HVAC Engineering

HVAC Duct Friction Loss Estimator with Roughness and Reynolds Correction Calculator

Calculate hvac duct friction loss estimator with roughness and reynolds correction calculator given relevant engineering parameters.

Quick Answer

Calculate HVAC Duct Friction Loss Estimator with Roughness and Reynolds Correction

Calculator

Pressure Drop per Unit Length (Pa⁄m)
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Result Interpretation

HVAC Duct Friction Loss Estimator with Roughness and Reynolds Correction Calculator computes Pressure Drop per Unit Length in Pa/m using the defined engineering formula and the input values provided.

Worked Example

Verified calculation

Given:

  • Air Density = 1.204
  • Air Velocity = 4
  • Darcy Friction Factor = 0.018
  • Duct Absolute Roughness = 1.5E-6
  • Hydraulic Diameter = 0.25
  • Air Dynamic Viscosity = 1.81E-5

Expected Result:

  • Pressure Drop per Unit Length = 0.693504

Engineering Interpretation:

Under the given input conditions, the calculated result is: Pressure Drop per Unit Length = 0.693504 Pa/m.

The actual numerical result is computed by the Runtime engine using the persisted tool definition. The values shown here come from automatically validated test cases.

Formula / Method

pressure drop per unit length = (darcy friction factor * air density * pow(air velocity, 2)) / (2.0 * hydraulic diameter)

Formula family: formula_hvac_hvac_duct_friction_loss_roughness_reynolds

Variables

SymbolLabelRoleDescription
friction_factor Darcy Friction Factor INPUT Darcy Friction Factor
density_air Air Density INPUT Air Density
velocity_air Air Velocity INPUT Air Velocity
hydraulic_diameter Hydraulic Diameter INPUT Hydraulic Diameter
absolute_roughness Duct Absolute Roughness INPUT Duct Absolute Roughness
dynamic_viscosity_air Air Dynamic Viscosity INPUT Air Dynamic Viscosity
pressure_drop_per_unit_length Pressure Drop per Unit Length OUTPUT Pressure Drop per Unit Length

Calculation Steps

  1. Enter the darcy friction factor in 1.
  2. Enter the air density in kg/m^3.
  3. Enter the air velocity in m/s.
  4. Enter the hydraulic diameter in m.
  5. Enter the duct absolute roughness in m.
  6. Enter the air dynamic viscosity in Pa·s.
  7. Step 1: Compute pressure drop per unit length.
  8. Read the pressure drop per unit length (Pa/m) from the results.

Engineering Summary

Calculate HVAC Duct Friction Loss Estimator with Roughness and Reynolds Correction

Frequently Asked Questions

What does this calculator calculate?

The HVAC Duct Friction Loss Estimator with Roughness and Reynolds Correction Calculator estimates Pressure Drop per Unit Length based on the input parameters you provide

Why is air density important in this calculation?

air density is directly proportional to pressure drop per unit length. When you enter air density in kg/m^3, the calculator uses it in the engineering formula to compute the output

How should I interpret the result pressure drop per unit length?

The calculator outputs pressure drop per unit length in Pa/m. The result is computed directly from the input values using the defined engineering formula

What units should I use for the inputs?

Enter each value in the units shown next to the input field: Air Density (kg/m^3), Air Velocity (m/s), Hydraulic Diameter (m), Duct Absolute Roughness (m), Air Dynamic Viscosity (Pa·s). Make sure all inputs use the specified units for consistent results

What assumptions does this calculator use?

This calculator uses automatically validated engineering formulas. Results are approximate and should be validated against site-specific conditions, applicable codes, and professional engineering judgment

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