Verification Case 23
PRODUCT: AFT Fathom
TITLE: FthVerify23.fth
REFERENCE: Hydraulic Institute, Effects of Liquid Viscosity on Rotodynamic (Centrifugal and Vertical) Pump Performance, ANSI/HI 9.6.7-2010, 2010, Hydraulic Institute, Page 13
FLUID: Viscous fluid through a pump
ASSUMPTIONS: N/A
RESULTS:
| Parameter | HI Standard | AFT Fathom |
| CQ | 0.938 | 0.9381 |
| CH | 0.938 | 0.9380 |
| CE | 0.739 | 0.7388 |
| CH at 60% Flow | 0.958 | 0.9577 |
DISCUSSION:
The kinematic viscosity in centistokes (120 cSt) was converted to dynamic viscosity for use in AFT Fathom assuming a specific gravity of 0.9. This results in a viscosity of 108 cp. Discharge and suction pressures and pipes were used, with the pipe diameters made very large to minimize pressure loss.
The water flow rate and pressure difference from the problem statement were used to find an approximate CQ of 0.9395, which provides a viscous flow rate of 413.38 gal/min for the 100 percent flow case and 248.028 gal/min for the 60 percent flow case. These were used in assigned flow junctions which replaced the inlet assigned pressures for the final calculation. The pumps were redefined with the water pump curve from the problem statement, shown below, to find the final values of CQ, CH, and CE.
| Water Flow Rate (gal/min) | Water Head (ft) | Water Efficiency (Decimal) |
| 264 | 340 | 0.602 |
| 352 | 323 | 0.660 |
| 440 | 300 | 0.680 |
| 528 | 272 | 0.660 |
The correction factors, CQ, CH and CE, all correspond closely to those in the handbook. The value of CE given in the reference problem was shown as 0.738 in the calculation, but 0.739 in Table 9.6.7.4.5b. In addition, CE is calculated as 0.739 if calculated using the same numbers as given in Step 4, so it is assumed that the difference in the value given in the reference includes round-off errors.
The CQ, CH, and CE values in AFT Fathom are displayed in the Pump Summary and within the labels on the Workspace.
