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

# Roughness & Surface Coefficients

## Surface coefficients that can be used to calculate friction and major pressure loss for fluid flow with surfaces like concrete, galvanized steel, corroded steel and more.

For turbulent flow the friction coefficient depends on the Reynolds Number and the roughness of the duct or pipe wall. Roughness for different materials can be determined by experiments.

Absolute roughness - k - for some common materials below:

Surfaces - Roughness & Surface Coefficients
SurfaceAbsolute Roughness Coefficient
- k -
( 10-3 m)
(feet)
Drawn Copper, Lead, Brass, Aluminum (new) and the like 0.001 - 0.002 (3.28 - 6.56) 10-6
PVC, PE and other smooth Plastic Pipes 0.0015 - 0.007 (0.49 - 2.30) 10 -5
Stainless steel, bead blasted 0.001 - 0.006 (0.00328 - 0.0197) 10-3
Stainless steel, turned 0.0004 - 0.006 (0.00131 - 0.0197) 10-3
Stainless steel, electron-polished 0.0001 - 0.0008 (0.000328 - 0.00262) 10-3
Commercial steel or wrought iron 0.045 - 0.09 (1.48 - 2.95) 10-4
Stretched steel 0.015 4.95 10 -5
Weld steel 0.045 1.48 10-4
Galvanized steel 0.15 4.92 10-4
Rusted steel (corrosion) 0.15 - 4 (4.92 - 131) 10-4
New cast iron 0.25 - 0.8 (8.2 - 26.2) 10-4
Worn cast iron 0.8 - 1.5 (2.62 - 4.92) 10-3
Rusty cast iron 1.5 - 2.5 (4.92 - 8.2) 10-3
Sheet or asphalted cast iron 0.01 - 0.015 (3.28 - 4.92) 10 -5
Smoothed cement 0.3 0.98 10-3
Ordinary concrete 0.3 - 1 (0.98 - 3.28) 10-3
Coarse concrete 0.3 - 5 (0.98 - 16.4) 10-3
Wood stove 0.18 - 0.9
Well planed wood 0.18 - 0.9 (5.9 - 29.5) 10-4
Ordinary wood 5 16.4 10-3
• 1 m = 3.28 feet
• Galvanized Steel - standard and commonly most used material in comfort air conditioning systems
• Aluminum - is widely used in clean room applications. Preferred for moisture laden air, special exhaust systems and ornamental duct systems
• Stainless Steel - is used in duct systems for kitchen exhaust, moisture laden air, and fume exhaust
• Carbon Steel (Black Iron) - is widely used in applications involving flues, stacks, hoods, other high temperature and special coating requirements for industrial use
• Copper - is mainly used for certain chemical exhaust and visual ductwork

### Relative Roughness

Relative roughness - the ratio between absolute roughness an pipe or duct diameter - is important when calculating pressure loss in ducts or pipes with the Colebrook Equation . Relative roughness can be expressed as

r = k / d h (1)

where

r = relative roughness

k = roughness of duct, pipe or tube surface (m, ft)

d h = hydraulic diameter (m, ft)

### Typical Duct Materials and Their Use

• Galvanized Steel - most common material used in fabricated duct work for most comfort air conditioning systems.
• Aluminum - widely used in clean room applications, moisture laden air, exhaust systems and ornamental duct systems.
• Stainless Steel - used for kitchen exhaust, moisture laden air and fume exhausts.
• Carbon Steel (Black Iron) - used for flues, stacks, hoods, high temperature industrial systems.
• Copper - used for certain chemical exhaust systems and ornamental duct work.
• Fibreglass Reinforced Plastic (FRP) - used mainly for chemical exhausts, scrubbers and underground systems. Resistant to corrosion, self insulated, excellent sound attenuation and high quality sealing.
• Polyvinyl Chloride (PVC) - used in chemical exhaust, fumes and underground duct systems. Resistant to corrosion, light weight, easy to modify.
• Fabric (textile ducts) - used for even air distribution.
• Flex Duct (inner liner supported by a helix wire coil) - used for connections.

## Related Topics

• ### Ventilation Systems

Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

## Related Documents

• ### Colebrook Equation

Friction loss coefficients in pipes, tubes and ducts.
• ### Energy Equation - Pressure Loss vs. Head Loss

Calculate pressure loss - or head loss - in ducts, pipes or tubes.
• ### Grit Size vs. Surface Roughness

Comparing sandpaper grit size and surface roughness.
• ### Manning's Roughness Coefficients

Manning's roughness coefficients for some common materials.
• ### Surface Roughness vs. Mechanical Processing

Mechanical production methods and their surface roughness.
• ### Velocity Classification of Ventilation Ducts

Recommended air velocities in ventilation ducts

## Search

Search is the most efficient way to navigate the Engineering ToolBox.

## 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 older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

## Citation

• The Engineering ToolBox (2003). Roughness & Surface Coefficients. [online] Available at: https://www.engineeringtoolbox.com/surface-roughness-ventilation-ducts-d_209.html [Accessed Day Month Year].

Modify the access date according your visit.

7.8.15

.