Justification of RELAP5 code for modeling water hammer phenomenon by employing the umsicht test facility data

摘要

The rapid closing or opening of a valve causes pressure transients in pipelines. The phenomenon is known as a water hammer. The valve closure can result in pressures well over the steady state values, while the valve opening can cause such low pressures that the flowing liquid vaporizes inside the pipe. If the pressure induced exceeds the pressure range of a pipe given by the manufacturer, the pipe may rupture. This unsteady state phenomenon deals with the change between the kinetic and potential energies, which may be positive or negative. In the paper, the capabilities of the RELAP5 code to correctly represent the water hammer phenomenon are shown. The paper presents a comparison of RELAP5 calculated and measured at UMSICHT test facility water hammer values at various water velocities after a fast closure of a valve. The influence of the calculation time step and control volume sizes in pipe components on the computation results is presented as well. The analysis showed that the RELAP5-calculated first pressure peak matches the measured value of pressure very well, but concerning the following pressure peaks the measured pressures are higher and peaks appear with an accumulating time delay. A comparison of UMSICHT test facility experimental results to RELAP5, MONA and FLOWMASTER calculation results is presented as well.