Air-cooled heat exchanger

Abstract

An air-cooled heat exchanger includes a bay having tube bundles that receive a process fluid. A framework supports a fan shroud and the bay with the single fan shroud positioned adjacent to the tube bundles. A single fan is rotatably positioned within the fan shroud so that rotation of the fan causes air flow over the tube bundles so that process fluids within the tube bundles are cooled. A fan motor is mounted on the framework and rotates the fan.

Description

AIR-COOLED HEAT EXCHANGERCLAIM OF PRIORITY

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 724,526, filed November 25, 2024, the contents of which are hereby incorporated by reference.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to systems for cooling fluids in industrial processes and, more particularly, to an air-cooled heat exchanger.BACKGROUND

[0003] Air-cooled heat exchangers are widely used in a variety of industries for cooling process fluid streams using a second cooling fluid stream. Examples of applications in such industries include, but are not limited to, natural gas liquefaction (and other processing) plants, chemical plants, power plants and petroleum refineries.

[0004] Air-cooled heat exchangers, as the name implies, use air as the second cooling fluid and employ fans to drive the air over tube bundles through which the process fluids being cooled flow. The air absorbs heat from the tube bundles therefore lowering the temperature of the process fluids within the tube bundles. Air-cooled heat exchangers may be of the induced draft exchanger type or the forced draft exchanger type. Induced draft exchangers feature tube bundle(s) located on the suction side of the fan (with the fan typically positioned above the bundle). Forced draft exchangers feature tube bundle(s) located on the discharge side of the fan (with the fan typically positioned below the bundle). The tube bundles in both types of designs are typically organized in bays with each bay containing one or more tube bundles serviced by one or more fans. Each bay also includes the structure for holding the tube bundle(s) and fan(s), plenum(s) and other attendant equipment.1

[0005] In applications that use air-cooled heat exchangers (ACHXs) for cooling of the process fluids, the ACHXs represent a significant percentage of the plant plot area, and the performance of the ACHXs is typically important to the plant processing or production rate.Improvements in ACHX efficiency can allow for a significant reduction in ACHX plot space (and therefore lower total installed cost) and / or colder process outlet temperatures(and therefore higher processing or production rates).SUMMARY OF THE DISCLOSURE

[0006] There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices and systems described and claimed below.These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.

[0007] In one aspect, an air-cooled heat exchanger includes a bay having a plurality of tube bundles. Each of the plurality of tube bundles is configured to receive a process fluid. A framework supports a single fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles. A single fan is rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles are cooled. A fan motor is mounted on the framework and is configured to rotate the fan.

[0008] In another aspect, an installation of air-cooled heat exchangers includes first and second air-cooled heat exchangers. Each of the first and second air-cooled heat exchangers includes a bay having a plurality of tube bundles with each tube bundle2configured to receive a process fluid. A framework is configured to support a single fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles. A single fan is rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles are cooled. A fan motor is mounted on the framework and is configured to rotate the fan.

[0009] Each of the plurality of tube bundles includes a header containing an inlet chamber and an outlet chamber and an inlet nozzle in fluid communication with the inlet chamber and an outlet nozzle in fluid communication with the outlet chamber. A plurality of U shaped heat exchange tubes extends between, and are in fluid communication with, the inlet and outlet chambers of the header. A pair of opposing elongated side plates has the plurality of U-shaped heat exchanger tubes positioned therebetween. An elongated end plate is connected to the pair of opposing elongated side plates and extends parallel to the header. A first elongated side plate of the first heat exchanger bundle is positioned adjacent to a second elongated side plate of the second tube bundle and headers of the plurality of tube bundles of the first and second air-cooled heat exchangers are generally in alignment along their longitudinal axes.

[0010] A system for liquefying natural gas includes a liquefier heat exchanger including a liquefying passage configured to receive a stream of natural gas and a refrigeration passage configured to receive a stream of mixed refrigerant so that the natural gas stream is cooled and liquefied in the liquefying passage by indirect heat transfer with the stream of mixed refrigerant in the refrigeration passage. A mixed refrigerant compression system includes a mixed refrigerant compressor that has an inlet in fluid communication with an outlet of the refrigeration passage. A mixed refrigerant condenser has an inlet in fluid3communication with an outlet of the mixed refrigerant compressor. The mixed refrigerant condenser has an outlet in fluid communication with the refrigeration passage of the liquefier heat exchanger. The mixed refrigerant condenser includes a bay having a plurality of tube bundles with each configured to receive a process fluid. A framework supports a single fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles. A single fan is rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles are cooled. A fan motor is mounted on the framework and configured to rotate the fan.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a perspective view of an embodiment of the air-cooled heat exchanger of the disclosure.

