A data center cooling system includes a modular heat sink and a working fluid. The modular heat sink includes an evaporator configured to thermally contact a heat-generating electronic device to receive heat from the data center heat-generating electronic device; a condenser coupled to the evaporator and configured to transfer the heat from the heat-generating electronic device into a cooling fluid; and a plurality of transport tubes that fluidly couple the evaporator and the condenser, at least one of the plurality of transport tubes including an open end positioned in the evaporator and a closed end positioned in the condenser. The working fluid vaporizes in the evaporator based on receipt of the heat from the heat-generating electronic device, and circulates, in vapor phase, from the evaporator to the condenser in the transport member, and circulates, in liquid phase, from the condenser to the evaporator.