Isothermal Process Curve for Steam

The question asks to identify the correct curve representing an isothermal process where wet steam is converted into superheated steam. This analysis is typically done on a Temperature-Entropy (T-s) diagram.

Characteristics of Isothermal Process on T-s Diagram

• An isothermal process occurs at a constant temperature.
• On a T-s diagram, a constant temperature process is represented by a horizontal line.

Steam State Changes

• Wet Steam: A mixture of saturated liquid and saturated vapor.
• Saturated Steam: Steam at the point of vaporization (pure vapor).
• Superheated Steam: Steam heated beyond its saturation temperature at a given pressure.

Process Explanation

When wet steam is heated isothermally:

1. Initially, heat addition causes the liquid phase to vaporize, turning the wet steam into saturated steam. This occurs at a constant saturation temperature.
2. As heating continues at the same constant temperature, the saturated steam becomes superheated steam.

Therefore, on a T-s diagram, the process starts within the saturation dome (wet region), crosses the saturation line, and continues into the superheated region, all along a line of constant temperature (a horizontal line).

Identifying the Correct Curve

The correct curve must be a horizontal line starting in the saturation region (representing wet steam) and extending into the region beyond the saturation dome (representing superheated steam), indicating a constant temperature process. Option 1 correctly depicts this horizontal path.