water cooling help

[bbaall]

hey,
i am designing a water cooling system and was wondering how does the flowrate and pressure drop effect the heat carrying capacity of water, is it a way to find out the required flowrate and pressure drop or is there any formulas? another thing i was wondering is how to calculate the pressure drops in water blocks and ideally what should be the normal inlet and outlet water temperature diffrence.

[billbartuska]

Originally Posted by bbaall

hey,
i am designing a water cooling system and was wondering how does the flowrate and pressure drop effect the heat carrying capacity of water, is it a way to find out the required flowrate and pressure drop or is there any formulas? another thing i was wondering is how to calculate the pressure drops in water blocks and ideally what should be the normal inlet and outlet water temperature diffrence.

Well, the restriction a pump has to work against will effect it's output, both pressure and flowrate. Martin's Flow Rate Spreadsheet is an excellent tool for determining these effects.

You'll also need some information on how the block(s) and rad you plan on using perform at various flow rates. Here's a good guide on how to determine what you need to know.

And, of course, searching these forums will answer pretty much any other questions you may have concerning watercooling.

[bbaall]

thanks billbartuska, the spreadsheet is quite good and i will have a look at the forums as well.
thanks for ur help

[#Rotor]

Damn haven't had my hand at this for a while, but they say it's like a bicycle, so here goes....

rule of thumb: The bigger the Delta in Temp between your transducers and your carrier, the more heat energy will be transferred.

what does this mean???.... simple really, flow-rate is everything. well almost.

but you will do good by making it your nr1 goal, to have as high a flowrate as is possible with what you have to work with...

[Brians256]

Flowrate is good for a REALLY good reason: barrier region.

High velocities make the region of slow moving coolant next to heat exchanging region (waterblock or radiator) thinner. So, the dT is moving heat over a thinner volume of stagnant water.

#Rotor, I'm not sure what you are talking about, since the velocity doesn't affect the water temp in between heat exchange elements. Well, actually a higher-power pump can add another parasitic element to the system by heating up the water, but that's another matter.

As for the bicycle metaphor, I'm not sure that the person who came up with it ever *had* sex. If he/she did... then that must have been a REALLY good bicycle ride to even think about comparing it to a real relationship. Who ever heard of make-up bicycle rides?

[#Rotor]

well the way I see it.... the longer the carrier ( water) resides in an exchanger, the more heat is absorbed or expeled... this is usually the thing most people think of as a good reason why the water should flow slowly.... but not, since the longer it stays, the smaller the difference in temp between the water and the exchanger becomes. And it's the Delta-T that is the primary key to good effective cooling. Without Delta-T nothing will happen, no matter what you do.

So to actually put it more correctly, do whatever it takes to have your Delta-t's, be it between the water and block, or between the water and the radiator, as large as you possibly can....