Saturation 2 Flashcards
True/False: A vapor that is about to condense is superheated vapor; otherwise it is saturated vapor.
False because if a vapor is about to condense it is at the saturation point. Liquid vapor is in equilibrium with its liquid phase (at boiling point), any additional heat will cause it to start condensing.
True/False: Quality might have some meaning in the superheated vapor region.
False because quality is defined as the ratio of the mass of vapor to the total mass of a mixture of liquid and vapor.
True/False: Saturated liquid is alternatively referred to as compressed liquid.
False because a saturated liquid is at the threshold of vaporisation, while a compressed liquid is simply a liquid at a higher pressure than its boiling point at that temp.
True/False: Temperature and pressure are dependent properties in the saturated mixture region.
True
True/False: For a gas modelled as an ideal gas, cv =cp+R, where R is the gas constant for the gas.
False
True/False: The reference point selected for the properties of a substance has no effect on thermodynamic analysis.
False because In the thermodynamic analysis we deal with the changes in the properties, and the changes are independent of the selected reference state.
True/False: As pressure increases toward the critical pressure, the values of vf and vg approach each other.
True
True/False: The term hf g represents the amount of energy needed to vaporize a unit mass of saturated liquid at a specified temperature or pressure.
True
True/False: If the pressure of a substance is increased during a boiling process, the temperature decreases.
False because in a boiling process if you increase the pressure, temp also increases to maintain the boiling process.
True/False: The amount of heat absorbed as 1 kg of saturated liquid water boils at 100°C has to be equal to the amount of heat released as 1 kg of saturated water vapor condenses at 100°C.
True because the saturated liquid absorbs the latent heat of vaporisation and the saturated vapor releases the latent heat of condensation. Since energy is conserved in a close system, the heat absorbed and the heat released must be equal.
True/False: A two-phase liquid–vapor mixture with equal volumes of saturated liquid and saturated vapor has a quality of 0.5.
False, the definition of quality is based on mass not volume.
True/False: It takes more energy to vaporize 1 kg of saturated liquid water at 100°C than it would at 120°C
False and The higher the temperature the lower the hfg value.
True/False: The quality of a system consisting of a two-phase liquid–vapor mixture of 5 kg of Refrigerant 134a in which one kg is saturated liquid is 20%.
False
True/False: It is impossible to have water vapor at −10°C.
False because ice can still sublimate (transition from solid directly to vapor) even in sub-zero conditions.
True/False: The pressures listed in thermodynamic tables are absolute pressures, not gage pressures.
True
True/False: Atmospheric air is normally modelled as an ideal gas
True
True/False: The point where the saturated liquid and the saturated vapor states are identical is called the supercritical point.
False because it is at the critical point.
True/False: In what kind of pot will a given volume of water boil at a higher temperature?
A given volume of water will boil at a higher temperature in a tall and narrow pot since the pressure at the bottom (and thus the corresponding saturation pressure) will be higher.
True/False: A liquid that is about to vaporize is saturated liquid; otherwise it is compressed liquid.
True
True/False: Completely vaporizing 1 kg of saturated liquid water at 1 atm pressure requires more energy than completely vaporizing 1 kg of saturated liquid water at 8 atm pressure.
True, Completely vaporizing 1 kg of saturated liquid water at 1 atm pressure requires more energy since the higher the pressure, the lower the h subscript f g end subscript.
T/F: In the absence of compressed liquid tables, the compressed liquid can be approximated as a saturated liquid at a given pressure.
False because saturated liquids are at the brink of phase change, while compressed liquids are not. There thermodynamic properties vary with pressure.
T/F: Water boils at higher temperature at higher pressure.
True
A man is cooking beef stew for his family in a pan. When will the cooking time be the shortest?
when the pan is covered with a heavy lid. Heavier the lid, the greater the pressure in the pan, and thus greater the cooking temperature.
A man is cooking beef stew for his family in a pan. When will the cooking time be the shortest?
when the pan is covered with a heavy lid. Heavier the lid, the greater the pressure in the pan, and thus greater the cooking temperature.
Under steady operation, what work is done on a simple compressible system.
shaft work and electrical work are the only forms of work
Name devices that are steady-flow
devices.
Nozzles and Diffusers
Turbines and Compressors
Throttling Valves
Mixing chambers
Heat Exchangers
What is a nozzle
A nozzle is a device that increases the velocity of a fluid at the expense of pressure
What is a diffuser
A diffuser is a device that increases the pressure of a fluid by slowing it down.
