LPG gas conversion

[bibacux2001]

I have bulk gas delivered and I am trying to work out how to convert litres of liqid petrol gas ie LPG in its liquid form into meters cubed of gas. IE if I had one litre of LPG liquid and let it expand into a gas what volume would the gas be in meters cubed. Any help or direction would be appreciated. thanks

[brachiopod]

1L of LPG = Whatever-sized-container-you-decide-to-put-it-in cm� of Petroleum Gas.

In other words, a gas expands to fill a (rigid) vessel completely.

LPG is only a liquid because it is under pressure. Release the pressure and it will turn to gas. The liquid in a cigarette lighter is usually butane (technically an LPG) - when you press the valve, a small stream of liquid butane turns to gaseous butane as it decompresses - (the flint ignites it at the same time to create a flame.)

If you allowed a liquified gas to expand into a non-rigid vessel (eg. a balloon), the liquid would turn into a gas and expand until the pressure exerted by the gas equals the contracting pressure exerted by the elastic skin of the balloon. This volume you can measure - however, it varies with temperature......For example, a ballon of a fixed volume of gas will have, say, a volume of 1L (1000cm�) at 21�C, but will be less for the same mass of gas at 2�C (in other words, the gas contracts at lower temperatures, assuming the pressure remains the same.

If you Google 'Charles' Law' and 'Boyles Law' you will hopefully see the relationship between volume, pressure and temperature of gases - and if you are feeling adventurous - try 'saturated vapour pressure' to see the effect of gas/liquid phase systems.

[bibacux2001]

Ok thanks for that however if a gas meter is inserted within an lpg gas circuit surely the gas is contained within the pipe. so a meter must be able to measure how much a full tank equals in meters cubed. I will look at Charles law as I remember using this in hydraulics at uni and maybe i can work out somthing from diameter of pipe.

[brachiopod]

I see what you mean now, bibacux, you need to find out what pressure your LPG system works under, I'm sure it will be a standard pressure.

I'll have a Google later and see what I can find out..

[lebesset]

I understand your question but why do you want to know ?

the bulk gas you buy is largely propane , some butane , and maybe 10% other lp gases , not very combustible

if what you are trying to do is work out a relative cost the easiest way is to convert everything to KwH as these figures are easy to obtain

and your bulk gas will give you around 7KwH/litre

I don't know if britain has yet arrived in the 21st century , but in most countries piped town gas supplies are now sold by th KwH

[stanleyman]

If you are trying to get a cost comparison for lpg then even knowing the equivalent in gas volume to town gas is not going to help because they have a different calorific value. It also bares no relation to oil per litre.

I used to work this out for heating systems when oil was much cheaper. Oil was cheapest, then town gas, solid fuel, electricity and LPG by twice as much as oil.

I would guess that the order now is town gas, solid fuel, oil, electricity and LPG probably by a considerable amount as it is related to oil prices unless demand is low.