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Somewhat involved, but economic passive radiator idea

793 Views 16 Replies 9 Participants Last post by  CyberDruid
I've been trying to think of an effective and economic way of taking the heat out of a watercooling system with little or no noise, and today I came up with the following idea. It would take a bit of work and to be honest is a little over the top, i'm not sure i would bother with it but i thought i would share it anyway.

I dont know about you guys in the states, but over here in the uk our hot water supply works as follows. Cold water direct from the ground piping is pumped into a water tank which is usually in the loft. A seperate hot water tank is then usually situated somewhere below it (usually in an 'airing cupboard'). The hot tank is then heated by a coil fed from the central heating supply.

What i'm suggesting is a third tank situated between the two. A coil fed from the watercooling setup could be submerged in this tank, cooling the watercooling feed to what is usually very cold temperatures here in the uk. Whenever a hot tap is turned on, the hot water tank would be refilled not from the cold tank but from the watercooling tank, which would in turn refill from the cold tank. Since the hot water (in my house anyway) is used quite frequently, the watercooling tank would be continually flushed and filled with cold water. This should keep the water in the coil down to a reasonably low temperature (i would guess 10 degrees at the most... all year round the cold water supply in this part of the world is very cold).

Although this setup is somewhat involved, and none portable, it does have its advantages. Firstly no more water would be wasted than normal. Secondly most of the heat generated by the cooled computer would simply be fed into the hot water supply, while the savings in pre-heating the hot water in this way would be minimal its economical value cannot be ignored. Thirdly one doesn't have to worry so much about the head height of sending a watercooling feed up into the loft, since the only 'true' height the pump is working the water through is the difference between the down pipe and the up pipe, everything else is just the length of the flow.

If i did this myself i would probably just fit two small taps in the wall of my computer room, and connect these to whatever cooling blocks i have. I've drawn a little image to illustrate what i mean, forgive its crudity i threw it up in a few minutes.

You might think im crazy, but this is a truely economical and silent cooling solution. The only energy wasted is that of the pump (and any heat lost in the pipes).

Anyway, thought i'd share...


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· SNERP!!!
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Originally Posted by confusi0n

Yeah that was the idea... the refilling and flushing would all be automatic... the problem is this...

Unless my calculations are incorrect, for the temperature to remain stable in a 30 gallon tank the water would need to be almost completely flushed (and refilled) every two hours. Thats a hell of a lot of water. Sure it would take like a day for the water to heat to room temperature, but that heating would not stop, and unless about 100 litres of water is expunged from the watercooling tank every two hours it just wont stabalise.

Its possible i've calculated it wrong. If specific heat capacity is measured in J/kg degree then i've just taken a water temp of 20 degrees, and 120 litres volume, worked out its energy (120 * 4190 * 20, where 4190 is the heat capacity of water)... then i've taken away the energy of 10 litres at 20 degrees and added the energy of 10 litres at 10 degrees... the result would be the energy of the tank after flushing 10 litres and refilling with the cold water... i've then converted this into degrees.

In order to get a change of negative 1 degree every two hours (to counter the heating i mentioned in my previous reply) i think i would need to be using about 100 litres of how water every two hours. Is this wrong?

The other alternative is to leave the water heating continually until somebody takes a bath, and most of the water is drained... it would then take a long time for the water to heat up again... i'm not so sure of this though...

I need to think about it more, at the moment its not looking too good though. I wonder what difference connecting the cooling tank to the feed for the toilet cisterns aswell would make? Oh well, good food for thought.


The problem I see with this is you will have mineral buildup in your blocks. It also seems like if any of your calcs are a little off you could end up with a dead CPU or wasting a lot of water or money on this.

I do however like the idea. If the water stays as cold as you say year around you could put a res of distilled water in your cold water tank. That way the cold water would be circulated more because it will be tied into everything in your house and you wouldn't have to worry about the mineral build up.
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