lower pipe box 1 and the upper pipe box 2, namely the floating coil pipes 1 are in a parallel structure.

Although the present invention has been described with reference to the preferred embodiments, it is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A heat pipe comprises a lower pipe box, an upper pipe box, a heat exchange pipe bundle and a return pipe, wherein the heat exchange pipe bundle is communicated with the lower pipe box and the upper pipe box, the lower pipe box is an evaporation end, a condensation end comprises the upper pipe box, fluid is subjected to heat absorption and evaporation in the lower pipe box and is condensed in the upper pipe box, and the condensed fluid returns to the lower pipe box through the return pipe; the return pipe is connected with the positions of the end parts of the two sides of the lower pipe box and the upper pipe box, and the lower pipe box is provided with an electric heating device; the heat exchange tube bundle is a coil, each coil comprises a plurality of arc-shaped heat exchange tubes, the end parts of the adjacent heat exchange tubes are communicated, so that the plurality of heat exchange tubes form a serial structure, and the end parts of the heat exchange tubes form free ends of the heat exchange tubes; the central lines of the plurality of arc-shaped heat exchange tubes are arcs of concentric circles; the concentric circles are circles taking the center of the cross section of the upper header as the center of a circle; the distance from the center of the upper tube box is L, the distance between adjacent heat exchange tubes is M, and M is S (L), and the M is a function of L, so that the following requirements are met: s '(L) >0, where S' (L) is the first derivative of S (L).

2. The heat pipe of claim 1, S "(L) >0, wherein S" (L) is the second derivative of S (L).