I've always considered the charge for refilling a 8.5KG gas cylinder to be a bit extreme considering the cost per litre for cars on LPG - I figured if 8.5KG of LPG in the cylinder cost $20 how come I can buy about 25 litres of gas for a LPG car for the same price. My thinking was based on my mistaken belief that like water, LPG was about the same weight per litre + 1 litre = 1 KG.
Then I found the following in the Elgas site:
Unlike water, 1 kilogram of LPG does NOT equal 1 litre of liquid LPG.
LPG density or specific gravity is about half that of water, at 0.51.
In Australia, where LPG is propane, 1kg of LPG has a volume of 1.96L.
Conversely, 1L of LPG weighs 0.51kg.
Now I figure it's not so bad as I'm getting almost twice the litre amount for my money. (yes, I'm easily fooled)
Good Luck.
Lancelot Link said
12:22 AM Sep 16, 2017
but then we have Boyles law:
(P1*V1)/T1=(P2*V2)/T2
Which says, if I remember my chemistry right, Volume depends on temperature and is related to pressure. So if in Darwin in summer versus Melbourne in winter, you will get less gas in Darwin at a higher pressure than in Melbourne with cold temperatures which will give you more gas at the same pressure! But if you buy in Melbourne and take it to Darwin in summer, you will end up with more pressure for the same volume!
RustyD said
08:50 AM Sep 16, 2017
Same Boyles Law works for tyre pressure. Never really thought of how much difference pumping a tyre up in zero degrees (273K) vs 40 degrees (313K).
daffyfrancis said
11:44 AM Sep 16, 2017
Like Hako I am easily fooled but would not 1kg by weight of gas be the same no matter what the pressure?
David
Aus-Kiwi said
11:51 AM Sep 16, 2017
Once it liquide ! That's it !
PeterD said
12:01 PM Sep 16, 2017
Boyles law has nothing to do with temperature. That's Charles's law. When using Charle's law remember the temperature scale to use is the Kelvin scale.
The ambient temperature between places in Oz does changes very little as a percentage of the temperatures we are working at. That means there is very little change in volume, probably not worth worrying about. It also has nothing to do with the amount of liquid in the bottle. To analyse the situation fully you need to use the ClausiusClapeyron relation. For a simple relationship you can use the equilibrium vapour pressure.
Again you need to use the Kelvin scale when working with the coefficient of expansion of the liquid in the bottle. Again the percentage change of temperature is so little that I would not be too worried about the change of volume with the change of temperature.
I've always considered the charge for refilling a 8.5KG gas cylinder to be a bit extreme considering the cost per litre for cars on LPG - I figured if 8.5KG of LPG in the cylinder cost $20 how come I can buy about 25 litres of gas for a LPG car for the same price. My thinking was based on my mistaken belief that like water, LPG was about the same weight per litre + 1 litre = 1 KG.
Then I found the following in the Elgas site:
Unlike water, 1 kilogram of LPG does NOT equal 1 litre of liquid LPG.
LPG density or specific gravity is about half that of water, at 0.51.
In Australia, where LPG is propane, 1kg of LPG has a volume of 1.96L.
Conversely, 1L of LPG weighs 0.51kg.
Now I figure it's not so bad as I'm getting almost twice the litre amount for my money. (yes, I'm easily fooled)
Good Luck.
(P1*V1)/T1=(P2*V2)/T2
Which says, if I remember my chemistry right, Volume depends on temperature and is related to pressure. So if in Darwin in summer versus Melbourne in winter, you will get less gas in Darwin at a higher pressure than in Melbourne with cold temperatures which will give you more gas at the same pressure! But if you buy in Melbourne and take it to Darwin in summer, you will end up with more pressure for the same volume!
Like Hako I am easily fooled but would not 1kg by weight of gas be the same no matter what the pressure?
David
Boyles law has nothing to do with temperature. That's Charles's law. When using Charle's law remember the temperature scale to use is the Kelvin scale.
The ambient temperature between places in Oz does changes very little as a percentage of the temperatures we are working at. That means there is very little change in volume, probably not worth worrying about. It also has nothing to do with the amount of liquid in the bottle. To analyse the situation fully you need to use the ClausiusClapeyron relation. For a simple relationship you can use the equilibrium vapour pressure.
Again you need to use the Kelvin scale when working with the coefficient of expansion of the liquid in the bottle. Again the percentage change of temperature is so little that I would not be too worried about the change of volume with the change of temperature.