Theoretical and experimental study on the thermal performance of flat miniature heat pipes including rectangular axial grooves

Experimental and theoretical studies are realized in order to verify the Mini Heat Pipe (MHP) concept for cooling high power dissipation electronic components, and determine the potential advantages of constructing mini channels as an integrated part of a flat heat pipe. In the experimental part of this study, a Flat Mini Heat Pipe (FMHP) prototype including a capillary structure composed of parallel rectangular microchannels is manufactured and a filling apparatus is developed in order to charge such FMHPs. The heat transfer improvement obtained by comparing the heat pipe thermal resistance to the heat conduction thermal resistance of a copper plate having the same dimensions as the tested FMHP is demonstrated for different heat input flux rates, heat sink temperatures, and orientations. In the theoretical part of this work, a detailed mathematical model of a FMHP with axial microchannels is developed in which the fluid flow is considered along with the heat and mass transfer processes during evaporation and condensation. The model is based on the equations for the mass, momentum and energy conservation, which are written for the evaporator, adiabatic, and condenser zones. The model, which permits to simulate several shapes of microchannels, can predict the maximum heat transfer capacity of FMHP, the optimal fluid mass, and the flow parameters along the microchannel. The comparison between experimental and model results shows the good ability of the numerical model to predict the axial temperature distribution along the FMHP.