Patent Description:
Servers in datacenters typically include one or more central processing units ("CPUs"), graphic processing units ("GPUs"), solid state drivers ("SSDs"), memory chips, or other suitable types of hardware components mounted on a printed circuit board as a "server blade. " CPUs, GPUs, and other hardware components of a server blade can produce heat during operation. If not adequately dissipated, the produced heat can damage, degrade, or otherwise negatively impact performance of the various components on the server blade.

Various air-cooling techniques have been used to dissipate heat produced by hardware components of servers. For example, one technique includes placing a fan in a server enclosure (e.g., top or bottom of a cabinet) to draw cooling air from outside of the server enclosure into contact with heat producing components inside the server enclosure. The cooling air can then carry away the produced heat to outside of the server enclosure. In another example, intercoolers (e.g., cooling coils) can be positioned between sections of the server enclosure. The intercoolers can remove heat from sections of the servers in the server enclosure to a cooling fluid (e.g., chilled water) and generally maintain the cooling air at a certain temperature range inside the server enclosure.

The foregoing air cooling techniques, however, have certain drawbacks. First, air cooling can be thermodynamically inefficient when compared to liquid cooling. As a heat transfer medium, air has heat transfer coefficients that is an order of magnitude below water, ethylene glycol, or other suitable types of liquid. As such, due to limitation on heat removal, densities of heat producing components on a server blade can be limited. In addition, air cooling can have long lag times in response to a control adjustment or load change. For example, when a temperature in a server enclosure exceeds a threshold, a fan can be activated to introduce additional flow of cooling air into the server enclosure to reduce the temperature. However, due to low heat transfer rates of cooling air, the temperature in the server enclosure may stay above the threshold for a long period even with the additional flow of cooling air.

Immersion cooling can address at least some of the foregoing drawbacks of air cooling. Immersion cooling generally refers to a cooling technique of placing heat producing components such as CPUs, GPUs, SSDs, memory, and/or other hardware components on a server blade submerged in a thermally conductive but dielectric liquid (referred to herein as a "dielectric coolant"). Example dielectric coolants can include mineral-oils or synthetic chemicals. Such dielectric coolants can have dielectric constants similar to that of ambient air. For example, a dielectric coolant provided by <NUM> (Electronic Liquid FC-<NUM>) has a dielectric constant of <NUM> while that of ambient air at <NUM> is about <NUM>.

During operation, a dielectric coolant can remove heat from heat producing components on a server blade via evaporation, and thus forming a two-phase fluid in a server enclosure. Vapor of the dielectric coolant (referred to herein as "dielectric vapor") can then be cooled and condensed via a coolant circulation system to remove heat from the dielectric vapor. The dielectric coolant can have much higher heat transfer coefficients than cooling air, and thus enabling much higher densities of heat producing components on a server blade. Higher densities of hardware components can result in smaller footprint for datacenters, racks, server enclosures, or other suitable types of computing facilities. The dielectric coolant can also allow fast cooldown of hardware components in the server enclosure due to control adjustment or load change. As such, long delays to lower temperatures in a server enclosure may be avoided.

One example design of an immersion cooling enclosure includes an elongated container (e.g., a <NUM>-foot long container commonly referred to as a "tank" or "immersion cooling tank") housing multiple server blades mounted vertically in the tank. Such a design has several drawbacks. First, retrofitting existing datacenters to accommodate such immersion cooling tanks may be costly. In existing datacenters, support structures holding server blades are typically much too small to accommodate <NUM>-foot immersion cooling tanks. As such, installing immersion cooling tanks may require additional and different support structures, such as concrete pad or pits.

To provide such support structures for immersion cooling tanks, however, can incur significant costs and prone to human error. For example, to accommodate an immersion cooling tank, a concrete pad may be erected in a datacenter. Accessory components such as power distribution panels, leak detectors, and cable termination panels may be installed around the concrete pad. The immersion cooling tank can then be installed on the prepared concrete pad, connected to power/signal lines, and server blades can then be installed in the tank. Once installed, a technician can charge the tank with a dielectric coolant, seal the tank, and ready the server blades for operation. As such, the installation of the tank involves multiple different operations that are performed in a prescribed sequence. The complexity of the multiple operations can thus incur high costs of installation and prone to human error.

