Abstract: To address the thermal management requirements of high-heat-flux electronic equipment in aerospace applications, a radial-flow sector-shaped plate-fin evaporator operating under consumable cooling conditions was investigated. The key structural parameters of the evaporator were preliminarily selected through numerical simulations. An open-loop experimental platform was established, utilizing an antifreeze fluid loop to simulate onboard thermal loads, enabling experimental testing of the flow and heat transfer characteristics of the expendable evaporator under typical operating conditions. The experimental results indicate that the impact of flow direction on the performance of radial flow sector plate fin evaporators exhibits significant dependence on operational conditions, with distinct crossover features between parallel flow and counter flow observed in medium-low and high thermal load ranges. In low-medium thermal load ranges, parallel flow demonstrates superior heat exchange performance due to the maximum initial temperature difference at the inlet section of the flow channel. However, under high thermal loads, counter flow surpasses due to its ability to sustain continuous and stable heat transfer driving forces and liquid phase wetting conditions in the latter half of the flow channel. Combined with numerical simulations, the mechanisms of two flow directions—parallel and counter flow—on the flow and heat transfer characteristics were systematically studied. Through analysis of temperature fields, gas phase volume fractions, and velocity fields, it was found that the primary cause of performance differences lies in the different axial temperature matching relationships between hot and cold fluids established by the two flow modes. Counter flow, through its inherent reverse temperature profile characteristics, extends the length of liquid film wetting, optimizing the heat transfer process in high heat flux regions. This research provides experimental evidence and theoretical references for the design and operation methods of evaporators targeting high heat flux dissipation scenarios.

Key words: Evaporator, Flow boiling, Plate-fin, Offset strip fin, Radial flow, Parallel and counter flow