Thermodynamic question?

In summary, the Carnot cycle cannot achieve isothermal heating at constant pressure in the superheated region due to the working fluid not changing phase. However, the Rankine cycle allows for this by operating in the superheated region, despite it not being an ideal cycle. This is due to limitations in equipment.
  • #1
abhishek_sai81
4
0
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?
 
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  • #2
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).
 
  • #3


In a Carnot cycle, the isothermal heating process occurs at a constant temperature, which means that the pressure also remains constant. However, in practice, it is not possible to maintain a constant pressure during the heating process in the superheated region. This is because the superheated region is where the temperature is above the boiling point of the working fluid, and any increase in pressure would cause the fluid to transition from a gas to a liquid, resulting in a change in temperature.

On the other hand, in a Rankine cycle, the isothermal heating process can be achieved in the superheated region because the working fluid is in a liquid state and can absorb heat without changing its phase. This allows for a constant pressure to be maintained during the heating process, resulting in an isothermal process.

In summary, the difference between the Carnot and Rankine cycles lies in the state of the working fluid during the heating process. The Carnot cycle operates with a gas as the working fluid, while the Rankine cycle uses a liquid. This difference allows for the isothermal heating process to be achieved in the superheated region in the Rankine cycle, but not in the Carnot cycle.
 

1. What is thermodynamics?

Thermodynamics is the branch of physics that deals with the relationship between heat, work, temperature, and energy. It studies how these variables affect and relate to each other in physical systems, such as engines, refrigerators, and chemical reactions.

2. What are the laws of thermodynamics?

The laws of thermodynamics are fundamental principles that govern the behavior of energy in physical systems. The first law states that energy cannot be created or destroyed, only transferred or converted. The second law states that the total entropy (disorder) of a closed system always increases over time, and the third law states that the entropy of a perfect crystal at absolute zero temperature is zero.

3. What is the difference between heat and temperature?

Heat and temperature are often used interchangeably, but they are not the same thing. Heat is a form of energy that is transferred between two objects due to a temperature difference. Temperature, on the other hand, is a measure of the average kinetic energy of the particles in a substance.

4. How is thermodynamics used in real life?

Thermodynamics has many practical applications in our daily lives. It is used in the design and operation of engines, refrigerators, air conditioners, and other heat-powered devices. It is also crucial in chemical reactions, such as in the production of fertilizers and pharmaceuticals.

5. What are some common misconceptions about thermodynamics?

One common misconception is that the laws of thermodynamics only apply to closed systems, when in fact they also apply to open systems. Another misconception is that the second law of thermodynamics implies that everything in the universe is constantly getting worse and less organized, when it actually only applies to isolated systems without external energy inputs.

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