In addition, the tank design for immersion cooling can incur high operating costs due to significant loss of the dielectric coolant due to leakage, pressure control, maintenance, or other reasons. For example, pressure inside the tank may exceed a threshold during operation. To reduce the pressure, a portion of the dielectric vapor may be purged from the tank. In another example, when one of the server blades in the tank fails or require maintenance, a technician may need to open the tank housing all of the server blades to replace the failed server blade, and thus causing excess loss of the dielectric coolant. In addition, current datacenters can have relatively high air velocity due to utilization of air cooling. The high air velocity can further exacerbate the loss of the dielectric coolant due to leakage, pressure control, maintenance, or other reasons.

Several embodiments of the disclosed technology can address at least some of the drawbacks of immersion cooling tanks by implementing a self-contained server assembly with an immersion cooling enclosure sized and shaped to fit into a rack, drawer, cabinet, or other suitable types of air-cooling support structure. In one embodiment, the immersion cooling enclosure can be configured to accommodate a single server blade. In another embodiment, the immersion cooling enclosure can be configured to accommodate two or more server blades juxtaposed or in other suitable arrangement related to one another.

In certain implementations, the immersion cooling enclosure can include a polyhedron or cuboid shape having a top wall, a bottom wall, and sidewalls between the top and bottom walls around an interior space. The sidewalls of the immersion cooling enclosure can have a height, width, and/or depth selected to fit into existing rack, drawer, or other suitable types of support structures. In other implementations, the immersion cooling enclosure can also have trapezohedron or other suitable shapes.

In one embodiment, a server blade can be mounted on a portion of the bottom wall in the interior space of the immersion cooling enclosure. The server blade includes a printed circuit board ("PCB") carrying one or more CPUs, GPUs, SSDs, memory chips, or other suitable types of hardware components. The PCB and the hardware components carried on the PCB are submerged in a dielectric coolant inside the immersion cooling enclosure. The PCB of the server blade can be oriented generally perpendicular to gravity when installed into an existing rack, drawer, or other suitable types of support structures. A distance between the top wall and the bottom wall (referred to as "spacing") can be just sufficient to accommodate a height of the PCB and other components carried thereon. For example, the spacing can be about <NUM>% of a largest height of the components on the PCB extending from the bottom wall toward the top wall. In other examples, the spacing can be <NUM>%, <NUM>%, <NUM>%, or other suitable values not exceeding <NUM>%, <NUM>%, or <NUM>%.

The self-contained server assembly includes a condenser assembly inside the immersion cooling enclosure and proximate to the PCB. The condenser assembly includes a vapor inlet and a liquid outlet at a first end proximate the PCB and a coolant inlet and a coolant outlet at a second end opposite the first end. The condenser assembly also includes a condenser coil at least partially extending between the first end and the second end. During operation, hardware components on the PCB can produce heat. The dielectric coolant submerging the PCB can absorb the produced heat and at least partially evaporate as a dielectric vapor. The condenser assembly can then draw the dielectric vapor through the vapor inlet and toward the cooling coil via a fan, natural convection, diffusion, or other suitable mechanisms. The coolant (e.g., cooling water or chilled water) passing through the cooling coil can then remove heat from the dielectric vapor and condense the dielectric vapor back into a liquid form. The condensed dielectric coolant can then be returned to the PCB through the liquid outlet via gravity, a pump, or other suitable means. As such, the condenser assembly can facilitate operation of various hardware components on the PCB by removing heat from the hardware components to the circulating coolant.

In certain implementation, the self-contained server assembly can also include an air passage above the top wall and a coolant supply assembly in fluid communication with a cooling air via the air passage. In one embodiment, the air passage can include an air duct above the top wall with a cooling air inlet configured to receive cooling air and a cooling air outlet configured to exhaust the cooling air to outside of the immersion cooling enclosure. In another embodiment, the air passage includes an opening on a portion of the top wall above the coolant supply assembly instead of the air duct. The opening is configured to receive the cooling air passing above the immersion cooling enclosure and provide the received cooling air to the coolant supply assembly. In further embodiments not covered by the claims, the air passage may be omitted, and a coolant supply assembly can be configured to provide the coolant to multiple self-contained server assemblies. In such embodiments, the coolant inlet and coolant outlet of the self-contained server assembly may be configured to be coupled to corresponding connectors on a coolant manifold via compression fitting, friction fitting or other suitable fitting techniques.

