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UNIVERSITY OF BUCHAREST FACULTY OF PHYSICS Guest 2024-11-24 11:23 |
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Conference: Bucharest University Faculty of Physics 2005 Meeting
Section: Atomic and Molecular Physics; Astrophysics
Title: High efficiency thermal engine
Authors: Mugurel Balan
Affiliation: University of Bucharest, Faculty of Physics
E-mail mugurel.balan@rosa.ro
Keywords:
Abstract: The purpose of this experiment is to design and construct a thermal engine that will transform solar heat in electrical power with very high efficiency, based on the fact that there is a temperature difference between the dark and the lighted side of the satellite. Conceptually, the engine consists of two bottles linked by a capillary net and by an empty tube with a turbine inside. The first one is heated directly by the sun while the second one is protected from the sun heat by a reflecting panel.
In imponderability the strongest force between a liquid and a surface is the adhesion force. Because of this force, a drop of liquid put on a surface will run out to cover the entire surface. So, putting a small quantity from the liquid inside the first bottle, without a gravitational field, the liquid will cover its entire internal surface.
Because this bottle is heated by the sun, the liquid from the inside will evaporate and after some time the whole liquid will be transformed into gas. Because of this phase transition the pressure will grow up. The problem is how to transform the internal energy of the gas into electrical power. The easiest way to do that is to allow the gas to pass through the tube into the second bottle. So, using the movement of the gas, the turbine from inside the tube will generate electrical power.
It is known from the black body theory that after some time the bottles will reach thermal equilibrium with the ambiance losing or gaining heat. At thermal equilibrium, the first one will reach 500 K and the second one 100 K.
A fraction f from the gas mass has passed now into the second bottle at a temperature T2, smaller than the temperature T1 (of the first bottle). T2 is bigger than the temperature of the bottle’s body, which is in thermal equilibrium with the ambiance (100 K). After some time, the part of the gas that passed into the second bottle will reach thermal equilibrium with the body of the bottle. If the temperature is small enough, the whole gas that reached the second bottle will became liquefied.
If the gas becomes liquid, the easiest way for it to be returned in the first bottle is to use a capillary net. This method is efficient even if this bottle is at higher pressure. In order to prove that the engine works, it was built and tested in a laboratory. In a gravitational field, the surface force is smaller. It can still be observed in a capillary net, for example a piece of chalk. Using water as a liquid and chalk as capillary net, the engine was tested and it worked. Because of the small temperature difference (100 K), its efficiency was not very high. If the engine would be built for space, where the temperature difference is bigger than 400 K, liquid Cl2 and ceramic would be used as liquid and capillary net. In this condition, from the calculations, the efficiency would reach 75%. In order to measure his efficiency the engine must be placed out side ISS as a satellite. However, this is only a concept and it is strongly recommended to test it in space.
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