Patent Publication Number: US-2023164952-A1

Title: Systems and methods for recovering fluid in immersion-cooled datacenters

Description:
BACKGROUND 
     Background and Relevant Art 
     Computing devices can generate a large amount of heat during use. The computing components can be susceptible to damage from the heat and commonly require cooling systems to maintain the component temperatures in a safe range during heavy processing or usage loads. Liquid cooling can effectively cool components as liquid working fluids have more thermal mass than air or gas cooling. The liquid working fluid can be maintained at a lower temperature by allowing vaporized fluid to rise out of the liquid. The vapor in the cooling liquid can adversely affect the cooling performance of the working fluid. The vapor can be condensed and returned to the immersion tank. 
     BRIEF SUMMARY 
     In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, and a fluid pump. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid pump is configured to circulate a working fluid from the catch pan to the housing. 
     In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, a fluid reservoir, and a fluid pump. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid reservoir is in fluid communication with the housing and configured to provide working fluid to the housing. The fluid pump is configured to circulate the working fluid from the catch pan to the fluid reservoir. 
     In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, a fluid reservoir, a fluid pump, and a level sensor. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid reservoir is in fluid communication with the housing and configured to provide working fluid to the housing. The fluid pump is configured to circulate the working fluid from the catch pan to the fluid reservoir. The level sensor is positioned in the catch pan and in data communication with the fluid pump. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed 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 as an aid in determining the scope of the claimed subject matter. 
     Additional features and advantages will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the teachings herein. Features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. Features of the present disclosure will become more fully apparent from the following description and appended claims or may be learned by the practice of the disclosure as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other features of the disclosure can be obtained, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic or exaggerated representations of concepts, at least some of the drawings may be drawn to scale. Understanding that the drawings depict some example embodiments, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG.  1    is a side schematic representation of an immersion cooling system, according to at least one embodiment of the present disclosure; 
         FIG.  2    is a side schematic representation of an immersion cooling system with an external condenser, according to at least one embodiment of the present disclosure; 
         FIG.  3    is a side schematic representation of an immersion cooling system with an internal condenser and a catch pan, according to at least one embodiment of the present disclosure; 
         FIG.  4    is a side schematic representation of an immersion cooling system configured to recirculate leaked working fluid from a catch pan, according to at least one embodiment of the present disclosure; 
         FIG.  5    is a side schematic representation of an immersion cooling system where a catch pan is a fluid reservoir, according to at least one embodiment of the present disclosure; and 
         FIG.  6    is a perspective cutaway view of an immersion cooling system with a plurality of housings above a catch pan. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to systems and methods for thermal management of electronic devices or other heat-generating components Immersion chambers surround the heat-generating components in a liquid working fluid, which conducts heat from the heat-generating components to cool the heat-generating components. As the working fluid absorbs heat from the heat-generating components, the temperature of the working fluid increases. In some embodiments, the hot working fluid can be circulated through the thermal management system to cool the working fluid and/or replace the working fluid with cool working fluid. In some embodiments, the working fluid vaporizes, introducing vapor into the liquid of the working fluid which rises out of the liquid phase, carrying thermal energy away from the heat-generating components in the gas phase via the latent heat of boiling. 
     In large-scale computing centers, such as cloud-computing centers, data processing centers, data storage centers, or other computing facilities, immersion cooling systems provide an efficient method of thermal management for many computing components under a variety of operating loads. In some embodiments, an immersion cooling system includes a working fluid in an immersion chamber and a heat exchanger to cool the liquid phase and/or a condenser to extract heat from the vapor phase of the working fluid. The heat exchanger may include a condenser that condenses the vapor phase of the working fluid into a liquid phase and returns the liquid working fluid to the immersion chamber. In some embodiments, the liquid working fluid absorbs heat from the heat-generating components, and one or more fluid conduits direct the hot liquid working fluid outside of the immersion chamber to a radiator, heat exchanger, or region of lower temperature to cool the liquid working fluid. Fluid conduits include closed tubes or pipes, such as metal pipes, plastic pipes, or flexible pipes. Fluid conduits also include open conduits, such as troughs, funnels, spillways, spouts, nozzles, or other open structures configured to direct fluid flow. 
     Whether the immersion cooling system is a two-phase cooling system (wherein the working fluid vaporizes and condenses in a cycle) or a one-phase cooling system (wherein the working fluid remains in a single phase in a cycle), the heat transported from the heat-generating components outside of the immersion chamber is further exchanged with an ambient fluid to exhaust the heat from the system. 
     A conventional immersion cooling system  100 , shown in  FIG.  1   , includes an immersion tank  102  containing an immersion chamber  104  and a condenser  106  in the immersion chamber  104 . The immersion chamber  104  contains a working fluid that has a liquid working fluid  108  and a vapor working fluid  110  portion. The liquid working fluid  108  creates an immersion bath  112  in which a plurality of heat-generating components  114  are positioned to heat the liquid working fluid  108  on supports  116 . 
     Referring now to  FIG.  2   , an immersion cooling system  200  according to the present disclosure includes an immersion tank  202  defining an immersion chamber  204  with a working fluid positioned therein. The working fluid transitions between a liquid working fluid  208  phase and a vapor working fluid  210  phase to remove heat from hot or heat-generating components  214  in the immersion chamber  204 . The liquid working fluid  208  more efficiency receives heat from the heat-generating components  214  and, upon transition to the vapor working fluid  210 , the vapor working fluid  210  can be removed from the immersion tank  202 , cooled and condensed by the condenser  206  (or other heat exchanger) to extract the heat from the working fluid, and the liquid working fluid  208  can be returned to the liquid immersion bath  212 . 
     In some embodiments, the immersion bath  212  of the liquid working fluid  208  has a plurality of heat-generating components  214  positioned in the liquid working fluid  208 . The liquid working fluid  208  surrounds at least a portion of the heat-generating components  214  and other objects or parts attached to the heat-generating components  214 . In some embodiments, the heat-generating components  214  are positioned in the liquid working fluid  208  on one or more supports  216 . The support  216  may support one or more heat-generating components  214  in the liquid working fluid  208  and allow the working fluid to move around the heat-generating components  214 . In some embodiments, the support  216  is thermally conductive to conduct heat from the heat-generating components  214 . The support(s)  216  may increase the effective surface area from which the liquid working fluid  208  may remove heat through convective cooling. 
