Combined numerical and experimental determination of the convective heat transfer coefficient between an AlCrN-coated Vanadis 4E tool and Rhenus oil

Regardless of the field of application, the reliability of numerical simulations depends on correct description of boundary conditions. In thermal simulation, determination of heat transfer coefficients is important because it varies with material properties and process conditions. This paper shows a combined experimental and numerical analysis applied for determination of the heat transfer coefficient between an AlCrN-coated Vanadis 4E tool and Rhenus LA722086 oil in an unloaded condition, i.e. without the tool being in contact with a workpiece. It is found that the heat transfer coefficient in unloaded conditions at 80 °C oil temperature is 0.15 kW/(m2·K) between the selected stamping tool and mineral oil. A sensitivity analysis of the numerical model was performed to verify the effects of mesh discretization, temperature measurement location and tool geometry. Among these parameters, mesh size and the thermocouple insert depth were identified as the critical parameters that affect the measured and calculated temperatures.