part (b) gpt - Flashcards
property tables,
Q: What is internal energy?
A: internal energy (𝑢) is the molecular energy possessed by a substance, including the microscopic kinetic energy of molecules and potential energy related to intramolecular forces
Q: What is enthalpy?
A: Enthalpy is the sum of the internal energy and the product of pressure and volume in a thermodynamic system. It is a measure of the total heat content of the system and is used in analysing open systems, such as boilers and heat exchangers.
Q: What is enthalpy measured in?
A: It is measured in kilojoules per kilogram (kJ/kg).
Q: What is entropy and what is it measured in?
A: Entropy is a thermodynamic property that represents the unavailability of a system’s thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system. It is measured in kilojoules per kilogram per Kelvin (kJ/kg·K).
Q: What is the equation for specific enthalpy?
A: Specific enthalpy (ℎ) is given by the equation
ℎ=𝑢+𝑃𝑣, where 𝑢 is the internal energy, P is the pressure, and
𝑣 is the specific volume.
Q: What is a compressed liquid?
A: A compressed liquid is a liquid that is not about to vaporize. It is under a pressure greater than
the saturation pressure for its temperature.
Q: What is a subcooled liquid?
A: A subcooled liquid is a liquid that is at a temperature below its saturation temperature at a given
pressure. Since it is “subcooled,” it means that the liquid is cooled below the point where it would
start to vaporize at a given pressure. (e.g. liquid nitrogen)
Q: What is superheated water?
A: Superheated water refers to water that is in the vapor phase at a temperature higher than its saturation temperature for a given pressure.
Q: What is the critical point of a pure substance?
A: The critical point is the temperature and pressure at which the liquid and gas phases of a substance become indistinguishable, resulting in a supercritical fluid.
Q: What is the dryness fraction or quality (x) of a liquid-vapour mixture?
A: The dryness fraction (𝑥) is the ratio of the mass of vapor to the total mass of a liquid-vapour mixture, indicating how much of the substance is in the vapor phase.
During a vaporization process a substance exits as a mixture of saturated liquid and saturated vapour. To analyze this mixture properly we need to know the proportions of the liquid and vapour phases in the mixture.
This is done by defining a new property called the dryness fraction or quality (x)
Q: How are properties of pure substances typically presented in thermodynamics?
A: Properties like pressure, temperature, specific volume, internal energy, enthalpy, and entropy are often presented in property tables due to the complexity of their relationships.