In certain implementations, the coolant supply assembly can include a circulating pump, a reservoir, a heat exchanger, and an air mover proximate the second end of the condenser assembly. The reservoir can include a container that is configured to store a suitable amount of the coolant (e.g., cooling water). The circulating pump can include a screw pump, a diaphragm pump, or other suitable types of pump configured to circulate the coolant from the reservoir to the cooling coil of the condenser assembly. The heat exchanger is configured to transfer heat from the coolant to the cooling air received via the air passage. As such, a temperature of the coolant may be reduced while the heated cooling air may be exhausted to outside of the immersion cooling enclosure via the air mover, natural convection, or other suitable mechanisms. In other embodiments, the heat exchanger can be configured to transfer heat from the coolant to chilled water, cooling water, or other suitable heat transfer media.

In certain embodiments, the self-contained server assembly can also include a dielectric coolant supply assembly having a reservoir pre-charged with a suitable amount of the dielectric coolant. During installation, upon installing the immersion cooling enclosure into a support structure, a valve between the dielectric coolant reservoir and the PCB can be actuated to allow a target amount of the pre-charged dielectric coolant to be released onto the PCB to submerge various hardware components on the PCB. As such, complex operations to charge the dielectric coolant during installation may be eliminated. In some embodiments, the self-contained server assembly can also include a level sensor (e.g., a float) that is configured to measure and control a fluid level of the dielectric coolant on the PCB. When the level sensor detects a level below a threshold, the level sensor and/or other suitable control elements may actuate the valve to introduce additional dielectric coolant onto the PCB. Thus, a target level of the dielectric coolant may be maintained in the immersion cooling enclosure. In other embodiments, the level sensor may be omitted, and the dielectric coolant may be metered onto the PCB at a preset rate.

In additional embodiments, the self-contained server assembly can further include an inert gas assembly having a gas reservoir that is configured to contain nitrogen, argon, or other suitable types of inert gas and a pressure controller configured to maintain a suitable pressure level inside the immersion cooling enclosure. During operation, the pressure controller can monitor a pressure level inside the immersion cooling enclosure. When the pressure controller detects a pressure level below a threshold, the pressure controller can be configured to introduce additional inert gas from the gas reservoir into the immersion cooling enclosure. As such, the immersion cooling enclosure can be pressurized with the inert gas in order to reduce a rate of loss of the dielectric vapor. In further embodiments, the self-contained server assembly can also include a membrane around at least a portion of the internal space of the immersion cooling enclosure. The membrane can be configured to allow air and/or the inert gas to pass through but not the dielectric vapor, and thus facilitating reduction of loss of the dielectric coolant from the immersion cooling enclosure.

Several embodiments of the disclosed technology can enable fast deployment of immersion cooled servers in existing datacenters. For example, by including the condenser assembly, the dielectric coolant supply assembly, and optionally the inert gas assembly in a single immersion cooling enclosure, complex field operations such as purging and/or charging the dielectric coolant can be avoided. The immersion cooling enclosure can also allow hybrid cooling solutions by incorporating a self-contained server assembly into a support structure with air-cooled enclosures. Also, pressure control, fluid expansion, and dielectric coolant condensing can all be server-level serviceable, and thus reducing large scale downtime. In contrast, when one server blade fails in an immersion cooling tank, other server blades may be shut down before the failed server blade can be serviced. In addition, the self-contained server assembly can be configured to contain a small volume of the dielectric coolant. As such, risks of excessive pressure buildup can be at least reduced when compared to larger and deeper immersion cooling tanks.

Certain embodiments of computing facilities, systems, devices, components, modules, and processes for rack mountable self-contained server assemblies are described below. In the following description, specific details of components are included to provide a thorough understanding of certain embodiments of the disclosed technology. A person skilled in the relevant art can also understand that the disclosed technology may have additional embodiments or may be practiced without several of the details of the embodiments described below with reference to <FIG>.

As used herein, the term an "immersion server enclosure" generally refers to a housing configured to accommodate a server, a server blade, or other suitable types of computing device submerged in a dielectric coolant inside the housing during operation of the server. A "dielectric coolant" generally refers to a liquid that is thermally conductive but dielectric. Example dielectric coolants can include mineral-oils or synthetic chemicals. Such a dielectric coolant can have a dielectric constant that is generally similar to that of ambient air (e.g., within <NUM>%). For example, a dielectric coolant provided by <NUM> (Electronic Liquid FC-<NUM>) has a dielectric constant of <NUM> while that of ambient air at <NUM> is about <NUM>. In certain implementations, a dielectric coolant can have a boiling point low enough to absorb heat from operating electronic components (e.g., CPUs, GPUs, etc.). For instance, Electronic Liquid FC-<NUM> provided by <NUM> has a boiling point of <NUM> at <NUM> atmosphere pressure.

