Design Inputs
Units: US Customary
Affects density, viscosity, and the flow from load constant.
Used for property lookups and vapor pressure in NPSH.
Typical values: 10–30°F depending on application.
Closed loops often ignore static; leave 0 unless applicable.
Coils, control valves, strainers. Enter known drop in feet.
Pipe Segments
| # | Material | Diameter (in) | Length (ft) | Fitting K-sum |
|---|
Fitting K quick guide:
Std 90° elbow ≈ 0.75
Long‑radius elbow ≈ 0.2
Tee through ≈ 0.6
Tee branch ≈ 1.8
Globe valve ≈ 10
Gate valve open ≈ 0.2
Results
Enter inputs and click Calculate.
Key Assumptions
- Darcy–Weisbach used for friction; Swamee‑Jain for turbulent friction factor.
- Minor losses modeled via total K for each segment.
- Head in feet of liquid. Brake HP by
HP = Q·H / (3960·η). - Closed loop: static head often cancels; elevation optional.
- Flow from load uses
GPM = Load / (Kfluid · ΔT).
This tool is for preliminary sizing. Verify with manufacturer pump curves and local codes.
Formulas Used
Flow from Heat Load
For a chosen fluid at temperature:
GPM = Load [BTU/hr] / (Kfluid · ΔT [°F])
Where Kfluid = 60 · ρ · cp / 1055 adjusted to BTU units; typical water constant is about 500.
Head Loss per Segment
hf = f · (L/D) · (v² / 2g) (friction) hm = K · (v² / 2g) (minors) Total = (hf + hm) · 3.28084 (ft)
Swamee‑Jain: f = 0.25 / [log10(ε/(3.7D) + 5.74/Re^0.9)]², Re = ρ·v·D/μ.
Pump Power
HP = (Qgpm · Hft) / (3960 · η)
Add a margin to H as desired. Check motor size and service factor per catalog.
NPSH (Optional Check)
NPSHa ≈ Patm(ft) + hstatic − hvapor − hloss,suction
Compare NPSHa to pump NPSHr at duty flow. Suction losses can be estimated with the same method using suction piping.
How to Use
- Select the working fluid and fluid temperature.
- Choose whether to compute flow from a heat load and ΔT, or enter a design flow directly.
- Add pipe segments for each diameter and material. Include an approximate sum of K for fittings on each segment.
- Enter additional drops for coils/valves and any elevation if applicable.
- Click Calculate to get total head, recommended pump HP, and velocity/Reynolds checks.
- Export results using CSV or PDF for records and share with vendors to select a pump curve.
Example Data
| Fluid | Temp (°F) | Load (BTU/hr) | ΔT (°F) | Segments | Extras (ft) |
|---|---|---|---|---|---|
| Water | 140 | 50,000 | 20 | 1" Copper 200 ft (K=3.0); 0.75" Copper 40 ft (K=2.0) | Coil drop 5 ft |
Click Load Example to populate the form and run the calculation.
FAQs
Often no, because static head cancels between supply and return; the pump only overcomes dynamic losses. Include elevation if there is a free surface or unbalanced leg that the pump must lift.
Glycol raises viscosity and slightly changes density and heat capacity, increasing head for a given flow and requiring more flow for the same heat transfer at a given ΔT.
Hazen‑Williams is common for water but does not account for viscosity or Reynolds number. Darcy–Weisbach is more general and preferred here for accuracy across fluids and temperatures.
Typical guidelines: 2–4 ft/s in comfort hydronics to limit noise and erosion; higher velocities are sometimes acceptable in short runs or industrial service. Check project standards.
Use the duty point (GPM, ft) with manufacturer pump curves. Prefer models where the operating point sits near the best efficiency island and provides some margin for fouling.
Yes—enter them as Additional Drops in feet. If a drop is in psi, convert using approximately 2.31 ft per psi for water near room temperature.
| Metric | Value | Units |
|---|