CN111928696B

CN111928696B - Flow rate control shell-and-tube heat exchanger

Info

Publication number: CN111928696B
Application number: CN201910394042.0A
Authority: CN
Inventors: 冷学礼; 朱玉熙; 魏民; 于耀; 刘磊; 孙晨; 邱燕; 张冠敏; 柏超; 田茂诚; 张井志
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2019-05-13
Filing date: 2019-05-13
Publication date: 2022-04-05
Anticipated expiration: 2039-05-13
Also published as: CN111928696A

Abstract

The invention provides a shell-and-tube heat exchanger which comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, a speed detection element is arranged in the free end of a tube bundle and used for detecting the flow speed of fluid in the free end of the tube bundle, the speed detection element is in data connection with a controller, and the controller controls whether an electric heater is used for heating or not according to the detected speed of the fluid. The heat exchanger can judge whether the stable state is achieved or not according to the speed field, and then intelligently controls the heating of the electric heater according to the speed field, so that the frequent vibration of the fluid in the heat exchanger can be realized, and good descaling and heating effects can be realized.

Description

Flow rate control shell-and-tube heat exchanger

Technical Field

The invention relates to a shell-and-tube heat exchanger, in particular to a shell-and-tube heat exchanger for intermittent vibration descaling.

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. There is therefore a need for improvements to the above-described heat exchangers. In this regard, we have developed a new shell-and-tube heat exchanger capable of generating periodic vibration, and have already filed patent applications.

However, in practice it has been found that adjusting the vibration of the tube bundle by a fixed periodic variation can result in hysteresis and excessively long or short periods. Therefore, the invention improves the previous application and intelligently controls the vibration, so that the fluid in the fluid can realize frequent vibration, and good descaling and heating effects can be realized.

Disclosure of Invention

The invention provides a novel shell-and-tube heat exchanger capable of intelligently controlling vibration for overcoming the defects in the prior art, and the shell-and-tube heat exchanger can realize frequent vibration of a heat exchange tube and improve the heating efficiency, thereby realizing good descaling and heating effects.

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

a shell-and-tube heat exchanger comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, a heat replacement component is arranged in the shell, the heat exchange component comprises a lower tube box, an upper tube box and a heat exchange tube, the heat exchange tube is communicated with the lower tube box and the upper tube box to form closed circulation of heating fluid, two ends of the lower tube box and the upper tube box are arranged in openings of the tube plates, and an electric heater is arranged in the lower tube box; filling phase-change fluid in the lower channel box; the heat exchange tubes are one or more, each heat exchange tube comprises a plurality of arc-shaped tube bundles, the central lines of the arc-shaped tube bundles are arcs with the following tube boxes as concentric circles, the end parts of the adjacent tube bundles are communicated, so that the end parts of the tube bundles form tube bundle free ends, speed detection elements are arranged in the tube bundle free ends and used for detecting the flow velocity of fluid in the tube bundle free ends, the speed detection elements are in data connection with a controller, and the controller controls whether the electric heater heats or not according to the detected speed of the fluid.

Preferably, the controller controls the electric heater to stop heating if the speed detected by the speed detecting element is higher than a certain value. The liquid level detected by the speed detection element is lower than a certain value, and the controller controls the electric heater to heat.

The invention has the following advantages:

1. the heat exchanger can judge whether the stable state is achieved or not according to the speed field, and then intelligently controls the heating of the electric heater according to the speed field, so that the frequent vibration of the fluid in the heat exchanger can be realized, and good descaling and heating effects can be realized.

2. The invention designs a layout of a heat exchange component with a novel structure in the shell, and can further improve the heating efficiency.

3. The invention optimizes the optimal relation of the parameters of the heat exchange tube through a large amount of experiments and numerical simulation, thereby realizing the optimal heating efficiency.

4. Through the flowing direction of fluid in the shell, the reasonable change of the internal diameter and the interval of the tube bundle of the heat exchange tube improves the heat exchange efficiency.

Description of the drawings:

FIG. 1 is a top view of a heat exchange member of the present invention.

Fig. 2 is a front view of the heat exchange part.

Fig. 3 is a layout diagram of heat exchange components arranged in a circular shell.

