How does temperature change during steam expansion in an impulse turbine?

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During the expansion of steam in an impulse turbine, the temperature can indeed decrease depending on the system conditions, such as pressure and humidity. As steam expands through the turbine, it converts thermal energy into kinetic energy, which manifests as a decrease in pressure and often leads to a reduction in temperature. This phenomenon is primarily described by the principles of thermodynamics, particularly the ideal gas law and the relations governing the enthalpy and entropy of steam.

The process of steam expansion in an impulse turbine allows the steam to do work on the blades of the turbine, which results in energy conversion. If the initial pressure of the steam is significantly higher than the pressure in the turbine, the swift expansion typically results in a drop in both pressure and temperature — a characteristic behavior of steam as it undergoes work extraction processes.

In contrast to the other options, the notion that the temperature increases throughout the expansion process does not align with thermodynamic principles, as there isn’t a heat input involved in an impulse turbine during expansion. Suggesting that the temperature remains constant overlooks the fundamental changes occurring during the expansion, and proposing that it fluctuates randomly misrepresents the systematic nature of steam behavior governed by enthalpy and pressure relationships in a turbine setting.

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