Does this recommend a safe pipe velocity?

No. It calculates mean velocity but does not evaluate pressure loss, noise, erosion, cavitation, surge or design acceptability.

Which diameter should be entered?

Enter the actual internal flow diameter at the assessed condition, not DN/NPS or outside diameter.

When is Reynolds number calculated?

Only when a positive documented kinematic viscosity for the same fluid and state is entered.

Do the displayed Reynolds bands prove the observed regime?

No. They are conventional straight circular-pipe screening ranges; transition depends on disturbances, entrance conditions, roughness and the actual system.

Same-state circular-pipe arithmetic

Actual-ID Pipe Mean-Velocity and Reynolds Arithmetic

Calculate cross-sectional mean velocity from actual volumetric flow and actual circular inside diameter. Add documented same-state kinematic viscosity only when a Reynolds-number screen is required.

Actual ID onlyOptional Reynolds numberNo safe-velocity grade

Cross-sectional mean velocity v̄

—

Diameter Reynolds number ReD

—

Conventional straight-pipe screen

—

Circular flow area

—

Contained volume per length

—

Arithmetic only.

A=πD²/4; v̄=Q/A=4Q/(πD²); ReD=v̄D/ν

Q is actual volumetric flow [m³/s],D is actual internal flow diameter [m],v̄ is cross-sectional mean velocity [m/s],and ν is same-state kinematic viscosity [m²/s].ReD is dimensionless.This is general engineering arithmetic,not an ISO sizing or acceptance formula.

Optional conventional Reynolds screen

When ν is supplied,the worksheet reports ReD and labels ReD<2300 as below the conventional transition screen,2300–4000 as the conventional transition interval,and ReD>4000 as above it for internal circular-pipe flow.These are screening ranges,not proof of the instantaneous flow state;transition depends on inlet disturbances,roughness,geometry,vibration and development length.

Exact conversions

1L=10⁻³m³;1h=3600s;1min=60s;1in=0.0254m exactly;1ft=0.3048m exactly;1USgal=231in³=0.003785411784m³ exactly;1cSt=1mm²/s=10⁻⁶m²/s.

Not a design verdict: no recommended velocity band,oversized-pipe diagnosis,pressure drop,noise,vibration,erosion,cavitation,surge,heat transfer or fitness decision is generated.

资料来源

University of Dayton flow-rate/velocity relation; University of Iowa pipe-flow Reynolds definition and conventional bands; Princeton transition-disturbance qualification; NIST exact international inch.