     In some embodiments, the heat-generating components  214  include electronic or computing components or power supplies. In some embodiments, the heat-generating components  214  include computer devices, such as individual personal computers or server blade computers. In some embodiments, one or more of the heat-generating components  214  includes a heat sink or other device attached to the heat-generating component  214  to conduct away thermal energy and effectively increase the surface area of the heat-generating component  214 . In some embodiments, the heat-generating components  214  include an electric motor. 
     As described, conversion of the liquid working fluid  208  to a vapor phase requires the input of thermal energy to overcome the latent heat of vaporization and may be an effective mechanism to increase the thermal capacity of the working fluid and remove heat from the heat-generating components  214 . Because the vapor working fluid  210  rises in the liquid working fluid  208 , the vapor working fluid  210  can be extracted from the immersion chamber  204  in an upper vapor region of the chamber. A condenser  206  cools part of the vapor working fluid  210  back into a liquid working fluid  208 , removing thermal energy from the system and reintroducing the working fluid into the immersion bath  212  of the liquid working fluid  208 . The condenser  206  radiates or otherwise dumps the thermal energy from the working fluid into the ambient environment or into a conduit to carry the thermal energy away from the cooling system. 
     In conventional immersion cooling systems, a liquid-cooled condenser is integrated into the immersion tank and/or the chamber to efficiently remove the thermal energy from the working fluid. In some embodiments according to the present disclosure, an immersion cooling system  200  for thermal management of computing devices allows at least one immersion tank  202  and/or chamber  204  to be connected to and in fluid communication with an external condenser  206 . In some embodiments, an immersion cooling system  200  includes a vapor return line  218  that connects the immersion tank  202  to the condenser  206  and allows vapor working fluid  210  to enter the condenser  206  from the immersion tank  202  and/or chamber  204  and a liquid return line  220  that connects the immersion tank  202  to the condenser  206  and allows liquid working fluid  208  to return to the immersion tank  202  and/or chamber  204 . 
     The vapor return line  218  may be colder than the boiling temperature of the working fluid. In some embodiments, a portion of the vapor working fluid  210  condenses in the vapor return line  218 . The vapor return line  218  can, in some embodiments, be oriented at an angle such that the vapor return line  218  is non-perpendicular to the direction of gravity. The condensed working fluid can then drain either back to the immersion tank  202  or forward to the condenser  206  depending on the direction of the vapor return line  218  slope. In some embodiments, the vapor return line  218  includes a liquid collection line or valve, like a bleeder valve, that allows the collection and/or return of the condensed working fluid to the immersion tank  202  or condenser  206 . 
     In some examples, an immersion cooling system  200  includes an air-cooled condenser  206 . An air-cooled condenser  206  may require fans or pumps to force ambient air over one or more heat pipes or fins to conduct heat from the condenser to the air. 
       FIG.  3    is a schematic representation of an immersion cooling system  300  with localized immersion chambers  304  around a server computer  324  to capture and pool liquid working fluid  308  adjacent the greatest heat-generating components  314 . Working fluid is recycled through the thermal management system, and, in some embodiments, the working fluid is a dielectric fluid or other fluid that is expensive. A thermal management system that uses less working fluid and/or uses the working fluid more efficiently allows for cost savings in the working fluid. In some embodiments, the working fluid is relatively dense and containing large volumes of the working fluid requires a strong container. Building and maintaining containers for large volumes and/or masses of working fluid can increase construction costs and container weight, which limits transport and maintenance of the containers. 
     In a conventional immersion tank, the liquid pressure increases as depth of the immersion bath increases. In conventional tanks and fluids, a depth of 1 meter results in a 2.3 pounds per square inch (PSI) increase. The increased pressure results in an increase in the boiling point for the working fluid and a resulting temperature increase of the components adjacent the working fluid at the bottom of the immersion bath. When separate immersion chambers are placed around heat-generating components, and/or the boards are oriented horizontally, the columnar pressure of the fluid around the component is reduced and produces lower operating temperatures for the component. In at least one example, a working fluid exhibits a 4° C. decrease in temperature relative to a component at a depth of 1 meter in a conventional immersion tank. 
     As the working fluid carries away thermal energy through latent heat of boiling, managing the boiling temperature of the working fluid is beneficial for the performance of the immersion cooling system. In some embodiments, the liquid working fluid receives heat in a cooling volume of working fluid immediately surrounding the heat-generating components. The cooling volume is the region of the working fluid (including both liquid and vapor phases) that is immediately surrounding the heat-generating components and is responsible for the convective cooling of the heat-generating components. In some embodiments, the cooling volume is the volume of working fluid within 5 millimeters (mm) of the heat-generating components. 
     The working fluid has a boiling temperature below a critical temperature at which the heat-generating components experience thermal damage. For example, the heat-generating components may be computing components that experience damage above 100° Celsius (C). In some embodiments, the boiling temperature of the working fluid is less than a critical temperature of the heat-generating components. In some embodiments, the boiling temperature of the working fluid is less about 90° C. In some embodiments, the boiling temperature of the working fluid is less about 80° C. In some embodiments, the boiling temperature of the working fluid is less about 70° C. In some embodiments, the boiling temperature of the working fluid is less about 60° C. In some embodiments, the boiling temperature of the working fluid is at least about 35° C. In some embodiments, the working fluid includes water. In some embodiments, the working fluid includes glycol. In some embodiments, the working fluid includes a combination of water and glycol. In some embodiments, the working fluid is an aqueous solution. In some embodiments, the working fluid is an electronic liquid, such as FC-72 available from 3M, or similar non-conductive fluids. In some embodiments, the heat-generating components, supports, or other elements of the immersion cooling system positioned in the working fluid have nucleation sites on a surface thereof that promote the nucleation of vapor bubbles of the working fluid at or below the boiling temperature of the working fluid. 
