Surface coefficients to calculate flow friction and major pressure loss - surfaces like concrete, galvanized steel, corroded steel and more
Material: Nature of Material: Roughness mm Roughness inch Steel pipe: drawn, new: 0.02 - 0.1: 0.0008 - 0.004: welded, new: 0.05 - 0.1: 0.002 - 0.004.
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:
| Surface | Absolute 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 |
- The roughness is actually a measurement of all the asperities at the surface of a material, especially a pipe where it will oppose the flow of fluid. The following table is summarizing usual pipe roughness for many materials used for piping or ducts.
- Material: Nature of Material: Roughness mm Roughness inch Steel pipe: drawn, new: 0.02 - 0.1: 0.0008 - 0.004: welded, new: 0.05 - 0.1: 0.002 - 0.004.
- In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in non-dimensional form that relates the Darcy-Weisbach friction factor f D, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.
- 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 / dh (1)
where
r = relative roughness
k = roughness of duct, pipe or tube surface (m, ft)
dh = 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 for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more
Related Documents
- Colebrook Equation - Calculate friction loss coefficients in pipes, tubes and ducts
- Energy Equation - Pressure Head Loss in Ducts, Tubes and Pipes - Pressure and head loss in ducts, pipes and tubes
- Grit Size vs. Surface Roughness - Comparison of sandpaper grit size and surface roughness
- Manning's Roughness Coefficients - Manning's roughness coefficients for common materials
- Mechanical Processing and Surface Roughness - Mechanical production methods and surface roughness
- Velocity Classification of Ventilation Ducts - Recommended air velocities in ventilation ducts
Tag Search
Carbon Steel Pipe Roughness Factor
- en: roughness coefficients friction ducts