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This paper is the second of a two-part series that presents experimental data and analysis on the liquid nitrogen quenching heat transfer process of a stainless-steel tube with an inner surface low-thermal conductivity thin-film coating. This paper focuses on the effects of different flow directions and two tube wall thicknesses. Additionally, this paper also provides an analysis on the chilldown thermal efficiency of the quenching process. Three flow directions with four different inner surface coating modifications, and three tube wall thicknesses were examined. The experimental data covers the Reynolds numbers ranging from 3500 to 140,000. The chilldown efficiency, along with chilldown time and LN 2 (liquid nitrogen) mass consumption were analyzed to assess the overall performance of the LN 2 line chilldown process. For thin tube wall cases, the chilldown efficiencies cover a range between 3% and 41%, and the maximum chilldown efficiency value is found for the tube with 3 L coating at Re = 5278 in the vertical up flow direction. For thick wall tube cases, the efficiencies cover a range between 4% and 52%, and the maximum chilldown efficiency value was found for the tube with 4 L coating at Re = 5308 in the vertical up flow direction. [ABSTRACT FROM AUTHOR]

This paper is the first of a two-part series that presents experimental data and analysis on the liquid nitrogen quenching heat transfer process of a stainless-steel tube with an inner surface low-thermal conductivity thin-film coating. The experimental data covers a wide range of flow mass fluxes (43 to 1077 kg/m2s). The experiments were conducted using test tubes with four different coating thicknesses to investigate the effects of various Teflon coating thicknesses. An analysis of the chilldown time and LN 2 mass consumption data are presented to evaluate the effects of the flow mass flux, axial distance from the tube inlet, and coating layer thickness. The chilldown time decreases with increasing flow Re. However, the chilldown mass consumption increases with increasing flow Re. In general, the larger the flow Reynolds number, the lower the percentage reduction in chilldown time is observed. For the percentage reduction in the chilldown time by the coating, the minimum is 27.8% for the tube with 7-layer coating at flow of Re = 100,000 and the maximum is 61.3% for the tube with 14-layer coating at flow of Re = 10,000. The percentage reduction in mass consumption due to coating falls in the range between 35.3% and 54.1%. [ABSTRACT FROM AUTHOR]