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Indexed by:Journal Papers

Date of Publication:2019-12-01

Journal:EXPERIMENTAL THERMAL AND FLUID SCIENCE

Included Journals:EI、SCIE

Volume:109

ISSN No.:0894-1777

Key Words:Supercritical pressure; Hydrodynamic characteristics; Mini-tube; Buoyancy; Static instability

Abstract:To meet the design requirements of a regenerative cooling circulation structure for aircraft, the hydrodynamic characteristic of fuel needs to be studied further. In this study, experiments were performed to investigate buoyancy effect on the multi-valued hydrodynamic characteristics and the onset of flow instability (OFI) of cyclohexane. The influence of flow directions in vertical and horizontal tubes were analysed, and the buoyancy effects in the hydrodynamic process was clarified. The negative slope of the hydrodynamic curve for horizontal flow was greater than that for vertical flow, and the mass flow rate corresponding to OFT of the horizontal tubes was also larger than that of the vertical tubes. The results demonstrated that the horizontal tubes are more prone to static instability. The buoyancy effect of the near-wall fluid on the hydrodynamic characteristics cannot be neglected. Finally, a new correlation considering buoyancy effect was introduced to predict the OFI of supercritical fluids in different flow directions.