HEAT EXCHANGER WITH SACRIFICIAL TURBULATOR

Abstract

A heat exchanger is disclosed. The heat exchanger includes a hollow tube extending from a tube inlet to a tube outlet. The hollow tube includes a wall inner surface comprising a copper alloy or a first aluminum alloy. A first fluid flow path is disposed along the wall inner surface from the tube inlet to the tube outlet. A turbulator is disposed within the hollow tube along the first fluid flow path, and the turbulator comprises a second aluminum alloy that is less noble than the copper or first aluminum alloy. A second fluid flow path is disposed across an outer surface of the wall.

Claims

1. A heat exchanger comprising: a hollow tube extending from a tube inlet to a tube outlet, said hollow tube including a wall inner surface comprising a copper alloy or a first aluminum alloy; a first fluid flow path along the wall inner surface from the tube inlet to the tube outlet; a turbulator disposed within the hollow tube along the first fluid flow path, said turbulator comprising a second aluminum alloy that is less noble than the copper or first aluminum alloy; a second fluid flow path across an outer surface of the wall.

2. The heat exchanger of claim 1, further comprising a shell around the second flow path and the hollow tube, the shell including an inlet and an outlet in operative fluid communication with the second fluid flow path.

3. The heat exchanger of claim 1, wherein the wall inner surface comprises the copper alloy.

4. The heat exchanger of claim 1, wherein the wall inner surface comprises the first aluminum alloy.

5. The heat exchanger of claim 1, wherein the second aluminum alloy includes zinc or magnesium.

6. The heat exchanger of claim 1, wherein the second aluminum alloy includes an alloying element selected from tin, indium, gallium, or combinations thereof.

7. The heat exchanger of claim 1, wherein the hollow tube wall is arranged as a hollow cylinder around the first fluid flow path.

8. The heat exchanger of claim 1, further comprising a plurality of fins comprising a third aluminum alloy extending outwardly from an outer surface of the wall.

9. A heat transfer system comprising a heat transfer fluid circulation loop in operative thermal communication with a heat source and a heat sink, wherein the heat exchanger of claim 1 is disposed as a thermal transfer link between the heat transfer fluid and the heat sink or heat source.

10. The heat transfer system of claim 9, wherein the heat transfer fluid circulation loop is in operative fluid communication with the first fluid flow path.

11. The heat transfer system of claim 9, wherein the heat transfer fluid comprises water.

12. The heat transfer system of claim 9, wherein the heat transfer fluid comprises alcohols, glycols, chlorides, formats/acetates, or ammonia.

13. The heat transfer system of claim 12, wherein the alcohol comprises ethylene glycol or propylene glycol.

14. A heat transfer system comprising: a first heat transfer fluid circulation loop in thermal communication with a heat sink, comprising a refrigerant in operative fluid communication with a heat absorption side of a cross-over heat exchanger; a second heat transfer fluid circulation loop in thermal communication with a heat source, comprising an aqueous heat transfer liquid in operative fluid communication through a hollow tube including a wall inner surface that comprises a copper alloy or a first aluminum alloy on a heat rejection side of the cross-over heat exchanger, said hollow tube further including a turbulator disposed within the hollow tube comprising a second aluminum alloy that is less noble than the copper or first aluminum alloy.

15. The heat transfer system of claim 14, wherein the first heat transfer fluid circulation loop includes a compressor, a heat rejection heat exchanger in thermal communication with the heat sink, an expansion device, and the heat absorption side of the cross-over heat exchanger, connected together in order by conduit.

16. The heat transfer system of claim 14, wherein the system is configured to reduce the aqueous heat transfer liquid below 0° C.

17. The heat transfer system of claim 14, wherein the aqueous heat transfer liquid comprises alcohols, glycols, chlorides, formats/acetates, or ammonia.

