Patent Publication Number: US-2023164951-A1

Title: Modular liquid cooling architecture for liquid cooling

Description:
BACKGROUND 
     Computer hardware generates heat during operation and tends to operate better and fail at lower rates when cooled. For this reason, cooling systems for computer hardware have been developed. A variety of cooling systems can be found in individual datacenters, which frequently house several types of computer hardware with differing cooling needs. Individual server racks or other cabinet-style housing for hardware may have convective air cooling systems, such as liquid-air heat exchangers, or cold plate systems wherein conductive elements with liquid conduits running therethrough are placed in contact with components to be cooled. Elsewhere in the center, immersion cooling systems may include a tank in which computer hardware may be immersed in evaporable liquid and a condenser positioned above the tank. These solutions can be inconvenient for customers that use the datacenter for hardware with disparate cooling needs because of the additional labor involved in accessing hardware distributed across different locations in the center. Further problems can arise if direct communication is desired between pieces of hardware with different cooling needs. For example, components that generate relatively little heat may be placed in the tank along with components that must be immersion cooled if direct communication between those components is unnecessary, resulting in unnecessary expense and crowding of the tank. Some components cannot be immersion cooled in any case, so placing such components in communication with immersion cooled components can involve significant difficulty. 
     BRIEF SUMMARY 
     Aspects of this disclosure are directed to a modular liquid cooling system that can implement immersion and condenser cooling modules in cooperation with lower cooling capacity modules such as liquid-air exchangers or cold plate arrangements. Racks can be disaggregated to one or more infrastructure modules and one or more payload modules for better flexibility and utilization. The infrastructure module, containing lower power air cooled information technology (“IT”) or other computing equipment, may rely on a low impedance rear door heat exchanger or cold plates with heat transferred locally to facility water. The payload module, containing higher powered IT or other computing equipment, may rely on two phase immersion cooling to transfer heat immediately to facility water. 
     The infrastructure module may house a programmable logic controller (“PLC”) governing the cooling functions of each module. As such, the PLC may govern the infrastructure module&#39;s heat exchanger as well as aspects of the immersion cooling system of each payload module. Power for some or all functions of the payload modules and the computing equipment housed by the payload modules may also be routed though the infrastructure module. Cooling fluid may be supplied to all modules in series or in parallel or first to the infrastructure module, then to each payload module in parallel. 
     In another aspect, a housing and cooling system for computer hardware may comprise an infrastructure module configured for housing computer hardware. The infrastructure module may be equipped with either or both of a convective air cooling system and an arrangement of metal plates connected by one or more conduits for carrying liquid for cooling computer equipment housed by the infrastructure module. The infrastructure module may house a PLC. The system may also comprise a payload module including an immersion cooling system governed by the PLC and located outside of the infrastructure module. 
     In another arrangement according to any of the foregoing, the infrastructure module may include one or more racks of computing hardware having a first power consumption level. 
     In another arrangement according to any of the foregoing, the payload module may include computing hardware having a second power consumption level, the second power consumption level being greater than the first power consumption level. 
     In another arrangement according to any of the foregoing, the payload module may have the dimensions of a single EIA-310 standard server rack or of two or three adjoining EIA-310 standard server racks. 
     In another arrangement according to any of the foregoing, the convective air cooling system includes a liquid-air heat exchanger. 
     In another arrangement according to any of the foregoing, the heat exchanger or conduits of the infrastructure module may be fluidly connected to a condenser of the payload module. 
     In another arrangement according to any of the foregoing, a flow path of cooling fluid through the housing and cooling system may pass through the cooling arrangement of the infrastructure module before reaching the condenser. 
     In another arrangement according to any of the foregoing, the payload module may be a first payload module, and comprising a second payload module including an immersion cooling system, the immersion cooling systems of the first and second payload modules being governed by the PLC through a central fluid management system housed within the infrastructure module. 
