Utilizing refrigerants in passive two-phase cooling for electronic devices

With rapid development of electronic devices, internal heat generation in those becomes significantly denser. Accordingly, their thermal management becomes increasingly important for the stable operation. For the heat dissipation performance improvement in limited installation spaces, 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 using R134a and R1234ze(E) is experimentally investigated. The well-known hysteresis of boiling inception was confirmed but negligible with R134a and R1234ze(E). The experimental circuit successfully kept the heating block temperature simulating electronic devices below 80 °C at heat fluxes up to 125 W cm^-2 with R1234ze(E). Furthermore, by using a super-hydrophilic boiling surface, the heat flux was extended to 135 W cm^-2. The experiment demonstrated that using the refrigerant, instead of water, and super-hydrophilic surfaces could be a beneficial solution for electronic device cooling.