Immersion cooling of servers can have many advantages when compared to air cooling. For example, immersion cooling can be more thermodynamically efficient due to higher heat transfer coefficients. However, current designs of tank-type enclosures may not be suitable for retrofitting existing datacenters or other suitable computing facilities. For example, one tank-type design includes an elongated container housing multiple server blades in the container. Retrofitting tank-type enclosures into support structures of an existing datacenter may be difficult and costly. In addition, such a tank-type design can incur high operating costs due to loss of a dielectric coolant used in the container due to leakage, pressure control, maintenance, or other reasons during operation.

Several embodiments of the disclosed technology can address at least some of the drawbacks of the tank-type design by implementing a server-level self-contained immersion cooling server assembly. An immersion cooling enclosure includes a condenser assembly and it can include, a dielectric coolant assembly pre-charged with a dielectric coolant, and an optional inert gas assembly containing an inert gas. As such, facilities that support immersion cooling can all be included in the immersion cooling enclosure to reduce costs of field erection and installation. In addition, pressure control, fluid expansion, and dielectric coolant condensing can all be server-level serviceable, and thus reducing large scale downtime, as described in more detail below with reference to <FIG>.

<FIG> is a schematic diagram of a computing facility <NUM> having one or more self-contained server assemblies <NUM> with immersion cooling enclosures <NUM> configured in accordance with embodiments of the disclosed technology. As shown in <FIG>, the computing facility <NUM> can include a controlled environment <NUM> (e.g., a room) housing a support structure <NUM> in which multiple server assemblies <NUM> can be installed. The computing facility <NUM> can also include a circulation fan <NUM> and a cooling tower <NUM> operatively coupled to the server assemblies <NUM>. Even though only one support structure <NUM> is shown in <FIG> for illustration purposes, in other embodiments, the computing facility <NUM> can include multiple support structures <NUM> (not shown), multiple groups of support structures <NUM>, and/or other suitable components arranged in series, in parallel, or in other suitable configurations.

The support structure <NUM> can include any suitable types of structures in which the server assemblies <NUM> can be installed. In one example, the support structure <NUM> can include a rack, e.g., a <NUM>-inch for mounting multiple servers provided by Dell Corporation of Austin, Texas. In another example, the support structure <NUM> can include a drawer, a shelf, a cabinet, or other suitable types of frame. Though not shown in <FIG>, in certain implementations, the support structure <NUM> can also house a fan, one or more intercoolers, and/or other suitable mechanical/electrical components. In other implementations, the support structure <NUM> can also house a coolant supply assembly <NUM>, as described in more detail below with reference to <FIG>.

As shown in <FIG>, the support structure <NUM> is configured to support multiple server assemblies <NUM> with both immersion-cooled and air-cooled server assemblies. For example, server assemblies <NUM>' can be configured as air cooled by including an enclosure with air inlets, multiple air passages, and air outlets (not shown) that allow the cooling air from the circulation fan <NUM> to flow past the various hardware components on the server blade <NUM>. As such, heat produced by the hardware components may be removed by the cooling air before the cooling air is exhausted via the air outlet 101b.

One or more of the server assemblies <NUM> can also be configured as immersion-cooled by individually including a server or server blade <NUM> (shown as a black rectangle) submerged in a dielectric coolant <NUM> in an immersion cooling enclosure <NUM>. Though not shown in <FIG>, the immersion cooling enclosure <NUM> can include a condenser assembly <NUM>, a dielectric coolant assembly <NUM>, and an optional inert gas assembly <NUM> (shown in <FIG>) operatively coupled to the server blade <NUM> to facilitate immersion cooling of various hardware components on the server blade <NUM>. Example configurations of the immersion cooling enclosure <NUM> are described in more detail below with reference to <FIG>.

The circulation fan <NUM> can be configured to provide cooing air to the controlled environment <NUM> via an air inlet 101a. For example, the circulation fan <NUM> can be configured to force cooling air into the controlled environment <NUM>, flow past the server assemblies <NUM> in the support structure <NUM> to carry away produced heat from the server assemblies <NUM>, and exhaust the cooling air carrying the produced heat to the cooling tower <NUM> as cooling air return via an air outlet 101b. The circulation fan <NUM> can include a centrifugal, a piston, or other suitable types of fan or compressor. Though particular configuration for cooling air circulation and cooling is shown in <FIG>, in other embodiments, the computing facility <NUM> can also include additional and/or different components. For example, the computing facility <NUM> can include a chiller, one or more heat exchangers (not shown), and/or other suitable mechanical components for removing heat from the cooling air return.

