CN112902706A

CN112902706A - Gas shell-and-tube heat exchanger with heat source height control function

Info

Publication number: CN112902706A
Application number: CN201911223372.XA
Authority: CN
Inventors: 田茂诚; 王进; 冷学礼; 修蓬岳; 张冠敏; 邱燕; 王一龙; 柏超; 魏民
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2021-06-04

Abstract

The invention provides a gas shell-and-tube heat exchanger with heat source height control, wherein a first heat source, a second heat source and a third heat source are arranged into a plurality of sections along the height direction of a shell, each section is independently controlled, the first heat source, the second heat source and the third heat source are respectively n sections, all the sections of the first heat source and the third heat source are closed, all the sections of the second heat source are opened when T =0 in a period T, and the start and the close of each section are controlled according to the period. According to the invention, the heating temperature at the upper end is high by gradually starting the heat source and closing the heat source from the flowing direction of the fluid, a similar counter-flow effect is formed, the flowing of the fluid is further promoted, and the elastic vibration effect is increased.

Description

Gas shell-and-tube heat exchanger with heat source height control function

Technical Field

The invention relates to a shell-and-tube heat exchanger, in particular to a shell-and-tube heat exchanger for gas heat exchange.

Background

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

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

The mode of passively strengthening heat exchange is to strictly prevent the fluid vibration induction in the heat exchanger from being changed into effective utilization of vibration, so that the convective heat transfer coefficient of the transmission element at low flow speed is greatly improved, dirt on the surface of the heat transfer element is restrained by vibration, the thermal resistance of the dirt is reduced, and the composite strengthened heat transfer is realized.

In application, it is found that continuous heating can cause the internal fluid to form stability, i.e. the fluid does not flow or has little fluidity, or the flow is stable, so that the vibration performance of the heat exchange tube is greatly weakened, thereby affecting the descaling of the heat exchange tube and the heating efficiency.

Current shell and tube heat exchangers include dual headers, one header evaporating and one header condensing, thereby forming a vibrating descaled heat pipe. Thereby improving the heat exchange efficiency of the heat pipe and reducing scaling. However, the heat pipe has insufficient uniformity of heat exchange, only one side is used for condensation, and the heat exchange amount is small, so that improvement is needed to develop a heat pipe system with a novel structure. There is therefore a need for improvements to the above-described heat exchangers.

Disclosure of Invention

The invention provides an electric heating shell-and-tube heat exchanger with a novel structure, aiming at the defects of the shell-and-tube heat exchanger in the prior art. The shell-and-tube heat exchanger can realize the 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 purpose, the invention adopts the following technical scheme:

a gas shell-and-tube heat exchanger with a heat source height controlled comprises a shell, a heat exchange component, a shell side inlet connecting pipe and a shell side outlet connecting pipe; the shell pass inlet connecting pipe and the shell pass outlet connecting pipe are respectively positioned at the upper end and the lower end of the heat exchanger; the heat exchange component is arranged in the shell and fixedly connected to the upper tube plate and the lower tube plate; the shell pass inlet connecting pipe and the shell pass outlet connecting pipe are both arranged on the shell; gas enters from the shell side inlet connecting pipe, exchanges heat through the heat exchange part and exits from the shell side outlet connecting pipe; the heat exchange component comprises a central tube, a left tube, a right tube and a tube group, wherein the tube group comprises a left tube group and a right tube group, the left tube group is communicated with the left tube 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 heating fluid closed circulation, the left tube and/or the central tube and/or the right tube are filled with 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, the first heat source, the second heat source and the third heat source are arranged into multiple sections along the height direction, each section is independently controlled, the first heat source, the second heat source and the third heat source are respectively n sections, all the sections of the first heat source and the third heat source are all closed, and all the sections of the second heat source are all opened when T =0 in a period T;

then starting a section from the upper end direction by the first heat source and the third heat source every T/2n, and simultaneously closing a section from the lower end 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 T/2 n;

then every T/2n time, the first heat source and the third heat source start from the lower end and close a section every T/2n time, meanwhile, the second heat source starts from the upper end and opens a section every T/2n time until all the sections of the first heat source and the third heat source are closed and all the sections of the second heat source are opened at T time.

