EP4296600A1

EP4296600A1 - Shell and tube isolation in heat exchanger

Info

Publication number: EP4296600A1
Application number: EP23179347.2A
Authority: EP
Inventors: Luis Avila; Valerie LISI
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2022-06-22
Filing date: 2023-06-14
Publication date: 2023-12-27
Also published as: CN117268158A; US20230417496A1

Abstract

A heat exchanger (22, 18) includes a heat exchanger shell (36) formed from a first metal material, and a plurality of heat exchanger tubes (38) extending through a plurality of tube openings (46) in the heat exchanger shell (36). The plurality of heat exchanger tubes (38) are formed from a second metal material different from the first metal material. A galvanic isolator (48) is located at each tube opening of the plurality of tube openings (46), radially between the tube opening (46) and the corresponding heat exchanger tube (38) of the plurality of heat exchanger tubes (38). The galvanic isolator (48) is configured to mitigate a galvanic reaction between the heat exchanger shell (36) and the plurality of heat exchanger tubes (38).

Description

The present invention pertains to the art of heat exchangers, and more specifically to corrosion mitigation for water cooled chillers.
In a water-cooled chiller, a flow of refrigerant is directed through one or more shell and tube heat exchangers, such as an evaporator and a condenser, via a plurality of heat exchanger tubes. The heat exchanger tubes are exposed to water inside the heat exchanger, which is used as a heat transfer fluid.
These heat exchanger tubes are suspended within the shell of the chiller, passing through steel end plates. An issue with galvanic corrosion may arise when the heat exchanger tubes are formed from aluminum. The steel construction is advantageous for medium to large chillers because of its strength given the size of the units. The use of aluminum heat exchanger tubes allows for more technical and intricate shapes and features of the tubes. The steel to aluminum galvanic pair, if not mitigated, is very strong and highly detrimental to the aluminum heat exchanger tubes.
A first aspect of the invention provides a heat exchanger including a heat exchanger shell formed from a first metal material, and a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell. The plurality of heat exchanger tubes are formed from a second metal material different from the first metal material. A galvanic isolator is located at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding heat exchanger tube of the plurality of heat exchanger tubes. The galvanic isolator is configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.
The heat exchanger shell may be formed from steel, and the plurality of heat exchanger tubes are formed from aluminum.
The galvanic isolator may be formed from a non-metallic material.
The galvanic isolator may be sleeve installed to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
The galvanic isolator may be a coating applied to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
The coating may be a polytetrafluoroethylene (PTFE) material.
The galvanic isolator may have a thickness in a range of 0.0005 inches to 0.001 inches.
Installation of the plurality of heat exchanger tubes into the plurality of tube openings may seal the plurality of tube openings.
A second aspect of the invention provides a chiller system including a refrigerant circuit having a flow of refrigerant circulating therethrough, and a fluid circuit having a flow of heat transfer fluid circulating therethrough. The fluid circuit is operably connected to the refrigerant circuit at a heat exchanger assembly to transfer thermal energy between the flow of refrigerant and the fluid circuit. The heat exchanger assembly includes a heat exchanger shell formed from a first metal material, and a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell. The plurality of heat exchanger tubes are formed from a second metal material different from the first metal material. A galvanic isolator is located at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding evaporator tube of the plurality of heat exchanger tubes. The galvanic isolator is configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.
The heat exchanger shell may be formed from steel, and the plurality of heat exchanger tubes are formed from aluminum.
The galvanic isolator may be formed from a non-metallic material.
The galvanic isolator may be sleeve installed to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
The galvanic isolator may be a coating applied to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
The coating may be a polytetrafluoroethylene (PTFE) material.
The galvanic isolator may have a thickness in a range of 0.0005 to 0.001 inches.
Installation of the plurality of heat exchanger tubes into the plurality of tube openings may seal the plurality of tube openings.
The heat transfer fluid may be water.
A third aspect of the invention provides a method of assembling a heat exchanger including defining a heat exchanger shell formed from a first metal material, the heat exchanger shell having a plurality of tube openings formed therein, and providing a plurality of heat exchanger tubes formed from a second metal material different from the first metal material. A non-metallic galvanic isolator is installed to one of an opening wall of the plurality of tube openings or the plurality of heat exchanger tubes. The plurality of heat exchanger tubes are installed into the plurality of tube openings, such that the galvanic isolator is located radially between the heat exchanger tube and the opening wall.
The galvanic isolator may be a polymeric sleeve.
The galvanic isolator may be a coating applied to one of the opening wall or the heat exchanger tube.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a schematic illustration of a chiller;
FIG. 2 is a cross-sectional view of a heat exchanger;
FIG. 3 is an illustration of an end sheet of heat exchanger shell;
FIG. 4 illustrates a galvanic isolator for a heat exchanger; and
FIG. 5 illustrates another galvanic isolator for a heat exchanger.

