Using the information estimate the ambient air temperature that could cause frostbite on a calm day on the ski slopes.

GIVEN

• Skier’s skin of thickness (L) = 3 mm = 0.003 m exposed to cold air

• Inner surface temperature of skin (Tsi) = 35°C

• Thermal conductivity of skin (k) = 0.35 W/(m K)

• Convective heat transfer coefficient in still air ( ch ) = 20 W/(m2 K)

• Frostbite occurs at an outer skin surface temperature (Tso) = 10°C FIND

• The ambient air temperature (T?) that could cause frostbite ASSUMPTIONS

• Steady state conditions prevail

• One dimensional conduction occurs through the skin

• Radiative loss (or gain from sunshine) is negligible

SKETCH


The rate of conductive heat transfer through the skin at frostbite conditions is



The rate of convective heat transfer from the surface of the skin,



These heat transfer rates must be equal



Solving for the ambient air temperature

Physics & Space Science

You might also like to view...

A star (no matter what its mass) spends most of its life

A) as a main-sequence star. B) as a T-Tauri variable star. C) as a planetary nebula. D) as a protostar. E) as a red giant or supergiant.

Physics & Space Science

Two parallel wires carry the a current I in the same direction. Midway between these wires is a third wire, also parallel to the other two, which carries a current 0.5 I, but in the direction opposite from the first two wires. In which direction are the net forces on the outer wires?

a. Both forces are toward the center wire. b. Since the net forces are zero, there is no direction. c. Both forces are away from the center wire. d. Both forces on the two wires are in the same direction in space.

Physics & Space Science

Electrons are accelerated through a potential difference of 90.0 kV and directed at a tungsten target to produce x-rays. What is the cutoff frequency in the x-ray spectrum produced?

a.
b.
c.
d.
e.

Physics & Space Science

A galaxy with randomly oriented elongated star orbits and little gas and dust would be a(n) _______________ galaxy

Fill in the blank(s) with correct word

Physics & Space Science