| Topic: |
Science > Physics |
| User: |
"Jeff Wisnia" |
| Date: |
06 Apr 2007 10:28:00 AM |
| Object: |
Propane Question |
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
.
|
|
| User: "Androcles" |
|
| Title: Re: Propane Question |
06 Apr 2007 12:52:38 PM |
|
|
"Jeff Wisnia" <jwisnia@conversent.net> wrote in message =
news:131cpoohfaiboe6@corp.supernews.com...
This is a question I once wondered about and now I don't remember ever =
if I ever got an answer.
=20
Take two identically sized and shaped propane tanks, one nearly full =
of=20
liquid and the other nearly empty, coupled together with a tube =
between=20
their tops.
=20
If they are left undisturbed long enough in a constant air temperature =
environment of say 70 F, will the liquid levels in the two containers=20
eventually equalize on their own?
If it doesn't change immediately, why should it change at all?
If the tube reaches the bottom of the tanks then expect a syphon,
but I'll assume that is not the case.
And if they won't, will they if the=20
air temperature surrounding them periodically cycles up and back down=20
again a few degrees.
Yes, eventually, but theoretically only at t =3D infinity.
What's the physics governing this?
Start at the extreme, one entirely filled with gas, the other=20
with liquid. Now cool both. Nothing happens to the level
in the full cylinder, but SOME vapour condenses to liquid in=20
the empty cylinder.=20
Now heat both. SOME liquid in the full cylinder vaporises and=20
flows into the empty cylinder.=20
Continue with the cycle and a balance is eventually reached,=20
but it is not a linear function of time. It has a "half-life" where
if 1/4 the liquid has been transferred in a week of continuous=20
cycling then 1/8 will transfer the next week, 1/16 the week after,=20
1/32 the week after that and so on. So it approaches the=20
same level in both but never quite reaches it until the end of=20
time. In practical terms, however, the difference soon becomes
too small to measure.
http://www.kettering.edu/~drussell/Demos/SHO/damp.html
Does the damped oscillation ever stop entirely?
=20
Thanks guys,
=20
Jeff
--=20
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
=20
.
|
|
|
|
| User: "Paul Cardinale" |
|
| Title: Re: Propane Question |
06 Apr 2007 11:28:33 AM |
|
|
Jeff Wisnia wrote:
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
If the connecting tube is at the bottom of the tanks, allowing liquid
to transfer, the levels will equallize quickly; the liquid presure
depends upon the height of the liquid. If the tube is at the top,
allowing gas to transfer, the levels will never equalize; the vapor
pressure depends only upon the temperature. Air pressure has no
effect on anything inside the tanks.
Paul Cardinale
.
|
|
|
| User: "" |
|
| Title: Re: Propane Question |
06 Apr 2007 12:36:06 PM |
|
|
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, "Paul Cardinale" <pcardinale@volcanomail.com> writes:
Jeff Wisnia wrote:
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
If the connecting tube is at the bottom of the tanks, allowing liquid
to transfer, the levels will equallize quickly; the liquid presure
depends upon the height of the liquid. If the tube is at the top,
allowing gas to transfer, the levels will never equalize; the vapor
pressure depends only upon the temperature. Air pressure has no
effect on anything inside the tanks.
Pressure of the propane vapors changes with altitude. There's only
12 inches or so of altitude to play with inside the tanks, but
if all other things are equal, this will come into play and eventually
the tanks will equalize with the propane at the same level even
though the tanks are only connected at the top.
Propane will evaporate from the surface of the more-full tank since
the vapor/liquid interface there is at a higher elevation and, hence,
at a lower pressure than in the less-full tank.
One might estimate the rate of transfer by figuring out the
pressure differential (what is the density of propane vapors
at room temperature and what is the difference in fluid levels?)
This pressure differential equates to a temperature differential
(how does the vapor pressure of propane vary with temperature?)
This temperature differential equates to a rate of heat flow
(what is the R value of a pair of steel tanks of propane in air?)
This rate of heat flow equates to a time parameter (how much
heat does it take to vaporize a one cm layer of propane in a
30 cm diameter tank?)
This should lead to a first order linear differential equation whose
solution is an exponential decay in the difference in fluid levels
over time.
.
|
|
|
| User: "Noman Lapetos" |
|
| Title: Re: Propane Question |
06 Apr 2007 01:02:18 PM |
|
|
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, "Paul
Cardinale" <pcardinale@volcanomail.com> writes:
Jeff Wisnia wrote:
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
If the connecting tube is at the bottom of the tanks, allowing liquid
to transfer, the levels will equallize quickly; the liquid presure
depends upon the height of the liquid. If the tube is at the top,
allowing gas to transfer, the levels will never equalize; the vapor
pressure depends only upon the temperature. Air pressure has no
effect on anything inside the tanks.
