Experimental and numerical investigation of cryogenic no-vent fill (NVF) process using adsorption on activated carbon

Abstract

Recently, the importance of a no-vent fill (NVF) has been increasing as an efficient method for cryogenic liquid filling. The primary goal of the cryogenic NVF process is to complete the fill process of cryogenic liquid at a pressure lower than the allowable pressure of the receiver tank without venting. For the tank with low allowable pressure, the tank pressure should be controlled not to exceed the allowable pressure. One of the methods to deal with this issue is to apply physical adsorption to the NVF process. The use of physical adsorption at cryogenic temperature can suppress the pressure rise of the tank and facilitate the NVF process by adsorbing and storing the gas inside the tank at a high density. In this paper, we conduct the experimental tests of NVF processes of liquid nitrogen (LN2) using cryogenic adsorption storage on activated carbon. The experimental apparatus used in tests consists of a 159 L receiver tank, a 180 L supply tank, an LN2 transfer line, and an adsorption storage system. The adsorption storage system, which has a volume of 2.2 L and contains 833 g of granular activated carbon, is pre-cooled by a Stirling cryocooler before the NVF process starts. In the experimental tests, we achieve a higher filling ratio by using the pre-cooled adsorption system. The effects of adsorption according to each fill configuration are experimentally investigated to analyze cryogenic adsorption and its influence on the tank pressure. In addition, a numerical model for the transient analysis of the thermodynamics and heat transfer is established to predict the tank pressure during the NVF and adsorption processes. The numerical model is verified by comparing the calculated tank pressure and liquid level with the experimental data. The experimental and numerical results demonstrate the practical applicability of the adsorption for the NVF process.