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Illustrated in FIG. 1 is an embodiment of a heating, ventilation and air conditioning (HVAC) system, for example a chiller 10. The chiller 10 includes a refrigerant circuit 12, having a flow of refrigerant 14 circulating therethrough. A compressor 16, a condenser 18, an expansion device 20, and an evaporator 22 arranged in series, with the flow of refrigerant 14 flowing through the components in sequence. The chiller 10 further includes a fluid circuit 24 operably connected to the refrigerant circuit 12 at the evaporator 22. The fluid circuit 24 has a flow of heat transfer fluid, such as a flow of water 26 circulating therethrough. The flow of water 26 circulates between the evaporator 22 and a heat exchanger, for example, a fan coil 28. The flow of water 26 is cooled at the evaporator 22 via an exchange of thermal energy with the flow of refrigerant 14. The cooled flow of water 26 is circulated to the fan coil 28 where it absorbs thermal energy from a flow or air 30 to provide cooling to a conditioned space 32. In some embodiments, a fan 34 aids the exchange of thermal energy at the fan coil 28. Additionally, in some embodiments, the condenser 18 is water cooled, and utilizes a condenser flow of water 60 to reject thermal energy from the flow of refrigerant 14 to condense the flow of refrigerant 14.
Referring now to FIG. 2, a cross-sectional view of a heat exchanger, such as the evaporator 22 or the condenser 18 of the chiller 10. The heat exchanger includes a heat exchanger shell 36 that contains a plurality of heat exchanger tubes 38 through which the flow of refrigerant 14 is directed through the heat exchanger. In some embodiments, the heat exchanger tubes 38 are formed from an aluminum material. The flow of water 26 enters the heat exchanger via a water inlet 40 and exits the heat exchanger after being either heated in the case of the condenser 18, or cooled in the case of the evaporator 22, via the flow of refrigerant 14 at a water outlet 42. In some embodiments, such as illustrated in FIG. 2, the flow of water 26 flows over the heat exchanger 38 via gravity. In other embodiments, the heat exchanger is flooded, in which the heat exchanger shell 36 is substantially filled with the flow of water 26.
Illustrated in FIG. 3 is an embodiment of an end sheet 44 of the heat exchanger shell 36. The end sheet 44 is formed from steel and includes a plurality of tube openings 46 through which the heat exchanger tubes 38 are installed. To prevent (or at least mitigate) a galvanic reaction between the end sheet 44 and the heat exchanger tubes 38 when the heat exchanger tubes 38 are exposed to the flow of water 26, a galvanic isolator 48 is disposed between the heat exchanger tube 38 and the end sheet 44 at the tube opening 46, as shown in FIG. 4. In a first embodiment, illustrated in FIG. 4, the galvanic isolator 48 is a very thin non-compressible sleeve or insert that is installed into the tube opening 46 prior to installation of the heat exchanger tube 38 into the tube opening 46. The heat exchanger tube 38 is then installed into the tube opening 46 such that the galvanic isolator 48 is radially between the heat exchanger tube 38 and an opening wall 50 of the tube opening 46. The fit between the evaporator tube 38 and the opening wall 50 is a close fit such that the tube opening 46 is sealed. The sleeve may be formed from a non-compressible polymeric or non-metallic material, and in some embodiments has a thickness in the range of 0.0005" to 0.001".
Utilizing a thin galvanic isolator 48 allows for use of existing spacing of heat exchanger tubes 38 in the heat exchanger, without having to compensate for the presence of the galvanic isolator 48, which may affect heat exchanger performance. While in the embodiment of FIG. 4 the galvanic isolator 48 is installed into the tube opening 46, in other embodiments the galvanic isolator 48 may be installed to the evaporator tube 38 prior to the heat exchanger tube 38 being into the tube opening 46.
In another embodiment, illustrated in FIG. 5, the galvanic isolator 48 is a coating applied directly to the opening wall 50 of the tube opening 46 prior to installation of the heat exchanger tube 38 into the tube opening 46. In some embodiments the coating material is, for example, polytetrafluoroethylene (PTFE) material applied by, for example, a spray or dip process. As with the sleeve, it is desired that the coating is thin, in the range of 0.0005" to 0.001" thickness, so that the spacing of the heat exchanger tubes 38 will not be affected by the use of the galvanic isolator 48. One skilled in the art will readily appreciate that the coating is not limited to PTFE material, and other thin coatings such as nano coatings or the like may be suitable. While in the embodiment of FIG. 5, the coating is applied to the opening wall 50 of the tube opening 46, one skilled in the art will appreciate that that coating may be applied instead to the heat exchanger tube 38 prior to installation of the heat exchanger tube 38 into the tube opening 46. Further, in some embodiments the coating may be applied to both the heat exchanger tube 38 and the opening wall 50 prior to installation of the heat exchanger tube 28 into the tube opening 46.
Use of the galvanic isolator 48 prevents (or at least mitigates) the galvanic pair from forming between the end sheet 44 and the heat exchanger tube 38, thus preventing (or at least mitigating) corrosion of the heat exchanger tube 38, which leads to an extension of the service life of the heat exchanger.
The term "about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the claims.
The following clauses set out features of the invention which may or may not be claimed but which may form the basis for future amendments and/or a divisional application:

