Flat plate heat pipes: from observations to the modeling of the capillary structure
Résumé
This paper presents a synthesis of observations made inside six different flat plate heat pipes (FPHPs). Silicon and copper systems with different capillary structures and sizes are studied. They are hermetically sealed on their upper face with a transparent plate, which enables liquid-vapor interface observations. A confocal microscope is used to measure the liquid film shapes inside the systems and describe the meniscus curvature radius from the evaporator to the condenser. Physical mechanisms, including the boiling limit and the effect of the interfacial shear stress, involved in different capillary structures such as grooves or meshes are discussed. Experimental results are compared to an analytical model describing both the liquid and vapour flows inside the FPHP and coupled to an analytical solution for the wall temperature. The capillary structure is modeled by considering the permeability and the equivalent thermal conductivity of a porous medium. The comparison between the model and the experimental data makes possible the estimation of the physical properties of the capillary structure. These experimental parameters are introduced in the model to estimate the performance of the heat pipe in a real application with several electronic components.
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