# Internal/external energy in compressor

• gumpfer
In summary: Expert SummarizerIn summary, thermodynamics is a highly abstract concept used to explain the behavior of systems like compressors. Compressors are mechanical devices used to increase the pressure of a gas, and the principles of thermodynamics are applied in their design and analysis. The specific heat difference, or external work, refers to the energy required to compress a gas, and it is different from the external work done by a gas engine running a generator.
gumpfer
This is about how to relate an abstraction of thermodynamics to a real compressor. The difference of the specific heats is called "external work" since in the legendary cylinder holding a pound of air being heated one degree, the spec heat capacity at constant pressure is this much more than the internal energy due to the piston having to push away the atmosphere to move and let the air inside expand.

My question is, how does this relate to a real compressor, and isn't it true that the term "external work" as in "The gas engine did the external work of running the generator," is a different usage of the same words?

Thanks.
Gumpfer

Dear Gumpfer,

Thank you for your question about the relationship between thermodynamics and real compressors. I am glad to see your interest in this topic.

To start off, let's define what we mean by "abstraction of thermodynamics." Thermodynamics is a branch of physics that deals with the relationships between heat, energy, and work. It is a highly abstract concept that is used to explain the behavior of various systems, including compressors. In thermodynamics, we use mathematical models and equations to describe the behavior of these systems.

Now, let's talk about compressors. A compressor is a mechanical device that is used to increase the pressure of a gas by reducing its volume. This process is essential in many industrial and commercial applications, such as refrigeration, air conditioning, and gas turbines.

So, how does the abstraction of thermodynamics relate to a real compressor? Well, the principles of thermodynamics are used to design and analyze the performance of compressors. For example, the first and second laws of thermodynamics are used to determine the efficiency of a compressor and the amount of work required to compress a gas.

The specific heat difference, also known as "external work," is a term used in thermodynamics to describe the energy required to move a gas from one state to another. In the case of a compressor, this refers to the work done by the piston to push the gas and compress it. This external work is necessary to overcome the resistance of the atmosphere and other external forces.

Lastly, you asked if the term "external work" has a different meaning in the context of a gas engine running a generator. In this case, the term is used to describe the work done by the engine to produce electricity. This is different from the external work in a compressor, which refers to the work done to compress a gas.

I hope this helps to clarify the relationship between thermodynamics and real compressors. If you have any further questions, please don't hesitate to ask.

## 1. What is internal energy in a compressor?

Internal energy in a compressor refers to the total energy stored within the compressor system, including the kinetic and potential energy of the compressor's moving parts and the thermal energy of the compressed gas. It is a measure of the energy available to do work or cause changes in the system.

## 2. How is internal energy different from external energy in a compressor?

Internal energy is the energy contained within the compressor system, while external energy refers to the energy transferred to or from the compressor from an external source. In other words, internal energy is inherent to the compressor itself, while external energy is introduced into the system from outside.

## 3. What factors affect the internal energy of a compressor?

The internal energy of a compressor is affected by several factors, including the type and design of the compressor, the type of gas being compressed, the speed and efficiency of the compressor, and the temperature and pressure of the gas being compressed. Additionally, any external energy inputs, such as electricity or heat, can also impact the internal energy of the compressor.

## 4. Why is it important to consider internal energy in compressor design?

Internal energy is a crucial factor in compressor design because it directly affects the performance and efficiency of the compressor. Understanding and managing internal energy allows for the optimization of the compressor system, resulting in improved energy efficiency, reduced operating costs, and increased equipment lifespan.

## 5. How can the internal energy of a compressor be controlled?

The internal energy of a compressor can be controlled through various methods, including proper maintenance and lubrication of the compressor, optimizing the compressor design and operating conditions, and using energy-efficient components and technologies. Additionally, implementing energy management strategies, such as heat recovery and waste heat utilization, can also help to control the internal energy of a compressor.

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