Opposite of radiators... and more

[Davey]

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. The obvious thing was the central heating: could I pump cold water around that? 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. 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. 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...

And a serious question: while thinking about adding antifreeze to the heating system, I recalled that in WWII, the piston-engined power plants in aircraft invaribly used (100%?) gycol (which I think is anti-freeze by any other name). What was the advantage of doing this? I can't see as the anti-freezing properties would be of any interest, so does gycol 'conduct' heat more efficiently than water or glycol-water mix? If it does, would running a domestic heating system with glycol instead of water make it more efficent?

Davey

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[Lee Blaver]

Not really related to your post, but browsing aircon units the other day, I noticed a split unit that used water as the link between the two units, rather than gas.

Actually sounded like a good idea :-)

Lee

[gandalf]

--------- 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.

------------- I'm sure you could.

---------- 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.

---------- No, typically you would want to circulate the water at 4 degrees Centigrade.

------------ 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.

[Andy Hall]

I saw a flyer for this in Plumbcenter recently

To email, substitute .nospam with .gl

[Ian Smeaton]

============================== Hi Davey, You'll need a drip-tray under every radiator! I've recently taken to chilling my lager glass in the freezer for a couple of hours before use. It's got condensation/frost on it before I get the freezer door shut!

Cheers,

Ian

[Ed Sirett]

There are several problems but by far and away the biggest is the amount of condensation (or even ice) that would form rapidly on the radiators.

However why get so into technology.

1)The average temperature (over 24hrs) even on the vey hottest days is only in the low 20s. So air the air at night try to keep the heat out during the day. Shutters are used in hot countries for this reason. 2) Humidity and air movement are far far more significant than temperature. 3) A low tech ceiling fan (big & slowish preferable) will make things much more confortable. 4) Cooling the air without removing the moisture will make things not much better if at all (I haven't followed the evaporative coolers thread but the idea of trading temp for humidity is dubious IMHO.

[Brian Reay]

A popular solution in the US (where not everyone has air conditioning) is a 'whole house fan'. This is a BIG fan, maybe 2' in diameter which is located in the upstairs ceiling and vents into the loft. In hot weather it draws air in downstairs and blows the hot air out via the loft, which is also cooled which, in turn, helps keep the house cooler.

Based on the cooling effect I get buy opening roof (velux) windows and a downstairs window this approach is worth trying.

I know that blowing warm (or hot) moist air into a cold loft is wrong but, in the summer, the loft isn't cold! Some cover would be required in the winter to prevent warm moist air getting into the loft and causing condensation.

Regards

Brian

[gandalf]

----------- Gophers apply a similar but more sophisticated technique. They ensure that entry/exit points to their underground home are at different heights. Any breeze causes an air circulation within the tunnel system and both cools and purges it. Pretty cunning for something that is supposed to be dumb. Humans also latched on to this trick in the days before air-conditioning. Hence the small towers on Arab houses. I'm sure many throughout Asia also applied this.

[IMM]

Georgian windows are supposed to go right up to ceiling height. Pull upper sash down and lower one up and instant circulation with the hot risen air floating outside and the cooler air dropping in via the bottom sash. Great design.

[IMM]

High insulation helps a lot. It keeps heat out as well as in. Roof overhangs to the correct length to shade the summer sun and allow in winter sun. A slow moving fan is fine for most cases with high insulation. Heat recovery is fine by taking in outside air from under vegetation. Quite effective too. No need for chillers, compressors, etc.

Heat pumps heating a battery in a duct can reverse. So cooling by default, but it still cost to run, but the extracted heat may be stored in the earth to be extracted in winter. It moves heat. The "overall" cost may be economical enough.

[Woodspoiler]

I once owned a house where my bedroom got insanely hot in summer. I had one of those small air fresheners which is basically a fan sucking air up through the base where there is a perfumed filter.

I chopped the legs and filter assembly off bottom of the freshener, leaving a fan mounted in a plastic cylinder.

I cut a hole in the bedroom ceiling, slightly smaller than unit, and mounted the unit above it in the loft. This was sealed to the upper surface of the plaster board with filler foam all round the outside. The internal switch was run out to a ceiling pull switch. I powered it from the lighting circuit - a bit naughty, but I didn't know any better in those days and it was a very low-power device anyway so no harm done.

I would run this all day in hot weather, venting air into the loft to combat heat build up, and all night too of course.

The fan was very quiet - you could barely tell it was on.

This system was extremely effective.

For the internal face of the ceiling I adpated a car speaker grille to provide a good cosmetic appearance. It collected dust and needed brushing off now and again - v. important, or the fan motor might start to fry eventually with the obvious fire risk.

In the winter I fitted a cover over the grille to prevent hot air escaping.

W.

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coming hot day.

to get

then a

might be an

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hotter days

of seasoned timber! ;O)

[Richard Caley]

e> ISTR that "radiator" in the wrong term.anyway Space heater would I think be e> more acurate. Something to do with radiating in vacuums.

