APPARATUS AND SYSTEM FOR TWO-PHASE SERVER COOLING WITH SERIAL CONDENSER UNITS

Embodiments are disclosed of an information technology (IT) cooling system. The system includes an IT container having an internal volume. Inside the internal volume there is an immersion fluid region adapted to submerge one or more servers in a two-phase immersion fluid. An immersion condenser is positioned above the immersion fluid region in the internal volume. The design includes a circulation condenser. The circulation condenser is fluidly coupled to a liquid distribution manifold and a vapor return manifold that are positioned in the internal volume above the immersion tank (i.e., the immersion fluid region) and are adapted to circulate a two-phase circulation fluid. The circulation condenser is also fluidly coupled to the immersion condenser, and an external cooling fluid is pumped from the circulation condenser to the immersion condenser. The distribution manifolds are adapted to be fluidly coupled to the server liquid cooling loops.

TECHNICAL FIELD

The disclosed embodiments relate generally to information technology (IT) liquid cooling systems, but not exclusively, to an apparatus and system for two-phase server cooling using serial condenser units.

BACKGROUND

Modern data centers like cloud computing centers house enormous amounts of information technology (IT) equipment such as servers, blade servers, routers, edge servers, power supply units (PSUs), battery backup units (BBUs), etc. These individual pieces of IT equipment are typically housed in racks within the computing center, with multiple pieces of IT equipment in each rack. The racks are typically grouped into clusters within the data center.

As IT equipment has become more computationally powerful it also consumes more electricity and, as a result, generates more heat. This heat must be removed from the IT equipment to keep it operating properly. Various cooling solutions have been developed to keep up with this increasing need for heat removal. One of the solutions is immersion cooling, and which the IT equipment is itself submerged in a cooling fluid. The cooling fluid can be a single-phase or two-phase cooling fluid; in either case, heat from the IT equipment is transferred into the cooling fluid in which it is submerged. But existing two-phase immersion cooling systems have the coolant only within the IT enclosure, and current two-phase immersion cooling solutions do not sufficiently support high power density servers which include one or more high power-density chips. Such designs are inefficient and may not be a proper solution for hyperscale deployment.

DETAILED DESCRIPTION

Embodiments are described of a two-phase cooling system for use with information technology (IT) equipment in a data center or an IT container such as an IT rack. Specific details are described to provide an understanding of the embodiments, but one skilled in the relevant art will recognize that the invention can be practiced without one or more of the described details or with other methods, components, materials, etc. In some instances, well-known structures, materials, or operations are not shown or described in detail but are nonetheless encompassed within the scope of the invention.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a described feature, structure, or characteristic can be included in at least one described embodiment, so that appearances of “in one embodiment” or “in an embodiment” do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. As used in this application, directional terms such as “front,” “rear,” “top,” “bottom,” “side,” “lateral,” “longitudinal,”etc., refer to the orientations of embodiments as they are presented in the drawings, but any directional term should not be interpreted to imply or require a particular orientation of the described embodiments when in actual use.

The disclosed embodiments are systems for two-phase cooling of IT components. The disclosed embodiments use more than one type of two-phase immersion coolant for solving challenges related to high power thermal management and corresponding challenges associated with two-phase immersion cooling technologies. In addition, the disclosed embodiments enable some or all of the following benefits:Accommodate different IT enclosures and different deployment scales.Different data center architectures, both brownfield and greenfield.Scalable for different power densities.High efficiency.Efficient and accurate control.Accommodate different redundant requirements.Ease of design and implementation.Enable designing system with at least two types of immersion coolant with different boiling temperatures.More advanced two-phase thermal fluid management.

The described embodiments are cooling systems that use two or more two-phase cooling fluids with different boiling temperature to extract the heat load from high power density components more efficiently and solve challenges in designing cooling systems using two-phase coolants.

The described embodiments include a pair of two-phase cooling loops. The first two-phase cooling loop is a two-phase immersion system in which all the servers and electronics are submerged in the liquid phase of a two-phase immersion fluid. The vapor phase of the immersion coolant is cooled by an immersion condenser. The second two-phase cooling loop uses a two-phase circulation fluid different from the two-phase immersion fluid. The liquid phase of the circulation fluid is circulated through cooling devices thermally coupled to heat loads, where it is converted to the vapor phase. The resulting vapor phase is cooled by a circulation condenser. The immersion condenser and the circulation condenser are connected in series in one cooling fluid loop. In one embodiment the two-phase circulation loop is a pumped two-phase loop, but in other embodiments, the two-phase circulation loop uses gravity to drive flow of the liquid phase.

