Modeling and optimization of coolant channel cross sections in induction heating coils

Abstract

In induction heating applications where high currents and intermittent power application dominate, thermal fatigue can be a limiting factor of the service life of the induction coil. The outer geometry of the coil is often set by the application, hence the temperature in the cross section has to be affected by the inner shape of the coil, coolant velocity, and thermal properties of the coolant. In this paper a model for estimating the temperature of the cross section is presented. The model is also applied to an optimization problem where a high power loss, copper region is surrounding a wedge shaped cooling channel. The point of the wedge was replaced by a radius that was optimized. The optimum was considered where the thermal fatigue service life is maximized, i.e. where the peak deviation from mean temperature in the cross section was at a minimum. The results show that the optimum corner radius is very small, typically 0.3-0.5 mm.