     In another arrangement according to any of the foregoing, the infrastructure module may include an infrastructure bus bar and the payload module includes a payload bus bar that is electrically connected to the infrastructure bus bar. 
     In another arrangement according to any of the foregoing, the infrastructure module and the payload module may each include a respective bus bar, the bus bar of the payload module is connected to the bus bar of the infrastructure module, and the bus bar of the infrastructure module is provided with a connector for receiving power from an external power supply. 
     In another example according to any of the foregoing, the payload module may be a first payload module. The immersion cooling system of the first payload module may include a first condenser. The housing and cooling system may also comprise a second payload module, the second payload module may include an immersion cooling system governed by the PLC and including a second condenser. The first condenser and the second condenser may be connected in series along a flow path of cooling fluid. 
     In another example according to any of the foregoing, the housing and cooling system may also comprise a distribution system circulating cooling liquid through the infrastructure and payload modules. The housing and cooling system may also comprise a dry cooler through which the distribution system passes, the dry cooler being configured to exchange heat from the cooling liquid with ambient air. 
     In another arrangement according to any of the foregoing, the infrastructure and payload modules may be connected in series to the distribution system. 
     In another aspect, a method of housing and cooling computer hardware may comprise housing first computer hardware in an infrastructure module that also houses a (“PLC”). The method may also comprise immersing second computer hardware in evaporable liquid within a two phase immersion cooling system housed by a payload module. The payload module may be located outside of the infrastructure module and the immersion cooling system being governed by the PLC. 
     In another arrangement according to any of the foregoing, the method may comprise cooling the first computer hardware with a cooling arrangement included by the infrastructure module, the cooling arrangement of the infrastructure module being either or both of a liquid-air heat exchanger and an arrangement of metal plates connected by one or more conduits for carrying liquid. 
     In another aspect according to any of the foregoing, the method may comprise connecting the cooling arrangement of the infrastructure module and a condenser of the two phase immersion cooling system in parallel to a building liquid supply. 
     In another aspect according to any of the foregoing, the method may comprise connecting the cooling arrangement of the infrastructure module and the condenser in series to a building liquid supply. 
     In another aspect according to any of the foregoing, the method may comprise connecting the cooling arrangement of the infrastructure module and the condenser to the building liquid supply such that liquid is supplied by the building liquid supply to the cooling arrangement of the infrastructure module and is returned to the building liquid supply from the condenser. 
     In another aspect according to any of the foregoing, the method may comprise supplying electrical power to the payload module and the second computer hardware through the infrastructure module. 
     In another aspect according to any of the foregoing, the payload module may be a first payload module, and comprising immersing third computer hardware in evaporable liquid in a tank housed by a second payload module that includes a two phase immersion cooling system. The two phase immersion cooling system of the second payload module may be governed by the PLC. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration of a modular cooling system according to a first arrangement. 
         FIG.  2    is a schematic illustration of a modular cooling system according to a second arrangement. 
         FIG.  3    is a schematic illustration of a modular cooling system according to a third arrangement. 
         FIG.  4    is a schematic illustration of a modular cooling system according to a fourth arrangement. 
         FIG.  5    is a schematic illustration of a modular cooling system according to a fifth arrangement. 
         FIG.  6    is a flowchart of a method of housing and cooling electronic equipment with any of the modular cooling systems illustrated in  FIGS.  1 - 5   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a modular cooling system  100  which may be used for information technology (“IT”) equipment, other computer hardware, or other items that need to be cooled. System  100  includes infrastructure module  110  and first payload module  120 . System  100  of the illustrate arrangement also includes a second payload module  130 , though in system  100  may have as few as one payload module or any plural number of payload modules in other arrangements. 
