EXPERIMENTAL TERRESTRIAL STUDY OF AN AMMO NIA 2-PHASE LOOP FOR THERMAL CONTROL IN SPATIAL ENVIRONMENT

This paper presents the terrestrial test results of a mechanically pum ped two-phase fluid loop, using ammonia as the working fluid. The 600 W experimental set-up (main components, instrumentation) is described, The two-phase flow patterns observed are compared with several flow r egime maps. The experimental results are in good agreement with the pr edictions of Taitel and Dukler. The condensation lengths and the mean heat transfer coefficients of the condenser are given. The friction pr essure gradients of adiabatic two-phase flow increases with mass flow rate and quality. The wall temperatures and heat transfer coefficients of the evaporator show the influence of the liquid distribution on th e heat transfer : it is better at the top than at the bottom of the tu be and at the ends than in the center part of the evaporator. The best evaporation coefficients are obtained with high mass flow rates and l ow qualities. The results obtained show the good operation of the syst em.