The “Maxwell/Ranque Heater”
Toward Home Heating through the use of Maxwell’s
demon
If
you could separate the air into volumes of hot and cold air, you could then throw away the cold air, and put the heat back
in your home.
As
long as you did this more efficiently than actually heating the air,
you
would have more heat than you paid the utility company to produce!
Without
the need for speculating about wild eyed plans to use that “Free” energy to generate even more “free”
energy, and so on until you have the equivalent of Hoover Dam in my basement, wouldn’t
you still feel pretty good about the idea of maybe 1/2 off your heating bill!
It
happens to be true that there is a device which can separate both hot and cold from air at the same time, using only
compressed air. It is little more than a tube with a pipe T, a washer and a leaky plug, and it has no moving parts. And no,
it is not an alien artifact; it is a common industrial tool.
Reference: http://en.wikipedia.org/wiki/Vortex_tube
If
this new heater were made of parts which are entirely available “off the shelf”;
involving
no new technology, only the proper arrangement of existing technology that would be even better. This also happens to be true.
Now
some readers will already be preparing the branch to hang me from, believing that I have provided enough rope to hang myself.
That is, after I fall off the laws of thermodynamics provided conveniently by James Clerk Maxwell.
However
we are going to enslave Maxwell's own Demon to help
heat our hypothetical home. And you will have to argue with James Clerk Maxwell who’s equations lay the foundation for special relativity and quantum mechanics.
Reference: http://en.wikipedia.org/wiki/Maxwell%27s_Demon
During
Maxwell’s Lectures he speculated that if we had a tiny demon which could open and close a tiny valve in the wall of
a box, we could separate the hotter and colder molecules of air by opening the valve only when a molecule of the right speed
came along. This is because statistically the molecules are of varying temperatures. In this way we could change the temperature
in the box.
We
will use the vortex tube to take on the role of Maxwell’s Demon. The vortex tube is well known to the theoretical
and industrial sides of engineering, with a number of well defined operational parameters.
The vortex tube has no moving parts, you blow air into the stem of a T shaped pipe of the appropriate internal design,
and hot air comes out one end of the top of the T and cold out the other.
Reference: http://www.vortexair.biz/Cooling/SPOTCOOLPROD/Vortex_Technical/vortex_technical.html
|
PSI |
Cold Fraction % |
|
20 |
30 |
40 |
50 |
60 |
70 |
80 |
|
20 |
61.5 |
59.5 |
55.5 |
50.5 |
43.5 |
36.0 |
27.5 |
|
14.5 |
24.5 |
36.0 |
49.5 |
64.0 |
82.5 |
107 |
|
40 |
88.0 |
85.0 |
80.0 |
73.0 |
62.5 |
51.5 |
38.0 |
|
20.5 |
35.0 |
51.5 |
71.0 |
91.5 |
117.0 |
147 |
|
60 |
104 |
100 |
93.0 |
84.0 |
73.0 |
59.5 |
44.5 |
|
23.5 |
40.0 |
58.5 |
80.0 |
104 |
132 |
168 |
|
80 |
115 |
110 |
102 |
92.0 |
80.0 |
65.5 |
49.0 |
|
25.0 |
43.0 |
63.0 |
86.0 |
113 |
143 |
181 |
|
100 |
123 |
118 |
110 |
99.0 |
86.0 |
70.5 |
53.0 |
|
26.0 |
45.0 |
66.5 |
91.0 |
119 |
151 |
192 |
|
120 |
129 |
124 |
116 |
104 |
90.5 |
74.0 |
55.0 |
|
26.0 |
46.0 |
69.0 |
94.0 |
123 |
156 |
195 |
|
140 |
135 |
129 |
121 |
109 |
94.0 |
76.0 |
56.5 |
|
25.5 |
46.0 |
70.5 |
96.0 |
124 |
156 |
193 |
|
Figures shaded in grey give temperature drop of
cold air, degrees F |
|
Figures on the second line give temperature rise
of hot air, degrees F |
Examination
of this chart shows that for heat or cold extracted vs. power input required to achieve the higher compression values, the
efficiency actually goes down with higher air pressures input, because it requires more energy to increase compression.
