Calculating pressure drop?

m3_arun · 12-08-2002, 08:07 PM

hello.
im thinking about getting into watercooling (as some already know) and ive come across a vital question.
Is there a way to calculate head loss/pressure drop in a given system (at a given flow rate)? this will aid in selecting a pump.
the system im thinking about is one with cathar's cpu block, a heater core, and either 1/2" or 5/8" tubing.
thanks.

murray13 · 12-08-2002, 10:21 PM

That's the million dollar question. But, to answer your question, no there is no easy way to actually calculate flow or head.

I wish there was, as do most of the people here.

The best that can be done is to look at the individual components. But some of them do not have any good information on them. You can calculate loss and flow for the tubing that you will use, but since that is only a small part of the system it only helps.

The biggest limiting factor in selecting a pump is how much your willing to spend.

IMHO if your willing to go around $145 then a Iwaki WMD-30RLZT is the way to go. 4.6 GPM max flow, 36.1 ft max head, ~29 ft head @ 3 GPM for only ~47W = 1/16HP.

m3_arun · 12-08-2002, 10:35 PM

i heard that the wmd's are no good...
thats not good news...
i was hoping that i could get a pump that would give the best compromise between rad/wb performance

m3_arun · 12-09-2002, 10:31 PM

is it possible to calculate the head loss for each component then add them up or something?

Albigger · 12-10-2002, 08:22 AM

Quote:

Originally posted by m3_arun
is it possible to calculate the head loss for each component then add them up or something?

in theory i believe this works, if you are calculating for the same flowrate?

Not sure, someone can clarify hopefully. but still, calculating for the waterblock and radiator would be difficult, i imagine.

From what I hear the Iwaki's with the japanese motors are the best

bigben2k · 12-10-2002, 09:13 AM

Quote:

Originally posted by m3_arun
is it possible to calculate the head loss for each component then add them up or something?

Yes.

You have to add each item as a length of a certain diameter or, in the case of some waterblocks and odd elements (heatercore), find their hydraulic equivalent.

You also have to consider surface smoothness: a rusty iron pipe can have twice the restriction of a smooth PVC pipe.

m3_arun · 12-10-2002, 07:43 PM

is there any site or anything that details how to do this? do you have any idea what the pressure drop is for most radiators.
thanks a lot.

Albigger · 12-10-2002, 10:53 PM

here's a site for calculating single pressure drop in pipes of certain diameter, i'm not sure how much it really applies, but here it is:

http://www.processassociates.com/process/fluid/dp_1.htm

and a "general" idea of some common pressure drops for radiators might be obtained from an article by BillA at overclockers.com not sure of the name, maybe someone else can provide a link.

of course if you are using a non-conventional rad. it might not be too helpful

m3_arun · 12-10-2002, 10:54 PM

thanks very much, thats pretty much all i need.

Blackeagle · 12-14-2002, 02:23 PM

The Iwaki pumps are about as good as I've found. I'm doing much the same as you are, trying to choose components for a new system. The thing is there are 2 types of Iwaki pumps.

The WMD denotes the pump has a american moter and cooling fan. These are louder, hotter and shorter service life, but at a savings.

The second type is the japanese moter: quiet, cool running, long service life, but higher cost.

If you get the japanese built type they have a differant designation of MD instead of WMD at the beginning of the model #.

The best price I've found for a MD-30RLZT is $208.00 so far.

m3_arun · 12-15-2002, 01:28 AM

what store is that? also how bout the 20rzt?

thanks

murray13 · 12-15-2002, 09:29 AM

m3:
Try this place out. These are the best prices I have found for Iwaki pumps.
Customaquatic

Dan_Dude · 12-15-2002, 07:02 PM

Well I can't really answer your first question but I'm currently using a whitewater block with a heater core and 1/2in clearflex 60 so i suppose I can give firsthand advice on this. Im using an eheim 1046 with this setup and its giving me temps of only 9C above ambiant measured with the oh so inaccurate motherboard sensor. A beefy pump should not be required by your setup.

m3_arun · 12-16-2002, 10:09 PM

thanks dan_dude.
do you have a flowmeter in your system? this would allow us to consult the power/flow curve for the eheim 1046 and derive the pressure drop for your system (i think).
thats the same system im hoping for except for the pump which im trying to decide on right now.

