System and method for standby mode cooling of a liquid-cooled electronics rack

A cooled electronics system comprising:

• an electronics rack comprising at least one heat-generating electronics subsystem and at least one bulk power assembly providing power to the at least one heat-generating electronics subsystem;
• at least one modular cooling unit (MCU) associated with the electronics rack and configured to provide, via a system coolant loop, system coolant to the at least one heat-generating electronics subsystem and the at least one bulk power assembly for facilitating cooling thereof, wherein each MCU of the at least one MCU comprises a liquid-to-liquid heat exchanger, a facility coolant loop portion and a system coolant loop portion, and when in normal operating mode, a facility coolant loop receives chilled coolant from a source and passes at least a portion thereof through the liquid-to-liquid heat exchanger of each MCU via the facility coolant loop portion thereof, and the system coolant loop provides cooled system coolant to the at least one heat-generating electronics subsystem and the at least one bulk power assembly, and expels heat in the liquid-to-liquid heat exchanger from the at least one heat-generating electronics subsystem and the at least one bulk power assembly to the chilled coolant in the facility coolant loop;
• an air-to-liquid heat exchanger associated with the electronics rack and in fluid communication with the system coolant loop;
• at least one pump in fluid communication with the system coolant loop;
• and
• a controller coupled to the at least one pump for adjusting operation of the at least one pump to control flow rate of system coolant through the system coolant loop dependent upon a mode of operation, wherein in the normal operating mode, a first system coolant flow rate is provided through the system coolant loop to cool the at least one heat-generating electronics subsystem and the at least one bulk power assembly, and in a standby mode, a second system coolant flow rate is provided through the system coolant loop to cool the at least one bulk power assembly, wherein the first system coolant flow rate is greater than the second system coolant flow rate, and wherein in standby mode, at least a portion of the system coolant flowing through the system coolant loop passes through the air-to-liquid heat exchanger to expel heat in the air-to-liquid heat exchanger from the at least one bulk power assembly to ambient air.

A method of cooling components of an electronics rack comprising at least one heat-generating electronics subsystem and at least one bulk power assembly providing power to the at least one heat-generating electronics subsystem, the method comprising:

• employing at least one modular cooling unit (MCU) associated with the electronics rack to provide, via a system coolant loop, system coolant to the at least one heat-generating electronics subsystem and the at least one bulk power assembly for facilitating cooling thereof, wherein each MCU of the at least one MCU comprises a liquid-to-liquid heat exchanger, a facility coolant loop portion and a system coolant loop portion, and when in normal operating mode, a facility coolant loop receives chilled coolant from a source and passes at least a portion thereof through the liquid-to-liquid heat exchanger of each MCU via the facility coolant loop portion thereof, and the system coolant loop provides cooled system coolant to the at least one heat-generating electronics subsystem and the at least one bulk power assembly, and expels heat in the liquid-to-liquid heat exchanger from the at least one heat-generating electronics subsystem and the at least one bulk power assembly to the chilled coolant in the facility coolant loop;
• pumping at least a portion of the system coolant in the system coolant loop through an air-to-liquid heat exchanger associated with the electronics rack and in fluid communication with the system coolant loop;
• and
• controlling at least one pump in fluid communication with the system coolant loop to control flow rate of system coolant through the system coolant loop dependent upon a mode of operation, wherein in the normal operating mode, a first system coolant flow rate is provided through the system coolant loop to cool the at least one heat-generating electronics subsystem and the at least one bulk power assembly, and in a standby mode, a second system coolant flow rate is provided through the system coolant loop to cool the at least one bulk power assembly, wherein the first system coolant flow rate is greater than the second system coolant flow rate, and wherein in standby mode, at least a portion of the system coolant flowing through the system coolant loop passes through the air-to-liquid heat exchanger and expels heat in the air-to-liquid heat exchanger from the at least one bulk power assembly to ambient air.