Eccentric arrangement double-side heating annular tube evaporator

Abstract

The invention relates to an eccentrically-arranged double-side heated annular pipe evaporator, and belongs to the technical field of evaporators. Comprising a shell, a heat exchange outer tube, a heat exchange inner tube and a tube plate, a shell pass inlet connecting pipe is arranged at one end of the shell, and a shell pass outlet connecting pipe is arranged at the other end; a heat exchange outer pipe is arranged in the shell, the two ends of the heat exchange outer pipe are each provided with a pipe plate, a distribution cavity is formed in each pipe plate, and the heat exchange outer pipe communicates with the distribution cavities. A tube pass inlet connecting pipe and a tube pass outlet connecting pipe are arranged on the shell; a heat exchange inner pipe is eccentrically arranged in the heat exchange outer pipe, and the two ends of the heat exchange inner pipe penetrate through the pipe plate. The inner pipe is eccentrically arranged, so that the two-phase friction resistance in the annular channel is effectively reduced, a water power multi-valued area is shortened, and the operation safety of equipment and a system is remarkably improved. Meanwhile, due to the double-side heating design, the heat distribution is more uniform, the local temperature difference is reduced, the flowing state of the working medium is further stabilized, and the flowing instability caused by uneven heat is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of evaporators, and in particular to an eccentrically arranged double-side heated annular tube evaporator. Background Art

[0002] In the field of energy utilization and industrial waste heat recovery, the Organic Rankine Cycle (ORC) system has been widely used in recent years because of its ability to efficiently convert medium and low temperature heat sources into electrical energy. As the core component of the ORC system, the performance of the evaporator directly determines the efficiency and stability of the entire system. However, the traditional shell and tube evaporator has a series of technical bottlenecks in practical applications, which seriously restricts its further development and promotion.

[0003] The main problem of traditional shell and tube evaporators is the phenomenon of hydrodynamic multi-value. Under two-phase flow conditions, when the total pressure drop of the system is within a specific range, the same pressure drop may correspond to multiple different working fluid mass flow rates. This multi-value will lead to extremely uneven flow distribution in different flow channels, which in turn will cause serious safety hazards such as local overheating, pressure fluctuations and even pipe bursts. The essence of hydrodynamic multi-value lies in the two-phase friction resistance (ΔP TP ) changes with the flow rate: in the low flow area, the rapid vaporization of the working fluid causes a sharp increase in the two-phase resistance; in the medium flow area, the flow pattern optimization may temporarily reduce the resistance; while in the high flow area, the single-phase resistance (ΔP SP ) becomes dominant again. This complex resistance characteristic causes the system to have multiple stable flow states under specific working conditions, which brings great challenges to the safe operation of the equipment.

[0004] In the existing technology, the following methods are mainly used to solve this problem: first, increase the system damping to suppress flow fluctuations, but this method can only alleviate the symptoms but cannot solve the problem; second, use compact designs such as microchannels, but this often leads to increased flow resistance and complex manufacturing processes; third, optimize the flow channel structure, but traditional symmetrical flow channel design is difficult to effectively improve the distribution characteristics of two-phase flow. These methods have failed to fundamentally solve the problem of hydrodynamic multi-values, but may introduce new technical difficulties. Summary of the invention

[0005] In order to solve or partially solve the problems existing in the related art, the present invention provides an eccentrically arranged double-sided heated annular tube evaporator, aiming to solve the adverse effects of hydrodynamic multi-values ​​on the performance and safety of the evaporator.

[0006] The above-mentioned eccentrically arranged double-side heated annular tube evaporator comprises a shell, a heat exchange outer tube, a heat exchange inner tube, and a tube sheet;

[0007] One end of the shell is provided with a shell-side inlet pipe, and the other end is provided with a shell-side outlet pipe;

[0008] The shell is provided with an outer heat exchange tube, and a tube sheet is provided at each end of the outer heat exchange tube, a distribution cavity is constructed in the tube sheet, and the outer heat exchange tube is communicated with the distribution cavity; the shell is provided with a tube side inlet pipe and a tube side outlet pipe, and the tube side inlet pipe and the tube side outlet pipe are respectively communicated with the distribution cavity in the two tube sheets;

[0009] An inner heat exchange tube is eccentrically arranged inside the outer heat exchange tube, and both ends of the inner heat exchange tube penetrate through the tube sheet.

