A reduced-order framework for performance mapping of compact parallel-channel evaporator

The increasing demand for thermal management of electronic components in modern aerospace and terrestrial applications has driven the development of two-phase mechanically pumped loops (2PMPLs), equipped with compact evaporators capable of exploiting the latent heat of vaporisation to manage high heat-flux operating conditions. Among heat acquisition components, compact parallel-channel evaporators are particularly attractive due to their high wetted-area-to-volume ratio; however, their integration into system-level models remains challenging because of the lack of reliable constitutive equations for the fluid-side heat transfer coefficient (HTC) in such non-standard geometries. This work proposes a reduced-order framework for obtaining an effective HTC capable of quantifying the average heat transfer performance of the evaporator at a given operating point. Wall temperature measurements, obtained under controlled heat input conditions, are combined with finite element modelling to infer fluid-side HTC values through an inverse heat transfer approach. The estimations, performed on cross-sections associated with six control points distributed along the axial length of the evaporator, enable the determination of an average heat transfer value for the component, interpreted as an effective HTC representative of its behaviour under the corresponding steady-state operating condition. The effective values obtained for the heat transfer coefficient and the internal wall temperature are subsequently employed in a consistency analysis using a one-dimensional thermo-hydraulic model of a two-phase mechanically pumped loop. This procedure ensures that the reduction of the heat transfer phenomenon to a single effective value remains compatible with the expected enthalpy evolution and the overall system response. The proposed reduced-order methodology aims to provide a consistent basis for the performance analysis of parallel-channel evaporators and to support design-oriented studies of two-phase thermal management systems.