In operation, components of the server blades <NUM> in the individual server assemblies <NUM> can consume power from a power source (not shown, e.g., an electrical grid) to execute suitable instructions to provide desired computing services. The dielectric coolant <NUM> can absorb the heat produced by the components during operation and eject the absorb heat into the cooling air flowing past the server assemblies <NUM>. The dielectric coolant <NUM> absorbs the heat produced by the servers via phase transition, i.e., evaporating a portion of the dielectric coolant into a vapor. The evaporated dielectric coolant <NUM> is then cooled by the cooling air using an air-cooled condenser assembly <NUM> (shown in <FIG>) and condensed into a liquid form. The condensed dielectric coolant <NUM> can then be recirculated to the server blades <NUM> via gravity or other suitable means. In other embodiments not covered by the claims, the dielectric coolant <NUM> can absorb the heat without a phase change. The circulation fan <NUM> then forwards the heated cooling air to the cooling tower <NUM> for discarding the heat to a heat sink (e.g., the atmosphere). The cooling air can then be circulated back to the server assemblies <NUM> by the circulation fan <NUM>.

Though the self-contained server assembly <NUM> described above with reference to <FIG> includes an individual air-cooled condenser assembly <NUM>, in other embodiments not covered by the claims, the condenser assembly <NUM> can be configured to receive a coolant (e.g., cooling water) from a source external to the immersion cooling enclosure <NUM>. For example, as shown in <FIG>, the support structure <NUM> can house a coolant supply assembly <NUM> configured to provide a coolant such as cooling water to the immersion cooling enclosures <NUM> via a supply manifold 112a and a return manifold 112b. During operation, the coolant supply assembly <NUM> can be configured to provide the coolant to the condenser assembly <NUM> in the individual immersion cooling enclosures <NUM> via the supply manifold 112a to remove heat from the dielectric coolant <NUM>. The cooling water with the removed heat can then be returned to the coolant supply assembly <NUM> via the return manifold 112b. The coolant supply assembly <NUM> can then be configured to eject the removed heat from the cooling water to the cooling air in the controlled environment <NUM> or to other suitable heat sinks. Example components of the coolant supply assembly <NUM> are described in more detail below with reference to <FIG> and <FIG>.

<FIG> is an exploded perspective view of an example immersion cooling enclosure <NUM> suitable for the computing facility of <FIG> in accordance with embodiments of the disclosed technology. As shown in <FIG>, the immersion cooling enclosure <NUM> can include a top wall <NUM>, a bottom wall <NUM> opposite the top wall <NUM>, and multiple sidewalls <NUM> (shown as first, second, third, and fourth sidewalls 124a-124d, respectively) between the top wall <NUM> and the bottom wall <NUM>. As shown in <FIG>, the top wall <NUM>, the bottom wall <NUM>, and the sidewalls <NUM> can form a housing having an interior space <NUM> in which a dielectric coolant <NUM> (shown in <FIG>) can be contained. The bottom wall <NUM> can also be configured to mount a server blade <NUM> having a printed circuit board or PCB <NUM> carrying one or more heat producing components <NUM>. As used herein, the term "heat producing components" can include any electronic components that produce heat during operation. Examples of heat producing components <NUM> can include CPUs, GPUs, SSDs, memory chips, etc..

As shown in <FIG>, the immersion cooling enclosure <NUM> also includes a condenser assembly <NUM>, a dielectric coolant assembly <NUM>, and an optional inert gas assembly <NUM> housed in the interior space <NUM> of the immersion cooling enclosure <NUM>. Each of the condenser assembly <NUM>, dielectric coolant assembly <NUM>, and optional inert gas assembly <NUM> can include a corresponding housing with suitable inlets, outlets, ports, or other suitable openings in fluid communication with the interior space <NUM>. The condenser assembly includes a vapor inlet <NUM> and a liquid outlet <NUM> (shown in <FIG>). The dielectric coolant assembly <NUM> can include a coolant port <NUM> (shown in <FIG>). The inert gas assembly <NUM> can include a gas port <NUM> (shown in <FIG>). In other examples, the foregoing assemblies <NUM>, <NUM>, and <NUM> can include other suitable types of ports or components, as described in more detail below with reference to <FIG> and <FIG>.

