# Glossary of Thermodynamic Terms

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T
 Primary Word Secondary Word Definition Tutorial Page Link
 temperature A numerical scale for measuring "coldness" or "hotness".  It is determined by applying the Zeroth Law of Thermodynamics, which allows the temperature of an object to determined by calibrating it with an object of known temperature.  [C, K , F, R] 1D8 temperature absolute Absolute temperature is temperature measure in either the SI scale of Kelvin or the English scale of Rankine. Using the absolute temperature scale, the lowest theoretical temperature is 0 K and the lowest experimental temperature reached is 0.000000002 K . [K, R] 1E10 temperature critical 2B6 temperature reduced A dimensionless temperature used with the generalized compressibility charts and other EOS's. The Reduced Temperature Tr, is defined as the ratio of the absolute temperature of the system to the critical temperature of the species in the system.  As the reduce temperature approaches one, the temperature of the system approaches the critical temperature. 2E8 temperature saturation 2B2 , 5, 2C2, 3E3 temperature scale ideal gas 6F7 - 9 , 13, 6G1, temperature scale Kelvin 6F5 - 6 , 10 , 13, 6G1 , 2, temperature scale Rankine 6G1 , 2 temperature scale thermodynamic 6F2 thermal conductivity Defined by Fourier's Law.  It is the proportionality constant between the conduction heat flux and the temperature gradient.  It is a temperature dependant property of a material that indicates its ability to transfer heat by conduction.  [W/(m*K)] 4B16 , 17 thermal efficiency A measure of the performance of a power cycle or heat engine. Thermal Efficiency is the ratio of the work produced by the cycle to the heat transferred into the heat engine from the hot reservoir. 4F6, 6B4, 6C4 , 5 thermal efficiency heat engine A measure of the performance of a heat engine or power cycle. Thermal Efficiency is the ratio of the work produced by the cycle to the heat transferred into the heat engine from the hot reservoir. 6G2 - 4 thermal efficiency power cycle A measure of the performance of a power cycle or heat engine. Thermal Efficiency is the ratio of the work produced by the cycle to the heat transferred into the heat engine from the hot reservoir. 6G2 - 4 thermal equilibrium 4B9 thermal radiation 4B21 thermal reservoir An object for which the temperature never changes regardless of how much heat is transferred to or from it.  The closest approximations of true thermal reservoirs are the ocean or the Earth's atmosphere.  For modest heat transfer rates, systems in which a phase change occurs can be considered to be thermal reservoirs because their temperature remains constant as heat is added or removed. 4F4, 6B2, 6F4 thermal reservoir within a system 6C7 thermocouple 1D9 thermodynamic cycle A series of processes in which the working fluid within the system is returned to its original state when the cycle has been completed. 1D4, 4F1, 5C1 thermodynamic Properties Also known simply as properties.  Any characteristic of a system is a property of the system.  Thermodynamic properties generally relate to the pressure, volume, temperature or energy of a system. 1C4 thermodynamic temperature scale 6F2 , 6 thermodynamics The field of study that includes all aspects of energy, energy transformation, power production, refrigeration, phase and chemical equilibria and relationships among the properties of matter. 1A1 thermodynamics topics in modern study of 1A2 thermodynamics First Law of In the absence of nuclear reactions, energy cannot be created or destroyed.  Energy can only change form or be transferred.  Also known as the Conservation of Energy Principal. 1A3, 4C1 - 11, 4E1 , 3 - 5 thermodynamics Second law of 1A1 , 3, 6A1 , 7, 6B1 thermodynamics Zeroth law of If two objects are in thermal equilibrium with a third object, then they are also in thermal equilibrium with each other. 1E9 thermodynamics topics in modern study of 1A2 thermometer ideal gas 1D11 , 12 thermometer ideal gas, calibrating 1D12 thermometer liquid 1D9 throttling device 5C11 throttling valve 5C11 tie-fighter diagam 6C4 - 6, 6E19 - 23, 4F4 -12 torque A force acting on a body that is applied at a distance from the axis of rotation results in a torque on that body.  Torque is the product of the appled force and the perpendicular distance from the point at which the force is applied to the axis of rotation. t = F*r  [N*m] 4A22 total energy 4C1 , 5 , 7 toxicity 10B5 transient A process during which at least one property of the system changes as a function of time.  This type of process is also known as an unsteady processes. 5D1, 5E1, translational energy The energy associated with a molecule of gas traveling through space with a linear velocity, thus possessing kinetic energy. 2A4 trapezoidal rule 4A13 triple point The state, or point on a phase diagram, in which the three principle phases (gas, liquid, and solid) of a substance co-exist in equilibrium.  For water, the triple point occurs at 0.01 C and 0.6113 kPa. 2B7 , 8 triple point water 6F6 TS diagram 7B8  ,  9 TS diagram area under a process curve 7B12, 7C4 , 5, 7D3 TS diagram enclosed area 7B17 TS diagram heat pump 7B17 TS diagram interpreting area for open systems 8B7 TS diagram power cycle 7B17 TS diagram refrigeration 7B17 turbine A type of rotating machinery used to produce shaft work by reducing the pressure on a gas stream. 5C6 , 9, 6B5, 6E17 TV Diagram 2B4 two-phase envelope 2B5