Preferably, each pipe group comprises a plurality of circular pipes in a circular arc shape, the ends of the adjacent circular pipes are communicated, the plurality of circular pipes form a serial structure, and the ends of the circular pipes form a free end of the circular pipes; 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; 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 or not; the first pipe orifice and the second pipe orifice are arranged on two opposite sides of the central pipe; the position of the right tube group is a position of the left tube group rotated by 180 degrees along the axis of the center tube.

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

Preferably, the heat source is an electric heater.

The invention has the following advantages:

1. 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 heating temperature at the upper end is high, a similar counter-flow effect is formed, the fluid flow is further promoted, and the elastic vibration effect is increased. Through the change of the heating power with time variability, the fluid can be frequently evaporated, expanded and contracted in the elastic tube bundle, so that the vibration of the elastic tube bundle is continuously driven, and the heating efficiency and the descaling operation can be further realized.

2. The invention provides a rotationally symmetric shell-and-tube heat exchanger for gas heat exchange, which is characterized in that more tube groups are arranged in a limited space, and each heat source can independently heat to form an evaporation part, so that heat transfer is enhanced and descaling is enhanced.

According to the invention, the prior art is improved, the pipe boxes and the coil pipes are respectively arranged into two pipes which are distributed left and right, a heat source is arranged in each pipe box, and each heat source can independently heat to form an evaporation part, so that heat transfer is enhanced, the coil pipes distributed on the left side and the right side can perform vibration heat exchange descaling, a heat exchange vibration area is enlarged, vibration can be more uniform, a heat exchange effect is more uniform, a heat exchange area is increased, and heat exchange and descaling effects are enhanced.

3. The 3 heat sources of the steam generator alternately heat 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 basically the same in time.

4. The invention increases the heating power of the coil pipe periodically and continuously and reduces the heating power, so that the heated fluid can generate the volume which is continuously in a changing state after being heated, and the free end of the coil pipe is induced to generate vibration, thereby strengthening heat transfer.

5. The invention can further improve the heating efficiency by arranging the pipe diameters and the intervals of the pipe groups in the height direction.

6. The invention optimizes the optimal relationship of the parameters of the shell-and-tube heat exchanger through a large amount of experiments and numerical simulation, thereby realizing the optimal heating efficiency.

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

Description of the drawings:

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

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

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

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

Fig. 5 is a dimensional structure schematic diagram of the heat exchange component of the invention.

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

In the figure: 1. the heat exchanger comprises a tube group, a left tube group 11, a

right tube group

12, 21, a left tube, 22, a right tube, 3, a free end, 4, a free end, 5, a free end, 6, a free end, 7, a ring tube, 8, a central tube, 91-93, a heat source, 10 a first tube orifice, 13 a second tube orifice, a left return tube 14, a right return tube 15, an upper tube plate 16, a baffle plate 17, a baffle plate 18, a lower tube plate 19, a

shell

20, 21, a shell inlet connecting tube, 22, a shell outlet connecting tube and a heat exchange component 23.

Detailed Description

A shell-and-tube heat exchanger, as shown in fig. 1, comprises a shell 20, a heat exchange component 23, a shell-side inlet connecting pipe 21 and a shell-side outlet connecting pipe 22; the shell pass inlet connecting pipe 21 and the shell pass outlet connecting pipe 22 are respectively positioned at the upper end and the lower end of the heat exchanger; the heat exchange part 23 is arranged in the shell 20 and fixedly connected to the upper tube plate 16 and the lower tube plate 19; the shell side inlet connecting pipe 21 and the shell side outlet connecting pipe 22 are both arranged on the shell 20; the gas enters from the shell side inlet connecting pipe 21, exchanges heat through the heat exchange part and exits from the shell side outlet connecting pipe 22.

Preferably, the heat exchange member extends in a vertical direction. The heat exchanger is arranged in the vertical direction.

The gas is preferably air, or carbon dioxide gas.

