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SimuPipe

Fluid Properties Table

Density, viscosity, and related properties for common engineering fluids, used in pipe flow, pressure-drop, and pump calculations. Liquids are at 20 °C; gases at 20 °C and 1 atm (saturated steam at 100 °C). Values come from CoolProp, IAPWS-IF97, and standard handbooks — the same data SimuPipe's solver uses.

Liquids (at 20 °C)
FluidDensity ρ (kg/m³)Dyn. visc μ (cP)Kin. visc ν (cSt)Vapor press. (kPa abs)Crit. press. (bar)
Water (IAPWS-IF97)998.21.0021.0042.338220.6
Seawater (20°C)10251.081.0542.338220.6
Ethanol (20°C)789.41.1941.5135.9561.48
Methanol (20°C)7910.5850.739612.980.84
Ethylene Glycol (20°C)111316.114.470.007977
Propylene Glycol (20°C)10364240.540.010661
Glycerin (20°C)1261141211202.00e-566.8
Gasoline (20°C)7490.460.61425325
Diesel Fuel (20°C)8322.42.8850.001321
Kerosene (20°C)8101.61.9755.00e-422
Crude Oil (20°C)8701011.490.00520
Hydraulic Oil ISO 32 (20°C)8603237.210.00120
SAE 10 Oil (20°C)8706574.710.00120
SAE 30 Oil (20°C)876290331.10.00120
SAE 70 Oil (20°C)891150016840.00120

1 cP = 0.001 Pa·s; 1 cSt = 1 mm²/s. Vapor and critical pressures are absolute. Water uses IAPWS-IF97; other liquids use CoolProp or handbook values.

Gases (at 20 °C, 1 atm)
GasDensity ρ (kg/m³)Dyn. visc μ (µPa·s)Molar mass M (g/mol)γ (Cₚ/Cᵥ)R (J/kg·K)
Air (20°C, 1 atm)1.20518.2128.961.402287.1
Nitrogen (20°C, 1 atm)1.16517.5728.011.401296.8
Oxygen (20°C, 1 atm)1.33120.27321.397259.8
Hydrogen (20°C, 1 atm)0.08388.7972.0161.4064124
Helium (20°C, 1 atm)0.166319.624.0031.6672077
Argon (20°C, 1 atm)1.66222.3139.951.67208.1
Carbon Dioxide (20°C, 1 atm)1.83914.6744.011.297188.9
Carbon Monoxide (20°C, 1 atm)1.16517.428.011.401296.8
Methane (20°C, 1 atm)0.668211.0416.041.308518.3
Ethane (20°C, 1 atm)1.269.20730.071.197276.5
Propane (20°C, 1 atm)1.8658.01144.11.139188.6
Butane (20°C, 1 atm)2.4967.27958.121.108143.1
Ammonia (20°C, 1 atm)0.71619.9117.031.319488.2
Hydrogen Sulfide (20°C, 1 atm)1.42811.8634.081.332244
Sulfur Dioxide (20°C, 1 atm)2.71212.664.061.284129.8
Ethylene (20°C, 1 atm)1.17310.328.051.25296.4
Neon (20°C, 1 atm)0.838531.320.181.667412
Steam (IAPWS-IF97)0.597612.2318.021.337461.5
R-134a (20°C, 1 atm)4.33611.621021.12281.49
R-32 (20°C, 1 atm)2.19213.1452.021.256159.8
R-125 (20°C, 1 atm)5.07212.751201.10569.28
R-23 (20°C, 1 atm)2.93514.6770.011.204118.8

Gas density is at 20 °C and 1 atm — it scales with absolute pressure (ρ ∝ P). Saturated steam is quoted at 100 °C. 1 µPa·s = 10⁻⁶ Pa·s. R = Ru/M.

