Heat exchanger for indirect and direct mixed heat exchange

Abstract

The invention provides an indirect and direct mixed heat exchange heat exchanger which is characterized in that a shell is divided into a plurality of cavities by tube plates, a cold source inlet is formed in the cavity adjacent to an inlet seal head, and a heat exchange tube in the cavity close to the inlet seal head is not provided with a communicating hole through which steam flows out from the heat exchange tube. And the heat exchange tube in the cavity close to the outlet seal head is provided with a communicating hole through which steam flows out from the heat exchange tube. Through whether the through holes are formed in the different positions of the heat exchange pipe or not, the mode that indirect heat exchange is adopted firstly and then direct heat exchange is adopted is adopted, on one hand, uniform heat exchange in the direction of the whole heat exchange pipe can be achieved, and meanwhile noise caused by steam injection is lowered.

Description

Technical Field

[0001] This invention belongs to the field of heat exchangers, and particularly relates to a heat exchanger that performs both direct and indirect heat exchange simultaneously. Background Technology

[0002] A heat exchanger is an energy-saving device that facilitates heat transfer between two or more fluids at different temperatures. It transfers heat from a higher-temperature fluid to a lower-temperature fluid, bringing the fluid temperature to the specified parameters to meet process requirements. It is also one of the key devices for improving energy efficiency. The heat exchanger industry involves nearly 30 sectors, including HVAC, pressure vessels, wastewater treatment equipment, chemicals, and petroleum, forming interconnected industrial chains.

[0003] A shell-and-tube heat exchanger is a type of heat exchanger in which two fluids at different temperatures flow within a space separated by a wall. Heat exchange occurs between the two fluids through heat conduction through the wall and convection at the wall surface. Shell-and-tube heat exchangers include shell-and-tube, double-tube, and other types, with shell-and-tube heat exchangers being the most widely used.

[0004] A mixing heat exchanger, also known as a direct contact heat exchanger, is a heat exchange device that achieves heat transfer through direct contact between cold and hot fluids. Its core principle is direct mixing and heat exchange between the fluids. It features advantages such as avoiding fouling and thermal resistance on heat transfer walls, simple structure, and high heat transfer efficiency. It is mainly used in chemical, metallurgical, power engineering, and air conditioning industries.

[0005] In the prior art, CN121089472A provides a shell-and-tube heat exchanger with gradually changing steam outlet areas on the heat exchange tubes. The heat exchange tubes have steam outlets on their walls, and the area of ​​the steam outlets increases from the inlet end cap to the outlet end cap, resulting in a larger flow area of ​​the steam outlets along the direction of steam flow within the tubes. This invention, by varying the area of ​​the steam outlets, improves steam distribution, making the steam distribution at the rear and front more uniform, or increasing the amount of steam at the rear. Furthermore, with continuous flow, the temperature difference between the hot and cold fluids gradually decreases. By increasing the steam flow rate at the rear, the overall heat exchange per unit area becomes relatively uniform.

[0006] CN206269615U discloses a spray-type condenser, including a shell, end caps, tube sheet, spray device, and heat exchange tubes. The end caps are connected to both ends of the shell, and the heat exchange tubes are arranged inside the shell with their open ends sealed to the tube sheet. A refrigerant inlet is provided on one end cap, and a refrigerant outlet is provided on the other end cap. A steam inlet and a non-condensable gas outlet are provided on the upper surface of the shell, and a condensate outlet is provided on the lower surface of the shell. This device provides a spray-type condenser suitable for the condensation process of mixed steam containing low-boiling-point components, which can effectively solve the problem that low-boiling-point components in mixed steam are difficult to condense completely.

[0007] CN119983903A provides a steam heat exchange tube and its steam-water mixing heat exchanger. The 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 inside the heat exchange tube flows out through the steam outlet holes. In this invention, the steam flows along the spiral flow channel and mixes thoroughly with the externally flowing liquid, enhancing the turbulence effect of the steam-liquid mixing and improving the steam-liquid heat exchange efficiency.