Fig. 2 shows a top view of a heat exchange unit 23, which, as shown in fig. 2, comprises a central tube 8, a left tube 21, a right tube 22 and a tube bank 1, the tube set 1 comprises a left tube set 11 and a right tube set 12, the left tube set 11 being in communication with a left side tube 21 and a central tube 8, the right tube set 12 being in communication with a right side tube 22 and the central tube 8, so that the central tube 8, the left side tube 21, the right side tube 22 and the tube group 1 form a closed circulation of heating fluid, the left side tube 21 and/or the central tube 8 and/or the right side tube 22 are filled with phase-change fluid, the left side tube 21, the central tube 8 and the right side tube 22 are respectively provided with a first heat source 91, a second heat source 92 and a third heat source 93, each tube group 1 comprises a plurality of circular arc-shaped annular tubes 7, the end parts of the adjacent annular tubes 7 are communicated, the plurality of annular tubes 7 form a serial structure, and the end parts of the annular tubes 7 form free ends 3-6 of the annular 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 orifice 10 and the second orifice 13 are arranged on opposite sides of the central tube 8. The position of the right tube group is a position of the left tube group rotated by 180 degrees along the axis of the center tube.

The ends of the two ends of the central tube 8, the left tube 21 and the right tube 22 are arranged in the openings of the upper and

lower tube plates

16 and 19 for fixation. The first orifice 10 and the second orifice 13 are located on the upper side of the central tube 8.

Preferably, a left return pipe 14 is arranged between the left pipe 21 and the central pipe 8, and a right return pipe 14 is arranged between the right pipe 22 and the central pipe 8. Preferably, the return pipe is arranged at the end of the central pipe. Both ends of the central tube are preferred.

Preferably, the fluid is a phase-change fluid, a vapor-liquid phase-change fluid, 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, flows to the left and

right headers

21 and 22 along the annular tube bundle, and is heated to expand in volume, so that steam is formed, and the volume of the steam is far larger than that of water, so that the formed steam can flow in the coil in a rapid impact manner. Because of volume expansion and steam flow, the free end of the annular tube can be induced to vibrate, the vibration is transmitted to the surrounding heat exchange fluid by the free end of the heat exchange tube in the vibration process, and the fluid can also generate disturbance, so that the surrounding heat exchange fluid forms disturbance flow, a boundary layer is damaged, and the purpose of enhancing heat transfer is realized. The fluid is condensed and released heat in the left and right side pipes and then flows back to the central pipe through the return pipe. Conversely, the fluid may be heated in the left and right pipes, condensed in the central pipe, and returned to the left and right pipes through the return pipe to be circulated.

According to the invention, the prior art is improved, and the condensation collecting pipe and the pipe groups are respectively arranged into two pipes which are distributed on the left side and the right side, so that the pipe groups distributed on the left side and the right side can perform vibration heat exchange descaling, the heat exchange vibration area is enlarged, the vibration can be more uniform, the heat exchange effect is more uniform, the heat exchange area is increased, and the heat exchange and descaling effects are enhanced.

The 3 heat sources of the steam generator alternately heat 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 basically the same in time.

Preferably, the annular pipes of the left pipe group are distributed by taking the axis of the left pipe as the center of a circle, and the annular pipes of the right pipe group are distributed by taking the axis of the right pipe as the center of a circle. The left side pipe and the right side pipe are arranged as circle centers, so that the distribution of the annular pipes can be better ensured, and the vibration and the heating are uniform.

Preferably, the tube group is plural.

Preferably, the center pipe 8, the left pipe 21, and the right pipe 22 are provided along the height direction.

Preferably, the left tube group 21 and the right tube group 22 are staggered in the height direction, as shown in fig. 3. Through the staggered distribution, can make to vibrate heat transfer and scale removal on the not co-altitude for the vibration is more even, strengthens heat transfer and scale removal effect.

Preferably, the tube group 2 is provided in plural (for example, the same side (left side or right side)) in the height direction of the center tube 8, and the tube diameter of the tube group 2 (for example, the same side (left side or right side)) becomes larger in the shell-side gas flow direction.

Preferably, the pipe diameter of the annular pipe of the pipe group (for example, the same side (left side or right side)) is increased continuously along the gas flowing direction in the shell side.

