How to compute the amount of heat body needed on a cold weather day?

Question

In a very cold weather day when temperature is -20C, what is the amount of heat needed to warm to body temperature37C,the .50L of air exchanged w/ each breath?Assume the specific heat of Air=1020j/kg K, 1L of air has a mass of 1.3x 10 raise to neg.3kg. How much heat is loss per hour if the respiration rate is 20 breaths/min?

Answer 1

Treat the air as if it were cooled from 37ºC to -20ºC. You have the specific heat and the density of air, so you can calculate the volumetric specific heat. This is multiplied by the temperature change and the respiration rate to get the heat loss