Not All Flow Tests Require a Test Port
by Matthew Gentry
Airflow Sciences Corporation (ASC) has always used a wide variety of testing equipment, tailoring the tools to the specific job at hand. In the past few years, ASC has been presented with a few opportunities to quantify fan performance in non-standard applications. These cases involved fans discharging into a room or tunnel where there was no feasible way to install test ports and complete a standard duct traverse. Instead, ASC utilized a test rig consisting of an array of vane anemometers. A vertical strut was used to support instruments held at different elevations. This allowed for simultaneous measurement of an entire column of data. The position of the support strut was then adjusted to complete a full traverse.
The vane anemometers were calibrated in an ASC’s EPA-certified wind tunnel, with NIST-traceable reference measurements prior to the test. All data were logged to a computer via a data acquisition system. Using the data acquisition computer and sampling from multiple vanes simultaneously, complete traverses consisting of 80-100 test points, were completed very quickly (~15 minutes), reducing any concerns about transient variations in the flows. The computer-controlled sampling also eliminated any human tester biases or any “eye averaging” that might be required when using a single handheld vane anemometer, resulting in improved measurement accuracy.
For HVAC, clean room, or fan testing applications where test ports are not practical and accurate flow measurements are required, this unique system has proven to be an excellent tool.