[0008] CN120557980A discloses a cryogenic flare gas heat exchange device and method based on U-shaped heat exchange tubes, belonging to the field of cryogenic equipment technology. The heat exchange device provided by this invention includes a cylinder, end caps, a tube-side box, a tube-side plate, heat exchange tubes, steam tubes, and steam injection tubes, wherein the heat exchange tubes are U-shaped. The cylinder is fixed to the end caps at both ends, has a steam pipe through-hole and a pressure-balancing vent at the top, and a water inlet and a drain outlet at the bottom. The inner cavity of the cylinder houses the heat exchange tubes, which are connected to the tube-side box via the tube-side plate. The lower and upper ends of the tube-side box are connected to the inlet and outlet pipes, respectively, and a partition plate is provided in the middle. A short-circuit protection partition is provided at the end of the heat exchange tube furthest from the tube-side plate. A liquid level control interface is located on the side of the cylinder. The heat exchange device provided by this invention has a compact design, saving space while reducing material usage, simplifying the manufacturing process, improving heat transfer efficiency, and enhancing performance. It has significant economic and high-performance advantages, reducing manufacturing costs.

[0009] In the existing technology, the same heat exchanger is used for heat exchange by direct mixing heat exchange or indirect heat exchange. However, the heat exchanger with direct mixing heat exchange has a lot of noise during the steam injection process because of the high steam pressure. The heat exchange effect of indirect heat exchange is worse than that of direct heat exchange.

[0010] To address the aforementioned problems, this invention improves the heat exchanger, enabling it to combine direct and indirect heat exchange simultaneously. By varying the presence of through holes at different locations on the heat exchange tubes, and by first employing indirect heat exchange followed by direct heat exchange, uniform heat exchange can be achieved throughout the entire heat exchange tube direction, while also reducing noise caused by steam jets. Summary of the Invention

[0011] This invention provides a heat exchanger that combines indirect and direct heat exchange, thereby solving the aforementioned technical problems.

[0012] To achieve the above objectives, the technical solution of the present invention is as follows: A heat exchanger for mixed indirect and direct heat exchange includes a shell, tube sheets, and heat exchange tubes. The shell has an inlet end cap and an outlet end cap at both ends, with a steam inlet and a fluid outlet respectively. A cold source inlet is located on the shell. Multiple tube sheets are arranged parallel to each other within the shell and are sealed to the inner wall of the shell. The tube sheets have perforations for the heat exchange tubes to pass through. Except for the inlet tube sheet adjacent to the inlet end cap, the remaining tube sheets have through holes for fluid passage. The tube sheets divide the shell into multiple cavities. The cold source inlet is located in the cavity adjacent to the inlet end cap. The heat exchange tubes in the cavity near the inlet end cap do not have through holes for steam to flow out, while the heat exchange tubes in the cavity near the outlet end cap do have through holes for steam to flow out.

[0013] As an improvement, a pressure relief hole is provided on the upper part of the outlet end cap.

[0014] As an improvement, drainage holes are provided at the lower parts of the inlet and outlet end caps, respectively.

[0015] As an improvement, the cold source is cold water, the steam is water vapor, and the fluid is hot water.

[0016] As an improvement, the tube sheet divides the shell into N cavities, wherein the number of cavities with connecting holes for the heat exchange tubes is greater than or equal to N / 2.

[0017] As an improvement, with the steam inlet temperature and pressure kept constant, the number of cavities with connecting holes in the heat exchange tubes increases as the cold source temperature at the cold source inlet decreases.

[0018] As an improvement, with the steam inlet temperature and pressure kept constant, as the cold source temperature at the cold source inlet decreases, the sum of the lengths of the cavities with connecting holes in the heat exchange tubes increases.

[0019] As an improvement, the number of tube sheets is set to 4-8.

[0020] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes, and the number of connecting holes in the tube sheet increases with the flow direction of the fluid inside the heat exchange tubes.

[0021] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes, and the number of connecting holes in the tube sheet increases with the direction of fluid flow inside the heat exchange tubes.

