ν = μ / ρ = kinematic viscosity (m 2 /s, ft 2 /s)
For a pipe or duct the characteristic length is the hydraulic diameter .
L = d h
where
d h = hydraulic diameter (m, ft)
The Reynolds Number for the flow in a duct or pipe can with the hydraulic diameter be expressed as
Re = ρ u d h / μ
= u d h / ν (2)
where
d h = hydraulic diameter (m, ft)
The Reynolds number for a pipe or duct expressed in Imperial units
Re = 7745.8 u d h / ν (2a)
where
Re = Reynolds Number (non dimensional)
u = velocity (ft/s)
d h = hydraulic diameter (in)
ν = kinematic viscosity (cSt) (1 cSt = 10 -6 m 2 /s )
The Reynolds Number can be used to determine if flow is laminar, transient or turbulent. The flow is
In practice laminar flow is only actual for viscous fluids - like crude oil, fuel oil and other oils.
A Newtonian fluid with a dynamic or absolute viscosity of 0.38 Ns/m 2 and a specific gravity of 0.91 flows through a 25 mm diameter pipe with a velocity of 2.6 m/s .
Density can be calculated from the specific gravity of the fluid and the density of the specific gravity reference water 1000 kg/m 3 - as
ρ = 0.91 (1000 kg/m 3 )
= 910 kg/m 3
Reynolds Number can then be calculated using equation (1) like
Re = (910 kg/m 3 ) (2.6 m/s) (25 mm) (10 -3 m/mm) / (0.38 Ns/m 2 )
= 156 ((kg m / s 2 )/N)
= 156 ~ Laminar flow
1 (N) = 1 (kg m / s 2 )
- free apps for offline use on mobile devices.
This calculator can be used if density and absolute (dynamic) viscosity of the fluid is known. The calculator is valid for incompressible flow - flow with fluids or gases without compression - as typical for air flows in HVAC systems or similar. The calculator is generic and can be used for metric and imperial units as long as the use of units are consistent.
Default values are for air at 60 o F , 2 atm pressure and density 0.146 lb m /ft 3 , flowing 20 ft/s between two metal sheets with characteristic length 0.5 ft . Dynamic (absolute) viscosity is 1.22 10 -5 lb m /s ft .
The calculator below can be used when kinematic viscosity of the fluid is known. The calculator is generic and can be used for metric and imperial units as long as the use of units are consistent.
Default values are for water at 20 o C with kinematic viscosity 1.004 10 -6 m 2 /s in a schedule 40 steel pipe . The characteristic length (or hydraulic diameter) of the pipe is 0.102 m .
Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more.
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Dimensions of pipes and tubes, materials and capacities, pressure drop calculations and charts, insulation and heat loss diagrams.
Hot and cold water service systems - design properties, capacities, sizing and more.
Online calculators, figures and tables with dynamic and kinematic viscosity of liquid and gaseous butane, C4H10, at varying temperarure and pressure, SI and Imperial units.
Friction loss coefficients in pipes, tubes and ducts.
The Darcy-Weisbach equation can be used to calculate the major pressure and head loss due to friction in ducts, pipes or tubes.
Physical and chemical dimensionless quantities - Reynolds number, Euler, Nusselt, and Prandtl number - and many more.
Calculate pressure loss - or head loss - in ducts, pipes or tubes.
Online calculator, figures and tables showing dynamic and kinematic viscosity of ethylene, C2H4, also called ethene or acetene, at varying temperature and pressure - Imperial and SI Units.
The entrance length is the length in a tube or duct after an obstruction - until the flow velocity profile is fully developed.
Calculate hydraulic diameter for pipes and ducts.
Calculate friction coefficients for laminar fluid flow.
Heat transfer, pressure and head loss in a fluid varies with laminar, transitional or turbulent flow.
Kinematic viscosities of some common liquids like motor oil, diesel fuel, peanut oil and many more.
Online calculator, figures and tables showing dynamic and kinematic viscosity of liquid methanol,CH3OH, at varying temperature - Imperial and SI Units.
Calculate fluid flow friction coefficients from a Moody diagram.
Online calculator, figures and tables showing dynamic and kinematic viscosity of oxygen, O2, at varying temperature and pressure - Imperial and SI Units.
A dimensionless number approximating the ratio of momentum diffusivity to thermal diffusivity.
Vicosity is a fluid's resistance to flow and can be valued as dynamic (absolute) or kinematic.
Friction loss in steel pipes for fluids with viscosities ranging 32 - 80000 SSU.
Convert between volume flow units like gpm, liter/sec, cfm, m3/h.
Absolute viscosity for water in centipoises for temperatures between 32 - 200oF.
Reynolds number for clean cold water flow.
Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!
We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.
Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.
Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.
AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.
If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. You can target the Engineering ToolBox by using AdWords Managed Placements.