The pipe diameter range through the heat exchange tube increases, can guarantee that shell side gas outlet position fully carries out the heat transfer, forms the heat transfer effect like the adverse current, further strengthens the heat transfer effect moreover for whole vibration effect is even, and the heat transfer effect increases, further improves heat transfer effect and scale removal effect. Experiments show that better heat exchange effect and descaling effect can be achieved by adopting the structural design.

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

Preferably, the spacing between banks on the same side (left or right) in the shell side in the direction of gas flow increases in a decreasing manner.

The interval amplitude through the heat exchange tube increases, can guarantee that shell side gas outlet position fully carries out the heat transfer, forms the heat transfer effect like the adverse current, further strengthens the heat transfer effect moreover for the whole vibration effect is even, and the heat transfer effect increases, further improves heat transfer effect and scale removal effect. Experiments show that better heat exchange effect and descaling effect can be achieved by adopting the structural design.

In tests it was found that the pipe diameters, distances and pipe diameters of the left side pipe 21, the right side pipe 22, the central pipe 8 and the pipe diameters of the ring pipes can have an influence on the heat exchange efficiency and the uniformity. If the distance between the collector is too big, then heat exchange efficiency is too poor, and the distance between the ring shape pipe is too little, then the ring shape pipe distributes too closely, also can influence heat exchange efficiency, and the pipe diameter size of collector and heat exchange tube influences the volume of the liquid or the steam that holds, then can exert an influence to the vibration of free end to influence the heat transfer. Therefore, the pipe diameters and distances of the left pipe 21, the right pipe 22, the central pipe 8 and the pipe diameters of the ring pipes have a certain relationship.

The invention provides an optimal size relation summarized by numerical simulation and 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 distance between the center of the central tube 8 and the center of the left tube 21 is equal to the distance between the center of the central tube 8 and the center of the right tube 21, L, the tube diameter of the left tube 21, the tube diameter of the central tube 8, and the radius of the right tube 22 are R, the radius of the axis of the innermost annular tube in the annular tubes is R1, and the radius of the axis of the outermost annular tube is R2, so that the following requirements are met:

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 is 0.6214 and b is 1.3005.

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

Preferably, the number of annular tubes of the tube set is 3-5, 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 10-40 mm; preferably 15 to 35mm, more preferably 20 to 30 mm.

Preferably, the centers of the left tube 21, the right tube 22 and the center tube 8 are on a straight line.

Preferably, the arc between the ends of the free ends 3, 4 around the centre axis of the left tube is 95-130 degrees, preferably 120 degrees. The same applies to the curvature of the free ends 5, 6 and the free ends 3, 4. Through the design of the preferable included angle, the vibration of the free end is optimal, and therefore the heating efficiency is optimal.

The first, second and third heat source heating powers are preferably 1000 to 2000W, and more preferably 1500W.

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

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

The heat exchange coefficient can be further improved by arranging the tube bundle of the tube group 1 with an elastic tube bundle.

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

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

The heat exchanger shown in fig. 6 has a circular cross-sectional housing in which the plurality of heat exchange members are disposed. Preferably, the number of the heat exchange components is three, the center of the central tube of each heat exchange component is located at the midpoint of an inscribed regular triangle of the circular cross section, the connecting lines of the centers of the central tubes form the regular triangle, one heat exchange component is arranged at the upper part of each central tube, two heat exchange components are arranged at the lower part of each central tube, and the connecting lines formed by the left side tube, the right side tube and the centers of the central tubes of the heat exchange components are of a parallel structure. Through such setting, can make and to fully reach vibrations and heat transfer purpose in can making the heater, improve the heat transfer effect.

Learn through numerical simulation and experiment, heat transfer part's size and circular cross-section's diameter have very big influence to the heat transfer effect, heat transfer part size too big can lead to adjacent interval too little, the space that the centre formed is too big, middle heating effect is not good, the heating is inhomogeneous, on the same way, heat transfer part size undersize can lead to adjacent interval too big, leads to whole heating effect not good. Therefore, the invention obtains the optimal size relation through a large amount of numerical simulation and experimental research.