     In some embodiments according to the present disclosure, a housing  326  is positioned around or on a server computer  324  or other electronic device to capture the liquid working fluid  308  adjacent to at least one heat-generating component  314  of the server computer  324  in an immersion chamber  304 . In some embodiments, the housing  326  includes a stamped metal or polymer sheet. In some embodiments, the housing  326  includes an injection molded sheet. The housing  326  may have planar or curved surfaces to define a portion of the immersion chamber  304 . In some embodiments, the housing  326  defines a portion of a rectangular prism or box-shaped immersion chamber  304  around the heat-generating electronic components  314 . In some embodiments, at least a portion of the housing  326  is contoured to follow the shape of the heat-generating electronic components  314 . 
     The housing  326  allows for the immersion cooling system  300  to use less working fluid than a conventional immersion cooling system in which the entire tank  302  is filled with working fluid into which the heat-generating components  314  are immersed. The housing  326  contains the liquid working fluid  308  around the heat-generating components, and, when the liquid working fluid  308  vaporizes, the vapor working fluid  310  passes through a vapor return line  318  to the condenser  306 . In single-phase cooling systems, the condenser  306  may be a heat exchanger or radiator to cool hot liquid working fluid  308  cycled out of the housing  326 . 
     The liquid working fluid  308  is stored in a fluid reservoir  328  from which a fluid pump  330  may draw or push the liquid working fluid  308  to the immersion chamber  304  contained in the housing  326 . In some embodiments, a portion of the liquid working fluid  308  may leak from the housing  326 , fluid reservoir  328 , or other fluid conduits of the thermal management system. In some embodiments, a portion of the liquid working fluid  308  may leak from the housing  326 , fluid reservoir  328 , or other fluid conduits of the thermal management system as incoming liquid working fluid  308  flows into the immersion chamber  304  from the pump  330 . In some embodiments, a portion of the liquid working fluid  308  may leak from the housing  326 , fluid reservoir  328 , or other fluid conduits of the thermal management system as the vapor working fluid  310  returns from the immersion chamber  304 . In conventional thermal management systems, a catch pan  332  is positioned under the housing  326 , fluid reservoir  328 , condenser  306  (or heat exchanger) or other fluid conduits of the thermal management system to capture the leaked working fluid. A leak sensor  334  may indicate to a technician when a leak has occurred. 
     The leaked working fluid is lost to the system, and, in the case of persistent leak, the housing  326 , fluid reservoir  328 , condenser  306  (or heat exchanger) or other fluid conduits of the thermal management system may substantially empty of working fluid, preventing effective thermal management of the server computer  324  or other heat-generating components  314 . In some examples, a portion of the working fluid is lost to the system, and the air in the housing  326 , fluid reservoir  328 , condenser  306  (or heat exchanger) or other fluid conduits of the thermal management system may cause intermittent delivery of liquid working fluid  308 , resulting in a water hammer effect that may damage the server computer  324  or other heat-generating components  314 . By opening at least a portion of the working fluid circulation system, such as a catch pan  332  or fluid reservoir  328 , to ambient atmosphere (inside the tank  302  or outside the tank  302 ), an immersion cooling system according to the present disclosure may limit and/or prevent the water hammer effect. 
       FIG.  4    illustrates an example of an immersion cooling system  400  that allows at least a portion of the leaked working fluid to be reintroduced to the fluid reservoir or other portions of the immersion cooling system  400  to extend the effective cooling capability of the immersion cooling system  400 . By reintroducing the leaked working fluid  436  to the system, technicians may have more time to respond to a leak before the immersion cooling system  400  runs dry and the heat-generating components  414  lack thermal management. 
     In some embodiments, any or all of the fluid reservoir  428 , condenser  406 , fluid pump  430 - 1 , housing  426 , and fluid conduits therebetween are positioned above the catch pan  432 . In some embodiments, a component of the immersion cooling system  400  is positioned above the catch pan  432  when the entire component is located above the catch pan  432  in the direction of gravity or a drip point of the component is located above the catch pan  432  in the direction of gravity. In some embodiments, a component of the immersion cooling system  400  is positioned above the catch pan  432  when at least 75% of the component is located above the catch pan  432  in the direction of gravity or a drip point of the component is located above the catch pan  432  in the direction of gravity. In some embodiments, a component of the immersion cooling system  400  is positioned above the catch pan  432  when at least 50% of the component is located above the catch pan  432  in the direction of gravity or a drip point of the component is located above the catch pan  432  in the direction of gravity. For example, a housing  426  (or other component) is positioned above the catch pan  432  when the entire housing  426  is located above the catch pan  432  such that any leaked working fluid  436  that drips from any portion of the housing  426  falls directly into the catch pan  432  under the influence of gravity. 
     In some examples, a housing  426  (or other component) is positioned above the catch pan  432  when a drip point  438  of the housing  426  is above the catch pan  432  such that any leaked working fluid  436  that leaks from the housing  426  is guided, such as by cohesion, to the drip point  438  and, subsequently, falls directly into the catch pan  432  under the influence of gravity. In the embodiment illustrated in  FIG.  4   , a single catch pan  432  is located under all of the other components of the immersion cooling system  400 , however, it should be understood that multiple catch pans  432  may be used to catch leaks from any number of components of the immersion cooling system  400 . 
     The catch pan  432  may include a level sensor  440  that measures includes a pressure or electrical contact that determines when leaked working fluid  436  is present in the catch pan  432 . The level sensor  440  can determine a fluid level of the leaked working fluid  436  and communicate with one or more components of the immersion cooling system  400  or other systems. For example, the level sensor  440  may be in electrical or data communication with a second fluid pump  430 - 2 . In response to the level sensor  440  detecting the presence of leaked working fluid  436  at a high enough level in the catch pan  432 , the second fluid pump  430 - 2  may pump the leaked working fluid  436  to the fluid reservoir  428 . In some embodiments, a fluid filter  442  may be positioned before and/or after the second fluid pump  430 - 2  to clean the leaked working fluid  436  before the leaked working fluid  436  returns to the fluid reservoir  428  and mixes with the liquid working fluid  408  therein. In some embodiments, the second fluid pump  430 - 2  draws the leaked working fluid  436  from the catch pan  432  proximate the level sensor  440 , such that the second fluid pump  430 - 2  draws from the region of the catch pan  432  that is representative of the fluid level measured by the level sensor  440 . 
