Heat exchanger and cold energy recovery device

Abstract

This application discloses a heat exchanger and a cold energy recovery device. The heat exchanger includes multiple U-shaped segments and connecting portions for connecting adjacent U-shaped segments. The U-shaped segments form a first fluid flow path and a second fluid flow path surrounding the first fluid flow path. The connecting portions are configured such that the first fluid flow path and the second fluid flow path of adjacent U-shaped segments are respectively connected, such that in at least a portion of the connecting portions, the first fluid flow path is not surrounded by the second fluid flow path. The heat exchanger and cold energy recovery device of this application have a compact structure, and the specific arrangement of the U-shaped segments ensures complete vaporization while improving cold energy utilization efficiency. Therefore, the power consumption of the refrigeration unit in the coolant circulation system is reduced.

Description

Technical Field

[0001] This application relates to the field of cold energy recovery. More specifically, it relates to a heat exchanger and a cold energy recovery device. More specifically, it relates to a device that uses a heat exchanger to convert cryogenic liquids into a gaseous state while effectively recovering cold energy. Background Technology

[0002] The expansion and vaporization of cryogenic liquids such as liquid oxygen, liquid argon, liquid nitrogen, and liquid helium contain enormous amounts of energy. Take liquid nitrogen as an example; its boiling point is -195.8℃. On-site nitrogen production requires energy-intensive equipment, which is typically located far from the application site. Therefore, nitrogen is usually transported to the application site in liquid form. However, nitrogen is ultimately mostly used in gaseous form, necessitating vaporization. The phase change of liquid nitrogen to gas through a vaporizer absorbs heat and generates cold energy. Plants with higher nitrogen demand release more cold energy as they obtain more nitrogen. Excessive cold energy can easily cause severe freezing, frost, or fogging on the vaporizer surface. A common solution is to provide a backup vaporizer to replace the frosted one. A common problem is the large footprint of vaporizers.

[0003] Furthermore, it cannot be flexibly adjusted according to the user's gas consumption. If gas consumption increases, the old cold energy recovery unit cannot be directly expanded or upgraded; it must be completely removed and replaced. If gas consumption decreases, excess cold energy will be wasted. Moreover, some existing heat exchangers, whose ends are connected only by flanges, are suitable for conventional cooling towers but not for situations involving phase change during heat exchange. Summary of the Invention

[0004] People have been thinking about how to effectively utilize this cold energy. Some industrial processes require the use of coolant. This coolant is supplied to the same or different equipment. If the cold energy generated by the expansion and vaporization of cryogenic liquids can be effectively transferred to the coolant, the waste of cold energy can be minimized.

[0005] One of the features of the heat exchanger and cold energy recovery device in this application is the structural design of the heat exchanger. Specifically, it uses a shell-and-tube heat exchanger, with the outer tube carrying the coolant and the inner tube carrying the cryogenic liquid (e.g., liquid oxygen, liquid nitrogen, liquid argon, liquid helium). The coolant and the cryogenic liquid exchange heat. The cryogenic liquid vaporizes into a gas and is supplied to the user. The coolant absorbs cold energy and cools down to become a cryogenic coolant, which is then used in the coolant circulation system. This simultaneously reduces the power consumption of the refrigeration unit in the coolant circulation system, thus reducing energy consumption and carbon dioxide emissions.

[0006] The first aspect of this application provides a heat exchanger, the heat exchanger including a plurality of U-shaped segments and a connecting portion for connecting adjacent U-shaped segments, wherein the U-shaped segments form a first fluid flow path and a second fluid flow path surrounding the first fluid flow path, and the connecting portion is configured such that the first fluid flow path and the second fluid flow path of adjacent U-shaped segments respectively dock, such that in at least a portion of the connecting portion, the first fluid flow path is not surrounded by the second fluid flow path.

[0007] Furthermore, the U-shaped segment includes an outer tube and an inner tube extending axially inside the outer tube. The first fluid to be vaporized (cryogenic liquid) flows in the inner tube, forming a first fluid flow path. An annular gap is formed between the inner tube and the outer tube, and the second fluid to be cooled (coolant) flows in the annular gap, forming a second fluid flow path.

[0008] Furthermore, the connecting portion includes a connecting portion body and a terminal portion. The connecting portion body includes a U-shaped segment connecting port and a terminal portion connecting port. The U-shaped segment connecting port is used to connect the U-shaped segment, and the terminal portion connecting port is used to connect the terminal portion.

[0009] Furthermore, the cross-sectional shape of the connecting part body is I-shaped, H-shaped, or convex.

