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Pump Heat Question

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Freeloader

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Jun 20, 2002
Location
Winnipeg
I have read many threads where the poster claims that putting the rad in between the pump and block improves performance by 1 or 2c. The idea being that the pump heat is removed before the water hits the block.

From what I read elsewhere, a 100watt load adds less than .5c to a 100gph flow. This means that a 30 watt pump will add less than .2c to the system. Since only about 50% or less heat is transfered at the pump, with the rest transfered throughout the system, the actual temp rise between the pump and block should be around .05c . A 10 watt pump sould be a third of that.

So the question is, is there something that I'm missing that can account for the larger improvement that people are seeing

EDIT: changed 100gpm to 100gph.
 
Last edited:

JFettig

Hey! I showered! Senior
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Jan 5, 2002
Location
MN
thats exactly what i was getting at in the microchannel thread to nikhsub1
 
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Freeloader

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thats exactly what i was getting at in the microchannel thread to nikhsub1

LOL, that's exactly why I started this thread, maybe we can put this myth to rest once and for all (doubt it)
 

Toysrme

Member
Joined
Nov 12, 2001
If you're running a T-line I doubt you'd see 1/2C difference. Submerged pump maybe you'd see some, but alias I have no expertise there so I won't touch it.

-Toysrme
 

gone_fishin

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Feb 11, 2002
Location
U.P. Michigan
Having the coolest water in the loop actually enter the block is to an advantage, not disadvantage. Volumetric flowrate is the same no matter where you are in the loop. What is the myth you are refering to?
 
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Freeloader

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Location
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Did you even read the initial post? I was saying that the improvement is so small (.05C) that it really doesn't matter. Are you actually worried about a .05c improvement. Do you really believe that you could actually tell the difference.

Volumetric flowrate is the same no matter where you are in the loop.

Who said anything about flowrate being different?
 

SkiFletch

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Jun 24, 2002
Location
Crotchfester (aka rochester), NY
yeah, pump heat isnt that significant at all. people who claim that changing the position of the pump in the line affects the temp by more than 1c are probably more likely experiencing the affects of a different flowrate because of a different tubing setup than are experiencing the removal of significant pump heat
 

gone_fishin

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Feb 11, 2002
Location
U.P. Michigan
The degree of significance is dependant on the amount of heat given off by the pump. Variables. A restrictive design will produce more pump heat also with different blocks because of more back presure. The style rad induces its own amount of backpresure also. A large pump obviously would make a larger impact than a puny one. Once the pieces are set up in the case, the overall length of the tubing would be equal no matter which direction it was set up so I do not understand that point. Why would you want to set it up in the manner in which it would be detrimental to performance in the first place?


Quote
"From what I read elsewhere, a 100watt load adds less than .5c to a 100gpm flow. " end quote from thread starter.

100gpm is an enormously exagerated figure. 1gpm to 3gpm is more the norm.

The amount of pump heat is different from system to system and the efficiency of the heatercore is also different from system to system because of style, size, airflow and water flowrate. It is logical then to conclude that the impact of rad placement will be different from system to system but it will always be worse if the rad is after the block instead of before the block. I think you are touting a myth instead of dispelling one:D
 

nikhsub1

Unoriginal Macho Moderator
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Oct 12, 2001
Location
Los Angeles
I just asked BillA about this same very issue. He has said what gone_fishin has said, flow rate is the SAME throughout the loop (unless you have some crappy res disrupting flow) so why not have the coolest water going to the block WHEN THE FLOW RATE AND VELOCITY IS THE SAME?
 

Since87

Member
Joined
Jul 30, 2002
Location
Indiana
gone_fishin said:
A restrictive design will produce more pump heat also with different blocks because of more back presure.

A centrifugal pump consumes less power when restricted. The result will be less pump heat going into the water for a relatively restricted system.

I'm not saying restricted is good, just that this is the way centrifugal pumps behave.

There's a discussion of this going on at procooling.
 

gone_fishin

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Feb 11, 2002
Location
U.P. Michigan
Since87 said:


A centrifugal pump consumes less power when restricted. The result will be less pump heat going into the water for a relatively restricted system.

I'm not saying restricted is good, just that this is the way centrifugal pumps behave.

There's a discussion of this going on at procooling.

Ah, another variable, type of pump. Thanks for puttin up the link.:)
 
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Freeloader

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"From what I read elsewhere, a 100watt load adds less than .5c to a 100gpm flow. " end quote from thread starter.

Typo, I meant 100gph. The numbers I quoted for a 30 watt pump were worse case senario. At 50 gph, the temp would increase to .1c or less between the pump and block. Any lower flow would be unrealistic with a 30 watt pump. Even 50gph is unrealistic.

the overall length of the tubing would be equal no matter which direction it was set up so I do not understand that point.

I have no idea what you're talking about.

Why would you want to set it up in the manner in which it would be detrimental to performance in the first place?[/

.05c isn't derimental. Too many times I see people telling other people to change their setup to pump>rad>block because the temps will improve 1 or 2C, when the actual improvement is so small it's irrelevant. A person should hookup their system to whatever is most convienient
 
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Freeloader

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flow rate is the SAME throughout the loop (unless you have some crappy res disrupting flow) so why not have the coolest water going to the block WHEN THE FLOW RATE AND VELOCITY IS THE SAME?

Please show me where I said that the flow rate would be different. Of course it wouldn't be any different. That was never the point. Why not ask BillA how much of a temp rise there is between the pump and block with a 30 watt pump and 100gph flow?(+/-.05C)
 

Toysrme

Member
Joined
Nov 12, 2001
I still say I like having colder water flow through the pump first, even though there is no data linking slightly cooler water with longer pump life. Can't hurt it though...

-Toysrme
 

DodgeViper

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Sep 21, 2001
Location
WILDCAT COUNTRY
PUMP>>>RAD>>>WATER BLOCK>>>PUMP is the best choice, but I would like to see the difference in temps in this method, RAD>>>PUMP>>>WATER BLOCK>>>RAD.

If you use a three barb heater core with a three barb water block you have no choice than to use the last configuration, that is if you want to get away from using a Y fitting.
 

myv65

Registered
Joined
Mar 28, 2002
The "best" answer is the method that yields the lowest CPU temperatures. For many people, this means whatever allows the best arrangement for getting the coolest air to the radiator. As others have noted, pump before vs after is typically on the order of 0.1°C or less. If moving the radiator via a plumbing change lets you pull air even 1°C cooler, it'll be the right answer.
 
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Freeloader

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Welcome to the forum myv65! I've read many of your posts over at procooling and am glad to see you over here. Maybe you could answer a question for me while your in the neighborhood. Is there a math formula to calculate how much the water temp would rise with a 100watt load and 100gph flow, or something along that line. If anybody else knows, fell free to post
 

myv65

Registered
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Mar 28, 2002
Freeloader said:
Welcome to the forum myv65! I've read many of your posts over at procooling and am glad to see you over here. Maybe you could answer a question for me while your in the neighborhood. Is there a math formula to calculate how much the water temp would rise with a 100watt load and 100gph flow, or something along that line. If anybody else knows, fell free to post

I registered here quite a while back, but have mainly been lurking sporadically. As to your question, I'll refer ya to one of my articles at AMDMB, right here.