     Infrastructure module  110  includes a housing for information technology (“IT”) equipment or other electronic hardware. Infrastructure module  110  houses infrastructure hardware  113 , which may be, for example, one or more racks of computer components, servers, other kinds of IT equipment, or other electronics, and which is housed by the housing of infrastructure module  110 . Infrastructure includes and optionally houses a programmable logic controller (“PLC”)  112  and an infrastructure bus bar  114  for conveying electric power to components of, within, or connected to infrastructure module  110 . PLC  112  itself may optionally be included by infrastructure hardware  113 . 
     Infrastructure module  110  may optionally also include a heat exchanger  111  as shown in the illustrated example. Heat exchanger  111  may be, for example, a liquid-air heat exchanger that uses a supply of cooling fluid to cool air for convective cooling of either or both of infrastructure hardware  113  and PLC  112 . Air heated by either or both of infrastructure hardware  113  and PLC  112  may be impelled into heat exchanger  111  and for cooling before being exhausted out of infrastructure module  110  or recirculated within infrastructure module. In other examples, air received into heat exchanger  111  from outside or within infrastructure module  110  may be cooled by heat exchanger  111  first before being impelled across either or both of infrastructure hardware  113  and PLC  112 . Such a liquid-air heat exchanger may be mounted to any wall or exterior surface of the housing of infrastructure module  110 , such as, for example, a rear door or a front door. 
     In other examples, heat exchanger  111  may be a contact-based cold plate system that includes one or more plates of conductive material, such as aluminum, copper, other metals, or certain ceramics or polymers, or any combination thereof. The plates each have at least one conduit extending therealong or therethrough for directing cooling fluid to carry away heat from the cold plates. Either or both of infrastructure hardware  113  and PLC  112  can therefore be cooled by placement in contact with any of the cold plates. 
     Liquid-air heat exchangers and cold plate systems are presented as examples of heat exchanger  111 , but heat exchanger  111  could be another type of heat exchanger having similar capabilities and operating needs. 
     System  100  also includes a first payload module  120 . First payload module  120  includes a housing for electronic hardware, a payload bus bar  124 , and a high-capacity cooling system. Payload bus bar  124  is configured for conveying electric power to components of, within, or connected to first payload module  120 . The high-capacity cooling system may be, for example, a two phase immersion cooling system for electronic or other hardware. Such an immersion cooling system includes a tank for evaporable liquid and a condenser system  121  positioned above the tank or otherwise in a location that vapors from the tank would travel to the condenser system  121  and then return to the tank after condensing to liquid. Examples of suitable evaporable liquids include any of several commercially available dielectric fluids engineered specifically for immersion cooling of computer hardware, though water may be used in some applications, particularly where electrical conductivity of the evaporable fluid is not a concern. Condenser system  121  may be any known type of condenser, but in some examples, condenser system  121  includes one or more tubes carrying a cooling fluid that reduces the tubes to a temperature suitable for condensing vapors rising from the evaporable liquid in the tank. The immersion cooling system also includes a humidity control system  122  for monitoring and adjusting humidity within infrastructure module  120 , via condenser system  121  or otherwise, and a fluid management system  125  for controlling the level of evaporable liquid within the tank. Fluid management system  125  may comprise, for example, any one or any combination of a pump, a filter, and a fluid level monitor for the evaporable fluid in the tank of first payload module&#39;s  120  immersion cooling system. 
     Payload hardware  123  may be one or more racks of electronic equipment immersed in the tank of evaporable liquid in first payload module&#39;s  120  immersion cooling system. Because payload module  120  has a high-capacity cooling system, payload hardware  123  housed and cooled by payload module  120  may be hardware with greater cooling needs, and having a greater power consumption level in some cases, than infrastructure hardware  113 . In some examples, payload hardware  123  may also be greater in volume than infrastructure hardware  113 . For example, where infrastructure hardware  113  occupies  12  rack units (“RU,”) payload hardware  123  may occupy 24 RU, though any other volumes and ratios between volumes of infrastructure hardware  113  and payload hardware  123  are possible. 
