GC: n

CT: Thermodynamics is a branch of physics which deals with the energy and work of a system. Thermodynamics deals only with the large scale response of a system which we can observe and measure in experiments. In aerodynamics, we are most interested in thermodynamics in the study of propulsion systems and understanding high speed flows.
The state of a gas is defined by several properties including the temperature, pressure, and volume which the gas occupies. From a study of the first law of thermodynamics, we find that the internal energy of a gas is also a state variable, that is, a variable which depends only on the state of the gas and not on any process that produced that state. We are free to define additional state variables which are combinations of existing state variables. The new variables often make the analysis of a system much simpler. For a gas, a useful additional state variable is the enthalpy which is defined to be the sum of the internal energy E plus the product of the pressure p and volume V. Using the symbol H for the enthalpy: H = E + p * V
The enthalpy can be made into an intensive, or specific , variable by dividing by the mass. Propulsion engineers use the specific enthalpy in engine analysis more than the enthalpy itself.

S: http://www.grc.nasa.gov/WWW/k-12/airplane/enthalpy.html (last access: 1 February 2015)

N: 1. 1927 in physics, from Greek enthalpein “to warm in,” from en “in” + thalpein “to heat,” from thalpos “warmth, heat,” especially “summer heat.”
2. Enthalpy is the amount of heat content used or released in a system at constant pressure. Enthalpy is usually expressed as the change in enthalpy. The change in enthalpy is related to a change in internal energy (U) and a change in the volume (V), which is multiplied by the constant pressure of the system.

S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=enthalpy&searchmode=none (last access: 1 February 2015). 2. http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Enthalpy (last access: 1 February 2015).

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CR: energy, kinetic energy, potential energy.