The condenser assembly <NUM> is configured to remove heat from and condense a vapor of the dielectric coolant <NUM> in the interior space <NUM> into a liquid form. The condensed dielectric coolant can then be returned to submerge the heat producing component <NUM> on the PCB <NUM>. The dielectric coolant assembly <NUM> can be configured to be pre-charged with a certain amount of the dielectric coolant <NUM>. During installation, a portion of the pre-charged dielectric coolant can be released into the interior space <NUM> to submerge the heat producing components <NUM>. During operation, the immersion cooling enclosure <NUM> can also include a level controller that is configured to adjust a liquid level of the dielectric coolant <NUM> in the interior space <NUM> by controllably releasing additional dielectric coolant <NUM> into the interior space <NUM>. As such, a target liquid level in the immersion cooling enclosure <NUM> may be maintained. The inert gas assembly <NUM> can be configured to provide an inert gas (e.g., nitrogen or argon) into the interior space <NUM> as blanketing against loss of vaporized dielectric coolant <NUM>. In certain embodiments, the immersion cooling enclosure <NUM> can also include a pressure controller that is configured to controllably release an amount of the inert gas from the inert gas assembly <NUM> to maintain a target pressure in the interior space <NUM>. In further embodiments, the inert gas assembly <NUM> may be omitted in part or in whole. Example components of the condenser assembly <NUM>, dielectric coolant assembly <NUM>, and the inert gas assembly <NUM> are described in more detail below with reference to <FIG> and <FIG>.

<FIG> and <FIG> are schematic cross-sectional views of a self-contained server assembly <NUM> during certain stages of operation in accordance with additional embodiments of the disclosed technology. As shown in <FIG>, the printed circuit board <NUM> can be mounted directly to the bottom wall <NUM> of the immersion cooling enclosure <NUM> via adhesives, fasteners, pressure fitting, or other suitable mounting techniques. The heat producing components <NUM> are carried on the printed circuit board <NUM> and can have different heights extending from the bottom wall <NUM> toward the top wall <NUM>. For example, the heat producing component <NUM>' can have a height h that is largest among all the heat producing components <NUM>. In accordance with embodiments of the disclosed technology, the printed circuit board <NUM> can be oriented generally perpendicular (e.g., within +/-<NUM>°) to gravity when installed into the support structure <NUM>. A distance between the top wall and the bottom wall (referred to as "spacing") can be just sufficient to accommodate the largest height h of the heat producing component carried on the printed circuit board <NUM>. For example, the spacing can be about <NUM>% of a largest height h extending from the bottom wall toward the top wall. In other examples, the spacing can be <NUM>%, <NUM>%, <NUM>%, or other suitable values not exceeding <NUM>%, <NUM>%, or <NUM>%. In <FIG> and <FIG>, the spacing is exaggerated to illustrate various aspects of the disclosed technology.

Also shown in <FIG>, the server assembly <NUM> has a vapor gap <NUM> above the dielectric coolant <NUM>. In other implementations not covered by the claims, the server assembly <NUM> may not have the vapor gap <NUM>. Instead, the immersion cooling enclosure <NUM> can be substantially filled with the dielectric coolant <NUM> such that the dielectric coolant <NUM> is in contact with both the top wall <NUM> and the bottom wall <NUM>. During operation, the heat producing components <NUM> can consume power to execute instructions to provide suitable computing services. The dielectric coolant <NUM> absorbs the produced heat by evaporating a portion of the dielectric coolant <NUM> into a dielectric vapor <NUM>. As such, the dielectric coolant <NUM> becomes a two-phase fluid having a liquid phase <NUM> and a vapor phase, i.e., the dielectric vapor <NUM> (represented in Figure 3A as bubbles). As shown in <FIG>, the dielectric vapor <NUM> can rise toward the vapor gap <NUM> and come in contact with the condenser assembly <NUM>.

As shown in <FIG>, the condenser assembly <NUM> includes a vapor inlet <NUM> and a liquid outlet <NUM> at a first end proximate the server blade <NUM> and a coolant supply assembly <NUM> proximate to a second end opposite the first end. In the illustrated embodiment, the condenser assembly <NUM> can include an air mover <NUM> proximate the vapor inlet <NUM> and a condenser coil <NUM> that is configured to receive a coolant from the coolant supply assembly <NUM>. The air mover <NUM> can include a fan or other suitable types of device configured to draw or otherwise induce the dielectric vapor <NUM> to enter the condenser assembly <NUM> via the vapor inlet <NUM>. Upon contact with the condenser coil <NUM>, heat can be removed from the dielectric vapor <NUM> to the coolant received from the coolant supply assembly <NUM>. As such, the dielectric vapor <NUM> is condensed into a liquid form. The condensed dielectric coolant <NUM> can then be returned to the liquid phase <NUM> of the dielectric coolant <NUM> via the liquid outlet <NUM>.