[0010] Furthermore, the end connection port is welded to the end portion. The welded joint can be precisely inspected and ensures a proper seal at low temperatures, eliminating crevice corrosion and ensuring long-lasting reliability.

[0011] Furthermore, only the first fluid flows through the terminal portion.

[0012] Furthermore, the connecting body is an H-shaped hollow structure. Preferably, at least one end of the hollow structure is connected to a U-shaped segment, such that the first fluid flow path and the second fluid flow path extend in the connecting body, and at least one other end extends out of the connecting body and is welded to the end portion.

[0013] Furthermore, the connecting body is formed by welding two three-way valves.

[0014] Furthermore, the first fluid and the second fluid flow in the same direction within the heat exchanger.

[0015] Furthermore, the U-shaped segment has an integrally formed closed U-shaped end.

[0016] A second aspect of this application provides a cold energy recovery device, the cold energy recovery device comprising:

[0017] A cryogenic liquid source;

[0018] One coolant source;

[0019] A heat exchanger for exchanging heat between a cryogenic liquid and a coolant, the heat exchanger comprising a plurality of U-shaped segments and a connecting portion for connecting the U-shaped segments, including:

[0020] A first fluid inlet, through which a cryogenic liquid source supplies cryogenic liquid to the heat exchanger;

[0021] The first fluid outlet, through which the gas produced by the vaporization of the cryogenic liquid is supplied to the gas user end;

[0022] A second fluid inlet, through which the coolant source supplies coolant to the heat exchanger;

[0023] The heat exchanger supplies coolant to the coolant-using end via a second fluid outlet.

[0024] Furthermore, the coolant is water or ethylene glycol.

[0025] A third aspect of this application provides a modular device for recovering cold energy from cryogenic liquids. This modular device facilitates construction or modification by adding or removing each set of heat exchangers, achieving complete vaporization. The longitudinal cross-section of the heat exchangers in each modular device is substantially constant in height.

[0026] Furthermore, the modular device consists of multiple heat exchangers arranged in parallel or series. Multiple modules can be connected together to meet different gas flow requirements. A parallel arrangement is preferred. That is, the cryogenic liquid and coolant are proportionally distributed to each heat exchanger, which does not increase pressure drop and thus results in higher efficiency.

[0027] Furthermore, the modular device may include a hexahedral box having length, width, and height. The box has opposite horizontal top and bottom faces, two opposite vertical end faces, and two opposite vertical side faces. The top and bottom faces are defined by the box's length and width. The two vertical end faces are defined by the box's length and height. The two vertical side faces are defined by the box's width and height. The box encloses at least one chamber with a hexahedral volume, the at least one chamber having length, width, and height. The chamber includes at least one cold energy recovery device as described above, capable of enabling heat exchange, which secures adjacent modular devices.

[0028] Furthermore, at least one common support frame is located on the outer periphery of each modular unit, providing process and / or control and / or utility functions. Each modular unit can be connected to the common support frame via a flange. For example, the capacity of a set of modular units means that the (gas) flow rate at the first fluid outlet is 100 Nm³. 3 / h~150Nm3 / h.

[0029] Adding modular components can increase its cold energy recovery capacity and / or efficiency. Alternatively,

[0030] Removing the modular unit allows for a reduction in its cold energy recovery capacity and / or efficiency, and / or a reduction in the size of the unit.

[0031] The box is made of metal, preferably stainless steel or carbon steel.

[0032] Compared with the prior art, the technical solution provided in this application has the following advantages:

[0033] 1. The heat exchanger and cold energy recovery device of this application have a compact structure, and the specific U-shaped segment arrangement ensures complete vaporization while improving cold energy utilization efficiency. Therefore, the power consumption of the refrigeration unit in the coolant circulation system is reduced.

[0034] 2. The cold energy recovery unit can be expanded into a modular design, allowing for adjustments to gas consumption by adding or removing modules. After installation, the module configuration can be adjusted according to user needs. Furthermore, it can be quickly disassembled and relocated. Attached Figure Description

[0035] The advantages and spirit of this application can be further understood through the following detailed description and accompanying drawings.

[0036] Figure 1 This is a front view of the heat exchanger of this application.

[0037] Figure 2 This is a top view of the heat exchanger of this application.

[0038] Figure 3 This is an isometric view of the heat exchanger of this application.

