Mission-oriented hierarchical multi-temperature thermal management for UAV avionics using vapor-compression/thermoelectric hybrid system

Unmanned aerial vehicles (UAVs) increasingly integrate avionics with distributed heat sources, high heat fluxes, multiple temperature levels, and stringent temperature-control requirements, challenging conventional single-mode cooling. Existing vapor-compression/thermoelectric systems mainly use thermoelectric modules (TEMs) for subcooling or localized regulation, with limited coordination between hardware design and scheduling optimization. This study therefore proposes a hierarchical thermal-management system coupling a vapor-compression refrigeration system (VCRS) with single-, two-, three-, and four-stage thermoelectric branches to distribute the required temperature lift across complementary cooling levels. A mission-oriented two-stage optimization framework is developed: Stage 1 determines the branch-wise TEM installation through full-envelope feasibility screening and Pareto analysis, while Stage 2 jointly schedules the active-module vector, branch currents, low-temperature evaporating temperature, and intermediate pressure for nine mission tasks. The balanced installation is [13, 16, 9, 10]. Under optimal scheduling, the system COP ranges from 1.56 to 4.55, with all 48 TEMs active during severe Tasks 5–7 while maintaining a COP of 1.56–1.59. Three operating regimes are identified, with an empirical transition near a relative TEM power contribution of 0.4. Below this level, compressor-side benefits dominate, whereas above it, increasing TEM power and hot-side heat rejection become controlling. Under identical Task 7 boundaries, the proposed system achieves a COP of 1.59 at 1777.99 W, reducing power consumption by 58.9% and 70.9% relative to minimum-feasible VCRS-only and minimum-power TEM-only benchmarks, respectively, while limiting the compressor pressure ratio to 3.93. The proposed framework provides a mission-adaptive approach for hierarchical UAV avionics thermal management over the full flight envelope.