[Les]

Originally Posted by lolito_fr

Not for a passive radiator. Check this:
http://www.coolingzone.com/Content/D...las/fcalc3.htm

Have played with and initially found to be a distraction.
However a 120x120x50mm heat-exchanger with a temp differential of ~25c gives a fin spacing ~6.5 mm and h(not Q) ~ 11W/m^2*K.
OK 25c is too large for dT(fin-air) but not too large for dT(air out -air in) IF the heat-exchanger is positioned beneath a household radiator(25++c on mine(thermometer only up to 50c).


Edit1 : Corrected "optimum fin spacing" to 6.5mm(from 4mm)
Edit2 : Corrected h to 11 from 30