     Infrastructure module  110  is operatively connected to first payload module  120  in several respects in the illustrated example. A coolant supply  146  is routed through infrastructure module  110  before reaching condenser system  121  and, after passing through condenser system  121 , exiting system  100  through a coolant return  149  that leads recycles the coolant for coolant supply  146  or otherwise disposes of the coolant. The cooling fluid of coolant supply  146  can be liquid, such as, for example, water, glycol and water solutions, etc., or dielectric fluids such as fluorocarbons, or other liquids, or gas such as, for example, air, carbon dioxide, or other gases. In examples where infrastructure module  110  includes heat exchanger  111 , coolant supply  146  may pass through and act as a coolant for heat exchanger  111  before reaching and acting as a coolant for condenser system  121 . Coolant supply  146  and coolant return  149  are both part of a fluid coolant distribution system that circulates coolant through the respective internal cooling systems of modules  110 ,  120 ,  130  and system  100  as a whole. The distribution system, may be provided by a tap system, another type of building liquid supply system, or any other source of liquid or gas suitable for use as a coolant. Coolant supply  146  is at a relatively low temperature, and, because modules  110 ,  120 ,  130  transfer heat to the coolant as the coolant flows through a flow path of the distribution system, coolant return  149  is at a relatively high temperature. Downstream of coolant return  149  and upstream of coolant supply  146 , the distribution system either cools the coolant or disposes the heated coolant and acquires new coolant at a lower temperature. 
     PLC  112  is in electronic communication with condenser system  121 , humidity control system  122 , and fluid management system  125 . By this electronic connection between PLC  112 , humidity control system  122 , and fluid management system  125 , PLC  112  controls humidity control system  122  and fluid management system  125  and thereby governs first payload module&#39;s  120  immersion cooling system. In various examples, PLC  112  may be able to power the immersion cooling system on or off, adjust a temperature maintained by the immersion cooling system, adjust flow rates within the immersion cooling system, or any combination of the foregoing. The governance of first payload module&#39;s  120  immersion cooling system by PLC  112  of infrastructure module  110  can simplify maintenance and operation of the immersion cooling system. Access to an immersion cooling system can be difficult and disruptive to the operation and cooling of hardware in the immersion cooling system because such systems are usually closed to prevent the escape of vapors. Accessing PLC  112  at infrastructure module  110 , the housing of which may be a simple server cabinet or something similar, may therefore be relatively easy. 
     PLC  112  may also be in electronic communication with a management system  147 , such as a building management system or data network. The connection between PLC  112  and management system  147  enables PLC  112  and the immersion cooling system of first payload module  120  to be controlled by a remote operator or in concert with other systems. In the illustrated example, infrastructure hardware  113  and payload hardware  123  are also in electronic communication with each other, though in other examples, infrastructure hardware  113  and payload hardware  123  may have no communication with each other. 
     A power and network connection  148  may also be routed through infrastructure module  110  before reaching first payload module  120 . The power aspect of power and network connection  148  may be, for example, a building power supply, grid power supply, or battery. The network aspect of power and network connection  148  may be, for example, an internet, telephone, local area network or other electronic communication network. In the illustrated example, power is communicated between infrastructure hardware  113  and infrastructure bus bar  114 , and infrastructure bus bar  114  is connected to payload bus bar  124 . Thus, payload module  120  may receive some or all operating power for itself and for payload hardware  123  from connections to infrastructure module  110 . However, payload module  120  and payload hardware  123  may acquire power from other sources as well, and in other examples, either or both of payload module  120  and payload hardware  123  may acquire all needed power from sources other than infrastructure module  110  and infrastructure hardware  113 . 
