CN115014099B

CN115014099B - Tube-shell heat exchanger with periodically-changing heating function

Info

Publication number: CN115014099B
Application number: CN202210311314.8A
Authority: CN
Inventors: 冷学礼; 修蓬岳; 王进; 张冠敏; 邱燕; 王一龙; 柏超; 魏民; 田茂诚
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2023-08-22
Anticipated expiration: 2039-12-03
Also published as: CN112902705B; CN112902705A; CN115014099A

Abstract

The invention provides a tube-shell heat exchanger for periodically changing heating, which comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, heat exchange components are arranged in the shell, a first heat source, a second heat source and a third heat source are respectively arranged as a plurality of electric heating components, each electric heating component is independently controlled, and the starting quantity of the electric heating components is periodically changed along with the change of time. By the time-variable heating, the fluid can be evaporated and expanded in the elastic tube bundle frequently, so that the heating efficiency and the descaling operation can be further realized.

Description

Tube-shell heat exchanger with periodically-changing heating function

Technical Field

The invention relates to a shell-and-tube heat exchanger, in particular to a shell-and-tube heat exchanger with periodically-changing heating.

Background

The shell-and-tube heat exchanger is widely applied to industries such as chemical industry, petroleum, refrigeration, nuclear energy, power and the like, and because of the worldwide energy crisis, in order to reduce energy consumption, the demand for the heat exchanger in industrial production is also increasing, and the quality requirement for the heat exchanger is also increasing. In recent decades, although compact heat exchangers (plate-type, plate-fin-type, pressure-welded plate-type heat exchangers, etc.), heat pipe-type heat exchangers, direct contact heat exchangers, etc. have been rapidly developed, shell-and-tube heat exchangers still occupy the dominant position of yield and usage due to high reliability and wide adaptability, and the usage of the shell-and-tube heat exchangers in the current industrial devices still accounts for about 70% of the usage of all heat exchangers according to relevant statistics.

After the shell-and-tube heat exchanger is scaled, the heat exchanger is cleaned by adopting the conventional modes of steam sweeping, back flushing and the like, and the production practice proves that the effect is not very good. The heat exchanger seal heads can be detached only by adopting a physical cleaning mode, but the heat exchanger seal heads are cleaned by adopting the mode, so that the operation is complex, the time consumption is long, the investment of manpower and material resources is large, and great difficulty is brought to continuous industrial production.

The enhanced heat exchange is realized by utilizing the vibration of the fluid-induced heat transfer element, which is a form of passive enhanced heat exchange, and the strict prevention of the fluid vibration induction in the heat exchanger can be changed into the effective utilization of the vibration, so that the convective heat transfer coefficient of the transmission element under the low flow velocity is greatly improved, the dirt on the surface of the heat transfer element is restrained by utilizing the vibration, the dirt thermal resistance is reduced, and the composite enhanced heat transfer is realized.

In applications, it has been found that continuous heating can result in internal fluid formation stability, i.e., no or little fluid flow, or stable flow, resulting in greatly reduced heat exchange tube vibration performance, thereby affecting heat exchange tube descaling and heating efficiency.

Current shell and tube heat exchangers include dual headers, one header evaporating and one header condensing, forming vibratory descaling heat pipes. Thereby improving the heat exchange efficiency of the heat pipe and reducing scaling. However, the heat exchange uniformity of the heat pipe is not enough, only one side is condensed, but the heat exchange amount is small, so that improvement is needed, and a heat pipe system with a novel structure is developed. There is therefore a need for improvements in the heat exchangers described above.

Disclosure of Invention

The invention provides an electric heating tube shell type heat exchanger with a novel structure, aiming at the defects of a shell type heat exchanger in the prior art. The shell-and-tube heat exchanger can realize periodic frequent vibration of the heat exchange tube, and improves the heating efficiency, thereby realizing good descaling and heating effects.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the utility model provides a tube-shell heat exchanger of periodic variation heating, includes the casing, the casing both ends set up the tube sheet respectively, set up heat transfer part in the casing, first heat source, second heat source, third heat source all set up to a plurality of electric heating parts respectively, every electric heating part independent control, along with the change of time, the quantity that electric heating part started carries out periodic variation.

Alternatively, the first heat source, the second heat source and the third heat source are respectively provided with n electric heating components, and in a half period of 0-T/2 when T=0, the n electric heating components of the first heat source and the third heat source are all closed, and the n electric heating components of the second heat source are all opened;

then, at intervals of T/2n, the first heat source and the third heat source respectively start an electric heating component, the second heat source turns off the electric heating component until the first heat source and the third heat source are all started at the time of T/2, and the second heat source is all turned off.

Alternatively, in the half period of T/2-T, every T/2n time, the second heat source starts an electric heating component, and the first heat source and the third heat source respectively turn off an electric heating component until the period T is over, the second heat source is started completely, and the first heat source and the third heat source are turned off completely.

