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

Abstract

This paper describes a novel method of utilizing adsorption to a no-vent fill (NVF) process. A primary goal of the NVF process is to complete the fill process of cryogenic liquid within the allowable pressure of the receiver tank without venting. 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 vapor at a high density. To prove the effects of adsorption on NVF, we conduct experimental tests of NVF processes of liquid nitrogen (LN2) using adsorption on activated carbon. The experimental apparatus used in tests consists of a 158 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 precooled by a Stirling cryocooler before the NVF process starts. When the adsorption inlet valve is opened at 48 s, the peak pressure reduction of 3.2 kPa is proved experimentally in the sorption-assisted NVF process. Furthermore, a numerical model for the sorption-assisted NVF is established to investigate the adsorption-related parameters that affect NVF processes. The numerical model is developed by dividing it into NVF and adsorption models and is validated by comparing the predicted tank pressure and filling ratio with the measured data. For four experimental cases, the absolute error of the filling ratio is within 3.3 %, and the absolute error of the pressure is within 10.8 kPa. From numerical simulations, we identify four adsorption parameters: valve opening time, volume ratio of activated carbon and copper, adsorption tank volume, and valve opening degree. The simulation results demonstrate the applicability of adsorption effects for the NVF process.