FIG.1illustrates an embodiment of an information technology (IT) cooling system100. Cooling system100combines immersion cooling with local fluid circulation to cool heat-generating electronics components. Immersion cooling is accomplished with a two-phase immersion fluid I having a liquid phase IL and a vapor phase IV, while circulation cooling is accomplished with a two-phase circulation fluid C having a liquid phase CL and a vapor phase CV. In most embodiments immersion cooling fluid I will be a dielectric fluid, meaning that it has little or no electrical conductivity. In one embodiment, immersion cooling fluid I and circulation cooling fluid C are different two-phase fluids; depending on the application, in various embodiments immersion cooling fluid I and circulation cooling fluid C will have different boiling points. In an embodiment where circulation fluid C must extract more heat than immersion fluid I, circulation fluid C will have a lower boiling point, enabling it to absorb and transfer away more heat. A third cooling fluid, external cooling fluid E, can be used to improve or speed up the transition from vapor phase to liquid phase for both two-phase cooling fluids I and C. The system is designed to minimize or prevent mixing of the immersion (I), circulation (C), and external (E) fluids.

Cooling system100includes an information technology (IT) container102that defines an internal volume. An immersion tank104in the internal volume is adapted to hold the liquid phase IL of two-phase immersion cooling fluid I. In the illustrated embodiment immersion tank104is part of the IT container and is formed by a lower portion of the internal volume of IT container202, but in other embodiments immersion tank104can be a physically separate tank within IT container102. IT container102is sealed to reduce or prevent escape of liquid phase IL and, during operation, escape of vapor phase IV. Immersion tank104can be understood as the immersion fluid region in this design—that is, the region in which servers are immersed and submerged in two-phase immersion fluid I for cooling, as further described below.

In the illustrated embodiment, one or more servers S are within the IT container102. The illustrated embodiment includes one server S, but other embodiments can have more servers than shown. Within each server S there are one or more heat-generating electronic components106, and a cooling device108is thermally coupled to the heat-generating electronic component. Cooling device108, which can be an evaporator in one embodiment, has a liquid inlet110and a vapor outlet112. Server S is submerged in liquid phase IL, and to ensure immersion cooling of the server the amount or level of liquid phase IL in immersion tank104is set so that the one or more servers S always remain fully submerged in the liquid phase.

Besides immersion tank104, three main components are positioned above immersion tank104in the interior volume of IT container102: an immersion condenser114, a liquid supply manifold116, and a vapor return manifold118. Immersion condenser114is not coupled by physical fluid connections to other components within IT container102. Liquid supply manifold116is fluidly coupled by a liquid line120to inlet110of cooling device108, and vapor return manifold118is fluidly coupled by a vapor return line122to vapor outlet112. As described below, cooling device108, liquid supply manifold116and vapor return manifold118form part of a two-phase circulation cooling loop to provide localized two-phase cooling to heat-generating component106.

Several external components outside IT container102are fluidly coupled to the components within IT container102to assist them in performing their functions. A circulation condenser124is fluidly coupled to liquid supply manifold116by a liquid supply line C1and is fluidly coupled to vapor return manifold118by vapor return line C2, so that liquid phase CL flows through C1and vapor phase CV flows through C2. A pump P2is fluidly coupled into liquid supply line C1to boost the pressure and/or flow rate of liquid phase CL flowing into and through liquid supply manifold116.

A cooling unit126is fluidly coupled to both immersion condenser114and circulation condenser124. Cooling unit126circulates external cooling fluid E through both condensers, improving their ability to condense their respective two-phase fluids. To circulate external cooling fluid E through both condensers, an external outlet114oof immersion condenser114is fluidly coupled by fluid line E1to inlet126of cooling unit126and an external outlet126oof cooling unit126is fluidly coupled by fluid line E2to an external inlet124iof circulation condenser124. A pump P1is coupled into fluid line E2to boost the flow of external cooling fluid E into circulation condenser124. Finally, an external outlet124oof circulation condenser124is then coupled by fluid line E3to an external inlet114iof immersion condenser114. In respect of the loop of cooling fluid E, the circulation condenser and immersion condenser are in series. In other embodiments pump P1can instead be coupled into fluid line E3or fluid line E1.

