Payload Dedicated Evaporator (PDE): Application, Concept, Design and First Test Results 921206
The Payload Dedicated Evaporator (PDE) has applications in many fields of space vehicle utilization, where the dissipating systems or payloads have a limited operational time. The evaporator is directly connected to the heat source and as such its application is possible in space systems without active cooling loops. Also in systems with cooling loop and radiators the PDE can be used to reject high peak heat loads which overshoot the radiator design values.
The PDE consists of a tube with inner capillary grooves in the axial direction. One end of the tube, the evaporating zone, is connected to the heat source. The other end interfaces with the vapor exhaust line. This end is equipped with a liquid trap to collect recondensed or slugged liquid evaporation fluid. The retained liquid is capillary pumped back to the evaporation zone in the axial grooves. This process is similar to a heat pipe.
Expended vapor, which is vented overboard must be substituted by injection of new evaporation fluid inside the tube. The injector consists of a flow control valve (FCV), the seat of which is the injecting nozzle. This FCV is directly flanged to the tube and interfaces the liquid supply line from storage tank to the evaporator.
The liquid trap consists of a hydrophobic membrane. Since recent test results showed that no ammonia but only water can be retained with such traps, water has been used as evaporation fluid within the first application tests.
The test results showed, that even with a simple system it is possible to reject up to 200 W per PDE.