EXPERIMENTAL INVESTIGATION ON QUENCHING OF LOW THERMAL CONDUCTIVE MATERIAL COATED CRYOGENIC TRANSFER LINE

Abstract

Cryogenic fluids are frequently encountered in many applications, such as cryogenic cooling, material processing, biological tissue preservation, food engineering, aerospace field, cooling of superconducting devices and chemical process etc. It has been understood in pool quenching experiments, that the thin low thermal conductive coating layer on the wall can greatly improve the cooling performance, while less is known about flow quenching. In the present study, the experiments are to investigate cryogenic flow quenching of the horizontal stainless steel tubes with different coating layers on the inner walls. Two types of coating layers with various thicknesses were prepared with the help of paint epoxy on the inner surface of the tube. To investigate the thermo-electric property and thickness of the coating layer on the quenching performance, as compared with the uncoated and epoxy coated tube. Here we are using magnetic stirring and sonication method for coating. It is shown that a thin coating layer on the inner tube wall can significantly shorten the quenching time and enhance the heat transfer performance. To analyse the heat transfer characteristics, an inverse heat conduction equation with consideration of variable thermo-physical properties and thermal contact resistance was numerically solved to obtain the inner wall temperature and heat flux. The reason for the quenching enhancement can be attributed to the shortening of the film boiling regime of cryogenic quenching in the inner surface by the coating layer which allows the improvement of Leidenfrost point (LPF) temperature.