18. The heat transfer system of claim 14, wherein the wall inner surface comprises the copper alloy.

19. The heat transfer system of claim 14, wherein the second aluminum alloy includes zinc or magnesium.

20. The heat transfer system of claim 14, wherein the second aluminum alloy includes an alloying element selected from tin, indium, gallium, or combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0026] FIG. 1 shows a perspective view of portions of a tube in shell heat exchanger;

[0027] FIGS. 2A, 2B, and 2C show views of a heat exchanger tube and turbulator;

[0028] FIG. 3 shows a perspective view of portions of a round tube plate fin heat exchanger; and

[0029] FIG. 4 schematically shows a heat transfer system.

DETAILED DESCRIPTION

[0030] 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.

[0031] Referring now to FIG. 1, an example embodiment of a heat exchanger 36 with tubes and turbulator is such as can be used in a dual circuit refrigerant cycle using two heat transfer fluid passes. The heat exchanger is of the tube and shell variety, but other configurations can be used as discussed in greater detail below. As shown in FIG. 1, heat transfer fluid flows through a plurality of copper tubes 38 and refrigerant surrounds the tubes 38 positioned within a shell 40, exchanging heat. A center partition plate 42 perpendicular to the axis of the shell 40 separates refrigerant circuit A and refrigerant circuit B. The partition plate 42 includes a plurality of apertures 44 to receive the plurality of tubes 38. A pass partition plate 82 perpendicular to the center partition plate 42 separates the heat transfer fluid passes Y1 and Y2.

[0032] Heat transfer fluid from a first refrigerant box 80 enters pass Y1. Inlet heat transfer fluid enters the refrigerant circuit A through the plurality of tubes 38 and exchanges heat with refrigerant circuit A. Refrigerant of refrigerant circuit A enters the shell 40 through inlet 46 and exits the shell 40 through outlet 48. Although the inlet 46 is illustrated at the bottom surface, the inlet 46 can be positioned at other locations in other type evaporators. Heat transfer fluid then enters and exchanges heat with the second refrigerant circuit B. Refrigerant of refrigerant circuit B enters the shell 40 through inlet 50 and exits the shell 40 through outlet 52. The heat transfer fluid from Y1 then enters a heat transfer fluid box 54. The heat transfer fluid then enters pass Y2 through tubes 48 and passes again through refrigerant circuits A and B. In the prior art design, the tubes 38 are of substantially the same diameter. Additionally, in some embodiments both refrigerant circuits A and B include an equal number of tubes.

[0033] As mentioned above, in some embodiments the tubes 38 are made of copper or a copper alloy, or of a first aluminum alloy. Alternatively, the tubes 38 can be clad with or have surface portions thereof covered with the copper or first aluminum alloy. Copper alloys, if present, for the tubes 38 can be selected from any of a number of known alloys, including but not limited to C120 or C122 (copper alloy numbers according to the Unified Numbering System for Copper+Copper Alloys, administered by the American National Standards Institute and the American Society for Testing and Materials. The first aluminum alloy, if present, can be an aluminum alloy based material and, in some embodiments, may be made from aluminum alloys selected from 1000 series, 3000 series, 5000 series, or 6000 series aluminum alloys (as used herein, all alloy numbers and alloy series numbers and individual alloy numbers are as specified and published by The Aluminum Association). Examples of aluminum alloys that can be used as core materials include but are not limited to AA1100, AA1145, AA3003, AA3102, AA5052, AA7072, AA8005, or AA8011.

[0034] As mentioned above, the tubes 38 include turbulators therein. In some embodiments, the turbulator can take the form of a helical structure (e.g., a double helix as shown in FIGS. 2A-2C or a single helix) that extends along the length of the tube (i.e., the tube axis), which can be formed by twisting a flat metal tape-like sheet into the desired shape. An example embodiment of a tube 38 with a turbulator therein is shown in FIGS. 2A-2C. As shown in FIG. 2A, a turbulator 39 extends lengthwise along the inside of the tube 38. A helical turbulator such as the turbulator 39 can be characterized by a period length H (FIG. 2A) and a thickness δ. The turbulator can be formed by securing one or more flat metal tape-like sheets to an end tab 41 (FIG. 2C), and twisting the tape under tension relative to the end tab 41, and then inserting the twisted turbulator 41 structure into the tube 38.