     In the illustrated embodiment of  FIG.  4   , the level sensor  440  is located at a first end of the catch pan  432  and the second fluid pump  430 - 2  draws from the first end. In some embodiments, the catch pan  432  has a sloped bottom surface that slopes toward the first end, such that leaked working fluid  436  flows toward the first end, pooling the leaked working fluid  436  at or near the level sensor  440  and an intake conduit  444  of the second fluid pump  430 - 2  to more efficiently return the leaked working fluid  436  to the fluid reservoir  428 . As described above, all components of the immersion cooling system illustrated in  FIG.  4    are positioned above the catch pan  432 , allowing leaked working fluid  436  that is leaked from anywhere in the immersion cooling system  400  (e.g., housing  426 , fluid reservoir  428 , condenser  406  or heat exchanger, or other fluid conduits) will collect in the catch pan  432  to be detected by the level sensor  440 , filtered by the filter  442 , and returned to the fluid reservoir  428  by the second fluid pump  430 - 2 . 
     As described herein, by opening at least a portion of the working fluid circulation system, such as a catch pan  432  or fluid reservoir  428 , to ambient atmosphere (inside the tank  402  or outside the tank  402 ), an immersion cooling system  400  according to the present disclosure may limit and/or prevent the water hammer effect. In some embodiments, a vent is positioned in the fluid reservoir  428  to allow the working fluid circulation system to vent to ambient air in the tank  402 . In some embodiments, a vent  445  is positioned in a wall of the tank  402  to allow the interior volume of the tank  402  to vent to atmosphere. In some embodiments, the vent  445  is positioned in a top surface or lid of the tank  402  to allow the interior volume of the tank  402  to vent to atmosphere. In some embodiments, the tank  402  is open across substantially all of the top surface (i.e., a lid is removed) to allow the interior volume of the tank  402  to vent to atmosphere. 
     Because the immersion cooling system  400  may draw liquid working fluid  408  from the catch pan  432 , in some embodiments, the fluid reservoir  428  may have a reservoir volume that is greater than the total volume of the initial liquid working fluid  408  and the volume of the housing  426 . For example, a conventional system may have a fluid reservoir with a volume that substantially matches the volume of the conduits, housing, condenser, etc. to hold a volume of liquid working fluid  408  needed to fill the conduits, housing, condenser, etc. In some embodiments according to the present disclosure, additional liquid working fluid  408  may be introduced to the fluid reservoir  428  from the catch pan  432 . Therefore, a fluid reservoir  428  may have a volume that is greater than or equal to the initial volume of liquid working fluid  408  in the system and the volume of the housing  426  to accommodate additional liquid working fluid  408  introduced to the system. 
     In some embodiments, the catch pan  432  may be the fluid reservoir  428 .  FIG.  5    is a schematic representation of another embodiment of an immersion cooling system  500 . The immersion cooling system  500  includes a housing  526  with heat-generating components  514  therein and a liquid working fluid  508  that is circulated through the housing  526 . A fluid pump  530  moves the liquid working fluid  508  from the catch pan  532 /fluid reservoir  528  via an intake conduit  544 . The liquid working fluid  508  may be filtered in a filter  542  before being pumped into the housing  526  to cool the heat-generating components  514 . 
     The immersion cooling system  500  may be a two-phase cooling system or a single-phase cooling system. For example, the two-phase cooling system may include a condenser  506  that condenses a vapor working fluid from the housing  526  back into a liquid working fluid  508 , which is returned to the catch pan  532 /fluid reservoir  528 . In other examples, the single-phase version of the immersion cooling system  500  may use a heat exchanger to cool the liquid working fluid  508  before the liquid working fluid  508  is returned to the catch pan  532 /fluid reservoir  528 . In yet other examples, a single-phase immersion cooling system may lack a condenser or heat-exchanger, and the relatively large surface area of the catch pan  532 /fluid reservoir  528  may function as the heat exchanger to reject heat from the liquid working fluid  508  to the environment. 
     Some embodiments of the immersion cooling system  500  include a filter  542  to filter the liquid working fluid  508  because the open catch pan  532 /fluid reservoir  528  may allow contaminants to enter the liquid working fluid  508 . In some embodiments, the tank  502  of the immersion cooling system  500  may be sealed to prevent water vapor from entering the tank  502  and introducing condensation into the liquid working fluid  508  of the open catch pan  532 /fluid reservoir  528 . 
     In some embodiments, the housing  526  does not entirely encase the server computer  524 . The server computer  524  may have a plurality of heat-generating electronic components  514  affixed to a substrate  546 , such as a motherboard. Some electronic components may consume more power and/or generate more heat than other components. The greatest heat-generating components  514  of the server computer  524  may be immersed in liquid working fluid  508 , while lesser heat-generating components  548  may be cooled through ambient gas convection cooling (e.g., a fan blowing on the lesser heat-generating components  548 ) or through overflow liquid working fluid  508  flowing from the immersion chamber  504  defined by the housing  526 . 
     In some embodiments, removing at least a portion of the server computers or other electronic devices from the immersion bath or collection bath can maintain a cleaner, and, therefore, more efficient, working fluid. For example, the elastomers found in electronic connectors, wires, cables, or other components can leach into the liquid working fluid more readily than into the vapor working fluid. The leached elastomers can adversely affect the thermal absorption efficiency of the working fluid, adversely affect the viscosity of the working fluid, adversely affect the boiling temperature of the working fluid, or cause the working fluid to leave a deposit on the heat-generating components, which can adversely affect the thermal transfer (e.g., cooling) from the heat-generating components. 
