Microchannel heat sinks 402-408 may be mounted on CPUs 490-496 respectively. The thermal actuators of flow regulation valves 418-424 may make tight contact with the top surfaces of CPUs 490-496 to ensure quick and accurate responses to temperature variations. Microchannel heat exchanging cores 410-416 may be located inside microchannel heat sinks 402-408. Microchannel heat exchanging cores 410-416 may be composed of multilayered, radial microchannels. The inlet quality of fluid may be controlled at the fluid's subcooled status, which may ensure a best heat transferring coefficient at the lowest wall temperature with minimal pressure drop. The wall temperature is the surface temperature of the heat source (i.e. the CPU).

Liquid supply hose 484 and vapor return hose 470 may run through server chassis 488 to be connected with microchannel heat exchanger 476. Liquid supply hose 484 and vapor return hose 470 may be composed of rigid materials, such as, without limitation, copper, plastic, etc. or flexible materials, such as, without limitation, rubber, plastic, fiberglass, etc. For example, if a high pressure refrigerant was used, the flexible hose could be a polyamide tube, polyester braid, PU sheath. If the working fluid was water, the tube could be PVC. Hard tunes, like copper, may also be used, though it involved higher installation costs and maintainability concerns. The type of tube used may depend on various factors, such as, without limitation, pressure rating of the refrigerant, cost of available materials, etc. Thus, minimal changes to a server chassis are required to incorporate reverse-return parallel loop system 400. Further, large supply and return manifolds may not be required in the present embodiment.