Modelling of an electric IR heater at transient and steady state conditions: Part II: modelling a paper dryer

A model for an electric infrared (IR) paper dryer has been developed. The model includes non-grey radiative heat transfer between the different parts of the IR heater, as well as conduction in reflector material and convective cooling of surfaces. Such heat transfer calculations are combined with energy balances to provide a system of equations that simulates the behaviour of an electric IR dryer. Using IR module voltage as the only input, the model predicts the temperature of dryer components and cooling air, as well as the net radiation heat transfer to the paper sheet at steady state and transient conditions. The model has been used to investigate trends in efficiency and component temperature with changing voltage and paper grade. Emphasis has been on back reflector temperature and dryer efficiency. Also, the transients during start-up of an IR paper dryer have been investigated. The study indicates that the transients of the back reflector is important for the time needed to reach steady state heat flux at the paper sheet.