Flow and Temperature Control of Mechanically Pumped Fluid Loops under Low Reynolds Number Conditions

To control the temperatures of components serviced by a mechanically pumped fluid loop, valves are generally equipped to adjust the mass flow rates through the cold plates. This strategy has been adopted by the Internal Thermal Control System in International Space Station, and would be employed by the Scientific Experiment Rack (SER) fluid loop of Chinese Space Station. For a certain opening of the valve, the mass flow rate is determined by the system flow impedances or pressure loss coefficients. Usually the pressure loss coefficient, especially for the local flow impedance, is assumed to be independent of Reynolds number. However, for laminar or transition flow regimes, the pressure loss coefficient is strongly affected by the Reynolds number, and unexpected flow rate or temperature results could be caused by improper assumptions. As a case study, sensitivity analysis was conducted to access the impact of low Reynolds number for a prototype of SER fluid loop developed by Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences. A thermal-fluid network model was established and the relationship between flow resistances and Reynolds numbers was varied to explore how it affected the flow rates and temperatures when valve openings were adjusted. The result showed that the effects could be reduced by reasonably selecting the working scope of the valves and the design of the SER fluid loop is robust. Although the investigation was conducted for this particular product and the specific data would only be valid for the current design, the analysis could provide guidance for future refinements and related applications.