[0039] In the diagram: 101 represents the U-shaped segment, 102 represents the connecting part, 1021 represents the end part, 1022 represents the connecting part body, 103 represents the U-shaped segment connection port, 104 represents the end part connection port, 105 represents the first fluid inlet, 106 represents the first fluid outlet, 107 represents the second fluid inlet, 108 represents the second fluid outlet, 109 represents the inner tube, and 110 represents the outer tube. Detailed Implementation

[0040] The specific embodiments of this application are described in detail below with reference to the accompanying drawings. However, this application should be understood as not being limited to the embodiments described below, and the technical concept of this application can be implemented in combination with other known technologies or other technologies with the same function as those known technologies.

[0041] In the following description of specific embodiments, in order to clearly illustrate the structure and working method, a number of directional terms will be used for description. However, terms such as "front", "rear", "left", "right", "outer", "inner", "outward", "inward", "axial", and "radial" should be understood as convenient terms and not as limiting terms.

[0042] In the following description of specific embodiments, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the purpose of simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. Furthermore, when the first structure is described as being positioned "above" or "below" the second structure, this should be understood to mean that the first structure is positioned further away from or closer to the horizontal plane.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and do not refer to a limitation on time sequence, quantity, or importance. They should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, but are merely used to distinguish one technical feature from another in this technical solution. Therefore, a feature specified with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified. Similarly, qualifiers such as "a" appearing herein do not refer to a limitation on quantity, but rather describe technical features not previously mentioned. Likewise, modifiers such as "approximately" or "approximately" preceding numerals generally include the number itself, and their specific meaning should be understood in conjunction with the context.

[0044] It should be understood that in this application, "at least one (item)" means one or more, and "more than one" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0045] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; a mechanical connection or an electrical connection; a direct connection or an indirect connection via an intermediate medium; or a connection within two components or an interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. "Fixed connection," "fixed connection," or "non-moving connection" is understood to refer to a connection between two or more structural members that is not constructed to provide relative movement. An embodiment of a fixed connection is a welded connection or a bolted connection, and in some cases, a weld and bolted connection. "Moving connection," "active," or "sliding connection" is understood to refer to a connection between two or more structural members that allows horizontal and / or vertical relative movement between the members under extreme dynamic loads. Such connections typically do not allow movement under static loads or general dynamic loads (e.g., those imposed by light / moderate wind forces).

[0046] Terminology Explanation

[0047] The terms “unit,” “item,” “object,” and “module” described in this specification refer to a unit for performing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0048] In this document, “upstream” and “downstream” are defined relative to the expected flow of fluid, with the upstream end corresponding to the end closest to the inlet where the fluid is introduced and the downstream end corresponding to the end where the fluid exits the outlet.

[0049] The terms "high pressure" and "low pressure" mean that high pressure is higher than low pressure, so the difference between the two may be relatively small.

[0050] The terms "high temperature" and "low temperature" mean that high temperature is higher than low temperature, so the difference between the two may be relatively small.

[0051] As used in this article, "heat exchange device," "heat exchanger," "heat exchanger," and "multi-tube heat exchanger" can refer to a double-pipe / tube-in-tube heat exchanger. It involves inserting an inner tube into an outer tube, allowing heat exchange between the fluid flowing within the inner tube and between the inner and outer tubes. A heat exchanger mainly consists of multiple long tubes spaced a certain distance apart and arranged parallel or non-parallel to each other. These long tubes have a flattened, elongated elliptical cross-section in the axial direction. Taking a double-tube heat exchanger as an example, a tube-in-tube heat exchanger includes an inner tube and an outer tube surrounding the outer circumference of the inner tube, forming a flow path between the inner and outer tubes.

[0052] As used herein, fluid refers to a continuous, amorphous substance whose molecules move freely toward each other and tend to take the shape of their container, such as, but not limited to, liquids or gases.

[0053] As used in this article, "cryogenic liquids" are partially liquid during transport due to low or even cryogenic temperatures. These can be liquid nitrogen or liquid argon, hydrogen, helium, neon, methane, and carbon monoxide, etc. Even if a phase change occurs in the cryogenic liquid within the heat exchanger, this article refers to both the cryogenic liquid and the gas produced after the phase change as the first fluid.

[0054] Unless otherwise clearly indicated, each aspect or embodiment defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0055] like Figure 1 and Figure 3 As shown, the heat exchanger used herein includes multiple U-shaped segments 101 and connecting portions 102 for connecting the U-shaped segments.

[0056] Each U-shaped segment 101 may be the same as or different from each other. For example, the U-shaped segments 101 may differ from each other in terms of length or diameter of one or more tubes. Adjacent U-shaped segments 101 are separated by a gap.

