Abstract: To overcome the thermal management bottleneck of high-power spaceborne phased-array antennas and optimize the performance of their integrated fluid-loop cooling modules, the coupling effects of array irradiation patterns, coolant boundary conditions, and flow models on heat transfer performance were investigated through numerical simulations. The results showed that, compared with the time-averaged heat-flux mode, the peak heat-flux mode increased the array temperature difference by approximately 32%, whereas doubling the coolant flow rate reduced the temperature difference by about 25%. The turbulence model predicted significantly higher heat-transfer efficiency at the fluid-solid interface than the laminar model, demonstrating the suitability of turbulence modeling under high-Reynolds-number flow conditions. For engineering applications, the impact of peak heat flux should be mitigated through optimization of the thermal-shield layout. Cooling parameters should be properly balanced between flow rate and power consumption, and appropriate turbulence models should be adopted to improve prediction accuracy. These findings provide useful guidance for the thermal design of high-frequency, high-power-density spaceborne phased-array antennas.