Patent Publication Number: US-11042200-B2

Title: Liquid soluble gas sealed cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of, and claims priority to, U.S. patent application Ser. No. 16/936,254, titled “LIQUID SOLUBLE GAS SEALED COOLING SYSTEM,” filed on Jul. 22, 2020, which is a continuation application of, and claims priority to, U.S. patent application Ser. No. 16/555,831, now U.S. Pat. No. 10,761,577, titled “LIQUID SOLUBLE GAS SEALED COOLING SYSTEM,” filed on Aug. 29, 2019. The disclosure of the foregoing applications are incorporated herein by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     Large computer, storage, or networking server systems, typically used in datacenters, require cooling. Often times liquid cooling systems are used to cool these systems. The liquid cooling system is typically a closed loop system that communicates chilled cooling fluid (coolant) to a cooling plate that is thermally coupled to a heat load (e.g., electronics) that requires cooling. The cooling plate transfers heat from the heat load to the coolant, and the heated coolant is communicated to a heat exchange for chilling. 
     Typically a rack or a chassis that is liquid cooled also includes multiple different airflow domains. An airflow domain, or more generally a gas flow domain, is a volume that is sealed from other gas flow domains and through which a gas (typically air) can be maintained at a positive pressure relative to ambient atmospheric pressure. There are liquid and air cooled equipment that require two or more gas flow domains that are independent and fluidly isolated from each other (e.g., fluidly sealed relative to each other). When a liquid coolant leak occurs in one of the domains, however, the coolant will tend to collect in the domain, as the domain is fluidly sealed from the other domains and from the external atmosphere. 
     To prevent pooling of coolant, some systems have unsealed airflow domains, typically through an unsealed drain outlet, to allow drainage from the airflow domain having liquid cooling components. This design, however, negatively impacts the air cooling effectiveness the airflow domains that are in communication with the unsealed drain outlet. Another design involves separate drainage paths for each domain. This design is more complex than the prior design, however, and is difficult to scale. 
     SUMMARY 
     The technology in this patent application is related to systems and methods for integrating liquid soluble seals/gaskets in air and water cooled electronic equipment to prevent coolant pooling within the volume that defines an air flow domain. 
     In general, one innovative aspect of the subject matter described in this specification can be embodied in an apparatus including a housing having a drain surface, and having defined within: a first volume, and a second volume that is fluidly isolated from the first volume by a separating member, wherein the separating member includes a first section that is insoluble to a cooling liquid and one or more second sections, wherein each of the one or more second sections is soluble to the cooling liquid; and wherein: the first volume defines a gas flow domain through which a gas may flow; the first volume is positioned above the second volume, and the drain surface is a bottom surface of the second volume; and when the second sections of the separating member are dissolved by the cooling liquid, open spaces are formed in the separating member and the cooling liquid drains from the first volume into the second volume. 
     Another innovative aspect of the subject matter described in this specification can be embodied in an apparatus including a first airflow domain, a liquid cooling exchange system located within the first airflow domain that includes a cooling liquid that is circulated within the liquid cooling exchange system; and a second airflow domain that is fluidly separated from the first airflow domain at least in part by a gas seal component, wherein the gas seal component comprises a liquid soluble material that is soluble to the cooling liquid. 
     Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. The liquid soluble air seals/gaskets dissolve when they come into physical contact with coolant, thus allowing for automatic opening of a drain path when the leak occurs. There is no need for an electro-mechanical switching device, or purely mechanical switching device, to open a drain path; instead, inexpensive and sacrificial sealing material is used to plug the drain path and seal the domain. In the event of a leak, the sacrificial sealing material dissolves, allowing the coolant to drain. The drain locations and drain path may thus be positioned virtually anywhere in the airflow domain, as design factors relating to drain pipes, pumps, etc., are eliminated. Instead, only a hole or space need be created, and then plugged with the sacrificial sealing material, which facilitates multiple drain path design options. 
     The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are cross-sectional and top sectional views of an apparatus, such as a server rack, that employs a liquid soluble gas sealed cooling system. 
         FIG. 1C  is a cross-sectional view of the apparatus of  FIGS. 1A and 1B , and further illustrating a coolant leak prior to dissolution of sacrificial sealing material. 
         FIG. 1D  is a cross-sectional view of the apparatus of  FIG. 1C , illustrating a drain path after dissolution of the sacrificial sealing material. 
         FIGS. 2A and 2B  are cross-sectional and top sectional views of an apparatus implementing another implementation of a liquid soluble gas sealed cooling system. 
         FIGS. 3A and 3B  are cross-sectional and top sectional views of an apparatus implementing yet another implementation of a liquid soluble gas sealed cooling system. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     This disclosure describes a liquid soluble gas sealed cooling architecture that provides a fluidly sealed airflow domain with liquid cooling components. The airflow domain is fluidly sealed, in part, by sections that are made of a sacrificial sealing material that is liquid soluble to the coolant used in the liquid cooling components. For example, if water is the coolant, then the sacrificial sealing material is made of a water-soluble material that dissolves when in contact with water (or otherwise structurally fails) to unseal the fluidly sealed domain and provide a drain path for the coolant. 
     The sacrificial sealing material may be used as one or more of seals, gaskets or plugs. When the sacrificial sealing material is dissolved, liquid is then allowed to flow through the drainage paths and drain from the equipment in a controlled manner. The liquid soluble sealing material thus allows for airflow domains to be fluidly sealed during normal operation but become unsealed in the presence of a coolant leak to allow drainage of the coolant. 
