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 77.1 °C and the room temperature is 24.0 °C how much more heat does the mug lose through conduction than from radiated energy. See the hint below for important constants. The mug loses heat by condensation (Fill in the blank with a number) times more quickly than by radiation.

Explanation / Answer

Heat transfer through conduction is given by

q = kA dT/s , where k= thermal conductivity of material, A= heat transfer area, dT= temperature gradient - difference - in the material, s=material thickness

require k A for the material to calculate this.

Heat loss due to radiation

q= (epsilon)* (sigma) * (delta T)^4

epsilon = emissivity of the body

sigma = stefan boltzmann constant

delta T= temperature gradient

provide the material parameters to solve the problem.

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