Reply To: Porta's Derivation of Lempor Theory

[Chris Corney]

My usual approach with a very inefficient device such as this is to try and identify the losses and then see if there is anything that can be done to reduce them. Obviously it’s necessary to stay within the loading gauge and – these days – limitations imposed by the heritage appearance.
Presumably the kinetic energy of the gases leaving the chimney is included in the losses, but there is not much that can be done about this.
Other losses that spring to mind are
– mixing losses due to steam and smokebox gases at different velocities.
– supersonic shock losses
– internal friction.
– losses due to pulsation effects (as previously discussed, there is not much knowledge about this)
As you can tell from previous discussions I’ve been trying to understand how a Kylchap works. The double Kylchap successfully draughts the boiler but with a much larger orifice area, and lower back pressure than the single chimney it replaced, so there must be something beneficial going on there!

Chris