A study on the unsteady conjugate heat transfer of hot gas valve

Time step size and iteration were selected for the unsteady analysis. The analysis was conducted using only an S-A turbulent model and a valve grid. No significant difference was found. Hence, the time step size was set as 10 μs, and 50 iterations were performed. The unsteady analysis was conducted by increasing the time step size throughout the four sections considering the operating time of the hot gas valve. The time step size was increased when the quantitative result reached within 5% difference in each section. The flow, pressure, and temperature fields in the flow area reached the steady state with within 5% difference at 8 ms, 100 ms, and 5.5 s, respectively. The three fields in the flow area reached the steady state at 10 s from the operating time of the hot gas valve. However, an approximately 7% difference in temperature field was observed in the solid area. The calculation time was reduced by approximately 130 times compared to the existing calculation method.