LAUSR

Abstract Cryogenic fluid is frequently used in such fields as cryogenic cooling, food engineering and chemical process, etc. It has been understood in pool quenching experiments that a thin low-thermal-conductive coating layer on the wall can greatly improve the cooling performance, while less is known about the flow quenching. In the present study, the experiments are conducted to investigate cryogenic flow quenching of the horizontal stainless steel tubes with the Teflon coating layers on the inner wall. To explore the influence of the coating layer on the quenching performance, three Teflon coating layers of distinct thicknesses are fabricated on the inner wall of the stainless steel tubes, and the quenching efficiency and quenching heat transfer performance are compared with those of the bare tube. It is shown that the thin coating layer on the inner tube wall can significantly shorten quenching time and reduce the consumption of liquid nitrogen at different inlet pressures. The quenching time of the Teflon-coated tube is reduced by up to about 78.5%, and the maximum quenching efficiency of the Teflon-coated tube is above 50.0% compared with 8.0% of the bare tube. The improvement of quenching performance in the present study is ascribed to the fact that the sharp temperature drop of the Teflon coating layer surface upon cooled by liquid nitrogen makes the transition boiling with higher heat transfer coefficient replace film boiling at a higher average wall temperature, leading to a reduction in quenching time and an improvement in quenching efficiency.