Alternatively, the heating power of each of the electric heating elements of the first heat source and the third heat source is the same. The power of each electric heating component of the second heat source is twice the power of the electric heating components of the first and third heat sources.

The shell-and-tube heat exchanger comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, a heat exchange component is arranged in the shell, the heat exchange component comprises a central tube, a left tube group, a right tube group and a tube group, the tube group comprises a left tube group and a right tube group, the left tube group is communicated with the left tube group and the central tube, the right tube group is communicated with the right tube group and the central tube, so that the central tube, the left tube, the right tube and the tube group form a heating fluid closed cycle, the left tube and/or the central tube and/or the right tube are filled with a phase-change fluid, the left tube, the central tube and the right tube are respectively provided with a first heat source, a second heat source and a third heat source, each tube group comprises a plurality of circular tubes in a circular arc shape, the end parts of adjacent circular tubes are communicated, the plurality of circular tubes form a serial structure, and the end parts of the circular tubes form a free end of the circular tubes; the central tube comprises a first tube orifice and a second tube orifice, the first tube orifice is connected with the inlet of the left tube group, the second tube orifice is connected with the inlet of the right tube group, the outlet of the left tube group is connected with the left tube, and the outlet of the right tube group is connected with the right tube; the first pipe orifice and the second pipe orifice are arranged on the same side of the central pipe, and the left pipe group and the right pipe group are in mirror symmetry along the surface where the axle center of the central pipe is located; a left return pipe is arranged between the left side pipe and the central pipe, and a right return pipe is arranged between the right side pipe and the central pipe; the controller controls whether the first heat source, the second heat source and the third heat source heat.

Preferably, the annular tubes of the left tube group are distributed by taking the axis of the left tube as the center of a circle, and the annular tubes of the right tube group are distributed by taking the axis of the right tube as the center of a circle.

Preferably, the heat source is an electric heater.

The invention has the following advantages:

1. according to the invention, through improving the prior art, the pipe box and the coil pipe are respectively arranged into two pipes which are distributed left and right, the heat source is arranged in each pipe box, and each heat source can be independently heated to become an evaporation part, so that the heat transfer is enhanced, the coil pipes distributed on the left side and the right side can perform vibration heat exchange and descaling, the heat exchange and descaling areas are enlarged, the more uniform vibration is realized, the more uniform heat exchange effect is realized, the heat exchange area is increased, and the heat exchange and descaling effects are enhanced.

2. According to the invention, 3 heat sources of the steam generator are heated alternately in a period, so that the periodic frequent vibration of the elastic coil can be realized, thereby realizing good descaling and heating effects and ensuring that the heating power is basically the same in time.

3. The invention increases the heating power and reduces the heating power periodically, so that the heated fluid can generate a continuously variable volume to induce the free end of the coil to vibrate, thereby enhancing heat transfer.

4. According to the invention, the heating efficiency can be further improved through the arrangement of pipe diameters and interval distribution of the pipe groups in the length direction.

5. According to the invention, through a large number of experiments and numerical simulation, the optimal relation of parameters of the shell-and-tube heat exchanger is optimized, so that the optimal heating efficiency is realized.

6. The invention designs a novel structural triangle layout diagram of the multi-heat exchange component, optimizes structural parameters of the layout, and can further improve heating efficiency through the layout.

Drawings

Fig. 1 is a schematic view of a housing structure.

Fig. 2 is a top view of a heat exchange component of the present invention.

Fig. 3 is a front view of a heat exchange component of the present invention.

Fig. 4 is a front view of another embodiment of the heat exchange member of the present invention.

Fig. 5 is a schematic view of the dimensional structure of the heat exchange member of the present invention.

Fig. 6 is a schematic layout of the heat exchange member of the present invention in a circular section heater.

Detailed Description

A shell-and-tube heat exchanger, as shown in fig. 1, comprising a housing 20, heat exchange means 23, a shell side inlet connection 21 and a shell side outlet connection 22; the heat exchange component 23 is arranged in the shell 20 and is fixedly connected to the front tube plate 16 and the rear tube plate 19; the shell side inlet connecting pipe 21 and the shell side outlet connecting pipe 22 are arranged on the shell 20; fluid enters from the shell side inlet connecting pipe 21, exchanges heat through the heat exchange component, and exits from the shell side outlet connecting pipe 22.

Preferably, the heat exchange member extends in a horizontal direction. The heat exchangers are arranged in the horizontal direction.