     In some embodiments, data connectivity may be improved by positioning the connectors of the server computer in a gaseous environment relative to a liquid environment. For example, optical connections, such as fiber optics, may perform better and/or more predictably in a gaseous environment relative to a liquid environment due to differences in the index of refraction between the optical fibers and the liquid environment. 
     Placing the fluid reservoir  528  (i.e., the catch pan  532 ) at the bottom of the immersion cooling system  500  may allow the liquid working fluid  508  condensed by the condenser  506  to be returned to the fluid reservoir  528  more efficiency and/or while using less energy. Because the liquid working fluid  508  is denser than the ambient gases in the tank  502 , the liquid working fluid  508  will preferentially flow from the condenser  506  downward to the fluid reservoir  528 . 
     The incoming liquid working fluid is delivered by, in some embodiments, a manifold that directs the incoming liquid working fluid into the immersion chamber. In some embodiments, the incoming liquid working fluid is introduced through the opening in the top surface of the immersion chamber. In some embodiments, the incoming liquid working fluid is introduced through a port in housing, such as in the lateral wall of the immersion chamber. The incoming liquid working fluid may displace the liquid working fluid in the immersion chamber, at least partially, out an outlet in the housing to circulate the working fluid. 
       FIG.  6    is a perspective view of an immersion cooling system  600  illustrating a plurality of server computers  624  and housings  626  in a row. The manifold  650  may provide incoming liquid working fluid  608  to each of the housings  626  and immersion chambers  604 , individually. The individual immersion chamber  604  for each server computer  624  is a more efficient allocation of liquid working fluid  608  while also providing modularity in the immersion cooling system  600  for maintenance and repairs. While the immersion cooling system  600  may include a condenser and return line(s) to return working fluid from the housing(s)  626  to the fluid reservoir  628 /catch pan  632 , the condenser and liquid return line(s) are not shown in  FIG.  6    due to cutaway view. 
     At least two of the housings  626  are positioned above the fluid reservoir  628 /catch pan  632 . The row of housings  626  can, thereby, share a fluid reservoir  628 /catch pan  632 , such that leaked working fluid from any one of the housings  626  will fall into the fluid reservoir  628 /catch pan  632  and be reintroduced into the manifold  650  to allow recirculation of the working fluid through all of the housings  626  connected to the manifold  650 . In some embodiments, a fluid pump  630  draws liquid working fluid  608  from the fluid reservoir  628 /catch pan  632  and delivers the liquid working fluid  608  to the manifold  650 . In some embodiments, a plurality of fluid pumps  630  draw liquid working fluid  608  from the fluid reservoir  628 /catch pan  632  and deliver the liquid working fluid  608  to the manifold  650 . In at least one embodiment, the immersion cooling system  600  has a fluid pump  630  for each of the housings  626 . 
     INDUSTRIAL APPLICABILITY 
     The present disclosure relates generally to systems and methods for thermal management of electronic devices or other heat-generating components Immersion chambers surround the heat-generating components in a liquid working fluid, which conducts heat from the heat-generating components to cool the heat-generating components. As the working fluid absorbs heat from the heat-generating components, the temperature of the working fluid increases. In some embodiments, the hot working fluid can be circulated through the thermal management system to cool the working fluid and/or replace the working fluid with cool working fluid. In some embodiments, the working fluid vaporizes, introducing vapor into the liquid of the working fluid which rises out of the liquid phase, carrying thermal energy away from the heat-generating components in the gas phase via the latent heat of boiling. 
     In large-scale computing centers, such as cloud-computing centers, data processing centers, data storage centers, or other computing facilities, immersion cooling systems provide an efficient method of thermal management for many computing components under a variety of operating loads. In some embodiments, an immersion cooling system includes a working fluid in an immersion chamber and a heat exchanger to cool the liquid phase and/or a condenser to extract heat from the vapor phase of the working fluid. The condenser condenses the vapor phase of the working fluid into a liquid phase and returns the liquid working fluid to the immersion chamber. In some embodiments, the liquid working fluid absorbs heat from the heat-generating components, and one or more fluid conduits direct the hot liquid working fluid outside of the immersion chamber to a radiator, heat exchanger, or region of lower temperature to cool the liquid working fluid. 
     Whether the immersion cooling system is a two-phase cooling system (wherein the working fluid vaporizes and condenses in a cycle) or a one-phase cooling system (wherein the working fluid remains in a single phase in a cycle), the heat transported from the heat-generating components outside of the immersion chamber is further exchanged with an ambient fluid to exhaust the heat from the system. 
     A conventional immersion cooling system includes an immersion tank containing an immersion chamber and a condenser in the immersion chamber. The immersion chamber contains a working fluid that has a liquid working fluid and a vapor working fluid portion. The liquid working fluid creates an immersion bath in which a plurality of heat-generating components is positioned to heat the liquid working fluid on supports. 
     In some embodiments, an immersion cooling system includes an immersion tank including an immersion chamber with a working fluid positioned therein. The working fluid transitions between a liquid working fluid phase and a vapor working fluid phase to remove heat from hot or heat-generating components in the immersion chamber. The liquid working fluid more efficiency receives heat from the heat-generating components and, upon transition to the vapor working fluid, the vapor working fluid can be removed from the immersion tank, cooled and condensed by the condenser to extract the heat from the working fluid, and the liquid working fluid can be returned to the liquid immersion bath. 
     In some embodiments, the immersion bath of the liquid working fluid has a plurality of heat-generating components positioned in the liquid working fluid. The liquid working fluid surrounds at least a portion of the heat-generating components and other objects or parts attached to the heat-generating components. In some embodiments, the heat-generating components are positioned in the liquid working fluid on one or more supports. The support may support one or more heat-generating components in the liquid working fluid and allow the working fluid to move around the heat-generating components. In some embodiments, the support is thermally conductive to conduct heat from the heat-generating components. The support(s) may increase the effective surface area from which the liquid working fluid may remove heat through convective cooling. 
