{"id":4291,"date":"2026-09-02T17:00:21","date_gmt":"2026-09-03T00:00:21","guid":{"rendered":"https:\/\/www.rbdinstruments.com\/blog\/?p=4291"},"modified":"2026-09-06T09:14:04","modified_gmt":"2026-09-06T16:14:04","slug":"checking-cooling-fan-performance-easily-with-cheap-handheld-anemometer","status":"publish","type":"post","link":"https:\/\/www.rbdinstruments.com\/blog\/checking-cooling-fan-performance-easily-with-cheap-handheld-anemometer\/","title":{"rendered":"Checking Cooling Fan Performance Easily with Inexpensive Handheld Anemometer"},"content":{"rendered":"\n

Intro<\/strong><\/span><\/p>\n\n\n\n

In this post we’ll explain a quick, simple, and inexpensive way to check on the performance of commonly used cooling fans using a handheld anemometer. This technique will assist you in comparing your cooling fan\u2019s current performance against its nameplate specifications, giving you a tool to track their condition. Having information about fan condition will help you schedule maintenance intervals or determine if the fan needs to be replaced.<\/p>\n\n\n\n

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Cooling fans are critical components used for regulating the temperature of engines, motors, circuitry, inhabited spaces, and experiment samples. It isn’t difficult to imagine scenarios in which expensive and sensitive equipment could be damaged due to the failure of a cooling fan. I feel confident assuming that we’d all like to avoid the potentially disastrous costs and consequences that fill the epilogues of equipment failure events. A non-zero number of these events could have been avoided by monitoring, maintaining, and\u2014when necessary\u2014replacing the problematic fans (sometimes for as little as a few dollars).<\/p>\n\n\n\n

Basic maintenance for the most common fans we are likely to interact with usually consists of nothing more than blasting off the dust and grime that accumulates on the blades with a little compressed \u201cair\u201d. Fan replacement is rarely necessary. Even the least expensive fans can perform for years! Fans are cheap, easy to acquire, and require very little skill or knowledge to implement and maintain. These qualities make these ubiquitous little workhorses well-suited for most temperature regulating duties.<\/p>\n\n\n\n

So, what if we wanted a way to check up on our aging fans? You know the ones\u2014faithfully purring away in the shadows, cooling critical equipment longer than anyone can remember. If only there was some convenient metric we could use to compare the old fan’s performance against what it was back when the fan-storks first delivered Baby Fan to our doorstep all those years ago. We could gain some insight into the present \u201chealth\u201d of the fan on its stoic journey towards inevitable doom.<\/p>\n\n\n\n

Fortunately for us, manufacturers include their fan\u2019s volumetric flow rate<\/em> (VFR) as one of the listed performance specifications! We can approximate the VFR for our fans by taking a few simple measurements and making a few simple calculations. Comparing the fan’s current VFR against its rated VFR can help alert us to small problems before they become bigger ones. (Note: We don’t like \u201cexpensive noises\u201d, \u201cunwelcomed smells\u201d, or error codes any more than you do).<\/p>\n\n\n\n

Volumetric flow rate<\/em> is just a fancy way of saying, \u201cThis is how many volume-units<\/em> passed by here per some unit of time<\/em>,” and is calculated below with its dimensional units given in the brackets:<\/p>\n\n\n\n

Equation 1:<\/strong><\/p>\n\n\n\n

<\/mtd>Q<\/mi>=<\/mo>V<\/mi>A<\/mi> <\/mtext>[<\/mo>d<\/mi>i<\/mi>s<\/mi>t<\/mi>a<\/mi>n<\/mi>c<\/mi>e<\/mi>3<\/mn><\/msup>\/<\/mi>t<\/mi>i<\/mi>m<\/mi>e<\/mi>]<\/mo><\/mrow><\/mtd><\/span><\/mtext><\/mtd><\/mtr><\/mtable>\\begin{equation}Q = VA~[distance^3\/time]\\end{equation}<\/annotation><\/semantics><\/math><\/div>\n\n\n\n

<\/p>\n\n\n\n

where Q is the volumetric flow rate<\/em>, V is the fluid velocity<\/em>, and A is the cross-sectional area<\/em> of the fluid stream (area normal to the flow direction). Commonly used units are m3<\/sup>\/s, CFM (aka: ft3<\/sup>\/min), and ml\/hr. The handheld anemometer will give us a velocity, and we will calculate the area via simple measurements taken from the fan.<\/p>\n\n\n\n

(Note<\/strong>: Why “Q<\/em>” for “volumetric flow rate?” Well, way back in 1840, Jean L\u00e9onard Marie Poiseuille was busy experimentally deriving a really great formula to get the pressure drop of blood within blood vessels. He realized that volumetric flow rate was an important “…quantity<\/em>…” for his formula.)<\/p>\n\n\n\n

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