MikeAlmogy Posted March 3, 2020 Share Posted March 3, 2020 Hi all. Like the title said, how can I calculate the btu output of my self made burner? My working pressure is 10 psi, the burner gas orifice is 0.8. The gas is Butane, not propane. Thanks. Mike Quote Link to comment Share on other sites More sharing options...
Latticino Posted March 3, 2020 Share Posted March 3, 2020 No simple answer to your question of how to calculate effective heat output rate for your burner (BTU/hr is what you want, not simply btu). First you would need to figure how much gas will flow through the orifice at that pressure (how is your fluid mechanics?). Then you need to either assume stoichiometric combustion (unlikely) or figure how much air is actually induced by your burner and effectively used for combustion inside your forge (might require measurement of oxygen content and temperature of the flue gases - how is your inorganic chemistry and thermodynamics?). Then, knowing the heat content of the gas and quantity flowrate that is actually combusted effectively inside your forge you should be able to quantify the heat output of your burner. One way of looking at it is that a well designed burner/forge assembly very likely approaches 75-85% efficiency. Anything more and you need to figure a way to extract heat from your flue gasses, lowering them down to the condensing range. If you assume that you can measure the usage over time of your fuel (weigh before and after 1 hr of use) then use that, the average heat content of the fuel (I would use the lower heating value of butane: 19,620 BTU/lbm) and multiply by the efficiency (0.75) to get the projected useful heat output over time. Or you could just test it using known quantities (i.e. a BTU is the unit of measurement for the amount of heat it takes to raise 1 pound of water 1 degree F). Why do you want to know? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 3, 2020 Share Posted March 3, 2020 Most folks I know just use the gas consumption by weight per unit of time times the energy per weight to give a "ballpark BTU" for their systems. As I turn my burner up and down depending on what I'm doing and ambient conditions; a single value isn't very accurate for me. Quote Link to comment Share on other sites More sharing options...
MikeAlmogy Posted March 3, 2020 Author Share Posted March 3, 2020 Thanks :-) I do not know how to calculate the flow rate. The rest is more easy. But, after talking to Uri Hoffi, he told me just to do trial and error. It will probably be more efficient then all the calculations since, as you wrote, i have no idea if my burner run at maximum efficiency. Thanks :-) Mike Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 3, 2020 Share Posted March 3, 2020 Btu output has been seen to be less than relevant in designing gas forges. I Forrest fire has loads of heat output, but very little usefulness. Quote Link to comment Share on other sites More sharing options...
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