The distance between the centers of the left side pipe and the right side pipe is L1, the side length of the inscribed regular triangle is L2, the radius of the axis of the innermost annular pipe in the annular pipes is R1, and the radius of the axis of the outermost annular pipe is R2, so that the following requirements are met:

10*(L1/L2)=d*(10*R1/R2)-e*(10*R1/R2)²-f; wherein d, e, f are parameters,

44.102<d<44.110,3.715<e<3.782,127.385<f<127.395；

further preferably, d =44.107, e =3.718, f = 127.39;

with 720< L2<1130mm preferred. Preferably 0.58< R1/R2< 0.62.

Further preferred is 0.30< L1/L2< 0.4.

Through the layout of the three heat exchange component structure optimization, the whole heat exchange effect can reach the best heat exchange effect.

It has been found in research and practice that a constant and stable heat source results in a fluid-forming stability of the internal heat exchange components, i.e. the fluid is not flowing or is less fluid, or the flow is stable, resulting in a significantly reduced vibration performance of the tube bank 1, which affects the efficiency of the descaling and heating of the tube bank 1. Therefore, the following improvements are required for the heat pipe.

Preferably, the first and

third heat sources

91 and 93 and the second heat source 92 are periodically and alternately heated with time.

As shown in fig. 3, in one cycle time T, the heating powers of the first heat source and the third heat source are P1 and P3, the heating power of the second heat source is P2, and the change rule of P1, P2 and P3 is as follows:

in a half period of 0-T/2, P1 is equal to n, P2 is equal to 0, and P3 is equal to n, namely the heating power of the first heat source and the third heat source is kept constant, and the second heat source does not heat;

and in the half period of T/2-T, P1=0, P2= m and P3=0, namely the first heat source and the third heat source do not heat, 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 P1 and P3, the heating power of the second heat source is P2, and the change rule of P1, P2 and P3 is as follows:

in a half period of 0-T/2, P2 is m, P1=0, P3=0, wherein n is a constant value and is in the unit of watt (W), namely the heating power of the first heat source and the third heat source is kept constant, and the second heat source does not heat;

half a period of T/2-T, P2=0, P1= n; p3= n; namely, the first heat source does not heat, and the heating power of the second and third heat sources is kept constant.

Wherein m and n are constant values and have the unit of watt (W). Preferably, m =2 n.

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

Through the heating with the time variability, the fluid can be frequently evaporated and expanded in the elastic tube bundle, and the stability of single heating is damaged due to the continuous periodic change of the expansion and the flowing direction of the steam, so that the vibration of the elastic tube bundle is continuously driven, and the heating efficiency and the descaling operation can be further realized.

Compared with the prior application, the heating mode ensures that the heat exchange component is heated in the whole period, and the elastic tube bundle can vibrate frequently, so that the heating efficiency and the descaling operation can be further realized.

Preferably, the first heat source 91, the second heat source 92 and the third heat source 93 are respectively provided as a plurality of electric heating parts, each of which is independently controlled, and the number of the electric heating parts that are activated is periodically changed with time.

Preferably, the first heat source 91, the second heat source 92 and the third heat source 93 are all provided with n electric heating parts, and if T =0, all the n electric heating parts of the first heat source 91 and the third heat source 93 are turned off and all the n electric heating parts of the second heat source 92 are turned on in a half cycle of 0-T/2 if T is a cycle T;

then, one electric heating part is respectively started by the first heat source 91 and the third heat source 93 every T/2n, one electric heating part is stopped by the second heat source 92, and the first heat source 91 and the third heat source 93 are all started and the second heater is all stopped until T/2.

In a half period of T/2-T, every T/2n, the second heat source 92 starts an electric heating part, and simultaneously the first heat source 91 and the third heat source 93 respectively stop one electric heating part until the period T is finished, the second heat source is completely started, and the first heat source and the third heat source are completely stopped.

Preferably, each of the electric heating parts in the first heat source and the third heat source has the same heating power. The power of each electric heating part of the second heat source is twice that of the first and third heat source electric heating parts. The relationship diagram is shown in fig. 4.