1. A chiller system comprising:
- a refrigerant circuit having a flow of refrigerant circulating therethrough;
- a fluid circuit having a flow of heat transfer fluid circulating therethrough, the fluid circuit operably connected to the refrigerant circuit at a heat exchanger assembly to transfer thermal energy between the flow of refrigerant and the fluid circuit, the heat exchanger assembly comprising:
  a heat exchanger shell formed from a first metal material;
  - a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell, the plurality of heat exchanger tubes formed from a second metal material different from the first metal material; and
  - a galvanic isolator disposed at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding evaporator tube of the plurality of heat exchanger tubes, the galvanic isolator configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.
2. The chiller system of clause 1, wherein:
- the heat exchanger shell is formed from steel; and
- the plurality of heat exchanger tubes are formed from aluminum.
3. The chiller system of clause 1, wherein the galvanic isolator is formed from a non-metallic material.
4. The chiller system of clause 1, wherein the galvanic isolator is sleeve installed to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
5. The chiller system of clause 1, wherein the galvanic isolator is a coating applied to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
6. The chiller system of clause 5, wherein the coating is a polytetrafluoroethylene (PTFE) material.
7. The chiller system of clause 1, wherein the galvanic isolator has a thickness in a range of 0.0005 to 0.001 inches.
8. The chiller system of clause 1, wherein installation of the plurality of heat exchanger tubes into the plurality of tube openings seals the plurality of tube openings.
9. The chiller system of clause 1, wherein the heat transfer fluid is water.

Claims

A heat exchanger (22, 18) comprising:
a heat exchanger shell (36) formed from a first metal material;

a plurality of heat exchanger tubes (38) extending through a plurality of tube openings (46) in the heat exchanger shell (36), the plurality of heat exchanger tubes (38) being formed from a second metal material different from the first metal material; and

a galvanic isolator (48) disposed at each tube opening of the plurality of tube openings (46), radially between the tube opening and the corresponding heat exchanger tube of the plurality of heat exchanger tubes (38), the galvanic isolator (48) being configured to mitigate a galvanic reaction between the heat exchanger shell (36) and the plurality of heat exchanger tubes (38).
The heat exchanger (22, 18) of claim 1, wherein:
the heat exchanger shell (36) is formed from steel; and

the plurality of heat exchanger tubes (38) are formed from aluminum.
The heat exchanger (22, 18) of any preceding claim, wherein the galvanic isolator (48) is formed from a non-metallic material.
The heat exchanger (22, 18) of any preceding claim, wherein the galvanic isolator (48) is sleeve installed to one of the plurality of tube openings (46) or the plurality of heat exchanger tubes (38) prior to installation of the plurality of heat exchanger tubes (38) into the plurality of tube openings (46).
The heat exchanger (22, 18) of any of claims 1 to 3, wherein the galvanic isolator (48) is a coating applied to one of the plurality of tube openings (46) or the plurality of heat exchanger tubes (38) prior to installation of the plurality of heat exchanger tubes (38) into the plurality of tube openings (46).
The heat exchanger (22, 18) of claim 5, wherein the coating is a polytetrafluoroethylene (PTFE) material.
The heat exchanger (22, 18) of any preceding claim, wherein the galvanic isolator (48) has a thickness in a range of 0.0005 to 0.001 inches.
The heat exchanger (22, 18) of any preceding claim, wherein installation of the plurality of heat exchanger tubes (38) into the plurality of tube openings (46) seals the plurality of tube openings (46).
A chiller system (10) comprising:
a refrigerant circuit (12) having a flow of refrigerant (14) circulating therethrough;

a fluid circuit (24) having a flow of heat transfer fluid (26) circulating therethrough, the fluid circuit (24) being operably connected to the refrigerant circuit (12) at a heat exchanger (22, 18) to transfer thermal energy between the flow of refrigerant (14) and the fluid circuit (24), the heat exchanger (22, 18) being a heat exchanger (22, 18) according to any preceding claim.
The chiller system (10) of claim 9, wherein the heat transfer fluid is 5 water.
A method of assembling a heat exchanger (22, 18) comprising:
defining a heat exchanger shell (36) formed from a first metal material, the heat exchanger shell (36) having a plurality of tube openings (46) formed therein;

providing a plurality of heat exchanger tubes (38) formed from a second metal 10 material different from the first metal material;

installing a non-metallic galvanic isolator (48) to one of an opening wall (50) of the plurality of tube openings (46) or the plurality of heat exchanger tubes (38); and

installing the plurality of heat exchanger tubes (38) into the plurality of tube openings (46), such that the galvanic isolator (48) is disposed radially between the heat exchanger tube and the opening wall (50).
The method of claim 11, wherein the galvanic isolator (48) is a 5 polymeric sleeve.
The method of claim 11, wherein the galvanic isolator (48) is a coating applied to one of the opening wall (50) or the heat exchanger tube.