Have I read or heard somewhere that putting insulation of some sort around gas bottles to keep the worst of the cold off them can be counter productive and slows / stops the vapourisation within the bottle.
JohnM
JohnM
LPG Gassing
- Thread starter JohnM20
- Start date
Yes you have read that…….
Think about it, temperature is a relative measure. When the LPG boils to provide your caravan appliances with gas, heat will be removed from the surrounding air, even if that air is below 0 degC.
This heat is the energy required to turn the LPG from liquid into gas without raising the temperature of the LPG.
Insulating the LPG cylinder will deny the LPG access to its source of heat from the surrounding air.
Since Propane will boil down to –30degC even air at –10degC is a source of heat for it to boil.
Butane will stop boiling at about 1degC and is not used as a reliable source of gas for caravans in our winters for this reason.
Think about it, temperature is a relative measure. When the LPG boils to provide your caravan appliances with gas, heat will be removed from the surrounding air, even if that air is below 0 degC.
This heat is the energy required to turn the LPG from liquid into gas without raising the temperature of the LPG.
Insulating the LPG cylinder will deny the LPG access to its source of heat from the surrounding air.
Since Propane will boil down to –30degC even air at –10degC is a source of heat for it to boil.
Butane will stop boiling at about 1degC and is not used as a reliable source of gas for caravans in our winters for this reason.
Damian
Moderator
Absolutely correct.
Insulating the cylinder will stop it working completely.
To produce gas from its liquid state in the cylinder, it requires heat from the atmosphere.
Butane will stop producing gas for any usable purpose at around 4 degrees C.
Propane will continue to produce usable gas to around -30 degrees C
Insulating the cylinder will stop it working completely.
To produce gas from its liquid state in the cylinder, it requires heat from the atmosphere.
Butane will stop producing gas for any usable purpose at around 4 degrees C.
Propane will continue to produce usable gas to around -30 degrees C
Thanks guys
I thought I had heard something somewhere but couldn't recall the reason for not giving the bottles a duvet jacket !
JohnM
I thought I had heard something somewhere but couldn't recall the reason for not giving the bottles a duvet jacket !
JohnM
Latent heat of evaporation is only part of the equation.
When a gas or vapour (its state at our defined room temp) is conveted into a liquid we dont actually cool it.- after all to get turn nitrogen into liquid nitrogen we would need something colder than -196 deg C, which is a little difficult to get to so its compressed. Compressing the gas into a liquid cools it and eventually you get a liquid and to remain as a liquid it has to be under pressure.
Liquid nitrogen will boil at -195 deg c .
To turn it back to a gas again we dont actually need heat to "boil" it as such What we need is a pressure drop. The drop in pressure causes the liquid to boil, and a compressed gas ( liquid) will re vapourise as soon as it is subjected to a pressure drop.But thsi can lead to another problem in that the liquid itself expands rapidly and you wolud get liquid lpg coming out of your nozzle.
So heat helps it " boil" as does the essure drop.
Water at 35000' boils at 60 degrees, not becuas of the heat but due to low pressure. At the bottom of the ocean it boils at 360 deg celsius due to the pressure of the water on top of it.
its a bit like the old aerofoil and lift on a wing that just about everyone gets wrong. not totally wrong but they miss the fatc that it not only requires bernoullies law but also newtons 3rd law.
Have fun and beat the CC booking frenzy.
When a gas or vapour (its state at our defined room temp) is conveted into a liquid we dont actually cool it.- after all to get turn nitrogen into liquid nitrogen we would need something colder than -196 deg C, which is a little difficult to get to so its compressed. Compressing the gas into a liquid cools it and eventually you get a liquid and to remain as a liquid it has to be under pressure.
Liquid nitrogen will boil at -195 deg c .
To turn it back to a gas again we dont actually need heat to "boil" it as such What we need is a pressure drop. The drop in pressure causes the liquid to boil, and a compressed gas ( liquid) will re vapourise as soon as it is subjected to a pressure drop.But thsi can lead to another problem in that the liquid itself expands rapidly and you wolud get liquid lpg coming out of your nozzle.
So heat helps it " boil" as does the essure drop.
Water at 35000' boils at 60 degrees, not becuas of the heat but due to low pressure. At the bottom of the ocean it boils at 360 deg celsius due to the pressure of the water on top of it.
its a bit like the old aerofoil and lift on a wing that just about everyone gets wrong. not totally wrong but they miss the fatc that it not only requires bernoullies law but also newtons 3rd law.
Have fun and beat the CC booking frenzy.
