Velocity from the initial pipe area.
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05 / Fluid systems & engineering economics
Piping & Pumping System Design
Move the fluid. Balance the cost.
A coolant-transfer design that connects hydraulic demand, pump selection and the cost of pipe diameter—and examines where the calculation needs more evidence.
The decision
Size the hydraulic duty first, then compare the energy and material costs of alternative diameters.
The evidence
A three-person academic calculation study; system-curve data and source limitations made explicit.
Coolant transfer / explanatory schematic 50% glycol–water
5 L/s
Design flow
100 m
Total pipe length
10 m
Static lift
16.37 m
Calculated head · initial pipe size
1.52 kW
Estimated pump shaft / motor-output requirement
3 inch
Report’s final nominal pipe recommendation*
Design of Thermal Fluids · King Saud University · report pp. 8, 13 and 20. *The economic recommendation is qualified below; the selected pump was assessed for the initial 2½-inch design.
01 / Set the duty
One flow requirement.
Several connected decisions.
Transfer 5 litres of coolant every second through 100 metres of carbon-steel pipe, with a 10-metre rise between two atmospheric reservoirs.
Our three-person team worked from the fluid properties and fitting inventory to select an initial pipe, calculate losses, choose a pump and examine the economics of other diameters. This was a calculation-based course project, not a commissioned system.
- Fluid
- 50% ethylene glycol–water
- Density / viscosity
- 1,080 kg/m³ / 0.005 Pa·s
- Pipe roughness
- 0.045 mm
- Initial pipe
-
2½-inch nominal, Schedule 40
62.71 mm internal diameter
Source: pp. 3–6. Fluid-property values are the report’s inputs; their temperature basis is not specified.
02 / Build the hydraulic requirement
The lift is only
part of the load.
Static elevation, pipe friction and fitting losses all contribute to the required head. An independent arithmetic check reproduces the headline result.
10.00 m Static elevation 5.75 m Pipe friction
Fittings add 0.62 m
10 + 5.75 + 0.62 ≈ 16.37 m
Reynolds number; turbulent flow.
Darcy factor from the Moody chart; ΣK = 4.65.
Hydraulic power, before efficiency losses.
Report pp. 7–9. Budget values independently recomputed from the stated inputs and rounded. The report’s rounded area produces a slightly different Reynolds number in Table 3.
Hydraulic demand
The system sets the head.
Required head
Source: report p. 9, Table 3. All 12 calculated points preserved; straight segments connect samples. Friction factors were read individually from a Moody chart. Dashed horizontal line: 10 m static lift.
View the underlying system-curve data
| Flow / L/s | Velocity / m/s | Re | f | Head / m |
|---|---|---|---|---|
| 1 | 0.323729362 | 4385.030754 | 0.041 | 10.37406855 |
| 2 | 0.647458725 | 8770.061509 | 0.033 | 11.22370403 |
| 3 | 0.971188087 | 13155.09226 | 0.0305 | 12.56168315 |
| 3.5 | 1.133052768 | 15347.60764 | 0.0285 | 13.27804885 |
| 4 | 1.294917449 | 17540.12302 | 0.028 | 14.21339064 |
| 5 | 1.618646811 | 21925.15377 | 0.027 | 16.37047742 |
| 5.5 | 1.780511492 | 24117.66915 | 0.0262 | 17.50214647 |
| 6 | 1.942376174 | 26310.18453 | 0.0255 | 18.71352529 |
| 7 | 2.266105536 | 30695.21528 | 0.025 | 21.65138954 |
| 7.5 | 2.427970217 | 32887.73066 | 0.0248 | 23.27949417 |
| 8 | 2.589834898 | 35080.24603 | 0.0245 | 24.94557125 |
| 8.5 | 2.751699579 | 37272.76141 | 0.024 | 26.56444261 |
03 / Select against the duty
Read the intersection.
Then check the power.
The report overlays the system curve on a centrifugal-pump performance chart at 1,750 rpm. Near the design flow of 80 US gpm, it identifies an approximately 180 mm impeller.
1,750rpm
≈180mm impeller
≈57%efficiency
The 57% efficiency estimate comes from the selection chart on p. 12. Dividing 867 W by that efficiency gives about 1.52 kW at the pump shaft. Motor efficiency and sizing margin are not included.
Original annotated figure retained because complete manufacturer curve data are not tabulated. No invented performance curve or new operating point is added.
04 / Check the suction side
Placement is a
design constraint.
The report obtains a maximum suction lift of approximately 0.67 m. It is a conditional calculation, not an installation clearance proven safe.
0.76 m required NPSH
1.00 m assumed margin
1.76 m target available NPSH
The calculation uses 101.325 kPa atmospheric pressure and 6.666 kPa vapor pressure at 100°C. However, it applies the full 100 m pipe length and all fitting losses to the suction side, and reads a glycol vapor-pressure chart without establishing the 50% mixture’s value.
