Chapter 1, Problem 1.74P

Most of the energy we consume as food ¡s converted tothermal energy in the process of performing all our bodilyfunctions and is ultimately lost as heat from our bodies.Consider a person who consumes 2100 kcal per day (notethat what are commonly referred to as food calories areactually kilocalories), of which 20000 kcal is converted tothermal energy. (The remaining 100 kcal is used to dowork on the environment.) The person has a surface area of $\text{1}.{\text{8 m}}^{\text{2}}$ and is dressed in a bathing suit.
(a) The person is in a room at 20°C, with a convectionheat transfer coefficient of $\text{3 W}/{\text{m}}^{\text{2}}\cdot \text{K}$ . At this airtemperature, the person is not perspiring much. Estimate the person’s average skin temperature.
(b) If the temperature of the environment were 33°C,what rate of perspiration would be needed to maintain a comfortable skin temperature of 33°C?