Fig. 2 shows a plan view of a heat exchange member 23, which, as shown in fig. 2, comprises a central tube 8, a left tube 21, a right tube 22 and a tube group 1, the tube group 1 comprises a left tube group 11 and a right tube group 12, the left tube group 11 communicates with the left tube 21 and the central tube 8, the right tube group 12 communicates with the right tube 22 and the central tube 8, so that the central tube 8, the left tube 21, the right tube 22 and the tube group 1 form a heating fluid closed cycle, the left tube 21 and/or the central tube 8 and/or the right tube 22 are filled with a phase change fluid, the left tube 21, the central tube 8 and the right tube 22 are provided with a first heat source 91, a second heat source 92 and a third heat source 93, respectively, each tube group 1 comprises a plurality of circular tubes 7 in circular arc shape, the ends of adjacent circular tubes 7 communicate, the plurality of circular tubes 7 form a series structure, and the ends of the circular tubes 7 form free ends 3-6 of the circular tubes; the central tube comprises a first tube orifice 10 and a second tube orifice 13, the first tube orifice 10 is connected with the inlet of the left tube group 11, the second tube orifice 13 is connected with the inlet of the right tube group 12, the outlet of the left tube group 11 is connected with the left tube 21, and the outlet of the right tube group 12 is connected with the right tube 22; the first nozzle 10 and the second nozzle 13 are arranged on the same side of the central tube 8. The left tube group and the right tube group are mirror symmetry along the surface of the axle center of the central tube.

The ends of the two ends of the center tube 8, the left tube 21 and the right tube 22 are arranged in the openings of the front and rear tube plates 16, 19 for fixation. The first nozzle 10 and the second nozzle 13 are located on the upper side of the central tube 8.

Preferably, a left return pipe 14 is provided between the left side pipe 21 and the center pipe 8, and a right return pipe 15 is provided between the right side pipe 22 and the center pipe 8. Preferably, the return pipe is arranged at the end of the central pipe. The two ends of the central tube are preferred.

Preferably, the fluid is a phase-change fluid, a vapor-liquid phase-change fluid, and the first heat source 91, the second heat source 92, and the third heat source 93 are in data connection with a controller, and the controller controls the first heat source 91, the second heat source 92, and the third heat source 93 to heat.

The fluid is heated and evaporated in the central tube 8 and flows along the annular tube bundle to the left and right headers 21, 22, and the fluid expands in volume after being heated to form steam, and the steam is much larger in volume than water, so that the formed steam can quickly impact flow in the coil. Because the volume expansion and the steam flow can induce the free end of the annular tube to vibrate, the free end of the heat exchange tube transmits the vibration to surrounding heat exchange fluid in the vibration process, and the fluids can generate disturbance, so that the surrounding heat exchange fluid forms turbulence and damages a boundary layer, and the purpose of enhancing heat transfer is realized. The fluid flows back to the central tube through the return tube after the left and right side tubes condense and release heat. Conversely, the fluid can also be heated in the left and right side pipes, then enter the central pipe to be condensed and then return to the left and right side pipes for circulation through the return pipe.

According to the invention, the prior art is improved, the condensing header and the tube groups are respectively arranged into two groups which are distributed left and right, so that the tube groups distributed on the left side and the right side can perform vibration heat exchange and scale removal, thereby enlarging the heat exchange vibration area, enabling the vibration to be more uniform, enabling the heat exchange effect to be more uniform, increasing the heat exchange area and strengthening the heat exchange and scale removal effects.

The invention has the advantages that 3 heat sources of the steam generator are heated alternately in a period, and the periodic frequent vibration of the elastic coil can be realized, so that good descaling and heating effects are realized, and the heating power is ensured to be basically the same in time.

Preferably, the annular tubes of the left tube group are distributed by taking the axis of the left tube as the center of a circle, and the annular tubes of the right tube group are distributed by taking the axis of the right tube as the center of a circle. Through setting up left and right sides pipe as the centre of a circle, the distribution of assurance annular pipe that can be better for vibration and heating are even.

Preferably, the tube group is plural.

Preferably, the center tube 8, the left tube 21, and the right tube 22 are provided along the longitudinal direction.

Preferably, the left tube group 21 and the right tube group 22 are arranged in a staggered manner in the longitudinal direction as shown in fig. 3. Through staggered distribution, vibration heat exchange and descaling can be performed on different lengths, so that vibration is more uniform, and heat exchange and descaling effects are enhanced.

Preferably, the tube group 1 is provided in plural (for example, the same side (left side or right side)) along the longitudinal direction of the center tube 8, and the tube diameter of the tube group 1 (for example, the same side (left side or right side)) is increased along the direction of fluid flow in the shell side.

Preferably, the annular tube diameter of the tube set (e.g., on the same side (left or right)) is increasing in magnitude along the direction of fluid flow within the shell side.

Through the pipe diameter range increase of the heat exchange pipe, the shell side fluid outlet position can be guaranteed to fully exchange heat, a heat exchange effect similar to countercurrent is formed, the heat transfer effect is further enhanced, the overall vibration effect is uniform, the heat exchange effect is increased, and the heat exchange effect and the descaling effect are further improved. Experiments show that better heat exchange effect and descaling effect can be obtained by adopting the structural design.

Preferably, the same side (left or right) tube group is provided in plural along the length direction of the center tube 8, and the pitch of adjacent tube groups on the same side (left or right) becomes smaller along the direction of fluid flow in the shell side.

