regarding specs

moonlightcheese · 08-26-2005, 07:41 AM

as far as specs go for pumps, PQ is about as good as it gets but it's difficult to determine the flow rate of a system with only that information since all of the pressure drop is happening at the water blocks. i was hoping to see some way of determining how much pressure drop to expect from a specific block along with the dTvsQ graph in the block reviews. the purpose of this measurement is to help with deciding on a pump to get for a specific system.

the way i'm understanding is, that at extremely low flow rates (eg. 0.5GPH) there is no pressure drop since it's hard to really restrict such a flow rate. however there comes a specific flow rate at which pressure drop begins. this could be labeled as restriction point (i'm not sure what the technical term would be), the amount of flow necesarry to produce significant restriction.

also, in addition, it would be nice to have dPvsQ graph for each block to give an idea of how much restriciton to expect from a setup. this way you can just look at the pressure drop as a static number, which would make it much easier to choose a pump for a system. ie:

Storm G4 = ~3PSI and 1GPH restriction point
DDMazeGPU ~2.3PSI and 0.7GPH restriction point
tubing ~1PSI and negligible restriction point

so you need at least 6.3PSI of head pressure to produce a somewhat effective loop. this is just a suggestion from my incredibly elementary understanding of pressure and flow, where (as i've read... as long as i haven't misread) the total drop in pressure is the sum of all of the restrictions in the loop. it may not be that simple but this gives a rough idea to people who need to know which pump to get for a specific setup given "x" "y" and "z" blocks in the loop.

is something like this possible? or even feesible?

bobkoure · 08-26-2005, 08:05 AM

Are you talking about the Reynolds number?

Water Flow in Tubes - Reynolds Number

moonlightcheese · 08-26-2005, 08:57 AM

no... that doesn't look like it.

jaydee · 08-26-2005, 09:24 AM

I think he wants to know the pressure drop of the water blocks. Something pH is doing and something I am working on doing. This info should start showing up sooner or later. Also Robotech has already posted some data on it. Problem is there is no way we are gong to cover every block on the planet.

But yeah, if you know how much presure drop there is for each part and a general idea of what the pump can do you should be able to put together a decent system. This has been a project in the works around here for ever now. Just not easy to do because of so many combinations of components.

moonlightcheese · 08-26-2005, 10:05 AM

Quote:

Originally Posted by jaydee

I think he wants to know the pressure drop of the water blocks. Something pH is doing and something I am working on doing. This info should start showing up sooner or later. Also Robotech has already posted some data on it. Problem is there is no way we are gong to cover every block on the planet.

But yeah, if you know how much presure drop there is for each part and a general idea of what the pump can do you should be able to put together a decent system. This has been a project in the works around here for ever now. Just not easy to do because of so many combinations of components.

now that's what i'm talkin about. each block creates a certain amount of pressure drop as does bends in the tubing, etc. now if you eliminate (or make negligible) the tubing as a flow restrictor (using a small amount of tubing) you can get a general idea of the restriction you can expect from each block.

yea covering every block there is would be no small task but covering the main blocks would be nice, like the Swiftech, DangerDen and Cathar parts and maybe a few other popular designs like some NexXxos blocks or something. it would make it MUCH easier to determine necessary head pressure.

also, i realize that this data is only somewhat useful, because certain blocks (like the G4 and TDX) require powerful pumps to get the most out of the block, which is why the dTvsQ graphs exist. but by providing the pressure drop with the review you can get a general idea of how much flow is NECESSARY (although not optimal) for running a certain loop. this type of measurement would be ideal for people looking for a silent system, rather than high performance, as they would be able to pick a low power pump based on the pressure drop of each component in the loop.

jaydee · 08-26-2005, 10:56 AM

What bothers me is manufactures should provide this information. It shouldn't be left up to us to figure it out. We should be here to verify the information not create it in the first place.

billbartuska · 08-26-2005, 03:09 PM

Mfgr's specs for restriction of blocks (rads and res's too) would be great.
went through the following machinations to approximate the flows I would get by replacing an Eheim with an Iwaki. The only info I "knew" was the flow rate of my current system..the rest is easy if you have pump curves (which are available for most).

Flow resistance for some blocks (and some rads) is available as stated above, but it takes alotta digging. And doesn't account for your specific tubing (size/type), barbs, and routing.

