Macrolayer Formation Model for Prediction of Critical Heat Flux in Saturated and Subcooled Pool Boiling

Abstract

A macrolayer formation model for predicting the critical heat flux (CHF) in saturated and subcooled pool boiling was proposed. The concept of this model was based on the bubble coalescence process, which was observed using a high-speed camera. In the present model, the thickness of the macrolayer was calculated assuming that the liquid volume remaining under the lower part of the bubble should contribute to the formation of the layer. A Poisson distribution was adopted for the distribution of nucleation sites. The predicted macrolayer thicknesses were used for the prediction of CHFs in saturated and subcooled pool boiling based on the macrolayer dryout model. This model reproduced the CHF values for pool boiling up to subcooling 40 K. The model concept was confirmed using a computational fluid dynamics code, where the assumption was that the liquid was captured and the macrolayer was formed at the coalescence of bubbles.

Acknowledgment

This research was conducted using the supercomputer SGI ICE X in the Japan Atomic Energy Agency.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Ayako Ono

Ayako Ono is an assistant principal researcher at the Japan Atomic Energy Agency (JAEA). Her main research activities are in the field of the thermal-hydraulic phenomena in a nuclear power plant. In 2008, she received her PhD from Hokkaido University for research on the study of the critical heat flux (CHF) mechanism for saturated and subcooled pool boiling. Since she joined JAEA in 2008, she devoted her research efforts on development project of the sodium fast reactor such as the evaluation of flow-induced vibration for the piping and the development of the heat removal system driven by natural circulation. Recently, her research interests are the establishment of an evaluation method for CHF in light water reactors based on the CHF mechanism. Her approach is to combine the model to predict CHF and the detailed two-phase flow numerical simulation.

Hiroto Sakashita

Hiroto Sakashita received the PhD degree in 1998 from Hokkaido University, Japan. He started his research carrier in 1981 as a research assistant at the department of nuclear engineering, Hokkaido University. He is currently an associate professor of Division of Energy and Environmental Systems at Hokkaido University. His current research interests are thermal-hydraulic problems of nuclear engineering, especially critical heat flux in pool and forced convection boiling, boiling heat transfer at high pressures, and coolability of debris bed in severe accident. He is also interested in boiling in aqueous mixtures and critical heat flux in nanofluids.

Hiroyuki Yoshida

Hiroyuki Yoshida received the PhD degree from Kyushu University in Japan in 1994. He has more than 20 years of experience in nuclear thermal hydraulics, especially in two-phase flow simulation based on computational fluid dynamics. After the Fukushima-Daiichi accident, he has been developing multiphase simulation method related to a severe accident of light water reactor and has performed experiments to understand thermal-hydraulics phenomena and validate simulation codes. Currently, he is a group leader of the development group for thermal-hydraulics in Japan Atomic Energy Agency. He is also adjunct professor of the University of Tsukuba since 2009.