[0035] The turbulators can be formed from (or be clad with or have surface portions thereof covered with) a second aluminum alloy. In embodiments where the second aluminum alloy is used as a cladding or surface covering, it can be deposited using various techniques including but not limited to thermal spray (e.g., cold spray), brazing, roll cladding, electroplating, etc. The second aluminum alloy can be an aluminum alloy based material and, in some embodiments, may be made from aluminum alloys selected from 1000 series, 3000 series, 5000 series, or 6000 series aluminum alloys, including AA1100, AA1145, AA3003, AA3102, AA5052, AA7072, AA8005, or AA8011. The second aluminum alloy is less noble than the copper alloy or is less noble first aluminum alloy, depending on which metal the tube 38 is made of. By “less noble”, it is meant that the second aluminum alloy is galvanically less noble, i.e., that the second alloy has a lower galvanic potential or a lower electrode potentials than the first aluminum alloy such that the second aluminum alloy would be anodic with respect to the first aluminum alloy in a galvanic cell. This allows the second aluminum alloy to provide sacrificial corrosion protection to the first aluminum alloy. In some embodiments, the difference in galvanic potential between the second aluminum alloy, and the nearest potential of the first and second aluminum alloys is in a range having a lower end of >0 V, 50 mV, or 150 mV, and an upper end of 400 mV, 650 mV, or 900 mV. These range endpoints can be independently combined to form a number of ranges, and each possible combination is hereby expressly disclosed. In some embodiments, the second aluminum alloy can be provided with reduced nobility by incorporating alloying elements such as zinc or magnesium. In some embodiments where zinc is present, the zinc can be present in the second aluminum alloy at a level in a range with a lower end of 0.5 wt. %, 2.0 wt. %, 2.5 wt. %, or 4.0 wt. %, and an upper end of 4.5 wt. %, 6.0 wt. %, 7.0 wt. %, or 10.0 wt. %. These range endpoints can be independently combined to form a number of ranges, and each possible combination is hereby expressly disclosed. In some embodiments where magnesium is present, the magnesium can be present in the second aluminum alloy at a level in a range with a lower end of 0.5 wt. %, 1.0 wt. %, or 2.2 wt. %, and an upper end of 1.5 wt. %, 2.8 wt. %, or 4.9 wt. %. These range endpoints can be independently combined to produce different ranges, each of which is hereby explicitly disclosed. The second aluminum alloy also includes one or more alloying elements selected from tin, indium, or gallium. In some embodiments, the selected alloying element(s) can be present in the second aluminum alloy at a level in a range with a lower end of 0.010 wt. %, 0.016 wt. %, or 0.020 wt. %, and an upper end of 0.020 wt. %, 0.035 wt. %, 0.050 wt. %, or 0.100 wt. %. These range endpoints can be independently combined to produce different possible ranges, each of which is hereby explicitly disclosed (i.e., 0.010-0.020 wt. %, 0.010-0.035 wt. %, 0.010-0.050 wt. %, 0.010-0.100 wt. %, 0.016-0.020 wt. %, 0.016-0.035 wt. %, 0.016-0.050 wt. %, 0.016-0.100 wt. %, 0.020-0.020 wt. %, 0.020-0.035 wt. %, 0.020-0.050 wt. %, 0.020-0.100 wt. %). The second aluminum alloy can also include one or more other alloying elements for aluminum alloys. The second alloy can also include one or more other alloying elements for aluminum alloys. In some embodiments, the amount of any individual other alloying element can range from 0-1.5 wt. %. In some embodiments, the total content of any such other alloying elements can range from 0-2.5 wt. %. Examples of such other alloying elements include Si, Fe, Mn, Cu, Ti, or Cr. In some embodiments, the second aluminum alloy can have a composition consisting of: 4.0-6.0 wt. % zinc or magnesium, 0.001-0.1 wt. % of one or more alloying elements selected from tin, indium, gallium, or combinations thereof, 0-2.5 wt. % other alloying elements, and the balance aluminum.