Also shown in <FIG>, the coolant supply assembly <NUM> includes a coolant pump <NUM>, a coolant reservoir <NUM>, and a heat exchanger <NUM> operatively coupled to one another. The coolant pump <NUM> can include a screw, piston, or other suitable types of pump configured to circulate the coolant from the coolant reservoir <NUM> to the condenser coil <NUM>. The heat exchanger <NUM> can include a tube-in-shell, plate-and-frame, or other suitable types of heat exchanger configured to remove heat from the coolant returning from the condenser coil <NUM> to the cooling air. In the illustrated embodiment, the immersion cooling enclosure <NUM> can also include an air duct <NUM> above the top wall <NUM> and an air opening <NUM> on the top wall <NUM>. The air opening <NUM> is configured to allow the cooling air received by the air duct <NUM> to be diverted or otherwise provided to be in contact with the heat exchanger <NUM> of the coolant supply assembly <NUM>. In other embodiments, the air duct <NUM> may be omitted. Instead, the cooling air may be received via the air opening <NUM> as the cooling air flows between the server assemblies <NUM> in the support structure <NUM> (<FIG>). In further embodiments, the cooing air may be provided to the heat exchanger <NUM> via an additional air mover (not shown) or via other suitable techniques.

As shown in <FIG>, the dielectric coolant assembly <NUM> can be in fluid communication with the interior space <NUM> hosting the server blade <NUM> via a coolant port <NUM>. In the illustrated embodiment, the dielectric coolant assembly <NUM> includes a dielectric coolant reservoir <NUM> that is pre-charged dielectric coolant <NUM> and in fluid communication with the coolant port <NUM> via a control valve <NUM>. The control valve <NUM> can include a diaphragm, ball, or other suitable types of valve with suitable actuators, limit switches, position switches, or other suitable components. During installation, upon installing the immersion cooling enclosure <NUM> into the support structure <NUM>, the control valve <NUM> between the dielectric coolant reservoir <NUM> and the coolant port <NUM> can be actuated to allow a target amount of the pre-charged dielectric coolant <NUM> to be released onto the printed circuit board <NUM> to submerge various heat producing components <NUM>. As such, complex operations to charge the dielectric coolant <NUM> during installation may be eliminated.

In certain embodiments, the immersion cooling enclosure <NUM> can also include a level sensor <NUM> (e.g., a float) operatively coupled to a level controller <NUM> that is configured to measure and control a liquid level of the dielectric coolant <NUM> on top of the printed circuit board <NUM>. When the level sensor <NUM> detects a liquid level below a threshold, the level controller <NUM> may actuate the control valve <NUM> to introduce additional dielectric coolant <NUM> from the dielectric coolant reservoir <NUM> onto the printed circuit board <NUM>. Thus, a target level of the dielectric coolant <NUM> may be maintained in the immersion cooling enclosure <NUM>. In other embodiments, the level sensor <NUM> and/or the level controller <NUM> may be omitted, and the dielectric coolant <NUM> may be metered from the dielectric coolant reservoir <NUM> onto the printed circuit board <NUM> at a preset rate.

As shown in <FIG>, in additional embodiments, the immersion cooling enclosure <NUM> can further include an inert gas assembly <NUM> having a gas reservoir <NUM> that is configured to contain nitrogen, argon, or other suitable types of inert gas <NUM>, a pressure control valve <NUM>, a pressure sensor <NUM>, and a pressure controller <NUM> configured to maintain a suitable pressure level in the vapor gap <NUM> inside the immersion cooling enclosure <NUM>. The pressure control valve <NUM> can include a diaphragm, butterfly, or other suitable types of valve that interconnect the gas reservoir <NUM> to the vapor gap <NUM> via a gas port <NUM>. The pressure sensor <NUM> can include a pressure transmitter configured to measure a pressure in the vapor gap <NUM>. The pressure controller <NUM> can include a single-loop or other suitable types of pressure controller.

During operation, the pressure controller <NUM> can monitor a pressure level inside the immersion cooling enclosure <NUM> via the pressure sensor <NUM>. When the pressure controller <NUM> detects a pressure level below a threshold, the pressure controller <NUM> can be configured to introduce additional inert gas <NUM> (represented as dark circles) from the gas reservoir <NUM> into the vapor gap <NUM> of immersion cooling enclosure <NUM> via the gas port <NUM>. As such, the immersion cooling enclosure <NUM> can be pressurized with the inert gas <NUM> in order to reduce a rate of loss of the dielectric vapor <NUM>. In further embodiments, the immersion cooling enclosure <NUM> can also include a membrane (not shown) around at least a portion of the internal space <NUM> of the immersion cooling enclosure <NUM>. The membrane can be configured to allow air and/or the inert gas <NUM> to pass through but not the dielectric vapor <NUM>, and thus facilitating reduction of loss of the dielectric coolant <NUM> from the immersion cooling enclosure <NUM>.