Damian
Moderator
Well,thank you for that totally off the wall posting about nitrogen , oceanic water and aerofoil lift characteristics ,,,,,,,not a lot to do with Butane and Propane, which , despite very eloquent long winded politically correct dissertations, makes not the slightest difference to the simple fact, and lets face it, most people like simple things,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,DONT insulate the cylinder, and Propane works better at lower temperatures than Butane.
Which is all the OP was asking
Which is all the OP was asking
You are technically right Philspadders.
……but my answer to the OP was to explain why he should not insulate his gas cylinder and to point out that if he was using Butane why he would be getting poor performance in near zero ambient temperatures.
I also took into account that others may read my answer so as Damian says........"I kept it simple"
……but my answer to the OP was to explain why he should not insulate his gas cylinder and to point out that if he was using Butane why he would be getting poor performance in near zero ambient temperatures.
I also took into account that others may read my answer so as Damian says........"I kept it simple"
Thanks for that Damien.
I always try to offer correct information unlike the " it wont work if you insulate it" .
I always try to offer correct information unlike the " it wont work if you insulate it" .
Oh Dear,
I’m likely to be accuses of perpetuating a thread at a depth of information well beyond the needs of the OP well I apologise for that now so if you don’t want a technical debate read no further.
Phil has tried to give some examples of the extremes of conditions that can affect the transphasic conditions of fluids, and much of what he writes has a ring of truth, but in some major respects his answer is flawed.
Quote :-“Compressing the gas into a liquid cools it and eventually you get a liquid and to remain as a liquid it has to be under pressure.”
When you compress a gas, the mass of gas actually gets hotter, as the molecules of gas resist the forces trying to compress them.
Quote:- “To turn it back to a gas again we dont actually need heat to "boil" it as such What we need is a pressure drop. The drop in pressure causes the liquid to boil, and a compressed gas (liquid) will re vapourise as soon as it is subjected to a pressure drop.”
When a pressure drop above a liquid occurs, the liquid will try to “boil” but it can only do that if there is enough latent heat within the body of the liquid to excite the molecules enough to cause them to break free as a vapour (boiling). Not enough heat and the molecules cannot become free of the liquid mass. – This is the Butane scenario
So contrary to Phil’s statement Heat or energy is an essential participant in both the condensation and evaporation of gaseous fluids
And insulating LPG bottles without an additional source of heat is wrong
I’m likely to be accuses of perpetuating a thread at a depth of information well beyond the needs of the OP well I apologise for that now so if you don’t want a technical debate read no further.
Phil has tried to give some examples of the extremes of conditions that can affect the transphasic conditions of fluids, and much of what he writes has a ring of truth, but in some major respects his answer is flawed.
Quote :-“Compressing the gas into a liquid cools it and eventually you get a liquid and to remain as a liquid it has to be under pressure.”
When you compress a gas, the mass of gas actually gets hotter, as the molecules of gas resist the forces trying to compress them.
Quote:- “To turn it back to a gas again we dont actually need heat to "boil" it as such What we need is a pressure drop. The drop in pressure causes the liquid to boil, and a compressed gas (liquid) will re vapourise as soon as it is subjected to a pressure drop.”
When a pressure drop above a liquid occurs, the liquid will try to “boil” but it can only do that if there is enough latent heat within the body of the liquid to excite the molecules enough to cause them to break free as a vapour (boiling). Not enough heat and the molecules cannot become free of the liquid mass. – This is the Butane scenario
So contrary to Phil’s statement Heat or energy is an essential participant in both the condensation and evaporation of gaseous fluids
And insulating LPG bottles without an additional source of heat is wrong
as i posted john , latent heat is only part of the equation so perhaps you should go back and read the post fully.
also, perhaps you could explain why when i designed and built a glycol regen plant for drying LPG i got it totally wrong by insulating the liquid gas vessel and relying on a series of orifice plates, restrictors and self regulating globe valves to vapourise during de pressurisation for flow to a water bath heater to warm up the vapour. It seemed to work, and as far as i know still does.
As i posted John , heat is only a small part of the equation and i am not going to get in to a point scoring who knows more contest with you.
also, perhaps you could explain why when i designed and built a glycol regen plant for drying LPG i got it totally wrong by insulating the liquid gas vessel and relying on a series of orifice plates, restrictors and self regulating globe valves to vapourise during de pressurisation for flow to a water bath heater to warm up the vapour. It seemed to work, and as far as i know still does.
As i posted John , heat is only a small part of the equation and i am not going to get in to a point scoring who knows more contest with you.
Damian
Moderator
Before this topic ends up as a full blown chemistry lesson and one poster trying to prove his point to distraction, swap email addresses and continue the debate away from the forum.
For all USEFUL CARAVAN purposes, it is enough to know that Propane is the gas to use in winter, Butane is OK for summer, and insulating the cylinder is counter productive.
