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Cavitation
Name: Bill
Status: other
Age: 20s
Location: N/A
Country: N/A
Date: 2000-2001
Question:
I would like to learn about cavitation. It is my
understanding that in a cavitation event, as the bubble colapses the
pressure in the bubble approaches infinity as the bubble's size
approaches zero. And that as the pressure increases so does the
temperature. So at the molecular level as the bubble size approaches the
size of one water molecule the temperature at that point could be hotter
than the sun. My first question would be, is my first assumpion correct?
My second question is, if indeed a cavitation event causes tremendous
temperatures, is that enough to break molecular bonds, or even atomic
bonds? If the answer to my second question is affermative then it is
possible to generate more energy out of a cavatation event than went into
making it?
Replies:
Yes, cavitation can generate tremendous temperatures inside the collapsing
bubble, even greater than at the surface of the sun. This is easily enough
to break covalent (molecular) bonds. Hovever, it does not approach the
temperatures necessary to induce nuclear reactions. The only reason that a
self-sustaining thermonuclear reaction can occur on the sun is that there is
so much fuel present. At the temperature of the sun, very, very little of
the material reacts at any given time. That is why the sun can sustain its
energy output for so many billions of years.
In other words, ultrasonic cavitation will not generate more energy than it
consumes by inducing nuclear reactions.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
An interesting experiment, but it is unlikely that are getting more
energy out
than you put in. And, as you've indicated, 20% is a lower limit on your
estimate. Two areas to double check are:
1. The accuracy of the instruments you are using to measure the power
you are
putting into the system
2. The calculations you use -- are your units consistent? For
example you
mention watt-hour meters for energy measurement and you look at the
temperature
rise of the drum of water. Do you have the correct heat capacity for
water. What
units is the heat capacity in? I doubt that it is in Watt-hours / (deg
C - kg).
More likely it is in Joules / (deg C - kg) or calories / (deg C - g).
the heat
capacity of water is 1 calorie / (deg C - g). Assuming a 55 gal drum
you could
have as much as 220,000 g of water. A temperature rise of 1 deg C (are
you using
Fahrenheit thermometers? -- another conversion!) requires 220,000
calories or
~920,000 Joules, or ~260 Watt-hours. These numbers are very approximate
and are
given only as an independent check on your figures.
Alternatively, the heat capacity of water is ~0.0012 Watt-hours /
(deg C - g)
or 0.00065 Watt-hours / (deg F - g) or 0.30 Watt-hours / (deg F - lb)
Greg Bradburn
I am still a little confused about the "Apparatus" in your experiment. Has
the test been run without any cavitation taking place and the results
recorded. We all know that your "perpetual motion machine" that you have
created cannot be correct. There is also the possibility that these meters
you are using are taking the uncalculated energy, you mentioned that you
"apparatus" also has a watt-hour meter for the motor, why is a second motor
needed and what exactly does this "Apparatus" do?? The other thing is you
are ignoring the loss of energy to the environment which may make up this
20% that is constantly lost, pumps are not the most efficient machines in
the world! If you were to use a "black box" around the whole room that this
test is in and measured the total energy input- energy contained within the
box you would find it is equal. there is no way to create excess energy
from nothing.
Michael Baldwin
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