Liquid-cooled electronics rack with immersion-cooled electronic subsystems

A liquid-cooled electronics rack comprising:

• a plurality of immersion-cooled electronic subsystems, each immersion-cooled electronic subsystem comprising:
• a housing at least partially surrounding and forming a sealed compartment about the electronic subsystem, the electronic subsystem comprising a plurality of electronic components to be cooled;
• a dielectric fluid disposed within the sealed compartment, wherein the plurality of electronic components to be cooled are at least partially immersed within the dielectric fluid;
• and
• a dielectric fluid inlet and a dielectric fluid vapor outlet in fluid communication with the sealed compartment, wherein the dielectric fluid is provided to the sealed compartment via the dielectric fluid inlet and dielectric fluid vapor egresses from the sealed compartment via the dielectric fluid vapor outlet;
• a vapor-condensing heat exchanger to facilitate condensing of the dielectric fluid vapor egressing from the sealed compartments of the plurality of immersion-cooled electronic subsystems;
• a dielectric fluid vapor return manifold coupling in fluid communication the dielectric fluid vapor outlets of the plurality of immersion-cooled electronic subsystems and the vapor-condensing heat exchanger;
• a reservoir for holding the dielectric fluid, the reservoir being disposed at a lower height than the vapor-condensing heat exchanger;
• a gravity drain line coupled to drain the dielectric fluid condensate from the vapor-condensing heat exchanger to the reservoir;
• an immersed, sub-cooling heat exchanger disposed within the reservoir for cooling the dielectric fluid;
• a dielectric fluid supply manifold coupling in fluid communication the reservoir and the dielectric fluid inlets of the plurality of immersion-cooled electronic subsystems;
• a pump disposed at an outlet of the reservoir for pumping under pressure the dielectric fluid from the reservoir to the dielectric fluid supply manifold for maintaining the dielectric fluid in a liquid state within the sealed compartments of the plurality of immersion-cooled electronic subsystems;
• and
• multiple flow restrictors associated with multiple immersion-cooled electronic subsystems of the plurality of immersion-cooled electronic subsystems, each flow restrictor of the multiple flow restrictors being associated with a respective immersion-cooled electronic subsystem of the multiple immersion-cooled electronic subsystems and being disposed in fluid communication with the dielectric fluid inlet to the sealed compartment thereof, and wherein the multiple flow restrictors facilitate balancing dielectric fluid flow from the dielectric fluid supply manifold to the multiple immersion-cooled electronic subsystems of the liquid-cooled electronics rack.

A method of facilitating cooling of a liquid-cooled electronics rack, the method comprising:

• providing a plurality of immersion-cooled electronic subsystems within the liquid-cooled electronics rack, each immersion-cooled electronic subsystem comprising:
• a housing at least partially surrounding and forming a sealed compartment about the electronic subsystem, the electronic subsystem comprising a plurality of electronic components to be cooled;
• a dielectric fluid disposed within the sealed compartment, wherein the plurality of electronic components to be cooled are at least partially immersed within the dielectric fluid;
• and
• a dielectric fluid inlet and a dielectric fluid vapor outlet in fluid communication with the sealed compartment, wherein the dielectric fluid is provided to the sealed compartment via the dielectric fluid inlet and dielectric fluid vapor egresses from the sealed compartment via the dielectric fluid vapor outlet;
• providing a vapor-condensing heat exchanger to facilitate condensing of the dielectric fluid vapor egressing from the sealed compartments of the plurality of immersion-cooled electronic subsystems, and a dielectric fluid vapor return manifold coupling in fluid communication the dielectric fluid vapor outlets of the plurality of immersion-cooled electronic subsystems and the vapor-condensing heat exchanger;
• providing a reservoir for holding the dielectric fluid, the reservoir being disposed at a lower height than the vapor-condensing heat exchanger;
• providing a gravity drain line to drain dielectric fluid condensate from the vapor-condensing heat exchanger to the reservoir;
• providing an immersed, sub-cooling heat exchanger disposed within the reservoir for cooling the dielectric fluid, the immersed, sub-cooling heat exchanger being coupled in series fluid communication with the vapor-condensing heat exchanger, wherein chilled facility coolant passes through the immersed, sub-cooling heat exchanger and then the vapor-condensing heat exchanger;
• providing a dielectric fluid supply manifold coupling in fluid communication the reservoir and the dielectric fluid inlets of the plurality of immersion-cooled electronic subsystems;
• and
• providing a pump disposed at an outlet of the reservoir for pumping under pressure the dielectric fluid from the reservoir to the dielectric fluid supply manifold for maintaining the dielectric fluid in a liquid state within the sealed compartments of the plurality of immersion-cooled electronic subsystems.