[0010] In some embodiments, the relative eccentricity between the inner heat exchange tube and the outer heat exchange tube is 0 to 0.623.

[0011] In some embodiments, the difference between the diameter of the outer heat exchange tube and the diameter of the inner heat exchange tube is equal to 3%-10% of the outer diameter of the inner heat exchange tube.

[0012] In some schemes, at least three heat exchange outer tubes are provided between two tube sheets, and the heat exchange outer tubes are arranged in a compact triangle shape.

[0013] In some embodiments, the distance between two adjacent heat exchange outer tubes is equal to 1.2 to 1.5 times the outer diameter of the heat exchange outer tube.

[0014] In some embodiments, the inner wall of the outer heat exchange tube is provided with spiral stripes;

[0015] The inner wall and the outer wall of the heat exchange inner tube are provided with spiral stripes.

[0016] In some schemes, the upper part of one of the tube sheets is fixedly connected to the upper part of the shell, and a gap is provided between the lower part and the lower part of the shell; the lower part of the other tube sheet is fixedly connected to the lower part of the shell, and a gap is provided between the upper part and the upper part of the shell;

[0017] An upper baffle and a lower baffle are alternately arranged between the two tube sheets, the upper portion of the upper baffle is fixedly connected to the upper portion of the shell, and a gap is provided between the lower portion and the lower portion of the shell; the lower portion of the lower baffle is fixedly connected to the lower portion of the shell, and a gap is provided between the upper portion and the upper portion of the shell;

[0018] In this way, the tube sheet, the upper baffle plate and the lower baffle plate divide the internal cavity of the shell into a serpentine heat exchange channel.

[0019] In some embodiments, the spacing between the adjacent tube sheet and the upper baffle, the upper baffle and the lower baffle, and the lower baffle and the tube sheet is equal to 1 / 5 to 1 / 3 of the length of the outer heat exchange tube.

[0020] The technical solution provided by the present invention may include the following beneficial effects:

[0021] The present invention effectively reduces the two-phase friction resistance in the annular channel by eccentrically arranging the inner tube, thereby shortening the hydrodynamic multi-value zone and significantly improving the operating safety of the equipment and system. At the same time, the double-sided heating design makes the heat distribution more uniform, reduces the local temperature difference, further stabilizes the flow state of the working fluid, and reduces the flow instability caused by uneven heat.

[0022] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0024] Figure 1 is a schematic structural diagram of an evaporator shown in an embodiment of the present invention;

[0025] Figure 2 is another structural schematic diagram of an evaporator shown in an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the flow of a heat source in an evaporator according to an embodiment of the present invention;

[0027] Figure 4 is a schematic diagram of the flow of a cold source in an evaporator shown in an embodiment of the present invention;

[0028] Figure 5 The hydrodynamic characteristics diagram of the eccentrically arranged double-side heated annular tube evaporator described in the present application and the traditional shell and tube evaporator under the same working conditions;

[0029] Reference numerals:

[0030] 1. Shell; 2. Heat exchange outer tube; 3. Heat exchange inner tube; 4. Tube sheet; 401. Distribution chamber; 5. Shell side inlet pipe; 6. Shell side outlet pipe; 7. Tube side inlet pipe; 8. Tube side outlet pipe; 9. Upper baffle; 10. Lower baffle. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the described contents.

[0032] like Figure 1 and Figure 2As shown, the present application provides an eccentrically arranged double-side heated annular tube evaporator, comprising a shell 1, a heat exchange outer tube 2, a heat exchange inner tube 3, and a tube sheet 4; the shell 1 comprises a main body and end covers arranged at both ends of the main body, and the end covers are connected to the main body by bolts to facilitate the installation and removal of the end covers.