     Systems may exist including infrastructure module  110  and only one payload module having the features of first payload module  120 . However, system  100  of the illustrated example also includes a second payload module  130 , which is the same as first payload module  120  with respect to all details of first payload module  120  described above. All connections between infrastructure module  110  and first payload module  120  also extend in parallel between infrastructure module  110  and second payload module  130  except for the flow path of coolant from coolant supply  146  and coolant return  149 . The flow path from coolant supply  146  to coolant return  149  instead passes in series through infrastructure module  110  first, then through a condenser system within second payload module  130 , and finally through condenser system  121  of first payload module  120 . First payload module  120  therefore only receives coolant that has already been used for cooling by second payload module  130 . Hardware to be cooled in each module  110 ,  120 ,  130  may therefore be chosen in view of the coolant&#39;s flow path to optimize efficiency in coolant and energy usage. For example, expenses per unit volume of coolant, per unit of heat imparted to the coolant used, and per unit of electrical power necessary to operate system  100  and the hardware cooled by system  100  may be considered in finding a most economical distribution of hardware among modules  110 ,  120 ,  130 . 
     Infrastructure module  110  may optionally be of a relatively small form factor, such as that of a typical server rack or cabinet. For example, infrastructure module  110  may have the shape and dimensions of an EIA-310 standard server rack, or at least dimensions similar enough to facilitate installation of infrastructure module  110  among such racks. 
     Payload modules  120 ,  130  may optionally be adapted for installation among typical server racks or cabinets. For example, payload modules  120 ,  130  have the same, or about the same, shape and dimensions as one, two, three, or more adjacent EIA-310 standard server racks such that the payload modules  120 ,  130  can be installed among such racks. Payload modules  120 ,  130  so configured may be installed adjacent to or near infrastructure module  110  in an area of a data center that has been set up for storing server racks. System  100  therefore enables types of hardware that might otherwise be scattered across a data center or among multiple different facilities due to their different cooling needs to be stored and operated in a single location. Further, system  100  enables cool-operating hardware that can be effectively cooled by heat exchanger  111  to be installed near to hardware that must be immersion cooled without not need immersion cooling to be installed near hardware that must be immersion cooled without the cool-operating hardware taking up space and wasting resources in an immersion cooling system. Installation of payload modules  120 ,  130  near infrastructure module  110  also facilitates access to and operation of the modules  110 ,  120 ,  130  by their owners or technicians. Installation of payload modules  120 ,  130  near infrastructure module  110  also simplifies electronic connection between infrastructure hardware  113 , payload hardware  123 , and hardware housed by second payload module  130 . 
     The presence of only a first payload module  120  and a second payload module  130  in system  100  is shown by way of example, and systems with other numbers of payload modules may be created. In some examples, second payload module  130  may be omitted altogether such that a coolant flow path extends from infrastructure module  110  directly and only to first payload module  120  before exiting system  100  through coolant return  149 . In other examples, system  100  may include any plural number of payload modules connected in series along the coolant flow path between infrastructure module  110  and first payload module  120 . All such additional modules may be connected to infrastructure module  110  for transmission of electronic communication and power in the same manner as first payload module  120  and second payload module  130 . 
       FIG.  2    illustrates a system  200  in which elements are generally alike to like numbered elements of system  100 . For example, infrastructure module  210  is the same as infrastructure module  110 , first payload module  220  is the same as first payload module  120 , second payload module  230  is the same as second payload module  130 , and so on, except for specifically illustrated or described differences. For this reason, certain numerals in  FIG.  2    may not be specifically mentioned herein. Moreover, all above described possible variations upon elements of system  100  are equally possible for elements of system  200  except to the extent they conflict with features of system  200  that differ from the features of system  100 . 
     System  200  differs from system  100  in that coolant is supplied to each module  210 ,  220 ,  230  in parallel. Thus, coolant from a first coolant supply  246   a  flows through heat exchanger  211  before exiting system  200  through a first coolant return  249   a , coolant from a second coolant supply  246   b  flows through first payload module&#39;s  220  condenser system  221  before exiting system  200  through a second coolant return  249   b , and coolant from a third coolant supply  246   c  flows through a condenser system of second payload module  230  before exiting system  200  through a third coolant return  249   c . In other examples wherein infrastructure module  210  lacks a heat exchanger  211 , infrastructure module  210  may be without any coolant supply or coolant return. 
