Transient thermal analysis of a kiln using different numerical approaches by means of CFD

Abstract

A transient study for the prediction of the temperature of hot gases inside a kiln loaded with bricks, using Computational Fluid Dynamics (CFD), is presented in this work. The prediction of transient thermal performance is obtained through four different approaches: the Properties Fitted to Temperature Polynomials (PFTP) model, the density changes according to the Boussinesq Approximation (BA) model with a Constant Thermal Expansion Coefficient (CTEC), the BA model with a Variable Thermal Expansion Coefficient (VTEC) and the density changes according to the Ideal Gas Law (IGL) model. Furthermore, the effects of a layer of ceramic fiber as insulation are investigated. The numerical results of the transient temperature of the hot gases inside the kiln were validated with experimental data. The mean relative error of the transient temperature was 5.0 %, 32.6 %, 26.4 % and 4.4 % for the PFTP model, BA model with a CTEC, BA model with a VTEC and IGL model, respectively. It was concluded that IGL model is the best approach to predict the transient temperature of the kiln. Finally, an increase in the temperature of the hot gases of 12.7 % was obtained by applying the IGL model and using a layer of 0.07 m of ceramic fiber as insulation. The results of this work could be helpful to improve the design and performance of kilns in further works.

Keywords

• Transient state
• Thermal analysis
• Brick kiln
• Numerical models
• CFD