[0033] A shell-side inlet pipe 5 is provided at one end of the shell 1, and a shell-side outlet pipe 6 is provided at the other end; a heat exchange outer tube 2 is provided in the shell 1, and the heat exchange outer tube 2 is arranged along the length direction of the shell 1, and a tube sheet 4 is provided at each end of the heat exchange outer tube 2, and a distribution cavity 401 is constructed in the tube sheet 4, and the heat exchange outer tube 2 is communicated with the distribution cavity 401; a tube-side inlet pipe 7 and a tube-side outlet pipe 8 are provided on the shell 1, and one end of the tube-side inlet pipe 7 and the tube-side outlet pipe 8 both extend into the shell 1, and are respectively connected to one of the tube sheets 4, and are communicated with the distribution cavity 401 in the corresponding tube sheet 4.

[0034] The heat exchange inner tube 3 is eccentrically arranged inside the heat exchange outer tube 2 , thereby dividing the internal cavity of the heat exchange outer tube 2 into an eccentric annular flow channel. Both ends of the heat exchange inner tube 3 penetrate the tube sheet 4 and are not connected to the distribution cavity 401 .

[0035] When using, Figure 3 and Figure 4 As shown, the heat source enters the shell 1 through the shell inlet pipe 5, and then a part of the heat source flows to the other end of the shell 1 through the heat exchange inner tube 3, and the other part flows to the other end of the shell 1 through the gap between the adjacent heat exchange outer tubes 2 and the gap between the heat exchange outer tube 2 and the inner side of the shell 1, and finally flows out from the shell outlet pipe 6;

[0036] The cold source enters the distribution cavity 401 through the tube side inlet pipe 7, and is then introduced into the eccentric annular flow channel of the heat exchange outer tube 2, then flows into the distribution cavity 401 of the other tube sheet 4, and finally flows out from the tube side outlet pipe 8.

[0037] When the cold source is in the eccentric annular flow channel, it exchanges heat with the heat source in the heat exchange inner tube 3 and the heat source outside the heat exchange outer tube 2, forming a double-sided heating effect, effectively improving the heat exchange efficiency of the evaporator.

[0038] In this embodiment, the relative eccentricity between the heat exchange inner tube 3 and the heat exchange outer tube 2 is 0 to 0.623; an asymmetric annular channel is formed between the heat exchange inner tube 3 and the heat exchange outer tube 2. The heat exchange inner tube 3 is eccentrically arranged downward to reduce the top gas phase velocity in the initial boiling stratified flow, while increasing the bottom liquid phase velocity, reducing the gas-liquid slip velocity, and thereby reducing the two-phase friction resistance, thereby effectively shortening the hydrodynamic multi-value zone in the heat exchange tube.

[0039] In this embodiment, the difference between the diameter of the heat exchange outer tube 2 and the diameter of the heat exchange inner tube 3 is equal to 3%-10% of the outer diameter of the heat exchange inner tube 3, so as to avoid the problem of flow blockage caused by too narrow flow channel and gas-liquid stratification caused by too wide flow channel, and ensure the turbulent effect of the working fluid flow.

[0040] In some specific embodiments, at least three heat exchange outer tubes 2 are provided between the two tube sheets 4, and the heat exchange outer tubes 2 are arranged in a compact triangle shape, which is beneficial to improving the heat exchange efficiency of the evaporator.

[0041] In this specific embodiment, the distance between two adjacent heat exchange outer tubes 2 is equal to 1.2 to 1.5 times the outer diameter of the heat exchange outer tube 2, so as to ensure uniform distribution of shell-side fluid and improve heat exchange efficiency.

[0042] In some specific embodiments, the inner wall and the outer wall of the heat exchange inner tube 3 are smoothly arranged, and the inner wall and the outer wall of the heat exchange outer tube 2 are smoothly arranged, which is beneficial to the flow resistance of the liquid.