     In some embodiments, the heat-generating components include electronic or computing components or power supplies. In some embodiments, the heat-generating components include computer devices, such as individual personal computer or server blade computers. In some embodiments, one or more of the heat-generating components includes a heat sink or other device attached to the heat-generating component to conduct away thermal energy and effectively increase the surface area of the heat-generating component. In some embodiments, the heat-generating components include an electric motor. 
     As described, conversion of the liquid working fluid to a vapor phase requires the input of thermal energy to overcome the latent heat of vaporization and may be an effective mechanism to increase the thermal capacity of the working fluid and remove heat from the heat-generating components. Because the vapor working fluid rises in the liquid working fluid, the vapor working fluid can be extracted from the immersion chamber in an upper vapor region of the chamber. A condenser cools part of the vapor working fluid back into a liquid working fluid, removing thermal energy from the system, and reintroducing the working fluid into the immersion bath of the liquid working fluid. The condenser radiates or otherwise dumps the thermal energy from the working fluid into the ambient environment or into a conduit to carry the thermal energy away from the cooling system. 
     In conventional immersion cooling systems, a liquid-cooled condenser is integrated into the immersion tank and/or the chamber to efficiency remove the thermal energy from the working fluid. In some embodiments according to the present disclosure, an immersion cooling system for thermal management of computing devices allows at least one immersion tank and/or chamber to be connected to and in fluid communication with an external condenser. In some embodiments, an immersion cooling system includes a vapor return line that connects the immersion tank to the condenser and allows vapor working fluid to enter the condenser from the immersion tank and/or chamber and a liquid return line that connects the immersion tank to the condenser and allows liquid working fluid to return to the immersion tank and/or chamber. 
     The vapor return line may be colder than the boiling temperature of the working fluid. In some embodiments, a portion of the vapor working fluid condenses in the vapor return line. The vapor return line can, in some embodiments, be oriented at an angle such that the vapor return line is non-perpendicular to the direction of gravity. The condensed working fluid can then drain either back to the immersion tank or forward to the condenser depending on the direction of the vapor return line slope. In some embodiments, the vapor return line includes a liquid collection line or valve, like a bleeder valve, that allows the collection and/or return of the condensed working fluid to the immersion tank or condenser. 
     In some examples, an immersion cooling system includes an air-cooled condenser. An air-cooled condenser may require fans or pumps to force ambient air over one or more heat pipes or fins to conduct heat from the condenser to the air. 
     In some embodiments, an immersion cooling system includes localized immersion chambers around a server computer to capture and pool liquid working fluid adjacent the greatest heat-generating components. Working fluid is recycled through the thermal management system, and, in some embodiments, the working fluid is a dielectric fluid or other fluid that is expensive. A thermal management system that uses less working fluid and/or uses the working fluid more efficiently allows for cost savings in the working fluid. In some embodiments, the working fluid is relatively dense and containing large volumes of the working fluid requires a strong container. Building and maintaining containers for large volumes and/or masses of working fluid can increase construction costs and container weight, which limits transport and maintenance of the containers. 
     In a conventional immersion tank, the liquid pressure increases as depth of the immersion bath increases. In conventional tanks and fluids, a depth of 1 meter results in a 2.3 pounds per square inch (PSI) increase. The increased pressure results in an increase in the boiling point for the working fluid and a resulting temperature increase of the components adjacent the working fluid at the bottom of the immersion bath. When separate immersion chambers are placed around heat-generating components, and/or the boards are oriented horizontally, the columnar pressure of the fluid around the component is reduced and produces lower operating temperatures for the component. In at least one example, a working fluid exhibits a 4° C. decrease in temperature relative to a component at a depth of 1 meter in a conventional immersion tank. 
     In some embodiments according to the present disclosure, a housing is positioned around or on a server computer or other electronic device to capture the liquid working fluid adjacent to at least one heat-generating component of the server computer in an immersion chamber. In some embodiments, the housing includes a stamped metal or polymer sheet. In some embodiments, the housing includes an injection molded sheet. The housing may have planar or curved surfaces to define a portion of the immersion chamber. In some embodiments, the housing defines a portion of a rectangular prism or box-shaped immersion chamber around the heat-generating electronic components. In some embodiments, at least a portion of the housing is contoured to follow the shape of the heat-generating electronic components. 
     The housing allows for the immersion cooling system to use less working fluid than a conventional immersion cooling system in which the entire tank is filled with working fluid into which the heat-generating components are immersed. The housing contains the liquid working fluid around the heat-generating components, and, when the liquid working fluid vaporizes, the vapor working fluid passes through a vapor return line to the condenser. In single-phase cooling systems, the condenser may be a heat exchanger or radiator to cool hot liquid working fluid cycled out of the housing. 
     The liquid working fluid is stored in a fluid reservoir from which a fluid pump may draw or push the liquid working fluid to the immersion chamber contained in the housing. In some embodiments, a portion of the liquid working fluid may leak from the housing, fluid reservoir, or other fluid conduits of the thermal management system. In some embodiments, a portion of the liquid working fluid may leak from the housing, fluid reservoir, or other fluid conduits of the thermal management system as incoming liquid working fluid flows into the immersion chamber from the pump. In some embodiments, a portion of the liquid working fluid may leak from the housing, fluid reservoir, or other fluid conduits of the thermal management system as the vapor working fluid returns from the immersion chamber. In conventional thermal management systems, a catch pan is positioned under the housing, fluid reservoir, condenser (or heat exchanger) or other fluid conduits of the thermal management system to capture the leaked working fluid. A leak sensor may indicate to a technician when a leak has occurred. 
     The leaked working fluid is lost to the system, and, in the case of persistent leak, the housing, fluid reservoir, condenser (or heat exchanger) or other fluid conduits of the thermal management system may substantially empty of working fluid, preventing effective thermal management of the server computer or other heat-generating components. In some examples, a portion of the working fluid is lost to the system, and the air in the housing, fluid reservoir, condenser (or heat exchanger) or other fluid conduits of the thermal management system may cause intermittent delivery of liquid working fluid, resulting in a water hammer effect that may damage the server computer or other heat-generating components. 
