Improving the heat dissipation performance of a looped thermosyphon using low-GWP volatile fluids R1234ze(Z) and R1234ze(E) with a super-hydrophilic boiling surface

With the rapid development of electronic devices, internal heat generation in these devices becomes significantly denser. Accordingly, their thermal management becomes increasingly important for stable operation. For the performance improvement of heat dissipation in limited installation spaces, passive two-phase cooling technique using water is applied. Instead of water, using a more volatile substance as the working fluid is advantageous in many aspects. For instance, the higher volumetric capacity that is the product of vapor density and latent heat of vaporization allows compactness, while higher boiling heat transfer coefficient can extend the stable operation conditions under heavy loads of the electronic devices. In this study, a gravity-driven cooling circuit known as thermosyphon using refrigerants R134a, R1234ze(E), and R1234ze(Z) is experimentally investigated. The experimental thermosyphon successfully kept the heating block temperature simulating electronic devices below 80 °C at heat fluxes up to 1400, 1250, and 1110 kW m⁻² with R134a, R1234ze(E), and R1234ze(Z), respectively. Furthermore, using a super-hydrophilic boiling surface fabricated by laser irradiation, the heat flux was extended to 1600, 1400, and 130 kW m⁻², respectively. The experiment demonstrated that using the selected volatile fluids and super-hydrophilic surfaces could be a beneficial method for cooling electronic devices.