Rosch taking orders on OU Bouyancy device.

[LibreEnergia]

Can some one tell me what the amount of energy in joules is required to compress a vessel volume of 1 ltr to 290 psi gauge pressure?-just ambiant air as gas.
Just wanting to see how that compares to a bouyant systems graph i have drawn up.

The answer depends on how you compress it and the properties of the gas being compressed.

For air, isothermal compression uses less energy compared with adiabatic, but takes an infinite amount of time vs adiabatic that can occur rapidly but requires perfect insulation.

During compression the work required is equal to the integral of P.dV from V1 to V2

The isothermal case is easiest to  derive.  Ideal gas law tells us P = nRT/V and the integral evaluates as W = -nRT ln(V1/V2)

So, to answer the question and actually put numbers to it you need to tell us how the air is compressed.

[tinman]

That is utter freaking nonsense.  Learn to use a protractor.Or just drink more Kool-Aid.

A protractor to get a 757 to do a 330* spiral dive at 470MPH,and nail the target-->thats a good one MarkE lol. Even TK has stated that the maneuver that was supposedly carried out on the pentagon attack would be extreemly dificult even for an experianced pilot-but the box cutter boys pulled it off no problem.
Oh,and by the way,we dont have kool aid here in OZ-we deal in facts-unlike your self.

 

Is your bet on nano thermite or dustification?  Maybe you think invisible giant space zombies pounded the buildings down with their giant invisible fists.

You have completely lost the plot MarkE. Your fire scenario is absolute junk-can never happen. Im sorry,but office furniture cant burn hot enough to turn steel to molten metal-like seen flowing out of the window's,and dug up from the rubble weeks later still molten hot.

You have failed to provide a picture(just 1) of another steel framed highrise building that has collapsed from fire-i have provided many that have not-even after days of burning.
In fact,you have failed to deliver on any credible evidence that supports your theories.

I am done debating this with you any further,as you are simply blind to the fact's that may upset the ballance of your perfect little world.

Now,if you would care to get back on topic,i have posted a question on the energy(in joules) required to fill a 1 ltr volume vessel to a pressure of 290psi gauge pressure. This IS in relation to this topic,and i believe this is something you can get right.

[d3x0r]

If you are trying to say that all of the input energy is lost to waste heat due to compression and expansion, then that is also wrong.

No it's lost to displacement of the water.  the heat gained/lost results in overall isothermal.  "Since air is a great insulator" ( http://www.physicsclassroom.com/class/thermalP/Lesson-1/Rates-of-Heat-Transfer  ) the heat it gets is going to remain for the few seconds it's compressed... it takes a long time to freeze a bottle of air so it's pressurized at room temp for instance (did this so my water vortex bottles had pressure).

what few milli-watts it sheds to the low water in pulled back when it decompresses at the top... so again tempurature difference is irrelavent.

but still none of that is used to make the motion.

There's no energy in displacement.

[tinman]

The answer depends on how you compress it and the properties of the gas being compressed.

For air, isothermal compression uses less energy compared with adiabatic, but takes an infinite amount of time vs adiabatic that can occur rapidly but requires perfect insulation.

During compression the work required is equal to the integral of P.dV from V1 to V2

The isothermal case is easiest to  derive.  Ideal gas law tells us P = nRT/V and the integral evaluates as W = -nRT ln(V1/V2)

So, to answer the question and actually put numbers to it you need to tell us how the air is compressed.

Thank you LE for the civil answer.
I mean to use a standard compressor-a high efficiency one.I know there will be losses in heat,but what is the energy we have in that 1ltr vessel at 290psi gauge pressure. Enviromental temperature will be close to 8*C

[d3x0r]

Anyway-back on track here.
Can some one tell me what the amount of energy in joules is required to compress a vessel volume of 1 ltr to 290 psi gauge pressure?-just ambiant air as gas.
Just wanting to see how that compares to a bouyant systems graph i have drawn up.

290psi is 19.7atm.  So 20x the pressure... which is 20L to 1L ...

a standard cubic foot represents 1.19804 moles  ( http://en.wikipedia.org/wiki/Standard_cubic_foot )
1 cubic foot = 28.3168L

n (moles of gas in 20L) =  (0.706 cubic-feet) * 1.19 = 0.84
R  8.3145 J/mol K    ( http://en.wikipedia.org/wiki/Gas_constant )
T 291.3333K (18.3333C)

ln(V2/v1)  (20L/1L) -2.995732274

= 0.84 * 8.3145 * 291.3 * -3
= 2031.491634J

divide by seconds to get watts.
---------------
applying these revisions to my spreadsheet to come out to J and therefore W/s increases COP to 1600 from 400  
Just looks better all the time.