Based on the thermal requirements of future large European platforms such as the Columbus Space Station, several developments in the field of two-phase flow systems were initiated over the last few years in Europe.
This paper will give a general overview of the objectives, development status and test results of an ESA-funded ‘Two-phase heat transport system’ study and of two studies sponsored by the German Ministry of Research and Technology on two-phase heat transport.
The ESA two-phase loop system resulting from the concept trade-off is driven by an electrically powered liquid pump and is provided with a capillary cold plate and an evaporative heat exchanger mounted in parallel. Under certain conditions, a simplified version of this type of system is able to work in a capillary-pumped mode. The system is designed for a heat load of 10-20 KW, a length of 20 m, a working temperature around 20°C and R114 as working fluid. All critical items (cold plates, evaporative heat exchangers, condensers, accumulator, gas trap, vapour quality sensors and control algorithms) have been manufactured and tested and will be implemented in a two-phase flow test bad in the near future.
Within the German-funded development, a two-phase loop designed to be run with water, NH3 or Freon has been manufactured. Special care was given to the evaporator plates (swirl flow and capillary cold plates). Extensive studies were performed on capillary geometry and materials, so as to reach heat flux densities of up to 5 W/cm2 with water.