Abstract Heat generation density from semiconductor devices increases with the rapid development of electronic technology. The cooling system using boiling two-phase phenomena attracts much attention because of its high heat removal potential. Most of heat transfer researches concerning the development of electronic devices are conducted for the cooling of small semiconductor chips, while there are limited numbers of innovative investigations for the cooling of a large area at extremely high heat flux larger than 2×10 6 W/m 2 . The technology can be applied to the cooling systems in space, e.g., cooling of laser medium in solar power satellites when solar energy is converted to laser power. To develop compact and high-performance cooling systems, a structure of narrow heated channel between parallel plates with auxiliary unheated channel was devised and tested by using water in three different kinds of experimental conditions. One of liquid supply method, where liquid is supplied to both of the main heated and the auxiliary unheated channel keeping the exit of the auxiliary channel closed, gives the highest CHF value at total volumetric flow rates more than 3.0×10 -5 m 3 /s and 2mm gap size of main heated channel
