In fields of data centers, power semiconductors, batteries, LEDs, etc., the rapid increase in heat generation density of equipment due to miniaturization and higher performance has become a problem, and the development of high-performance thermal control equipment is urgently needed. In particular, energy-saving devices are required from a carbon-neutral perspective. Therefore, this study focuses on a heat transport device that can operate without electricity, the loop heat pipe (LHP), which circulates fluid by capillary force acting on a porous body and transports heat by evaporation and condensation. The evaporator with porous media is governed by liquid-vapor two-phase flow in the porous media, which involves evaporation. We have been working to elucidate this physical phenomenon in evaporators and developed a original design method for evaporator geometry. We are also working to achieve higher performance by controlling the microstructure of the porous media. We are also working on applications such as solar heat utilization by utilizing the knowledge we have obtained so far.