Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

• the most efficient way to navigate the Engineering ToolBox!

# Water Flow in Tubes and Reynolds Number

## Reynolds number for clean cold water flow.

Turbulent or laminar flow is determined by the dimensionless Reynolds Number which is important when analyzing fluid flow where there is a substantial velocity gradient (i.e. shear). The Reynolds number indicates the relative significance of the viscous effect compared to the inertia effect and the number is proportional to the inertial force divided by the viscous force.

The flow is

• laminar when Re < 2300
• transient when 2300 < Re < 4000
• turbulent when 4000 < Re

Reynolds Number for one liter of water at approximately 20oC (68oF) flowing through pipes of different dimensions:

Pipe Size
(inches)11 1/223468101218
(mm)25405075100150200250300450
Reynolds number with
1 liter/min
835 550 420 280 210 140 105 85 70 46
Reynolds number with
1 gal/min
3180 2090 1600 1060 780 570 400 320 265 175

Note that the water viscosity varies with temperature.

• the kinematic viscosity of water at 20oC - used to calculate the table above - is 1.004·10-6 m2/s
• at 0oC the kinematic viscosity is 1.787·10-6 m2/s - the Reynolds values in the table above must be multiplicated with 1.004 / 1.787 = 0.56
• at 100oC the kinematic viscosity is 0.29·10-6 m2/s - the values in the table above must be multiplicated with 1.004 / 0.29 = 3.46

## Related Topics

• Fluid Mechanics - The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
• Fluid Flow and Pressure Loss - Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more.

## Search Engineering ToolBox

• the most efficient way to navigate the Engineering ToolBox!

## SketchUp Extension - Online 3D modeling!

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!

## Privacy

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.

Temperature

oC
oF

Length

m
km
in
ft
yards
miles
naut miles

Area

m2
km2
in2
ft2
miles2
acres

Volume

m3
liters
in3
ft3
us gal

Weight

kgf
N
lbf

Velocity

m/s
km/h
ft/min
ft/s
mph
knots

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O

Flow

m3/s
m3/h
US gpm
cfm

6 24