[0022] Compared with the prior art, the present invention has the following advantages: This invention utilizes the presence or absence of connecting holes at different locations on the heat exchange tubes. Indirect heat exchange is employed at the steam inlet, thereby reducing steam pressure and temperature, and thus minimizing steam jet noise. Simultaneously, direct heat exchange is employed at locations farther from the steam inlet, increasing heat exchange efficiency. Therefore, this application, by first employing indirect heat exchange and then direct heat exchange, can improve heat exchange efficiency while simultaneously reducing noise caused by steam jets. Furthermore, because the initial indirect heat exchange lowers the steam temperature, the subsequent mixed heat exchange ensures uniform heat exchange throughout the entire heat exchange tube direction. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the heat exchanger structure of the present invention; Figure 2 This is a schematic cross-sectional view of the heat exchange tube of the present invention; Figure 3 This is a schematic diagram of the improved cross-sectional structure of the heat exchanger tube of the present invention. Detailed Implementation

[0024] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] Unless otherwise specified, in this article, " / " represents division, and "×" and "*" represent multiplication.

[0026] Figure 1 A heat exchanger that combines indirect and direct heat exchange is disclosed. For example... Figure 1 As shown, the heat exchanger includes a shell 1, tube sheets 21-23, and heat exchange tubes 3. An inlet end cap 4 and an outlet end cap 5 are respectively provided at both ends of the shell 1. A steam inlet 6 and a fluid outlet 7 are respectively provided on the inlet end cap 4 and the outlet end cap 5. A cold source inlet 8 is provided on the shell 1. There are multiple tube sheets 21-23 arranged in parallel inside the shell, including an inlet tube sheet 21 adjacent to the inlet end cap, an outlet tube sheet 22 adjacent to the outlet end cap, and an intermediate tube sheet 23. The tube sheet 2 is sealed to the inner wall of the shell 1. The tube sheet is provided with tube holes 24 for the heat exchange tubes 3 to pass through. Except for the inlet tube sheet 21 adjacent to the inlet end cap, the outlet tube sheet and the intermediate tube sheet are provided with through holes 25 for fluid to pass through. The tube sheet 2 divides the shell into multiple cavities 9. The cold source inlet 8 is located on the cavity adjacent to the inlet end cap. The heat exchange tube 3 in the cavity 9 near the inlet end cap does not have a connecting hole 31 for steam to flow out of the heat exchange tube. The heat exchange tube 3 in the cavity near the outlet end cap has a connecting hole 31 for steam to flow out of the heat exchange tube.

[0027] For example, see Figure 1A total of 5 tube sheets are set, which divide the tube shell into four chambers from left to right. The heat exchange tubes in the first chamber near the inlet head do not have a connecting hole 31, while the heat exchange tubes in the other three chambers have a connecting hole 31.

[0028] By setting connecting holes at different positions on the heat exchange tube, the following technical effects are achieved: 1) Because the steam at the inlet has a certain pressure and temperature, the jetting noise is quite loud. This invention addresses this by using through holes at different locations on the heat exchange tube to achieve indirect heat exchange at the steam inlet, thereby reducing the steam pressure and temperature. The steam is cooled and depressurized before jetting, thus reducing the noise from the steam jetting. Furthermore, since direct heat exchange is significantly more efficient than indirect heat exchange, direct heat exchange is used at locations far from the steam inlet to increase heat exchange efficiency. This achieves both noise reduction and increased heat exchange efficiency simultaneously.

[0029] 2) In normal direct or indirect heat exchangers, the heat exchange efficiency gradually decreases as the heat source temperature decreases and the temperature difference with the cold source decreases along the fluid flow direction. This application addresses this by first employing indirect heat exchange followed by direct heat exchange. Indirect heat exchange is used where the heat source temperature is high, and direct heat exchange is used where the heat source temperature is low. Because direct heat exchange has a higher efficiency than indirect heat exchange, the heat exchange is relatively uniform throughout the entire heat exchange tube direction, avoiding localized uneven heat exchange.

[0030] As an improvement, the heat exchange tube is open at one end and closed at the other. For example... Figure 1 As shown, the inlet tube sheet 21 is open, while the outlet tube sheet is closed. This closed section ensures that steam can be ejected through the connecting hole, thus enhancing heat transfer.

[0031] As an improvement, a pressure relief hole 10 is provided on the upper part of the outlet end cap 5. By providing the pressure relief hole 11, non-condensable gases can be discharged.

