As the gas cools, energy is delivered as propulsion (see the sections “Temperature” and “Euler’s equation”). We estimate the propulsion energy in 2 situations: (1) duct, moving in a straight line; (2) rotating duct. In both of them, the propulsion energy turns out to be the same. It is given by the resttorest energy formula
This formula shows that a gaseous mass m, initially at rest in one frame of reference, makes the transition, at the expense of its own stagnation enthalpy, to a state of rest in another frame of reference, where the 2 reference frames move with respect to each other with constant linear velocity c. Thus, the above formula stems from the physics of a system with variable mass. If we perform temperature analysis, the exact same formula comes out as the result. One can call this formula an “apparent massenergy equivalence”, since to an observer in the starting frame where m is initially at rest, it seems that the removal of this mass leads to the liberation of energy. In fact, the mass only transitions between 2 frames of reference and is not equivalent to energy. It releases some of its pressure and thermal energy in the transition.
The information contained in this site is based on the following research articles written by Jeliazko G Polihronov and collaborators:
 “Thermodynamics of Angular Propulsion”
 “Vortex Tube Effect Without Walls”
 “Angular Propulsion  The Rotational Analog of Rocket Motion”
 “On the Thermodynamics of Angular Propulsion",
 Proceedings of the 10th International Conference on HEFAT, 1416 July 2014, Orlando (2014).
