Steam heat exchange tube and steam-water mixed heat exchanger thereof

Abstract

The application provides a steam heat exchange pipe and a steam-water mixed heat exchanger thereof. The heat exchange pipe comprises a pipe body and spiral flow channel sheets arranged outside the pipe body. The heat exchange pipe is open at one end for steam inflow and is closed at the other end. Steam outlet holes are arranged on the pipe body between the spiral flow channel sheets. Steam in the heat exchange pipe flows out through the steam outlet holes. Steam flows along the spiral flow channel and is fully mixed with the liquid flowing outside, so that the disturbance effect of steam-liquid mixing is enhanced, and the steam-liquid heat exchange effect is improved.

Description

Technical Field

[0001] This invention relates to a heat exchange tube and a heat exchanger thereof, and more particularly to a steam heat exchange tube and a heat exchanger for steam-water mixing heat exchange. Background Technology

[0002] Shell-and-tube heat exchangers are widely used in industries such as chemical, petroleum, refrigeration, nuclear power, and energy. Due to the global energy crisis, the demand for heat exchangers in industrial production is increasing, and the quality requirements for heat exchangers are also becoming more stringent. In recent decades, although compact heat exchangers (plate, plate-fin, and welded plate heat exchangers, etc.), heat pipe heat exchangers, and direct contact heat exchangers have developed rapidly, shell-and-tube heat exchangers still dominate in terms of production and usage due to their high reliability and wide adaptability. According to relevant statistics, shell-and-tube heat exchangers still account for about 70% of all heat exchangers used in industrial plants.

[0003] Currently, people usually use heat exchangers to heat water. In various shell-and-tube and plate heat exchangers, steam and water go through different channels and exchange heat through good conductors. The water flow channels are generally designed to be winding and tortuous to increase the contact area with steam and enable it to be fully heated. As a result, there are defects such as complex structure, slow heating speed, large vibration and noise, and low thermal efficiency. Although the noise can be reduced to some extent by installing silencers, the flow rate and velocity of steam must be limited, and the shortcomings of slow heating speed and low thermal efficiency still exist.

[0004] Existing technologies also include some inventions related to direct vapor-liquid mixing heat exchange, such as CN104075590A which discloses a silent vapor-water mixing heat exchanger. This silent vapor-water mixing heat exchanger has a main body with an inlet and an outlet end along the water flow direction. A steam inlet end is located on the side wall of the main body. Both the inlet and outlet ends are conical structures. The outlet end has nozzles on its pipe wall for steam ejection, with the angle between the axis of the nozzles and the axis of the pipe wall being 40-65°. The main body is filled with a packing layer for noise reduction. A filter screen is provided at the steam inlet end, and a drain plug is provided on the side wall corresponding to the steam inlet end. This invention is rationally designed, uses a silent packing layer, is quiet and vibration-free, has low cost, is easy to install in a piping system, has high heating efficiency, and is simple to install and maintain, thus improving work efficiency. CN202709791U discloses a composite steam-water mixing tank, comprising a tank body, a drain valve, a steam inlet, a cold water inlet, a perforated baffle, a thermostat interface, a water outlet, and a vent pipe. The drain valve is located at the bottom of the tank body, the steam inlet is located on the lower side of the tank body, the perforated baffle is installed inside the tank body, the cold water inlet is located on the side of the tank body between the steam inlet and the perforated baffle, and the water outlet, vent pipe, and thermostat interface are located at the top of the tank body. This invention significantly improves upon traditional mixing tanks to address scaling issues, making it suitable for environments with high water hardness. It facilitates disassembly and cleaning, solves the problem of waste heat recovery, and fundamentally eliminates scaling and clogging.

[0005] In existing technologies, steam-liquid mixing heat exchange suffers from several problems, such as a single heat exchange tube, a small heat exchange area, and poor steam-liquid mixing effect. This application improves the heat exchange tube by adopting a new structure for the heat exchange tube and its heat exchanger, expanding the heat exchange area and increasing the mixing zone, resulting in better steam-liquid mixing. Summary of the Invention

[0006] In order to overcome the defects and deficiencies in the existing technology, the present invention provides a steam heat exchange tube and its vapor-liquid heat exchanger, which can increase the heat exchange area and increase the mixing zone, thereby effectively improving the heat transfer efficiency.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A steam heat exchange tube includes a tube body and spiral flow channel plates disposed outside the tube body. One end of the heat exchange tube is open for steam to flow in, and the other end is closed. Steam outlet holes are provided on the tube body between the spiral flow channel plates, and the steam in the heat exchange tube flows out through the steam outlet holes.