Preferably, the spacing between the tube sets on the same side (left or right) is increasing with decreasing amplitude along the direction of fluid flow within the shell side.

Through the increase of the interval amplitude of the heat exchange tubes, the shell side fluid outlet position can be guaranteed to exchange heat fully, a heat exchange effect similar to countercurrent is formed, the heat transfer effect is further enhanced, the overall vibration effect is uniform, the heat exchange effect is increased, and the heat exchange effect and the descaling effect are further improved. Experiments show that better heat exchange effect and descaling effect can be obtained by adopting the structural design.

In the experiments, it was found that the pipe diameters, distances, and pipe diameters of the left side pipe 21, the right side pipe 22, the center pipe 8, and the ring pipe may have an influence on heat exchange efficiency and uniformity. If the distance between the headers is too large, the heat exchange efficiency is too poor, the distance between the annular pipes is too small, the annular pipes are distributed too densely, the heat exchange efficiency is also affected, the sizes of the headers and the heat exchange pipes affect the volume of the contained liquid or steam, and vibration of the free ends is affected, so that heat exchange is affected. The pipe diameters, distances and pipe diameters of the left side pipe 21, the right side pipe 22, the center pipe 8 and the annular pipe have a certain relationship.

The invention relates to an optimal size relation which is summarized by numerical simulation and test data of a plurality of heat pipes with different sizes. From the maximum heat exchange amount in the heat exchange effect, nearly 200 forms are calculated. The dimensional relationships are as follows:

the distance between the center of the center tube 8 and the center of the left tube 21 is equal to the distance between the center of the center tube 8 and the center of the right tube 21, L, the pipe diameter of the left tube 21, the pipe diameter of the center tube 8, the radius of the right tube 22 are R, the radius of the axis of the innermost annular tube in the annular tube is R1, and the radius of the axis of the outermost annular tube is R2, and the following requirements are satisfied:

r1/r2=a.ln (R/L) +b; where a, b are parameters and Ln is a logarithmic function, where 0.6212< a <0.6216,1.300< b <1.301; preferably, a=0.6214 and b= 1.3005.

Preferably, 35< R <61mm;114< L <190mm;69< R1<121mm,119< R2<201mm.

Preferably, the number of annular tubes of the tube group is 3 to 5, preferably 3 or 4.

Preferably, 0.55< R1/R2<0.62;0.3< R/L <0.33.

Preferably, 0.583< R1/R2<0.615;0.315< R/L <0.332.

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

Preferably, the centers of the left side tube 21, the right side tube 22 and the center tube 8 are aligned.

Preferably, the arc between the ends of the free ends 3, 4 is 95-130 degrees, preferably 120 degrees, centered on the central axis of the left tube. The free ends 5, 6 and the free ends 3, 4 have the same radian. By the design of the preferable included angle, the vibration of the free end is optimized, so that the heating efficiency is optimized.

Preferably, the heat exchange component can be used as an immersed heat exchange component, immersed in fluid to heat the fluid, for example, the heat exchange component can be used as an air radiator heating component and also can be used as a water heater heating component.

The heating power of the first, second and third heat sources is preferably 1000-2000W, more preferably 1500W.

Preferably, the box body is a circular section, and a plurality of heat exchange components are arranged, wherein one of the heat exchange components is arranged at the center of the circular section (the center pipe is arranged at the center) and the other heat exchange components are distributed around the center of the circular section.

Preferably, the tube bundle of the tube group 1 is an elastic tube bundle.

By providing the tube bundle of the tube group 1 with an elastic tube bundle, the heat exchange coefficient can be further improved.

Further preferably, the heat source is an electrical heating rod.

The number of the tube groups 1 is plural, and the plurality of tube groups 1 are in a parallel structure.

The heat exchanger shown in fig. 6 has a housing of circular cross section, and the plurality of heat exchange members are disposed in the circular housing. Preferably, three heat exchange components are arranged in the shell, the center of the central tube of each heat exchange component is positioned at the middle point of an inscribed regular triangle with a circular section, the connecting line of the centers of the central tubes forms the regular triangle, the upper part is a heat exchange component, the lower part is two heat exchange components, and the connecting lines formed by the centers of the left side tube, the right side tube and the central tube of each heat exchange component are of a parallel structure. Through such setting, can make the interior fluid of heater fully reach vibrations and heat transfer purpose, improve the heat transfer effect.

Preferably, the tube bundle of the tube group is an elastic tube bundle.

By arranging the tube bundles of the tube group with the elastic tube bundles, the heat exchange coefficient can be further improved.

Further preferably, the heat source is an electrical heating rod.

The plurality of the tube groups are in parallel connection.

