The objective of the study was to investigate the mechanisms and heat transfer characteristics of phase-change thermal control unit during the flight of aircraft.Considering the conduction in the solid and natural convection in the liquid，the physical and mathematical model for the heat transfer was formulated.The governing conservation equations were solved using the finite-volume method on fixed grids.An enthalpy-porosity method was used for modeling the melting phenomena of phase-change thermal control unit.The time and space movement of the phase front，the temperature distribution，and the heat dissipation rate has been analyzed based on the model.The influence of the unit geometry，heat source location，type of phase change materials，as well as the boundary condition on the thermal performance of the thermal control unit was investigated.This model and numerical method was evaluated by comparing the numerical predictions with the experimental results.The results from the analysis elucidate the thermal performance of phase-change thermal control unit and will provide the bases to the design and optimization of thermal control unit.