     In some examples, an immersion cooling system allows at least a portion of the leaked working fluid to be reintroduced to the fluid reservoir or other portions of the immersion cooling system to extend the effective cooling capability of the immersion cooling system. By reintroducing the leaked working fluid to the system, technicians may have more time to respond to a leak before the immersion cooling system runs dry and the heat-generating components lack thermal management. 
     In some embodiments, any or all of the fluid reservoir, condenser, fluid pump, housing, and fluid conduits therebetween are positioned above the catch pan. In some embodiments, a component of the immersion cooling system is positioned above the catch pan when the entire component or a drip point of the component is located above the catch pan in the direction of gravity. For example, a housing (or other component) is positioned above the catch pan when the entire housing is located above the catch pan such that any leaked working fluid that drips from any portion of the housing falls directly into the catch pan under the influence of gravity. 
     In some examples, a housing (or other component) is positioned above the catch pan when a drip point of the housing is above the catch pan such that any leaked working fluid that leaks from the housing is guided, such as by cohesion, to the drip point and, subsequently, falls directly into the catch pan under the influence of gravity. A single catch pan may be located under all of the other components of the immersion cooling system; however, it should be understood that multiple catch pans may be used to catch leaks from any number of components of the immersion cooling system. 
     The catch pan may include a level sensor that includes a pressure or electrical contact that determines when leaked working fluid is present in the catch pan. The level sensor can determine a fluid level of the leaked working fluid and communicate with one or more components of the immersion cooling system or other systems. For example, the level sensor may be in electrical or data communication with a second fluid pump. In response to the level sensor detecting the presence of leaked working fluid at a high enough level in the catch pan, the second fluid pump may pump the leaked working fluid to the fluid reservoir. In some embodiments, a fluid filter may be positioned before and/or after the second fluid pump to clean the leaked working fluid before the leaked working fluid returns to the fluid reservoir and mixes with the liquid working fluid therein. In some embodiments, the second fluid pump draws the leaked working fluid from the catch pan proximate the level sensor, such that the second fluid pump draws from the region of the catch pan that is representative of the fluid level measured by the level sensor. 
     In some embodiments, the level sensor is located at a first end of the catch pan and the second fluid pump draws from the first end. In some embodiments, the catch pan has a sloped bottom surface that slopes toward the first end, such that leaked working fluid flows toward the first end, pooling the leaked working fluid at or near the level sensor and an intake conduit of the second fluid pump to more efficiently return the leaked working fluid to the fluid reservoir. As described above, all components of the immersion cooling system may be positioned above the catch pan, allowing leaked working fluid that is leaked from anywhere in the immersion cooling system (e.g., housing, fluid reservoir, condenser or heat exchanger, or other fluid conduits) will collect in the catch pan to be detected by the level sensor, filtered by the filter, and returned to the fluid reservoir by the second fluid pump. 
     Because the immersion cooling system may draw liquid working fluid from the catch pan, in some embodiments, the fluid reservoir may have a reservoir volume that is greater than the total volume of the initial liquid working fluid and the volume of the housing. For example, a conventional system may have a fluid reservoir with a volume that substantially matches the volume of the conduits, housing, condenser, etc. to hold a volume of liquid working fluid needed to fill the conduits, housing, condenser, etc. In some embodiments according to the present disclosure, additional liquid working fluid may be introduced to the fluid reservoir from the catch pan. Therefore, a fluid reservoir may have a volume that is greater than or equal to the initial volume of liquid working fluid in the system and the volume of the housing to accommodate additional liquid working fluid introduced to the system. 
     In some embodiments, the catch pan may be the fluid reservoir. For example, the immersion cooling system may include a housing with heat-generating components therein and a liquid working fluid that is circulated through the housing. A fluid pump moves the liquid working fluid from the catch pan/fluid reservoir via an intake conduit. The liquid working fluid may be filtered in a filter before being pumped into the housing to cool the heat-generating components. 
     The immersion cooling system may be a two-phase cooling system or a single-phase cooling system. For example, the two-phase cooling system may include a condenser that condenses a vapor working fluid from the housing back into a liquid working fluid, which is returned to the catch pan/fluid reservoir. In other examples, the single-phase version of the immersion cooling system may use a heat exchanger to cool the liquid working fluid before the liquid working fluid is returned to the catch pan/fluid reservoir. In yet other example, a single-phase immersion cooling system may lack a condenser or heat-exchanger, and the relatively large surface area of the catch pan/fluid reservoir may function as the heat exchanger to reject heat from the liquid working fluid to the environment. 
     Some embodiments of the immersion cooling system include a filter to filter the liquid working fluid because the open catch pan/fluid reservoir may allow contaminants to enter the liquid working fluid. In some embodiments, the tank of the immersion cooling system may be sealed to prevent water vapor from entering the tank and introducing condensation into the liquid working fluid of the open catch pan/fluid reservoir. 
     In some embodiments, the housing does not entirely encase the server computer. The server computer may have a plurality of heat-generating electronic components affixed to a substrate, such as a motherboard. Some electronic components may consume more power and/or generate more heat than other components. The greatest heat-generating components of the server computer may be immersed in liquid working fluid, while lesser heat-generating components may be cooled through ambient gas convection cooling (e.g., a fan blowing on the lesser heat-generating components) or through overflow liquid working fluid flowing from the immersion chamber defined by the housing. 
     In some embodiments, removing at least a portion of the server computers or other electronic devices from the immersion bath or collection bath can maintain a cleaner, and, therefore, more efficient, working fluid. For example, the elastomers found in electronic connectors, wires, cables, or other components can leach into the liquid working fluid more readily than into the vapor working fluid. The leached elastomers can adversely affect the thermal absorption efficiency of the working fluid, adversely affect the viscosity of the working fluid, adversely affect the boiling temperature of the working fluid, or cause the working fluid to leave a deposit on the heat-generating components, which can adversely affect the thermal transfer (e.g., cooling) from the heat-generating components. 
