Multi-evaporator hybrid loop heat pipe for small spacecraft thermal management

This paper describes the design, development, modeling, and testing of a miniaturized multi-evaporator hybrid loop heat pipe (ME-HLHP), a centralized thermal bus (CTB) architecture proposed as the next-generation thermal management system (TMS) for future small spacecraft. This work was performed during a 6-month phase. A study as part of the NASA ST-8 program. To validate ME-HLHP technology, single, dual, and quad-evaporator test loops were designed, fabricated, and tested. SINDA/FLUTNT models of the ME-HLHP system were developed to optimize loop thermal-hydraulic design. The results indicated quad-evaporator transport (8-280 W), single-evaporator transport (2-100 W), maximum flux (30 W/cm²), conductance (5-8 W/K per evaporator), heat load sharing (> 95%), condenser switching, sink temperature variation (233-273 K), freeze tolerant condenser design, temperature control (+/- 0.25 K, variable set-point), rapid start-up (∼ 30 minutes), low control power (2-3 W), and Teflon wick evaporator durability (233-353 K cycling). Plans to continue ME-HLHP technology development leading to an ST-8 flight experiment were formulated.