US20240035753A1

US20240035753A1 - Condenser tube with non-uniform surface enhancements

Info

Publication number: US20240035753A1
Application number: US18/228,815
Authority: US
Inventors: Kar-Wing Lau; Joseph Capes
Original assignee: Liquidstack Holding BV
Current assignee: Liquidstack Holding BV
Priority date: 2022-08-01
Filing date: 2023-08-01
Publication date: 2024-02-01

Abstract

Condenser tubes with non-uniform surface enhancements are described herein. In one example, the condenser tube may include a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface. The condenser tube may have a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a coolant. The exterior surface may have a top portion and a bottom portion. The top portion may have a substantially smooth region. The bottom portion may have a plurality of surface enhancements extending longitudinally from the first end to the second end. In one application, the condenser tubes with non-uniform surface enhancements may be deployed in condensers for two-phase immersion cooling systems. Other examples may be claimed or described.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Patent Application No. 63/394,116, filed on Aug. 1, 2022, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to condenser tubes with non-uniform surface enhancements. The condenser tubes may be used in condensers for two-phase immersion cooling systems.

BACKGROUND

Data centers house information technology (IT) equipment for the purposes of storing, processing, and disseminating data and applications. IT equipment may include electronic devices, such as servers, storage systems, power distribution units, routers, switches, and firewalls.
Data centers are energy-intensive facilities. It is not uncommon for a data center to consume over fifty times more energy per square foot than a typical commercial office building. A significant portion of the energy consumed in data centers is due to operating and cooling the IT equipment. A proven way to reduce power consumption is through deployment of liquid cooling systems. Liquid cooling systems capture waste heat from IT equipment and reject the heat outside of the data center. One form of liquid cooling is immersion cooling. In an immersion cooling system, an electronic device is immersed in dielectric fluid. Waste heat from the electronic device is transferred to the dielectric fluid and then rejected outside of the data center through an outdoor heat rejection system.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.
In one aspect, a condenser tube may include a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface. The condenser tube may have a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a coolant. The exterior surface may have a top portion and a bottom portion. The top portion may have a substantially smooth region, and the bottom portion may have a plurality of surface enhancements extending longitudinally from the first end to the second end. The plurality of surface enhancements may extend radially from the exterior surface. The plurality of surface enhancements may include a plurality of fins. The plurality of surface enhancements each extend either horizontally or downward from the exterior surface. The plurality of surface enhancements may each extend downward from the exterior surface. The plurality of surface enhancements each extend horizontally from the exterior surface. The plurality of surface enhancements may include a plurality of fins extending from the first end to the second end. The plurality of surface enhancements may extend in a parallel configuration, and a first surface enhancement may be recessed relative to a second surface enhancement that is above and adjacent to the first surface enhancement. The condenser tube may be part of a condenser, and the condenser may be part of a two-phase immersion cooling system. The surface enhancements may be located below a horizontal midplane of the condenser tube. Less than half of the top portion may include surface enhancements. The surface enhancements may include a plurality of pointed fins that taper in a direction from a base to a tip of each fin. The interior surface may be substantially smooth. Each fin may have a maximum fin length greater than a minimum distance between adjacent fins.
In another aspect, a condenser tube may include a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface, and a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a coolant. Between 25% and 50% of the exterior surface may be substantially smooth, and between 50% and 75% of the exterior surface may include surface enhancements. The interior surface may be substantially smooth. The surface enhancements may include a plurality of fins that extend longitudinally from the first end to the second end. The plurality of fins may extend radially and downward.
In another aspect, a condenser may include an inlet manifold with an inlet, an outlet manifold with an outlet, and a plurality of condenser tubes fluidly connecting the inlet manifold to the outlet manifold. At least one of the condenser tubes may include a tube having a first end, a second end opposite the first end, an interior surface, an exterior surface, a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a heat transfer fluid. The interior surface may be substantially smooth. The exterior surface may have a top portion and a bottom portion. The top portion may have a region that is substantially smooth, and the bottom portion may include a plurality of surface enhancements extending longitudinally from the first end to the second end.

BRIEF DESCRIPTION OF DRAWINGS

The drawings are not necessarily to scale, and emphasis may instead be placed upon illustrating principles of the invention. Like numerals may identify like elements throughout the views and embodiments. In the detailed description, various embodiments are described with reference to the following drawings, in which:

FIG. 1 shows an example of a prior art condenser with four condenser tubes.

