ABSTRACT

Optimization of flat miniature heat pipes was carried out based on the existing and newly obtained experimental results and the quasi-Newton algorithms employing the BFGS (Broyden, Flether, Golfarb, Shanno) method. The heat pipe contains capillary axial grooves that were cut using the method of electric-discharge-machining (EDM). The general multivariable optimization methods were used to search for the optimum structure of the heat pipe. Based on the optimization results, a miniature copper-water heat pipe with external overall dimensions of 7 × 3 × 120 mm was fabricated and tested. Maximum heat transfer rates of 50 watts in the horizontal orientation and 70 watts in the vertical orientation at a working temperature of 100°C were achieved. The corresponding heat fluxes were 25 and 35 W/cm², respectively, based on the external heating surface area. These two values are increased to 40 and 56 W/cm² if the calculation is based on the dimensions of the vapor space. The heat transport capacity of the optimized heat pipe was increased by 66% to 100% at the working temperature of 100°C, compared to the non-optimized heat pipes. The effective thermal conductance of the heat pipe was 60 to 110 times that of a copper bar having the same overall dimensions.