[0009] Preferably, the flow area of ​​the steam outlet hole increases continuously from one end of the heat exchange tube to the other.

[0010] Preferably, the flow area of ​​the steam outlet hole increases progressively from one end of the heat exchange tube to the other.

[0011] Preferably, the spacing between the spiral flow channel plates is 1:(1.5-2) to the height of the spiral flow channel plates.

[0012] A steam-water mixing heat exchanger includes a shell, heat exchange tubes, a liquid inlet pipe, an inlet end cap, and an outlet end cap. The liquid inlet pipe is disposed on the shell, and a steam inlet pipe and a fluid outlet pipe are respectively disposed on the inlet end cap and the outlet end cap. An inlet tube sheet is disposed between the inlet end cap and the shell, and an outlet tube sheet is disposed between the outlet end cap and the shell. The heat exchange tubes are disposed in the shell, and a first end and a second end of the heat exchange tubes are respectively fixedly connected to the inlet tube sheet and the outlet tube sheet, wherein the first end is connected to the inlet end cap, and the second end is not connected to the outlet end cap. Steam outlet holes for gas outflow are provided on the tube wall of the heat exchange tubes, and through holes for connecting the shell and the outlet end cap are provided on the outlet tube sheet. The heat exchange tubes are characterized in that they include a tube body and spiral flow channel plates disposed outside the tube body, and steam outlet holes are provided on the tube body between the spiral flow channel plates, through which steam in the heat exchange tubes flows out.

[0013] As a preferred option, the flow area of ​​the steam outlet hole increases continuously from the inlet end cap to the outlet end cap.

[0014] As a preferred option, the flow area of ​​the steam outlet is increasing at an ever-increasing rate.

[0015] Preferably, the steam enters the heat exchange tube through the steam inlet pipe and the end cap, and then exits through the steam outlet hole of the heat exchange tube. It mixes and exchanges heat with the liquid entering through the liquid inlet pipe. The heat-exchanged fluid enters the outlet end cap through the through hole of the outlet tube sheet, and then flows out from the fluid outlet pipe.

[0016] Preferably, the spacing between the spiral flow channel plates is 1:(1.5-2) to the height of the spiral flow channel plates.

[0017] Preferably, the height of the spiral flow channel fins is 0.3-0.4 times the outer diameter of the heat exchange tube.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] This invention utilizes a steam heat exchange tube with a spiral flow channel. Steam flows out from the steam holes of the heat exchange tube with the spiral flow channel structure and flows along the spiral flow channel, mixing with the externally flowing liquid in a spiral manner. Moreover, because a portion of the external fluid also flows along the spiral flow channel, the structure of the spiral flow channel causes the mixed fluid to change its flow direction when flowing within it, forming a vortex, which enhances turbulence and mixing, thereby improving the turbulence effect and the mixing effect. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of the spiral flow channel heat exchange tube structure of the heat exchanger of the present invention;

[0021] Figure 2 This is a schematic diagram of the shell-and-tube heat exchanger of the present invention;

[0022] Figure 3 This is a schematic diagram of the heat exchanger with a spiral flow channel heat exchange tube structure according to the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] Unless otherwise specified, in this article, " / " represents division, and "×" and "*" represent multiplication.

[0025] Figure 1 A spiral flow channel steam heat exchange tube 2 is disclosed. For example... Figure 1 As shown, the heat exchange tube 2 includes a tube body 25 and spiral flow channel plates 24 disposed outside the tube body. One end 21 of the heat exchange tube is open for steam to flow in, and the other end 22 is closed. Steam outlet holes 23 are provided on the tube body between the spiral flow channel plates 24. The steam in the heat exchange tube 2 flows out through the steam outlet holes 23 and mixes with the external fluid for heat exchange.

[0026] This invention utilizes a steam heat exchange tube with a spiral flow channel. Steam flows out from the steam holes of the heat exchange tube with the spiral flow channel structure and flows along the spiral flow channel, mixing with the externally flowing liquid in a spiral manner. Moreover, because a portion of the external fluid also flows along the spiral flow channel, the structure of the spiral flow channel causes the mixed fluid to change its flow direction when flowing within it, forming a vortex, which enhances turbulence and mixing, thereby improving the turbulence effect and the mixing effect.

[0027] Furthermore, the spiral flow channel is equivalent to external spiral fins, allowing indirect heat exchange between the external fluid and steam through the heat exchange tube wall, further improving the heat exchange mixing effect.

