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Author Topic: (Updated w/ pics) Watercooled Rack of Servers - 50% completed  (Read 9841 times)
DeathAndTaxes
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Gerald Davis


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May 01, 2012, 04:19:15 AM
 #81

I don't see why that idea would be expensive though. It seems like something that could be done for $20, and perform as well or better than a large plate exchanger. The biggest downside is the floor space and low SAF.

I doubt you are going to find everything for $20.  Copper loops large enough to have any significant heat transfer aren't going to be cheap.  Still even if it was free this is the water my family drinks.   Not sure I want to be hooking up some salvage hot water heater of unknown origin or quality.

I fully concede that a flat plate exchange on the cold water inlet doesn't recovery 100% of theoretical energy but is does recover a good portion, is cheap and simple and doesn't require potentially contaminating the water supply.

If I went the storage tank w/ heat exchanger route I would look for something like this:
https://www.signalmarine.com/p-51907-atwood-eh-20-electric-water-heater-wheat-exchanger-20gal-110v.aspx

If someone made something like this without the backup electrical heat it likely would be cheaper.
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May 01, 2012, 04:26:02 AM
 #82

You could always do some kind of radiant floor heat in the winter...just a thought...
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May 01, 2012, 04:51:30 AM
 #83

I don't see why that idea would be expensive though. It seems like something that could be done for $20, and perform as well or better than a large plate exchanger. The biggest downside is the floor space and low SAF.

Copper loops, finding a hot water heater in decent shape, rigging up some water tight seals.  I mean remember this isn't a science experiment.  It is the water my family drinks.  It doesn't seem worth it.  Like I said it would provide marginally more recovered energy but hacking around with drinking water isn't my idea of a good ROI%.  I also don't think you are going to find all the parts, supplies, connectors, and tools for $20 but even if it is was $0.00 I don't think messing around with drinking water is a good idea.

I think you are missing the point on the amount of water.  2 ft, 20ft, 20,000ft it doesn't really matter how much energy is in the loop.  We aren't storing it for on demand use.  That energy will be dumped out of the loop at the same rate regardless of how big the loop is.

Your points are valid, it would be significantly more work to ensure it was built well and safe. As for the amount of water, to efficiently transfer the heat you need a large amount of surface area. To have a large surface area without excessive restriction, you'd need a large volume. That requires more water with more stored energy.

I'd actually be very interested in your calculations for the plate heat exchanger you looked at, and what the stats are for your system in terms of flow rate and head pressure, temperatures and such. With 6kW, you have a lot of leeway for heating water, but looking at my own supply even in the summer the incoming cold supply is around 10C. Getting it to 30C requires a lot of power.
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May 02, 2012, 06:18:50 AM
 #84

I don't see why that idea would be expensive though. It seems like something that could be done for $20, and perform as well or better than a large plate exchanger. The biggest downside is the floor space and low SAF.

Copper loops, finding a hot water heater in decent shape, rigging up some water tight seals.  I mean remember this isn't a science experiment.  It is the water my family drinks.  It doesn't seem worth it.  Like I said it would provide marginally more recovered energy but hacking around with drinking water isn't my idea of a good ROI%.  I also don't think you are going to find all the parts, supplies, connectors, and tools for $20 but even if it is was $0.00 I don't think messing around with drinking water is a good idea.

I think you are missing the point on the amount of water.  2 ft, 20ft, 20,000ft it doesn't really matter how much energy is in the loop.  We aren't storing it for on demand use.  That energy will be dumped out of the loop at the same rate regardless of how big the loop is.

Your points are valid, it would be significantly more work to ensure it was built well and safe. As for the amount of water, to efficiently transfer the heat you need a large amount of surface area. To have a large surface area without excessive restriction, you'd need a large volume. That requires more water with more stored energy.

I'd actually be very interested in your calculations for the plate heat exchanger you looked at, and what the stats are for your system in terms of flow rate and head pressure, temperatures and such. With 6kW, you have a lot of leeway for heating water, but looking at my own supply even in the summer the incoming cold supply is around 10C. Getting it to 30C requires a lot of power.

Its  not about getting it to 30c. But it's sure as hell higher than 10c. Not much energy saved but free is better.

Beside, i'm doing it to help with the heat being dumped in the house during hot summer days.

Now, i'm not sure how well it work. I hoped high untill i saw ciuciu's pic. LOL  

Any responsible human being wouldnt waste water like that. Clean water isnt cheap. Its infact more expensive than gasoline where i am.
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May 02, 2012, 08:42:28 PM
 #85

ok.. so I've been thinking...  flat plate on cold water inlet vs. 2nd tank with sidearm heat exchanger...

I see the trade off as being:  with the flat plate method, you are only getting benifit while you are taking a shower.  Lets say the entire household totals 1 hour per day.  you get maximum effenciency/minimum price with the flat plate, but only for (1/24) = 4.1% of the time.. the other 95.9 percent, you are getting nothing. 

So the question is. how much heat are you recovering during that ~4% of the day?  after doing some research (yer geeks, you know how to use google..) I found that 1 Kilowatt/hr will heat 409 gallons 1 degree.  Lets assume you need a delta increas of 40 degrees.. so 1 Kilowatt/hr will cover approx 10 gallons.  assuming 2 gallons per minute on the shower, the question is:  does your water loop provide 1 kwh of heat energy every 5 minutes or less?  If yes, then you are golden with the flat plate setup. 

If not, then your water loop cannot keep up with your shower, and you need to extend the time where you are extracting heat.  To do this, it seems to me the best way would be to install a 2nd tank (cheap/new or used.. ) with a sidarm heat exchanger.  Put this inline with your hot water heater on the cold side instead of the flat-plate.  While this is the more expensive option, in the long run it should pay off as you will be actually be pre-heating all the shower water instead of just some.

If like me, your needed temp increase is closer to 60 degrees, then the calculations lean even further in the direction of 2nd tank.

Alternatively, you could just install water saving shower heads...  Ugg, I hate those things.

Sigg

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