Fig. 4 is a schematic view of the structure of a heat exchange tube.

Fig. 5 is a schematic view of the housing structure.

FIG. 6 is a schematic of a pressure controlled descaling flow.

In the figure: 1. the heat exchange tube comprises a heat exchange tube body 2, a lower tube box 3, a free end 4, a free end 5, a shell pass inlet connecting tube 6, a shell pass outlet connecting tube 7, a free end 8, an upper tube box 9, a connecting point 10, a heat exchange part 11, a shell body 12, a tube bundle 12, an electric heater 13, a front tube plate 14, a support 15, a support 16, a rear tube plate 17 and end parts 18-20

Detailed Description

A shell-and-tube heat exchanger, as shown in fig. 5, the shell-and-tube heat exchanger includes a shell 11, a heat exchange component 10, a shell-side inlet connection pipe 5, and a shell-side outlet connection pipe 6; the heat exchange component 10 is arranged in the shell 11 and fixedly connected to the front tube plate 14 and the rear tube plate 17; the shell side inlet connecting pipe 5 and the shell side outlet connecting pipe 6 are both arranged on the shell 11; fluid enters from a shell side inlet connecting pipe 5, exchanges heat through a heat exchange part and exits from a shell side outlet connecting pipe 6.

The end parts 18-20 at both ends of the lower and upper tube boxes are arranged in the openings of the front and

rear tube plates

14, 17 for fixation.

Fig. 1 shows a top view of a heat exchange part 10, as shown in fig. 1, the heat exchange part 10 includes a lower tube box 2, an upper tube box 8 and a heat exchange tube 1, the heat exchange tube 1 is communicated with the lower tube box 2 and the upper tube box 8, a fluid is circulated in the lower tube box 2, the upper tube box 8 and the heat exchange tube 1 in a closed manner, an electric heater 13 is arranged in the heat exchange part 10, the electric heater 13 is used for heating the fluid in the heat exchange part 10, and then the fluid in the shell is heated by the heated fluid.

As shown in fig. 1-2, an electric heater 13 is provided in the lower header tank 2; the lower tube box 2 is filled with phase-change fluid; the heat exchange tubes 1 are one or more, each heat exchange tube 1 comprises a plurality of circular arc-shaped tube bundles 12, the central lines of the circular arc-shaped tube bundles 12 are circular arcs which are concentric with the lower tube box 2, the end parts of the adjacent tube bundles 12 are communicated, and fluid forms serial flow between the lower tube box 2 and the upper tube box 8, so that the end parts of the tube bundles form tube bundle

free ends

3 and 4; the fluid is phase-change fluid, vapor-liquid phase-change liquid, the heat exchange component is in data connection with the controller, and the controller controls the heating power of the heat exchange component to periodically change along with the change of time.

Preferably, the lower header 2 and the upper header 8 are provided along the length of the shell side. The shell side preferably extends in the horizontal direction.

It has been found in research and practice that the continuous power-stable heating of the electric heater can result in the stability of the fluid formation of the internal heat exchange components, i.e. the fluid is not flowing or has little fluidity, or the flow rate is stable, and the vibration performance of the heat exchange tube 1 is greatly weakened, thereby affecting the descaling of the heat exchange tube 1 and the heating efficiency. Therefore, the following improvements are required for the above-mentioned electric heating heat exchange pipe.

In the prior application of the inventor, a periodic heating mode is provided, and the vibration of the heat exchange pipe is continuously promoted by the periodic heating mode, so that the heating efficiency and the descaling effect are improved. However, adjusting the vibration of the tube bundle with a fixed periodic variation can lead to hysteresis and too long or too short a period. Therefore, the invention improves the previous application and intelligently controls the vibration, so that the fluid in the fluid can realize frequent vibration, and good descaling and heating effects can be realized.

Aiming at the defects in the technology researched in the prior art, the invention provides a novel electric heating water heater capable of intelligently controlling vibration. This water heater can improve heating efficiency to realize fine scale removal and heating effect.

Self-regulation vibration based on pressure

Preferably, a pressure detection element is arranged in the heat exchange component and used for detecting the pressure in the heat exchange component, the pressure detection element is in data connection with the controller, and the controller controls whether the electric heater heats or not according to the detected pressure.