[0057] like Figure 2 As shown, the U-shaped segment 101 includes an inner tube 109 and an outer tube 110 surrounding the outer surface of the inner tube. The inner tube 109 extends axially inside the outer tube 110. In the U-shaped segment 101, the inner tube 109 is inserted into the outer tube 110, that is, the axis of the inner tube 109 and the axis of the outer tube 110 coincide. The inner tube 109 of any U-shaped segment 101 exits from the outer tube 110 of the preceding U-shaped segment 101, passes through the connecting portion 102, and then enters the outer tube 110 of the following U-shaped segment 101, to ensure that at least one section of the inner tube 109 and the outer tube 110 does not involve circling or nesting. As an example, such as Figure 1As shown, the non-nested portion is the end portion 1021 of the connecting portion 102. Exemplarily, this end portion 1021 is equivalent to an "exposed" inner tube structure. This non-nested end portion 1021 facilitates observation of the vaporization state. If supercooling occurs, frost may form on the end portion 1021. Furthermore, the solder joints of the end connection port 104 are all exposed, facilitating leak detection and repair at the solder joints.

[0058] The connecting body 1022 includes a U-shaped segment connecting port 103 and an end connecting port 104. The U-shaped segment connecting port 103 is used to connect the U-shaped segment 101. The end connecting port 104 is used to connect the end portion 1021. The cross-sectional shape of the connecting body 1022 is I-shaped, H-shaped, or convex. As an example only, the connecting body 1022 can be welded from two three-way valves.

[0059] The first and second fluid flow paths of adjacent U-shaped segments 101 are connected separately by connecting parts 102. "Separately connected" here means that at least a portion of the first fluid flow path is not surrounded by the second fluid flow path, but rather connects as an independent flow path to the first fluid flow path of the next U-shaped segment. In other words, the total axial length of the inner tube in the heat exchanger is greater than the total axial length of the outer tube.

[0060] The U-shaped end of the U-shaped segment 101 is a one-piece closed end. While maintaining the coaxiality of the inner tube 109 and the outer tube 110, the entire segment 101 can be bent to cope with the stress caused by the thermal expansion and contraction of the cryogenic liquid. This is because temperature differences cause the inner tube to expand relative to the outer tube along its horizontal axis. According to an advantageous design, during manufacturing, the inner tube in its initial state is inserted into the outer tube, and then the outer tube is shaped and processed. This method results in a consistent shape at the end sections of the inner and outer tubes. This provides space for synchronized expansion and contraction of the inner and outer tubes, thereby stabilizing and improving the stress caused by the thermal expansion and contraction of the fluid. Taking liquid nitrogen as an example, the inner tube of a 1.5-meter-long U-shaped segment will experience a contraction force of 1 to 4 cm. Using traditional welding or other fixing methods here would highly likely result in deformation or cracking.

[0061] The first fluid inlet 105 and the second fluid inlet 107 are both located at the bottom of the heat exchanger. The first fluid and the second fluid pass through each U-shaped section 101 from bottom to top and are led out from the first fluid outlet 106 and the second fluid outlet 108.

[0062] The outer tube 110 and the inner tube 109 are preferably made of metal, especially steel, and particularly stainless steel.

[0063] In the aforementioned heat exchanger, the cryogenic liquid and coolant flow in the same direction. Furthermore, both the cryogenic liquid and coolant flow from bottom to top. This ensures that the vaporized gas continuously flows along the inner tube 109 towards the first fluid outlet 106, eventually reaching thermal equilibrium with the coolant. This is significantly different from the counter-current flow pattern of two fluids in conventional shell-and-tube heat exchangers.

[0064] Fluids can exchange heat without direct contact with each other. The pipe diameter is selected based on the processing capacity. A larger diameter outer pipe is fitted inside a smaller diameter inner pipe. The cross-section includes two outer pipe walls and two inner pipe walls in both the vertical and horizontal directions. This effectively increases the vaporization area and improves vaporization efficiency.

[0065] Specific embodiments of this application are described in detail below with reference to the accompanying drawings. Embodiments are present throughout multiple views of the drawings. The same reference numerals in the embodiments generally denote the same or corresponding elements. Therefore, the description of the embodiments is incorporated herein by reference, and descriptions of common subject matter across embodiments are generally not repeated herein.

[0066] Taking a set of cold energy recovery unit modules as an example, the capacity of each modular unit represents a (gas) flow rate of 100 Nm³ at the first fluid outlet. 3 / h. Water is used as a coolant to vaporize liquid nitrogen while recovering the cold energy from the liquid nitrogen into the water.

