Heat Loss During Breathing. In very cold weather a significant mechanism for heat loss by the human body is energy expended in warming the air taken into the lungs with each breath.
(a) On a cold winter day when the temperature is -20°C, what amount of heat is needed to warm to body temperature (37°C) the 0.50 L of air exchanged with each breath? Assume that the specific heat of air is 1020 J /kg • K and that 1.0 L of air has mass 1.3 X 10-3 kg. (b) How much heat is lost per hour if the respiration rate is 20 breaths per minute?