Alternatively, if a period is T, then in a half period of 0-T/2, when T =0, all n of the second heat sources 92 are turned off, and all n of the first heat sources 91 are turned on;

then every T/2n time, the second heat source 92 starts an electric heating part, and simultaneously the first heat source 91 and the third heat source 93 stop an electric heating part, until the T/2 time, the second heater is started, and the first heater and the third heat source are stopped.

In a half period of T/2-T, every T/2n, the first heat source 91 and the third heat source start one electric heating part, and the second heat source 92 stops one electric heating part at the same time, until the heating parts of the first heat source and the third heat source are all started in the period T, and the heating parts of the second heater are all closed.

Preferably, the

heat sources

91, 92, 93 are provided in a plurality of stages along the height direction of the tube shell, each stage is independently controlled, and as time changes, all the stages of the first heat source 91 and the third heat source 93 are turned off and all the stages of the second heat source 92 are turned on in a half cycle of 0-T/2 with T = 0;

then the first heat source 91 and the third heat source 93 are sequentially started along the opposite direction of the flow direction of the fluid in the shell pass (for example, the upper end of fig. 1 is started) until all the sections are started, and simultaneously the second heat source 92 is sequentially closed along the flow direction of the fluid in the shell pass until all the sections are closed;

in a half period of T/2-T, the first heat source 91 and the third heat source 93 start to be sequentially closed along the flow of the fluid in the shell pass, the second heat source 92 starts to be sequentially opened along the direction opposite to the flow of the fluid in the shell pass, and all the sections of the first heat source 91 and the third heat source 93 are completely closed and all the sections of the second heat source 92 are completely opened until the period is finished.

That is, assuming that the first heat source 91, the second heat source 92, and the third heat source 93 are all n segments, all the segments of the first heat source 91 and the third heat source 93 are all turned off, and all the segments of the second heat source 92 are all turned on when T =0 in one period T;

then every T/2n time, starting a section by the first heat source 91 and the third heat source 93 from the direction opposite to the flowing direction of the fluid in the shell pass, simultaneously starting a section by the second heat source 92 from the flowing direction of the fluid in the shell pass, and stopping all the sections of the first heat source 91 and the third heat source 93 until the T/2 time, and stopping all the sections of the second heat source 92;

then every T/2n time, the first heat source 91 and the third heat source 93 start from the flowing direction of the fluid in the shell pass, and are closed for a section every T/2n time, meanwhile, the second heat source starts from the flowing direction of the fluid in the shell pass, and is opened for a section every T/2n time until all the sections of the first heat source and the third heat source are closed and all the sections of the second heat source are opened at T time.

Alternatively, in a half cycle of 0-T/2, when T =0, all the segments of the first and

third heat sources

91 and 93 are all turned on, and all the segments of the second heat source 92 are all turned off; then the first heat source 91 and the third heat source 93 are sequentially closed along the flowing direction of the fluid in the shell pass until all the sections are closed, and simultaneously the second heat source 92 is sequentially opened along the direction opposite to the flowing direction of the fluid in the shell pass until all the sections are opened;

in a half period of T/2-T, the second heat source 92 is turned off sequentially from the upper end, the first heat source 91 and the third heat source 93 are turned on sequentially from the opposite direction of the fluid flow direction in the shell side, all the sections of the second heat source 92 are turned off until the period is finished, and all the sections of the first second heat source 91 and the third heat source 93 are turned on.

That is, if the first heat source 91, the second heat source 92, and the third heat source 93 are all n segments, in one period T, when T =0, all the segments of the second heat source 92 are all turned off, and all the segments of the first heat source 91 and the third heat source 93 are all turned on;

then every T/2n time, starting a section from the direction opposite to the flowing direction of the fluid in the shell pass by the second heat source 92, and simultaneously starting closing a section from the flowing direction of the fluid in the shell pass by the first heat source 91 and the third heat source 93 until all the sections of the second heat source 92 are completely started and all the sections of the first heat source 91 and the third heat source 93 are completely closed at the T/2 time;

then every T/2n time, the second heat source starts from the flowing direction of the fluid in the shell side, and is closed every T/2n time, meanwhile, the first heat source and the third heat source 93 start from the opposite direction of the flowing direction of the fluid in the shell side, and are opened every T/2n time until all the sections of the second heat source are closed at T time, and all the sections of the first heat source and the third heat source 93 are opened.