[0032] As an improvement, the lower parts of the inlet end cap 6 and the outlet end cap 5 are respectively provided with drain holes 11 and 12. By providing drain holes, the liquid accumulated inside the end caps can be discharged when the heat exchanger is not running and the weather is cold, thus preventing freezing.

[0033] As an improvement, the cold source is cold water, the steam is water vapor, and the fluid is hot water. Therefore, the final output from the fluid outlet is hot water. The hot water can be domestic hot water or heating hot water.

[0034] As an improvement, such as Figure 1 As shown, tube sheets 21-23 divide the shell into N cavities, for example, see [reference needed]. Figure 1A total of five tube sheets are installed, dividing the tube shell into four chambers from left to right. The number of chambers with connecting holes for the heat exchange tubes is greater than or equal to N / 2, where N / 2 is rounded to the nearest whole number. This arrangement ensures that the heat exchange area for direct heat exchange is greater than or equal to that for indirect heat exchange, guaranteeing sufficient heat exchange efficiency.

[0035] As an improvement, the length of the tube without the connecting hole 31 is between one-fifth and one-half of the total length of the heat exchange tube. Preferably, it is between one-quarter and one-third. This setting ensures sufficient heat exchange efficiency while minimizing noise.

[0036] As an improvement, the steam temperature and pressure at steam inlet 6 remain constant. As the cold source temperature at the cold source inlet decreases, the number of cavities with connecting holes in the heat exchange tubes increases. This is also one design method for the heat exchanger. Because the cold source temperature is low, indirect heat exchange occurs between the cold source and the steam, causing the steam temperature and pressure to decrease more rapidly. This also reduces the noise from the steam jet. Therefore, in this case, the number of cavities with connecting holes in the heat exchange tubes can be increased to increase the heat exchange area for direct mixing and heat exchange, thereby improving the thermal efficiency.

[0037] As an improvement, the steam inlet temperature and pressure remain constant. As the cold source temperature at the inlet decreases, the sum of the lengths of the cavities with connecting holes in the heat exchange tubes increases. This is also one design method for a heat exchanger. Because the cold source temperature is low, indirect heat exchange occurs between the cold source and the steam, causing the steam temperature and pressure to decrease more rapidly. This also reduces the noise from the steam jet. Therefore, in this case, the total length of the cavities with connecting holes in the heat exchange tubes can be increased to increase the heat exchange area for direct mixing and heat exchange, thereby improving thermal efficiency.

[0038] As an improvement, the number of tube sheets is set to 4-8. Preferably, it is 5.

[0039] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes. The number of connecting holes increases with the flow direction of the fluid inside the heat exchange tubes. This is because as more steam is ejected from the connecting holes, the amount of fluid inside the shell also increases. By increasing the number of connecting holes, the flow area of ​​the connecting holes is increased, thus achieving fluid velocity balance.

[0040] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes. The number of connecting holes in the tube sheet increases progressively with the direction of fluid flow within the heat exchange tubes. This arrangement further achieves fluid velocity equalization.

[0041] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes. The flow area of ​​each individual through-hole in the tube sheet increases with the direction of fluid flow within the tubes. This is because as more steam is ejected from the connecting holes, the amount of fluid inside the shell also increases. By increasing the flow area of ​​the through-holes, the total flow area of ​​the through-holes is increased, thus achieving fluid velocity balance.

[0042] As an improvement, a cavity with connecting holes is provided in the heat exchange tubes. As the fluid flows through the heat exchange tubes, the flow area of ​​each individual through-hole in the tube sheet increases progressively. This arrangement can further achieve fluid velocity equalization.

[0043] As an improvement, the heat exchanger is a horizontal heat exchanger, the heat exchange tubes are arranged horizontally, and the tube sheet is arranged vertically.

[0044] As an improvement, the distribution density of the through holes in different tube sheets is partially different. Along the direction from the inlet head to the outlet head, the distribution density of the tube holes in the tube sheet is greater in the lower part near the inlet head than in the upper part, less in the lower part of the tube sheet in the middle position than in the upper part, and finally greater in the lower part of the tube sheet near the outlet head than in the upper part.

