In article ,
john t west writes:
Looking at how some people are protecting their Green Houses against the
frost, i was surprised how tiny the flames were on the paraffin heaters
in the green houses. They were hardly giving off any heat at all.

I was told its not about the 'Heat', but the fact that the flame changes
the 'relative humidity' in the air'.

Could anyone explain fairly simply, how this actually works? Thanks

In a slightly different context, someone I know has a large garage
they want to use for storage. As expected for an unheated detached
building, anything left in it gets damp and rusty, even though the
building is watertight and the building fabric itself isn't damp.

I have been running an experiment for over a month now, recording
the internal temperature and humidity, and the outside temperature
and humidity, to try and understand why things get damp in an
outbuilding. I have also added some heating, and what surprised me
was how little heating is required to reduce the relative humidity
inside the garage by quite a bit. I found it quite simple to control
a heater to limit the internal relative humidity to, say, 80%, but
I don't know if this is low enough to prevent timber and furnishings
getting to smell damp, or steel from rusting (or even if controlling
the max humidity is the right thing to do).

When I have more data and understand more of the relationships
between the various parameters, I'll write a blog on it.

The heater I use is a 1kW oil filled electric radiator (what I had
to hand), reduced to 500W by half-wave rectifying the supply to it.
I haven't analysed the figures in detail, but at a quick glance,
it's running with a 30% duty cycle when outdoor humidity is almost
100%RH, which is going to be around 150W equivalent. In comparison,
a gas pilot light is about 250W, and I'm guessing the parafin flame
is going to be in this same ball-park.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]