Saturated pool film boiling heat transfer around vertical spheroids

This study analytically and experimentally investigates the saturated pool film boiling heat transfer around vertical spheroids in a gravity field. The analysis employed the integral method to consider surface tension. The analytical solution for the dimensionless vapor film thickness varies with the reciprocal of the Bond number and the eccentricity at the vertical cross-section containing the centroid of the prolate spheroid. Film boiling experiments utilize five test cylinders made of pure aluminum. The test cylinders include two types of prolate spheroids as well as a sphere and two types of oblate spheroids. The coolant is ion-exchange water under atmospheric pressure. The temperature history of the test cylinder is monitored using a thermocouple installed at the center. The average heat flux is calculated under the assumption of a uniform temperature inside the test cylinder. A factor derived from the analytical results is employed to quantify the dimensionless average heat transfer coefficient and to establish a correlation with the experimental results. The key findings are as follows: (1) Surface tension affects the vapor film thickness and the vapor velocity within the vapor film but has little effect on the average heat transfer coefficient. (2) The dimensionless average heat transfer coefficient for the prolate spheroid surpasses that of the oblate spheroid. (3) The analytical outcomes obtained using the integral method enable the alignment of experimental values within a range of $\pm$15%.