Duct Airflow Measurement

Ashrae provides guidance on the number and location of measuring points within a plane for both rectangular and circular ducts.

Duct airflow measurement.

For duct sides shorter than 30 five traversal points must be taken 5 on each side 5 5 25. Design airflow 50 85 125 1500 2000 180 240 325 525. Our customer base both in the uk and overseas is wide ranging from air quality specialists process manufacturers consultants and commissioning engineers through to insurance inspectors local authorities hospitals military and scientific research. A maximum of forty nine sample points can be used in pipes with larger dimensions.

Measure how far in inches the card swings inward to get a sense of the fan s airflow. Airflow measurements are very proud to be a uk channel partner for tsi instruments who are one of the leading manufacturers in the industry. Airflow can vary across the cross sectional area of a duct. Measurement accuracy improves by taking measurements at multiple points and then calculating the mean.

Flex duct 05 on most metal duct calculator round metal pipe 06 on most metal duct calculators field duct sizing chart. If frictional losses are neglected. Measuring airflow in a duct with a square or rectangular shape. Verabar a new idea in duct air flow measurement the veris verabar is designed to be the most reliable accurate and repeatable method of measuring volumetric or mass airflow in round and rectangular ducts.

A rectangular duct pipe will require a minimum of twenty five sample points alongside the cross section to give us an accurate measurement. Rotating vane anemometer measurement mid airflow range pressure drop across the dry evaporator coil estimate total external static pressure method estimate. New duct sizing chart xls author. Duct area can be inputted to allow direct volume flow measurement figure 6.

A total of eighteen readings accurately describes the air flow rate. The most common and easiest way to measure or with some methods estimate and set airflow is to use one of the following methods. Take airflow measurements at a minimum of 25 points regardless of duct size. Air flow in large ducts power and plant utilities duct air flow.

25 cfm for 1 5 inches 3 8 cm 35 cfm for 2 inches 5 1 cm 48 cfm for 2 5 inches 6 4 cm cfm stands for cubic feet per minute which is how airflow is measured. In power and plant utility measurement the verabar delivers precise control of combustion airflow to ensure proper fuel to. Where to measure airflow. Air flow by g j matthews airflow developments limited.

Three traverses diameters evenly spaced at 60 create six pieces of pie in a round duct. Note the air most affected by friction is seemingly over represented. Twothirds toward the center. For duct sides longer than 36 seven points must be taken.

The rough airflow measurements for different inches are. Three air flow measurements are taken per radius. A tube placed in a duct facing into the direction of the flow will measure the total pressure in the duct.