[0012] Fig. 2 is top plan view of an installation of multiple air-cooled heat exchangers in an embodiment of the disclosure.

[0013] Fig. 3 is side elevational view of an installation of multiple air-cooled heat exchangers in an embodiment of the disclosure.

[0014] Fig. 4 is an end elevation view of the installation of Fig. 3.DETAILED DESCRIPTION OF EMBODIMENTS

[0015] A more detailed description of the system and method in accordance with the present disclosure is set forth below. It should be understood that the description below of specific systems and methods is intended to be exemplary, and not exhaustive of all possible variations or applications. Thus, the scope of the disclosure is not intended to be4limiting and should be understood to encompass variations or embodiments that would occur to persons of ordinary skill.

[0016] As used herein, and as known in the art, a heat exchanger is that device or an area in the device wherein indirect heat exchange occurs between two or more streams at different temperatures, or between a stream and the environment.

[0017] As used herein, the terms “communication”, “communicating”, and the like generally refer to fluid communication unless otherwise specified.

[0018] Reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures for shared elements or components without additional description in the specification in order to provide context for other features.

[0019] In the claims, letters are used to identify claimed steps (e.g. a., b. and c.). These letters are used to aid in referring to the method steps and are not intended to indicate the order in which the claimed steps are performed, unless and only to the extent that such order is specifically recited in the claims.

[0020] A non-limiting example of an application within which an embodiment of the aircooled heat exchanger of the disclosure may be used is a natural gas liquefaction system.Natural gas is often liquefied for storage and transport. Systems for liquefying natural gas typically chill the gas through indirect heat exchange with a refrigerant in a liquefier heat exchanger (which is typically located inside of an insulated “cold box”). Efficiency in terms of energy usage is a primary issue for such liquefaction systems. Use of a mixed refrigerant in the refrigeration cycle(s) for the system increases efficiency in that the warming curve of the refrigerant more closely matches the cooling curve of the natural gas.5

[0021] The refrigeration cycle for the liquefying system will typically include a compression system for conditioning or processing the mixed refrigerant after it is used for cooling in the liquefier heat exchanger. Processing of the mixed refrigerant may include separating liquid and vapor phases so that they may be directed to portions of the heat exchanger to provide more efficient cooling. The mixed refrigerant compression system typically includes one or more stages, with each stage including a compressor, a condenser and a separation and liquid accumulator device. Mixed refrigerant vapor exiting the compressor is cooled in the condenser, and the resulting two-phase or mixed phase stream is directed to the separation and liquid accumulator device, from which vapor and liquid exit for further processing and / or direction to the liquefaction heat exchanger.Embodiments of the air-cooled heat exchanger of the embodiment may be used as the condenser in the mixed refrigerant compression system.

[0022] Examples of such natural gas liquefaction and mixed refrigerant compression systems are provided in commonly assigned U.S. Patent No. 9,441,877 to Gushanas et al.,U.S. Patent No. 10,480,851 to Ducote Jr. et al., U.S. Patent No. 10,060,671 to Ducote Jr. et al., U.S. Patent No. 10,663,221 to Ducote Jr. et al. and 11,187,457 to Ducote Jr. et al., the contents of each of which are hereby incorporated by reference.

[0023] While embodiments of the disclosure are described below in terms of a natural gas liquefaction or liquid natural gas (LNG) plant, it is to be understood that the innovation may be used in general refinery processes, chemical processes, power plants and other industrial fluid cooling applications.

[0024] Prior art air-cooled heat exchangers for LNG plants are typically designed with a single tube bundle per bay and multiple fans per bay. The bundle width (perpendicular to the longitudinal axis of the tube bundle) is typically approximately 20 feet or less. Fan diameters of approximately 16 feet or lower, and fan motors with approximately 60 hp or6lower are typically used. Most designs have included aluminum (Al) fans, but there have been some fiber reinforced plastic (FRP) fans utilized.

[0025] In accordance with the disclosure, the air-cooled heat exchanger described below may be used in place of standard single tube bundle per bay coolers in LNG plants.Embodiments of the air-cooled heat exchanger of the disclosure utilize significantly larger diameter fans resulting in a more efficient air-cooled heat exchanger design. This more efficient air-cooled heat exchanger design may lead to a combination of improved air cooling performance, reduced overall size and / or reduced overall fan motor power required.

[0026] An embodiment of the air-cooled heat exchanger of the disclosure is indicated in general at 10 in Fig. 1. As will be explained in greater detail below, the air-cooled heat exchanger 10 is an induced draft air-cooled heat exchanger.

