Experimental and numerical investigation on heat transfer characteristics of cryogenic line chill-down process

Abstract

This research focuses on the transient process of the pipe cooling by the internal flow of cryogenic fluid, which is a so-called cryogenic line chill-down process. We extended the quenching database with various cryogenic fluids and developed the heat transfer correlations for predicting the cryogenic line chill-down process. The line chill-down experiments are carried out on a 12.7 mm outer diameter, 7 m long horizontal pipe with liquid nitrogen, liquid argon, and liquid oxygen. Based on the experimental data, the empirical correlations for some important parameters, such as the critical heat flux (CHF), the CHF temperature, and the minimum heat flux (MHF) temperature are developed. The calculation results predict the experimental data with the mean absolute error of 20.1%, 3.6%, and 2.3%, respectively. Additionally, a one-dimensioned homogeneous model is established to simulate the chill-down process, and the correlations for heat transfer coefficient (HTC) are developed for single-phase vapor heat transfer regime and film boiling regime. The empirical correlations are validated by simulating the line chill-down process with LN2, LAr, and LOX in mass flux range from 15 to 868 kg/$m^2s$ and predicting the line chill-down time within 10% error.