A simplified model for minor and major loop magnetic hysteresis and its application for inference of temperature in induction heated particle beds

Abstract

In this work, a LangArc model is presented that successfully fits both major and minor hysteresis loops of a bed of magnetic particles in real time using instruments that detect changes in the magnetic field strength, such as in-situ pick-up coils. A novel temperature measurement application is demonstrated based on a real-time characterisation of a magnetic material, in this case magnetite, as a function of temperature. Magnetic hysteresis can be used to provide useful induction heating in a packed bed of magnetic materials. This can be used for general heating and to provide energy to chemical reactions in chemical processes. Accurate temperature measurement of magnetic particles under induction heating is a well-known challenge: conventional techniques give a single-point measurement, and are subject to inaccuracy due to self-heating of the instrument tip. Thermal lag can be problematic given the rapid heating rates that are characteristic of induction heating. The LangArc inferred temperature measurement technique is shown to detect heating rates in excess of 30 °C·s-1, under which circumstances an in-bed thermocouple was shown to lag by as much as 180 °C. This new method has significant importance for temperature measurement in applications involving the induction heating of magnetic materials as it avoids the location of an instrument inside the magnetic particle bed and is highly responsive under rapid heating where other techniques can give misleading results.