Nor does it account for the barrametric pressure, phase of the moon or currency rates at the time of the testing...sorry, can't get \\WING// out of my head!

Les · 08-26-2005, 04:42 PM

Quote:

Originally Posted by billbartuska

,,,,,,,,, went through the following machinations to approximate the flows I would get by replacing an Eheim with an Iwaki. The only info I "knew" was the flow rate of my current system..the rest is easy if you have pump curves (which are available for most).,,,,,,

Not sure I follow your machinations or the flow rate you are predicting.
My method:-
Eheim1048; flow rate 2.2 lpm indicates 1.335 m(H2O) System PD (Yellow data point)
Construct "System P/Q curve" assuming P=Constant*Q^2 which gives the "dotted black line" with an intersection of the "Iwaki P/Q curve" at 4.79 lpm.
The predicted Flow Rate is ~ 4.8 lpm

bobkoure · 08-27-2005, 09:33 AM

Quote:

Originally Posted by moonlightcheese

...however there comes a specific flow rate at which pressure drop begins.

This is what had me thinking you were looking for the Reynolds number - essentially the point at which the flow transitions from laminar to chaotic. Now that I think of it, probably only an "open" block or maybe a maze block has laminar flow.
So the question becomes, given already-chaotic flow (so no "hockey stick" shape to the graph) what does the flow/restriction curve look like?

08-26-2005, 07:41 AM	#1
moonlightcheese Cooling Neophyte Join Date: Jul 2005 Location: Atlanta, GA Posts: 13	regarding specs as far as specs go for pumps, PQ is about as good as it gets but it's difficult to determine the flow rate of a system with only that information since all of the pressure drop is happening at the water blocks. i was hoping to see some way of determining how much pressure drop to expect from a specific block along with the dTvsQ graph in the block reviews. the purpose of this measurement is to help with deciding on a pump to get for a specific system. the way i'm understanding is, that at extremely low flow rates (eg. 0.5GPH) there is no pressure drop since it's hard to really restrict such a flow rate. however there comes a specific flow rate at which pressure drop begins. this could be labeled as restriction point (i'm not sure what the technical term would be), the amount of flow necesarry to produce significant restriction. also, in addition, it would be nice to have dPvsQ graph for each block to give an idea of how much restriciton to expect from a setup. this way you can just look at the pressure drop as a static number, which would make it much easier to choose a pump for a system. ie: Storm G4 = ~3PSI and 1GPH restriction point DDMazeGPU ~2.3PSI and 0.7GPH restriction point tubing ~1PSI and negligible restriction point so you need at least 6.3PSI of head pressure to produce a somewhat effective loop. this is just a suggestion from my incredibly elementary understanding of pressure and flow, where (as i've read... as long as i haven't misread) the total drop in pressure is the sum of all of the restrictions in the loop. it may not be that simple but this gives a rough idea to people who need to know which pump to get for a specific setup given "x" "y" and "z" blocks in the loop. is something like this possible? or even feesible?

08-26-2005, 08:05 AM	#2
bobkoure Cooling Savant Join Date: Feb 2003 Location: USA - Boston area Posts: 798	Are you talking about the Reynolds number? Water Flow in Tubes - Reynolds Number Last edited by bobkoure; 08-26-2005 at 08:08 AM. Reason: added a link for Google impaired

08-26-2005, 08:57 AM	#3
moonlightcheese Cooling Neophyte Join Date: Jul 2005 Location: Atlanta, GA Posts: 13	no... that doesn't look like it.

08-26-2005, 09:24 AM	#4
jaydee Put up or Shut Up Join Date: Dec 2001 Location: Spokane WA Posts: 6,506	I think he wants to know the pressure drop of the water blocks. Something pH is doing and something I am working on doing. This info should start showing up sooner or later. Also Robotech has already posted some data on it. Problem is there is no way we are gong to cover every block on the planet. But yeah, if you know how much presure drop there is for each part and a general idea of what the pump can do you should be able to put together a decent system. This has been a project in the works around here for ever now. Just not easy to do because of so many combinations of components.

08-26-2005, 10:56 AM	#6
jaydee Put up or Shut Up Join Date: Dec 2001 Location: Spokane WA Posts: 6,506	What bothers me is manufactures should provide this information. It shouldn't be left up to us to figure it out. We should be here to verify the information not create it in the first place.

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