Refrigeration theory: Why does the compression follow an isentrope?

In summary, the conversation discusses the concept of isentropic compression and its relation to entropy. It is explained that in ideal conditions, the compression will follow an isentropic line on a h,log(p)-diagram. However, in real life, the compressors have an efficiency of 0.8, causing deviation from the ideal path. This is due to irreversibility caused by fluid friction and friction between cylinder wall and piston. It is also mentioned that the compressor should ideally follow an isentropic path to avoid any heat generation and violation of the 2nd law of thermodynamics. It is clarified that the compressor does heat up the refrigerant during the compression process.
  • #1
EVriderDK
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When you have a perfect compressor the compression will follow an isentropic line and an h,log(p)-diragram (enthalpy,pressure diagram) but why? What is entropy exactly and what does it mean in such a system?

In real life the compressors have an isentropic efficiency of maybe 0.8, which will make the compression on the diagram deviate from the isentropic path. But why? Is it just because the friction etc. in the compressor heats up the refrigerant?
 
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  • #3
Hey I do not think that it does.
 
  • #4
Compression process is isentropic(ideally),isentropic means that process is entirely reversible and adiabetic.
adiabetic means no heat transfer,this can be achieved via proper insulation etc.now coming to the irreversibility,fluid friction and friction between the cylinder wall and Piston are the causes of irreversibility that causes a compressor to deviate from isentropic path..
why compressor should follow isentropic path? ans: "ideally" compressor is not generating any heat,no losses at all,all the energy given to compressor is transferred to fluid.therefore,entropy change is zero(which violates the 2nd law of thermodynamics)
compressor heats up the refrigerant? and: yes,in comprsr with pressure,temp of ref also increases.
 

1. Why is compression necessary in refrigeration?

In refrigeration, compression is necessary to increase the pressure and temperature of the refrigerant gas so that it can easily release heat and condense into a liquid form. This process is vital in maintaining a continuous cycle of cooling and heating.

2. What is an isentrope in refrigeration theory?

In refrigeration theory, an isentrope is a thermodynamic process in which the refrigerant gas is compressed without any heat transfer, resulting in a constant entropy. This means that the compression occurs without any energy loss or gain.

3. How does an isentropic compressor affect the efficiency of a refrigeration system?

An isentropic compressor is highly efficient in a refrigeration system because it compresses the refrigerant gas without any energy loss. This results in a higher coefficient of performance (COP) and reduces the amount of work required for compression, thus improving the overall efficiency of the system.

4. What factors can affect the isentropic compression process in refrigeration?

There are several factors that can affect the isentropic compression process in refrigeration, such as the type of refrigerant used, ambient temperature, compressor design, and the condition of the refrigeration system. These factors can impact the efficiency and performance of the isentropic compressor.

5. Can an isentropic compressor operate at any pressure and temperature?

No, an isentropic compressor has limitations on the pressure and temperature at which it can operate effectively. If the pressure or temperature exceeds the compressor's capabilities, the process will not follow an isentrope, and the efficiency of the compressor will decrease.

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