[0027] As illustrated in Fig. 1, the heat exchanger 10 includes a single bay, indicated in general at 12, that includes three tube bundles, indicated in general at 14a, 14b and 14c.Tube bundle 14a includes a header, indicated in general at 16, having inlet nozzles 18 and20 and outlet nozzles 22 and 24. Header 16 includes an internal wall, indicated in phantom at 26, that divides the interior of the header into an upper fluid inlet chamber 28 and a lower fluid outlet chamber 32. While two inlet nozzles and two outlet nozzles are illustrated for header 16, alternative numbers of inlet and outlet nozzles may be used.

[0028] As is known in the art, a number of U-shaped heat exchange tubes 34 have inlets in fluid communication with the upper fluid inlet chamber 28 of header 16 and outlets in fluid communication with the lower fluid outlet chamber 32 of header 16. As a result, process fluid (in this case mixed refrigerant) enters the inlet nozzles 18 and 20 of header16 and is directed through the inlet chamber of the header and into the tubes for cooling.The cooled mixed refrigerant exits the tubes through the outlet chamber of the header and7the exit nozzles 22 and 24. Alternative tube and header configurations known in the art may be used in place of the U-shaped tubes 34 and header 16 including, but not limited to, serpentine tubes.

[0029] With continued reference to Fig. 1, tube bundle 14a includes a pair of opposing elongated side plates 42 and 44 with the tubes 34 positioned therebetween and that support the header 16. Tube bundle 14a also includes an elongated end plate 45 that runs parallel to the header 16.

[0030] Each of tube bundles 14b and 14c features a construction similar to that of tube bundle 14a. As illustrated in Fig. 1, the tube bundles 14a-14c are positioned in a side-byside arrangement with tube bundle 14b sandwiched between tube bundles 14a and 14c.More specifically, an elongated side plate of tube bundle 14a is adjacent to one elongated side plate of tube bundle 14b with the remaining elongated side plate of tube bundle 14b adjacent to an elongated side plate of tube bundle 14c. The adjacent elongated side plates may or may not be abutting each other. The headers of tube bundles 14a- 14c are generally in alignment along their longitudinal axes. While three tube bundles 14a-14c are illustrated in the bay 12 of the embodiment of Fig. 1, the air-cooled heat exchanger of the disclosure may instead feature two or more than three tube bundles within the bay.

[0031] The elongated side plates of tube bundles 14a, 14b and 14c, and thus the U-shaped heat exchange tubes, end plate and header of each tube bundle, are supported by transverse elongated support beams 46, 48, 50, 52 and 54 that extend perpendicular to the longitudinal axes of the tube bundle elongated side plates. The bay 12 thus formed is supported on a surface by leg assemblies. More specifically, elongated support beams 46,48, 50, 52 and 54 are supported at first end portions by leg assemblies 56, 58 and 62.Opposite end portions of elongated support beams 46, 48, 50, 52 and 54 are supported by similar leg assemblies. As examples only, elongated support beams 46, 48, 50, 52 and 548may be steel I-beams while the leg assemblies 56, 58 and 62 may be constructed from steel L-beams or I-beams. Alternative types of beams or members and materials known in the art may be used instead.

[0032] A fan shroud 64 is mounted to a deck 66 which is supported via framework 68 over the tube bundles 14a, 14b and 14c. The framework, which may be constructed of steel I-beams and / or L-beams, includes bottom portions with are mounted to the top edges of the elongated side plates of tube bundles 14a, 14b and 14c.

[0033] As illustrated in Fig. 2, a fan opening 72 is provided in the fan deck 66. The fan shroud 64 (Fig. 1) features a bottom edge that is sized so as to border the circumference of the fan opening 72. A fan 74 (Fig. 2) is positioned within a bottom portion of the fan shroud and is driven by a motor (76 in Figs. 1 and 2) via a horizontally extending drive shaft 78 and a gearbox (not shown) to which the hub 77 of the fan is rotatably connected.The gearbox serves as an interface between the drive shaft 78 and the fan 74 so that a single speed electric motor 76 may be used. Motor 76 is mounted to the fan deck 66.

[0034] When fan 74 (Fig. 2) is operating, an induced draft is created for the tube bundles14a, 14b and 14c (Fig. 1) whereby air is pulled up across the heat exchange tubes of the tube bundles so that process fluid (mixed refrigerant in the present example) within the tubes is cooled. The air continues to travel upwards due to the fan operation and exhausts / exits the top of the fan shroud 64 (Fig. 1).