The heat exchanger as shown has a circular cross-section housing with the plurality of heat exchange components disposed within the circular housing. Preferably, three heat exchange components are arranged in the shell, the center of the central tube of each heat exchange component is positioned at the middle point of an inscribed regular triangle with a circular section, the connecting line of the centers of the central tubes forms the regular triangle, the upper part is a heat exchange component, the lower part is two heat exchange components, and the connecting lines formed by the centers of the left side tube, the right side tube and the central tube of each heat exchange component are of a parallel structure. Through such setting, can make the interior fluid of heater fully reach vibrations and heat transfer purpose, improve the heat transfer effect.

Preferably, the first and third heat sources and the second heat source are alternately heated periodically with time.

In a period of time T, the heating powers of the first heat source and the third heat source are W1 and W3, the heating power of the second heat source is W2, and the change rule of W1, W2 and W3 is as follows:

in the half period of 0-T/2, W1=n, W2=0 and W3=n, namely the heating power of the first heat source and the third heat source is kept constant, and the second heat source is not heated;

in the half period of T/2-T, W1=0, W2=Z and W3=0, namely the first heat source and the third heat source are not heated, and the heating power of the second heat source is kept constant.

Alternatively, in one cycle time T, the heating powers of the first heat source and the third heat source are W1 and W3, the heating powers of the second heat source are W2, and the change rule of W1, W2 and W3 is as follows:

in the half period of 0-T/2, W2=Z, W1=0 and W3=0, namely the first heat source and the third heat source are not heated, and the heating power of the second heat source is kept constant;

within half period of T/2-T, w2=0, w1=n; w3=n; wherein n is a constant value, and the unit is watt (W), namely the second heat source does not heat, and the heating power of the first heat source and the third heat source is kept constant.

Wherein Z, n is a constant value in watts (W). Preferably, z=2n.

T is 50-80 minutes, where 1000W < n <1500W.

Through foretell time variability heats, can make the fluid frequent evaporation expansion in the elastic tube bank, because the expansion and the flow direction of continuous periodic change steam have destroyed the stability of single heating to continuous vibration that drives the elastic tube bank, thereby can further realize heating efficiency and scale removal operation.

Compared with the prior application, the heating mode not only ensures that the heat exchange component heats in the whole period, but also enables the elastic tube bundle to vibrate frequently, thereby further realizing heating efficiency and descaling operation.

Preferably, the heat sources are arranged in a plurality of sections along the length direction of the tube shell, each section is independently controlled, and when T=0 in a half period of 0-T/2 along with the change of time, all sections of the first heat source and the third heat source are closed, and all sections of the second heat source are opened;

then the first heat source and the third heat source are sequentially started along the direction opposite to the fluid flow direction in the shell side (for example, the right end of the shell side is started in fig. 1) until all the sections are started, and simultaneously the second heat source is sequentially closed along the fluid flow direction in the shell side until all the sections are closed;

in the half period of T/2-T, the first heat source and the third heat source are turned off sequentially along the fluid flow in the shell pass, the second heat source is turned on sequentially along the opposite direction of the fluid flow in the shell pass until the period is over, all the sections of the first heat source and the third heat source are turned off, and all the sections of the second heat source are turned on.

That is, assuming that the first heat source, the second heat source and the third heat source are all n sections, in a period T, when t=0, all sections of the first heat source and the third heat source are all closed, and all sections of the second heat source are all opened;

then starting a section from the direction opposite to the fluid flow direction in the shell side by the first heat source and the third heat source at intervals of T/2n, and closing a section from the fluid flow direction in the shell side by the second heat source until all the sections of the first heat source and the third heat source are started and all the sections of the second heat source are closed at intervals of T/2;

then, every T/2n, the first heat source and the third heat source are started from the fluid flowing direction in the shell side, one section is closed every T/2n, meanwhile, the second heat source is started from the opposite direction of the fluid flowing direction in the shell side, one section is opened every T/2n until all sections of the first heat source and the third heat source are closed at the T time, and all sections of the second heat source are opened.

Alternatively, during half a period of 0-T/2, when t=0, all segments of the first heat source, the third heat source are all on, and all segments of the second heat source are all off; then the first heat source and the third heat source are turned off in sequence along the fluid flow direction in the shell pass until all the sections are turned off, and the second heat source is turned on in sequence along the opposite direction of the fluid flow direction in the shell pass until all the sections are turned on;

in the half period of T/2-T, the second heat source is turned off from the upper end, the first heat source and the third heat source are turned on from the opposite direction of the fluid flow direction in the shell pass, until the period is over, all the sections of the second heat source are turned off, and all the sections of the first heat source, the second heat source and the third heat source are turned on.