Preferably, the heating power of each of the first and third heat sources 93 is the same. The second heat source has twice the heating power per segment as the first and third heat sources 93. 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 heating temperature at the upper end is high, a similar counter-flow effect is formed, the fluid flow is further promoted, and the elastic vibration effect is increased. Through the change of the heating power with time variability, the fluid can be frequently evaporated, expanded and contracted in the elastic tube bundle, so that the vibration of the elastic tube bundle is continuously driven, and the heating efficiency and the descaling operation can be further realized.

Preferably, the first heat source 91 is provided in plural, each heat source 91 has different power, and may be combined by one or more of them to form different heating power, and the second heat source 92 is provided in plural, and each heat source 92 has different power. The third heat source 93 is provided in plural, each heat source has different power, and one or more of the heat sources can be combined to form different heating power

In the period T, T =0, all of the plurality of first heat sources 91 and the plurality of first heat sources 93 are turned off, all of the plurality of second heat sources 92 are turned on,

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

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

simultaneously, closing a single second heat source, independently closing the single second heat source according to the sequence of sequentially increasing the heating power, then closing two second heat sources, independently closing the two second heat sources according to the sequence of sequentially increasing the heating power, then gradually increasing the number of closed second heat sources, and if the number is n, independently closing the n second heat sources according to the sequence of sequentially increasing the heating power; and ensuring that the heating power of the second heat sources is reduced in sequence until all the second heat sources are closed finally.

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

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

Meanwhile, according to the time sequence, firstly, a single second heat source is started, the single second heat source is independently started according to the sequence that the heating power is sequentially increased, then two second heat sources are started, the two second heat sources are independently started according to the sequence that the heating power is sequentially increased, then the starting number of the second heat sources is gradually increased, and if the number is n, the n second heat sources are independently started according to the sequence that the heating power is sequentially increased; until all the second heat sources are started up, the heating power of the second heat sources is ensured to be increased in sequence

For example, the number of the first heat sources is three, the first heat source D1, the first heat source D2 and the first heat source D3 respectively, and the heating powers are P1, P2 and P3 respectively, wherein P1< P2< P3, P1+ P2> P3; that is, the sum of D1 and D2 is larger than D3, D1, D2, D3, D1 plus D2, D1 plus D3, D2 plus D3, then D1+ D2+ D3 are sequentially started in time sequence in the first half period, and the closing sequence in the second half period is D1, D2, D3, D1 plus D2, D1 plus D3, D2 plus D3.

The number of the third heat sources is three, namely a first heat source D4, a first heat source D5 and a first heat source D6, the heating power is P4, P5 and P6, wherein P4< P5< P6, P4+ P5> P6; that is, the sum of D4 and D5 is larger than D6, D4, D5, D6, D4 plus D5, D4 plus D6, D5 plus D6, then D4+ D5+ D6 are sequentially started in time sequence in the first half period, and the closing sequence in the second half period is D4, D5, D6, D4 plus D5, D4 plus D5, D5 plus D6.

The number of the second heat sources is three, namely a second heat source M1, a second heat source M2 and a second heat source M3, and the heating power is P1, P2 and P3, wherein P1< P2< P3, P1+ P2> P3; that is, the sum of M1 and M2 is greater than M3, M1, M2, M3, M1 plus M2, M1 plus M3, M2 plus M3, then M1+ M2+ M3 are sequentially closed in time sequence in the first half period, and the opening sequence in the second half period is M1, M2, M3, M1 plus M2, M1 plus M3, M2 plus M3.

Alternatively, in the period T, T =0, all of the plurality of second heat sources 92 are turned off, all of the plurality of first heat sources 91 and third heat sources 93 are turned on,

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

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

For example, the number of the second heat sources is three, and the second heat source is D1, D2 and D3, and the heating powers are P1, P2 and P3, wherein P1< P2< P3, P1+ P2> P3; that is, the sum of D1 and D2 is larger than D3, D1, D2, D3, D1 plus D2, D1 plus D3, D2 plus D3, then D1+ D2+ D3 are sequentially started in time sequence in the first half period, and the closing sequence in the second half period is D1, D2, D3, D1 plus D2, D1 plus D3, D2 plus D3.

