Dry spot propagation during boiling crisis on thin metal heaters

Abstract

This work presents the results of an experimental investigation aimed at elucidating the role of heater-side parameters on the growth of an irreversible dry spot during the boiling crisis of FC-72 on thin metal foils. A two-sided funnel shape of the heater is adopted to induce the occurrence of the boiling crisis in the middle of the foil and capture the expansion of the critical dry patch through high-speed infrared thermometry. In agreement with pre-existing literature, critical heat flux values achieved during this experimental campaign are shown to increase with bulk subcooling, thermal effusivity, and thickness of the heater. The transient temperature field at the boiling surface is used to capture the spatiotemporal evolution of the dry spot and investigate the effect of heater’s parameter on dry spot propagation. Results collected in this work show that the growth of an irreversible dry patch is strongly affected by the heat diffusion process occurring within the thin heater. The dry spot propagation rate is found to be proportionally correlated with the thermal diffusivity of the heater and the volumetric heat dissipation rate achieved at the boiling crisis, the latter being inversely proportional to heater’s thickness. These results provide important insights into the dryout dynamics related to the boiling crisis in thin wall heat transfer devices. Nevertheless, they open questions about the role of fluid thermophysical properties, that still deserve to be studied in detail.