For all USEFUL CARAVAN purposes, it is enough to know that Propane is the gas to use in winter, Butane is OK for summer, and insulating the cylinder is counter productive.
Damaina,
I am not trrying to score points, I am discussing a technical issue that a contributor has raised. The information was not complete and as a result it gave a wrong impression.
Phil,
Within the process you describe, the latent heat had to be managed, thus you could not ignore as it is a natural and significant characteristic of the process you were trying to achieve.
I will not be swapping emails on this subject.
I am not trrying to score points, I am discussing a technical issue that a contributor has raised. The information was not complete and as a result it gave a wrong impression.
Phil,
Within the process you describe, the latent heat had to be managed, thus you could not ignore as it is a natural and significant characteristic of the process you were trying to achieve.
I will not be swapping emails on this subject.
Rotating Heat Exchangers is what's needed here
With a rotating heat exchanger outlet air heats (or cools) the exchanger when the wheel passes through the outlet air flow. The energy is transferred to the make up air when the wheel passes through the make up air.
Both sensible and latent heat may be transferred. Latent heat when moisture in the outlet air condensates on the wheel. Moisture may be transferred with heat exchangers using hygroscopic wheels. For exchangers without hygroscopic wheels, the condensate is drained out.
The intervention of the famous bypass nodulator valve will also improve efficiency.
The moisture transfer efficiency of an heat recovery unit can be expressed as:
μm = (x2 - x1) / (x3 - x1) (2)
where
μm = moisture transfer efficiency
x1 = moisture outside air before the heat exchanger (kg/kg)
x2 = moisture outside air after the heat exchanger (kg/kg)
x3 = moisture inside air before the heat exchanger (kg/kg)
I've only ever used propane and never ever had any problems as suggested even in sub zero temperatures.
With a rotating heat exchanger outlet air heats (or cools) the exchanger when the wheel passes through the outlet air flow. The energy is transferred to the make up air when the wheel passes through the make up air.
Both sensible and latent heat may be transferred. Latent heat when moisture in the outlet air condensates on the wheel. Moisture may be transferred with heat exchangers using hygroscopic wheels. For exchangers without hygroscopic wheels, the condensate is drained out.
The intervention of the famous bypass nodulator valve will also improve efficiency.
The moisture transfer efficiency of an heat recovery unit can be expressed as:
μm = (x2 - x1) / (x3 - x1) (2)
where
μm = moisture transfer efficiency
x1 = moisture outside air before the heat exchanger (kg/kg)
x2 = moisture outside air after the heat exchanger (kg/kg)
x3 = moisture inside air before the heat exchanger (kg/kg)
I've only ever used propane and never ever had any problems as suggested even in sub zero temperatures.
Well at least I kept my Posts simple.........I know my abilities!
Deliberately as it happens as I knew the Prof would step in with the definitive answer sooner or later.
He has not let me down
Deliberately as it happens as I knew the Prof would step in with the definitive answer sooner or later.
He has not let me down
I knew that!Dustydog said:Rotating Heat Exchangers is what's needed here
With a rotating heat exchanger outlet air heats (or cools) the exchanger when the wheel passes through the outlet air flow. The energy is transferred to the make up air when the wheel passes through the make up air.
Both sensible and latent heat may be transferred. Latent heat when moisture in the outlet air condensates on the wheel. Moisture may be transferred with heat exchangers using hygroscopic wheels. For exchangers without hygroscopic wheels, the condensate is drained out.
The intervention of the famous bypass nodulator valve will also improve efficiency.
The moisture transfer efficiency of an heat recovery unit can be expressed as:
μm = (x2 - x1) / (x3 - x1) (2)
where
μm = moisture transfer efficiency
x1 = moisture outside air before the heat exchanger (kg/kg)
x2 = moisture outside air after the heat exchanger (kg/kg)
x3 = moisture inside air before the heat exchanger (kg/kg)
I've only ever used propane and never ever had any problems as suggested even in sub zero temperatures.
After about 50 years of caravanning I still do not understand why some people persist in saying that propane for winter and butane for summer. Surely it makes more sense to stick to propane year round and thus save the expense of additional regulators/pigtails and having to store the extra bottles. If I am missing something could someone please explain
Hello Graham, There is nothing wrong in sticking to Propane. Depending on where and how you buy it, it may work out a little more expensive, but equally it might be cheaper. The only down side to propane is in hot climates where there may be an issue with bottles getting too hot. (Calor do not recommend using Propane where the bottles can exceed 50C due to the increase in vapour pressure at elevated temperatures.
Thanks Prof John, you have confirmed my feelings that there is really no need for butane when caravanning in the UK and with bottles such as the Calor Lite lightweight bottles the weight saving alone makes a certain amount of sense.
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