FIG. 2 shows a cross-sectional view of the condenser tubes of FIG. 1 while operating in a two-phase immersion cooling system.

FIG. 3 shows an example of a prior art condenser with eight condenser tubes.

FIG. 4 shows a cross-sectional view of condenser tubes with surface enhancements while operating in a two-phase immersion cooling system.

FIG. 5 shows a condenser operating in a two-phase immersion cooling system, where the condenser has condenser tubes with non-uniform surface enhancements.

FIG. 6 shows a cross-sectional view of the condenser tubes of FIG. 5 while operating in a two-phase immersion cooling system.

FIG. 7A shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend radially.

FIG. 7B shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that each extend either horizontally or downward.

FIG. 7C shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that each extend downward.

FIG. 8A shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend radially.

FIG. 8B shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that each extend either horizontally or downward.

FIG. 8C shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that each extend downward.

FIG. 9A shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend radially and taper in a direction from a base to a tip of each surface enhancement.

FIG. 9B shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend horizontally or downward.

FIG. 9C shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend downward.

FIG. 10A shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend horizontally in a parallel configuration.

FIG. 10B shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend horizontally in a parallel configuration.

FIG. 100 shows a cross-sectional view of a condenser tube with non-uniform surface enhancements that extend downward.

FIG. 11 shows a first prior art example of a two-phase immersion cooling system with one condenser.

FIG. 12 shows a second prior art example of a two-phase immersion cooling system with a primary condenser and a freeboard condenser.

FIG. 13 shows an example of a two-phase immersion cooling system with a primary condenser and a freeboard condenser, each having condenser tubes with non-uniform surface enhancements.

