Influence of geometrical and operating conditions on the performance of the heat pipes: A review

Abstract

A heat pipe is one of the most effective devices for transferring heat from the heat source to the sink. It is a vacuum-tight device that depends on the phase-change conversion associated with highly effective thermal conductivity. A comprehensive review of experimental and numerical investigations related to the influences of the controlled geometrical parameters and operating variables on the thermal characteristics of heat pipes and thermosyphons is presented. These variables include the diameter and length of the heat pipe, working fluids, energy inputs, filling ratio, tilt angle, coolant flow rate, etc. The thermal features of the heat pipe is described by thermal coefficients and temperature differences through the condenser and evaporator, thermal efficiency, and thermal resistance. It is realized that the thermal resistance reduces, and the thermal coefficients increase with the amount of power input. In addition, the optimum values of tilt angles and fill ratios depend on the other controlled variables. However, the optimum filling ratio ranged from 15%-60%. While the best inclination angle was between 60° and 90°.