Hybrid experimental/modelling methodology for identifying the convective heat transfer coefficient in cryogenic assisted machining

Cryogenic assisted machining has become a very popular method in the metal cutting industry, as it enables the cooling of a cutting zone for improving surface integrity or/and tool life without contaminating the machined part. However, the thermal interaction between liquid nitrogen (LN2) and a hot cutting zone remains unclear. The main objective of this work is to analyse the thermal phenomena occurring at the LN2 jet/workpiece interface. The nitrogen liquid/gas phase proportion has a significant influence on the heat transfer. To determine the influence of LN2 jet parameters on the convective heat transfer coefficient, a model based on the projection of an LN2 jet on a workpiece instrumented with thermocouples is proposed. The most influential parameters of the thermal distribution and heat transfer coefficient are LN2 pressure, nozzle diameter, projection angle and the distance between the nozzle and the workpiece surface.