Each
time the chart increases compression, less differential is gained between the value of the hot and cold outputs.
While
the chart does not specify values for Power input to achieve compression, we know from experience that it becomes more and
more difficult to press the bicycle pump down as the back pressure increases.
Referencing
the chart for a cold fraction of 60 %:
The
difference between the hot output between 120 PSI input and 140 PSI input is only + 1 degree hotter for the 20 additional
PSI.
In other
words:
The
increase from 120 to 140 PSI has an input benefit of + 1 degree
The
increase from 0 to 20 PSI has an input benefit of + 64 degrees
Clearly
the lower pressure is more efficient.
It
is a fact that there is progressively less benefit at higher pressures. And the decrease in efficiency is not linear.
This
holds true from 120 PSI down to 20 PSI for a fact, and I expect it is true below 20 PSI.
The output is dependant upon the input temperature, and the difference between the input pressure and Cold Fraction
output pressure.
I
estimate based on a visual analysis of the trend in the bar chart (In the upper right corner) that the effect continues at
increasingly lower differential values until the vortex ceases to form from lack of pressure.
Since
vortex fans are able to create a vortex effect, I believe this leaves us with the option of going to fractional PSI increase
values if we determine the temperature differential is sufficient for a desired number of vortex tube stages.
However
based on some projections and calculations, I believe the lowest practical pressure would be about 5 PSI.
There
are many other wonderful facts posted on the site referenced above.
I
highly recommend it. Making my first tube from brass fittings cost me around $ 40
Since
the tubes sell for around $ 100 dollars, the assurance of a successful reference tube is well worth the investment for the
experimenter.
There
are a number of other manufacturers available, but this one has the best documentation in my opinion. I have no personal connection with them, and have not yet purchased a reference tube yet.
With
lowering input pressure, the extremes of the hot and cold outputs are not as high and low, and the volume of air decreases;
but not as rapidly as the power needed to compress the air.
Efficiency
in this case being how much electric power it costs to raise the output temperature of a volume of air N degrees.
For
instance a fan has very low power consumption compared to high pressure compressor.
If we could heat the house using only a few fans, moving greater volumes at lower expense, this would consume much
less electricity than a high pressure, high volume compressor.
We
will ignore for the moment that with lower pressure we have lower air flow. This can be compensated for by using a wider vortex
tube. The industrial vendor in the link supplies several sizes. So we can surmise that they can be scaled up for lower pressure,
higher volume architectures. In fact references show the tubes being used in refinery processes and Natural Gas pipelines.
These are of considerable dimension.
For
our current purposes we are interested in low pressure, and heating.
The
Thermal Engineering community which knows the vortex tube extremely well appears
to be not particularly interested in either heating or low pressure operation with the vortex tube. 20 PSI seems to be as low as they care to explore. I find primarily references to cooling and high pressure
characteristics explored on the web and indexed in the “literature”. The heat is rarely used for any purpose other
than de-icing the cold side.
Also
consider that industrial cooling often demands extremely low temperature outputs, requiring extremely high differentials,
and extremely high input pressures.
But
we are not about cooling here.
The
value for minimum pressure which provides the maximum efficiency is probably
undefined by the Thermal Engineering community at large unless is not currently “public” knowledge. I have not been able to find it, if it does exist.
Why?
When
operating within the laws of thermodynamics, ignorance is no excuse!
Because
of the high industrial pressures used to generate extreme temperatures, Vortex Tubes are considered horrendously inefficient!
Fortunately
it will not be hard to determine if vortex tubes can be arranged to efficient low pressure home heating configurations.
With an input temperature of 70 degrees as shown in the above table, Maxwell’s demon allows me to run the compressed
air through a vortex tube at 20 PSI and 60 percent of the air goes out the Cold Fraction side. I gain 64 degrees from the
input temperature on the remaining 40 percent of input going out the Hot Fraction side.
