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In the scope of the COLUMBUS-preparatory support technology programme, funded and coordinated by the European Space Agency (ESA/ESTEC), critical components of a mechanically pumped two-phase heat transport system, i.e. evaporator cold plate, evaporative heat exchanger, vapour quality sensors, condenser, accumulator, gas trap and control system, have been identified and developed by a number of European companies under Dornier-subcontract. A comprehensive test programme, focussed on the investigation of critical components performance characteristics and limits, has generally demonstrated very satisfactory and partially even excellent results. However, experience gained during test performance as well as overall test evaluation have concluded in several recommendations for further analysis, improving modifications and a continuation of testing aimed at an enhancement of European two-phase technology know-how.

Under the COLUMBUS Preparatory Support Technology Programme, the European Space Agency has coordinated the development of critical components for a European pumped two-phase heat transport system. The critical components are Evaporator Cold Plate (Dornier GmbH), Evaporative Heat Exchanger (Aeritalia) being an interface component to an external loop, Heat Rejection Interfaces/Condensers (Fokker), active Accumulator/Control Reservoir (British Aerospace) and Vapour Quality Sensors (Dornier GmbH and NLR). They have been incorporated into a flexible and fully instrumented test bed at BAe. The test bed is designed to evaluate the performance of a complete representative loop with heat loads up to 15 kW and primary loop lengths up to 40 metres. It includes an implementation of algorithms developed at Fokker and NLR for the control of evaporator inlet temperature conditions, vapour temperature setpoint and vapour quality.

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.