During operation of cooling system100, heat-generating components within servers S are cooled by both the immersion cooling loop and the circulation cooling loop. In the immersion cooling loop, heat generated by heat-generating components106within servers S is transferred to liquid phase IL of the immersion fluid I, transforming it by evaporation into vapor phase IV. Vapor phase IV rises into the space between a surface of the liquid phase IL in immersion tank104and the top of IT container202, where it enters immersion condenser114and condenses back into liquid phase IL. External cooling E from cooling unit126flows in and out of immersion condenser114, as described above, to improve the condensation rate of immersion condenser114. Under the force of gravity, liquid phase IL drops from immersion condenser114back into immersion tank104, where it will again be transformed by heat from component into vapor phase IV, thus completing the immersion cooling loop.

The circulation cooling loop operates simultaneously with the immersion cooling loop to provide enhanced and more localized cooling to heat-generating components106. The liquid phase CL of circulation cooling fluid C flows from liquid supply manifold116, through liquid supply line120and liquid inlet110, into cooling device108, where the liquid phase CL absorbs heat from heat-generating device106and is converted into vapor phase CV. Vapor phase CV then flows out of cooling device108through vapor outlet112and vapor line122to vapor return manifold118. Vapor phase CV then flows from vapor return manifold118into circulation condenser124through vapor line C2. In circulation condenser124, vapor phase CV, with the help of external cooling fluid E from cooling unit126, condenses vapor phase CV back into liquid phase CL. Liquid phase CL is then returned through liquid supply line C1, with the assistance of pump P2, from the circulation condenser to liquid supply manifold116, thus completing the circulation cooling loop. The immersion cooling loop and the circulation cooling loop are fully separated and operate independently without mixing their respective two-phase fluids. In system100the circulation loop is the main cooling system because it functions as a localized high power density thermal management system in a fully two-phase immersion environment. For this reason, external cooling fluid E is first delivered to the circulation condenser through fluid line E2before being delivered to the immersion condenser through fluid line E3.

FIG.2illustrates an embodiment of an information technology (IT) cooling system200. Cooling system200is in most respects similar to cooling system100. The primary difference between cooling systems100and200is that in cooling system200the elements are grouped and packaged differently so that the system can be modularized.

In system200, IT container202has an internal volume, and all the same elements within the internal volume of IT container102are also found within IT container202: immersion tank104, server S, immersion condenser114, liquid supply manifold116and vapor return manifold118. All of these components are positioned the same way, and have the same fluid connections among themselves, as they do in IT container102. But unlike IT container102, IT container202has pump P2positioned in the internal volume rather than outside the IT container.

In system200, the elements outside the IT container—principally circulation condenser124and cooling unit126—are grouped and packaged differently than in system100. Cooling unit126remains a separate unit, but circulation condenser124, pump P1, and parts of the fluid lines between elements are grouped together and packaged in a condenser unit204. In the illustrated embodiment, parts of fluid lines E1, E2, and E3are grouped and packaged within condenser unit204.

The fluid connections between cooling unit126and circulation condenser124and pump P1in condenser unit204, and the fluid connections between cooling unit126and elements within IT container202, remain substantially the same as in system100. Circulation condenser124is fluidly coupled to liquid supply manifold116by a liquid supply line C1and is fluidly coupled to vapor return manifold118by vapor return line C2, with liquid phase CL flowing through C1and vapor phase CV flowing through C2. Pump P2is fluidly coupled into liquid supply line C1to boost the pressure and/or flow rate of liquid phase fluid CL flowing into and through liquid supply manifold116. To circulate external cooling fluid E through both condensers, an external outlet114oof immersion condenser114is fluidly coupled by fluid line E1to inlet126is of cooling unit126; an external outlet126oof cooling unit126is fluidly coupled by fluid line E2to an external inlet124iof circulation condenser124. A pump P1is coupled into fluid line E2to boost the flow of external cooling fluid E into circulation condenser124. An external outlet124oof circulation condenser124is then coupled to an external inlet114iof immersion condenser114.

