How do you convert a volume of hot gas to btu?

Answer 1

There is no direct conversion because it depends on the gas. A BTU is a unit of energy (a "British thermal unit") and how much energy a certain volume of gas has depends on the identity of the gas. A liter of gaseous oxygen will have a different amount of energy in it than a liter of hydrogen gas.

Also, it depends on the temperature and pressure of the "hot gas." Because of the Ideal Gas Law (see Related Questions links), the amount of gas in the same volume goes down the hotter the gas. If you know the temperature and pressure, it is easy to find how much gas you have in a certain volume.

Then, to convert that to BTU, you need to know the energy content of that specific gas. That you need to look up in a table somewhere...

Agree with JEK above.

The short answer: It depends on the type of gas, and whether the gas is hot or cold changes the density of the gas. So standard atmospheric temperature and pressure should be taken into consideration The long answer: To convert a volume of any gas into a unit of energy, you have to know what kind of gas it is first. The Btu content of a gas is determined by the percentages of its component gas. The higher the Btu rating of the gas, the more energy it contains per cubic foot or volume of that gas. Take Natural Gas for example. NG is a mixture of several different gasses, mostly methane. This being the case, no two wells that produce NG have the same energy content. There is no true standard of energy content (or calorific value) for NG. For rough estimates an average value can be used: it is roughly 1000 Btu/ft^3. A standard heating value for domestic and commercial NG delivery is 950 Btu/scf (scf=standard cubic feet). There are references on the Btu content of specific gases. There are also conversions. Hope the links provided help a bit. Reference books are your best bet.