As a coffee enthusiast you wish to keep your coffee as hot as possible for as lo

Question

As a coffee enthusiast you wish to keep your coffee as hot as possible for as long as possible. You wish to find the rate of heat loss of a typical coffee mug. Assume the mug to be a cylinder which has a lid made out of the same material as the rest of the cylinder, and the thickness of the walls is 1.17 cm. If the coffee in the mug is 83.4 °C and the room temperature is 21.6 °C how much more heat does the mug lose through conduction than from radiated energy.

Assume that the thermal conductivity of all sides of the mug is 0.919 W/m·C, that the mug has an emissivity of 0.790 and the Stefan-Boltzmann Constant is 5.67 × 10-8 W/m2·K4. Remember to properly convert all units and to include all surfaces of the mug.

Explanation / Answer

Heat loss due to conduction

H = K A/d dT (Where H is the energy flow rate)

H= 0.919 * 1.17 * (83.4 - 21.6) = 0.0616 J/s

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