FluidTech Suite/Viscosity and temperature

FT-01 · Transport properties

Virtual viscometer: Saybolt ↔ cSt ↔ cP

Converts a Saybolt Universal reading, adjusts for density and builds the log–log kinematic viscosity curve from two experimental points.

Fluid data and calibration points

Temperature T₁ · Saybolt reading T₁ · s SUSApproximate ASTM correlation, SUS ≥ 32 s Temperature T₂ · Viscosidad ν₂ · cSt Target temperature · Density at 15 °C · Thermal expansion α · Walther correction · cTypical value for mineral oils

ν at the target temperature

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Kinematic viscosity

Equivalente Saybolt

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Segundos universales

Dynamic viscosity

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μ = νρ

Corrected density

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Linear volumetric model

Walther A

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Walther B

—

ν₁ from SUS

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Inlet condition

Valid

ASTM D341 curve · logarithmic axes

Modelo aplicado

\[\log_{10}\!\left[\log_{10}(\nu+c)\right]=A-B\log_{10}(T_K)\]

\[\mu\,[\mathrm{cP}]=\nu\,[\mathrm{cSt}]\,\rho\,[\mathrm{kg/m^3}]/1000\]

The Saybolt conversion uses two empirical branches. The curve needs two distinct temperatures and viscosities above the mathematical limit of the model.

FluidTech calculation directory

Ten more modules connected by the same SI/USCS unit system.

FT-02 · HYDROSTATICS

Differential manometer

ΔP, column height and gauge fluids.

Open module →FT-03 · COMPUERTAS

Hydrostatic force

Resultant force and centre of pressure.

Open module →FT-04 · BUOYANCY

Metacentric height

Buoyancy, GM and righting moment.

Open module →FT-05 · FLUJO INTERNO

Pipes in series

Darcy–Weisbach, HGL and EGL.

Open module →FT-06 · REDES

Pipes in parallel

Flow split between branches.

Open module →FT-07 · BOMBAS

Centrifugal selection

Affinity laws, Ns and operating curve.

Open module →FT-08 · MANNING

Open channels

Flow rate, section and Froude number.

Open module →FT-09 · MOMENTUM

Jet impact

Vector force on deflectors.

Open module →FT-10 · PARTICLES

Drag and lift

Cd, Cl and terminal velocity.

Open module →FT-11 · HVAC

Air ducts

Section, friction, noise and insulation.

Open module →

Saybolt to centistokes calculator with temperature correction

Kinematic viscosity is the resistance to flow divided by density. Saybolt viscometers report the efflux time in SUS seconds; empirical correlations convert that reading to centistokes before the temperature correction is applied.

Saybolt conversion equations

Rango	Approximate conversion	Uso
32–100 SUS	ν = 0.226S − 195/S	Low to medium viscosity fluids
>100 SUS	ν = 0.220S − 135/S	More viscous oils
Dynamic	μ(cP) = ν(cSt)ρ/1000	Requires density at the target temperature

Viscosity vs. temperature per ASTM D341

The Walther equation linearises a strongly non-linear relationship through a double logarithmic transformation. Two experimental points fix A and B; interpolation is normally more reliable than extrapolation.

Preguntas frecuentes

Are cSt and cP equivalent?

No. cSt measures kinematic viscosity and cP dynamic viscosity. Density links the two.

Can I use two different products as the two points?

No. Both points must come from the same product under comparable conditions.

Why does the Saybolt reading change with temperature?

As temperature rises, most liquids become less viscous and take less time to discharge.