Session: 7.1 - Heat and Mass Transfer in multiphase flows

Paper Number: 170214

170214 - Experiments on Hot Wall Cooling With a Falling Liquid Film 

Abstract: 

Rapid cooling of hot solid wall by quenching is crucial to ensure safety of nuclear power plants during severe accidents. However, most of the existing quenching models rely heavily on empiricism and may not be applicable to varied thermal-hydraulic conditions encountered during severe accidents. In the present work, the spatial distribution of the heat transfer coefficient during quenching of hot vertical wall with a falling liquid film was measured under varied experimental conditions. To accumulate experimental data on the rapidly changing temperature distribution of the heat transfer surface during quenching, a silicon wafer that is transparent to the infrared ray was used as the hot wall and a high-speed infrared camera was used for temperature measurement. In consequence, it was elucidated that the main heat transfer mechanism near the quench front is nucleate boiling. Based on this experimental finding, a new quench model was developed using the two widely accepted correlations for nucleate pool boiling: Zuber’s critical heat flux correlation and Rohsenow’s heat transfer coefficient correlation. The proposed quench model succeeded to predict the quench velocities measured under varied conditions of wall material, wall thickness, initial wall temperature, liquid film flow rate, and liquid subcooling. It was also demonstrated that the quench velocity can be accelerated by fabricating a nanoparticle layer on a heat transfer surface. The effect of the nanoparticle layer was discussed from the two aspects: a decrease in the contact temperature and enhancement of the surface wickability.

Presenting Author: Tomio Okawa The University of Electro-Communications

Presenting Author Biography: