CFD in the design of gas quenching furnace

Abstract: This thesis focuses on the numerical and theoretical studies of gas quenching in industrial furnaces. Gas quenching is the rapid cooling of metal pieces, aiming at forcing a phase transformation of the metal structure to improve its mechanical properties. The numerical methodology has been evaluated with respect to the desired accuracy and different aspects of the flow with importance for achieving an optimized process have been investigated. Initially, attention was paid to the flow and heat transfer fields both in an empty furnace and in a furnace loaded with different charges with the objective to study the influence of the charge configuration on the flow and heat transfer uniformity. This study led to the identification of several possible improvements, which are currently being implemented by the industrial partners of this project. As earlier studies had shown the importance of flow uniformity on the quality of the heat treatment, the subsequent work focused substantially on the flow uniformity upstream of the quenching zone resulting in design recommendations for the particular type of furnace under consideration. The dependence of the performance of the coolant medium on its composition was investigated theoretically and an analysis of most important parameters was carried out. Improved knowledge of the effect of gas mixture composition on heat transfer was added to the body of knowledge already available.