Transient pool boiling of liquid nitrogen (a safe analogue of LNG) on AISI 304 stainless steel flat surfaces

Abstract

Reducing the boil-off rate of liquefied natural gas (LNG) stored in an LNG cargo containment system (CCS) is one of the key concerns in the design of CCSs in terms of both safety and economy. Correlations for transient boiling on steel surfaces, which show the relationship between the heat flux and the wall superheat, are beneficial for the estimation of the boil-off rate of LNG in a CCS during a loading process. However, these boiling correlations are not yet available. In this study, an attempt was made to fill this gap. Specifically, transient boiling experiments of liquid nitrogen on AISI 304 stainless steel were performed. Liquid nitrogen was used because it has been commonly considered a safe analogue of LNG in laboratory tests. It was observed that the boiling curves for transient boiling deviated significantly from that for steady boiling. The boiling correlations were obtained by adjusting the correlations for steady boiling using the experimental results for the temperature difference range of 5–200 K. In addition, it was experimentally confirmed that the assumption of perfect thermal contact between a liquid and a boiling surface is inapplicable to boiling on a metal surface. The findings of this study are expected to be beneficial for the estimation of the boil-off rate of LNG and the analyses of the thermal stress distribution in a CCS during a loading process.