[0035] In an alternative embodiment, the framework may be configured so that the tube bundles 14a-14c are positioned above the fan and fan shroud, so that air is blown by the fan over the tube bundles to form a forced draft exchanger.

[0036] As illustrated in Figs. 2, 3 and 4, multiple air-cooled heat exchangers of the disclosure, indicated at WOa-lOOh may be positioned adjacently in installations with the9headers 116a-l 16h of their tube bundles in alignment along their longitudinal axes to provide a compact and efficient plot layout.

[0037] It should be noted that the embodiment of the air-cooled heat exchanger of the disclosure indicated at lOOa-lOOh in Figs. 2-4 differs from the embodiment of Fig. 1 in that the end portions of the tube bundles (such as 34 of tube bundle 14a) of Fig. 1 extend longitudinally out from underneath the fan deck 66, while the entireties of the tube bundles of each air-cooled heat exchanger lOOa-lOOh in Figs. 2-4 are positioned under the corresponding fan deck. In addition, the numbers of air-cooled heat exchangers illustrated in the installations of Figs. 2-4 are in no way limiting.

[0038] The multiple tube bundles (preferably of the same service) of the air-cooled heat exchangers of Figs. 1-4 provide each air-cooled heat exchanger with a bay that may be significantly wider than a standard cooler bay allowing for larger fan diameters. Fan diameters (indicated by arrows 70 of Fig. 2) in the air-cooled heat exchangers of the disclosure are preferably in the range of approximately 24 feet to approximately 36 feet.Large diameter fans may have a significantly higher fan static efficiency when compared to smaller standard diameter fans of the same design / material type. Moreover, larger fans in general are more efficient in moving air because of a Reynolds number efficiency improvement, improved blade-to-hub ratio and lower velocity pressure losses.

[0039] This significant improvement in static fan efficiency allows for a meaningful reduction in air-cooled heat exchanger plot area and / or reduced air-cooled heat exchanger temperature approach, and therefore increased LNG production in LNG plant applications.Additionally, a reduced bay count and fan count leads to reduced installation costs.

[0040] Examples of fans suitable for use in the air-cooled heat exchanger of the disclosure include the Tuf-Lite® line of fans available from Hudson Products Corporation of ChartIndustries, Inc., Ball Ground, Georgia.10

[0041] A variable frequency drive motor (VFD) may be substituted for the single speed electric motor 76. VFDs reduce or eliminate process control issues for cooling services that require process control. VFDs also allow for the use of fan direct drive motors which removes drive shafts, belts and / or gears and which also improves reliability and availability and potentially sound reduction.

[0042] There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices, and systems described and claimed below.These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.

[0043] While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.11

Claims

CLAIMSWhat is claimed is:

1. An air-cooled heat exchanger including: a. a bay including a plurality of tube bundles, each of said plurality of tube bundles configured to receive a process fluid; b. a single fan shroud; c. a framework configured to support the fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles; d. a single fan rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles arc cooled; and e. a fan motor mounted on the framework and configured to rotate the fan.

2. The air-cooled heat exchanger of claim 1 wherein the fan has a diameter in the range of approximately 24 feet to approximately 36 feet.

3. The air-cooled heat exchanger of claim 1 wherein the plurality of tube bundles receive process fluid that is part of a same service.

4. The air-cooled heat exchanger of claim 1 wherein the framework is configured to support the fan shroud over the bay so that the air cooled heat exchanger is an induced draft exchanger.

125. The air-cooled heat exchanger of claim 1 wherein the framework is configured to support the fan shroud under the bay so that the air cooled heat exchanger is a forced draft exchanger.

6. The air-cooled heat exchanger of claim 1 wherein the fan motor is a variable frequency drive motor that is configured to directly drive the fan.

7. The air-cooled heat exchanger of claim 1 further comprising a gearbox operatively connected to the fan and a fan drive shaft operatively connected to the fan motor and the gearbox and wherein the fan motor is a single speed motor.

8. The air-coolcd heat exchanger of claim 1 wherein each of the plurality of tube bundles includes: i) a header containing an inlet chamber and an outlet chamber and an inlet nozzle in fluid communication with the inlet chamber and an outlet nozzle in fluid communication with the outlet chamber; ii) a plurality of U-shaped heat exchange tubes extending between and in fluid communication with the inlet and outlet chambers of the header; iii) a pair of opposing elongated side plates with the plurality of U-shaped heat exchanger tubes positioned therebetween; iv) an elongated end plate connected to the pair of opposing elongated side plates and extending parallel to the header.

139. The air-cooled heat exchanger of claim 8 further comprising a fan deck mounted upon the framework wherein said fan shroud is mounted to the fan deck, said fan deck including a fan opening having a circumference that is bordered by an edge of the fan shroud.