Preferably, the controller controls the electric heater to stop heating if the pressure detected by the pressure detecting element is higher than a certain value, and controls the electric heater to heat if the pressure detected by the pressure detecting element is lower than a certain value.

The pressure detected by the pressure detecting element can basically reach saturation when the certain pressure is met, and the volume of the internal fluid is not changed greatly basically. So that the fluid undergoes volume reduction to thereby realize vibration. When the pressure is reduced to a certain degree, the internal fluid starts to enter a stable state again, and at the moment, the fluid needs to be heated so as to evaporate and expand again, so that the electric heater needs to be started for heating.

Preferably, the pressure detecting element is provided in the lower header 2 and/or the upper header 8.

Preferably, the pressure detecting elements are provided in the lower and

upper headers

2 and 8. The average of the pressures of the two headers can be selected as regulating data.

Preferably, the pressure detecting element is provided at the free end. Through setting up at the free end, can perceive the pressure variation of free end to realize better control and regulation.

Independently adjusting vibration based on temperature

Preferably, a temperature detection element is arranged in the heat exchange component and used for detecting the temperature in the heat exchange component, the temperature detection element is in data connection with the controller, and the controller controls whether the electric heater heats or not according to the detected temperature.

Preferably, the controller controls the electric heater to stop heating if the temperature detected by the temperature detecting element is higher than a certain value, and controls the electric heater to heat if the temperature detected by the temperature detecting element is lower than a certain value.

The pressure detected by the temperature detection element can basically saturate the evaporation of the internal fluid and the volume of the internal fluid is not changed greatly under the condition of meeting a certain temperature, and in this case, the internal fluid is relatively stable, so that the vibration of the tube bundle is poor, and adjustment is needed to vibrate the tube bundle so as to stop heating. So that the fluid undergoes volume reduction to thereby realize vibration. When the temperature is reduced to a certain degree, the internal fluid starts to enter a stable state again, and the fluid needs to be heated to evaporate and expand again, so that the electric heater needs to be started for heating.

Preferably, the temperature sensing element is provided at an upper end in the lower and/or upper header.

Preferably, the temperature detection element is provided at an upper end in the lower and upper headers.

Preferably, the temperature detection element is provided at the free end. Through setting up at the free end, can perceive the temperature variation of free end to realize better control and regulation.

Thirdly, automatically adjusting vibration based on liquid level

Preferably, a liquid level detection element is arranged in the lower pipe box and used for detecting the liquid level of the fluid in the lower pipe box, the liquid level detection element is in data connection with the controller, and the controller controls whether the electric heater heats or not according to the detected liquid level of the fluid.

Preferably, the controller controls the electric heater to stop heating if the liquid level detected by the liquid level detecting element is lower than a certain value. The liquid level detected by the liquid level detection element is higher than a certain value, and the controller controls the electric heater to heat.

The liquid level detected by the liquid level detecting element can be adjusted to vibrate the tube bundle so as to stop heating under the condition that a certain liquid level (for example, the lowest limit) is met, the evaporation of the internal fluid is basically saturated, and the volume of the internal fluid is basically not changed greatly. So that the fluid undergoes volume reduction to thereby realize vibration. When the liquid level rises to a certain degree, the internal fluid starts to enter a stable state again, and at the moment, the fluid needs to be heated so as to evaporate and expand again, so that the electric heater needs to be started for heating.

Fourthly, automatically adjusting vibration based on speed

Preferably, a speed detection element is arranged in the free end of the tube bundle and used for detecting the flow speed of the fluid in the free end of the tube bundle, the speed detection element is in data connection with the controller, and the controller controls whether the electric heater heats or not according to the detected speed of the fluid.

The speed detected by the speed detecting element can be adjusted to vibrate the tube bundle to stop heating, because the internal fluid is relatively stable and the tube bundle is deteriorated in vibration property in the case where the evaporation of the internal fluid is substantially saturated to form a stable flow and the speed of the internal fluid is not substantially changed when a certain speed (for example, the highest upper limit) is satisfied. So that the fluid undergoes volume reduction to thereby realize vibration. When the speed drops to a certain degree, the internal fluid starts to enter a stable state again, and at the moment, the fluid needs to be heated so as to evaporate and expand again, so that the electric heater needs to be started for heating.