[0043] In some specific embodiments, the heat exchange inner tube 3 and the heat exchange outer tube 2 are both made of high-pressure resistant and corrosion-resistant stainless steel materials, and the inner wall of the heat exchange outer tube 2 is provided with spiral stripes; the inner wall and outer wall of the heat exchange inner tube 3 are provided with spiral stripes (not shown in the figure) to enhance the turbulence near the wall, thereby improving the heat exchange effect of the evaporator.

[0044] In some specific embodiments, Figure 3 and Figure 4 As shown, the upper part of one of the tube sheets 4 is fixedly connected to the upper part of the shell 1, and a gap is provided between the lower part and the lower part of the shell 1; the lower part of the other tube sheet 4 is fixedly connected to the lower part of the shell 1, and a gap is provided between the upper part and the upper part of the shell 1;

[0045] An upper baffle 9 and a lower baffle 10 are alternately arranged between the two tube sheets 4, the upper portion of the upper baffle 9 is fixedly connected to the upper portion of the shell 1, and a gap is provided between the lower portion and the lower portion of the shell 1; the lower portion of the lower baffle 10 is fixedly connected to the lower portion of the shell 1, and a gap is provided between the upper portion and the upper portion of the shell 1;

[0046] In this way, the tube sheet 4, the upper baffle plate 9 and the lower baffle plate 10 divide the internal cavity of the shell 1 into a serpentine heat exchange channel.

[0047] During operation, part of the heat flows from one end of the shell 1 to the other end through the serpentine heat exchange channel, which is beneficial to improving the heat exchange uniformity between the heat exchange outer tube 2 and the external heat source.

[0048] In this specific embodiment, the spacing between the adjacent tube sheets 4 and the upper baffle 9, the upper baffle 9 and the lower baffle 10, and the lower baffle 10 and the tube sheet 4 is equal to 1 / 5 to 1 / 3 of the length of the heat exchange outer tube 2, so as to take into account the uniformity of fluid distribution and the shell-side pressure drop control, and at the same time play the role of supporting the heat exchange outer tube 2.

[0049] like Figure 5 As shown, the solid line is the hydrodynamic characteristic curve of the traditional shell and tube evaporator, and the dotted line is the hydrodynamic characteristic curve of the eccentrically arranged double-sided heated annular tube evaporator described in this application. It can be seen from the figure that when the total pressure drop of the evaporator is within the range, the traditional shell and tube evaporator corresponds to multiple mass flow rates at the same pressure drop, resulting in extremely uneven distribution of working fluid flow rates in different flow channels. This flow difference not only significantly reduces the overall heat transfer efficiency, but may also cause local overheating, pressure fluctuations, and even pipe bursts and other serious safety accidents, greatly threatening the stable operation of equipment and systems; while the eccentrically arranged double-sided heated annular tube evaporator arranges the inner tube downward eccentrically, reduces the top gas phase velocity in the initial boiling stratified flow, and increases the bottom liquid phase velocity at the same time, reduces the gas-liquid slip velocity, and then reduces the two-phase friction resistance, which significantly shortens the hydrodynamic multi-value zone.

[0050] Table 1 is a comparison of the thermal economy of the eccentrically arranged double-side heated annular tube evaporator described in this application and the traditional shell and tube evaporator under the same size and the same working conditions.

[0051] The heat exchange tube size of the traditional shell and tube evaporator is tube bundle n = 19, tube length L = 3m, and tube outer diameter d out =25mm.

[0052] The outer diameter d of the heat exchange inner tube 3 in =15mm, the outer diameter d of the heat exchange outer tube 2 out =25mm.

[0053] The heat source is 130℃ hot water, the mass flow rate is 0.5kg / s, the working fluid is R245fa, and the evaporation temperature is 90℃.

