The Procedure of Solving the Inverse Problem for Determining Surface Heat Transfer Coefficient between Liquefied Nitrogen and Inconel 718 Workpiece in Cryogenic Machining

摘要

The determination of the cooling effect is important since the phase (liquid and gaseous) has a significant influence on the cooling effect, which indirectly influences the integrity of the machined surface after machining process. Therefore, this paper presents how the phase of liquefied nitrogen influences the surface heat transfer coefficient. The determination of the phase has been defined by resolving the inverse problem with conducted experiments and verified by the design of a numerical simulation. The experimental part includes the temperature measurement in the material (a plate of Inconel 718) at the time when the nozzle has moved across the plate, and the design of the numerical simulation. The results have shown that the surface heat transfer coefficient reaches the maximum value of 75000 W/(m(2)K) at the temperature difference (between liquefied nitrogen-Inconel 718 plate) of 196 K (liquid phase of the nitrogen). Steep value decrease for heat transfer coefficent (15000 W/(m(2)K)) at temperature difference 160 K (pure gaseous phase of the nitrogen) has been detected.