     In some embodiments, data connectivity may be improved by positioning the connectors of the server computer in a gaseous environment relative to a liquid environment. For example, optical connections, such as fiber optics, may perform better and/or more predictably in a gaseous environment relative to a liquid environment due to differences in the index of refraction between the optical fibers and the liquid environment. 
     Placing the fluid reservoir (i.e., the catch pan) at the bottom of the immersion cooling system may allow the liquid working fluid condensed by the condenser to be returned to the fluid reservoir more efficiency and/or while using less energy. Because the liquid working fluid is denser than the ambient gases in the tank, the liquid working fluid will preferentially flow from the condenser downward to the fluid reservoir. 
     The incoming liquid working fluid is delivered by, in some embodiments, a manifold that directs the incoming liquid working fluid into the immersion chamber. In some embodiments, the incoming liquid working fluid is introduced through the opening in the top surface of the immersion chamber. In some embodiments, the incoming liquid working fluid is introduced through a port in housing, such as in the lateral wall of the immersion chamber. The incoming liquid working fluid may displace the liquid working fluid in the immersion chamber, at least partially, out an outlet in the housing to circulate the working fluid. 
     The manifold may provide incoming liquid working fluid to each of the housings and immersion chambers, individually. The individual immersion chamber for each server computer is a more efficient allocation of liquid working fluid while also providing modularity in the immersion cooling system for maintenance and repairs. 
     At least two of the housings may be positioned above the fluid reservoir/catch pan. The row of housings can, thereby, share a fluid reservoir/catch pan, such that leaked working fluid from any one of the housings will fall into the fluid reservoir/catch pan and be reintroduced into the manifold to allow recirculation of the working fluid through all of the housings connected to the manifold. In some embodiments, a fluid pump draws liquid working fluid from the fluid reservoir/catch pan and delivers the liquid working fluid to the manifold. In some embodiments, a plurality of fluid pumps draw liquid working fluid from the fluid reservoir/catch pan and deliver the liquid working fluid to the manifold. In at least one embodiment, the immersion cooling system has a fluid pump for each of the housings. 
     The present disclosure relates to systems and methods for cooling heat-generating components of a computer or computing device according to at least the examples provided in the sections below: 
     [A1] In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, and a fluid pump. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid pump is configured to circulate a working fluid from the catch pan to the housing. 
     [A2] In some embodiments, the fluid pump of [A1] is positioned above the catch pan. 
     [A3] In some embodiments, the immersion cooling system of [A1] or [A2] further includes a cooling conduit providing fluid communication from the fluid pump to the housing, and the cooling conduit is positioned above the catch pan. 
     [A4] In some embodiments, the immersion cooling system of any of [A1] through [A3] further includes a heat exchanger positioned above the catch pan. 
     [A5] In some embodiments, the heat exchanger of [A4] is a condenser. 
     [A6] In some embodiments, the immersion cooling system of [A5] further includes return conduit providing fluid communication from the housing to the condenser, and the return conduit is positioned above the catch pan. 
     [A7] In some embodiments, the immersion cooling system of any of [A1] through [A6] further includes a filter configured to filter contaminants from the working fluid. 
     [A8] In some embodiments, the filter of [A7] is positioned between an intake conduit and the fluid pump and configured to filter contaminants from the working fluid between the catch pan and the fluid pump. 
     [A9] In some embodiments, the immersion cooling system of any of [A1] through [A8] is open to ambient atmosphere outside of a tank. 
     [A10] In some embodiments, the tank of [A9] is fully open on a top surface. 
     [A11] In some embodiments, the immersion cooling system of any of [A1] through [A10] further includes a fluid reservoir, and the fluid pump is configured to pump working fluid from the catch pan to the fluid reservoir. 
     [A12] In some embodiments, the heat-generating electronic device of any of [A1] through [A11] is part of a computer that also includes at least one lesser heat-generating components, and the housing is positioned around the heat-generating electronic device and not the lesser heat-generating component. 
     [B1] In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, a fluid reservoir, and a fluid pump. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid reservoir is in fluid communication with the housing and configured to provide working fluid to the housing. The fluid pump is configured to circulate the working fluid from the catch pan to the fluid reservoir. 
     [B2] In some embodiments, the immersion cooling system of [B1] includes a second fluid pump configured to pump working fluid from fluid reservoir to the housing. 
     [B3] In some embodiments, the immersion cooling system of [B1] or [B2] includes a level sensor in data communication with the fluid pump, and the level sensor is configured to measure a fluid level in the catch pan. 
     [B4] In some embodiments, the catch pan of any of [B1] through [B3] is a first catch pan and the immersion cooling system includes a second catch pan, and the fluid reservoir receives working fluid from both the first catch pan and second catch pan. 
     [B5] In some embodiments, the housing of any of [B1] through [B4] is a first housing and the immersion cooling system includes a second housing. The fluid reservoir is in fluid communication with both the first housing and second housing and configured to provide working fluid to the first housing and second housing. 
     [B6] In some embodiments, a volume of the fluid reservoir of any of [B1] through [B5] is greater than a total volume of a liquid phase of the working fluid and an internal volume of the housing. 
     [C1] In some embodiments, an immersion cooling system includes a catch pan, a heat-generating electronic device, a housing, a fluid reservoir, a fluid pump, and a level sensor. The housing is positioned around the heat-generating electronic device, and at least part of the housing is positioned above the catch pan. The fluid reservoir is in fluid communication with the housing and configured to provide working fluid to the housing. The fluid pump is configured to circulate the working fluid from the catch pan to the fluid reservoir. The level sensor is positioned in the catch pan and in data communication with the fluid pump. 
     [C2] In some embodiments, the level sensor and an intake of the fluid pump of [C1] are positioned proximate a first end of the catch pan, and a bottom surface of the catch pan is sloped to direct working fluid to the first end. 
     The articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements in the preceding descriptions. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value. 
     A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims. 
     It should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to “front” and “back” or “top” and “bottom” or “left” and “right” are merely descriptive of the relative position or movement of the related elements. 
     The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.