So what is head when discussing a pump and what does it have to do with a water cooling circuit? This ought to be a good topic as I think this is a much misunderstood issue. From what I have gathered from pump websites and speaking to those in the know, head pressure is measured at the pump outlet with no fittings attached.
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Anybody for a little head?
- Thread starter Top Nurse
- Start date
The general definition of a pump's "pressure-head" is the maximum vertical height at which the pump can no longer exert enough pressure to move water.
Feel free to correct me on any of the following, this is my collective learnings of a little research into pump head, and I'm always game for education..
A pump will move water at it's given flow rate until it reaches it's maximum head pressure.
(ignoring the resistance comming from tubing friction)
Keep in mind everything in your loop adds resistance to the pump, may it be fittings, blocks, radiators, sharp bends etc.
The smaller the diameter of tubing used, the higher the head of the pump required to maintain flow (in before the physics buffs
). A general rule to compensate additional head when shrinking the diameter of tubing, is to take the percentage difference between the tubing diameter sand multiply it by the length of the larger tube:
example
5' of 1/2" ID to 7/16"
7/16" = 87.5% of 1/2" = 12.5% difference
12.5% * 5' = 0.625' of additional head required to overcome the change in tubing.
How one goes about calculating how much head is required to effectively circulate a watercooling loop, I'm at a loss. Heck some of this stuff dosent make an entirety of sense to me, or seems to be contradictory. Hopefully someone can come and correct me and set things clear
Feel free to correct me on any of the following, this is my collective learnings of a little research into pump head, and I'm always game for education..
A pump will move water at it's given flow rate until it reaches it's maximum head pressure.
(ignoring the resistance comming from tubing friction)
Keep in mind everything in your loop adds resistance to the pump, may it be fittings, blocks, radiators, sharp bends etc.
The smaller the diameter of tubing used, the higher the head of the pump required to maintain flow (in before the physics buffs
). A general rule to compensate additional head when shrinking the diameter of tubing, is to take the percentage difference between the tubing diameter sand multiply it by the length of the larger tube:example
5' of 1/2" ID to 7/16"
7/16" = 87.5% of 1/2" = 12.5% difference
12.5% * 5' = 0.625' of additional head required to overcome the change in tubing.
How one goes about calculating how much head is required to effectively circulate a watercooling loop, I'm at a loss. Heck some of this stuff dosent make an entirety of sense to me, or seems to be contradictory. Hopefully someone can come and correct me and set things clear
Just so everyone can talk from some sort of base...
Original WC system:
- MCP655 pump (setting 5)
- MCR220 rad
- original Apogee CPU block
- MCW55 GPU block
- (2) temp fittings
- Swissflow flow sensor
- 7/16 tubing
My flow was 5 lpm. The pressure/flow curve off the Swiftech site shows a system pressure of ~ 300 mBar at this flow. If one were to put a pressure gage just downstream of the pump, this is where the one would see 300 mBar.
Current WC system: As above except:
- dtek fuzion CPU block
- 2nd MCR220 rad
- (2) additional temp fittings
- 2 Colder quick connects
With this configuration, flow is 4 lpm. Corresponding head pressure is ~ 325 mBar. Obviously, different system are going to deviate somewhat from these numbers, but should still be relatively close to 300 mBar, give or take a bit... Tubing size, additional blocks, etc. will influence this number somewhat, but it is a good (IMO) starting point for any further discussion.
So, based on this data (and assumption), it would seem reasonable that most WC systems would see an approximate 300 mBar drop thru their system. If you wish, you could use this number to determine an *approximate* system flow rate for a given pump.
Does this help????
Original WC system:
- MCP655 pump (setting 5)
- MCR220 rad
- original Apogee CPU block
- MCW55 GPU block
- (2) temp fittings
- Swissflow flow sensor
- 7/16 tubing
My flow was 5 lpm. The pressure/flow curve off the Swiftech site shows a system pressure of ~ 300 mBar at this flow. If one were to put a pressure gage just downstream of the pump, this is where the one would see 300 mBar.
Current WC system: As above except:
- dtek fuzion CPU block
- 2nd MCR220 rad
- (2) additional temp fittings
- 2 Colder quick connects
With this configuration, flow is 4 lpm. Corresponding head pressure is ~ 325 mBar. Obviously, different system are going to deviate somewhat from these numbers, but should still be relatively close to 300 mBar, give or take a bit... Tubing size, additional blocks, etc. will influence this number somewhat, but it is a good (IMO) starting point for any further discussion.
So, based on this data (and assumption), it would seem reasonable that most WC systems would see an approximate 300 mBar drop thru their system. If you wish, you could use this number to determine an *approximate* system flow rate for a given pump.
Does this help????
Heat dump doesn't enter the equation till after you hook it up to a loop, correct? And isn't the head pressure rated at the outlet with no fittings attached? So given that, I don't think head is useful unless you are talking about a specific cooling loop, correct?
madmat
2[H]4U
- Joined
- Jun 3, 2005
- Messages
- 2,372
Head is the ability of the pump to move a 1" column of water. Using a formula you can hook a pressure meter, flow meter and valve to a pump and plot the flow curve but you'll have to hook all these things to the pump to do so so you can't say "With no fittings" because each of those items IS a fitting.
Arcygenical
Fully [H]
- Joined
- Jun 10, 2005
- Messages
- 25,066
TN you dirty girl you. Shame on you
Head should be measured with a totally unrestricted pump other than the measuring utilities... On a vertical stretch of tubing equal to the diameter of the pump outlet. The volume of this water is equal to pi*r^2*h where r^2 = .5"^2 and h = 1"
or about 0.785398163"^3
Head should be measured with a totally unrestricted pump other than the measuring utilities... On a vertical stretch of tubing equal to the diameter of the pump outlet. The volume of this water is equal to pi*r^2*h where r^2 = .5"^2 and h = 1"
or about 0.785398163"^3