To support the modularization of components in system200, some or all of IT container202, condenser unit204, and cooling unit126include fluid interfaces to allow one unit to be fluidly coupled to another quickly and efficiently. System200includes six fluid interfaces, but other embodiments can include more or less fluid interfaces than shown. In system200, fluid interfaces #1through #4couple elements within condenser unit204to elements within IT container202, while fluid interfaces #5and #6couple elements within condenser unit204to cooling unit126. The fluid interfaces are as follows:Fluid interfaces #1and #5are both fluidly coupled in fluid line E1between external outlet114oof immersion condenser unit114and external inlet126iof the cooling unit. Fluid interface #1is positioned in fluid line E1between IT container202and condenser unit204, while fluid interface #5is positioned in fluid line E1between condenser unit204and the inlet126iof the cooling unit.Fluid interface #2is fluidly coupled in fluid line E3between external outlet124oof circulation condenser124and external inlet114iof immersion condenser114. Fluid interface #2is positioned in line E3between condenser unit204and IT container202.Fluid interface #3is fluidly coupled in fluid line C1between circulation condenser124and pump P2and liquid supply manifold116. Fluid interface #3is positioned in line C1between condenser unit204and IT container202.Fluid interface #4is fluidly coupled in fluid line C2between vapor return manifold118and circulation condenser124. Fluid interface #4is positioned in line C2between condenser unit204and IT container202.

In one embodiment the fluid interfaces can be quick connect/disconnect fluid connectors, but in other embodiments the fluid interfaces can be another type of fluid connector such as a blind mating connector. In one embodiment all the fluid interfaces can be of the same type, but in other embodiments they need not all be of the same type. And although they are individually referred to in the singular as a fluid interface, each fluid interface can include one or more fluid connectors. For instance, in one embodiment fluid interfaces #3and #4can include a single connector between the IT container202and condenser unit204, but in another embodiment these same fluid interfaces can include multiple fluid connectors—e.g., one fluid connector at IT container202and another at condenser unit204.

System200operates in substantially the same way as described above for system100, with the addition of some controls. System200includes a pressure sensor PS that is positioned in vapor return manifold118and is communicatively coupled to pumps P1and P2. With this arrangement, the amount of cooling fluid E delivered from cooling unit126to circulation condenser124, and the amount of the liquid phase CL delivered from circulation condenser124to liquid supply manifold116, can be controlled based on the vapor pressure in vapor return manifold118. In one embodiment, for instance, if the vapor pressure measured by pressure sensor PS increases, meaning that more liquid is needed at cooling device108, the speeds of pumps P1and P2can both be increased to provide more, and cooler, liquid phase CL to the liquid supply manifold116and to cooling device108. Pressure sensor PS and its communicative coupling to pumps P1and P2can also be added to system100, in which case systems100and200operate substantially the same way. In system200, the circulation loop is the main cooling system because it functions as a localized high power density thermal management system in a fully two-phase immersion environment. The main cooling system can be also understood as the one that extracts a significant amount of the heat generated by the servers. For this reason, external cooling fluid E is first delivered to the circulation condenser through fluid line E2before being delivered to the immersion condenser through fluid line E3.

FIG.3illustrates another embodiment of a two-phase cooling system300. System300is in many ways similar to system100; the primary differences are the placement of some of the components and the operation of the system. Cooling system300, like cooling system100, combines global immersion cooling with local fluid circulation to cool heat-generating electronic components. Immersion cooling is accomplished using a two-phase immersion fluid I with a liquid phase IL and a vapor phase IV, while circulation cooling is accomplished using a two-phase circulation fluid C with a liquid phase CL and a vapor phase CV. Generally, immersion cooling fluid I will be a dielectric fluid, meaning that it has little or no electrical conductivity. In one embodiment, immersion cooling fluid I and circulation cooling fluid C are different two-phase fluids. In some embodiments, circulation fluid C will have a lower boiling point than immersion cooling fluid I, enabling it to absorb and carry away more heat. A third cooling fluid, external cooling fluid E, can be used to improve the transition from vapor phase to liquid phase for both cooling fluids I and C. The system is designed to minimize or prevent mixing of fluids I, C, and E.

Cooling system300includes an information technology (IT) container302with an internal volume that includes an immersion tank104adapted to hold the liquid phase IL of two-phase immersion cooling fluid I. In the illustrated embodiment immersion tank104is formed by a lower portion of the internal volume of IT container202, but in other embodiments immersion tank104can be a physically separate tank within IT container102. IT container102is sealed to reduce or prevent escape of liquid phase IL and, during operation, escape of vapor phase IV.

In the illustrated embodiment, one or more servers S are within the IT container302. The illustrated embodiment includes one server S, but other embodiments can have more servers than shown. Within server S there are one or more heat-generating electronic components106, and a cooling device108is thermally coupled to the heat-generating electronic component. Cooling device108, which can be an evaporator in one embodiment, has a liquid inlet110and a vapor outlet112. Server S is submerged in liquid phase IL, and to ensure immersion cooling the amount or level of liquid phase IL in immersion tank104is chosen so that the one or more servers S always remain fully submerged in the liquid phase.

