Thermohydraulic Study of a Flat Plate Heat Pipe by Means of Confocal Microscopy: Application to a 2D Capillary Structure

Abstract

Thermal and hydrodynamic experimental results of a flat plate heat pipe (FPHP) are presented. The capillary structure is made of crossed grooves machined in a copper plate. The shape of the liquid-vapor interface in this type of capillary structure—that can also be viewed as an array of posts—is studied theoretically and experimentally. A confocal microscope is used to visualize the liquid-vapor interface and thus the capillary pressure field in the system. These hydrodynamic measurements, coupled to temperature measurements on the FPHP wall, are used to estimate the permeability and the equivalent thermal conductivity of the capillary structure filled with methanol or FC72. These parameters are obtained from a comparison between the experimental data and an analytical model. Finally, the model is used to compare the draining capability of crossed grooves with that of longitudinal grooves.