# Glossary of Thermodynamic Terms

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S
 Primary Word Secondary Word Definition Tutorial Page Link
 saturated liquid A liquid that exists at the saturation temperature or boiling point (T = Tsat = Tbp) that corresponds to the existing pressure. If any energy is added to the liquid and the pressure is kept constant, some of the liquid would boil. During the boiling process the temperature will remain constant. 2B2  ,  4  ,  5  ,  6  ,  8, 2C1  ,  2, 3E1 - 2  ,  5  ,  6  ,  10 saturated liquid specific entropy 7B10 saturated liquid curve A curve on a phase diagram that is the collection of points or states at which all of the mass of the system exists in a saturated liquid phase.  Each point on the curve corresponds to a pressure equal to the vapor pressure, P*, a temperature equal to the saturation temperature, Tsat, and a quality of 1. 2B3 saturated mixture A mixture of saturated liquid and saturated vapor in equilibrium. The temperature is Tsat and the pressure is the vapor pressure is P*. 2B2 saturated vapor A vapor that exists at the saturation temperature (T = Tsat) that corresponds to the existing pressure. If any energy was removed from the vapor while the pressure is kept constant, some of the vapor would condense.  During the process of condensation the temperature would remain constant. 2B2  ,  4  ,  5  ,  6  ,  8, 2C1  ,  2, 3E1 - 2  ,  5  ,  10 saturated vapor curve A curve on a phase diagram that is the collection of points or states at which all of the mass of the system exists in a saturated vapor phase.  Each point on the curve corresponds to a pressure equal to the vapor pressure, P*, a temperature equal to the saturation temperature, Tsat, and a quality of 1. 2B3 saturation A state in which a given phase contains the highest concentration of a certain substance that it can hold. 2B2 saturation absolute In a gas-vapor system, the ratio of the mass of vapor to the mass of vapor-free, non-condensable gas. [ kg vapor / kg dry gas ] 2D6 saturation relative A measure of how close the gas phase is to saturation with the condensable species.  A Relative Saturation of 100% means that the gas phase is saturated.  A saturated gas phase contains as much of the condensable species as it possibly can at that temperature.  Relative Saturation of a gas phase is defined as the ratio of the partial pressure of the condensable species to the vapor pressure of the condensable species at the temperature of the gas phase. 2D6 saturation pressure tables 2C1  ,  2  ,  5 saturation temperature 2B2 , 5, 2C2, 3E3 saturation temperature tables 2C1 , 2 , 3 , 4 second law efficiency 8D6 second law of thermodynamics 1A1 , 3, 6A1 , 7, 6B1 second law of thermodynamics Clausius statement 6C3 , 5, 6D1, second law of thermodynamics Kelvin-Planck statement 6C8, 6D1, 6E21 , 22 sensible heat When heat is transferred into or out of a system and it produces a change in the temperature of the system is called sensible heat.  This is in direct contrast to a latent heat. 4B2  ,  3 shaft work 4A20 - 23, 4C5, 5C3 shaft work polytropic process 8B12 - 20 shaft work polytropic process, exponent = 1 8B16 shaft work polytropic process, ideal gas 8B14 shaft work polytropic process, ideal gas, constant heat capacities 8B15 shaft work polytropic process, ideal gas, isothermal process 8B17 shaft work polytropic process, isochoric 8B18 Shomate equation 3C12, 3D11 , 21, SI 1B4 - 6, 1D10, sign convention heat 4B6 - 7 , 13, 5B5, sign convention work 4A3 - 4 , 10, 5B5, SISO 5C4 , 6, 5E1, SISO mass balance 5D3 , 4 Soave-Redlich-Kwong EOS A cubic, empirical EOS that accurately represents the behavior of a wide variety of systems, especially hydrocarbons.  Its three parameters are empirical functions of the critical temperature and pressure and the Pitzer Accentric Factor. 2F1 , 8 solid A phase in which molecules are separated from each other by a distance of not more than a few molecular diameters (a condensed phase)   Molecules in a solid phase have less translational, vibrational, and rotational energies than the same type of molecules in either a pure liquid phase or  a pure gas phase at the same temperature and thus have a lower internal energy. 