That is, assuming that the first heat source, the second heat source and the third heat source are all n sections, in a period T, when t=0, all sections of the second heat source are all closed, and all sections of the first heat source and the third heat source are all opened;

then starting a section from the direction opposite to the fluid flow direction in the shell side by the second heat source at intervals of T/2n, and starting to close a section from the fluid flow direction in the shell side by the first heat source and the third heat source until all sections of the second heat source are started at the time of T/2, and closing all sections of the first heat source and the third heat source;

and then starting the second heat source from the flow direction of the fluid in the shell side every T/2n, closing one section every T/2n, starting the first heat source and the third heat source from the opposite direction of the flow direction of the fluid in the shell side, opening one section every T/2n until all sections of the second heat source are closed at the T time, and opening all sections of the first heat source and the third heat source.

Preferably, the first heat source and the third heat source have the same heating power for each section. The second heat source each section is twice the heating power of each section of the first and third heat sources. The relationship diagram is shown in fig. 4.

The heat source is gradually started along the opposite direction of the fluid flow and is closed from the fluid flow direction, so that the rear-end heating temperature is high, a similar countercurrent effect is formed, the fluid flow is further promoted, and the elastic vibration effect is increased. Through the change of the time-variable heating power, fluid can be enabled to be frequently evaporated and expanded and contracted in the elastic tube bundle, so that the elastic tube bundle is continuously driven to vibrate, and heating efficiency and descaling operation can be further realized.

Preferably, the first heat source is provided in a plurality, each of the heat sources has different power, and one or more of the heat sources can be combined to form different heating powers, and the second heat source is provided in a plurality, each of the heat sources has different power. The third heat source is arranged in a plurality, each heat source has different power, and one or a plurality of the third heat sources can be combined to form different heating powers

In the period T, t=0, the plurality of first heat sources and the plurality of third heat sources are all turned off, the plurality of second heat sources are all turned on,

as an option, in a half period of 0-T/2, starting a single first heat source according to time sequence, starting the single first heat source independently according to the sequence of increasing heating power, then starting two first heat sources independently according to the sequence of increasing heating power, then gradually increasing the number of the first heat sources, and if the number is n, starting the n first heat sources independently according to the sequence of increasing heating power; until all the first heat sources are started, ensuring that the heating power of the first heat sources is increased in sequence;

simultaneously, starting a single third heat source, wherein the single third heat source is independently started according to the order of sequentially increasing the heating power, then starting two third heat sources, the two third heat sources are independently started according to the order of sequentially increasing the heating power, then gradually increasing the starting quantity of the third heat sources, and if the quantity is n, the n third heat sources are independently started according to the order of sequentially increasing the heating power; until all third heat sources are started, ensuring that the heating power of the third heat sources is increased in sequence;

simultaneously, the single second heat source is closed, the single second heat source is independently closed according to the sequence of increasing the heating power, then the two second heat sources are closed, the two second heat sources are independently closed according to the sequence of increasing the heating power, then the number of closed second heat sources is gradually increased, and if the number is n, the n second heat sources are independently closed according to the sequence of increasing the heating power; and until all the second heat sources are turned off finally, the heating power of the second heat sources is ensured to be reduced in sequence.

In the next half period of T/2-T, firstly, a single first heat source is closed, the single first heat source is independently closed according to the order of increasing heating power in turn, then two first heat sources are closed, the two first heat sources are independently closed according to the order of increasing heating power in turn, then the number of closed first heat sources is gradually increased, and if the number is n, the n first heat sources are independently closed according to the order of increasing heating power in turn; and until all the first heat sources are closed finally, ensuring that the heating power of the first heat sources is reduced in sequence.

Simultaneously, a single third heat source is closed, the single third heat source is independently closed according to the sequence of increasing the heating power, then two third heat sources are closed, the two third heat sources are independently closed according to the sequence of increasing the heating power, then the number of the closed third heat sources is gradually increased, and if the number is n, the n third heat sources are independently closed according to the sequence of increasing the heating power; and until all third heat sources are turned off, ensuring that the heating power of the third heat sources is reduced in sequence.

Simultaneously, starting a single second heat source according to time sequence, independently starting the single second heat source according to the sequence of increasing heating power, then starting two second heat sources independently according to the sequence of increasing heating power, then gradually increasing the number of the second heat sources to be started, and if the number is n, independently starting the n second heat sources according to the sequence of increasing heating power; and until all the second heat sources are started, ensuring that the heating power of the second heat sources is increased in sequence.

For example, the number of the first heat sources is three, namely a first heat source V1, a first heat source V2 and a first heat source V3, and the heating powers are W1, W2 and W3 respectively, wherein W1< W2< W3, W1+ W2> W3; that is, the sum of the heating powers of V1 and V2 is greater than the heating power of V3, V1, V2, V3, V1 plus V2, V1 plus V3, V2 plus V3, then v1+v2+v3 are sequentially started in time sequence in the upper half period, and the order of closing in the lower half period is V1, V2, V3, V1 plus V2, V1 plus V3, V2 plus V3.