[0028] As an improvement, the diameter of the heat exchange tube and the shape and size of the spiral flow channel can be changed according to the steam-liquid flow rate. To maintain a good mixing effect and make the steam and external fluid mix more evenly, the height of the spiral flow channel blades and the diameter of the cylinder, as well as the pitch of the spiral flow channel blades and the diameter of the cylinder, should be kept at certain values. Therefore, it is preferable that the spacing between adjacent spiral flow channel blades and the height of the spiral flow channel blades are 1:(1.5-2), and the height of the spiral flow channel blades is 0.3-0.4 times the outer diameter of the heat exchange tube, so as to maintain a good turbulence effect and a good mixing effect.

[0029] As an improvement, the through-hole area of ​​the steam outlet 23 of the heat exchange tube increases from the open end 21 to the closed end 22. This arrangement ensures that the flow area of ​​the steam outlet 23 increases along the direction of steam flow within the tube. This improves the heat exchange efficiency. The heat exchange between the liquid and steam is divided into two parts: indirect heat exchange through the heat exchange tube and heat exchange through the mixing of steam and liquid at the steam outlet 23. Since the steam inlet and liquid inlet are in the same direction, for example… Figure 2 , 3 The above approach aims to reduce flow resistance. However, this is essentially co-current heat exchange, which suffers from poor heat transfer efficiency. Furthermore, because the pressure is higher near the steam inlet, steam is more easily discharged, leading to uneven steam distribution. Therefore, further improvements are needed. By varying the distribution density of the steam outlet holes, the steam distribution can be improved, resulting in a more uniform distribution of steam at the rear compared to the front, or even a larger steam volume at the rear. Moreover, as the flow continues, the temperature difference between the hot and cold fluids gradually decreases. By increasing the steam flow rate at the rear, the overall heat transfer per unit area becomes more uniform.

[0030] As an improvement, the through-hole area of ​​the steam outlet 23 of the heat exchange tube gradually increases from the open end 21 to the closed end 22, thereby gradually increasing the steam output per unit length of the heat exchange tube. With continuous flow, the temperature difference between the hot and cold fluids gradually decreases. By gradually increasing the steam output per unit length of the heat exchange tube, the steam flow rate is increased. This increased flow rate reduces the decrease in heat exchange caused by the shrinking temperature difference, resulting in a more uniform heat exchange per unit length. This overcomes the problem of uneven heat exchange in co-current heat exchangers, thus achieving the technical effect of improving heat exchange efficiency.

[0031] The present invention also provides a shell-and-tube heat exchanger for steam-water mixing heat exchange, such as... Figure 2 As shown, the shell-and-tube heat exchanger includes a shell 1, heat exchange tubes 2, a liquid inlet pipe 3, an inlet end cap 4, and an outlet end cap 5. The liquid inlet pipe 3 is disposed on the shell, and a steam inlet pipe 6 and a fluid outlet pipe 7 are respectively disposed on the inlet end cap 4 and the outlet end cap 5. An inlet tube sheet 8 is disposed between the inlet end cap 6 and the shell 1, and an outlet tube sheet 9 is disposed between the outlet end cap 7 and the shell 1. The heat exchange tubes 2 are disposed in the shell 1, and the first end 21 and the second end 22 of the heat exchange tubes are fixedly connected to the inlet tube sheet 8 and the outlet tube sheet 9, respectively. The first end 21 is connected to the inlet end cap 4, and the second end 22 is not connected to the outlet end cap 5. A steam outlet hole 23 is provided on the tube wall of the heat exchange tubes 2, and a through hole 10 is provided on the outlet tube sheet to connect the shell and the outlet end cap.

[0032] The steam enters the heat exchange tube 2 through the steam inlet pipe 6 and the end cap 4, and then exits through the steam outlet 23 of the heat exchange tube 2. Because the second end of the heat exchange tube is a closed structure, the steam cannot directly enter the outlet end cap 5 through the second end, and therefore must flow out through the steam outlet 23. The liquid flows in through the liquid inlet pipe 3, and then mixes and exchanges heat directly with the steam flowing out through the steam outlet 23 in the tube shell 1. The heat-exchanged fluid enters the outlet end cap through the through hole of the outlet tube sheet, and then flows out from the fluid outlet pipe.

[0033] This invention proposes a shell-and-tube heat exchanger for direct steam-water mixing and heat exchange. The heat exchanger can provide an expanded heat exchange area, increasing the mixing zone. Moreover, because it is a shell-and-tube heat exchanger, the steam inside the heat exchange tubes can achieve indirect heat exchange with the liquid even inside the tubes. This allows the steam to exchange heat with the liquid both inside and outside the tubes, extending the heat exchange length and area, resulting in a greater heat exchange area distributed per unit volume.