DETAILED DESCRIPTION

Condenser tubes with non-uniform surface enhancements are described herein. In one example, the condenser tubes can be used to improve performance of condensers for use in two-phase immersion cooling systems. Prior art examples of two-phase immersion cooling systems are shown in FIGS. 11 and 12 . The prior art systems can be improved by incorporating the condenser tubes described herein, as shown in FIG. 13 , to provide improved performance and efficiency.
FIG. 11 shows a first prior art example of a two-phase immersion cooling system 1100. The system 1100 includes an immersion tank 201 partially filled with dielectric fluid 620 in liquid phase, providing a bath of dielectric fluid. The system includes a condenser 235 mounted in a headspace of the tank 201. An electronic device 800 is immersed in the bath of dielectric fluid. The electronic device 800 may be a server with one or more microprocessors 801. The tank 201 is enclosed by a lid 225. When powered on, the electronic device 800 produces heat. The heat is transferred to the dielectric fluid 620, which causes a portion of the fluid to boil and dielectric vapor 615 to form. The vapor 615 rises through the bath of dielectric liquid 620 and enters the headspace of the tank 201. Coolant (e.g., a water-glycol mixture) is circulated through the condenser coil to maintain the condenser at a temperature below a dew point of the dielectric vapor. When the vapor 615 contacts the condenser 235, it condenses to liquid and passively drains back to the liquid bath, thereby completing a cycle 1101 of evaporation, condensation, precipitation, and collection. During operation, boiling of the relatively dense dielectric fluid 620 produces a relatively less dense vapor 615, which expands and enters the headspace occupied by non-condensable gases (e.g., air). As more vapor 615 is produced and enters the headspace, the tank pressure increases, since dielectric fluid 620 occupies more volume as a vapor than a liquid. To prevent the tank pressure from reaching an unsafe level, a pressure relief valve 460 is provided in the tank 201 and opened when the pressure exceeds a predetermined threshold. Upon actuation of the pressure relief valve 460, a fraction of the dielectric vapor 615 is released from the tank 201 and lost to the environment. Over time, periodic valve actuation and fluid loss depletes the fluid 620, necessitating replenishment. To reduce costly fluid loss and to conserve space to allow for more compact or mobile systems, it is desirable to improve the performance of the condenser and condenser tubes, in accordance with the examples shown and described herein.
FIG. 12 shows a second prior art example of a two-phase immersion cooling system 1200 with two condensers. The system 1200 includes an immersion tank 201 partially filled with dielectric fluid 620 in liquid phase. An electronic device 800 is immersed in the dielectric fluid 620. The electronic device 800 may be a server including one or more microprocessors 801. The immersion tank 201 is enclosed by a lid 225. The system 1200 may include a primary condenser 235 and a freeboard condenser 250 mounted within the immersion tank 201. The primary condenser 235 may be located above a liquid line 605 in the headspace of the tank 201. The freeboard condenser 250 may be located a distance above the primary condenser 235 in the headspace 206. In one example, the primary condenser 235 may operate at a temperature of about 5° C. to 15° C. The freeboard condenser 250 may operate at a lower temperature of about −28° C. to −2° C. The system 1200 has a high freeboard ratio, where freeboard ratio is defined as a distance measured from the top of the primary condenser 235 to an underside of the lid 225 divided by an internal width of the immersion tank 201.
During steady-state operation of the system 1200, vapor 615 is generated as heat from the electronic device 800 vaporizes dielectric fluid 620 in the tank 201. The vapor 615 is heavier than air 705, so a first zone 1205 containing saturated vapor 615 may settle above the liquid line 605. A second zone 1210 containing mixed vapor 615 and air 705 may form above the saturated vapor 615. A third zone 1215 containing mostly air 705 may form above the mixture of vapor 615 and air 705. The saturated vapor zone 1205 may be located between the liquid line 605 and the primary condenser 235. The mixed vapor and air zone 1210 may be located between the primary condenser 235 and the freeboard condenser 250. The third zone 1215 containing mostly air 705 may be located between the freeboard condenser 250 and the lid 225. The primary condenser 235 may be appropriately sized to condense most of the vapor 615 produced during steady-state operation. The freeboard condenser 250 may condense vapor 615 that rises above the primary condenser 235 and enters the second zone 1210. During steady-state operation, an equilibrium of vapor production and condensing may exist.
During periods of high microprocessor 801 utilization, more electric power is consumed by the device 800 and more heat is produced, resulting in a higher rate of vapor production. As the amount of vapor 615 in the headspace 206 increases, the depth of the saturated vapor zone 1205 grows. The freeboard condenser 250, which is maintained at a lower temperature than the primary condenser 235, may effectively condense vapor 615 that reaches it.
FIG. 3 shows an example of a prior art condenser 100 for use in an immersion cooling system, such as the systems shown in FIGS. 11 and 12 (1100, 1200). The condenser 100 may include an inlet manifold 105, an outlet manifold 110, and one or more condenser tubes 115 fluidly connecting the inlet manifold 105 to the outlet manifold 110. The condenser tubes 115 may provide parallel fluid pathways from the inlet manifold 105 to the outlet manifold 110. The condenser 100 may receive a coolant (e.g., a water-glycol mixture from a facility cooling loop) through an inlet 101 formed in the inlet manifold 105. The coolant may flow into the inlet manifold, through the condenser tube, into the outlet manifold, and exit the condenser through the outlet. The coolant may be provided to the condenser 100 at a temperature that is below a boiling point of the dielectric vapor 113 in the immersion cooling system. As the coolant flows through the condenser, it may receive heat from the dielectric vapor 113, thereby causing the vapor to condense and form a condensate 132 that returns to the fluid bath 111 by way of gravity (e.g., by dripping from the condenser 104 back into the fluid bath), as shown in the cross-sectional view of the condenser tubes 115 in FIG. 2 .
To improve the efficiency of the immersion cooling system, it is desirable to improve the performance of the condenser 100. The performance of the condenser 100 (i.e., its ability to convert dielectric vapor to dielectric liquid) may be influenced, in part, by its effective surface area. Increasing the surface area may improve performance. To increase the effective surface area of the condenser, more condenser tubes 115 can be added to the condenser 300, as shown in the prior art example of FIG. 3 . However, this alteration increases size, cost, weight, and complexity, since more material and additional welds are required to manufacture the condenser. It is preferable to find a way to improve performance of the condenser 100 without adding more condenser tubes 115 or increasing tube length.
