Abstract: A heat exchanger comprising a first surface, a second surface, and a spacer configured to maintain a cavity between the first surface and the second surface, wherein the cavity has a thickness less than or equal to about 20 thousands of an inch (mils) and has a width-to-thickness ratio greater than or equal to about 8:1, and wherein the cavity allows any fluid in the cavity to exchange heat with the first surface, the second surface, or both is disclosed. Also disclosed is an apparatus comprising a thermal load and a heat exchanger substantially adjacent to or integrated with the thermal load, wherein any fluid flowing through the heat exchanger has a velocity greater than or equal to about 20 feet per second (fps).