Besides immersion tank104, four main components are positioned above the tank in the interior volume of IT container302: an immersion condenser114, a circulation condenser124, a liquid supply manifold116, and a vapor return manifold118. In system300, then, circulation condenser124is positioned within the IT container, as opposed to system100in which it is positioned outside the IT container. Within IT container302, immersion condenser114has an external inlet114ifluidly coupled by physical fluid connection E3to external outlet124oof circulation condenser124. Liquid supply manifold116is fluidly coupled by liquid line C1to circulation condenser124, and vapor return manifold118is also fluidly coupled by vapor line C2to the circulation condenser, with liquid phase CL flowing through C1and vapor phase CV flowing through C2. Liquid supply manifold116is also fluidly coupled to inlet110of cooling device108by a liquid line120, and vapor return line122is fluidly coupled between vapor outlet112and vapor return manifold118. As described below, cooling device108, liquid supply manifold116, vapor return manifold118, and circulation condenser124form part of a two-phase circulation cooling loop to provide localized two-phase cooling to heat-generating component106.

An external cooling unit126, separate from IT container302, is fluidly coupled to both immersion condenser114and circulation condenser124to circulate external cooling fluid E through both condensers, improving their ability to condense their respective two-phase fluids. External outlet114oof immersion condenser114is fluidly coupled by fluid line E1to inlet126iof cooling unit126, and outlet126oof cooling unit126is fluidly coupled by fluid line E2to external inlet124iof circulation condenser124. As described above, immersion condenser114has an external inlet114ifluidly coupled by fluid connection E3to external outlet124oof circulation condenser124, so that fluid lines E1-E3form a loop through which fluid E flows. A pump P1is coupled into fluid line E2to boost the pressure and/or flow rate of cooling fluid E flowing into and through circulation condenser124and immersion condenser114. In other embodiments P1can instead be coupled into fluid line E3or fluid line E1.

As in system200, system300includes fluid interfaces to assist modularization. System300includes two fluid interfaces, but other embodiments can include more or less interfaces than shown. Fluid interfaces #1and #2are used to couple cooling unit126to the immersion condenser and the circulation condenser within IT container302. The fluid interfaces are as follows:Fluid interface #1is fluidly coupled in fluid line E1between external outlet114oof immersion condenser unit114and external inlet126iof the cooling unit. Fluid interface #1is positioned in fluid line E1between IT container302and cooling unit126.Fluid interface #2is fluidly coupled in fluid line E2between external outlet126oof the cooling unit and external inlet124iof circulation condenser124. Fluid interface #2is positioned in line E2downstream of pump P1between cooling unit126and IT container302.

During operation of cooling system300, heat-generating components within servers S are cooled by both the immersion cooling loop and the circulation cooling loop. In the immersion cooling loop, heat generated by heat-generating components106within servers S can be transferred to liquid phase IL of the immersion fluid I, transforming it by evaporation into vapor phase IV. Vapor phase IV rises into the space between a surface of the liquid phase IL in immersion tank104and the top of the IT container202, where it enters immersion condenser114and condenses back into liquid phase IL. External cooling fluid E from cooling unit126flows through immersion condenser114, as described above, to improve its condensation rate. By the force of gravity, liquid phase IL drops from immersion condenser114back into immersion tank104, where it will again be transformed by heat into vapor phase IV, thus completing the immersion cooling loop.

The circulation cooling loop operates simultaneously with the immersion cooling loop to provide enhanced and more localized cooling to heat-generating components106. The liquid phase CL of circulation cooling fluid C flows from liquid supply manifold116, through liquid supply line120and liquid inlet110, into cooling device108. In cooling device108the liquid phase CL absorbs heat from heat-generating device106and is converted into vapor phase CV. Vapor phase CV then flows out of cooling device108through vapor outlet112and vapor line122to vapor return manifold118. Vapor phase CV then flows from vapor return manifold118into circulation condenser124through vapor line C2. In circulation condenser124, vapor phase CV, with the help of external cooling fluid E from cooling unit126, condenses vapor phase CV back into liquid phase CL. Liquid phase CL is then returned by gravity from the circulation condenser to liquid supply a supply manifold116through liquid supply line C1, completing the circulation cooling loop. Thus, in system300the vapor phases CV and IV rise naturally to the condensers in their respective cooling loops and liquid phases IL and CL drop by gravity to the tank and the liquid supply manifold respectively.

