Parametric investigation of film boiling heat transfer on the quenching of vertical rods in water pool

Highlights: • The effects of liquid subcooling, thermophysical properties, and surface conditions on T_min were experimentally investigated. • Surface characterization analyses were performed to obtain essential information needed to identify the effects of surface condition on T_min. • The quenching behavior for various surfaces was captured sing a high-speed camera. • Substrate materials with lower thermophysical properties and higher porosity were observed to quench faster. • A new generalized correlation to predict T_min was developed based on the experimental data. The present study explores the effects of liquid subcooling, material properties and surface conditions on the film pool boiling heat transfer using stainless steel (SS), zirconium (Zr), and Inconel-600 rods. Vertical quenching experiments were performed in subcooled and saturated distilled water pool at atmospheric pressure. Surface characterization results (microscope images, surface roughness, and water contact angle) were obtained to characterize the morphology of the substrate surface of the test samples. A visualization study was carried out using a high-speed camera to observe the phenomenon of quench front axial propagation in addition to the instability of the vapor-liquid interface. Embedded thermocouples are used to measure the change in temperature of the test samples with time. An inverse heat conduction code was used to determine the surface temperature and the corresponding heat flux curves. The effects of liquid subcooling, thermal properties of the substrate, and surface conditions on the minimum film boiling temperature ($T_{\min }$) were investigated. The lower $k\rho c_p$ and the porous surface of the Zr test sample disturb the flow of the vapor during film boiling. This along with the lower contact angle of the Zr surface resulted in a higher $T_{\min }$ value compared to the other two test samples. A generalized correlation was developed and compared to various existing correlations. The effects of liquid subcooling, surface roughness, and thermal properties of the substrate materials were taken into account in developing the correlation. The average error estimated for the generalized correlation is $1.5\%$ and the root-mean-square error is $9.3\%$.