[0067] Taking a U-shaped segment 101 and a connecting part 102 for connecting the U-shaped segments as an example, the outer tube 110 is a continuous seamless tube with a length of 2460 mm, a diameter of 34 mm, and a wall thickness of 2 mm. The inner tube 109 is a continuous seamless tube with a diameter of 18 mm, a wall thickness of 2 mm, and a length of 2840 mm. Using the aforementioned multiple U-shaped segments 101 and connecting parts 102, multiple sets of resistance temperature detectors (RTDs) are installed on the surface to test heat transfer and the minimum required pipe length. It was found that complete vaporization can be achieved with a heat exchanger inner tube of 15 to 18 meters in total length.

[0068] The liquid nitrogen temperature at the first fluid inlet 105 is below -150℃, and the inlet pressure is approximately 1.2 MPa. The nitrogen flow rate at the first fluid outlet 106 is 100 Nm³. 3 / h, temperature greater than 7℃, outlet pressure approximately 1.2MPa.

[0069] The water flow rate at the second fluid inlet 107 is 2.5 Nm. 3 The flow rate is approximately 14℃ / h, and the inlet pressure is approximately 0.2–0.5 MPa. The water flow rate at the second fluid outlet 108 is 2.5 Nm³ / h. 3 The flow rate is approximately 7°C, and the outlet pressure is approximately 0.2–0.5 MPa.

[0070] The heat transfer efficiency can be determined based on the ratio of the energy recovered from cooling water to the heat generated by nitrogen vaporization. Tests have shown that the heat transfer efficiency of this cold energy recovery device is close to 90%.

[0071] The embodiments described in this specification are merely preferred embodiments of this application. These embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of this application. Any technical solutions that can be obtained by those skilled in the art based on the concept of this application through logical analysis, reasoning, or limited experimentation should be within the scope of this application.

Claims

1. A heat exchanger, characterized in that, The heat exchanger includes a plurality of U-shaped segments and a connecting portion for connecting adjacent U-shaped segments, wherein the U-shaped segments form a first fluid flow path and a second fluid flow path surrounding the first fluid flow path, and the connecting portion is configured such that the first fluid flow path and the second fluid flow path of adjacent U-shaped segments are respectively connected, such that in at least a portion of the connecting portion, the first fluid flow path is not surrounded by the second fluid flow path.

2. The heat exchanger according to claim 1, characterized in that, The U-shaped segment includes an outer tube and an inner tube extending axially inside the outer tube. The first fluid to be vaporized flows in the inner tube, forming a first fluid flow path. An annular gap is formed between the inner tube and the outer tube, and the second fluid to be cooled flows in the annular gap, forming a second fluid flow path.

3. The heat exchanger according to claim 1 or 2, characterized in that, The connecting part includes a connecting part body and an end part. The connecting part body includes a U-shaped segment connecting port and an end part connecting port. The U-shaped segment connecting port is used to connect the U-shaped segment, and the end part connecting port is used to connect the end part.

4. The heat exchanger according to claim 3, characterized in that, The cross-sectional shape of the connecting part body is I-shaped, H-shaped, or convex.

5. The heat exchanger according to claim 3, characterized in that, The end connection port is welded to the end portion.

6. The heat exchanger according to claim 3, characterized in that, Only the first fluid flows through the terminal portion.

7. The heat exchanger according to claim 1 or 2, characterized in that, The first and second fluids flow in the same direction in the heat exchanger.

8. The heat exchanger according to claim 1 or 2, characterized in that, The U-shaped segment has an integrally formed closed U-shaped end.

9. A cold energy recovery device, characterized in that, The cold energy recovery device includes: A cryogenic liquid source; One coolant source; A heat exchanger for exchanging heat between a cryogenic liquid and a coolant, the heat exchanger comprising a plurality of U-shaped segments and connecting portions for connecting the U-shaped segments, and: A first fluid inlet, wherein the cryogenic liquid source supplies cryogenic liquid to the heat exchanger via the first fluid inlet; The first fluid outlet, through which the gas produced by the vaporization of the cryogenic liquid is supplied to the gas-using end; A second fluid inlet, through which the coolant source supplies coolant to the heat exchanger; The heat exchanger supplies coolant to the coolant-using end via the second fluid outlet.

10. A modular device for recovering cryogenic liquid cold energy, characterized in that, The modular device consists of multiple heat exchangers arranged in parallel or series.

Images