In system300the circulation loop is the main cooling system because it functions as a localized high power density thermal management system in a fully two-phase immersion environment. For this reason, external cooling fluid E is first delivered to the circulation condenser through fluid line E2before being delivered to the immersion condenser through fluid line E3.

FIG.4illustrates another embodiment of a two-phase cooling system400. Cooling system400is in most respects similar to cooling system300. System400includes IT container302and cooling unit126; both include the same components as in system300, with the components within IT container302and cooling unit126fluidly connected in the same way. The primary difference between systems300and400is that system400includes additional fluid and control components to manage operation of the system. System400, then, operates similarly to system300, but with additional controls.

System400includes a pair of reservoirs to help manage the liquid phases of the immersion fluid and the circulation fluid. Circulation reservoir402holds the liquid phase CL of circulation fluid C and is fluidly coupled, by fluid line C3, to liquid supply manifold116. A pump P2is coupled into fluid line C3, and a control valve V1is coupled into fluid line C3downstream of pump P2. Similarly, immersion reservoir404holds the liquid phase IL of immersion fluid I and is fluidly coupled, by fluid line I1, to immersion tank104. A pump P3is coupled into fluid line I1, and a control valve V2is coupled into fluid line I1downstream of pump P3. In other embodiments circulation reservoir402and immersion reservoir404can be fluidly coupled to more than one IT container at a time, so that pumps P2and P3are also shared by more than one IT container.

A pressure sensor PS is positioned in vapor return manifold118and is communicatively coupled to pump P1and control valve V1so that the amount of circulation fluid flowing through the circulation loop can be controlled by controlling the pump speed and the open ratio of the valve. The open ratio of control valve V1is a measure of how open the valve is. In one embodiment the open ratio can have any value between 0 and 1: an open ratio of 0 means the valve is fully closed and all flow is cut off; an open ratio of 1 means the valve is fully open and fluid flows freely through it; an open ratio of 0.5 means the valve is half open; and so on.

In operation, if the vapor pressure measured by pressure sensor PS drops, meaning that more liquid phase CL is needed at cooling device108, the speed of pump P2and the open ratio of control valve V1can both be increased. An increase in the pump speed and valve open ratio results in liquid-phase fluid CL being delivered from the circulation reservoir into liquid supply manifold116at higher pressure and flow rate, thus delivering more liquid phase to cooling device108. Put differently, pump P2and control valve V1are used in a combined manner to making up lost circulation flowing through fluid lines C2and C2. In other embodiments, circulation reservoir402can be fluidly coupled to multiple IT containers302, and individual control valves V1of each IT container can provide individual control to that particular container.

IT container302cannot be perfectly sealed against exit of vapor phase IV, so the amount of liquid phase IL in immersion tank104naturally decreases over time and must occasionally be replenished. To accomplish this replenishment, a liquid level sensor L is positioned in immersion tank104and is communicatively coupled to control valve V2so that the amount of immersion fluid in immersion tank104can be kept high enough that the one or more servers S are always kept fully submerged in the liquid phase IL of the immersion fluid. Liquid level sensor L can be used to control the open ratio of valve V2. If the level of liquid IL in immersion tank104drops below the required level, the open ratio of control valve V2is increased, allowing liquid IL to flow into immersion tank104until the require liquid level is restored. Once the required liquid level is restored, the open ratio of control valve V2is decreased to slow or stop the flow of liquid IL into the tank. Put differently, pump P3and control valve V2are used in a combined manner to making up lost liquid phase IL in tank104. In other embodiments, immersion reservoir404can be fluidly coupled to multiple IT containers302, and individual control valves V2of each IT container can provide individual control to that particular IT container.

In system400the circulation loop is the main cooling system because it functions as a localized high power density thermal management system in a fully two-phase immersion environment. For this reason, external cooling fluid E is first delivered to the circulation condenser through fluid line E2before being delivered to the immersion condenser through fluid line E3. In other embodiments, the control sensor can include more advanced ML algorithm for enhanced performance in different scenarios.

Other embodiments are possible besides the ones described above. For instance:More advanced control and optimization algorithm can be integrated.The IT container can be designed in different configurations.The solution can be extended for more than two different types of two-phase immersion cooling fluid coexisting in one system.

The above description of embodiments is not intended to be exhaustive or to limit the invention to the described forms. Specific embodiments of, and examples for, the invention are described herein for illustrative purposes, but various modifications are possible.