Glossary of Thermodynamic Terms

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H
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Definition
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heat A form of energy that is transferred between two systems driven by a difference between the temperatures of the two systems. 4B1 - 5, 4C1, 5B5
heat Flux Heat transfer rate per unit area.  The appropriate area is the area for heat transfer normal or perpendicular to the direction of heat flow.  [W/m2] 4B12
heat of Fusion Also known as the Enthalpy of Fusion, Latent Heat of Fusion and Latent Enthalpy of Fusion.  Enthalpy of Fusion is the amount of energy released when a substance makes the transition from the liquid phase to the solid phase.  Values of the Enthalpy of Fusion are typically tabulated at the normal melting point (temperature).  [kJ/kmol] 3E13
heat specific
heat of Sublimation Also known as the Enthalpy of Sublimation, the Latent Heat of Sublimation and the Latent Enthalpy of Sublimation.  Enthalpy of Sublimation is the amount of energy required when a substance makes the transition directly from the solid phase to the vapor phase.  The Enthalpy of Sublimation is a function of temperature.  [kJ/kmol] 3E13
heat of Vaporization Also known as the Enthalpy of Vaporization, the Latent Heat of Vaporization and the Latent Enthalpy of Vaporization.  Represents the amount of energy required to vaporize a unit mass of saturated liquid at a given temperature or pressure. [kJ/kmol] 3E2
heat capacity Also known as the Specific Heat.  The energy required to raise the temperature of a unit mass (or mole) of a substance by one degree. 3C1, 4B1, 
heat capacity constant pressure Also known as the Constant Pressure Specific Heat.  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, 7D8 - 11, 
heat capacity constant volume Also known as the Constant Volume Specific Heat.  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, 7D8 - 11, 
heat capacity ideal gas 3C3  ,  5 - 7  ,  10 - 12, 6F8 - 9, 
heat capacity incompressible liquids 3C8
heat capacity liquid 3E7
heat capacity Shomate equation 3C12, 3D11, 3D21
heat capacity solids 3C8
heat capacity ratio The Heat Capacity ratio is the ratio of the constant pressure heat capacity to the constant volume heat capacity at a given temperature and pressure.  The heat capacity ratio is a weak function of temperature and a very weak function of pressure, so it is often treated as a constant.  Also known as the Specific Heat Ratio. 3C2, 7E5  ,  6, 
heat capacity relationship ideal gas 7D11
heat engine 4F4, 6B1, 6C4  ,  6
heat exchanger A device in which two bodies of matter, usually two moving fluids, exchange heat without physically mixing.  5C6  ,  13 - 14
heat flux 4B12 - 13
heat of vaporization 3E2 - 13
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, 10A1, 10D1
heat pump COP 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. 10D1  ,  3  ,  4
heat pump vapor-compression 10A1, 10D1 - 4, 
heat sink 6B2
heat source 6B2
heat transfer rate 4B11 - 13
hP A unit of power.  1 hP = 745.7 W = 550 ft-lbf/sec 4A6
HS diagram 7B18
HS diagram adiabatic turbine 7B18
heterogeneous mixture A mixture that does not have the same chemical composition at all positions within the system.  A heterogeneous mixture cannot be treated as a pure substance. 2A2
homogeneous mixture A mixture that has the same chemical composition at all positions within a system.  A homogeneous mixture can often be treated as a pure substance. 2A2
horse power A unit of power.  1 hP = 745.7 W = 550 ft-lbf/sec 4A6
humidity absolute In an air-water system, the ratio of the mass of water vapor to the mass of dry air. [ kg water / kg dry air ] 2D6
humidity relative A measure of how close the gas phase is to saturation.  A relative humidity of 100% means that the gas phase is saturated.  A saturated gas phase contains as much water vapor as it possibly can at that temperature.  Relative humidity is defined as the ratio of the partial pressure of water to the vapor pressure of water at the temperature of the gas phase. 2D6
hypothetical process path A process path that connects the initial state to the final state that is mad up of particularly simple steps that usually only involve a change in one property of the system, such as T, P, phase or extent of reaction.  The purpose of an HPP is to make it easier to calculate the change in the values of properties from the initial to the final state.  This is possible because changes in properties, or state variables, are independent of the process path. 3D4 - 22, 3E1  ,  4 - 9,