Increasing the surface area of the condenser 400 can also be accomplished by adding surface enhancements 120 (e.g., radial fins) to the condenser tubes 115, as shown in FIG. 4 . However, during operation, dielectric fluid 620 that condenses from vapor may pool between the surface enhancements 120 and fail to drain back into the fluid bath. If dielectric liquid is covering all or a portion of the surface area of the condenser 104, the available surface area is reduced and, in turn, the performance of the condenser is reduced. Consequently, there is a need to prevent the condensed dielectric liquid 620 from pooling or otherwise collecting on the condenser tube 115 and reducing its available surface area and performance.
As shown in FIG. 12 , air 705 may be present in the headspace 206 of the immersion cooling system 1200. The air may contain water vapor. The mixture of air and water vapor may behave as a non-condensable gas 125 at the operating temperatures and pressures within the headspace. The non-condensable gas 125 may become trapped between the surface enhancements 10 of the condenser tube 400, as shown in FIG. 4 , and block dielectric vapor from reaching the condenser tube, thereby decreasing the condensation rate and reducing efficiency of the condenser. There is a need to improve the surface enhancements of the condenser tube to avoid or reduce trapping of the non-condensable gas, and thereby increase the rate of condensation of dielectric vapor and the efficiency of the condenser.
FIG. 5 shows a condenser 500 with non-uniform surface enhancements 520 on the condenser tubes 515. FIG. 6 shows a cross-sectional view of the condenser tubes 515. The condenser tubes 515 may include surface enhancements 520 along a bottom portion of the condenser tube. The condenser tubes 515 may be substantially free of surface enhancements along a top portion to avoid trapping and collecting non-condensable gas 125 and/or condensed dielectric fluid 620 in that region. The surface enhancement may be fins 520 that extend radially from the condenser tube 515. The surface enhancements 520 may be oriented so that gravity aids in shedding condensate 620 from the condenser tube 515. In other words, the surface enhancements 520 may be self-draining.
FIGS. 7A-C show cross-sectional views of three examples of condenser tubes 515 with non-uniform surface enhancements 520. The example in FIG. 7A is the same as the condenser tubes shown in FIG. 6 . The condenser tube 515 may have an interior surface 545, an exterior surface 540, and a tube wall 555 therebetween. The condenser tube 515 may have a longitudinal bore 550 defined by the interior surface 545 and extending from a first end to a second end of the condenser tube. The condenser tube 515 may be configured to transport a coolant, such as a water-glycol mixture. The interior surface 545 may be substantially smooth. The exterior surface 540 may include a top portion 530 and a bottom portion 535. The top portion 530 is located above a horizontal midplane 525 of the condenser tube, and the bottom portion is located below the horizontal midplane 525, as shown in FIG. 7A. The top portion 530 may have a region that is substantially smooth, and the bottom portion 535 may have surface enhancements 520 extending longitudinally from the first end to the second end. FIG. 7B shows a condenser tube with surface enhancements that extend radially and either extend horizontally or downward. FIG. 7C shows a condenser tube with surface enhancements that extend downward only. The upper portion of the condenser tubes in FIGS. 7A-C may be substantially smooth and free of surface enhancements.
FIGS. 8A-C show cross-sectional views of three examples of condenser tubes 515 with non-uniform surface enhancements 520. FIG. 8A shows a condenser tube with surface enhancements that extend radially and extend horizontally, downward, or upward. FIG. 8B shows a condenser tube with surface enhancements that extend radially and extend horizontally or downward. FIG. 8C shows a condenser tube with surface enhancements that downward. The upper portion of the condenser tubes in FIGS. 8A-C may be substantially smooth and free of surface enhancements. The surface enhancements may be fins that each have a maximum length (I) greater than a minimum distance (d) between adjacent fins, as shown in FIG. 8A.
In one example, more than 50% (e.g., about 75%) of the exterior surface 540 of the condenser tube 515 may have surface enhancements and less than 50% (e.g., about 25%) of the exterior surface area may be substantially smooth, as shown in FIG. 7A. In another example, about 50% of the exterior surface 540 of the condenser tube 515 may have surface enhancements and about 50% of the exterior surface area may be substantially smooth, as shown in FIG. 7B. In another example, less than 50% (e.g., about 45%) of the exterior surface 540 of the condenser tube 515 may have surface enhancements and more than 50% (e.g., about 55%) of the exterior surface area may be substantially smooth, as shown in FIG. 7C. In another example, between about 25% and about 50% of the exterior surface may be substantially smooth, and between about 50% and about 75% of the exterior surface comprises surface enhancements. As used herein, the term “about” is defined as meaning plus or minus five percent.
FIGS. 9A-C show cross-sectional views of three examples of condenser tubes 515 with non-uniform surface enhancements 520. FIG. 9A shows a condenser tube 515 with surface enhancements 520 that extend radially. FIG. 9B shows a condenser tube 515 with surface enhancements 520 that extend radially and extend horizontally or downward. FIG. 9C shows a condenser tube 515 with surface enhancements 520 that extend downward. The upper portion of the condenser tubes in FIGS. 9A-C may be substantially smooth and free of surface enhancements. The surface enhancements 520 may be pointed fins that taper in a direction from a base to a tip of each fin.
FIGS. 10A-C show cross-sectional views of three examples of condenser tubes 515 with non-uniform surface enhancements 520. FIG. 10A shows a condenser tube with surface enhancements that extend horizontally. FIG. 10B shows a condenser tube with surface enhancements that extend horizontally in a parallel configuration where each surface enhancement is recessed relative to the surface enhancement that is above and adjacent. FIG. 10C shows a condenser tube with surface enhancements 520 that extend downward in a parallel configuration and where each surface enhancement is recessed relative to the surface enhancement that is above and adjacent. The upper portion of the condenser tubes in FIGS. 10A-C may be substantially smooth and free of surface enhancements.
FIG. 13 shows a two-phase immersion cooling system 1300 that is similar to the system 1200 shown in FIG. 12 but includes condensers having condenser tubes 515 with non-uniform surface enhancements 520. The non-uniform surface enhancements 520 may be any of the surface enhancements shown and described herein (see, e.g., FIGS. 7A-100 ). The lower condenser may be a primary condenser, and the upper condenser may be a freeboard condenser.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments, therefore, are to be considered in all respects illustrative rather than limiting the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

