2. (3 pts) Heat Transfer via Blood Flow

One of the reasons that jack-rabbits have such large ears (15 cm long!) is for temperature regulation.

The blood, at 37°C, enters a capillary with an 8um diameter at a velocity of 1.14 mm s-¹. The

capillary runs both up and down the full length of the ear. You may assume that the capillary is close

enough to the surface that the surface temperature is the outdoor temperature.

A. On a hot day where the outside temperature is 32°C, what is the temperature of the blood

returning from the ear to the body? (What is a reasonable assumption for the properties of blood?

Hint: you should be well hydrated) Note, ignore that some of this is "micro-fluidics" and don't

worry about a "minimum" Rep.

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B. When it is extra hot, the blood vessels in the ears expand, or "vasodilate". How does this help

with heat transfer? How does vasodilation change the heat transfer coefficient? What is an

advantage of vasodilation?