The Effect of Rotational Speed on Thermosiphon Cooling for the Application of Drill-bit Cooling

In a rotating wickless tapered thermosiphon, the centrifugal force drives circulation between the boiler and condenser sections leading to high heat transfer capability. This can be utilised for reduced cutting temperatures and increased tool life in a manner that promotes environmentally friendly dry-machining operations. Herein, an effective gravity derivation is proposed and presented as an improved correlation for determining burnout heat flux (boiling) and entrainment (flooding) limitations. In order to enclose the proposed effective gravity, Sun and Lienhards boiling limit and Faghri's flooding limit correlation are modified enabling predictive performance in multiple operating orientations, whereby the external effect of gravity may aid or oppose working fluid flow. A conical test rig was constructed to validate the proposed effective gravity. A flooding limit correlation for a rotating tapered thermosiphon is presented, alongside with the system filling ratio and the geometrical design recommendations.