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Thermodynamics heat transfer problem

  1. Apr 25, 2010 #1
    1. The problem statement, all variables and given/known data

    An 85kg yachtsman falls out of his boat into the cold ocean waters. He begins to loose body heat through a 0.02m thick layer of surface fat. The surface heat transfer coefficient between his skin and the sea water is 30. The total surface area of the yachtsman is 2.2 and his metabolism continues to produce thermal energy at a rate of 180W. if the initial core temperature of the yachtsman is 36deg and the ocean water is at 5deg by how much will his core body temperature fall in the 30minutres before he is rescued ? (in K)
    Thermal conductivity of surface fat = 0.2
    heat capacity of human body = 3.49x10^3

    2. Relevant equations

    3. The attempt at a solution

    Hey. I got an exam tomorrow and im really confused as to answer this question. Like i dont understand what to calculate.. (conduction equation,convection etc) and how to deal with situations in which there are multiple layers (conduction through series I THINK), can somone please show me their working out and how they answer this question cheers.
  2. jcsd
  3. Apr 25, 2010 #2


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    Break it into sections. How is the heat transfer rate linked with the changing core temperature over time? How is the same rate linked with the temperature difference across the fat layer? How is the same rate linked with the heat transfer coefficient to the water?
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