Characterization of a Mechanical Pumped Fluid Loop (MFPL) by test campaign

Payload power in spacecrafts has increased during the last decades, a trend that is expected to continue in the future. The need for flexibility, the increase of payload power and payload power density mean that spacecrafts thermal control systems development is gaining importance. Mechanical Pumped Fluid Loop (MFPL) is the best solution for this problem as it can handle high heat fluxes and can flexibly remove heat from multiple payloads. Two-phase loops use the heat vaporization of the refrigerant fluid to transport heat and they present advantages over one-phase loops, like reducing fluid flow rates, decreasing temperature gradients and increasing heat transfer coefficients. Arquimea Space has developed a Mechanically Pumped Advanced Control Loop (M-ACL) under an ESA’s contract. Although it was planned to use a NACPA pump from RealTechnologie AG, this pump did not reach the planned and needed performance due to performance degradation from previous testing campaigns. Therefore, an industrial pump with expected characteristics has been used. The main components of this M-ACL are: HP Network (to introduce power), four evaporators, one accumulator, four condenser plates, one subcooler plate, two control valves, one centrifugal pump and transport lines. Additionally, two flowmeters and six pressure transducers have been introduced in the loop to monitor the performance. An exhaustive test campaign has been carried out to fully characterize its behaviour: test without pump with all evaporators operative and test with pump with one, two and all evaporators operative. During those tests, different conditions were imposed on the sink temperature and power levels and the influence of parameters, like temperature difference between accumulator and liquid stabilization chamber, and vapor quality at evaporator outlet in the thermal performance, are evaluated. A detailed thermo-hydraulic model was developed in EcosimPro simulation tool. Predictions where ambient conditions and heat leaks were considered, were made before testing.