Phase change material heat sinks

A heat sink includes a core body. The core body defines a coolant plenum, sealed first and second chambers, and first and second coolant conduits. The sealed first and second chambers each house a phase change material. The first and second coolant conduits are separated from one another by the coolant plenum and are in fluid communication with the coolant plenum for transferring heat between coolant flowing through the core body and the phase change material.