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5.6.1 Definitions

• Temperature: Absolute temperature () in Kelvin (K). In terms of thermodynamic properties, it is the driving potential for energy transfer as heat.

• Conductivity: Thermal transport property of fluid or solid, relating the heat flux (W/m²) to the temperature gradient according to Fourier's Law . The unit for conductivity () is W/m-K.

• Static Enthalpy: It is a measure of the energy (J/kg) of a thermodynamic system as defined below:

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  where

  	Static enthalpy (J/kg)
  	Specific internal energy (J/kg)
  	Pressure (Pa)
  	Density (kg/m3)

• Total Enthalpy: Total enthalpy, also known as the stagnation enthalpy is expressed in terms of static enthalpy, and flow kinetic energy as follows:

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  where

  	Total enthalpy (J/kg)
  	Static enthalpy (J/kg)
  	Velocity (m/s)

• Capacity: Refers to specific heat capacity of fluid or solid, relating the change of enthalpy () with temperature (). The unit for capacity is J/(kg-K). For fluids, specific heat at constant pressure is given as:

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• Total Flux: Total Wattage (W) of heat crossing a selected boundary or interface.

• Flux per Area: The average Wattage per area (W/m²) of heat crossing a selected boundary or interface.

• Prandtl Number: The ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity, .

• Internal Energy: Internal Energy () is the thermodynamic specific internal energy of the fluid or solid. The unit for specific internal energy is J/kg.

• Mass Avg Internal Energy: The average internal energy in a selected volume based on a mass weighted average (as opposed to a volume weighted average).

• Mass Avg Tot Internal Energy: The average total internal energy in a selected volume based on a mass weighted average (as opposed to a volume weighted average).

• Tot Internal Energy: The specific internal energy at stagnation (J/kg) of the fluid or solid.

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  where

  	Total internal energy (J/kg)
  	Specific internal energy (J/kg)
  	Velocity (m/s)

• Mass Avg Enthalpy: The average enthalpy in a selected volume/area based on mass weighted average (as opposed to a volume weighted average).

• Mass Avg Tot Enthalpy: The average total enthalpy in a selected volume/area based on mass weighted average (as opposed to a volume weighted average).

• Total Temperature: Total temperature, also known as the stagnation temperature is related to the static temperature as follows:

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  where

  	Total temperature (K)
  	Static temperature (K)
  	Specific heat at constant pressure (J/(kg-K))
  	Velocity (m/s)