Preferably, the pipe diameter of the lower pipe box 2 is smaller than that of the upper pipe box 8, and the pipe diameter of the lower pipe box 2 is 0.5-0.8 times of that of the upper pipe box 8. Through the pipe diameter change of lower tube case and upper tube case, can guarantee that the fluid carries out the phase transition and in the internal time of first box short, get into the heat exchange tube fast, fully get into the heat transfer of second box.

Preferably, the connection position 9 of the heat exchange tube at the lower tube box is lower than the connection position of the upper tube box and the heat exchange tube. This ensures that steam can rapidly enter the upper header.

Preferably, a return line is provided between the lower and upper headers, optionally at the ends 18-20 of the lower and upper headers, to ensure that condensed fluid in the upper header can enter the first line.

Preferably, the lower tube box and the upper tube box are arranged in the horizontal direction, the heat exchange tubes are arranged in a plurality along the flowing direction of the fluid in the shell side, and the tube diameter of the heat exchange tube bundle is continuously increased along the flowing direction of the fluid.

Preferably, the tube diameter of the heat exchange tube bundle is increased along the flowing direction of the fluid.

The pipe diameter range through the heat exchange tube increases, can guarantee that shell side fluid 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 heat exchange tubes are arranged in a plurality along the flowing direction of fluid in the shell side, and the distance between every two adjacent heat exchange tubes is gradually reduced along the flowing direction of the fluid.

Preferably, the interval between the heat exchange tubes becomes smaller and larger along the height direction of the lower header.

The interval amplitude through the heat exchange tube increases, can guarantee that shell side fluid 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.

Preferably, as shown in fig. 3, the casing is a casing with a circular cross section, and a plurality of heat exchange components are arranged in the casing.

Preferably, as shown in fig. 3, a plurality of heat exchange members are disposed in the housing, one of which is disposed in the center of the housing to become a central heat exchange member, and the others are distributed around the center of the housing to become peripheral heat exchange members. Through the structural design, the fluid in the shell can fully achieve the vibration purpose, and the heat exchange effect is improved.

Preferably, the heating power of the single peripheral heat exchange member is smaller than the heating power of the central heat exchange member. Through the design, the center reaches higher vibration frequency to form a central vibration source, so that the periphery is influenced, and better heat transfer enhancement and descaling effects are achieved.

Preferably, on the same horizontal heat exchange section, the fluid needs to achieve uniform vibration, and uneven heat exchange distribution is avoided. It is therefore necessary to distribute the amount of heating power among the different heat exchange members reasonably. Experiments show that the heating power ratio of the central heat exchange component to the peripheral tube bundle heat exchange component is related to two key factors, wherein one factor is related to the distance between the peripheral heat exchange component and the center of the shell (namely the distance between the circle center of the peripheral heat exchange component and the circle center of the central heat exchange component) and the diameter of the shell. Therefore, the invention optimizes the optimal proportional distribution of the pulsating flow according to a large number of numerical simulations and experiments.

Preferably, the radius of the inner wall of the shell is R, the center of the central heat exchange component is arranged at the center of the circular section of the shell, the distance from the center of the peripheral heat exchange component to the center of the circular section of the shell is S, the centers of adjacent peripheral heat exchange components are respectively connected with the center of the circular section, the included angle formed by the two connecting lines is a, the heating power of the peripheral heat exchange component is P2, and the heating power of a single central heat exchange component is P1, so that the following requirements are met:

P1/P2 ═ a-b ═ Ln (R/S); ln is a logarithmic function;

a, b are coefficients, wherein 2.0869< a <2.0875,0.6833< b < 0.6837;

preferably, 1.35< R/S < 2.1; further preferred is 1.4< R/S < 2.0;

preferably, 1.55< P1/P2< 1.9. Further preferred is 1.6< P1/P2< 1.8;

wherein 35 ° < a <80 °.

Preferably, the number of the four-side distribution is 4-5.

