Speaker
Description
Single evaporator heat loops (HL: LHP, CPL, etc.) are well-studied two-phase heat transfer devices, both theoretically and through many applications in spacecraft thermal management. Classical HL are well suited for operation with concentrated heat sources. However, collection of heat from a wide flat area by HL evaporator comes at a cost of using additional interfaces (saddles, embedded heat pipes, vapor chamber etc.) or using multiple LHPs. These solutions bring unwanted thermal resistance at interfaces or complicate assembly and integration.
Another way to solve the task is through the use of multievaporator LHP, which is currently going through engineering model development stage. Multievaporator, comprising a grid of interconnected capillary pumps and compensation chambers, is at the core of technology that may adapt classical LHP to unconcentrated heat sources, often present in spacecraft modules. With 250x250 mm heat collection interface, overall LHP conductance with 6 m long transport lines can reach 100W/K value.
Multievaporator has demonstrated operation with different working fluids, such as ammonia, butane, R1233zd(E) and R134a, with different length of transport lines (up to 16m with ammonia), as well as various heat rejection modes and their combinations: radiation as in space environment, but also forced and natural convection, helpful for characterization. Throughout the characterization tests, the test setup was developed from measurement of steady state heat transfer capability to going through shock transient regimes, including variation of loop hydraulic resistance, heat sink temperature and heat transfer coefficient.
Overall, multievaporator LHP is a versatile device. Its modularity make it possible to adapt for different use scenarios regarding choice of working fluids, length of transport lines and heat source power and dimensions.
