How far would one litre of water have to fall before it boils its self.?

Question

I have a pipe going down into the ground xkm in that pipe there are turbines that can be adjusted to resist the flow of water down the pipe, this resistance heats the water, by the time the water gets to to bottom of the pipe it is boiling, it returns to the surface as steam along another insulated pipe. how far does the water have to fall before it produces enough energy to boil itself?

we are concidering changing the turbines to the type used in common hydro electric systems, with the exception the electricity produced is used to heat the falling water, would this be more effective?

The pipe is made of 2 walled titanium vacuum flask structure to reduce heat losses, (resistance coefficient )= varies, but is adjusted so as to produce the maximum transfer of energy, the diameter of the inner circle of the pipe, =1metre, the temperature of water going into the pipe, on average measures 20 degrees,

There are few losses because the further the water falls the higher the potential energy, the potential energy can exceed 100% for two reasons, firstly no limit has been set for the fall of the water, the second has to do with the environment, as the water falls it picks up geothermal energy from the earth, we try to keep this to a minimum as we are only trying to take the energy from the rotation of the earth. the system is not perpetual motion as the earth will one day stop rotation, when this happen the potential energy will be equal to zero.

Answer 1

Essentially you are saying: I will convert the energy change in moving with the pull of gravity from a 'higher' to a 'lower' point into kinetic energy to turn turbines which I will then convert to electrical energy to boil the water again....

Each step is less than 100% efficient, so you'll lose energy at each step.....so it won't work...believe me I used to think about the same stuff...... can't do it m8, but nice try ;)

Answer 2

This sounds like a second law perpetual motion machine.

Given the pressure you can look at the locations on the vapor dome for quality zero and 100% then determine the enthalpy change between them, and thats the energy that must be added. consider the energy to be mgh, you know the mass and g is effectively constant so you can determine h, thats your depth.

So you have not-yet superheated water at the bottom of a shaft, and you want it to rise. There is heat flow through the walls of the shaft, it will condense, and drip down. You have to account for that.

There is entropy to consider.

Instead of doing a balance of energy, do an avaliability/exergy analysis of your system. You will probably find that it has to create exergy (impossible) to work

There are 5 laws that for every observed circumstance in all of known science are always always valid:
conservation of mass,
balance of linear momentum
balance of angular momentum
balance of energy
the second law of thermodynamics (entropy).

If you are attempting to violate any one of these, its the graveyard of bright people. These things have essentially the entire history of science supporting them. Its probably a better idea to go try to prove the reimann hypothesis, or solve any of the clay institute of mathematics problems, then try to violate these laws. You are making it harder because you are trying to use 1890's technology (thermodynamics, heat and mass transfer) to do so. Bleeding edge quantum might have some infinitesimal hope of redefining something and squeaking past some part... if you were the next einstein, maybe. Trying to be the old Gibbs and beat 400+ years of good science.. thats "a tough row to hoe".

Answer 3

I've just worked it out to 32km assuming that all the KE of the water turns to heat and that no terminal velocity is reached.
Also, there will be heat transfer from the water as it heats up and so losses from the system.
Sounds like a good system but you need some serious research before you invest big money in it!

Answer 4

Gee, you'll probably have to give us some numbers like what's the pipe made of (resistance coefficient), the diameter of the inner circle of the pipe, the temperature of water going into the pipe, and I think that's it.

Answer 5

Well, its not the distance that makes it boil it self, its the height because if you poured water out from a rocket going through the stratosphere, it would boil because the gravity and pressure collide and cause heat as you travel faster and faster you pressure builds up and so does your heat because you are going too fast you body/object can't take the heat, it burns up or in this cause evaporates and becomes so light because of heat, it is so light in its gaseous form it's upthrust effects it more causing it to rise and not fall.

Answer 6

Err...free-falling water would never do that, notice how rain isn't boiling?

Its because air-resistance provides only enough to resist the force of gravity, and the water cools off very fast on its own, with contact to air.

You'd have to add many other things before you could pull that one off.

Answer 7

you know exactly what you are saying it would seem but i haven't a bloody clue. so how about coming back again and give us the answer on another page, like boiling water and i will know what to look for.

Answer 8

to the bottom of the pipe.

Answer 9

mmm..this question is going to require a large amount of effort...but I suggest researching ways you could create cavitation in your system.....

Answer 10

to the bottom of3" hot pan