Why Aren't Carnot Engines Considered Real Engines?

[Soaring Crane]

In class, we're being introduced to thermodynamics, and one of the topics is heat engines.

Steam engines were also mentioned.

Carot engines also entered the pic. They are described as ideal systems. Exactly why are Carnot engines not "real" engines, or are not possible?

I'm sorry if these inquiries sound stupid.
Does anyone know of any good Internet sites on heat engines or any images that may help be understand better?

Thanks. :shy:

 

[brewnog]

As you rightly say, the Carnot cycle is an 'ideal' one. We think of it as the most efficient cycle which could be used in an engine. It is conceptual. The efficiency determned by such a cycle is dependent only upon the difference in temperatures of the 'reservoirs' between which it operates.

The reason this is not a practical cycle (i.e it cannot be employed physically) is because it is based upon the use of reversible 'ideal' processes, and in the real world this does not occur. Efficiencies of various kinds of real world engines are often compared to their associated Carnot efficiency, which is the highest efficiency theoretically obtainable.

Have a look at this link for a starter:
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html

After that, have a google with the first, second, third (and zeroth) laws of thermodynamics, there's plenty of stuff out there.

 

[wais]

No worries, your inquiries are not stupid at all! In fact, it's great that you're curious and seeking more information to understand the topic better.

To answer your question, Carnot engines are considered ideal systems because they operate under certain assumptions that are not possible to achieve in real-life engines. These assumptions include having a perfectly insulated system, a perfectly reversible process, and no friction or energy losses. These conditions are not possible to achieve in real engines, hence why they are not considered "real" engines.

Some good internet sites that can provide more information on heat engines and Carnot engines include Khan Academy, HyperPhysics, and Engineering Toolbox. As for images, a simple Google search for "Carnot engine diagram" or "heat engine cycle" should provide some helpful visual aids.

Keep exploring and asking questions, it's the best way to learn and understand new concepts!