Understanding Entropy: From Thermodynamics to Transport Equations

In summary, the conversation discusses the relationship between the second law of thermodynamics and entropy. It explains that all thermodynamic systems can be seen as a reservoir and provides an expression for change in entropy. The question is raised about how one can obtain this expression from the Stefan-Boltzmann law. It is also mentioned that entropy is a thermodynamic equilibrium property while the Stefan-Boltzmann equation is a transport equation. The two are unrelated and the speaker asks for recommended reading on the topic.
  • #1
shonen
8
0
From second law of thermodynamics one can obtain an expression for change in entropy of a system developed by Classius.

All thermodynamic systems can be looked at as a reservoir.

ds=[tex]\oint[/tex]DQ/T---(1)

Ds- Change in entropy in the system brought about by reversible heat transfer between system, and surrounding, during some time dt
DQ- Heat transfer either absorbed or removed from system during some time dt.
T- Temperature of reservoir

Now, question is how does one reach from this general expression formed form Stefan-Boltmzman law, corresponding entropy.

DQ=[tex]\epsilon[/tex][tex]\sigma[/tex](Te^4- Ts^4)

Te- Surface Temperature of the surface
Ts- Surface temperature of the body

Ds= 4/3[tex]\epsilon[/tex][tex]\sigma[/tex](Te^3-Ts^3)

Also its puzzling as well how one can obtain this expression as well for how one can obtain the following expression for entropy in this form.

NRln(Pf/Po)=ds

Any recommended reading text will be appreciated.
 
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  • #2
Entropy is a thermodynamic equilibrium property and the Stefan-Boltzmann equation is a transport equation. The two are unrelated.
 

1. What is energy entropy?

Energy entropy is a measure of the amount of energy that is unavailable for useful work in a system. It represents the randomness and disorder in a system, and is often referred to as the "disorder" of a system.

2. How is energy entropy calculated?

Energy entropy is calculated by taking the natural logarithm of the number of possible microstates in a system, multiplied by the Boltzmann constant. This calculation can be applied to any physical system, including gases, liquids, and solids.

3. What is the relationship between energy entropy and temperature?

The relationship between energy entropy and temperature is that as the temperature of a system increases, the energy entropy also increases. This means that as a system becomes more disordered, its temperature also increases.

4. Can energy entropy be reversed?

No, energy entropy cannot be reversed. The second law of thermodynamics states that the total entropy of an isolated system will always increase over time, and cannot decrease. This means that the randomness and disorder of a system will always tend to increase, and cannot be reversed.

5. How does energy entropy affect the efficiency of energy conversion?

Energy entropy has a direct impact on the efficiency of energy conversion. As the energy entropy of a system increases, the efficiency of converting energy into useful work decreases. This is because a greater amount of energy is lost as heat due to the disorder of the system.

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