For the purpose of demonstrating the theory, I can simply discard 60 percent of the
air at 43.5 degrees colder than the 70 degree input as exhaust.
NOTE:
I am arbitrarily throwing away a 43.5 degree temperature drop and still demonstrating
a free additional temperature increase in the house. For home heating purposes the Cold Fraction is really a liability. This
could be used toward refrigeration as a side benefit and that use might even make our task easier and more energy
efficient on the whole.
OC
Do
you now believe that I have demonstrated that you do get Over-Unity or COP > 1 from a Vortex or Ranque Tube? Those are
both ways of saying more energy out than put in.
The
truth is that there is no more energy in the room than when we started.
When
I dispose of the cold output, I need to replace that air with an equivalent volume
of more highly heated air, fortunately the demon stole some heat from the air which I am throwing away. I can use that to
heat the fresh air, just as long as I find a place warmer than my coldest temperature air to dispose of it.
I
personally do not believe I am describing Over-Unity or COP > 1, because there was no expansion of the original air volume,
“Normal
Heating” causes expansion.
If
this is either Over-Unity or COP > 1 then the distinction is only semantic anyway.
We
transferred existing heat energy incidentally, and took advantage of this to get a statistically higher average temperature
of the remaining air. No new energy was introduced into the universe during this experiment! No laws of Thermodynamics or
Engineering scholars were violated.
Don't celebrate yet!
The
real engineering problem comes after you gain the "Free Energy"?
To
use this for home heating, you need to discharge the cold from the cold air output, outside the home. This is because you
are simply separating the hotter and colder molecules of air.
“Simple
separation” is a convenient over-simplification. Heat exchange within the vortex is vital to vortex tube operation.
The heat exchange allows the tube to be more efficient at higher input air temperatures, and makes sequential
configuration of multiple tubes possible.
Once
again analysis of the chart reveals a pertinent fact. Approximately 60% of the air needs to be cold output for optimal efficiency
in heating.
By
discharging the air, you would be creating a vacuum in the house, sucking in exterior cold air to replace the separated cold
fraction air.
WARNINING
TO EXPERIMENTERS: I also fear incidentally separating the oxygen and discharging that
outside, oxygen separation with vortex tubes has been done by NASA. Removing
the oxygen from your home can severely impact your respiratory health. You would not see, or smell the difference, but you
might sense something is wrong as you pass into coma and death.
See
NASA [PDF]
To
overcome the discharge problem I have two ideas:
The
first is to use a heat exchange system to a ground water source to "sink" some of the cold and recirculate the air back in
at ground water temperature. In this way we gain the benefit of the difference between the colder output and the ground water
temperature, The difference between the ground water temperature and the inside temperature becomes lost efficiency, as we
now need to heat that to a comfortable inside temperature, however it is always necessary to introduce fresh air and heat
that fresh air continually, so this helps to mitigate the inefficiency.
This
approach in its pure form is operationally limited by the differential with the outside temperature. Once the outside medium becomes as cold as the Cold Fraction, there is no way to dump the cold. (That is why I prefer ground water to air as a sink, air can get much colder than ground water naturally
gets.)
The
second idea is to use a multistage approach and cycle the hot or cold output through the input of another vortex tube. (See
the referenced page above)
Cycling
the hot output looks less promising on paper Cycling the cold output provides the ability to preprocess the majority of air
at a low differential with a 20% CF and then reduce the 20% to as low as 4 % extremely cold output.
Efficiency
increases with higher input temperatures and multistage vortex tubes have been successfully tested (But not to my knowledge,
both together.).
In
this way it might be possible to gain a higher differential and exchange a smaller total fraction
of extremely cold output for relative outside warmth.
It
is also theoretically possible to freeze a large area of ground mass below the frost line. Though I do not have any idea on
how that would be implemented in a practical way. But the possible seasonal cooling benefits might make it worth thought.
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