Flashing Phenomena of Liquid Nitrogen in a Pressure Vessel Under Rapid Depressurizations

Abstract

In recent years in Japan, the demand of cryogenic fluids like a LH2, LNG is increasing because of the advance of fuel cell device technology, hydrogen of engine, and stream of consciousness for environmental agreement. The purpose of this study is to clarify some fundamental features of the flashing of cryogenic fluids. Experiments on flashing of liquid nitrogen were conducted to clarify the effect of surface roughness of a vessel. Two types of pressure vessel were used. One is a vessel made of stainless steel, the other is a vessel made of glass. In the case of glass vessel, many types of boiling have been observed. The degree of superheat at the start of boiling was found to depend strongly on the rate of depressurization.

Phenomena of Liquid Nitrogen Flashing under Rapid Depressurizations

“…Hanaoka [7] conducted blow down experiments for the Freons R-11 and R-113 to clarify the fundamental characteristics of the flashing under slow rate of depressurizations (0.1-2.0MPa/s) and concluded that the correlation of superheated limit of hot water in high depressurization rate examined by Alamgir and Lienhard [8] could not be applied to that of these fluids in low depressurization rate. Furthermore, the authors [9][10][11] conducted flashing experiments of liquid nitrogen from a low temperature technological point of view. These results showed that the pressure undershoots depend significantly on the rate of depressurization and initial temperature even when the depressurization rate is low.…”

Void fraction measurement in cryogenic flows. Part I: Design and validation of a void fraction capacitive sensor

“…As the boiling temperatures of cryogenic fluids are very low, various two phase flow phenomena are frequently encountered during their processes such as boiling [1], cavitation [2] and flashing [3]. Occasionally, they might lead to detrimental situations.…”