> But it is only liquid because it is under pressure. As soon as some
> liquid is in the lighter it vaporises to fill the chamber and if the
> resultant pressure is less than the pressure in the gas cylinder more
> liquid will go into the lighter until the system will reach stability.
>
>> Yes, adding liquid to the lighter gives back a bit of pressure for the
>> lighter's side, but not enough. The fresh liquid could vaporize to
>> provide more gas but that transformation requires a lot of heat which is
>> not available at the refill time.
>>
> The heat is taken from the air and the hand that is holding it. You can
> feel the lighter getting cold and you can hear the butane rushing into
> the lighter. The sound will stop when the pressure has equalised and the
> lighter will continue to fill up.

I haven't had chance to think in detail what is happening (nor do I have 
much experience with refilling lighters), but I suspect a good 
understanding of vapour pressure and how it changes with temperature is 
required:

http://en.wikipedia.org/wiki/Vapor_pressure
http://en.wikipedia.org/wiki/Butane_(data_page)#Vapor_pressure_of_liquid

Also bear in mind that it might not be 100% pure butane in the refill 
(or there might be some air in the lighter), so you better also know 
about partial pressure :-)

http://en.wikipedia.org/wiki/Partial_pressure

It sounds to me from what you describe that it's got something to do 
with things heating up or cooling down, causing the vapour pressure to 
change. An interesting experiment would be to prepare the lighter to be 
cooler or warmer than the refill canister and note any difference in 
behaviour when it is refilled.

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> The heat is taken from the air and the hand that is holding it. You can
> feel the lighter getting cold and you can hear the butane rushing into
> the lighter. The sound will stop when the pressure has equalised and the
> lighter will continue to fill up.

One possibility is that the sound you hear is actually a small amount of 
gas flowing rapidly into the lighter (or liquid that instantly 
evaporates as it hits the low pressure in the empty lighter) before the 
liquid starts to flow through the opening. When the sound stops that 
isn't because the pressure has equalised, just that it is liquid flowing 
much slower then rather than gas flowing quickly.

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On 11/16/2014 10:42 AM, Stephen wrote:
> On 16/11/2014 15:48, Thomas de Groot wrote:
>> On 16-11-2014 15:13, Stephen wrote:
>>> The heat is taken from the air and the hand that is holding it. You can
>>> feel the lighter getting cold and you can hear the butane rushing into
>>> the lighter. The sound will stop when the pressure has equalised and the
>>> lighter will continue to fill up.
>>>
>>
>> Such a long time since I stopped smoking that I only dimly remember
>> these things. The cold comes from the gas expanding, right? Same way as
>> a fridge.
>
> Correct.
>


Almost, but not fully.

The cold comes from the phase change from liquid to gas (It takes energy 
to evaporate the liquid, and the liquid will happily do so, because the 
equilibrium favors the gas phase (lower pressure on the cold side) If 
there is not enough pressure on the hot side (i.e. not enough coolant) 
to condense the gas to a liquid, the refrigeration is minimal to 
nonexistent.


... As for the rest of the conversation, it's fascinating; I think it's 
pressure difference that fills the lighter.

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On 17-11-2014 15:09, Raiford, Michael wrote:
> On 11/16/2014 10:42 AM, Stephen wrote:
>> On 16/11/2014 15:48, Thomas de Groot wrote:
>>> On 16-11-2014 15:13, Stephen wrote:
>>>> The heat is taken from the air and the hand that is holding it. You can
>>>> feel the lighter getting cold and you can hear the butane rushing into
>>>> the lighter. The sound will stop when the pressure has equalised and
>>>> the
>>>> lighter will continue to fill up.
>>>>
>>>
>>> Such a long time since I stopped smoking that I only dimly remember
>>> these things. The cold comes from the gas expanding, right? Same way as
>>> a fridge.
>>
>> Correct.
>>
>
>
> Almost, but not fully.
>
> The cold comes from the phase change from liquid to gas (It takes energy
> to evaporate the liquid, and the liquid will happily do so, because the
> equilibrium favors the gas phase (lower pressure on the cold side) If
> there is not enough pressure on the hot side (i.e. not enough coolant)
> to condense the gas to a liquid, the refrigeration is minimal to
> nonexistent.

Ah! Thank you for that correction. Phase change indeed.

>
>
> ... As for the rest of the conversation, it's fascinating; I think it's
> pressure difference that fills the lighter.
>

That's my best guess too.

Thomas

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Cooling in refrigeration is accomplished by adiabatic expansion of the
refrigerant gas - a rapid increase in the entropy due to the phase change from
liquid to gas.  From the ideal gas laws, P1V1/T1 = P2V2/T2   Change the pressure
and volume, and the temperature changes as a consequence.  See "Carnot cycle".

> I find this explanation neat, although I am not entirely satisfied
> somehow. Imho the problem resides in the fact that the liquid is a
> compressed gas which will want to expand as soon as there is a
> possibility for it.

That's irrelevant once the pressure differential between the two containers is
equilibrated.  What evaporated into gas can be recompressed back into liquid.

> I dimly remember that refilling a lighter often gave
> frustrating results as it was impossible to refill up to the initial
> level... with the exception of the use of a /pressurised/ filling mechanism.
>
> Thomas

Yes, when refilling with butane the filling container is obviously pressurized.

I believe that there are several interrelated issues here.

First, most people hold the butane refiller to the refilling valve, depress, and
then it's over and done with.  The system has not been given a chance to attain
equilibrium.

