Quality: The ratio of saturated vapor mass against total mass of a substance in a system. Above the critical temperature, no amount of pressure will force condensation to occur. Adding heat raises it temperature, removing heat lowers its temperature.Ĭritical point: The temperature and pressure at which a liquid becomes indistinguishable from a vapor. Superheated vapor: A vapor that is not about to condense. Saturated vapor: A vapor that will begin condensing if any heat is removed. Saturated mixture: When a saturated liquid and saturated vapor coexist in the same system. Saturated liquid: A liquid that will begin vaporizing if any heat is added. h our liquid = h f of saturated liquid our liquid’s T). Specific internal energy, specific enthalpy, specific entropy, and specific volume are not strong functions of pressure for a compressed liquid, and for moderately small pressures, these properties can be approximated as being equal to those of a saturated liquid having the same temperature, (i.e. If I instantly relocate my cup to the peak of Mount Everest where the atmospheric pressure is about one-third its sea level value, then the water will begin to spontaneously boil and change into vapor.Ĭompressed liquid: Also called “ subcooled liquid,” is a liquid that is not about to vaporize either its pressure must decrease or temperature must increase (or a combination of the two) in order to cause vaporization. If I have a cup of liquid water at sea level and its temperature is 76☌, then it’s not going to be boiling. A decrease in pressure below the vapor pressure will allow vaporization to occur. Vapor pressure: The pressure required to keep a substance a liquid when held at a certain temperature. Any addition of heat will cause further phase change and no change in temperature when pressure is constant as long as the two different phases continue to coexist. At saturation, temperature and pressure are fixed and no longer independent from each other. Saturation: When a substance is either about to undergo or is currently undergoing a phase change. Sensible Heat: The thermal energy associated with a change in temperature of a substance. Temperature does not change during a constant pressure phase change process. Latent Heat of Vaporizationis the energy required to cause vaporization (when heat is added) or condensation (when heat is extracted). Latent Heat ofįusion is the energy required to cause melting (when heat is added) or freezing (when heat is extracted). Latent Heat: The amount of thermal energy required to cause a change in phase of a substance. Lecture with animations and video ( Triple Point, Critical Point, Steam Power 1, Steam Power 2, Steam Turbines) shown via projector. Properties of Pure Substances, Phase Changes Class 5Īt the completion of the lecture, students should:ġ) Understand the concept of latent heat as it relates to a change of phase.Ģ) Understand the concept of sensible heat as it relates to a temperature change.ģ) Understand how P-v and T-v diagrams depict properties of multiphase systems.Ĥ) Understand and apply the property of Quality with regard to saturated liquid-vapor mixtures.ĥ) Analyze a multiphase closed system process. Thermodynamics Data, Equations, Charts, Equations and Calculators Related Resources: thermodynamics Properties of Pure Substances, Phase Changes Class 5
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