CFD Loading Assessments on a Liquid Quenched Propane System

In designing propane quenching systems, a number of concerns arise with the specific fluids properties, thermal, and structural behavior of the system. In this work, the fluid-based loading on a quenched piping system is examined using computational fluid dynamics (CFD). Fluids loading is assessed during an event when a propane line is liquid quenched prior to a recycle valve opening event. During the event, hot vaporous propane is quickly exhausted into the quenched pipe. The CFD studies suggest that the loading in such an event is much larger than a similar event where the line is not quenched. Several aspects of the quench are shown to increase the loads with respect to the non-quench line, and appear to be associated with two mechanisms. The first load amplifying mechanism is the reduction of sound speed in a liquid/vapor mixture. This effect impacts the axial load in the pipe, and increases it multiple orders of magnitude as compared to a pure vapor flow. The second load increasing mechanism observed was due to slug formation. It was found that when considering quench stream droplets, stratification layers are likely to develop eventually within long pipes as the velocity from the nozzles is dissipated in the large line. In the pipe investigated, the hot, high-speed vapor blows the stratified liquid into a slug. When the slug makes turns through elbows, the pipe axial load increased even more. Simultaneously, a similar scale, perpendicular load was also observed. The overall results suggest that these loading events are not small and should be considered in the structural design and layout of a quenching system. The series of results also indicates that CFD provides a valuable tool for assessing complex two phase fluid issues, in particular for the loading on a pipe.