Experimental study on the onset of flow instability in small horizontal tubes at supercritical pressures

The flow instability of hydrocarbon fuel is an important factor in the design of a regenerative cooling channel due to flow excursion accidents. To explore the mechanism of the instability process, the onset of flow instability (OFI) of cyclohexane were investigated experimentally in horizontal tubes at supercritical pressures. The geometric structure of the test channel, with a tube length of 0.20-0.79 m and inside diameter of 1.0-2.0 mm, was studied with regard to static flow characteristics. Based on the experimental data, a dimensionless analysis was conducted, and a new correlation to predict the OFI for supercritical fluids was obtained.