Which parameter primarily determines the saturation temperature of steam?

Which parameter primarily determines the saturation temperature of steam?

• A. Temperature
• B. Pressure
• C. Volume
• D. Entropy

Answer: (B)

Saturation temperature is the temperature at which liquid and vapor are in equilibrium for a given pressure. On the steam saturation curve, each pressure has its own unique saturation temperature, and that temperature rises as pressure increases up to the critical point. Because of this, pressure primarily determines the saturation temperature. Temperature alone isn’t enough to fix Tsat, since at the same temperature you could be dealing with subcooled liquid at high pressure or superheated steam at low pressure—the pressure tells you where you are on the saturation line. Volume and entropy define the state once you know whether you’re on the saturated line, subcooled, or superheated, but they don’t set the saturation temperature by themselves. For water, Tsat is 100 C at 1 atm and increases with pressure toward the critical point (374 C at the critical pressure).

Saturation temperature is the temperature at which liquid and vapor are in equilibrium for a given pressure. On the steam saturation curve, each pressure has its own unique saturation temperature, and that temperature rises as pressure increases up to the critical point. Because of this, pressure primarily determines the saturation temperature. Temperature alone isn’t enough to fix Tsat, since at the same temperature you could be dealing with subcooled liquid at high pressure or superheated steam at low pressure—the pressure tells you where you are on the saturation line. Volume and entropy define the state once you know whether you’re on the saturated line, subcooled, or superheated, but they don’t set the saturation temperature by themselves. For water, Tsat is 100 C at 1 atm and increases with pressure toward the critical point (374 C at the critical pressure).