[0034] As an improvement, such as Figure 3 As shown, the heat exchange tube is... Figure 1 Spiral flow channel heat exchange tube.

[0035] As an improvement, the height of the spiral flow channel blades extending outward from the outer wall of the horizontal pipe increases continuously from the inlet end cap 4 to the outlet end cap 5. This arrangement allows for thorough mixing of the liquid and steam upstream of the liquid flow due to the smaller blade height. As the flow channel blade height increases, the fully mixed steam and water enter the spiral flow channel, where the rotational force increases, resulting in a greater rotational force in the output airflow. This enhances the rotational mixing effect at the rear, strengthens heat exchange, promotes overall heat exchange uniformity, and further improves the uniformity of mixing.

[0036] As an improvement, the height and amplitude of the rotating flow channel plates extending outward from the outer wall of the horizontal tube are continuously increased from the inlet end cap 4 to the outlet end cap 5. This continuous increase in amplitude further enhances the uniformity of mixing.

[0037] As an improvement, the spiral flow channel plates can be arranged at intervals. For example, heat exchange tube sections with spiral flow channel plates and those without spiral flow channel plates can be arranged alternately. This allows for segmented turbulent mixing of the fluid, reducing flow resistance and also segmentally disrupting the laminar sublayer, thereby improving the heat exchange effect.

[0038] As an improvement, the shell-and-tube heat exchanger is a horizontal shell-and-tube heat exchanger, in which multiple through holes 10 are provided, and the distribution density of the through holes 10 decreases from bottom to top. The purpose of setting a change in the density of the through holes is to achieve a change in the flow area of ​​the fluid after heat exchange, thereby making the flow area gradually decrease from bottom to top. The main purposes are as follows. Firstly, because of its low density, the discharged steam may not undergo timely heat exchange and could accumulate at the top, increasing the pressure there. This could cause the steam to exit directly through the upper orifice without mixing and heat exchange, thus reducing short-circuiting in heat exchange. Secondly, while excessive steam at the top increases pressure, the absence of orifices would hinder liquid mixing. Therefore, small-flow orifices are necessary to reduce pressure, and the orifice flow area should be minimized to ensure effective heat exchange. Thirdly, the smaller upper flow area allows steam to flow from the bottom, and the liquid, due to gravity, is also more concentrated at the bottom. This ensures thorough mixing of the liquid and steam at the bottom, reduces steam accumulation at the top, and results in more uniform heat exchange overall. This lowers the pressure inside the tube and shell, further achieving the goal of thorough mixing and heat exchange.

[0039] As an improvement, the distribution density of the through holes 10 gradually increases along the upward height direction. By varying the distribution density of the through holes, and thus the flow area, the overall heat exchange becomes more uniform, the pressure inside the tube is reduced, and the purpose of thorough mixing and heat exchange is further achieved.

[0040] As an improvement, multiple baffles 11 are installed inside the shell, including a lower baffle located at the bottom of the shell and an upper baffle located at the top of the shell, with the lower and upper baffles spaced apart. By installing the baffles, the liquid flows in a tortuous manner, improving the heat exchange effect.

[0041] As an improvement, the liquid inlet pipe 3 is located on the side close to the inlet head 4. This arrangement ensures that the steam flow and liquid flow are in the same direction, thereby reducing flow resistance.

[0042] As an improvement, such as Figure 2 As shown, the liquid inlet connector is located at the lower part of the tube shell, and the lower baffle is located near the liquid inlet connector baffle. This arrangement ensures that the inlet fluid must flow upwards, preventing it from flowing through the lower part due to gravity, thereby improving heat exchange efficiency.

[0043] As an improvement, the steam is water vapor, the liquid is cold water, and the heat-exchanged fluid is hot water.

[0044] As an improvement, such as Figure 2As shown, the baffle plate near the outlet tube sheet is the lower baffle plate. Furthermore, the height of the baffle plate near the outlet tube sheet is greater than the height of the other baffle plates. Preferably, the height of the baffle plate near the outlet tube sheet is 0.75-0.85 times the diameter of the tube shell 1, and 1.2-1.3 times the height of the other baffle plates. By setting the height of the outlet baffle plate, the liquid passes through the upper part as much as possible, flushing away the steam in the upper part and preventing steam accumulation on the outlet tube sheet. Moreover, this baffle plate height setting is coordinated with the distribution density variation of the through-holes 10, thereby ensuring thorough mixing of liquid and steam in the lower part and reducing steam accumulation in the upper part, resulting in uniform heat exchange overall, reducing the pressure inside the tube shell, and further achieving the purpose of thorough mixing and heat exchange.