10. The air-cooled heat exchanger of claim 1 further comprising a plurality of leg assemblies configured to support the framework on a surface.11 . An installation of air-cooled heat exchangers comprising: a. first and second air-cooled heat exchangers wherein each of said first and second air-cooled heat exchanger includes: i. a bay including a plurality of tube bundles, each of said plurality of tube bundles configured to receive a process fluid; a single fan shroud; iii. a framework configured to support the fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles; iv. a single fan rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles are cooled; v. a fan motor mounted on the framework and configured to rotate the fan; vi. each of said plurality of tube bundles including:

141. a header containing an inlet chamber and an outlet chamber and an inlet nozzle in fluid communication with the inlet chamber and an outlet nozzle in fluid communication with the outlet chamber;2. a plurality of U-shaped heat exchange tubes extending between and in fluid communication with the inlet and outlet chambers of the header;3. a pair of opposing elongated side plates with the plurality ofU-shaped heat exchanger tubes positioned therebetween;4. an elongated end plate connected to the pair of opposing elongated side plates and extending parallel to the header; b. wherein a first elongated side plate of the first heat exchanger bundle is positioned adjacent to a second elongated side plate of the second tube bundle and headers of the plurality of tube bundles of the first and second air-cooled heat exchangers are generally in alignment along their longitudinal axes.

12. A system for liquefying natural gas comprising: a. a liquefier heat exchanger including a liquefying passage configured to receive a stream of natural gas and a refrigeration passage configured to receive a stream of mixed refrigerant so that the natural gas stream is cooled and liquefied in the liquefying passage by indirect heat transfer with the stream of mixed refrigerant in the refrigeration passage; b. a mixed refrigerant compression system including: i. a mixed refrigerant compressor having an inlet in fluid15communication with an outlet of the refrigeration passage; ii. a mixed refrigerant condenser having an inlet in fluid communication with an outlet of the mixed refrigerant compressor, said mixed refrigerant condenser having an outlet in fluid communication with the refrigeration passage of the liquefier heat exchanger; c. said mixed refrigerant condenser including: a bay including a plurality of tube bundles, each of said plurality of tube bundles configured to receive a process fluid; a single fan shroud; iii. a framework configured to support the fan shroud and the bay with the single fan shroud positioned adjacent to the plurality of tube bundles; iv. a single fan rotatably positioned within the fan shroud with the fan shroud configured so that rotation of the fan causes air flow over the plurality of tube bundles so that process fluids within the plurality of tube bundles are cooled; and v. a fan motor mounted on the framework and configured to rotate the fan.

13. The system for liquefying natural gas of claim 12 wherein the fan of the mixed refrigerant condenser has a diameter in the range of approximately 24 feet to approximately 36 feet.1614. The system for liquefying natural gas of claim 12 wherein the framework of the mixed refrigerant condenser is configured to support the fan shroud over the bay so that the air-cooled heat exchanger is an induced draft exchanger.

15. The system for liquefying natural gas of claim 12 wherein the framework of the mixed refrigerant condenser is configured to support the fan shroud under the bay so that the air-cooled heat exchanger is a forced draft exchanger.

16. The system for liquefying natural gas of claim 12 wherein the fan motor of the mixed refrigerant condenser is a variable frequency drive motor that is configured to directly drive the fan.

17. 1'he system for liquefying natural gas of claim 12 wherein the mixed refrigerant condenser includes a gearbox operatively connected to the fan and a fan drive shaft operatively connected to the fan motor and the gearbox and wherein the fan motor is a single speed motor.

18. The system for liquefying natural gas of claim 12 wherein each of the plurality of tube bundles of the mixed refrigerant condenser includes:

1. a header containing an inlet chamber and an outlet chamber and an inlet nozzle in fluid communication with the inlet chamber and an outlet nozzle in fluid communication with the outlet chamber;2. a plurality of U-shaped heat exchange tubes extending between and in fluid communication with the inlet and outlet chambers of the header;173. a pair of opposing elongated side plates with the plurality ofU-shaped heat exchanger tubes positioned therebetween;4. an elongated end plate connected to the pair of opposing elongated side plates and extending parallel to the header.

19. The system for liquefying natural gas of claim 12 wherein the mixed refrigerant condenser includes a fan deck mounted upon the framework wherein said fan shroud is mounted to the fan deck, said fan deck including a fan opening having a circumference that is bordered by an edge of the fan shroud.

20. The system for liquefying natural gas of claim 12 wherein the mixed refrigerant condenser includes a plurality of leg assemblies configured to support the framework on a surface.18

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