Q about flowrate

{BC}Helix

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• Oct 12, 2003

• #1

i'm testing my system right now and have a bit of a concern about flowrate. as i look through my tubes i can (somehow) see the water flowing through the tubes but it isn't going very fast. i'd say a bubble would cross 1 foot of tubing in about 2 seconds (with 5/8 tubing). i would think this to be somewhat normal for a system running a whitewater and a 2-342 heatercore but i just want to make sure. The pump is a danner 3 and they aren't weak pumps so i imagine the flow would be slightly better that what it is right now. any ideas?

 

LtBlue14

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Mar 9, 2003

• Oct 12, 2003

• #2

unrelated to your post, but want to make sure you had read this thread about the mag3, so yours doesn't ever leak/crack on you.

 

OP

{BC}Helix

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• Oct 12, 2003

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• #3

i already read that thread and took the nessisary precautions to make sure it didn't leak, but thanks for making sure

 

JFettig

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• Oct 12, 2003

• #4

Yeah, 2 seconds sounds pretty close. becides its 5/8" tubing wich means that it would move even slower.

Jon

 

OP

{BC}Helix

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• Oct 13, 2003

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• #5

yeah thats what i figured, but thanks for clearing it up

 

cpufan

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• Oct 13, 2003

• #6

Hi- I ran some calculations based on your numbers in the first post.

Flow in 5/8 diameter tubing at a velocity of 0.5 feet per second, gives a flowrate of 1.8 liters per minute (0.5 gallons per minute). That seems pretty low to me, considering you are using a pump that should flow about three times that much in your system.

Are you using a bunch of fittings (Tees, Wyes, etc.)?

Reservoir?

Perhaps the bubble that you timed was not travelling at the average velocity of the fluid. (?)

 

OP

{BC}Helix

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• Oct 13, 2003

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• #7

i'm using a reservoir, and the system is externial. the tubes going to the block are about 4/5 feet long and thats 9 both ways.

 

FizzledFiend

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Winston Salem NC

• Oct 13, 2003

• #8

WHOA that alot of head preasure bud any way to shorten the lines...maybe move the pump and res closer to comp

 

OP

{BC}Helix

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• Oct 13, 2003

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• #9

well i got new numbers on theat flow rate, i measued out 1 foot on the lines and timed the water between the two points. i got 1.3 seconds. so that seems a bit better.


[EDIT]

heres a pic of the return into the res.

 

Last edited: Oct 13, 2003

cpufan

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• Oct 13, 2003

• #10

That is a flowrate of 2.8 liters per minute (0.8 gallons per minute). That is better, but still considerably less than I would have predicted.

 

OP

{BC}Helix

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• Oct 14, 2003

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• #11

i got a questions on your flowrate calculations, how exactly did you do them? what i did was take the volume of cubic inches of water in the 5/8 tube (3.68 cubic inches (PIRxRh=V)), then i took 60 (seconds in a minute) and divided it by 1.3 (the time it takes 3.68 cubic inches of water to travel through 1 foot of tubing) and i got 46.15 cubic inches a minute. then i took the number of cubic inches in a liter (61.0237441 cubic inches) and got 1.322 liters/minute. whats wrong with my math?

 

cpufan

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• Oct 14, 2003

• #12

Hi-

I calculated the cross sectional area of the flow:

Pi x radius^2= area

=3.14 x 0.31^2 = 0.31 inches^2

And the velocity:

9.2 inches/second

Then, Flowrate:

Q = VA (flowrate = Velocity x Area)

Q= 0.32 x 9.2= 2.94 in^3/sec = 176 in^3/min = 2.9 liters/minute

That should give you the right flowrate. It is certainly possible that I made a mistake along the way. Give it another go.

Jeff

 

S

Since87

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• Oct 14, 2003

• #13

cpufan said:

It is certainly possible that I made a mistake along the way.

Click to expand...

FWIW, I calculated 1.8 lpm as well, before your posted.

 

Cathar

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• Oct 14, 2003

• #14

Hmmm, measure the flow rate by filling a container of known size or something, not by judging the speed of bubbles.

Still, something is clearly going wrong. With a White Water, a heater-core and a Danner Mag 3, you should be seeing around 2gpm (~8lpm) flow rates.

 

OP

{BC}Helix

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• Oct 14, 2003

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• #15

a little while befor i wrote the above post i shotened my tubes to about 2.5 feet so 5 feet both ways, i got the following flowrate

the picture doesn't really show the "swiftness" of the water but it's really moving. but like cathar said i should just probally see how fast it fills a liter jug.

 

Last edited: Oct 14, 2003

OP

{BC}Helix

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• Nov 23, 2003

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• #16

well, I FINALLY got around to some real physical testing, and from the test i got 1.4 GPM. that good enough?