Thermodynamics: isentropic efficiency and ideal gas model

In summary, the conversation discusses the expansion of air at 1175 K and 8 bar through a turbine with an isentropic efficiency of 92%. Using the ideal gas model with k=1.4, the work developed by the turbine is determined to be 486 kJ/kg and the temperature at the exit is 691 K. However, a different solution found on another website yields different answers, possibly due to discrepancies in the tables used for finding enthalpy or an error in the units of temperature. The correct answers cannot be determined without further clarification.
  • #1
jofree87
38
0
Air at 1175 K, 8 bar enters a turbine operating at steady state and expands adiabatically to 1 bar. The isentropic turbine efficiency is 92%. Employing the ideal gas model with k=1.4 for the air, determine (a) the work developed by the turbine, in kJ per kg of air flowing, and (b) the temperature at the exit, in K. Ignore kinetic and potential energy effects.

The answers my professor provided are W = 486 kJ/kg, and T2 = 691 K

I found a solution (attached below) on another website that comes up with different answers. The work on the solution looks to be correct, but why do the answers differ? Which answers are correct?
 

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  • #2
maybe the tables used for finding enthalpy from temperature is different. are you sure about the credibility of the image? the guy has the units of temperature wrong ( mayb just a silly mistake).
 

FAQ: Thermodynamics: isentropic efficiency and ideal gas model

What is thermodynamics and why is it important?

Thermodynamics is the branch of physics that deals with the study of energy and its transformations. It is important because it helps us understand how energy moves and changes within a system, which is essential for many fields such as engineering, chemistry, and biology.

What is isentropic efficiency and how is it calculated?

Isentropic efficiency is a measure of how well a process or machine is able to convert energy without any loss. It is calculated by dividing the actual work or energy output by the maximum possible work or energy output as predicted by the isentropic process model.

What is the ideal gas model and how is it used in thermodynamics?

The ideal gas model is a simplified model that describes the behavior of gases at low pressures and high temperatures. It assumes that gas molecules have no volume and do not interact with each other, making it easier to analyze and predict their behavior in thermodynamic processes.

How does entropy relate to thermodynamics?

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it is closely related to the second law which states that the total entropy of a closed system will always increase over time. This law helps us understand the direction and efficiency of energy transformations.

What are some real-life applications of thermodynamics?

Thermodynamics has numerous practical applications, such as in the design and operation of engines, refrigerators, power plants, and chemical processes. It is also used in fields such as meteorology, astrophysics, and materials science to study energy transfer and transformations on a larger scale.

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