Sergey L. Kernazhitskiy and Gerald W. Recktenwald
Presented at the 2004 ASME Heat Transfer/Fluids Engineering Summer Conference Charlotte, North Carolina, July 11-15, 2004
Heat treating of high strength steel parts for mining equipment involves quenching the parts in a batch process in a large tank. The parts are placed on a tray that is first put into a large annealing oven, and then lowered into the quench tank. During the quench process, the quenchant is circulated by large propellers called agitators.
As a first step in understanding the flow in the quench tank, a steady, isothermal model of the turbulent flow in the tank was developed. The model includes most of the geometric complexity of the tank including the part tray. The castings are idealized as a regular array of cubic blocks 15~cm on a side.
This paper reports on two phases of quench tank modelling. The first phase involved a screening study to identify the key parameters controlling the flow in the tank. The parameters considered in this phase of the research were density of castings on the tray, the hole size and open area ratio of the tray, the presence of a screen in the quenchant flow path, the depth of the castings in the tank, the presence of a center baffle designed to redirect the flow from the agitators, and the flow rate of the agitators. A partial factorial parameter study was conducted to minimize the effort of simulating all possible combinations of design parameters. The results of the first phase of the modelling study show that the casting spacing, the agitator flow rate, and the presence of the flow-directing baffles are the dominant configuration parameters affecting the total flow and the uniformity around the castings.
The second phase of the project involved examining four new conceptual designs for the quench tank. Once again, partial factorial parameter studies were used to economize on the number of CFD simulations necessary to compare the primary features of each conceptual design. The outcome of the second phase was the identification of a promising new design that could be realized by the addition of ducting to the existing design.
The contributions of this research include a better understanding of the parameters affecting large scale batch quench processes, experience with the use of partial factorial parameter studies with CFD analysis, and the development of new directions for quench tank design. The results of this research also provides a foundation for a more complete simulation of the quench process.