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
.
|
|
|
| User: "" |
|
| Title: Re: Propane Question |
06 Apr 2007 01:04:37 PM |
|
|
In article <46168ac9$0$97252$892e7fe2@authen.yellow.readfreenews.net>, "Noman Lapetos" <nospam@nospam.com> writes:
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, "Paul
Cardinale" <pcardinale@volcanomail.com> writes:
Jeff Wisnia wrote:
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
If the connecting tube is at the bottom of the tanks, allowing liquid
to transfer, the levels will equallize quickly; the liquid presure
depends upon the height of the liquid. If the tube is at the top,
allowing gas to transfer, the levels will never equalize; the vapor
pressure depends only upon the temperature. Air pressure has no
effect on anything inside the tanks.
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
Actually, yes, even in a closed pressurized system, gravity isn't
switched off over there. Of course, the amount of change is too small
to be of concern (or even noticeable) in most systems.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
|
|
|
| User: "Gordon" |
|
| Title: Re: Propane Question |
06 Apr 2007 01:53:53 PM |
|
|
On Fri, 06 Apr 2007 18:04:37 GMT,
wrote:
In article <46168ac9$0$97252$892e7fe2@authen.yellow.readfreenews.net>, "Noman Lapetos" <nospam@nospam.com> writes:
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, "Paul
Cardinale" <pcardinale@volcanomail.com> writes:
(snip)
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
Actually, yes, even in a closed pressurized system, gravity isn't
switched off over there. Of course, the amount of change is too small
to be of concern (or even noticeable) in most systems.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
This isn't a matter of altitude above the liquid surface. Any
difference in gas pressure as a function of altitude differences
of this magnitude would be EXTREMELY minimal, but would relate
to the altitude at the connection fitting, relative to the earth,
not relative to the propane fluid level. So, if both tanks are
placed on a level surface and the connection from tank to tank is
at the same altitude relative to earth, there would be no
transfer of gas from one tank to the other by this means. Gordon
.
|
|
|
| User: "" |
|
| Title: Re: Propane Question |
06 Apr 2007 04:17:43 PM |
|
|
In article <9i5d13pb6vrpc9ltklh75k9d62c3q5cvt1@4ax.com>, Gordon <gordonlr@DELETEswbell.net> writes:
On Fri, 06 Apr 2007 18:04:37 GMT,
wrote:
In article <46168ac9$0$97252$892e7fe2@authen.yellow.readfreenews.net>, "Noman Lapetos" <nospam@nospam.com> writes:
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, "Paul
Cardinale" <pcardinale@volcanomail.com> writes:
(snip)
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
Actually, yes, even in a closed pressurized system, gravity isn't
switched off over there. Of course, the amount of change is too small
to be of concern (or even noticeable) in most systems.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
This isn't a matter of altitude above the liquid surface.
Any difference in gas pressure as a function of altitude differences
of this magnitude would be EXTREMELY minimal, but would relate
to the altitude at the connection fitting, relative to the earth,
not relative to the propane fluid level.
Sigh. We're talking about stationary situation. Given stationary fluid in
gravity field, you've a vertical pressure gradient of g*density.
That's all. The connections are not relevant to this, they're only
relevant to any flow that may be present till equilibrium is
established.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
|
|
|
| User: "Noman Lapetos" |
|
| Title: Re: Propane Question |
06 Apr 2007 10:03:36 PM |
|
|
<> wrote in message
news:XNyRh.64$25.202@news.uchicago.edu...
In article <9i5d13pb6vrpc9ltklh75k9d62c3q5cvt1@4ax.com>, Gordon
<gordonlr@DELETEswbell.net> writes:
On Fri, 06 Apr 2007 18:04:37 GMT,
wrote:
In article <46168ac9$0$97252$892e7fe2@authen.yellow.readfreenews.net>,
"Noman Lapetos" <nospam@nospam.com> writes:
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>,
"Paul
Cardinale" <pcardinale@volcanomail.com> writes:
(snip)
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
Actually, yes, even in a closed pressurized system, gravity isn't
switched off over there. Of course, the amount of change is too small
to be of concern (or even noticeable) in most systems.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
This isn't a matter of altitude above the liquid surface.
Any difference in gas pressure as a function of altitude differences
of this magnitude would be EXTREMELY minimal, but would relate
to the altitude at the connection fitting, relative to the earth,
not relative to the propane fluid level.
Sigh. We're talking about stationary situation. Given stationary fluid
in
gravity field, you've a vertical pressure gradient of g*density.
That's all. The connections are not relevant to this, they're only
relevant to any flow that may be present till equilibrium is
established.
right, there is no fluid flow, only gas flow.
