The development of space is a great dream left to mankind. About 40 years have passed since the artificial satellite was launched for the first time in the world. At present, international telephone communication can be made through comsats and the image of clouds can be seen on television and newspapers through a meteorological satellite. With a greater power output in satellites and spaceships, the thermal control system must be considered for the recovery, transport, and disposal of waste heat. The change of phase of the working fluid results in lower electrical power requirement to operate pumps and gives a relatively isothermal sink temperature. Various system designs must be made to accomplish this two-phase thermal management capability. However, there is only little information available, as a restricting factor, on the fluid and heat transfer characteristics of two-phase flows such as pressure drop, flow pattern, and heat transfer in reduced-gravity environments. Here, the present status of investigation on gas-liquid two-phase flow under microgravity environments is outlined with a development of space radiator techniques for use in space.
