System for cooling server boards in a data center

A cooling system for cooling a plurality of server boards located inside an enclosure, the system comprising:

• at least one main two-phase fluid circuit serving the plurality of server boards, with a descending pipe, an ascending pipe, a loop bottom connector and an upper portion, said upper portion being thermally coupled with at least one heat rendering exchanger located outside the enclosure, said main two-phase fluid circuit generally operating according to the thermosiphon principle,
• at least one evaporator in each of the served server boards, said evaporator being coupled to a hot source to be cooled down in the server boards (CPU, etc.),
• a plurality of local circuits, each local circuit respectively serving one of the server boards and operating in bypass with respect to the main circuit, each local circuit comprising on the one hand a first branch, forming a feed-in from a tapping in the descending pipe and, on the other hand, a second branch forming a fluid return in the ascending pipe of the main circuit, as well as an auxiliary circuit internal to the server board connected to one or several evaporator(s),
• and wherein first and second fluid-tight quick-disconnect fluid connectors are further provided, arranged respectively on each of the first and second branches,
• the system containing no active pumping member, neither in the main circuit nor in the local circuits.