BTU Charts
(See Description Below)
The calculations used to produce these charts attempt to model the critical dimensions of the type of gas jet used in the HybridBurner design and the net heat output. Unlike other calculations they also model the air induction capability of the jets to get a rating of the efficiency of the burner.
The following are links to pdf files that provide the charts plus
numerical tables with burner output, fuel usage and more. (US and SI units).
Shorty Burner
TRex Burner
1" Diameter Burner
1.25" Diameter Burner
For special applications these alternate tip configurations have been tested.
Shorty w/23 Burner  lower output  extra efficiency
1" Diameter w/52 Burner  higher max output  extra reducing atmosphere
About the Tables  "pdf" format
Theoretical Burner BTU Output
Charts
The calculations used to produce these charts attempt to model the critical dimensions of the type of gas jet used in the HybridBurner design and the net heat output. Unlike other calculations they also model the air induction capability of the jets to get a rating of the efficiency of the burner.
These charts provide the theoretical heating value of the propane used
by four of the five Burners I offer. The graphs are a result of calculation
rather than actual measurement, so are theoretical. The calculations use some
approximations but are based on methods believed to be reasonably accurate.
The BTU/Hr value given is "net", meaning it excludes the heat of vaporization
of the water in the products of combustion. Environmental conditions, variations in the temperature of the fuel gas, the specific
composition of the fuel gas actually used, manufacturing tolerances of the burners,
and other factors that can affect the actual output available to perform work.
The energy used to heat the air needed for combustion is also not accounted
for. So the values charted are assuming ideal conditions and a 100% conversion
of fuel to heat energy. Actual output values would be less than shown. However the BTU/hr ratings can allow comparisons between, for example 2 shorty burners running at 20 PSI vs 2 TRex burners running at 5 PSI.
The charts here are upgraded from those on the site previously, These include an extra line labeled "adjust for air" this accounts for the fuel gas that is not burned using the air entrained by the gas jet. Theoretically this represents loss from perect eficiency, however, for almost all applications a slight reducing atmosphere is desirable because it reduces scale formation. Note also that the efficiency falls off in the "sonic flow" region. this is because the speed of the gas jet is capped by the speed of sound and as such the air/fuel ratio falls off.
The net heating value
of propane used is 19,944 BTU/Lb. This comes from Marks' Standard Handbook
For Mechanical Engineers, 10th Ed., McGraw Hill, 1996. Other sources have
slightly different values. The computation is based on the methods for adiabatic
frictional flow from "Compressible Fluid Flow", 2nd Ed., Michel A. Saad, Prentice
Hall, 1993 and "Combustion", 3rd Ed, Irvin Glassman, Academic Press, 1996. Plus other sources. The physical characteristics of propane are
from the National Institute of Science and Technology WebBook
(http://webbook.nist.gov/cgi/cbook.cgi?ID=74986).
Please feel
free to validate these results  weigh a propane tank on an accurate scale  run the burner for a convenient period of time
at a known pressure  then reweigh the tank. This of course does not take into
account any of the various modifying factors discussed above.
If you wish to do your own calculations an easier model to work with is available on Ron Reil's Forge
and Burner Design Page as the "BTU
Output Calculator". (A 'zipped' copy for download is HERE.) This will provide a close approximation of the output
of each burner at a specified operating pressure.You will need to enter the
jet diameter, and your intended operating pressure into the calculator to obtain
the BTU output. Because the output varies with changes in operating pressure,
and each burner can operate over a broad range of input gas pressures. Note that
these jet tips are TWECO contact tips used in MIG welders, and will measure
slightly larger than the quoted size below, perhaps 7 to 9 thousandths greater than the nominal wire diameter.
The charts and tables
were created by Paul Boulay. We are very indebted to Paul for the time and effort he put into producing this data and making it available to
the public.If you have any questions please feel
free to contact Paul or me. Paul's Email address
is pboulay <at> earthlink <dot> net
(Click icon to email me)