IIRC most of the heating from a CH radiator comes from convection rather then radiation (compare holding your hand a foot in front with holding it a foot above the radiator).

Randomly prompted question for CH bods: I have recently moved my couch to be in front of the radiator. Should Ithink of moving it somewhere else for the winter? I presume I will heat the back of the couch, which I don't think woll be a problem per-se, and heat being heat it will just leak out into the room, but maybe it will make the room warm up so much slower that it will be a real problem.

[IMM]

You could have the fan on the inside of a hatch door and a grill the other side. This can hinge up and be fixed in place when not used. Then have another "sealed" hatch door on the other side of the hatch and swing this down for winter use. The best is a permanent fan in the loft and a grill with an auto sealed damper in the ceiling at the top of the stairs. the two are connected via ductwork.

[Davey]

It was - at least partially - a tongue in cheek posting. Just my musings about the problem of being too hot whilst trying to get to sleep. But it has generated some interesting postings!

But, as yet, no one has answered my one serious question: why did WWII planes use neat glycol as coolant, and what would the effects of using this in a domestic heating system be. Apart from finding all the leaks, perhaps. Perhaps I should post in alt.history.wwii.aeronauticalengineering (or something)?!

Davey

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[parish]

Because it has a higher specific heat capacity than water or water/anit-freeze and meant they could use smaller radiators.

in a domestic heating system be. Apart from finding all the leaks, perhaps.

[Terry]

Interesting thread all round:

Maybe a water bed with ice in it????? Condensation could be contained by the liner? One might wake rather damp in the morning though?

I've always claimed "that the climate here is similar but colder than the UK" But even at the same latitude as Spain, on this side of the Atlantic though, it is on average colder and being adjacent to the North Atlantic, well moderated so that while it doesn't get as cold as central North America it can be cold and foggy in the summer!

Well; yesterday we finally got some warm weather here (eastern Canada) about time too, mid July!

It got up to a somewhat humid 26 Celsius which we find hot. I can just hear our Florida friends snicker and say "Call that hot"? That's their winter temperature! Last night it cooled right down, the advantage of being on the coast so that even with the annual crop of icebergs all drifted away to melt in the Gulf Stream it was comfortable for sleeping. Later I had to close the window it got quite chilly.

Two things; Vent the roof;

1) Our roof is already well vented but today I must remember to get the ladder and open the 'big' vent in the gable end of the roof to vent hot air (sometimes we also install a temporary fan mounted on a piece of plywood) if this weather continues. Must also put in the temporary 'fly screen' we had a wasps nest in there one year! Use basement (if available); 2) Our approx. 1500 sq. foot by 8 foot high, in ground concrete basement stays cool at about ground temperature, plus other losses and gains; roughly at 55 deg. F in winter and approximately 60 deg. F in summer. So it is possible to close up the house tight early on a hot day and circulate the upstairs warm and basement cool air with temporary fans to attain some degree of comfort. This has worked for several hours until say around 4.00 PM. Between then and sunset though it gets rather warm and one would like to be able to go in and out of an evening. One problem though can be the basement gets damp with warm humid upstairs and outside air getting to dew point down there; so some days later, on a dry day, one 'airs out' the basement thoroughly. We also use a small dehumidifier in a 9 foot by 11 foot electronics workshop down there if required. When we lived in Liverpool, big old house turned into flats, a basement work/storage area was available. On an occasional hot night it was just as well to go down there into the cool and do some d-i-y in the workshop, rather than toss and turn in the heat upstairs! If necessary the basement is a great place to sleep!

[al]

The opposite to a radiator in this form would be a similar device mounted close to the ceiling with something substantially colder pumped through it (say a liquid with a low freezing point kept at -20C). Then convection would do the opposite of what the radiator does in that the cool would "fall" as opposed to the heat "rising". Problem is, the moisture in the air would just ice up the metal and make a mess!! If you had a low (1C for example) water based system, it would just condensate all over the place so that's not a goer either!

Some old "air conditioning" systems do just use cold water pipes and a fan to blow air over them, thus slightly cooling the air which is accelerated around the room by the fan. A bit too subtle for my liking though! The fact is, hot objects near floor level put high energy into the cold air around them and send it with gusto up to the roof - this heats a room very effectively if the volume of air is not too great. A cold system would be too subtle without pumping the hot air past a refrigerant and blowing it out aggressively through the room.

Trust me, the forced convection of an air conditioner will serve you better ;o)

a

[geoff]

In message , Davey writes

They probably only used glycol after Italy surrendered and there was plenty of Italian wine about

[parish]

I thought that was Austrian wine?

[Gnube]

Rascal ;O)

Take Care, Gnube I don't want to win the lottery I just want to win a barn full of seasoned timber! ;O)