Calculadora de Dimensionamento de Dutos de Ar | Simplificar o Dimensionamento de Dutos HVAC - Tamanhos de Dutos Precisos para um Fluxo de Ar Eficiente
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Calculadora de Dimensionamento de Dutos de Ar

Determine as dimensões corretas para dutos de ar redondos ou retangulares para um fluxo de ar ideal.

Duct Sizing Results

Duct Area (sq. in.)
Round Duct Diameter (in.)
Standard Round Duct Size
Rectangular Duct Dimensions (in.)
Calculated Velocity (FPM)
Total Pressure Drop (in. w.g.)

Note: Uses the equal friction method for duct sizing, ideal for residential and small commercial HVAC systems. Standard duct sizes are suggested for practical use (e.g., 4", 6", 8", 10", 12" for imperial; 10 cm, 15 cm, 20 cm, 25 cm, 30 cm for metric). For flex ducts, increase friction rate (e.g., 0.15–0.2 in. w.g./100 ft or 1.23–1.64 Pa/m). Consult ASHRAE standards for complex systems.

Understanding HVAC Duct Sizing

This calculator determines optimal duct sizes for HVAC systems using airflow, velocity, and duct shape, with support for both imperial and metric units. It ensures efficient airflow, minimal pressure loss, and reduced noise.

Proper duct sizing prevents high static pressure, noise, or energy waste. The equal friction method maintains a constant friction rate (default: 0.1 in. w.g./100 ft or 0.82 Pa/m for smooth metal ducts). Typical supply duct velocities are 800–1000 FPM (4–5 m/s).

Example Duct Sizing Results

Parameter Imperial Metric Scenario
Airflow 400 CFM 0.189 m³/s Typical for 1-ton HVAC unit
Duct Area 57.6 sq. in. 371.6 cm² 1000 FPM (5.08 m/s)
Round Diameter 8.6 in. (use 8 in.) 21.8 cm (use 20 cm) Standard size
Rectangular Dimensions 10 x 6 in. 25 x 15 cm 2:1 aspect ratio
Pressure Drop 0.13 in. w.g. 32.3 Pa 100 ft (30.48 m), 0.1 in. w.g./100 ft, 2 90° elbows

How to Use the Air Duct Sizing Calculator

  1. Select the unit system (imperial or metric).
  2. Enter airflow (CFM or m³/s, e.g., 400 CFM for a 1-ton HVAC unit).
  3. Specify desired velocity (FPM or m/s, typically 800–1000 FPM or 4–5 m/s).
  4. Choose duct shape and, for rectangular ducts, an aspect ratio. Enter friction rate, duct length, and number/type of elbows.
  5. Click "Calculate Duct Size" to view duct area, dimensions, standard round size, velocity, and pressure drop.

Duct Sizing Comparison

Duct area and pressure drop for round vs. rectangular ducts.

Frequently Asked Questions

Why use standard duct sizes?

Standard sizes (e.g., 4", 6", 8" or 10 cm, 15 cm, 20 cm) are widely available, cost-effective, and ensure compatibility with HVAC fittings.

How does duct shape affect performance?

Round ducts have lower friction and better airflow efficiency, while rectangular ducts save space in tight installations but may increase pressure loss.

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