Definitions & Key Relations

Kinematic viscosity is dynamic viscosity divided by density:

ν=μρ\nu = \frac{\mu}{\rho}

Both forms appear in the Reynolds number, which sets the flow regime (laminar vs turbulent):

Re=ρVDμ=VDνRe = \frac{\rho V D}{\mu} = \frac{V D}{\nu}

For a gas, density follows from the ideal-gas law in mass terms, with the specific gas constant R=Ru/MR = R_u / M:

ρ=PR T=P MRu T\rho = \frac{P}{R\,T} = \frac{P\,M}{R_u\,T}
  • μ\mu — dynamic viscosity (Pa·s), ν\nu — kinematic viscosity (m²/s)
  • ρ\rho — density, MM — molar mass, γ=Cp/Cv\gamma = C_p/C_v — specific-heat ratio
  • Ru=8314.5R_u = 8314.5 J/(kmol·K) — universal gas constant, PP absolute pressure, TT absolute temperature

SimuPipe evaluates density and viscosity from temperature correlations at your set fluid temperature, and recomputes gas density at the actual line pressure (Peng-Robinson for non-ideal gases) — so a simulation is not limited to the single reference condition tabulated here.

Frequently Asked Questions

What is the difference between dynamic and kinematic viscosity?
Dynamic (absolute) viscosity μ measures a fluid's resistance to shear, in pascal-seconds (Pa·s) or centipoise (cP, where 1 cP = 0.001 Pa·s). Kinematic viscosity ν is dynamic viscosity divided by density, ν = μ/ρ, in m²/s or centistokes (cSt, where 1 cSt = 1 mm²/s). The Reynolds number can be written with either form — Re = ρVD/μ = VD/ν — so which one you need depends on the data you have. Water at 20°C is about 1.0 cP and 1.0 cSt; the two happen to coincide because water's density is close to 1000 kg/m³.
What density and viscosity should I use for water and air?
For water at 20°C use ρ = 998.2 kg/m³ and μ = 1.002 cP (0.001002 Pa·s). For air at 20°C and 1 atm use ρ = 1.205 kg/m³ and μ = 18.2 µPa·s (1.82×10⁻⁵ Pa·s). Both are the values SimuPipe uses by default. Remember that gas density scales with absolute pressure and temperature, so air at 7 bar(g) is roughly eight times denser than the 1-atm figure in this table.
Why do gas properties depend on pressure and temperature?
Gases are compressible: density rises almost linearly with absolute pressure and falls with temperature (ρ = PM/ZRT for an ideal or near-ideal gas). The densities in the gas table are quoted at 20°C and 1 atm; at higher line pressure you must scale them. Viscosity changes too — gas viscosity rises with temperature — but only weakly with pressure at moderate conditions. SimuPipe recomputes density at the actual operating pressure (using the Peng-Robinson equation of state for non-ideal gases) rather than using the 1-atm value.
What is the specific gas constant R?
The specific gas constant R is the universal gas constant (8314.5 J/kmol·K) divided by the gas's molar mass M: R = R_u/M, in J/(kg·K). It appears in the ideal-gas law in mass terms, P = ρRT, and in compressible-flow equations. Air is 287 J/(kg·K); hydrogen, with the smallest molar mass, is the highest at about 4124 J/(kg·K). Larger molecules (CO₂, refrigerants) have smaller R.
Are these fluid properties temperature-dependent?
Yes. Density and viscosity both change with temperature — strongly for viscous liquids like oils and glycerin, more mildly for water and gases. The values here are quoted at a single reference temperature (20°C for most fluids, 100°C for saturated steam) for comparison. When you run a simulation, SimuPipe evaluates density and viscosity from temperature correlations at the actual fluid temperature you set, rather than using these fixed reference values.
Which fluids does SimuPipe support?
SimuPipe ships with 38 fluid presets — water and steam (IAPWS-IF97), common process liquids (oils, fuels, glycols, alcohols), and gases (air, nitrogen, natural-gas components, refrigerants, and more) — plus custom liquid and custom gas options where you enter your own density and viscosity. Property data comes from CoolProp, IAPWS-IF97, and standard engineering handbooks. Free accounts can use water and air; all 38 presets and custom fluids are available on Pro.

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