Pressure drop characteristics in single-side heated circular smooth channel under sub-cooled flow boiling conditions

In this study, the two-phase pressure drop for a one-side heated smooth channel was explored through subcooled flow boiling experiments for divertor applications. When the channel heat load was gradually increased, there was little differential pressure change in the single-phase regime, but when it exceeded the onset of significant void (OSV) heat flux, the differential pressure started to increase. It was found that as the subcooling and flow rate increased, the OSV heat flux increased, and the slope of the two-phase differential pressure decreased, This is because it is possible to condense the generated vapor more quickly under these conditions. Moreover, as the pressure increased, the OSV heat flux increased and the size of the ejected single bubble decreased under high pressure conditions. The prediction performances of existing two-phase pressure drop multiplier correlations were also evaluated. Since most of the existing correlations were developed based on channels of a small diameter, and were not evaluated at a high heat flux, that is, in the order of 10 MW/m²—they exhibited a high average error rate. Therefore, we developed a new two-phase pressure drop multiplier correlation for a smooth channel under one-side high heat load conditions using PYTHON code and artificial intelligence regression method.