Thermodynamics heat transfer problem

In summary, a 85kg yachtsman falls into the ocean and begins to lose body heat through a 0.02m thick layer of surface fat. The surface heat transfer coefficient is 30 and the total surface area of the yachtsman is 2.2. His metabolism continues to produce thermal energy at a rate of 180W. With an initial core temperature of 36deg and ocean water at 5deg, it can be calculated that his core body temperature will fall by a certain amount in the 30 minutes before he is rescued. This calculation involves considering the thermal conductivity of the surface fat, the heat capacity of the human body, and the various factors that affect the heat transfer rate, such as temperature difference
  • #1
luysion
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Homework Statement



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


Homework Equations





The Attempt at a Solution



Hey. I got an exam tomorrow and I am really confused as to answer this question. Like i don't 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.
 
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  • #2
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?
 

1. What is the difference between heat and temperature?

Heat is a form of energy that is transferred from one object to another due to a temperature difference. Temperature, on the other hand, is a measure of the average kinetic energy of the particles in a substance. In simpler terms, heat is the transfer of energy, while temperature is a measure of the amount of energy present in a substance.

2. How does heat transfer occur in thermodynamics?

Heat transfer in thermodynamics occurs through three main mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two objects, while convection is the transfer of heat through the movement of fluids such as air or water. Radiation is the transfer of heat through electromagnetic waves.

3. What is the first law of thermodynamics?

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another. This means that in any thermodynamic process, the total amount of energy remains constant.

4. What is the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system always increases over time. Entropy is a measure of the disorder or randomness in a system. This law also implies that heat will always flow from a hotter object to a cooler object, and it is impossible to have a completely efficient heat engine.

5. How is heat transfer related to work in thermodynamics?

In thermodynamics, heat and work are both forms of energy transfer. Heat is the transfer of thermal energy, while work is the transfer of mechanical energy. The first law of thermodynamics relates these two forms of energy transfer, stating that the total change in internal energy of a system is equal to the sum of heat and work done on or by the system.

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