Iimproving heat dissipation performance of a looped thermosyphon using volatile low-GWP working fluids with a super-hydrophilic boiling surface

Abstract

With rapid development of electronic devices, their internal heat generation become significantly denser. Accordingly, the thermal management becomes increasingly important for their stable operation. For the heat dissipation performance improvement in limited installation spaces of integrated computer packages, passive two-phase cooling technique using water is being applied. Instead of water, using refrigerants as the working fluid is advantageous in many aspects. The large heat transport rate in refrigerant vapour allows compactness, while higher boiling heat transfer coefficient can extend the stable operation conditions with heavy loads of electronic devices. In this study, a gravity-driven cooling circuit so called looped thermosyphon using water, R134a, R1234ze(E), and R1234ze(Z) are experimentally investigated. The well-known hysteresis of boiling inception was confirmed but negligible with R134a, R1234ze(E) and R1234ze(Z). The experimental circuit successfully kept the heating block temperature simulating electronic devices below 80 °C at heat fluxes up to 1400, 1250, and 1110 kWm^-2 with R134a, R1234ze(E), and R1234ze(Z), respectively; meanwhile that is 750 kWm^-2 with water. Furthermore, by using a super-hydrophilic boiling surface, the heat flux was extended to 1600, 1400, and 1350 kWm^-2 in R134a, R1234ze(E), and R1234ze(Z). The experiment demonstrated that using the selected volatile working fluids, instead of water, and the super-hydrophilic surface can be a beneficial solution for electronic device cooling.