Second, there is likely to be a mixture of gases at play -

From http://lighterreviews.com/butane/  :

"Butane, is either of two isomeric flammable gaseous alkanes C4H10 usually
obtained from petroleum or natural gas and used as a fuel. Most butane for cigar
lighters is a mixture of of butane as noted above, isobutene , propane and a
small amount of air (yup the stuff we breath everyday). "

When you use the lighter, the butane flows from the bottom, through a "dip
tube".
http://www.inpharmix.com/jps/_images/exploded%20lighter%20labeled.jpg

Which means that the less volatile components, the ones that tend to remain
liquid as the lighter gets used, are pushed out by the headspace gas - composed
of the comparatively less liquifiable components.  After several
discharge/refill cycles, the lighter becomes filled with a higher proportion of
less liquifiable compounds, and so requires either more pressure to complete the
same fuel transfer, or venting of the more volatile components.

You could hold down the fuel lever to vent these gases before refilling, or more
effectively, hold the partially full lighter upside down while doing so -
causing the expansion of the less volatile components to push the more volatile
ones out the dip tube (which is now at the top).
You could then refill the lighter which has been depleted of those other
components.

To enhance filling, you could heat the butane refiller while filling with warm
water or a towel soaked in hot water.  Alternatively, you could chill the
lighter in the freezer before filling.

And, you could just wait and keep the filler depressed against the lighter for
far longer than most people do so that equilibrium can be more closely achieved.

Post a reply to this message

On 17/11/2014 17:04, Bald Eagle wrote:
> That's irrelevant once the pressure differential between the two containers is
> equilibrated.  What evaporated into gas can be recompressed back into liquid.
>

Yes, if we ignore heat transfer from the outside it is a closed system.

>> >I dimly remember that refilling a lighter often gave
>> >frustrating results as it was impossible to refill up to the initial
>> >level... with the exception of the use of a/pressurised/  filling mechanism.
>> >
>> >Thomas
> Yes, when refilling with butane the filling container is obviously pressurized.
>
> I believe that there are several interrelated issues here.
>

Nicely observed and the image is handy too.

 > http://www.inpharmix.com/jps/_images/exploded%20lighter%20labeled.jpg

I think that there is an additional factor. As Scott pointed out vapour 
pressure might have something to do with it as well. I did mention but 
it was probably overlooked.
When you fill the lighter the liquid fills the part of the chamber below 
the valve then stops. (Using the image you posted. The central divider 
in the lighter body, is the other way around and the gap is at the valve 
end.) At this point the system is in equilibrium. If you then pour some 
of the liquid into the empty part. You can fill the lighter to a similar 
level in the first chamber.
So I am guessing that it has to do with a function of vapour pressure 
and the distance from the top of the liquid to the inlet valve.


-- 

Regards
     Stephen

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On 17/11/2014 12:25, scott wrote:
>> The heat is taken from the air and the hand that is holding it. You can
>> feel the lighter getting cold and you can hear the butane rushing into
>> the lighter. The sound will stop when the pressure has equalised and the
>> lighter will continue to fill up.
>
> One possibility is that the sound you hear is actually a small amount of
> gas flowing rapidly into the lighter (or liquid that instantly
> evaporates as it hits the low pressure in the empty lighter) before the
> liquid starts to flow through the opening. When the sound stops that
> isn't because the pressure has equalised, just that it is liquid flowing
> much slower then rather than gas flowing quickly.
>

You could very well be right. I did not think of that.
Someone needs to do a doctoral theses on the subject. :-)

-- 

Regards
     Stephen

Post a reply to this message

Stephen <mca### [at] aolcom> wrote:

> When you fill the lighter the liquid fills the part of the chamber below
> the valve then stops. (Using the image you posted. The central divider
> in the lighter body, is the other way around and the gap is at the valve
> end.) At this point the system is in equilibrium. If you then pour some
> of the liquid into the empty part. You can fill the lighter to a similar
> level in the first chamber.

So....  what stops the gas from flowing over the top of the divider and
condensing into a liquid, yet at the same time allows the liquid butane to be
poured freely across the top?

When you use the lighter, do you empty one side, and then have to "refill" the
other side by pouring over from the other side?

Post a reply to this message

On 18/11/2014 15:53, Bald Eagle wrote:
> Stephen <mca### [at] aolcom> wrote:
>
>> When you fill the lighter the liquid fills the part of the chamber below
>> the valve then stops. (Using the image you posted. The central divider
>> in the lighter body, is the other way around and the gap is at the valve
>> end.) At this point the system is in equilibrium. If you then pour some
>> of the liquid into the empty part. You can fill the lighter to a similar
>> level in the first chamber.
>
> So....  what stops the gas from flowing over the top of the divider and
> condensing into a liquid, yet at the same time allows the liquid butane to be
> poured freely across the top?
>

Sorry, the lighter is disconnected from the refill at that point. Then 
reconnected to keep filling it. I've not tried to...

[Sounds of footsteps fading into the distance and returning]

Nothing, just tried it.
If my theory that brontosauruses are big and pointed at both ends, is 
right. Then the increase in pressure at the valve, as the liquid reaches 
it. Only, backs up the liquid from the butane cylinder, more. As I 
righted them, liquid started to flow into the empty part of the lighter.

> When you use the lighter, do you empty one side, and then have to "refill" the
> other side by pouring over from the other side?
>
>
>
Oo! Nice one! :-)
You almost got me with that. ;-)

-- 

Regards
     Stephen

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On 18-11-2014 17:44, Stephen wrote:
> On 18/11/2014 15:53, Bald Eagle wrote:
>> When you use the lighter, do you empty one side, and then have to
>> "refill" the
>> other side by pouring over from the other side?
>>

That happens automatically as a lighter is never constantly standing up 
right but is laying around, carried in pockets, shaken up, iow, 
mishandled ;-)

Thomas

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