[0054] Table 1

[0055]

[0056] It can be seen from the table that the heat transfer coefficient of the evaporator described in this application is increased by 28.6%, and the double-sided heating significantly enhances the heat exchange capacity; at the same size, the volume of the eccentric annular heat exchange tube bundle is reduced by 7.9%, and the compact design optimizes space utilization; the weight is reduced by 30.4%, and the double-tube structure reduces material usage; the heat exchange per unit volume is increased by 8.5%, and the heat exchange per unit weight is increased by 44.6%. At the same size, the eccentric annular heat exchange tube bundle is superior to the traditional heat exchange tube bundle in terms of heat exchange efficiency, volume, weight and economy, especially in scenarios with high efficiency and compactness requirements.

[0057] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. An eccentrically arranged double-side heated annular tube evaporator, characterized in that: It comprises a shell (1), a heat exchange outer tube (2), a heat exchange inner tube (3), and a tube sheet (4); One end of the shell (1) is provided with a shell-side inlet pipe (5), and the other end is provided with a shell-side outlet pipe (6); The shell (1) is provided with a heat exchange outer tube (2), and a tube sheet (4) is provided at each end of the heat exchange outer tube (2), and a distribution cavity (401) is constructed in the tube sheet (4), and the heat exchange outer tube (2) is connected to the distribution cavity (401); the shell (1) is provided with a tube side inlet pipe (7) and a tube side outlet pipe (8), and the tube side inlet pipe (7) and the tube side outlet pipe (8) are respectively connected to the distribution cavity (401) in the two tube sheets (4); A heat exchange inner tube (3) is eccentrically arranged inside the heat exchange outer tube (2), and both ends of the heat exchange inner tube (3) penetrate the tube sheet (4).

2. The eccentrically arranged double-side heated annular tube evaporator according to claim 1, characterized in that: The relative eccentricity between the inner heat exchange tube (3) and the outer heat exchange tube (2) is 0 to 0.

623.

3. The eccentrically arranged double-side heated annular tube evaporator according to claim 1, characterized in that: The difference between the diameter of the outer heat exchange tube (2) and the diameter of the inner heat exchange tube (3) is equal to 3% to 10% of the outer diameter of the inner heat exchange tube (3).

4. The eccentrically arranged double-side heated annular tube evaporator according to claim 1, characterized in that: At least three heat exchange outer tubes (2) are arranged between the two tube sheets (4), and the heat exchange outer tubes (2) are arranged in a compact triangle.

5. The eccentrically arranged double-side heated annular tube evaporator according to claim 4, characterized in that: The distance between two adjacent heat exchange outer tubes (2) is equal to 1.2 to 1.5 times the outer diameter of the heat exchange outer tube (2).

6. The eccentrically arranged double-side heated annular tube evaporator according to claim 1, characterized in that: The inner wall of the heat exchange outer tube (2) is provided with spiral stripes; The inner wall and the outer wall of the heat exchange inner tube (3) are provided with spiral stripes.

7. The eccentrically arranged double-side heated annular tube evaporator according to claim 1, characterized in that: The upper part of one of the tube sheets (4) is fixedly connected to the upper part of the shell (1), and a gap is provided between the lower part and the lower part of the shell (1); the lower part of the other tube sheet (4) is fixedly connected to the lower part of the shell (1), and a gap is provided between the upper part and the upper part of the shell (1); An upper baffle (9) and a lower baffle (10) are alternately arranged between the two tube sheets (4); the upper portion of the upper baffle (9) is fixedly connected to the upper portion of the shell (1), and a gap is provided between the lower portion and the lower portion of the shell (1); the lower portion of the lower baffle (10) is fixedly connected to the lower portion of the shell (1), and a gap is provided between the upper portion and the upper portion of the shell (1); In this way, the tube sheet (4), the upper baffle plate (9) and the lower baffle plate (10) divide the internal cavity of the shell (1) into a serpentine heat exchange channel.

8. The eccentrically arranged double-side heated annular tube evaporator according to claim 7, characterized in that: The spacing between the adjacent tube sheets (4) and the upper baffle (9), the upper baffle (9) and the lower baffle (10), and the lower baffle (10) and the tube sheets (4) is equal to 1 / 5 to 1 / 3 of the length of the heat exchange outer tube (2).

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