Common Inputs
Round Duct
Rectangular Duct
Introduction
Common Inputs:
Air Density & Dynamic Viscosity:
These are parameters dependent on the state of the air. Users can adjust them based on the specific conditions of the fluid in the duct. For example, with normal air, the density is 1.204 kg/m³ and the viscosity is 0.0000182 Pa·s, but for smoke or exhaust gases, these values may vary.
Duct Roughness (mm):
The roughness of duct surfaces depends on the material. For example:
- Galvanized metal duct: 0.09 mm
- Stainless steel duct: 0.15 mm
- PVC plastic duct: 0.01 mm
Calculation Formulas:
Reynolds Number (Re):
Re = (ρ × v × Dh) / μ
- Re: Reynolds number
- ρ: Air density (kg/m³)
- v: Air velocity (m/s)
- Dh: Hydraulic diameter (m)
- μ: Dynamic viscosity (Pa·s)
Friction Factor:
Laminar Flow: f = 64 / Re
Turbulent Flow: Colebrook-White equation for turbulent flow:
1 / √f = -2.0 log10[(ε / 3.7D) + (2.51 / Re√f)]
- f: Friction factor
- ε: Duct surface roughness (m)
Pressure Loss:
ΔP = f × (L / Dh) × (ρ × v² / 2)
- ΔP: Pressure loss (Pa/m)
- L: Duct length (m)
- Dh: Hydraulic diameter (m)
- v: Air velocity (m/s)