     These features and additional features are described in more detail below. 
       FIGS. 1A and 1B  are cross-sectional and top sectional views of an apparatus  100 , such as a server rack, that employs a liquid soluble gas sealed cooling system. The apparatus  100  includes a housing  102  having a drain surface  104 , i.e., a surface in the downward direction of gravity relative to other components and from which fluid may drain through a drain outlet  106 . The drain surface  104  may be a bottom surface upon which the apparatus  100  rests, or, alternatively, may be an intermediate divider below which are additional airflow domains. 
     The housing  100  includes various walls and structures that define a first volume  120  and a second volume  140 . The first volume  120  is positioned above the second volume  140 , and the bottom of the second volume  140  is defined by the drain surface  104 . 
     The second volume  140  is fluidly isolated from the first volume  120  by a separating member  150 . The separating member  150  includes components that are insoluble to coolant, and components that are soluble to the coolant. In the example implementation of  FIGS. 1A and 1B , the separating member  150  includes a first section  152  that is insoluble to the coolant, and one or more second sections, e.g., second sections  154  and  156 , that are soluble to the coolant. 
     The first section  152  may be a printed circuit board that includes electronic components that, when powered, generate a heat load. Alternatively, the first section  152  may be a mounting structure upon which one more circuit boards, fans, or other electronic components may be mounted and powered. In still other implementations, the first section  152  may simply be an interior plate or divider section, and electronic components may be mounted elsewhere within the first volume  120 . 
     The second sections  154  and  156  are gas sealing component that are used to fill a gap that exists between the side edges  160  and  162  of the first section  152  and respective side walls  108  and  110 . The second sections are sacrificial sealing material that dissolve when in contact with the coolant. The type of sacrificial sealing material may depend on the coolant used. For example, when water is the coolant, the sacrificial sealing material may be made from a biodegradable plant product, such as material made from grain sorghum or corn starch, the same material that is used to make packing peanuts. Other materials that may be used include polyvinyl alcohol (PVA). More generally, the sacrificial sealing material is any material that dissolves when in contact with the particular coolant used, and when dry provides sufficient striatal integrity at a normal operation temperature (e.g., up to 140 degrees Fahrenheit/60 degrees Celsius) to provide a fluid (gas) isolation at a typical pressure differential between the airflow domains  120  and  140 . 
     The first volume  120  defines a sealed gas flow domain through which a gas may flow. For example, gas in the volume  120  may be maintained at a positive pressure relative to ambient atmospheric pressure. As used in this specification, the term “sealed” does not necessarily mean hermetically sealed or otherwise sealed in a manner that fluid (gas or liquid) may not escape. Instead, the term “sealed” means, in the context of a domain, that a gas may be maintained at a pressure that is higher relative to another domain or an external domain. Thus, the first section  152  and second sections  154  and  156  need not provide a true hermetic seal, but need only provide sufficient isolation to maintain gas flow within the domain. 
     Assuming the first section  152  is a printed circuit board, the first section  152  may be coupled to a heat dissipating component. Within the first volume  140  is a thermal coupler  170  and a cold plate  172 . The cold plate  172  is coupled to a tubing  174  though which chilled cooling liquid is circulated. In operation, the electronic components generate a heat load that is cooled by the cooling system by coupling of the heat load through the thermal coupler  170  to the cold plate  172 . The first volume  120  and the second volume  140  are fluidly isolated by means of the first section  152  and the second sections  154  and  156 . In the event of a coolant leak, however, the second sections  154  and  156  will dissolve to allow for drainage of the coolant. Such a scenario is described with reference to  FIGS. 1C and 1D . In particular,  FIG. 1C  is a cross-sectional view of the apparatus of  FIGS. 1A and 1B , and illustrate a coolant leak prior to dissolution of sacrificial sealing material of the second sections  154  and  156 .  FIG. 1D  is the cross-sectional view illustrating a drain path after dissolution of the sacrificial sealing material. 
       FIG. 1C  illustrates a leak occurring at the cold plate  172 , and a resultant pooling of coolant  180  in the first volume  120 . However, because the coolant  180  is in contact with the second section  154  and  156 , and because the second sections  154  and  156  are made of a material that is soluble to the coolant, the second sections  154  and  156  begin to dissolve. Eventually the structural integrity of the sacrificial sealing material fails, and a drain path opens from the first volume  120  to the second volume  140 , as shown in  FIG. 1D . The drain path is defined by the spaces that connect the first volume  120  to the second volume  140 , and created by the dissolution of the sacrificial sealing material. The coolant  180  then collects on the drain surface  104  and drains through the drain outlet  106 . 
     In the example implementation of  FIGS. 1A-1D , the first section  152  defines edge peripheries  160  and  162  that are separate from the side walls  108  and  110  of the housing  102 . But other configurations can also be used. For example, in  FIGS. 2A and 2B , an alternate implementation of the apparatus  200  includes a first section  252  that has multiple holes filled by second sections  254 , where each second section is made of the sacrificial sealing material. 
     By way of another example, in  FIGS. 3A and 3B , an alternate implementation of the apparatus  300  includes a first section  352  and second sections  354  and  356  that fill slots defined in the first section  352 . Still other configurations can also be used. For example, instead of multiple gas seal components spaced apart from each other, a single gas seal component can be used to fill a single space in the first section. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any features or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.