2A4 solids heat capacity 3D14 - 17 solids property change 3D14 - 17 specific energy 5B4 specific heat Also known as the Heat Capacity.  The energy required to raise the temperature of a unit mass (or mole) of a substance by one degree. 3C1 specific heat constant pressure Also known as the Constant Pressure Heat Capacity.  The amount energy required to raise the temperature of a unit mass (or mole) of a substance by one degree at a constant pressure. The symbol for the constant pressure heat capacity is Cp and only the units can tell you whether the value refers to a molar basis or a mass basis.  [ kJ / kg-K, J / mole-C, Btu / lbm-F, etc. ] 3C2 specific heat constant volume Also known as the Constant Volume Heat Capacity.  The amount energy required to raise the temperature of a unit mass (or mole) of a substance by one degree while the volume of the system remains constant. The symbol for the constant pressure heat capacity is Cv and only the units can tell you whether the value refers to a molar basis or a mass basis.  [ kJ / kg-K, J / mole-C, Btu / lbm-F, etc. ] 3C2 specific heat ratio Also known as the Heat Capacity Ratio.  The Specific Heat ratio is the ratio of the constant pressure Specific Heat to the constant volume Specific Heat at a given temperature and pressure.  The Specific Heat ratio is a weak function of temperature and a very weak function of pressure, so it is often treated as a constant. 3C2 specific volume 2B1, 2C2 , 14, spontaneity 6A4 - 6, 6B1, 6C38719 spring constant The proportionality constant between the force exerted on a spring and its length or displacement. 4A27 spring work 4A20 , 27 , 28 state The condition of a system.  ALL of the properties of a system have fixed or specified values at a given state.  If the value of any property of the system changes, then the system is in a different state. 1C6, 1D2 - 4, 3D1 state variable Variables that are dependent only on the state of the system and not the path by which the state was reached. 3D4, 4A12, 4C5 , 6 steady-state A type of process in which properties may vary with posistion within the system, but none of the properties of the system change with time. 5C1  ,  2 Stefan-Boltzmann Constant 4B21 Stefan-Boltzmann Law An equation that permits you to calculate the radiation heat transfer rate between two objects  based on the temperature and surface properties of the emitter and the absorber. 4B21 STP Standard Temperature and Pressure. The standard temperature and pressure are 1 atm and 25 C. 2E3 stream mixer 5C6 , 16 subcooled liquid Also known as a compressed liquid.  A liquid that is at a temperature BELOW the saturation temperature (T < Tsat) that corresponds to the existing pressure. The addition of a small amount of energy will NOT cause the vapor to vaporize, its temperature will just increase. 2B4 , 5 , 8, 2C13 - 16, 3E6 subcooled liquid enthalpy 3B12 - 16 subcooled liquid internal energy 3B12 - 16 subcooled liquid specific entropy 7B10 subcooled liquid tables 2C1 , 13 - 16 sublimation A process in which molecules in a solid phase make the transition directly into the gas phase.  For a system containing a pure substance, sublimation can only occur at pressures and temperatures below the triple point. 2B7 , 8 sublimation latent heat of 3E13 sublimation curve 2B8 supercritical fluid A substance existing at a temperature above the critical temperature, Tc, and above the critical pressure, Pc. 2B6 , 8 superheated vapor A vapor existing at a temperature ABOVE the saturation temperature that corresponds to the existing pressure (T > Tsat).  The removal of a small amount of energy will NOT cause the vapor to condense, its temperature will just decrease. 2B2 , 4 , 5, 2C18 , 19, superheated vapor tables 2C1 surroundings All of the mass and volume of the universe that is NOT inside the boundary of the system. 1C2, 4A2 - 4, system The quantity of mass or volume that has been chosen for analysis.  The system boundary separates the system from the surroundings. 1C2 , 3, 4A2 - 4 , 9 , 13, system closed No mass crosses the boundary of a Closed System during a process. 1C2 , 3 system open A system in which mass crosses the boundary during a process. 1C3, 5A1  ,  2, system boundary 1C2, 4A2 - 6,