Author Topic: Pression engine (Read 6033 times)

Gabriele · « **on:** January 20, 2015, 08:47:35 PM »

Hello. Can somebody help me doing some computation?
System is simple. We have a tank of water deep 20m and wide 10 meters.We have a vertical piston on the top-right from 0 to 10m,and an orizzontal one at 20 m of deep. We compress the water from the bottom by an half of the volume doubling his density. We bring the bottom piston from 20m to 10m so the density of water doubles.We let expand the upper piston to the right releasing energy needed to copress the liquid,plus the energy involved considering now the density from 0 to 10m to the right became 2g/cm3 from1g/cm3 (that is 0.25g/cm3x10mx10m) NOW,we move down the lower piston from 10 to 20m and from right to the left the upper right piston... it results to me the energy spend is in an assolute value 200 and a energy gained is 175. This is what i consider... the weight of water i need to rise from 20 to 10 to compress so -20kgx10. the energy in more i gain from expanding the upper right piston that is 0.25 x 10m x10m(should be 1 but on the right of the wall we have a spring that compensate natural pression on the wall of 10m of water) and then i gain also 10kg to 20kg from the fall of the lower piston so 15x10m... -200+25+150 = -25... why? Thanks....(here i post an approximation of what i would do...)

Gabriele · « **Reply #1 on:** January 20, 2015, 08:58:10 PM »

It can be done with gas too... damn... what have i lost by the way (excluding the brain

)?

LibreEnergia · « **Reply #2 on:** January 20, 2015, 11:06:21 PM »

Water is not compressible, so the system would not work as you presume.

If you were to use a gas instead then it should be self evident there is no energy to be gained by cycling the gas over any range of pressures. First law of thermodynamics applies...

Gabriele · « **Reply #3 on:** January 21, 2015, 06:19:57 PM »

From wiki: The compressibility of water is a function of pressure and temperature. At 0 °C, at the limit of zero pressure, the compressibility is 5.1×10−10 Pa−1.[31] At the zero-pressure limit, the compressibility reaches a minimum of 4.4×10−10 Pa−1 around 45 °C before increasing again with increasing temperature. As the pressure is increased, the compressibility decreases, being 3.9×10−10 Pa−1 at 0 °C and 100 MPa.

The bulk modulus of water is 2.2 GPa.[32] The low compressibility of non-gases, and of water in particular, leads to their often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume.[32]

http://en.wikipedia.org/wiki/Properties_of_water#Compressibility

If i can comprime water by 2%,the behavior don't change...i simulated it... (bycalcolus)...perhaps i miss something...

For a gas is the same concept insted. (each centimeter of fall,pression rise by the amount of the weight of a cm of gas!)

LibreEnergia · « **Reply #4 on:** January 21, 2015, 10:27:27 PM »

Quote from: Gabriele on January 21, 2015, 06:19:57 PM

From wiki: The compressibility of water is a function of pressure and temperature. At 0 °C, at the limit of zero pressure, the compressibility is 5.1×10−10 Pa−1.[31] At the zero-pressure limit, the compressibility reaches a minimum of 4.4×10−10 Pa−1 around 45 °C before increasing again with increasing temperature. As the pressure is increased, the compressibility decreases, being 3.9×10−10 Pa−1 at 0 °C and 100 MPa.

The bulk modulus of water is 2.2 GPa.[32] The low compressibility of non-gases, and of water in particular, leads to their often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume.[32]

http://en.wikipedia.org/wiki/Properties_of_water#Compressibility

If i can comprime water by 2%,the behavior don't change...i simulated it... (bycalcolus)...perhaps i miss something...

For a gas is the same concept insted. (each centimeter of fall,pression rise by the amount of the weight of a cm of gas!)

As you correctly point out water is somewhat compressible at extreme pressures.

However, you were talking about 'doubling' the density of the water. You would need enormous forces to do that and its is simply not practical.

In any case compressing liquid or a gas results in no net energy gain around a cycle so why bother.

Gabriele · « **Reply #5 on:** January 24, 2015, 09:10:46 PM »

Mine, wanted to be only a question to help me solve this kind of problem,because a can't focus the exit. I know,in a cycle where i rise,let fall,compresss a gas or a liquid,there must be always an equal sum of energy used and gained. My is could be an easy exercise for you. Can you help me? I will rewrite the problem if you didn't understand what i wrote. I compress water using x energy + the energy needed to rise the weight of water from the botton. I let expand it laterlally from the same distance i compressed...than i bring she back where it was,down to te bottom. If i consider a recatangle tank of 10x20m,energy i use to compress is a LOT+10kg of force per 10m... when i decompress it energy water should return should be that alot+10kg of force per 10m,,, but in this case i computated is less...always that LOT OF ENERGY+should be 10x10.. but density cannot return 1(medium densiity from 0to 10mof deep)x10(height of the moblie wall)x10(travell) Medium density will pass from 1 to 0.5, so where does de rest of energy come from? From the lower level of the water now stands and doesn't have no more the 10m of water above her so the compression of the water decrease a little permitting this 10-12% of energy to return? 10-12% of the whole is a lot of energy considering water will increase her volume for 1/1000000 c.ca.... if some one can enlight me about this trouble, thanks

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Author Topic: Pression engine (Read 6033 times)

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