Aperson is walking outdoors on a cold day when the temperature is -20°c. he is breathing at the rate of 16 breaths per minute, and each time he breathes in he inhales 0.0050 m3 of air. at what rate does he lose heat from breathing if the air in his lungs is heated to body temperature (37°c) before it is exhaled? the specific heat of air is 1020 j/kg ∙ k and the density of air is 1.29 kg/m3.

Along wire of diameter 1 mm is submerged in an oil bath of temperature ∞ 31°c. the wire has an electrical resistance per unit length of 0.01 ω/m. if a current of 103 a flows through the wire and the convection coefficient is 500 w/m2·k, what is the steady-state temperature of the wire? from the time the current is applied, how long does it take for the wire to reach a temperature that is within 1°c of the steady-state value? the properties of the wire are 8000 kg/m3, 500 j/kg·k, and 20 w/m·k.