12-08-2002, 08:07 PM	#1
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	Calculating pressure drop? hello. im thinking about getting into watercooling (as some already know) and ive come across a vital question. Is there a way to calculate head loss/pressure drop in a given system (at a given flow rate)? this will aid in selecting a pump. the system im thinking about is one with cathar's cpu block, a heater core, and either 1/2" or 5/8" tubing. thanks.

12-15-2002, 07:02 PM	#13
Dan_Dude Cooling Neophyte Join Date: Oct 2002 Location: Living it up on Long Island (zero good comp stores) Posts: 8	Well I can't really answer your first question but I'm currently using a whitewater block with a heater core and 1/2in clearflex 60 so i suppose I can give firsthand advice on this. Im using an eheim 1046 with this setup and its giving me temps of only 9C above ambiant measured with the oh so inaccurate motherboard sensor. A beefy pump should not be required by your setup. __________________ You know that shitty ass software, VFD Thinger? I wrote that. Now you know who to bitch to. Get it at: http://jgsr.mine.nu:233/vfd/

12-08-2002, 10:21 PM	#2
murray13 Cooling Savant Join Date: Sep 2002 Location: Omaha, NE USA Posts: 216	That's the million dollar question. But, to answer your question, no there is no easy way to actually calculate flow or head. I wish there was, as do most of the people here. The best that can be done is to look at the individual components. But some of them do not have any good information on them. You can calculate loss and flow for the tubing that you will use, but since that is only a small part of the system it only helps. The biggest limiting factor in selecting a pump is how much your willing to spend. IMHO if your willing to go around $145 then a Iwaki WMD-30RLZT is the way to go. 4.6 GPM max flow, 36.1 ft max head, ~29 ft head @ 3 GPM for only ~47W = 1/16HP.

12-08-2002, 10:35 PM	#3
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	i heard that the wmd's are no good... thats not good news... i was hoping that i could get a pump that would give the best compromise between rad/wb performance

12-09-2002, 10:31 PM	#4
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	is it possible to calculate the head loss for each component then add them up or something?

12-10-2002, 07:43 PM	#7
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	is there any site or anything that details how to do this? do you have any idea what the pressure drop is for most radiators. thanks a lot.

12-10-2002, 10:53 PM	#8
Albigger Cooling Savant Join Date: Sep 2002 Location: ohio Posts: 140	here's a site for calculating single pressure drop in pipes of certain diameter, i'm not sure how much it really applies, but here it is: http://www.processassociates.com/process/fluid/dp_1.htm and a "general" idea of some common pressure drops for radiators might be obtained from an article by BillA at overclockers.com not sure of the name, maybe someone else can provide a link. of course if you are using a non-conventional rad. it might not be too helpful

12-10-2002, 10:54 PM	#9
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	thanks very much, thats pretty much all i need.

12-14-2002, 02:23 PM	#10
Blackeagle Thermophile Join Date: Oct 2002 Location: U.S.A = Michigan Posts: 1,243	The Iwaki pumps are about as good as I've found. I'm doing much the same as you are, trying to choose components for a new system. The thing is there are 2 types of Iwaki pumps. The WMD denotes the pump has a american moter and cooling fan. These are louder, hotter and shorter service life, but at a savings. The second type is the japanese moter: quiet, cool running, long service life, but higher cost. If you get the japanese built type they have a differant designation of MD instead of WMD at the beginning of the model #. The best price I've found for a MD-30RLZT is $208.00 so far.

12-15-2002, 01:28 AM	#11
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	what store is that? also how bout the 20rzt? thanks

12-15-2002, 09:29 AM	#12
murray13 Cooling Savant Join Date: Sep 2002 Location: Omaha, NE USA Posts: 216	m3: Try this place out. These are the best prices I have found for Iwaki pumps. Customaquatic

12-16-2002, 10:09 PM	#14
m3_arun Cooling Neophyte Join Date: Oct 2002 Location: san jose, ca Posts: 91	thanks dan_dude. do you have a flowmeter in your system? this would allow us to consult the power/flow curve for the eheim 1046 and derive the pressure drop for your system (i think). thats the same system im hoping for except for the pump which im trying to decide on right now.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)