     The presence of only first payload module  220  and second payload module  230  in the illustrated example is one configuration of system  200 , but in other examples, system  200  may omit second payload module  230 , and in yet other examples, system  200  may include any number of payload modules with independent, parallel coolant supply and return connections. 
     Similar to system  100 , system  200  enables infrastructure module  210  to be installed among one or more payload modules  220 ,  230  to provide easy access to governance of immersion cooling at PLC  212  and to store and operate hardware of different cooling needs in a single location. However, because modules  210 ,  220 ,  230  receive cooling fluid in parallel, heat generated by and removed from hardware in any one module  210 .  220 ,  230  will have little or no effect on the cooling of hardware in any other module  210 ,  220 ,  230 . The overall efficiency of system  200  will therefore be less dependent on the choice of which payload module  220 ,  230  will house and cool particular hardware than the efficiency of system  100 . 
       FIG.  3    illustrates a system  300  in which elements are generally alike to like numbered elements of systems  100  and  200 . For example, infrastructure module  310  is the same as infrastructure modules  110  and  210 , first payload module  320  is the same as first payload modules  120  and  220 , second payload  330  is the same as second payload modules  130  and  230 , and so on, except for specifically illustrated or described differences. For this reason, certain numerals in  FIG.  3    may not be specifically mentioned herein. Moreover, all above described possible variations upon elements of systems  100  and  200  are equally possible for elements of system  300  except to the extent they conflict with features of system  300  that differ from the features of systems  100  or  200 . 
     In system  300 , coolant is supplied to each payload module  320 ,  330  in parallel through infrastructure module  310 . Thus, coolant from a coolant supply  346  flows through heat exchanger  311  before splitting into separate flow paths. One of the flow paths after the split extends through condenser system  321  of first payload module  320  before exiting system  300  through a first coolant return  349   a  while another flow path after the split extends through a condenser system of second payload module  330  before exiting system  300  through a second coolant return  349   b.    
     The presence of only first payload module  320  and second payload module  330  in the illustrated example is one configuration of system  300 , but in other examples, system  300  may omit second payload module  330 , and in yet other examples, system  300  may include any number of payload modules that receive coolant in parallel with one another after the coolant has passed through heat exchanger  311  and before the coolant exits system  300  through a respective coolant return. 
     System  300  has all the capabilities that system  200  shares with system  100 . Like system  200 , system  300  is configured in a way that causes heating and cooling within any one payload module to have little, if any, effect on the temperature of coolant entering any other payload module. Routing all coolant through infrastructure module  310  first can simplify installation of system  300  in some cases, while connecting all modules in parallel as shown in system  200  may be simpler in other circumstances. Since infrastructure hardware  313  in some examples presents a relatively low heat load, cooling of payload modules  320 ,  330  may not be significantly impacted by their placement downstream of infrastructure module  310 . However, if heat exchanger  311  splits coolant into separate channels expected to have differing heat loads within heat exchanger  311  and those separate channels flow to different payload modules  320 ,  330 , the differing heat loads within heat exchanger  311  may be taken into account when choosing a payload module  320 ,  330  for specific hardware to optimize the cooling efficiency of system  300 . Otherwise, similar to system  200 , choice of payload modules  320 ,  330  for specific hardware in system  300  has relatively little effect on system&#39;s  300  cooling performance. 
       FIG.  4    illustrates a system  400  in which elements are generally alike to like numbered elements of system  300 . For example, infrastructure module  410  is the same as infrastructure module  310 , first payload module  420  is the same as first payload module  320 , second payload module  430  is the same as second payload module  330 , and so on, except for specifically illustrated or described differences. For this reason, certain numerals in  FIG.  4    may not be specifically mentioned herein. Moreover, all above described possible variations upon elements of systems  100 ,  200 , and  300  are equally possible for elements of system  400  except to the extent they conflict with features of system  400  that differ from the features of systems  100 ,  200 , or  300 . 
