Ground heat pumps. How does this heat exchanging work, then?
Ground heat pumps. How does this heat exchanging work, then?
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Discussion

BB-Q

Original Poster:

1,697 posts

239 months

Monday 29th December 2008
quotequote all
Seems really interesting to me but can't get my head round it. Bit like when a friend of mine invented a steam powered fridge to hold the beers on hid steam powered boat.

Edumacate me please?

Graham E

13,018 posts

215 months

Monday 29th December 2008
quotequote all
The steam powered fridge I can explain, but the ground heat pump baffles me completely!

Any eggheads out there would make me a happy man if they could explain this "put a couple of tubes out in the cold and your house gets warm" skullduggery works.

i think it's voodoo

V8mate

45,899 posts

218 months

Monday 29th December 2008
quotequote all
It's hot at the centre of the earth.

HTH

TheEnd

15,370 posts

217 months

Monday 29th December 2008
quotequote all
they work like a fridge trying to cool the planet, so end up getting hot

fido

18,873 posts

284 months

Monday 29th December 2008
quotequote all
It's basically the opposite of a fridge except, instead of taking heat from the inside of your fridge it takes heat from the ground [which even a few metres down is always 10C or thereabouts], and the hot fins at the back of the fridge are used to heat water in your central heating.

pacey_sot

246 posts

224 months

Monday 29th December 2008
quotequote all
Yep, i found it best to imagine it as air con in reverse - instead of the hot bit outside and cold inside it's reversed

BB-Q

Original Poster:

1,697 posts

239 months

Monday 29th December 2008
quotequote all
Brilliant- but how does a fridge work? weeping

Olf

11,978 posts

247 months

nottyash

4,671 posts

224 months

Monday 29th December 2008
quotequote all
From what I understand they work in reverse of the fridge principle but require a large area to heat exchange.

I know refrigerant is heated by a compressor. this heats it by compresion and sends it to the condenser as a gas. (A condenser usually uses air or seawater to cool it to a liquid) this changes it to a liquid by cooling it then it goes to a liquid reciever, where its held for going through a TCV (Thermostatic regulating valve) and through the fridge room via an evaperatoer (Heat exchanger) this then goes back to the compresser, and around again..

I dont understand the opposite bit though....may be magic.

lost in espace

6,586 posts

236 months

Monday 29th December 2008
quotequote all
The ground is heated by the sun. You remove the heat and use it in your house. This heat can get used up if you have the wrong ground conditions. Air source heat pumps are becoming fashionable.

Graham E

13,018 posts

215 months

Monday 29th December 2008
quotequote all
Thermodynamics mate - expanding gas / evaporation is endothermic (cooling)

Therefore, in a fridge, there is a closed system of refrigerant, that is compressed mechanically via a capiliary tube, then allowed to epand into the cooled area in the fridge. The bit at the back of the fridge (compressor area) gets hot, and the area inside the fridge wall (expansion chamber) gets cool. I beleive your steam powered fridge simply uses the steam to run the compressor, rather than an electric motor. The rest of the principle is the same.

B17NNS

18,506 posts

276 months

Monday 29th December 2008
quotequote all
I think the temperature of the ground at a metre or so depth is pretty much constant so even if the air above is freezing the ground is still say 10 degrees or whatever it is.

Therefore the liquid pumped through the buried pipes is warmed to at least that temperature. Therefore the boiler doesn't have to heat it as much. Therefore using less gas?

Might be completely wrong but thats what I've always assumed.

nottyash

4,671 posts

224 months

Monday 29th December 2008
quotequote all
B17NNS said:
I think the temperature of the ground at a metre or so depth is pretty much constant so even if the air above is freezing the ground is still say 10 degrees or whatever it is.

Therefore the liquid pumped through the buried pipes is warmed to at least that temperature. Therefore the boiler doesn't have to heat it as much. Therefore using less gas?

Might be completely wrong but thats what I've always assumed.
Ive heard it is deep in the ground, Maybe this is it?

cheshire_cat

260 posts

214 months

Monday 29th December 2008
quotequote all
From what I gather, water is pumped down a closed loop of pipe and given sufficient 'coils' in the pipe, the water is kept at whatever temperature the depth of the bore hole you drill is.

This water is passed through one side of a heat exchanger (metal fins, large surface area) with your central heating loop hooked up to the other. Although you will obviously never get hot temperatures with this soley, it will provide sufficient ambient heating, and also cooling.

BigBen

12,155 posts

259 months

Monday 29th December 2008
quotequote all
BB-Q said:
Brilliant- but how does a fridge work? weeping
What I can never understand is my oven is hot but my fridge is cold yet both are powered by electricity.

TheEnd

15,370 posts

217 months

Monday 29th December 2008
quotequote all
cheshire_cat said:
From what I gather, water is pumped down a closed loop of pipe and given sufficient 'coils' in the pipe, the water is kept at whatever temperature the depth of the bore hole you drill is.

This water is passed through one side of a heat exchanger (metal fins, large surface area) with your central heating loop hooked up to the other. Although you will obviously never get hot temperatures with this soley, it will provide sufficient ambient heating, and also cooling.
That's geothermal heating, and they use that in iceland (near the Findus crispy pancakes)

True geothermal uses hot groundwater, and this goes straight into a house and is decently warm.

The ground pump takes lots of cool liquid, and pumps it into the marginally warmer ground, and uses that 1-2' of heating of larger amounts of liquids to warm a small amount by more.

A fridge takes the heat out of the inside, and dumps it out the back, this works in reverse, so it's like putting a fridge in a doorway so the outside get cooler, and inside the house gets warmer.

nottyash

4,671 posts

224 months

Monday 29th December 2008
quotequote all
BigBen said:
BB-Q said:
Brilliant- but how does a fridge work? weeping
What I can never understand is my oven is hot but my fridge is cold yet both are powered by electricity.
My explanation above is how a fridge works.
4 main components Compresser, Condenser, TCV, and evaperator.

whitechief

4,432 posts

224 months

Tuesday 30th December 2008
quotequote all
Don't they just use the inherent heat in the ground to bring the water in your heating cycle up to a given temperature, therefore saving you the extra energy to bring it to that temp'?

BigBen

12,155 posts

259 months

Tuesday 30th December 2008
quotequote all
nottyash said:
BigBen said:
BB-Q said:
Brilliant- but how does a fridge work? weeping
What I can never understand is my oven is hot but my fridge is cold yet both are powered by electricity.
My explanation above is how a fridge works.
4 main components Compresser, Condenser, TCV, and evaperator.
Is it because electricity is made of positive and negative particles which are hot and cold respectively ?

cuneus

5,963 posts

271 months

Tuesday 30th December 2008
quotequote all
lost in espace said:
Air source heat pumps are becoming fashionable.
I find that interesting - can you qualify that ?