# Why doesn't the stagnation temperature change in a stator?

• granzer
In summary, the conversation discusses the behavior of stagnation pressure and stagnation temperature in a rotary compressor. It is understood that both increase in the rotor stage, while in the stator stage, there is a loss of stagnation pressure but no change in stagnation temperature. It is suggested that the loss in stagnation pressure is converted into heat, but according to the classical gas law formula, a reduction in stagnation pressure results in a decrease in stagnation temperature. Additionally, the flow in the stator stage is adiabatic, meaning there is no mechanism for increasing total temperature. While there may be some minor effects that can lead to a recovery temperature, the overall total temperature remains constant in that region.
granzer
I am studying the rotary compressor and I have understood that the stagnation pressure and stagnation temperature both increase in the rotor stage (as energy is being added). I also read that in the stator stage the stagnation temperature remains a constant but there is loss of stagnation pressure. If there is a loss in stagnation pressure in the stator, shouldn't the stagnation temperature increase (I am guessing here that the stagnation pressure loss is converted into heat)?

Without seeing reference source, it is difficult to evaluate that statement. By the classical gas law formula, a reduction in stagnation pressure results in a reduction in stagnation temperature, not an increase.

The flow is adiabatic in the stator stage, so there is no mechanism for increasing total temperature. In a compressible flow, there is a mechanism for viscous dissipation in the boundary layer that can dissipate some of the enthalpy, leading to what is called a recovery temperature, but this is a very minor effect compared to the overall enthalpy in the flow and is most important when trying to predict or calculate heat transfer rates into the surface. Otherwise, in general, the total temperature remains constant as long as the flow is adiabatic in that region.

JBA

## 1. Why is the stagnation temperature constant in a stator?

The stagnation temperature remains constant in a stator because it is designed to have a fixed geometry, which means there is no change in the fluid's velocity or energy as it passes through. This ensures that the temperature remains constant.

## 2. How does the stator maintain a constant stagnation temperature?

The stator maintains a constant stagnation temperature through its design and function. As the fluid flows through the stator, it is directed and diffused in a way that ensures the energy and velocity remain constant, thus keeping the stagnation temperature constant as well.

## 3. Can the stagnation temperature change in a stator?

No, the stagnation temperature cannot change in a stator. As mentioned earlier, the stator's design and function are specifically meant to maintain a constant stagnation temperature. Any changes in the temperature would require a change in the stator's geometry, which is not possible during operation.

## 4. What is the significance of a constant stagnation temperature in a stator?

A constant stagnation temperature in a stator is crucial for maintaining the efficiency and performance of the system. It ensures that the fluid entering the rotor has a consistent energy and velocity, which is necessary for the proper functioning of the turbine or compressor.

## 5. Does the stagnation temperature change in a stator affect the overall performance?

Yes, any change in the stagnation temperature in a stator can significantly impact the overall performance of the system. It can lead to a decrease in efficiency and output, as well as potential damage to the components. Therefore, it is essential to maintain a constant stagnation temperature in a stator for optimal performance.

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