This case study examines the findings from a comprehensive flow analysis conducted on two identical suction lines connected to VIS Breaker Bottom Pumps. The existing Bottom Pumps were slated for replacement with new models.
According to the pump supplier’s specifications, a minimum straight length of five times the diameter (5D) was required directly upstream of the suction nozzle. However, the existing system layout lacked adequate space to accommodate this straight section of pipe.
Dynaflow Research Group (DRG) was tasked with investigating the differences in flow patterns between a configuration with the required 5D straight section upstream and a configuration with a shorter upstream length. Both configurations included an inline filter positioned a few pipe diameters upstream of the pump nozzle. For this analysis, DRG modeled the two flow configurations and conducted a detailed Computational Fluid Dynamics (CFD) analysis.
CFD Flow Analysis
Analysis Overview
DRG carried out a CFD analysis to simulate the flow patterns within a pipeline section approximately four meters long, upstream of the pump. This section comprised a 10-inch horizontal pipe, an elbow leading to a vertical section, a gate valve, a filter, and a 10×8-inch reducer. Additionally, three small-diameter branches (2 inches or smaller) were present in the vertical section of the model. Various models were developed to assess the impact of the extended straight pipe section on the flow characteristics at the pump suction nozzle.
Key Findings
The CFD analysis revealed that the radial velocity components induced by the filter generated two vortical flow structures downstream of the filter. While the presence of a 5D straight section had a minimal effect on these vortices, it significantly reduced the flow variations across different cross-sectional quadrants to acceptable levels. In the absence of the filter, the flow pattern was laminar with minimal velocity differences across the channel’s cross-section.
To address the disturbances in the flow field caused by the filter, DRG proposed two potential solutions:
- Reducing Pressure Drop: Utilize a filter with a lower mesh density to decrease pressure drop across the filter.
- Modifying Filter Geometry: Alter the filter design to prevent radial flow post-filter, thereby enhancing flow uniformity.
By optimizing these factors, the overall flow performance in the suction lines can be improved, ensuring better pump operation and efficiency.