     In system  400 , coolant is supplied to each payload module  420 ,  430  in parallel through infrastructure module  410  in the same manner that system  300  distributes coolant to payload modules  320 ,  330  in parallel through infrastructure module  310 . Thus, coolant from a coolant supply  446  flows through heat exchanger  411  before splitting into separate flow paths, one of which extends through condenser system  421  of first payload module  420  before exiting system  400  through a first coolant return  449   a  while another flow path extends through a condenser system of second payload module  430  before exiting system  400  through a second coolant return  449   b.    
     System  400  has all the capabilities that system  300  shares with systems  100  and  200 , as well as most of the capabilities that differentiate system  300  from systems  100  and  200 . However, system  400  differs from system  300  by the location of a central fluid management system  415  within infrastructure module  410 . Central fluid management system  415  governs liquid levels in the tank of the immersion cooling system in each payload module  420 ,  430  such that the individual payload modules  420 ,  430  do not need to include a dedicated circuit or controller for governing their own liquid levels. Central fluid management system  415  is in electronic communication with PLC  412 , and may be governed by PLC  412  in a similar manner to the governance of distributed fluid management systems in systems  100 ,  200 ,  300 . Placement of central fluid management system  415  within infrastructure module  410  provides the same ease of access to central fluid management system  415  as provided for PLC  412  without occupying space in the payload modules  420 ,  430 . 
     The presence of only first payload module  420  and second payload module  430  in the illustrated example is one configuration of system  400 , but in other examples, system  400  may omit second payload module  430 , and in yet other examples, system  400  may include any number of payload modules having immersion cooling systems governed by central fluid management system  415 . 
       FIG.  5    illustrates a system  500  in which elements are generally alike to like numbered elements of systems  100 ,  200 , and  300 . For example, infrastructure module  510  is the same as infrastructure modules  110 ,  210 , and  310  and payload module  520  is the same as payload modules  120 ,  220 , and  320 , and so on, except for specifically illustrated or described differences. For this reason, certain numerals in  FIG.  5    may not be specifically mentioned herein. Moreover, all above described possible variations upon elements of systems  100 ,  200 ,  300 , and  400  are equally possible for elements of system  500  except to the extent they conflict with features of system  500  that differ from the features of systems  100 ,  200 ,  300 , and  400 . 
     System  500  includes a standalone cooler  550  that supplies coolant in series to infrastructure module  510 , then to payload module  520  in series. The coolant that leaves payload module  520  at coolant return  549  returns to standalone cooler  550  to be restored to a supply temperature and re-supplied through coolant supply  546  to infrastructure module  510 . Standalone cooler  550  is therefore connected in-line along a flow path of the coolant distribution system that extends through system  500  at a location downstream of condenser  524  and payload module  520  but upstream of heat exchanger  511  and infrastructure module  510 . 
     Rather than a building or municipal supply of fluid that may be used as a coolant, standalone cooler  550  is a self-contained cooling system for the coolant used by system  500 . Standalone cooler  550  may be, for example, a low-energy or passive cooler, such as a dry cooling tower or another type of dry cooler, meaning a cooler that can does not require a separate cooling liquid to extract heat from the coolant used for system  500 , such as heat exchangers that dissipate heat from the coolant to ambient air. Such passive or low-energy types of standalone cooler  550  are particularly useful for implementing system  500  in remote locations where power and other utilities are limited. infrastructure module  310 . 