The number of the third heat sources is three, namely a third heat source V4, a third heat source V5 and a third heat source V6, and the heating power is W4, W5 and W6 respectively, wherein W4< W5< W6, W4+ W5> W6; that is, the sum of the heating powers of V4 and V5 is greater than the heating power of V6, V4, V5, V6, V4 plus V5, V4 plus V6, V5 plus V6 are sequentially started in time sequence in the upper half period, then v4+v5+v6, and the order of closing in the lower half period is V4, V5, V6, V4 plus V5, V4 plus V6, V5 plus V6.

The number of the second heat sources is three, namely a second heat source Z1, a second heat source Z2 and a second heat source Z3, and the heating power is W1, W2 and W3 respectively, wherein W1< W2< W3, W1+ W2> W3; that is, the sum of the heating powers of Z1 and Z2 is larger than the heating power of Z3, and Z1, Z2, Z3, Z1 plus Z2, Z1 plus Z3, Z2 plus Z3 are sequentially closed according to time sequence in the upper half period, then Z1+ Z2+ Z3 are sequentially opened in the lower half period, and the sequence of opening is Z1, Z2, Z3, Z1 plus Z2, Z1 plus Z3, and Z2 plus Z3 are sequentially closed.

Alternatively, during the period T, t=0, the plurality of second heat sources are all turned off, the plurality of first heat sources and the plurality of third heat sources are all turned on,

in the half period of 0-T/2, starting a single second heat source according to time sequence, independently starting the single second heat source according to the sequence of increasing heating power, then starting two second heat sources, independently starting the two second heat sources according to the sequence of increasing heating power, then gradually increasing the number of the second heat sources, and if the number is n, independently starting the n second heat sources according to the sequence of increasing heating power; until all the second heat sources are started, ensuring that the heating power of the first heat sources is increased in sequence; simultaneously, the single first heat source is closed, the single first heat source is independently closed according to the sequence of increasing the heating power, then the two first heat sources are closed, the two first heat sources are independently closed according to the sequence of increasing the heating power, then the number of closed first heat sources is gradually increased, and if the number is n, the n first heat sources are independently closed according to the sequence of increasing the heating power; and until all the second heat sources are turned off finally, the heating power of the second heat sources is ensured to be reduced in sequence. Simultaneously, a single third heat source is closed, the single third heat source is independently closed according to the sequence of increasing the heating power, then two third heat sources are closed, the two first heat sources are independently closed according to the sequence of increasing the heating power, then the number of the closed third heat sources is gradually increased, and if the number is n, the n third heat sources are independently closed according to the sequence of increasing the heating power; and until all third heat sources are turned off, ensuring that the heating power of the third heat sources is reduced in sequence.

In the next half period of T/2-T, firstly, a single second heat source is closed, the single second heat source is independently closed according to the order of increasing heating power, then two second heat sources are closed, the two second heat sources are independently closed according to the order of increasing heating power, then the number of closed second heat sources is gradually increased, and if the number is n, the n second heat sources are independently closed according to the order of increasing heating power; and until all the heat sources are turned off finally, ensuring that the heating power of the second heat source is reduced in sequence. Simultaneously, starting a single first heat source according to time sequence, independently starting the single first heat source according to the sequence of increasing heating power, then starting two first heat sources independently according to the sequence of increasing heating power, then gradually increasing the number of the first heat sources to be started, and if the number is n, independently starting the n first heat sources according to the sequence of increasing heating power; and starting all the first heat sources until the last, and ensuring that the heating power of the first heat sources is increased in sequence. Simultaneously, starting a single third heat source according to time sequence, independently starting the single third heat source according to the sequence of increasing heating power, then starting two third heat sources, independently starting the two third heat sources according to the sequence of increasing heating power, then gradually increasing the starting quantity of the third heat sources, and if the quantity is n, independently starting the n third heat sources according to the sequence of increasing heating power; and starting all third heat sources until the last, and ensuring that the heating power of the third heat sources is increased in sequence.

For example, the number of the second heat sources is three, namely a second heat source V1, a second heat source V2 and a second heat source V3, and the heating powers are W1, W2 and W3 respectively, wherein W1< W2< W3, W1+ W2> W3; that is, the sum of the heating powers of V1 and V2 is greater than the heating power of V3, V1, V2, V3, V1 plus V2, V1 plus V3, V2 plus V3, then v1+v2+v3 are sequentially started in time sequence in the upper half period, and the order of closing in the lower half period is V1, V2, V3, V1 plus V2, V1 plus V3, V2 plus V3.

The number of the first heat sources is three, namely a first heat source Z1, a first heat source Z2 and a first heat source Z3, and the heating power is W1, W2 and W3 respectively, wherein W1< W2< W3, W1+ W2> W3; that is, the sum of the heating powers of Z1 and Z2 is larger than the heating power of Z3, and Z1, Z2, Z3, Z1 plus Z2, Z1 plus Z3, Z2 plus Z3 are sequentially closed according to time sequence in the upper half period, then Z1+ Z2+ Z3 are sequentially opened in the lower half period, and the sequence of opening is Z1, Z2, Z3, Z1 plus Z2, Z1 plus Z3, and Z2 plus Z3 are sequentially closed.

