Entropy Generation in a Rod: Heat Transfer Considerations

In summary, the conversation discusses the concept of entropy generation and heat transfer in an insulated rod. The temperature gradient in the rod is given by an equation, and the question is raised about whether entropy is generated within the rod during heat transfer. The speaker argues that there should be no entropy generation since heat transfer occurs at a temperature difference approaching zero. The other person points out that the second law of thermodynamics still applies and that there will still be an increase in entropy. However, this increase is attributed to the heat transfer itself, not due to any irreversibility.
  • #1
kittu1421
10
0
Hi..
Consider a rod which is insulated on its lateral surface, now this rod is brought in contact with a source at temperature T1 and sink at temperature T2 now a temperature gradient sets up in the rod after steady state is reached temperature at some distance X from the source end is given as
T=T1-(T1-T2)*X/L
now this rod is removed and ends are insulated as well
then my question is as heat flows from high temp. region to low temp. region is any entropy generated within the rod...?
what i feel is it should not because there are no irreversibility in the rod during heat transfer, even the heat transfer across any rod element takes place at temp. difference tending to zero, hence in eqn.
ds=δq/T+Δsgen, Δsgen should be zero so that eqn. becomes
ds=δq/T
check me if i am correct and if i have missed something notify me.
 
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  • #2
Your argument is that if an isolated system is not at equilibrium, it will not move toward equilibrium with time (since that obviously would increase entropy)? Seriously?! S = ∫dQ/T and you think the heat flow magically stops once the ends are insulated? I draw your attention to the second law of thermodynamics. (as well as the zeroth law).
 
  • #3
Entropy will increase but that increase will be due to heat transfer from hot end to cold end and not because of some generations due to irreversibility and that's what i have said above in last equation i have taken entropy generatio(Sgen=0) and not change in total entropy equal to zero(dS!=0)
 

1. What is entropy generation in the context of heat transfer in a rod?

Entropy generation refers to the increase in the level of disorder or randomness within a system. In the case of heat transfer in a rod, entropy generation occurs due to the dissipation of heat energy and the resulting increase in thermal chaos.

2. How does entropy generation affect the efficiency of heat transfer in a rod?

High levels of entropy generation can lead to a decrease in the efficiency of heat transfer in a rod. This is because the dissipation of heat energy results in a loss of usable thermal energy, making it more difficult for the rod to maintain a steady temperature gradient.

3. What factors contribute to entropy generation in a rod?

Entropy generation in a rod can be influenced by a variety of factors, including the material properties of the rod, the rate of heat transfer, and the temperature difference between the two ends of the rod. Other factors such as surface roughness, convective heat transfer, and thermal resistance also play a role.

4. How can entropy generation be minimized in a rod for improved heat transfer?

There are several ways to reduce entropy generation in a rod, including improving the thermal conductivity of the material, reducing the temperature difference between the two ends of the rod, and increasing heat transfer by using fins or other heat transfer enhancement techniques. Proper insulation and minimizing surface roughness can also help reduce entropy generation.

5. What are the practical applications of understanding entropy generation in heat transfer in a rod?

Understanding entropy generation in heat transfer can help engineers and scientists design more efficient heat transfer systems, such as heat exchangers and cooling systems. It can also aid in the development of more effective insulation materials and techniques. Additionally, studying entropy generation can provide insights into the fundamental laws of thermodynamics and their application in real-world scenarios.

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