Fluid-cooled data centres without air conditioning, and methods for operating same

A method for operating a data centre, the data centre comprising:

• a building for housing a multiplicity of racks, each rack being an open rack housing IT equipment wherein input air from the building enters a front side of the rack, each rack comprising a heat exchanger to transfer heat generated by the IT equipment to a fluid coolant, said heat exchanger located at a back side of the rack, wherein the IT equipment includes at least one fan to cool parts of the IT equipment and to create a heated air flow in the rack towards the heat exchanger located at the back side of the rack;
• and
• at least one first cooling circuit to supply the heat exchanger with the fluid coolant and to convey heated fluid coolant away from the heat exchanger, the at least one first cooling circuit coupled to a cooling source outside of the building housing the multiplicity of racks,
• the method comprising:
• A) providing the fluid coolant in the at least one first cooling circuit such that an input flow of the fluid coolant entering the heat exchanger has a first temperature of 1 degree Kelvin to 5 degrees Kelvin below a second temperature of a return flow of the heated fluid coolant exiting the heat exchanger;
• B) controlling the input flow and the return flow within the at least one first cooling circuit to maintain the first temperature of the input flow of the fluid coolant;
• and
• C) conveying the heated fluid coolant exiting the heat exchanger to the cooling source to cool the heated fluid coolant to less than or equal to the first temperature of the input flow of the fluid coolant, and returning the fluid coolant to the at least one first cooling circuit,
• wherein:
• an input temperature of the input air from the building entering the front side of the rack is between 0 degrees Kelvin and 2 degrees Kelvin higher than the second temperature of the return flow of the heated fluid coolant exiting the heat exchanger and flowing in the first cooling circuit.