Effect of the inclination angle on the transient performance of a phase change material-based heat sink under pulsed heat loads*

摘要

The transient performance of a phase change material (PCM)-based heat sink may be affected by its inclination angle because natural convection usually occurs and dominates melting during the operation of the heat sink. An experimental setup was designed and used in this study that allows for the alternation of the inclination angle of the heat sink. The inclination angle was varied from 0° to 90° at increments of 15°, while two pulsed heat loads (20 and 40 W) were adopted. 1-hexadecanol of a nominal melting temperature of 49 °C was selected as the PCM. The transient performance of the heat sink was characterized by the temperature variations at the center of the heat spreader under various conditions. The results showed that the transient performance of the heat sink is able to be improved by simply increasing its inclination angle which then facilitates the natural convection during melting. However, the variation in the performance is not a monotonous function of the inclination angle. Although the time-averaged thermal resistances of the heat sink were shown to be only marginally lowered, the maximum operation times may be greatly extended under the given thermal conditions. For a heat load of 40 W and the maximum allowable temperature of 75 °C, the operation time of the heat sink is extended by up to nearly 67% at an inclination angle of 75° when compared to that of the horizontal case. Based on the cases tested, the optimal inclination angle was found to lie between 60° and 75°.