The student from Problem 79 realizes that standing naked in a cold room will not give him the desired weight loss results since it is much less efficient than simply exercising. So he decides to “burn” calories through conduction. He fills the bathtub with 16°C water and gets in. The water right next to his skin warms up to the same temperature as his skin, 35°C, but the water only 3.0 mm away remains at 16°C. At what rate (in kcal/h) would he “burn” calories? The thermal conductivity of water at this temperature is 0.58 W/(m · K).

Data From Problem 79

A student wants to lose some weight. He knows that rigorous aerobic activity uses about 700 kcal/h (2900 kJ/h) and that it takes about 2000 kcal per day (8400 kJ) just to support necessary biological functions, including keeping the body warm. He decides to burn calories faster simply by sitting naked in a 16°C room and letting his body radiate calories away. His body has a surface area of about 1.7 m², and his skin temperature is 35°C. Assuming an emissivity of 1.0, at what rate (in kcal/h) will this student “burn” calories?