     The foregoing modular systems  100 ,  200 ,  300 ,  400 ,  500  each present distinct variations on shared concepts, but modular systems according to other examples may combine those distinct variations in any way. For example, standalone cooler  550  could be used to deliver and cool coolant for systems having any number of payload modules and any flow path among the modules, including any of the flow paths of modular systems  100 ,  200 ,  300 ,  400 . Central fluid management system  415  may replace the separate fluid management systems of any of modular systems  100 ,  200 ,  300 ,  500 , or any variations on those modular systems. A modular system according to other examples may include any combination of payload modules connected in series with one another as shown in modular system  100 , payload modules receiving coolant that has not passed through the infrastructure module as shown in modular system  200 , and payload modules receiving coolant that has passed through the infrastructure module in parallel with other payload modules as shown in modular systems  300  and  400 . 
     As shown in  FIG.  6   , a process  1000  of housing and cooling electronic equipment with any of the systems  100 ,  200 ,  300 ,  400 ,  500  described above includes a setup phase  1010 , a storage phase  1020 , and an operation phase  1030 . The process  1000  is described below with reference to elements of system  100  by way of example, but each reference below to any element of system  100  is equally applicable to the corresponding elements of any of systems  200 ,  300 ,  400 ,  500  or any possible variations on systems  100 ,  200 ,  300 ,  400 ,  500 . 
     Setup phase  1010  includes coolant connection  1011  and module interconnection  1012 , either of which may be performed before, during, or after the other. During coolant connection  1011 , modules  110 ,  120 ,  130  are connected to an available distribution system for fluid coolant. Modules  110 ,  120 ,  130  may be connected in parallel or series and in any order. During module interconnection  1012 , modules are connected to each other electrically, electronically, or both. For example, interconnection  1012  may include establishing electrical connection between bus bars  114 ,  124 , connecting PLC  112  to humidity control system  122  and fluid management system  125 , and extending electronic connectors such as wires or cables between modules  110 ,  120 ,  130  through which computer hardware  113 ,  123  can communicate electronically with computer hardware  113 ,  123  in any other module. Establishment of fluid connections among modules  110 ,  120 ,  130  may be considered part of either or both of coolant connection  1011  and module interconnection  1012 . 
     Setup phase  1011  is followed by storage phase  1020 , which includes infrastructure installation  1021  and immersion  1022 . Either of infrastructure installation  1021  and immersion  1022  may be performed before, during, or after the other. Infrastructure installation  1021  includes placement of infrastructure hardware  113  into infrastructure module  110  so that infrastructure hardware  113  may operate on power from bus bar  114 . Immersion  1022  includes immersing payload hardware  123  into the evaporable liquid in the immersion cooling systems of payload modules  120 ,  130 . At the end of storage phase  1020 , infrastructure hardware  113  and payload hardware  123  are housed and stored within their respective modules  110 ,  120 ,  130  and are prepared to operate and be cooled appropriately. 
     Operation phase  1030  follows storage  1020  and includes cooling  1031  and computing  1032  which may be performed concurrently. Cooling  1031  includes running heat exchanger  1011  to cool infrastructure hardware  113  and running the immersion cooling system of one of, some of, or all payload modules  120 ,  130  to cool payload hardware  123 . Cooling  1031  may also include circulating coolant among modules  110 ,  120 ,  130 . Computing step  1032  includes operating infrastructure hardware  113  and payload hardware  123 . Computing  1032  may also include operation of any other computing components in any module  110 ,  120 ,  130 . Operating PLC  112  to govern the immersion cooling systems, such as by controlling humidity control system  122  and fluid management system  125 , may therefore be considered part of cooling  1031 , computing  1032 , or both. 
     Additions to and variations on process  1000  are possible. For example, setup phase  1010  may overlap or follow installation phase  1020 . Also, additional infrastructure installation  1021  and immersion  1022  may occur during or after operation phase  1030  as hardware  113 ,  123  is added or swapped out of system  100 . 
     Although the concept herein has been described with reference to particular examples, it is to be understood that these examples are merely illustrative of the principles and applications of the present concept. It is therefore to be understood that numerous modifications may be made to the illustrative examples and that other arrangements may be devised without departing from the spirit and scope of the present concept as defined by the appended claims.