# Glossary of Thermodynamic Terms

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C
 Primary Word Secondary Word Definition Tutorial Page Link
 Carnot 1A1 Carnot heat engine 6E1  ,  13 - 18  ,  20 - 22 Carnot heat pump 6E1  ,  14  ,  19  ,  21 Carnot power cycle 6E1  ,  13 - 18  ,  20 - 22 Carnot refrigeration 6E1  ,  14  ,  19  ,  21 Carnot cycle 6E1  ,  3 - 22 Carnot cycle closed system 6E1 - 14 Carnot cycle First law analysis 7B17 Carnot cycle gas power 9E1 Carnot cycle open system 6E15 - 16 Carnot cycle PV diagram 7B14 Carnot cycle refrigeration 10A2 - 5 Carnot cycle Second Law analysis of 7B16 Carnot cycle TS diagram 7B15 Carnot cycle vapor power cycle 6E17  ,  18 Carnot efficiency 6G1 Carnot Principle First 6E20  ,  21 Carnot Principle Second 6E20 - 22 Carnot refrigeration cycle gas 10A2 - 5 Carnot refrigeration cycle vapor-compression 10A2 - 5 Carnot vapor power cycle TS diagram 9B1 chemical stability 10B5 Clapeyron equation 3E10  ,  11 Clausius inequality 7A1 - 10 Clausius-Clapeyron equation An equation that relates the vapor pressure of a given substance to the temperature and the heat of vaporization of the substance at the same temperature. Given the vapor pressure and the heat of vaporization at one temperature, the Clausius-Clapeyron Equation provides a way to estimate the vapor pressure at other, similar temperatures.  This is accurate as long as the heat of vaporization remains essentially constant over the range of temperatures under consideration. 3E11 closed system No mass crosses the boundary of a Closed System during a process. 4C3 - 6 coefficient of performance heat pump A measure of the performance of a heat pump system.  The COP is the desired energy transfer rate divided by the required energy transfer rate.  For a heat pump cycle, COP is the heat transfer rate into the hot reservoir divided by the rate at which work is supplied to the cycle. COP is generally greater than 1. 6B8 coefficient of performance refrigeration A measure of the performance of a refrigeration system.  The COP is the desired energy transfer rate divided by the required energy transfer rate.  For a refrigeration cycle COP is the heat transfer rate from the cold reservoir divided by the rate at which work is supplied to the cycle. COP is generally greater than 1. 4F9 coefficient of performance A measure of the performance of a refrigeration or heat pump system.  In each case, COP is the desired energy transfer rate divided by the required energy transfer rate.  For a refrigeration cycle COP is the heat transfer rate from the cold reservoir divided by the rate at which work is supplied to the cycle. For a heat pump cycle COP is the heat transfer rate into the hot reservoir divided by the rate at which work is supplied to the cycle.  COP is generally greater than 1. 4F9 cold air-standard assumption 9E11 compound Chemical species comprised of more than one element 2A1 compressed liquid Also known as a subcooled 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 compressed liquid specific entropy 7B10 compressibility chart Also known as the Generalized Compressibility Charts.  A plot of the compressibility factor, Z, as a function of the reduced pressure, Pr.  The three different compressibility charts cover the low, intermediate and high ranges of Pr.  The charts include curves of constant reduced temperature, Tr and curves of constant ideal reduced molar volume, Vr 2E10 compressibility factor Also known as the Generalized Compressibility Factor.  The symbol for the Compressibility Factor is Z.  It is equal to the ratio of the actual molar volume to the molar volume predicted by the Ideal Gas EOS.  The defining equation is :  Z = PV/nRT.  Therefore, Z = 1 for ideal gas and the deviation of Z from 1 is a measure of the non-ideal behavior of a gas at a given t and P. 2E7 compression 4A1  ,  11 compression adiabatic 6E9  ,  10 compression isothermal 6E8  ,  10 compression multi-stage with intercooling 8C13 - 18 compression multi-stage with intercooling, ideal gas, constat heat capacities 8C17  ,  18 compression reversible 6E2 compressor A device that uses an external source of work, such as a motor, to increase the pressure of a gas. 5C6  ,  9 condensable 2D3  ,  4  ,  5 condensation A process in which molecules make the transition from the gas or vapor phase into the liquid phase. 