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.

低温流体常用于低温冷却、食品工程和化学加工等领域。 在池淬火实验中了解到，壁上薄薄的低导热涂层可以大大提高冷却性能，而较少已知关于流动淬火。在本研究中，进行实验以研究内壁具有特氟龙涂层的水平不锈钢管的低温流动淬火。为探究涂层对淬火性能的影响，在不锈钢管内壁制作了三层不同厚度的特氟龙涂层，并与裸管进行了淬火效率和淬火传热性能的比较。结果表明，内管壁上的薄涂层可以显着缩短淬火时间，减少不同入口压力下液氮的消耗。特氟龙涂层管的淬火时间减少了约78.5%，与裸管的8.0%相比，特氟龙涂层管的最大淬火效率在50.0%以上。本研究中淬火性能的提高归因于特氟龙涂层表面在液氮冷却后温度急剧下降，使得具有较高传热系数的过渡沸腾取代了较高平均壁温下的薄膜沸腾，导致缩短淬火时间，提高淬火效率。