Heat Rejection process of Carnot Refrigeration

In summary, the conversation discusses the classification of energy in the heat addition process of a Carnot Refrigeration Cycle using refrigerant-134a as the working fluid. The question is whether the energy should be classified as enthalpy or internal energy and why. The expert clarifies that enthalpy and internal energy are functions of the thermodynamic state of a system and are different from heat passing through the system's boundaries. For an ideal gas, internal energy is the sum of the kinetic energies of the molecules, while for a real gas, it includes energetic interactions between molecules. Enthalpy is defined as the sum of internal energy and the product of pressure and volume, and is often used as a convenient parameter in therm
  • #1
ChildLikEsper
2
0
Hi there, I just sign up today. I'm curious to know about the energy added/released in a Carnot Refrigeration Cycle. Let's say the problem is like this:

A Carnot Refrigerator used refrigerant-134a as the working fluid. During the heat addition process, a percentage of mass of the refrigerant vaporise.
​
So the question is how do we classify the energy in heat addition process? Is it enthalpy or internal energy? And why?
 
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  • #2
ChildLikEsper said:
Hi there, I just sign up today. I'm curious to know about the energy added/released in a Carnot Refrigeration Cycle. Let's say the problem is like this:

A Carnot Refrigerator used refrigerant-134a as the working fluid. During the heat addition process, a percentage of mass of the refrigerant vaporise.
​
So the question is how do we classify the energy in heat addition process? Is it enthalpy or internal energy? And why?
You are aware that enthalpy and internal energy are functions of the thermodynamic state of a system, and are inherently different from heat passing through the boundaries of a system, correct?
 
  • #3
Chestermiller said:
You are aware that enthalpy and internal energy are functions of the thermodynamic state of a system, and are inherently different from heat passing through the boundaries of a system, correct?

Can you elaborate on these, I may get these 2 terms confused.
 
  • #4
ChildLikEsper said:
Can you elaborate on these, I may get these 2 terms confused.
For an ideal gas, the internal energy is just the sum of the kinetic energies of all the molecules. For a real gas, the internal energy also includes attractive and repulsive energetic interactions between the molecules. The enthalpy is just a convenient parameter to work with in many kinds of problems, and has no fundamental significance. It is defined as H = U + PV.

chet
 

1. What is the heat rejection process in Carnot refrigeration?

The heat rejection process in Carnot refrigeration is the transfer of heat from the refrigerant to the environment. This occurs in the condenser of the refrigeration system, where the refrigerant is condensed from a gas to a liquid. The heat is rejected to the environment through the use of a heat exchanger or cooling tower.

2. Why is heat rejection important in Carnot refrigeration?

Heat rejection is important in Carnot refrigeration because it allows the refrigerant to release the heat it has absorbed from the cooled space. This process is necessary for the refrigerant to return to its original state and continue the cooling cycle. Without proper heat rejection, the refrigerant would not be able to cool the space effectively.

3. How does the heat rejection process affect the efficiency of a Carnot refrigeration system?

The heat rejection process has a significant impact on the efficiency of a Carnot refrigeration system. The amount of heat rejected in the condenser is directly related to the amount of work required by the compressor. Therefore, the more efficient the heat rejection process, the less work the compressor needs to do, resulting in a more efficient overall system.

4. What factors can affect the heat rejection process in Carnot refrigeration?

Several factors can affect the heat rejection process in Carnot refrigeration, including the type and condition of the heat exchanger, the temperature and flow rate of the cooling medium, and the ambient temperature. These factors can impact the rate at which heat is transferred from the refrigerant to the environment, ultimately affecting the overall efficiency of the refrigeration system.

5. How can the heat rejection process be optimized in Carnot refrigeration?

To optimize the heat rejection process in Carnot refrigeration, it is important to use high-quality heat exchangers and ensure they are properly sized for the system. Additionally, optimizing the flow rate and temperature of the cooling medium can help improve heat transfer. Regular maintenance and cleaning of the condenser and cooling tower can also help improve the efficiency of the heat rejection process.

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