Experimental investigation on cryogenic quenching enhancement with turbulent film boiling

Abstract

This study aims to evaluate the impact of wire-coil inserts on cryogenic line chilldown performance. Quenching experiments are conducted on a stainless-steel tube with a length of 650 mm using liquid nitrogen. Tubes with wire-coil inserts of varying pitches (5, 8, 10, 12, and 15 mm) are tested against a bare tube. Temperature, mass flow rate, and pressure are measured under vertical upward flow conditions across a wide range of Reynolds numbers. Experimental results show that wire-coils effectively enhance heat transfer during chilldown, reducing chilldown time by up to 75.9 % compared to the bare tube. This is attributed to coil-induced turbulence and fluid mixing near the tube wall, which lead to a turbulent film boiling regime with a higher heat transfer coefficient. As a result, tubes with inserts achieve a chilldown efficiency of up to 30 %, whereas that of the bare tube remains below 10 %. Notably, this superior performance is observed for tubes with inserts, regardless of wire-coil pitch or inlet conditions. These findings provide a guideline for optimizing the chilldown process: using a wire-coil insert with a larger pitch under low Reynolds number conditions is recommended to optimize heat transfer, minimize pressure drop, and achieve substantial savings in cryogen mass consumed during chilldown.