[0036] As mentioned above, other types of heat exchangers (e.g., round tube plate fin, or microchannel heat exchangers) can include turbulators according to the present disclosure. An example embodiment of a round tube plate fin heat exchanger is schematically shown in FIG. 3. As shown in FIG. 3, a heat exchanger 300 can include one or more flow circuits for carrying refrigerant. For the purposes of explanation, a portion of the heat exchanger 300 is shown with a single flow circuit refrigerant tube 320 in FIG. 3 consisting of an inlet line 330 and an outlet line 340. The inlet line 330 is connected to the outlet line 340 at one end of the heat exchanger 300 through a 90 degree tube bend 350. It should be evident, however, that more circuits may be added to the unit depending upon the demands of the system. For example, although tube bend 350 is shown as a separate component connecting two straight tube section, the tube 320 can also be formed as a single tube piece with a hairpin section therein for the tube bend 350, and multiple units of such hairpin tubes can be connected with u-shaped connectors at the open ends to form a continuous longer flow path in a ‘back-and-forth’ configuration. Alternatively, the tubes can be configured as separate tube segments in parallel between headers on each end (not shown). The heat exchanger 300 can further include a series of fins 360 comprising radially disposed plate-like elements spaced along the length of the flow circuit, typically connected to the tube(s) 320 with an interference fit. The fins 360 are provided between a pair of end plates or tube sheets 370 and 380 and are supported by the lines 330, 340 in order to define a gas flow passage through which conditioned air passes over the refrigerant tube 320 and between the spaced fins 360. Fins 360 can also include heat transfer enhancement elements such as louvers. In some embodiments, fins 360 can be formed from a third aluminum alloy, which can include aluminum alloy materials such as, for example, materials selected from the 1000 series, 3000 series, 6000 series, 7000 series, or 8000 series aluminum alloys. The embodiments described herein utilize an aluminum alloy for the fins of a tube-fin heat exchanger having an aluminum alloy tube. In some embodiments, the fins can be made from or can be overlaid by an aluminum alloy that is galvanically less noble than the tube alloy.

[0037] The heat exchanger embodiments disclosed herein can be used in a heat transfer system. Referring now to the FIG. 4, an exemplary heat transfer system for use as a chiller is schematically shown in block diagram form. As shown in FIG. 4, a first refrigerant circulation loop includes a compressor 410, which pressurizes a refrigerant (e.g., a fluorocarbon) in its gaseous state, which both heats the fluid and provides pressure to circulate it throughout the system. The hot pressurized gaseous refrigerant exiting from the compressor 410 flows through conduit 415 to heat rejection heat exchanger 420, which functions as a heat exchanger to transfer heat from the refrigerant to the surrounding environment, resulting in condensation of the hot gaseous refrigerant to a pressurized moderate temperature liquid. The liquid refrigerant exiting from the heat rejection heat exchanger 420 (e.g., a condenser) flows through conduit 425 to expansion valve 430, where the pressure is reduced. The reduced pressure liquid refrigerant exiting the expansion valve 430 flows through conduit 435 to a heat absorption side (e.g., evaporator side) of a cross-over heat exchanger 440, which functions as a heat exchanger to absorb heat from a heat transfer fluid, thereby cooling or chilling the heat transfer fluid) on a heat rejection side of the cross-over heat exchanger 440, thereby cooling or chilling the heat transfer fluid, and causing the refrigerant to boil. The now gaseous refrigerant exiting the cross-over heat exchanger 440 flows through conduit 445 to the compressor 410, thus completing the refrigerant loop. The heat transfer system has the effect of transferring heat from the heat transfer fluid on the heat rejection side of the cross-over heat exchanger 440 to the heat absorption side of the heat rejection heat exchanger 420. The thermodynamic properties of the refrigerant allow it to reach a high enough temperature when compressed so that it is greater than the temperature on the heat absorption side of the heat exchanger 420, allowing for heat transfer. The thermodynamic properties of the refrigerant must also have a boiling point at its post-expansion pressure that provides a temperature differential to cool the heat transfer fluid on the heat rejection side of the cross-over heat exchanger 440 and provide heat at a temperature to vaporize the liquid refrigerant. The heat exchanger and turbulator embodiments described herein can be used for either of the heat exchangers 420 or 440. In some embodiments, the heat exchanger and turbulator embodiments described herein are used for the cross-over heat exchangers 440, where sacrificial corrosion protection provided by the less noble turbulator can protect against conductive and corrosive properties of brines used as low temperature heat transfer fluids used in some chiller systems.

