"Davey" wrote in message
...
First, as an aside, what is the opposite of radiator (as in central
heating) - consumer, sink? Best I could think of was absorber.

To the point: I can't see any actual solutions to my problem, but it should
provoke some intereresting discussion, anyway.

It's been very hot here in the UK this past weekend and while lying awake in
the sweltering heat, trying and failing to get to sleep, I was wondering if
there was anything I could do to cool the house down. I started on how we
kept the house warm, and worked backwards.
---------
You're not far off the mark. The main difference is the method of heat exchange
employed.

With a UK central heating system you only have the heating element of an
environmental control system. You pump in energy, that's converted to a
distributed form of heat, water generally, and then piped around the premises to
larger heat exchangers (radiators), the water on return is now cooler than at
launch and gets reheated. Round and round it goes.

This is fine for your house, especially in England where the odd warm day or
sultry night is something to be remembered. Where both heating and cooling are
required regularly you need a few enhancements.


The obvious thing was the central
heating: could I pump cold water around that?
-------------
I'm sure you could.

Well the rads. were already
cold, so that wasn't doing much. So why does the heating work? Because the
rads get a lot hotter than the surroundings.
----------
That's right. They're not efficient but they are fine for your house. They
transfer their heat by 'absorbing' the cold in the environment. As they give up
their heat the water in them gets colder and the environment gets warmer. They
are useless at cooling in conventional form.

Could I pump very cold water
around the system? I couldn't see water even at 0 deg. having much effect,
so it would have to be well below 0 deg. to have any effect.
----------
No, typically you would want to circulate the water at 4 degrees Centigrade.

The obvious
problem - you can't cool water below 0 deg. C! How could I stop it freezing
up? Does the anti-corrosion additive have any anti-freeze properties?
Doubtful, as this isn't its purpose. Add antifreeze? That can take water
down to -20 deg. C, as I recall (if, of course, I could 'bulk cool' the
water down to that!). Now rads at -20 deg C might be nice on hot summer
nights...
------------
Might as well go the whole hog and circulate liquid nitrogen (just joking)

The cooling element of an environmental control system is not unlike that which
cools your fridge. Way bigger, but the same principal. So you 'could' rig one up
yourself. You have much of the system already installed. You just require a
cooler instead of/as well as a boiler and fan-coil units instead of radiators.
Fan-coil units could be made from old car radiators (this time they would be
working in reverse) with a fan behind them. ( The idea being that you want to
blow air across as many elements as practical to exchange energy, in this case -
blowing warm, environmental, air across cold vanes. The air sucked in by the fan
will be at ambient. the air after passing through the radiator will be markedly
cooler ) The cooling unit 'could' be contrived out of a few old fridge bits but
you would need to allow for venting the heat they will generate, (heat doesn't
disappear it just gets moved around.), this requires more energy.

The idea would be to push the cold water through the 'car radiators', the fan
blowing across the elements would enhance the otherwise crummy heat exchange and
away you go. The return water would be cooler than at launch and so would
require cooling again. Round and round you go.

But it all takes energy. Which we have to pay for. So, to be warm, or cool,
comes at a cost. But I reckon one could make such a set-up if really desired.