The number of the first heat sources is three, namely a first heat source M1, a first heat source M2 and a first heat source M3, and the heating power is P1, P2 and P3, wherein P1< P2< P3, P1+ P2> P3; that is, the sum of M1 and M2 is greater than M3, M1, M2, M3, M1 plus M2, M1 plus M3, M2 plus M3, then M1+ M2+ M3 are sequentially closed in time sequence in the first half period, and the opening sequence in the second half period is M1, M2, M3, M1 plus M2, M1 plus M3, M2 plus M3.

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 P1, P2 and P3, wherein P1< P2< P3, P1+ P2> P3; namely, the sum of K1 and K2 is larger than K3, K1, K2, K3, K1 plus K2, K1 plus K3, K2 plus K3, then K1+ K2+ K3 are sequentially closed in the first half period according to the time sequence, and the K1, K2, K3, K1 plus K2, K1 plus K3, K2 plus K3 are sequentially opened in the second half period.

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

Preferably, the heating power of the heat source is linearly increased in the first half cycle, and the heating power of the heat exchanging member is linearly decreased in the second half cycle.

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 the heat sources with gradually increased number 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 heat exchange part 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 tube, the right tube and the middle tube are connected in 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. The pipe diameter of the middle pipe is preferably 1.4-1.5 times of the pipe diameter of the left side pipe and the right side pipe. Through the pipe diameter setting of left side pipe, right side pipe and intermediate pipe, can guarantee that the fluid carries out the phase transition and keeps the same or close transmission speed at left side pipe, right side pipe and intermediate pipe to guarantee the homogeneity of conducting heat.

Preferably, the connection position of the coil pipe at the left channel box is lower than the connection position of the middle channel box and the coil pipe. This ensures that steam can rapidly enter the intermediate header. Similarly, the connecting position of the coil pipe at the right channel box is lower than the connecting position of the middle channel box and the coil pipe.

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 gas shell-and-tube heat exchanger with a heat source height controlled comprises a shell, a heat exchange component, a shell side inlet connecting pipe and a shell side outlet connecting pipe; the shell pass inlet connecting pipe and the shell pass outlet connecting pipe are respectively positioned at the upper end and the lower end of the heat exchanger; the heat exchange component is arranged in the shell and fixedly connected to the upper tube plate and the lower tube plate; the shell pass inlet connecting pipe and the shell pass outlet connecting pipe are both arranged on the shell; gas enters from the shell side inlet connecting pipe, exchanges heat through the heat exchange part and exits from the shell side outlet connecting pipe; the heat exchange component comprises a central tube, a left tube, a right tube and a tube group, wherein the tube group comprises a left tube group and a right tube group, the left tube group is communicated with the left tube 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 heating fluid closed circulation, the left tube and/or the central tube and/or the right tube are filled with 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, the first heat source, the second heat source and the third heat source are arranged into multiple sections along the height direction, each section is independently controlled, the first heat source, the second heat source and the third heat source are respectively n sections, all the sections of the first heat source and the third heat source are all closed, and all the sections of the second heat source are all opened when T =0 in a period T;

2. The heat exchanger of claim 1, wherein each tube group comprises a plurality of annular tubes in the shape of circular arcs, the ends of adjacent annular tubes communicate such that the plurality of annular tubes form a series arrangement, and such that the ends of the annular tubes form the free ends of the annular 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; 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 or not; the first pipe orifice and the second pipe orifice are arranged on two opposite sides of the central pipe; the position of the right tube group is a position of the left tube group rotated by 180 degrees along the axis of the center tube.

3. The heat exchanger of claim 1, wherein the annular tubes of the left tube set are centered on the axis of the left tube and the annular tubes of the right tube set are centered on the axis of the right tube.

4. A shell-and-tube heat exchanger is characterized by comprising a plurality of circular arc-shaped annular tubes, wherein the end parts of the adjacent annular tubes are communicated, so that the annular tubes form a series structure.