Thermodynamic question?

[abhishek_sai81]

in carnot cycle isothermal heating at constant pressure cannot be achieved in practice in superheated region why?but in case of raNKINE cycle it can be obtained, WHY?

 

[Q_Goest]

Hi abhishek.

in carnot cycle isothermal heating at constant pressure cannot be achieved in practice in superheated region why?

Isothermal heating requires that your working fluid change phase. If the fluid is in the superheated region, it isn't changing phase, so it isn't isothermal. Adding energy to a working fluid in the superheated region results in the temperature increasing.

but in case of raNKINE cycle it can be obtained, WHY?

Adding heat in the superheated region doesn't change for any cycle. Adding heat to a superheated fluid will increase the fluid's temperature. The Rankine allows fluid to operate in this superheated region. The Carnot cycle does not. This web page shows a Carnot cycle versus a "real" cycle:
http://en.wikipedia.org/wiki/Image:Real_vs_Carnot.jpg
Limitations, primarily on equipment, forces us to work with a "real" cycle (Rankine cycle).