Ceiling fan with most airflow1/2/2024 Next time you’re looking for a ceiling fan, check the label. A good fan will give you more than 100 cfm per watt a poor one might be as low as 30 cfm per watt. Its units are cubic feet per minute (cfm) of air flow per watt (W) of electrical power. ( Efficacy is an efficiency rating where the output and input quantities have different units.) For fans, the measure of efficacy is how much air flow you get for the amount of electrical energy you put in. A fan’s efficacy tells you how well it moves airĮvery new ceiling fan being sold in the US these days is labeled with its efficacy. If the air movement created by a ceiling fan isn’t hitting anyone’s skin, it’s just making the space warmer with no cooling benefit. They cool our bodies two ways: by aiding evaporative cooling and by aiding convective cooling. Ĭeiling fans are useful for cooling only when they move air over skin. No, it’s not a lot of heat, but just be aware that the net result of running a ceiling fan is that you’re adding heat to the room, not cooling it. From the second law of thermodynamics, we know where that heat is going - into the cooler room. The infrared image below shows a ceiling fan motor that’s hotter than the room it’s in. Why? Because electric motors are devices that turn electrical energy into mechanical energy, most of which ends up as heat. (See number 2 below.) But its effect on the room it’s in is to add heat. Sounds clever, but it’s a ridiculous idea.Īnyway, here are seven things about ceiling fans that a lot of people seem not to know. What got me on to this topic was a video of a fan with blades that hide on top of the fan when the fan is turned off. So why don’t we chop down some myths and misconceptions about ceiling fans. Here we are in the middle of air conditioning season.
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