What is claimed is:

1. A condenser tube comprising:

a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface;

a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a coolant;

wherein the exterior surface has a top portion and a bottom portion, and

wherein the top portion comprises a substantially smooth region, and the bottom portion comprises a plurality of surface enhancements extending longitudinally from the first end to the second end.

2. The condenser tube of claim 1, wherein the plurality of surface enhancements extend radially from the exterior surface.

3. The condenser tube of claim 2, wherein the plurality of surface enhancements comprise a plurality of fins.

4. The condenser tube of claim 2, wherein the plurality of surface enhancements each extend either horizontally or downward from the exterior surface.

5. The condenser tube of claim 2, wherein the plurality of surface enhancements each extend downward from the exterior surface.

6. The condenser tube of claim 1, wherein the plurality of surface enhancements each extend horizontally from the exterior surface.

7. The condenser tube of claim 2, wherein the plurality of surface enhancements comprise a plurality of fins extending from the first end to the second end.

8. The condenser tube of claim 5, wherein the plurality of surface enhancements extend in a parallel configuration and where a first surface enhancement is recessed relative to a second surface enhancement that is above and adjacent to the first surface enhancement.

9. The condenser tube of claim 1, wherein the condenser tube is part of a condenser.

10. The condenser tube of claim 9, wherein the condenser is part of a two-phase immersion cooling system.

11. The condenser tube of claim 1, wherein the surface enhancements are located below a horizontal midplane of the condenser tube.

12. The condenser tube of claim 1, wherein less than half of the top portion comprises surface enhancements.

13. The condenser of claim 1, wherein the surface enhancements comprise a plurality of pointed fins that taper in a direction from a base to a tip of each fin.

14. The condenser of claim 1, wherein the interior surface is substantially smooth.

15. The condenser of claim 3, wherein each fin has a maximum fin length greater than a minimum distance between adjacent fins.

16. A condenser tube comprising:

a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface; and

wherein between 25% and 50% of the exterior surface is substantially smooth, and

wherein between 50% and 75% of the exterior surface comprises surface enhancements.

17. The condenser of claim 1, wherein the interior surface is substantially smooth.

18. The condenser of claim 1, wherein the surface enhancements comprise a plurality of fins that extend longitudinally from the first end to the second end.

19. The condenser of claim 18, wherein the plurality of fins extend radially and downward.

20. A condenser comprising:

an inlet manifold comprising an inlet;

an outlet manifold comprising an outlet;

a plurality of condenser tubes fluidly connecting the inlet manifold to the outlet manifold;

wherein at least one of the condenser tubes comprises:

a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a heat transfer fluid;

wherein the interior surface is substantially smooth;

wherein the exterior surface has a top portion and a bottom portion, and

wherein the top portion comprises a region that is substantially smooth, and the bottom portion comprises a plurality of surface enhancements extending longitudinally from the first end to the second end.