.
|
|
|
| User: "" |
|
| Title: Re: Propane Question |
06 Apr 2007 10:41:31 PM |
|
|
In article <461709b2$0$97242$892e7fe2@authen.yellow.readfreenews.net>, "Noman Lapetos" <nospam@nospam.com> writes:
< > wrote in message
news:XNyRh.64$25.202@news.uchicago.edu...
In article <9i5d13pb6vrpc9ltklh75k9d62c3q5cvt1@4ax.com>, Gordon
<gordonlr@DELETEswbell.net> writes:
On Fri, 06 Apr 2007 18:04:37 GMT,
wrote:
In article <46168ac9$0$97252$892e7fe2@authen.yellow.readfreenews.net>,
"Noman Lapetos" <nospam@nospam.com> writes:
<briggs@encompasserve.org> wrote in message
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>,
"Paul
Cardinale" <pcardinale@volcanomail.com> writes:
(snip)
Pressure of the propane vapors changes with altitude.
not in a closed pressurized system.
Actually, yes, even in a closed pressurized system, gravity isn't
switched off over there. Of course, the amount of change is too small
to be of concern (or even noticeable) in most systems.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
This isn't a matter of altitude above the liquid surface.
Any difference in gas pressure as a function of altitude differences
of this magnitude would be EXTREMELY minimal, but would relate
to the altitude at the connection fitting, relative to the earth,
not relative to the propane fluid level.
Sigh. We're talking about stationary situation. Given stationary fluid
in
gravity field, you've a vertical pressure gradient of g*density.
That's all. The connections are not relevant to this, they're only
relevant to any flow that may be present till equilibrium is
established.
right, there is no fluid flow, only gas flow.
The term "fluid" in physics encompasses gases and liquids. And in the
situation described there is no flow of significance.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
|
|
|
|
| User: "tj Frazir" |
|
| Title: Re: Propane Question |
07 Apr 2007 07:50:53 AM |
|
|
Nope. Your twin tanks are conected so you can use 1 gage .
Turn your bic lighter upside down .
That conection between the two sides at the top of the bic is at the
bottom acting as the line between two tanks.
You can draw the gas from the empty tank.
The full tank will feed the empty tank wile you draw from the empty
side.
I
.
|
|
|
|
|
|
|
|
|
| User: "Androcles" |
|
| Title: Re: Propane Question |
06 Apr 2007 03:09:49 PM |
|
|
<briggs@encompasserve.org> wrote in message =
news:mKkMcpQHnJGx@eisner.encompasserve.org...
In article <1175876913.471011.219220@b75g2000hsg.googlegroups.com>, =
"Paul Cardinale" <pcardinale@volcanomail.com> writes:
=20
Jeff Wisnia wrote:
This is a question I once wondered about and now I don't remember =
ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full =
of
liquid and the other nearly empty, coupled together with a tube =
between
their tops.
If they are left undisturbed long enough in a constant air =
temperature
environment of say 70 F, will the liquid levels in the two =
containers
eventually equalize on their own? And if they won't, will they if =
the
air temperature surrounding them periodically cycles up and back =
down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
=20
If the connecting tube is at the bottom of the tanks, allowing liquid
to transfer, the levels will equallize quickly; the liquid presure
depends upon the height of the liquid. If the tube is at the top,
allowing gas to transfer, the levels will never equalize; the vapor
pressure depends only upon the temperature. Air pressure has no
effect on anything inside the tanks.
=20
Pressure of the propane vapors changes with altitude. There's only
12 inches or so of altitude to play with inside the tanks, but
if all other things are equal, this will come into play and eventually
the tanks will equalize with the propane at the same level even
though the tanks are only connected at the top.
=20
Propane will evaporate from the surface of the more-full tank since
the vapor/liquid interface there is at a higher elevation and, hence,
at a lower pressure than in the less-full tank.
Thus vapour from the less full tank will flow from the high pressure=20
to low pressure region, filling the full tank until the low pressure =
tank=20
reaches vacuum and keep the tanks out of balance. You are totally =
psychotic.
.
|
|
|
|
|
|
| User: "boson boss" |
|
| Title: Re: Propane Question |
06 Apr 2007 05:22:41 PM |
|
|
On Apr 6, 5:28 pm, Jeff Wisnia <jwis...@conversent.net> wrote:
This is a question I once wondered about and now I don't remember ever
if I ever got an answer.
Take two identically sized and shaped propane tanks, one nearly full of
liquid and the other nearly empty, coupled together with a tube between
their tops.
If they are left undisturbed long enough in a constant air temperature
environment of say 70 F, will the liquid levels in the two containers
eventually equalize on their own? And if they won't, will they if the
air temperature surrounding them periodically cycles up and back down
again a few degrees.
What's the physics governing this?
Thanks guys,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
Surface of fluid is a miracle of nature. in one hand the fluid could
flow wherever, and gas would equalize apart from that.
.
|
|
|
|
|
Related Articles |
|
|