<FIG> illustrates additional embodiments, said embodiments not being covered by the claims, of the immersion cooling enclosure <NUM> in which a coolant supply assembly <NUM> is configured to provide a coolant such as cooling water to multiple immersion cooling enclosures <NUM> via a supply manifold 112a and a return manifold 112b. As shown in <FIG>, the condenser coil <NUM> can be coupled to the supply manifold 122a and the return manifold 122b via supply and return connectors 149a and 149b, respectively. In one embodiment, the condenser coil <NUM> can be coupled to the supply and return connectors 149a and 149b via compression fitting. In other embodiments, the condenser coil <NUM> can be coupled to the supply and return connectors 149a and 149b via friction fitting or other suitable fitting techniques.

During operation, the coolant supply assembly <NUM> can be configured to provide the coolant to the condenser assembly <NUM> in the individual immersion cooling enclosures <NUM> via the supply manifold 112a to remove heat from the dielectric coolant <NUM>. The cooling water with the removed heat can then be returned to the coolant supply assembly <NUM> via the return manifold 112b. The coolant supply assembly <NUM> can then be configured to eject the removed heat from the cooling water to the cooling air in the controlled environment <NUM> or to other suitable heat sinks.

<FIG> is a flowchart illustrating a process of maintaining a server housed in an example immersion cooling enclosure <NUM> configured in accordance with embodiments of the disclosed technology. As shown in <FIG>, the process <NUM> can include detecting removal of power from the server housed in the immersion cooling enclosure <NUM> at stage <NUM>. The process <NUM> can then include purging (e.g., with nitrogen) the dielectric coolant from the immersion cooling enclosure <NUM> at stage <NUM>. In certain embodiments, purging the dielectric coolant can include actuating the pressure control valve <NUM> (<FIG>). In other embodiments, purging the dielectric coolant can include introducing an inert gas from an external source. Upon completion of purging the immersion cooing enclosure <NUM>, the process <NUM> can include allowing an operator to open the immersion cooling enclosure <NUM> and perform various suitable operations, such as replacing components of the server. The process <NUM> can then include refilling the enclosure before power can be applied to the server at stage <NUM>.

Claim 1:
A computer system, comprising:
a support structure (<NUM>) comprising an air inlet and an air outlet;
a first air-cooled server assembly (<NUM>') housed in the support structure, the first air-cooled assembly (<NUM>) having a first server blade (<NUM>) and a first enclosure (<NUM>) configured to receive cooling air that removes heat from heat producing components (<NUM>) on the first server blade (<NUM>); and
a second immersion-cooled server assembly (<NUM>) housed in the support structure with the first air-cooled server assembly (<NUM>'), the second immersion-cooled server assembly (<NUM>) having a second enclosure (<NUM>) housing:
a second server blade (<NUM>) having a printed circuit board (<NUM>) carrying one or more heat producing components (<NUM>);
a dielectric coolant (<NUM>) in the interior space (<NUM>) of the enclosure (<NUM>) and submerging the heat producing components (<NUM>) on the PCB (<NUM>); and
a condenser assembly (<NUM>) in the interior space (<NUM>) of the enclosure (<NUM>) the condenser assembly (<NUM>) having:
a vapor inlet (<NUM>) and a liquid outlet (<NUM>) proximate the PCB (<NUM>) of the server blade (<NUM>);
a condenser coil (<NUM>) in fluid communication with a vapor gap in the interior space (<NUM>) via the vapor inlet (<NUM>), the condenser coil (<NUM>) being configured to receive a coolant that removes heat from a vapor of the dielectric coolant (<NUM>) in the vapor gap and condenses the vapor into a liquid to be returned to the heat producing components (<NUM>) mounted on the PCB (<NUM>) via the liquid outlet (<NUM>) and a heat exchanger (<NUM>) in fluid communication with the cooling air received via the air inlet of the support structure, the heat exchanger being configured to receive the coolant with the removed heat from the condenser coil (<NUM>) and transfer the removed heat from the coolant to the cooling air before exhausting the cooling air via the air outlet.