Preferably, R is 1600-2400 mm, preferably 2000 mm; s is 1150-1700 mm, preferably 1300 mm; the diameter of the heat exchange tube bundle is 12-20 mm, preferably 16 mm; the outermost diameter of the heat exchange tube is preferably 300-560 mm, preferably 400 mm. The tube diameter of the lower manifold is 100-116 mm, preferably 108 mm, and the length of the upper manifold and the lower manifold is 1.8-2.2 m.

The total heating power is preferably 5000-.

More preferably, a is 2.0872 and b is 0.6835.

Preferably, the box body is of a circular section, and is provided with a plurality of heat exchange components, wherein one heat exchange component is arranged at the center of the circle of the circular section, and the other heat exchange components are distributed around the center of the circle of the circular section. The heat exchange tubes 1 are in one group or multiple groups, each group of heat exchange tubes 1 comprises a plurality of circular arc-shaped tube bundles 12, the central lines of the circular arc-shaped tube bundles 12 are circular arcs of concentric circles, and the end parts of the adjacent tube bundles 12 are communicated, so that the end parts of the heat exchange tubes 1 form tube bundle free ends 3 and 4, such as the free ends 3 and 4 in fig. 2.

Preferably, the heating fluid is a vapor-liquid phase-change fluid.

Preferably, the lower header 2, the upper header 8 and the heat exchange tubes 1 are all of a circular tube structure.

Preferably, the tube bundle of the heat exchange tubes 1 is an elastic tube bundle.

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

Preferably, the concentric circles are circles centered around the center of the lower header 2. I.e., the tube bundle 12 of heat exchange tubes 1 is arranged around the center line of the lower header 2.

As shown in fig. 4, the tube bundle 12 is not a complete circle, but rather leaves a mouth, thereby forming the free end of the tube bundle. The angle of the arc of the mouth part is 65-85 degrees, namely the sum of included angles b and c in figure 4 is 65-85 degrees.

Preferably, the ends of the tube bundle on the same side are aligned in the same plane, with the extension of the ends (or the plane in which the ends lie) passing through the median line of the lower header 2.

Further preferably, the electric heater 13 is an electric heating rod.

Preferably, the first end of the inner tube bundle of the heat exchange tube 1 is connected with the lower tube box 2, the second end is connected with one end of the adjacent outer tube bundle, one end of the outermost tube bundle of the heat exchange tube 1 is connected with the upper tube box 8, and the end parts of the adjacent tube bundles are communicated, so that a series structure is formed.

The included angle c formed by the plane of the first end and the plane of the central lines of the lower pipe box 2 and the upper pipe box 8 is 40-50 degrees.

The included angle b formed by the plane of the second end and the plane of the central lines of the lower pipe box 2 and the upper pipe box 8 is 25-35 degrees.

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

As shown in fig. 4, the number of tube bundles of heat exchange tube 1 is 4, and tube bundles A, B, C, D are communicated. Of course, the number is not limited to four, and a plurality of the connecting structures are the same as that in fig. 4.

The heat exchange tubes 1 are multiple, the heat exchange tubes 1 are respectively and independently connected with the lower tube box 2 and the upper tube box 8, and the heat exchange tubes 1 are in parallel connection.

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 shell-and-tube heat exchanger comprises a shell, wherein tube plates are respectively arranged at two ends of the shell, a heat replacement component is arranged in the shell, the heat exchange component comprises a lower tube box, an upper tube box and a heat exchange tube, the heat exchange tube is communicated with the lower tube box and the upper tube box to form closed circulation of heating fluid, two ends of the lower tube box and the upper tube box are arranged in openings of the tube plates, and an electric heater is arranged in the lower tube box; filling phase-change fluid in the lower channel box; the heat exchange tube is characterized in that a speed detection element is arranged inside the free end of the tube bundle and used for detecting the flow velocity of fluid in the free end of the tube bundle, the speed detection element is in data connection with a controller, and the controller controls whether the electric heater heats according to the detected speed of the fluid, so that frequent vibration of the tube bundle can be realized, and good descaling and heating effects are realized.

2. The heat exchanger of claim 1, wherein the controller controls the electric heater to stop heating if the speed detected by the speed detecting element is higher than a certain value.