Experimental investigation on line chill-down process by liquid argon

Abstract

The cryogenic line chill-down process is an essential part of the cryogenic system application. As the heat transfer characteristics during the transient cooling down are highly affected by the fluid properties, universal heat transfer correlations, which are valid for the chill-down process with various kinds of cryogenic fluid, are required in many industries. This paper investigates cryogenic line chill-down process by using a 7 m long stainless steel horizontal pipe. Liquid argon is selected as the working fluid to examine the fluid property effects. The histories of the wall temperature, pressure, and mass flow rate are measured during the chill-down process. The heat transfer characteristics of liquid argon are analyzed and compared with those of chill-down process with liquid nitrogen. At the same time, the empirical correlations for the critical heat flux, critical heat flux temperature, and minimum heat flux temperature, which can well estimate the parameters for both of liquid nitrogen and liquid argon cases, are suggested. As a result, the critical heat flux is estimated with the mean absolute error (MAE) of 14.8%. The critical heat flux temperature and minimum heat flux temperature are predicted with the MAE of 3.4% and 1.9%, respectively. The empirical correlations are essential to construct a numerical model for simulating the cryogenic line chill-down process.