[0038] The heat transfer system shown in FIG. 4 can be used as an air conditioning system, in which the exterior of heat rejection heat exchanger 20 is contacted with air in the surrounding outside environment and the heat absorption heat exchanger 40 is contacted with air in an interior environment to be conditioned. Additionally, as is known in the art, the system can also be operated in heat pump mode using a standard multiport switching valve to reverse refrigerant flow direction and the function of the condensers and evaporators, i.e. the condenser in a cooling mode being evaporator in a heat pump mode and the evaporator in a cooling mode being the condenser in a heat pump mode. Additionally, while the heat transfer system shown in FIG. 4 has evaporation and condensation stages for highly efficient heat transfer, other types of refrigerant loops are contemplated as well, such as fluid loops that do not involve a phase change, for example, multi-loop systems such as commercial refrigeration or air conditioning systems where a non-phase change loop thermally connects one of the heat exchangers in an evaporation/condensation loop like FIG. 4 to other heat transfer fluid loops in thermal communication with a surrounding outside environment or to an interior environment to be conditioned.

[0039] With continued reference to FIG. 4, the heat transfer system includes a heat transfer fluid circulation loop 450 that utilizes one or more pumps (not shown) to circulate a heat transfer fluid between the heat absorption side of the cross-over heat exchanger 440 and a heat source 455. In some embodiments, the heat transfer fluid in the loop 450 is aqueous, either water or a solution comprising water. In some embodiments, the system can be configured to cool the heat transfer fluid in the loop 450 to a temperature at or below 0° C., for example to provide a freezing temperature to a heat source 455 such as a frozen storage environment or an ice surface such as an ice rink. For such low temperature applications, an aqueous heat transfer fluid can include components to provide the aqueous fluid with a freezing point below 0° C. or below a minimum operating temperature of the cross-over heat exchanger 440. Such low-temperature aqueous heat transfer fluids are sometimes referred to as “brines”, and can include water-soluble organic solvents such as alcohols, including but not limited to glycols (e.g., ethylene glycol, propylene glycol), chlorides (e.g., calcium chloride, sodium chloride, potassium chloride, lithium chloride), alcohols (methanol, ethanol and water), potassium (potassium acetate, potassium formate), and ammonia. Such components can increase electrical conductivity of the aqueous heat transfer fluid, which can promote susceptibility to galvanic corrosion that is addressed by sacrificial corrosion of the turbulators to provide a technical effect of protecting the tube walls. In some embodiments, another heat transfer fluid loop 460 can transfer heat from the heat absorption side of the heat exchanger 420 by circulating (pumps not shown) a heat transfer fluid to a heat sink 465 (e.g., a cooling tower in fluid and thermal communication with an outside environment (i.e., outside air)). In such an example embodiment, the heat transfer fluid 460 can include an aqueous heat transfer fluid, which can include optional additives such as corrosion inhibitors, pH buffers, anti-scale agents, biocides, etc., but which does not require freezing point suppression like the heat transfer fluid in the loop 450.

[0040] To the extent used herein, 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. For example, “about” can include a range of ±8% or 5%, or 2% of a given value.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. 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.

[0042] While the present disclosure 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 disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.