Saturation 1 Flashcards
At what state is the pressure of water at 30ºC the lowest?
Superheated vapor
If a steam mixture with a quality of 0.2 undergoes a constant pressure heating process, what happens to the specific internal energy of the system?
It increases as the proportion of liquid decreases.
What is the quality of a saturated mixture of water at 100°C and atmospheric pressure (1 atm)?
The quality (x) of the mixture is between 0 and 1.
An ordinary glass of water at room temperature is at a state of
Compressed liquid and Subcooled liquid
If a saturated liquid is heated at constant pressure, what happens first?
The liquid evaporates while the temperature remains constant.
For a superheated vapor is P greater or less than Psat.
Superheated vapor: P is less than 𝑃sat at a given T.
A vapor that is not about to condense is called a
Superheated vapor
A vapor that is about to condense is called a
Saturated vapor
Given a mixture of water at 120°C and 100 kPa, which of the following can be inferred?
The mixture is superheated steam.
A typical sealed bottled water at room temperature is at a state of:
Compressed liquid and Subcooled liquid
What is the definition of latent heat of vaporization at a given pressure for a saturation mixture?
It is the energy required to convert saturated liquid into saturated vapor.
In a thermodynamic cycle, if the working fluid leaves the boiler as a saturated vapor and enters the turbine, what effect would a reduction in boiler pressure have on the cycle efficiency?
Efficiency will decrease. Lowering the boiler pressure reduces the enthalpy drop across the turbine, decreasing the work output and thus the cycle efficiency.
In a closed vessel containing a saturated liquid-vapor mixture of water at equilibrium, what will happen to the vapor quality if the volume of the vessel is reduced while maintaining constant temperature?
The vapor quality will decrease.
For a substance undergoing an adiabatic expansion in the two-phase region (saturated mixture), how does the pressure change affect the temperature of the mixture?
The temperature decreases as the pressure drops.
Water is boiled at a constant pressure of 90 kPa. How much heat need to be transferred to one kg water to turn it into vapor? 𝑞 = 𝑢𝑓𝑔 @ 90 kPa
𝑞=hfg@ 90 kPa
At 1 atm, water boils at 100°C. If heat is added to saturated steam at 1 atm, what happens?
The steam becomes superheated and its temperature increases.
A mixture of water and steam has a quality of 0.4 at 150°C. Which of the following best represents the fraction of the total volume occupied by the vapor?
More than 0.4. Even though the quality represents the mass fraction of vapor, the vapor phase occupies a much larger volume due to its lower density compared to the liquid.
Which thermodynamic property remains constant during the vaporization of a saturated mixture at constant pressure?
Temperature
A piston-cylinder contains a saturated mixture of water at 200 kPa. If heat is added to the system at constant pressure, what happens to the specific volume of the system?
It increases.
What would happen to the specific volume of a saturated liquid-vapor mixture if the pressure is increased while keeping the temperature constant?
The specific volume will decrease.
For a given saturation temperature, what decreases as the quality of a mixture increases?
Mass of the liquid phase
At which two states are the temperatures of a pure substance at a specified pressure equal?
Saturated vapor and Saturated liquid
At what state is the temperature of water at 1 atm pressure the lowest?
Compressed liquid
Given a saturated mixture of water at a specific pressure, how does increasing the quality (x) affect the internal energy (u) of the mixture?
Internal energy increases as the proportion of vapor increases.
What is an Compressed liquid (subcooled liquid)?
A substance that it is not about to vaporize.
What is an Saturated liquid?
A liquid that is about to vaporize.
What is an Saturated liquid–vapor mixture?
Saturated liquid–vapor mixture: The state at which the liquid and vapor phases coexist in equilibrium.
What is a Saturated vapor?
Saturated vapor: A vapor that is about to condense.
What is a Superheated vapor?
Superheated vapor: A vapor that is not about to condense (that is not a saturated vapor).
What is saturation pressure/temp?
Saturation temperature Tsat: The temperature at which a pure substance changes phase at a given pressure.
Saturation pressure Psat: The pressure at which a pure
substance changes phase at a given temperature.
What is latent heat
Latent heat: The amount of energy absorbed or released during a phase-change process.
What is latent heat of vaporisation
Latent heat of vaporization: The amount of energy absorbed during vaporization, and it is equivalent to the energy released during condensation.
What is the critical point
Critical point: The point at which the saturated liquid and
saturated vapor states are identical.
Definition of quality
Quality, x: The ratio of the mass of vapor to the total mass of the mixture.
What is the first law of thermodynamics?
The first law states that energy can be neither created nor destroyed during a process; it can only change forms.
A closed system involves what?
A closed system involves only heat transfer and work.
