Mathematical modelling and simulation of thermal regenerators including solid radial conduction effects

Increasing combustion fuels costs, depletion of fossil fuel reserves, and necessity to control environmental emissions, showing the importance of industrial heat recovery. For this purpose, different types of heat recovery systems have been designed and built. One of the most industrial applicable systems is a thermal regenerator that has widespread applications in energy industries such as glass, aluminium, and power plants. In aluminium and glass melting furnaces such system can be applied to preheat combustion air by absorbing heat from flue gases that results considerable fuel saving in the furnace. Due to the high temperature application of such systems, the packing must be constructed from low conductivity ceramic materials and the mechanism of heat transfer will be convection and radial conduction inside the solids. This paper presents the results of the mathematical modelling and simulation studies of a regenerator filled with spherical shape packing made from alumina with different diameters. For the modelling purposes two mathematical models have been considered; simplest convection model and more complex radial conduction model inside the packing particles. For the evaluation of the model and to study the effect of different parameters such as gas mass flow rate, period time and ball diameter on the performance of the system, an experimental setup has been designed and built. The results clearly show that decreasing of gas mass flow rate, period time and packing diameter increase the system efficiency. Finally, a simulation software package has been developed and used for the prediction of output parameters in two industrial cases and excellent agreement has been obtained that proves the accuracy of the model for the high temperature applications.