2B7 condense 2D1 condenser 6B5  ,  7  ,  9 conduction A heat transfer mechanism that occurs when more energetic atoms, molecules or electrons interact or collide with less energetic molecules.  Conduction is the principle mode of heat transfer in solids and is also important for heat transfer in fluids. 4B14 - 17 conservation of energy principle In the absence of nuclear reactions, energy cannot be created or destroyed.  Energy can only change form or be transferred.  Also known as the First Law of Thermodynamics. 1A3 conservation of mass In the absence of nuclear reactions, mass cannot be created or destroyed. 5A1 conservation of mass closed system 8B3 conservation of mass open system 8B3 conservation of mass steady-state 8B5 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  ,  6 - 8 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  ,  5 - 8 convection A mode of heat transfer usually between a solid surface at one temperature and an adjacent moving fluid at another temperature.  Convection heat transfer is the combination of conduction heat transfer with the effects of fluid motion at an interface. 4B14  ,  18 - 20 convection forced Heat transfer in which the motion of the fluid phase is driven by a pressure difference within the fluid.  This pressure difference is generally applied by a fan or pump of some sort. 4B18  ,  20 convection free Heat transfer in which the motion of the fluid phase is caused by buoyant forces.  The buoyant forces are the result of unbalanced density differences in an external acceleration field, usually gravity.  Also known as natural convection. 4B18  ,  20 convection heat transfer coefficient An empirical parameter defined in Newton's Law of Cooling.  It is the proportionality constant between the convection heat flux and the difference in temperature between the bulk fluid and the solid surface.  The value of the convection heat transfer coefficient depends on fluid properties, the fluid velocity profile near the interface and the geometry  of the fluid-solid interface. The symbol for the convection heat transfer coefficient is "h".  [W/(m^2*K)] 4B19  ,  20 convection natural Heat transfer in which the motion of the fluid phase is caused by buoyant forces.  The buoyant forces are the result of unbalanced density differences in an external acceleration field, usually gravity.  Also known as free convection. 4B18  ,  20 corresponding states principle of For all gases at the same reduced temperature and reduced pressure, many physical properties, including the compressibility factor, Z, are the same. 2E7 corrosiveness 10B5 critical molar volume The molar volume at of a pure substance when it exists at the critical temperature and pressure of that substance.  [ L/mol ] 2B7 critical point State (T and P) at which the saturated liquid and saturated vapor states are identical.  This means that the saturated vapor and liquid have all the same properties and, as a result, become indistinguishable. 2B3  ,  5  ,  7  ,  8 critical pressure The pressure at the critical point.  This is the highest pressure at which a species can coexist in the vapor and liquid phases.  [ atm, Pa, bar, Torr ] 2E8 critical temperature The temperature at the critical point.  The highest temperature at which a species can coexist in the liquid and vapor phases.  [ K, C, R, F ] 2B6 cross-sectional area 5A5 cryogenic temperatures 10E1 cycle A cycle, or thermodynamic cycle, is 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 cycle Carnot 6E1  ,  3 - 22 cycle closed 4F1 cycle gas 4F1 cycle gas power 9E1 - 13 cycle heat pump A cycle in which work is done on a system in order to transfer energy, in the form of heat, into a high temperature reservoir from a cold reservoir. 4F1  ,  3  ,  10 - 11 cycle irreversible 7A3  ,  6 cycle open 4F1 cycle power A cycle in which energy, in the form of heat, is transferred from a hot reservoir into a system in order to do work on the surroundings. 4F1  ,  3 - 6 cycle refrigeration A cycle in which work is done on a system in order to remove energy, in the form of heat, from a cold reservoir and reject waste heat into a high temperature reservoir. 4F1  ,  3  ,  7 - 9 cycle reversible 7A3  ,  5 - 9 cycle thermodynamic definition 4F1 cycle vapor 4F1 cycle vapor power 9B1 cyclic integral 7A2  ,  7 - 8 