Biomimetic porous wick with efficient fluid transport and excellent heat transfer for loop heat pipes

Abstract

The porous wick, as a core component of the loop heat pipe (LHP), serves as a source of circulation power. Inspired by the transport system of plant vessels, a radially stacked polyethersulfone (PES) porous wick was designed using PES membranes with an anisotropic porous structure. The PES membranes exhibited excellent capillary force and high permeability. However, the supply capacity of the axially stacked wick was far inferior to that of sintered wick due to the problem of contact gaps and pore misalignment between layers. From the bionic point of view, a laminar winding special transport structure, which is perpendicular to the direction of liquid transport was proposed. The method effectively avoids the adverse effects of gap and pore misalignment on liquid transport. Combining experimental and simulation methods, the heat transfer characteristics and liquid transport characteristics of the radial stacking polyethersulfone wick (RPES) were studied and compared with those of traditional axial stacking polyethersulfone wick (APES) and sintered nickel wick. The results showed that the heat transfer performance of RPES-LHP was significantly improved, with the heating surface temperature maintained at 54.1 °C and thermal resistance of 0.095 °C/W under a heat load of 400 W, which was respectively 26.6 °C and 0.066 °C/W lower than that of the APES-LHP. The evaporator thermal resistance of RPES-LHP also ranked among the top in existing research on wicks. Simulation results indicated that the radial stacking method avoided capillary force weakening and flow resistance increase caused by gap and pore misalignment, thereby enhancing the supply capacity of RPES. The concept of regulating the stacking orientation of the wick to be perpendicular to the direction of liquid transport can strengthen the supply capacity and provide light on the design of porous wicks in the future.