[0045] As an improvement, the distance between the lower baffle plate near the outlet tube sheet and the outlet tube sheet is smaller than the distance between the lower baffle plate near the outlet tube sheet and adjacent baffle plates. By reducing the distance, the liquid flows more rapidly, flushing away the steam accumulated on the upper part of the baffle plate and other locations, reducing steam accumulation in the upper part, resulting in more uniform heat exchange overall, reducing the pressure inside the tube shell, and further achieving the purpose of thorough mixing and heat exchange.

[0046] As an improvement, the height of the lower baffle gradually increases from the inlet end cap 4 to the outlet end cap 5. This is mainly because, with the continuous heat exchange flow between steam and liquid, steam, due to its lower density, tends to concentrate more and more at the top, causing an increase in pressure. This steam accumulation at the top deteriorates the heat exchange effect, thus requiring increased liquid impact to disperse and mix the steam. Since the liquid has a higher density, it is less likely to impact the top. Therefore, by gradually increasing the height of the lower baffle, the flow rate of the liquid upwards is increased, resulting in a greater impact force along the flow direction. Compared to a baffle with a constant height, this design ensures low flow resistance while achieving thorough vapor-liquid mixing, thereby improving the heat exchange effect.

[0047] As an improvement, the height of the lower baffle plate gradually increases from the inlet end cap 4 to the outlet end cap 5. This design further ensures thorough mixing of the vapor and liquid, improving heat exchange efficiency.

[0048] As an improvement, the spacing between adjacent baffles 11 increases continuously from the inlet end cap 4 to the outlet end cap 5. Because as the fluid flows continuously and steam continuously flows out, the amount of steam-liquid mixture increases, leading to a continuous increase in flow velocity. Especially due to the presence of steam, a steam-water mixture may be present, causing both increased flow velocity and increased noise during the flow process. Increasing the spacing between adjacent baffles ensures a balanced flow velocity and avoids generating significant noise.

[0049] As an improvement, the spacing between adjacent baffles 11 increases progressively from the inlet end cap 4 to the outlet end cap 5. This further ensures balanced flow velocity and reduces noise.

[0050] While the present invention has been disclosed above with reference to preferred embodiments, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A steam-water mixing heat exchanger, comprising a shell, heat exchange tubes, a liquid inlet pipe, an inlet end cap, and an outlet end cap; the liquid inlet pipe is disposed on the shell, and a steam inlet pipe and a fluid outlet pipe are respectively disposed on the inlet end cap and the outlet end cap; an inlet tube sheet is disposed between the inlet end cap and the shell, and an outlet tube sheet is disposed between the outlet end cap and the shell; multiple heat exchange tubes are disposed within the shell, and a first end and a second end of each heat exchange tube are fixedly connected to the inlet tube sheet and the outlet tube sheet, respectively, wherein the first end communicates with the inlet end cap, and the second end is not communicated with the outlet end cap; steam outlet holes are provided on the tube walls of the heat exchange tubes, and through holes are provided on the outlet tube sheet communicating with the shell and the outlet end cap, characterized in that... The heat exchange tube includes a tube body and spiral flow channel plates disposed outside the tube body. Steam outlet holes are provided on the tube body between the spiral flow channel plates, and steam inside the heat exchange tube flows out through the steam outlet holes. The flow area of ​​the steam outlet holes continuously increases from the inlet end cap to the outlet end cap.

2. The heat exchanger as described in claim 1, characterized in that, The flow area of ​​the steam outlet is increasing at an increasingly larger rate.

3. The heat exchanger as described in claim 1, characterized in that, The steam enters the heat exchange tube through the steam inlet pipe and the end cap, then exits through the steam outlet hole of the heat exchange tube and mixes with the liquid entering through the liquid inlet pipe for heat exchange. The heat-exchanged fluid enters the outlet end cap through the through hole of the outlet tube sheet and then flows out from the fluid outlet pipe.

4. The heat exchanger as described in claim 1, characterized in that, The spacing between the spiral flow channel plates is 1:(1.5-2) to the height of the spiral flow channel plates.

5. The heat exchanger as described in claim 1, characterized in that, The height of the spiral flow channel fins is 0.3-0.4 times the outer diameter of the heat exchange tube.

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