Development and Test Results of a 5kW Ammonia Capillary Pumped Loop

This paper presents the design, testing and analysis of the 5kW ammonia Capillary Pumped Two Phase Loop (CPL), developed in co-operation between MATRA MARCONI SPACE (MMS) and the French Space Agency (CNES).

The ammonia CPL breadboard was designed to transport a 5 kW heat load over 5 meters. It consisted of:

• 5 parallel evaporators and isolators,
• 4 parallel condensers with an additional sub-cooler,
• a reservoir, to control the loop saturation temperature,
• two adiabatic pipes, one for the liquid line and one for the vapour line
• the testing instrumentation including thermocouples and absolute and differential pressure transducers.

Test results presented show the performance measured on the loop (horizontal position) for:

• maximum capillary head pressure for each evaporator according to the saturation temperature and the applied heat load,
• maximum and minimum heat load density,
• start-up, steady state and transient behaviour, re-priming after dry-out,
• evaporator temperature control ability,
• heat load sharing between evaporators.

The mathematical analyses were performed with CEDRIC software, which models fluid networks for single and two phase flow, by solving the three balance equations (mass, momentum and energy).