Dogs keep themselves cool by panting, rapidly breathing air in and out. Panting results in evaporation from moist tissues of the airway and lungs, which cools the animal. Measurements show that, on a 35∘C day with a relative humidity of 50%, a 12 kg dog loses 1.0 g of water per minute if it is panting vigorously. What rate of heat loss, in watts, does this achieve?

Question

Physics

Joyce Walsh

22 November, 18:45

Dogs keep themselves cool by panting, rapidly breathing air in and out. Panting results in evaporation from moist tissues of the airway and lungs, which cools the animal. Measurements show that, on a 35∘C day with a relative humidity of 50%, a 12 kg dog loses 1.0 g of water per minute if it is panting vigorously. What rate of heat loss, in watts, does this achieve?

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Answers (1)

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Janelle · Answer 1

Evaporation results in cooling because water absorbs heat equal to mass times latent heat of evaporation to get converted into vapor.

latent heat of evaporation of water = 2260 x 10³ J / kg or 2260 J / g

in the evaporation of 1 g of water, heat lost = 2260 J

heat lost per minute = 2260 J

heat lost per second = 2260 / 60

= 37.66 J / s

= 37.66 W

So heat lost by dog in watt = 37.66 W.