How to Calculate Airflow Rate

Airflow Rate Calculator

Understanding Airflow Rate

Airflow rate is a crucial measurement in many fields, including HVAC (Heating, Ventilation, and Air Conditioning), industrial processes, and environmental monitoring. It quantifies the volume of air that moves through a given space or system over a specific period. Calculating airflow rate accurately helps in designing efficient ventilation systems, ensuring proper air exchange in buildings, and optimizing industrial operations.

How to Calculate Airflow Rate

The fundamental formula for calculating airflow rate (often denoted as 'Q') is:

Q = A × v

Where:

• Q is the Airflow Rate (usually in cubic meters per second, m³/s).
• A is the cross-sectional Area of the duct or opening (in square meters, m²).
• v is the average Velocity of the air moving through that area (in meters per second, m/s).

To use this calculator, you need to provide the dimensions of the duct (width and height) and the average speed of the air flowing through it. The calculator will first determine the cross-sectional area of the duct and then multiply it by the air velocity to give you the airflow rate.

Duct Area Calculation

For a rectangular duct, the area (A) is calculated as:

A = Duct Width × Duct Height

Example Calculation

Let's say you have a rectangular duct with a width of 0.5 meters and a height of 0.3 meters. The average air velocity measured within this duct is 2.5 meters per second.

• Duct Width = 0.5 m
• Duct Height = 0.3 m
• Air Velocity = 2.5 m/s

First, calculate the cross-sectional area:

Area (A) = 0.5 m × 0.3 m = 0.15 m²

Next, calculate the airflow rate:

Airflow Rate (Q) = Area (A) × Air Velocity (v) = 0.15 m² × 2.5 m/s = 0.375 m³/s

So, the airflow rate in this example is 0.375 cubic meters per second.

function calculateAirflow() { var ductWidth = parseFloat(document.getElementById("ductWidth").value); var ductHeight = parseFloat(document.getElementById("ductHeight").value); var airVelocity = parseFloat(document.getElementById("airVelocity").value); var resultDiv = document.getElementById("result"); resultDiv.innerHTML = ""; // Clear previous results if (isNaN(ductWidth) || isNaN(ductHeight) || isNaN(airVelocity) || ductWidth <= 0 || ductHeight <= 0 || airVelocity <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for all fields."; return; } var ductArea = ductWidth * ductHeight; var airflowRate = ductArea * airVelocity; resultDiv.innerHTML = "Duct Area: " + ductArea.toFixed(2) + " m²" + "Airflow Rate: " + airflowRate.toFixed(3) + " m³/s"; }