Heat engine operations

Your name]In summary, the maximum temperature that one of the bodies can be raised to by the operation of heat engines is determined by the Second Law of Thermodynamics. While a less efficient heat engine may transfer more heat to another body, efficiency is important in order to obtain useful work from a given amount of input heat. Therefore, in the case of three identical bodies, an efficient heat engine is necessary to achieve the maximum temperature while minimizing the input heat.
  • #1
sachi
75
1
we have 3 identical bodies of constant thermal capacity, two at 300K and one at 100k. we want to know the highest temperature that anyone of the bodies can be raised by the operation of heat engines.
we already solved this problem in a tute, and we assumed the heat engines were reversible so that there was no change in entropy. The physics is confusing me, though. Why do we want our heat engines to be efficient? Surely for the max. amount of heat transfer to another body we want an inefficient heat engine so that the min. possible input heat is converted to work?
thanks very much.
 
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  • #2

Thank you for your question about the maximum temperature that one of the bodies can be raised to by the operation of heat engines. I can understand your confusion about the efficiency of heat engines and their role in maximizing heat transfer.

Firstly, let me clarify that the maximum temperature that one of the bodies can be raised to is determined by the laws of thermodynamics, specifically the Second Law. This law states that heat cannot spontaneously flow from a colder body to a hotter body. This means that a heat engine, no matter how efficient, cannot raise the temperature of one of the bodies higher than the temperature of the hottest body.

Now, to address your question about the efficiency of heat engines, it is true that a less efficient heat engine would transfer more heat to another body compared to a more efficient one, assuming the same amount of input heat. However, this is not the whole picture. Efficiency is important because it determines the amount of useful work that can be obtained from a given amount of input heat. In other words, a more efficient heat engine can convert a larger portion of the input heat into useful work, while a less efficient one would waste more heat.

In the case of the three identical bodies, we want to maximize the temperature of one of the bodies while minimizing the input heat. This can only be achieved by using an efficient heat engine, as a less efficient one would require more input heat to produce the same amount of work. Therefore, efficiency is crucial in this scenario to achieve the maximum temperature with the minimum input heat.

I hope this explanation helps to clarify your confusion. If you have any further questions, please do not hesitate to ask.
 

1. How does a heat engine work?

A heat engine works by converting thermal energy into mechanical work. This is typically achieved by using a fuel source to heat a fluid, such as water or steam, which then expands and pushes against a piston or turbine, generating power.

2. What are the main components of a heat engine?

The main components of a heat engine include a fuel source, a heat source, a working fluid, a compressor or pump, and a mechanical output, such as a piston or turbine. These components work together to convert heat energy into mechanical work.

3. What is the difference between an internal combustion engine and an external combustion engine?

An internal combustion engine burns fuel directly inside the engine, while an external combustion engine burns fuel outside of the engine, using the resulting heat to power the engine. Examples of internal combustion engines include gasoline and diesel engines, while external combustion engines include steam engines and Stirling engines.

4. How is the efficiency of a heat engine calculated?

The efficiency of a heat engine is calculated by dividing the work output by the heat input. This is known as the thermal efficiency and is typically expressed as a percentage. The higher the thermal efficiency, the more efficient the heat engine is at converting heat into work.

5. Can a heat engine operate at 100% efficiency?

No, a heat engine cannot operate at 100% efficiency due to the laws of thermodynamics. The maximum theoretical efficiency of a heat engine is determined by the Carnot cycle, and is based on the temperatures of the heat source and heat sink. Real-world heat engines typically have efficiencies much lower than the Carnot efficiency, due to factors such as heat loss and friction.

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