Gerhard
2020-03-06 22:26:26 UTC
A magnetic fluid (ferrofluid) is a liquid that becomes strongly attracted by a magnet. Suppose we have a system with such magnetic fluid and a strong magnet on the left side. The magnetic fluid will be attracted by the magnet and build up a "pillar" on the left side at the magnet. So the density in the fluid pillar on the left side is much higher than the density (just air) on the right side of the system.
However, what happens if the system has also a paddle wheel, which partly extends into this "magnetic fluid pillar" at the left side?
M+-----------------------+
A|* * * |
G| * * | |
N|* * *\ | / |
E| * * \ | / |
T|* * * \ | / |
M| ----------o---------- |
A|* * * / | \ |
G| * * / | \ |
N|* * */ | \ |
E| * * | |
T|* * * |
+-----------------------+
On the left side: The fluid produces a buoyancy on the paddle because of the high density of the fluid - which acts opposite to the gravity force. On the right side, the wheel will pushed down by the normal gravity force - the wheel begins to spin.
When one part of the wheel on the left side spins upwards out of the magnetic fluid, another part begins to go inside the fluid in the left lower side. So the wheel will spin continuously.
When the magnetic fluid pillar pushes the wheel up the fluid acts against the gravity and so cool down. So heat energy (without a heat difference) will be transformed in rotational energy - which can be used in many ways. At last the rotational energy will somehow be transformed back to heat energy which heat another part of the system.
This idea does not violate the second law of thermodynamics, which states that the total entropy can never decrease. In fact, building up a certain temperature difference will increase the entropy in this system.
However, this system violates the Clausius statement of the second law, an empirically validated postulate of thermodynamics, which states that "Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time."
Remarks
The idea is that there is some density difference normal to the gravity vector (or at least not in parallel). This can be done by a fluid or a gas which is attracted by an arbitrary force. A paddle wheel, which is not attracted by this force "sees" just this change of the density and therefore is affected by this density change – it is influenced by this buoyant force only in this delimited part of the system. Moreover this works not only for a paddle wheel, but for many structures like a propeller or an Archimedean screw. Just one part of the structure, which can be moved or twist must be inside the part with the high density and the other outside.
However, what happens if the system has also a paddle wheel, which partly extends into this "magnetic fluid pillar" at the left side?
M+-----------------------+
A|* * * |
G| * * | |
N|* * *\ | / |
E| * * \ | / |
T|* * * \ | / |
M| ----------o---------- |
A|* * * / | \ |
G| * * / | \ |
N|* * */ | \ |
E| * * | |
T|* * * |
+-----------------------+
On the left side: The fluid produces a buoyancy on the paddle because of the high density of the fluid - which acts opposite to the gravity force. On the right side, the wheel will pushed down by the normal gravity force - the wheel begins to spin.
When one part of the wheel on the left side spins upwards out of the magnetic fluid, another part begins to go inside the fluid in the left lower side. So the wheel will spin continuously.
When the magnetic fluid pillar pushes the wheel up the fluid acts against the gravity and so cool down. So heat energy (without a heat difference) will be transformed in rotational energy - which can be used in many ways. At last the rotational energy will somehow be transformed back to heat energy which heat another part of the system.
This idea does not violate the second law of thermodynamics, which states that the total entropy can never decrease. In fact, building up a certain temperature difference will increase the entropy in this system.
However, this system violates the Clausius statement of the second law, an empirically validated postulate of thermodynamics, which states that "Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time."
Remarks
The idea is that there is some density difference normal to the gravity vector (or at least not in parallel). This can be done by a fluid or a gas which is attracted by an arbitrary force. A paddle wheel, which is not attracted by this force "sees" just this change of the density and therefore is affected by this density change – it is influenced by this buoyant force only in this delimited part of the system. Moreover this works not only for a paddle wheel, but for many structures like a propeller or an Archimedean screw. Just one part of the structure, which can be moved or twist must be inside the part with the high density and the other outside.