Experimental Study of Heat Transfer Mechanisms under Exponential Power Excursion in Plate-Type Fuel

Abstract

This paper presents an investigation of transient pool boiling heat transfer phenomena for water at atmospheric pressure under rapidly escalating heat fluxes on plate-type heaters, which were used to simulate the interface between cladding and coolant in plate-type fuel during Reactivity Initiated Accidents (RIAs). The investigation utilized Infrared (IR) thermometry and High-Speed Video (HSV) to gain insight into the physical phenomena and generate a database that can be used for development and validation of accurate models of transient boiling heat transfer. The test matrix included exponential power escalations with periods in the range from 5 to 100 milliseconds, and subcooling of 0, 25 and 75 K. The onset of nucleate boiling (ONB), onset of significant void (OSV) and overshoot (OV) conditions were identified. The experimental data suggest that ONB, OSV and OV temperature and heat flux increase monotonically with decreasing period and increasing subcooling. The transient boiling curves were measured up to the fully developed nucleate boiling (FDNB) regime.