Fanning yourself on a hot day cools you off more than you might think

Labor Day has come and gone. But the heat remains. For a while, anyway. So keep your fan handy. That’s the advice of a theoretical astrophysicist. He says that fanning cools you off more than you might think.

Dr. E. Sterl Phinney is the astrophysicist. In a Wall St. Journal report, he breaks down the fanning effect by the numbers.

Amount of energy you produce while at rest… about 100 watts.

Waving a fan adds… about one watt.

The result… coolness is doubled.

The trick, according to Dr. Phinney, is to reduce the boundary layer. That’s the layer of motionless air between your skin and the air around you. Fanning makes the boundary layer thinner. And you feel significantly cooler.

For only one watt of effort, you can’t go wrong.

But Dr. Phinney has a suggestion for even better results. With a minimum of effort, a porch swing creates a wraparound breeze to thin even more of your boundary layer.

Pretty cool.

“Does Fanning Help on a Hot Day?” Heidi Mitchell, Wall St. Journal, 8/6/12,

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