Wednesday, 3 March 2010
Steam heating 1.0
Our new (third hand) boiler is almost ready to go: all associated tanks, vents, flues and drains are done and there remains only a few yards (these pipe fitters are old school) of return mains to pipe in. We'll be testing the lot later today.
In the past we've used vessels with great big electrical elements in them to heat brewing water and boil the wort, but we're on a different scale now and there are more efficient ways available to us. High pressure steam, costly on installation - cheap to run, gives excellent light touch control and a wonderfully clean heat transfer through stainless steel coils, eliminating burnt or caramel flavours that can otherwise arise from this area.
The boiler delivers steam at about 80 psi (15 is atmospheric pressure) and 160 degrees Celsius through an inch and a quarter diameter 'black iron' (steel) pipe to a 2 inch diameter stainless steel coil (total length 5 meters - apologies for mixing my units: I'm quite comfortable doing it, I hope you are reading it). It's here that the steam gives up its heat (well, energetic enthalpy really, 2000 kJ/kg) to the wort, subsequently condensing, whereupon it's forced through a funky gate (the steam trap) to a three quarter inch return main, at atmospheric pressure, returning to the boiler for a repeat performance.
Thermodynamics is the subject - this time it's practical so I may just, finally, get it.
We haven't named the boiler yet - feel free to make any suggestions. The lucky winner gets to have their photo taken next to the big fellow.