Improvement of Heavy Load Device Cooling Using R1234ze(E) by Laser Interference Surface Structuring

Abstract

Thermal management of electronic devices becomes increasingly important for their stable operation. To improve the heat dissipation performance in confined installation spaces, passive two-phase cooling technique is being applied. The key technique is enhancement of boiling heat transfer because the surface area in evaporators attached to CPU chips is very limited. Therefore, the effects of finned and LISS (laser interference surface structuring) boiling surfaces made of copper, shown in Figure 1, are experimentally investigated with A gravity-driven cooling circuit, so called looped thermosyphon, using R1234ze(E) as the working fluid. The estimated active nucleation cavity ranges from 0.1 to10 m for R1234ze(E) at a saturation temperature of 25 °C, which is about the size of agglomerated grain microstructures formed by LISS. This results significant nucleate boiling enhancement; however associates the well-known hysteresis of boiling inception, as shown in Figure 2. Nevertheless, the employed boiling surfaces successfully kept the chip temperature below 80 °C at imposed heat fluxes up to 1350 kWm^-2. From the experimental assessment, it was demonstrated that introducing enhanced boiling surface fabricated by LISS is promising idea to improve heat dissipation performance of looped thermosyphons for highly integrated CPUs.