Before specifying pump elevation, the suction-only layout, mixture properties and operating temperature must be established. The 0.67 m result should not be reused as a general cavitation limit.
Source: report pp. 13–15. NPSHr ≈ 2.5 ft (0.76 m), read from the original pump chart.
05 / Compare the trade-off
Spend more on pipe.
Less on pumping.
The useful finding is the competing trend. The cost period and model assumptions determine what “economic” actually means.
Economic comparison
A larger pipe changes the balance.
Pipe + one year’s energy Pipe cost · one-off Energy · annual
Source: report p. 19, Table 6. All seven samples preserved. Combined cost adds pipe capital to one year of energy; it is not a 15-year life-cycle cost. The table’s 62.71 mm energy value differs from p. 17.
View the underlying cost data
| ID / mm | Pipe · once | Energy · annual | Combined |
|---|---|---|---|
| 49.26 | 797.8933 | 1278.620457 | 2076.514 |
| 52.52 | 850.6974 | 1044.923531 | 1895.621 |
| 53.97 | 874.1839 | 965.9044944 | 1840.088 |
| 58.42 | 946.2632 | 788.0894612 | 1734.353 |
| 59.01 | 955.8198 | 770.1025962 | 1725.922 |
| 62.71 | 1015.751 | 678.3399548 | 1694.091 |
| 66.64 | 1079.407 | 610.3375013 | 1689.745 |
One year, not fifteen.
The displayed sum combines pipe cost with a single year of pumping energy. At 62.71 mm it reports $678.34/year, versus $713.94/year in the earlier energy calculation. That difference remains unresolved.
$11,724.85 over 15 years.
The report separately calculates $1,015.75 + 15 × $713.94. This is an undiscounted pipe-and-energy sum, excluding pump purchase, installation, maintenance and replacement costs.
Study assumptions: 8,000 operating hours/year; 0.22 SAR/kWh, converted in the report to 0.05866 USD/kWh; 57% efficiency. Historical assumptions, not a current quotation or tariff.
06 / The recommendation
A standard size.
A qualified choice.
The report moves from an initial 2½-inch Schedule 40 design to a final 3-inch Schedule 40 recommendation after reporting a theoretical economic diameter of 64.45 mm.
That is a conceptual recommendation. The displayed optimization uses one year of energy, fixed friction and simplified linear pipe pricing. Its final 3-inch Schedule 40 choice is not one of the tabulated comparison points.
2½″Initial design
3″Recommended
Nominal sizes · illustrative comparison, not a scale drawing
07 / Engineering review
Know what the model
does—and does not—prove.
The calculations tell a useful design story. Reviewing their assumptions is part of that story, rather than evidence of a built or validated pumping system.
Reproducible hydraulic duty
Using D = 0.06271 m, Q = 0.005 m³/s, f = 0.027 and ΣK = 4.65 independently gives 16.372 m head and 867.29 W hydraulic power. These agree with the report’s rounded 16.37 m and 867.18 W. The original Table 3 values remain unchanged in the chart.
Cost model and optimum need reconciliation
Table 6 is a first-year combined-cost comparison, despite the conclusion’s life-cycle wording. The table’s energy value does not reproduce the earlier design-point calculation. The 64.45 mm optimum is reported, not independently validated, and the tabulated IDs include schedules other than 40 despite later wording. A smaller economic diameter alone does not prove that the required flow cannot be delivered.
The pipe-price reference numbering also needs correction. The stated 1,177 USD/ton and 8.63 kg/m give 10.15751 USD/m and 1,015.751 USD for 100 m; the intermediate printed unit price differs slightly. A final selection needs a consistent cost period, schedule-specific prices and a revised pump/system intersection.
The vibration check has a dimensional error
On p. 10, fLV²/(2gD) is head in metres, but the report labels its ≈57.44 result as kPa. Multiplying by ρg gives approximately 609 kPa per 1,000 m using the stated inputs. This does not support the report’s claim that the pressure loss is far below its cited 557–679 kPa range. No verified low-noise or vibration result is claimed here.
Cavitation is conditional on the suction layout
The 0.67 m lift result uses full-system losses on the suction side and an unverified mixture vapor-pressure assumption. Suction pipe lengths, fittings, fluid properties and temperature need to be reconciled before an installation recommendation.
The takeaway
Connect the calculation
to the decision.
This project brought hydraulic sizing, pump selection and engineering economics into one design process. It strengthened my ability to work within a team, compare alternatives and recognize when a plausible result still depends on unresolved assumptions.
Source: the complete 23-page course report. Shared team work; no unverified individual attribution, physical construction or experimental performance is claimed. Original reports and student identifiers are not published.