Topic: (Updated w/ pics) Watercooled Rack of Servers - 50% completed - page 3. (Read 10536 times)

"The term "negative pressure" is used in physics and engineering to refer to a situation in which an enclosed area has lower pressure than the area around it. Any compromise in the divide between the area of negative pressure and the more highly pressurized area around it would cause substances to flow into the area of negative pressure."

Please, humor me.

The cards are in series. I have only one heat exchanger.
http://koolance.com/index.php?route=product/product&path=54_119&product_id=944

I agree with this post. Simple fluid dynamics.  Fluid flows from high pressure to low pressure.  Or it wouldn't flow at all

Hoping you can post a video showing a walk around of the rack.
Love your hose connectors on the front.

Please enlighten me on this simple theory.  Why does the resistance not cause more pressure on one side when the fluid is being pumped through a restriction?  Surely you can explain such a simple theory to someone with a degree in math from an engineering school.

AH, yours is a sealed system? MY system has the overflow tank, thus there is a positive and negative pressure. Thus if air enters from the suction, it's released in the overflow tank.

Besides, restrict the water flow in your closed loop (such as running it through a water block compared to 1 inch hose), and you can bet your ass you'll have negative and positive pressure on either side of the restriction.

Yes, you right. First card is at 20C last at 40C. To lower the temperatures I can increase the cold water debit, but I want to keep the noise down.

Connecting the loops in series would allow higher temps to be dumped into the heat exchager right? The higher delta T the better. But it also means that your rigs run hotter or at least some of them do. Which might create more energy consumption due to the worse switching efficiency of higher temps on GPU.

Yeah, the heat was driving me insane last summer.

Awesome.  First I have heard of anyone else doing this.

Hi,
I have a similar setup, with 12 cards (9 5970 and 4 5870) working flowlessly for about 1 year.  The diferrence is that I ran them in series. I'm using a Koolance heat exchanger connected to the cold water line. Will soon add 5 more cards.

For high efficiency water heater standing losses are less than 20%.  So if you use x BTUs of energy per day/week/month/year 0.8x is heating up cold water and only 0.2x (or less) is keeping that water hot.

I use about ~$300 per year in hot water so lets assume that is ~$240 toward heating up water, and $60 towards keeping it hot.  Heat exchanger should be able to preheat 60F water to >120F for "free" using the waste heat of the GPU loop.

Sure having a custom built hot water heater with an internal water to water heat exchanger and bypass valve and backup heat source would provide even better efficiency but it also would cost a LOT more, and provide only a marginal increase in savings.

So:
spending $80 on heat exchanger (+ parts &  labor) = recovery 80%-90% of energy costs
vs
spending $1500 on new custom hot water heater (+ parts & a lot more labor = recovery 90% - 100% of energy cost.

Simply put using heat exchanger as a pre-heater is "good enough" and provides a much higher ROI%.  Another way to look at it is every BTU of energy dumped into the cold water line is a BTU the hot water heater doesn't need to expend.  "Free" BTUs vs paid BTUs.


Regarding pressure & flow.  Flat plate exchangers they can handle much greater pressure than home water systems.  They are often used in industrial cooling applications.  Those brazetek models have burst rating of 400 psi.  They make them in all sizes able to handle 10gpm up to 100gpm+ at various pressure losses. 

these plate heat exchangers sound like a good plan in theory. A couple of questions rises though. Are they capable of handling the water pressure in your cold water line and do they have enough flow? ...okay you said you could put a few in but still. You only run hot water like 0.1% of a day, double or triple that if you got a wife. So during that time you could save money. My point being that you would actually have to ditch that water boiler all together and build a custom water boiler that constantly circulates the boiler water through your heat exchanger to have any kind of hope to save money. Your water boiler is still going to keep that water heated during that 99.9% of the day

House heating during winter times would yield a lot better ROI IMHO.

Oh and another thing I thought about. What is the temp that your pump can take(if you are considering moving it to the other side)? What will it do to its life span? I'd say the water coming from your 24 GPU rig will be burning hot. Your tubes will melt

Yeah the radiator will be outside but my goal is to maximize the amount of energy "harvested" for heating water so the loop is

GPU (heat source)   ---> water2water exchanger (preheater) -----> radiator (outside) ----> coolant back to GPUs.


I will be using flat plate heat exchanger.
You can reduce pressure loss by using more plates.

http://www.brazetek.com/brazed-plate-heat-exchangers

I have a strong feel to drop that radiator into a lake during summer 

I get what you are saying now but remember heat only flows from hotter side to cooler side.

The cold water line will never be hotter than the hot loop (loop carrying GPU waste heat).  At worst it will be the same temp (Delta T = 0) and there will be no heat flow. 

So water is flowing on cold water inlet to hot water heater heat will be transfered from hot loop to cold water raising its temp (and saving me energy).  When hot water is shut off, the water in line will reach equilibrium with hot loop and heat transfer stops.

Will do.  Don't one to pull the existing rigs out of the rack but I will be building/converting rig #4 this weekend.  Will snap some shots.

Once you have a leak it isn't a closed loop.

P.s. Snag some pix of the innards.