Chapter 1, Problem 1.18P

You've experienced convection cooling if you've ever extended your hand out the window of a moving vehicle or into a flowing water stream. With the surface of your hand at a temperature of $30°\text{C,}$ determine the convection heat flux for (a) a vehicle speed of 35 km/h in air at $-5°\text{C}$ with a convection coefficient of $40{\text{W/m}}^{\text{2}}\cdot \text{K}$ and (b) a velocity of 0.2 m/s in a water stream at $10°\text{C}$ with a convection coefficient of $900{\text{W/m}}^{\text{2}}\cdot \text{K}\text{.}$ Which condition would feel colder? Contrast these results with a heat loss of approximately $30{\text{W/m}}^{\text{2}}$ under normal room conditions.