Chiller pump feedback

[Marvin]

Fellows, how long are your pumps working without problems at subzero temps ?
Please tell us the model, application(sub or inline),coolant, how many hours per day usage, and other info that would help us to choose it.
reards

 

[gclg2000]

i had a mag drive 250gph that worked fine. I think what alot of people don't account for, is that the pump impeller generates some heat. My pump never ran warm it was just "cool" It never condensated past the inlet/outlet ports. I ran it for a couple weeks though before i tore it apart to use the compressor on a phase changer

 

[Ice Czar]

pump heat is mostly the imparting of kenetic energy to the coolant itself

http://www.overclockers.com/articles599/

Summary

If you increase flow rate with the same pump, your temperatures will trend in the direction of goodness. If you increase flow rate by going to a bigger pump, you will reach a trade off somewhere where the pump starts putting too much energy into the system and temperatures will start increasing.

 

[gclg2000]

This can't be applied here, because it all matters on the surface area of the evaporator coil used in the submerged liquid and also the wattage rating of the compressor and yada yada along with the type of gas used in the chiller loop and yada yada.

The amount of heat generated "by the kinetic friction" is minimal. As long as you have a good sized evaporator or "heat exchanger" you'll be fine.

 

[Ice Czar]

well my chip chiller has 2 sides
the refrigrant loop with compressor, condenser\heatexchanger, radiator
and the coolant loop with the pump, waterblock and heat exchanger

in which case it does apply
and since he said pump instead of compressor...

 

[gclg2000]

well my chip chiller has 2 sides
the refrigrant loop with compressor, condenser\heatexchanger, radiator
and the coolant loop with the pump, waterblock and heat exchanger

in which case it does apply
and since he said pump instead of compressor...

First i don't know what he's talking about with using a radiator in any part of his loop. Radiator's are not used in Coolant loops. If he's using a radiator on the liquid loop that's even worse cuz its just sitting there blowing hot "room temp" air in the form of mucho watt's and really hindering the loop's cooling power itself.

The evaporator submerged into the liquid reservoir is what absorbs all the heat from the coolant line and it is then blown off by the condensor fan.

I wouldn't make such a big deal out of the pump question. Just don't submerge the pum entirely into the liquid, that will for sure make the evap/liquid absorb all the heat and the is the worst goal of what your trying to do. Just put the pump external to the reservoir, that way only the impeller is "touching" the coolant line and the excess heat is not absorbed as much. You can really help this by putting a fan onto the pump to help it out.

Main thing though. You'd prob do the most harm by submerging the pump into the liquid. If you using alcohol or something like that to cool it with, it can be not so good of an idea cuz the alcohol will slowly eat at the plastic and rubber and all the parts and yada yada.....what are you using for your liquid?

A couple things i would do though. Is remake your evaporator into a coil of copper tubing about 25-30ft long or so using 1/4" or even 3/8" would be best. This will give you more surface area for the chilled liquid to come in contact with, resulting in better cooling. 3/8" would also be good b/c it will probally match up with your suction line, which ideally should be 3/8" also. Then you can just wrap your metering device line around the suction line also for a little bit better subcooling.

I've listed pictures below to help show what i'm talking about. Hope this helps, and we are all here to help you out buddy.

The evap coil i was talking about.

and the metering device, wrapped around the suction line.

 

[Ice Czar]

First i don't know what he's talking about with using a radiator in any part of his loop.

ahh nothing like early morning caffine deprivation induced dyslexia
you are correct that is an innaccuate description the corrected version would be
the refrigrant loop with compressor, evaporator\heatexchanger, radiator/condenser
and the coolant loop with the pump, waterblock and heat exchanger


and its not absorption of heat from the pump that is the issue had you read the article or the link to the thread at the bottom
energy is energy, you can convert it but not destroy it
the actual motion of the coolant is adding energy to the loop

There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a Constant (the specific heat of water) times the Delta T (fluid temp out minus fluid temp in):

Q = M x C x Delta T

In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Since you cannot mess with mother nature, it is very naive to think it works any other way.

Assume the CPU inserts a constant rate of energy (Q) into the cooling system. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant. This smaller Delta T (fluid out - fluid in) also means that the average fluid temperature in the water block is somewhat lower even though the rate of heat transfer has not changed.

Now let's look at the heat transfer from the CPU to the water:

The rate of heat transfer between two points is proportional to the temperature difference between those points.

In our case, this Delta T (not to be confused with the one above) is the temperature of the CPU minus the average water temperature in the water block. Lowering the average water temperature, as we did above by increasing the flow rate, means we have a little better heat transfer from the CPU to the now somewhat cooler water. The result is that the CPU runs a little cooler.

This all says that if you increase the flow rate and everything else remains constant, you will decrease the CPU temperature. However, everything else will not remain constant if you increase the flow rate by using a larger pump.

The pump uses some amount of electrical energy. This energy must end up somewhere. A relatively small amount of it is dissipated as heat from the motor. The overwhelming majority of it is converted from electrical energy to mechanical energy in the form of a rotating shaft that does real work on the water.

This energy ends up in the water by increasing its temperature. It is called "pump heat" and can be very significant.

An Eheim 1048 is rated at 10 watts, almost all of which ends up in the water. I understand a very overclocked CPU is good for upwards of 75 watts. As you can see, a smaller pump like the 1048 contributes about 13% to the total heat load on a system with an energy hungry CPU. With other more common CPUs running at 25 to 50 watts, this percentage is much higher and is therefore much more significant.

An interesting aside for non-believers: This is also why excessive use of a blender to mix up frozen orange juice results in the juice not being as cold as expected. Also, nuclear power plants use primarily pump heat (from three or four 6,000 HP pumps) to heat up almost 75,000 gallons of water from 200 degrees F to about 550 degrees in about six hours or less.

The point here is that there is a trade off in how big a pump to use to increase the flow rate. More flow is beneficial. It is best to achieve the desired flow with as small a pump as possible and flow paths with minimum flow resistance.

The bigger the pump, the more heat is added to the system. Eheim makes a 50 watt unit that I see talked about every now and then. This guy is probably a bigger heat load on the cooling system than the CPU itself.

PS RhoXS is a nuclear engineer, and has more than a passing understanding of cooling
hmm... the link is busted
here is the original thread its quite long also take special note of BillA's contributions
http://www.ocforums.com/showthread.php?t=78055&highlight=thermodynamics

 

[gclg2000]

ahh nothing like early morning caffine deprivation induced dyslexia
you are correct that is an innaccuate description the corrected version would be
the refrigrant loop with compressor, evaporator\heatexchanger, radiator/condenser
and the coolant loop with the pump, waterblock and heat exchanger

Just run your pump outside of the liquid man and you'll be fine. My pump lasted along time in my chiller and i stil luse the same pump currently for a video card block i use.

Your original question's answer is. The pump will be fine with the colder temps.

Hope this helps, and we are all here to help you out buddy.

 

[Marvin]

Thank you guys, so i wouldnt be worried with my EHEIM 1250 to pump the fluid....
i Hope my PVC reservoir handle that cold...

i dont have the $$ to buy a copper reservoir....

 

[gclg2000]

looks great so far. What gas you goona put in it???

I can get some *MISC* parts if you get in a jam.

 

[Marvin]

INstead of the compressor is for R12 , it will run with R22...

 

[gclg2000]

you should be able to use R404. Thats a common gas in the back of any A/C guy's truck. But R22 is good to around -30 or so, so that will work too.

 

[macrospect]

Is it just me or is that tecumseh compressor in Marvin(s) picture rather large? Whats the model on it by chance?

 

[Marvin]

It is AE1380AS.