Monday, June 8, 2009

Keeping your dog cool... a physics lesson.

This weekend was one of the first where we had to worry about keeping our dogs cool. On the black dogs especially, you could feel the effects of the sunshine, as they were hot to the touch. However, I continue to see people whose only effort to cool their dog is putting them in front of a fan-which has limited benefits for dogs. But to explain, I'll start with a quick physics lesson.
Fans feel "cool" to us because of "evaporative cooling," the physical phenomenon in which objects cool (or lose heat) when the liquid on or inside evaporates into the surrounding air, taking energy with it. To demonstrate this phenomenon, take a dry kitchen or hand towel and twirl it above your head for 15-20 seconds, then stop and feel the towel. If it was dry, you shouldn't feel any difference in temperature. Now, wet the towel with lukewarm water, wring it out and twirl again. This time you should feel a big difference in temperature! This is because the water molecules on the towel evaporated into the air taking energy (heat) along with them. When you twirled the towel, you were simulating a fan, exciting the molecules and making it easier for them to evaporate. This is why a fan feels so good when we are sweaty and hot.
But back to dogs.... dog do not sweat except for the pads of their feet. So turning a fan on a dog is like twirling the DRY towel. There is a minimal benefit of exchanging the air if they are in a tightly enclosed area that is warmer than the outside air due to their own body heat, but this is nothing like what we experience by sitting in front of a fan. To simulate the cooling effect we get from fans, you have to simulate persperation as well. So keep a spray bottle handy, or find a place to get your dog wet. Or buy/make a dog "cool coat" which works on this same principle by placing a moist fabric on the dog to provide evaporative cooling. Most importantly, when YOU are sweating, your dog is probably hot also and remember that recirculating air with a fan alone really does very little to cool your dog.

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