The number of the third heat sources is three, namely a third heat source K1, a third heat source K2 and a third heat source K3, and the heating power is W1, W2 and W3 respectively, wherein W1< W2< W3, W1+ W2> W3; that is, the sum of the heating powers of K1 and K2 is larger than the heating power of K3, K1, K2, K3, K1, K3, K2, K3 and K1+K2+K3 are sequentially closed according to time sequence in the upper half period, and then K1, K2, K3, K1, K2, K1, K3 and K3 are opened in the lower half period.

The heating power is gradually increased and reduced through the heat source, so that the flow of fluid is further promoted, and the elastic vibration effect is improved. Through the change of the time-variable heating power, fluid can be enabled to be frequently evaporated and expanded and contracted in the elastic tube bundle, so that the elastic tube bundle is continuously driven to vibrate, and heating efficiency and descaling operation can be further realized.

Preferably, the heating power of the heat source is linearly increased during the first half period, and the heating power of the heat source is linearly decreased during the second half period.

The linear variation of the heating power is achieved by a variation of the input current or voltage.

By arranging a plurality of heat sources, the starting of increasing the number of the heat sources gradually is realized, and the linear change is realized.

Preferably, the period is 50 to 300 minutes, preferably 50 to 80 minutes; the average heating power of the single electric heating device is 2000-4000W.

Preferably, the heat source is an electric heater.

Preferably, the period is 50 to 300 minutes, preferably 50 to 80 minutes.

Preferably, the axes of the left side tube, the right side tube and the middle tube are connected on a straight line or on a plane.

Preferably, the pipe diameters of the left side pipe and the right side pipe are smaller than the pipe diameter of the middle pipe. Preferably, the pipe diameter of the middle pipe is 1.4-1.5 times of the pipe diameters of the left pipe and the right pipe. Through the pipe diameter setting of left side pipe, right side pipe and intermediate tube, can guarantee that the fluid carries out the phase transition and keeps the same or nearly transmission speed at left side pipe, right side pipe and intermediate tube to guarantee the homogeneity of heat transfer.

Preferably, the connection position of the coil pipe on the left side pipe box is lower than the connection position of the middle pipe box and the coil pipe. This ensures that steam can quickly pass upwardly into the middle tube box. Similarly, the connection position of the coil pipe on the right side pipe box is lower than the connection position of the middle pipe box and the coil pipe.

While the invention has been described in terms of preferred embodiments, the invention is not so limited. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

1. The shell-and-tube heat exchanger comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, a heat exchange component is arranged in the shell, the heat exchange component comprises a central tube, a left tube, a right tube and a tube group, the left tube group is communicated with the left tube group and the central tube, the right tube group is communicated with the right tube and the central tube, so that the central tube, the left tube, the right tube and the tube group form a heating fluid closed cycle, the left tube and/or the central tube and/or the right tube are filled with a phase-change fluid, the left tube, the central tube and the right tube are respectively provided with a first heat source, a second heat source and a third heat source, each tube group comprises a plurality of circular tubes in a circular arc shape, the ends of the adjacent circular tubes are communicated, the plurality of circular tubes form a serial structure, and the ends of the circular tubes form a free end of the circular tubes; the central tube comprises a first tube orifice and a second tube orifice, the first tube orifice is connected with the inlet of the left tube group, the second tube orifice is connected with the inlet of the right tube group, the outlet of the left tube group is connected with the left tube, and the outlet of the right tube group is connected with the right tube; the first pipe orifice and the second pipe orifice are arranged on the same side of the central pipe, and the left pipe group and the right pipe group are in mirror symmetry along the surface where the axle center of the central pipe is located; a left return pipe is arranged between the left side pipe and the central pipe, and a right return pipe is arranged between the right side pipe and the central pipe; the controller controls whether the first heat source, the second heat source and the third heat source are heated or not; the first heat source, the second heat source and the third heat source are respectively arranged into a plurality of electric heating components, each electric heating component is independently controlled, and the number of the electric heating components started is periodically changed along with the change of time.

2. The heat exchanger of claim 1, wherein the first heat source, the second heat source and the third heat source are respectively provided with n electric heating components, and in a half period of 0-T/2, when t=0, all of the n electric heating components of the first heat source and the third heat source are turned off, and all of the n electric heating components of the second heat source are turned on;

3. The heat exchanger of claim 1, wherein the second heat source activates one of the electrical heating elements every T/2n of a time period of T/2-T, and the first heat source and the third heat source are each turned off one of the electrical heating elements until the second heat source is fully activated at the end of the period T, and the first heat source and the third heat source are fully turned off.

4. The heat exchanger of claim 1, wherein each of the electrical heating elements of the first and third heat sources has the same heating power, and wherein each of the electrical heating elements of the second heat source has twice the power of the electrical heating elements of the first and third heat sources.