2 replies to this topic

[sacarove]

Dear all,

 

Can somebody explain why the entropy in an expander remains constant?

 

Thanks

Sacarove

[ankur2061]

Sacarove,

 

When you say expansion it is not clear. There are two types of expansion processes:

 

1. Free Expansion (throttling during pipe / valve flow) is not an isentropic (constant entropy) process. In this case no work is done by the gas. In free expansion the temperature of an ideal gas will not change but for a real gas it may either increase or decrease depending upon the initial pressure and temperature.

 

2. In turboexpanders useful work is extracted out of the expansion process, which means the expansion is reversible (adiabatic reversible process) and the gas is in thermodynamic equilibrium at all times. In turboexpansion the gas does positive work during the expansion and its temperature decreases. Hence it is an isentropic process

 

Some links from wikipedia are suggested for reading to get detailed explanation of expansion processes and what is adiabatic process

 

http://en.wikipedia..../Free_expansion

 

http://en.wikipedia....–Thomson_effect

 

http://en.wikipedia....i/Turboexpander

 

http://en.wikipedia....iabatic_process

 

Regards,

Ankur.

[sacarove]

Thank you so much Ankur.

 

Have a nice weekend ):