BANGasman wrote
Simplest explanation I have seen is in viper book
Yep and it tells you to multiply by three on a 3 section layout.
Not quite, it says to multiply by 3 for a 0.33 mbar drop in THIS example.
The times 3 is a simplification used for instruction that must be understandable for beginners.
To make things easy, the author assumes an equal pressure loss over 3 sections, with the largest requirement at the end of the main pipe, and the 3 sections fairly similar in length, 4m, 5m, and 4m on the main pipe, and the discharge split at approximately 30%, 30%, and 40%.
Personally, I would hope that experienced engineers do not need simplifications anymore.
Before you jump at the opportunity, based on my own observations in the field, I hope in vein and I have considered the 4% for the little fire negligible.
Back to the op.
That leaves here 13 meters to the boiler at 54 kW, followed by 4 more meters at 22 kW.
Rounding things off that means 5 m3 over the first 13 meters and 2 m3 over the last 4 meters.
If you would follow the same simplification, you would allow 0.5 over the first 13 meters and another for the last 4 meters.
You would then double the discharge from the bsen 1057 table to correct from 1 mbar to 0.5 mbar.
That would bring the need for 35 mm on the first section, and 15 mm for the second section
However, the same table reads discharge of 5.2 m3 at a length of 25 metres using 28 mm.
That would mean you can run the first segment in 28 and the second in 22, the little bit to the boiler from the main pipe also in 22, and find less than 1mbar drop at either appliance.
In this case, the simplification would distort the picture completely.
I know you are reading this Chris, am I far wrong?