[0045] Because of the location near the inlet end cap, and the use of indirect heat exchange, cold water enters the shell and flows downwards due to its density. This results in a higher concentration of cold water at the bottom, leading to a greater distribution density and flow area in the lower perforations compared to the upper ones. In the middle section, steam is ejected and accumulates at the top. Again, the lower perforation density and flow area allow more cold water to flow upwards for direct heat exchange. As heat exchange continues, the steam condenses into water, which flows downwards due to its density, again resulting in a higher concentration of water at the bottom. Therefore, the lower perforation density and flow area are again greater than the upper perforation density. This design improves heat exchange efficiency and reduces flow resistance.

[0046] As an improvement, the heat exchange tube has a square cross-section.

[0047] As an improvement, the lines connecting the vertices of the heat exchange tube cross section form a square, and a tube wall is formed between adjacent vertices of the square. The tube wall is parabolic, and the bending direction of the tube wall is towards the center of the square. A connecting hole 31 is formed on the tube wall.

[0048] The heat exchange tube of the present invention increases the heat exchange area by modifying the square tube into an inwardly curved shape; moreover, because of the inwardly curved tube wall, the fluid inside the tube flows more from the center of the tube to the apex of the tube, thereby increasing the corner pressure. Compared with other shapes, it reduces the flow dead zone and avoids uneven spraying caused by uneven fluid distribution at different positions, thus making the overall sprayed fluid uniform.

[0049] This application improves the shape of the square tube wall by making it curved inward, which increases the flow area of ​​the external fluid and the mixing area and mixing time of the two fluids, thereby making the mixing more uniform and the heat exchange effect better.

[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 heat exchanger for indirect and direct mixed heat exchange, the heat exchanger comprising a shell, tube sheets, and heat exchange tubes, wherein an inlet end cap and an outlet end cap are respectively provided at both ends of the shell, and a steam inlet and a fluid outlet are respectively provided on the inlet end cap and the outlet end cap, and a cold source inlet is provided on the shell, wherein multiple tube sheets are arranged in parallel within the shell, the tube sheets are sealed to the inner wall of the shell, and the tube sheets are provided with tube holes for the heat exchange tubes to pass through, except for the inlet tube sheet adjacent to the inlet end cap, the remaining tube sheets are provided with through holes for fluid to pass through, characterized in that, The tube sheet divides the shell into multiple cavities. The cold source inlet is located in the cavity adjacent to the inlet end cap. The heat exchange tubes in the cavity near the inlet end cap do not have connecting holes for steam to flow out of the heat exchange tubes. The heat exchange tubes in the cavity near the outlet end cap have connecting holes for steam to flow out of the heat exchange tubes.

2. The heat exchanger as described in claim 1, characterized in that, The upper part of the outlet end cap is also provided with a pressure relief hole.

3. The heat exchanger as described in claim 1, characterized in that, The lower part of the inlet end cap and the outlet end cap are respectively provided with drainage holes.

4. The heat exchanger as described in claim 1, characterized in that, The cold source is cold water, the steam is water vapor, and the fluid is hot water.

5. The heat exchanger as described in claim 1, characterized in that, The tube sheet divides the shell into N cavities, where the number of cavities with connecting holes for the heat exchange tubes is greater than or equal to N / 2.

6. The heat exchanger as described in claim 5, characterized in that, When the steam inlet temperature and pressure remain constant, as the cold source inlet temperature decreases, the number of cavities with connecting holes in the heat exchange tubes increases.

7. The heat exchanger as described in claim 5, characterized in that, When the steam inlet temperature and pressure remain constant, as the cold source temperature at the cold source inlet decreases, the sum of the lengths of the cavities with connecting holes in the heat exchange tubes increases.

8. The heat exchanger as claimed in claim 1, characterized in that, The number of tube sheets is set to 4-8.

9. The heat exchanger as claimed in claim 1, characterized in that, In a cavity with connecting holes in the heat exchange tubes, the number of connecting holes in the tube sheet increases with the flow direction of the fluid inside the heat exchange tubes.

10. The heat exchanger as claimed in claim 9, characterized in that, In a cavity with connecting holes in the heat exchange tubes, the number of connecting holes in the tube sheet increases with the direction of fluid flow inside the heat exchange tubes.

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