90degrees best for jet impingement?

Gulp35 · 04-29-2003, 01:28 PM

http://cpdl.kettering.edu/jiht.html

I found this article and they found that say that about 70degrees make the best angle.

What I think it is, is that the windshield is angled 20degrees so that when at 70degree jet a 90degree angle is formed, but I am not sure because there isn' that much interpretation of the graph.

bigben2k · 04-29-2003, 01:46 PM

More importantly, how does this relate to watercooling a PC?!? More specifically, what relation do you see with that information?:shrug:

airspirit · 04-29-2003, 02:03 PM

I see the relationship. If you angle the barb/jet at 70 degs to the baseplate, you can (by his data) get better results. This only works, though, in cases with one inlet and one outlet. In cases where there are two opposing outlets like WW (or my project for that matter) this wouldn't work. It also wouldn't be optimized for using ridges or fins like WW, and would only work on pin style configurations.

This makes absolute sense as it would allow the old coolant to be cleared from "ground zero" more effectively than direct 90 deg impingement. How to utilize it effectively is another matter altogether.

bigben2k · 04-29-2003, 02:17 PM

Yeah but look at the Reynolds rating of the tested flows: 5'000, 10'000 and 20'000: our pumps don't do that, unless that's a turbulence rating at the surface of the windshield?!?

[edit] For those interested, here's the very relevant, accompanying text (PDF, 15 pages).

[edit2]...and the 4 page primer.

airspirit · 04-29-2003, 03:32 PM

I'm just playing devil's advocate here, not suggesting a change in design philosophy.

Nooge.

bigben2k · 04-29-2003, 03:35 PM

Note that the whole experiment is for AIRFLOW, not waterflow.

Alchemy · 04-29-2003, 03:39 PM

Seems Ben is learning.

One does not look at a pretty picture and jump to conclusions about what the picture means.

I don't think anyone could realize without reading the article that this simulation was for *air flow* and thus serves no purpose for waterblocks. Although, looking at the realm of Reynolds numbers in the charts should have been a clue.

Their theoretical equations seem right, if it helps anyone.

Alchemy

airspirit · 04-29-2003, 04:22 PM

I would imagine that water would provide similar result (having NOT read the article, looked at the graphs, or anything). Both results are probably going to be similar because both of them probably are caused by the same thing: clearing out the old and bringing in the new balanced with maximal pressure against the target area.

bigben2k · 04-29-2003, 04:59 PM

The (big) paper claims that an angle of 75 deg provides maximum heat transfer, but does make a note that the airflow is restricted at the bottom of the "windshield", by the "dash". At least, that's the way I read it. Anyone else catch this any different?

LiquidRulez · 04-30-2003, 01:19 AM

Well ,most us understand how it means nothing for our uses Ben...
Hes talking about a none submerged jet of water ,shooting into the wind

versus a submerged jet impingment creating velocity and forcing the boundary layer into a smaller envelope, and thus bring the thermal resistance down, to acheive a lower C/W.

bigben2k · 04-30-2003, 05:38 AM

Quote:

Originally posted by LiquidRulez
Well ,most us understand how it means nothing for our uses Ben...
Hes talking about a none submerged jet of water ,shooting into the wind

versus a submerged jet impingment creating velocity and forcing the boundary layer into a smaller envelope, and thus bring the thermal resistance down, to acheive a lower C/W.

No, it's not even water at all! It's the air vents at the edge of the dash, that defog the windows!

04-29-2003, 01:28 PM	#1
Gulp35 Cooling Savant Join Date: Sep 2002 Location: Atlanta, GA Posts: 135	90degrees best for jet impingement? http://cpdl.kettering.edu/jiht.html I found this article and they found that say that about 70degrees make the best angle. What I think it is, is that the windshield is angled 20degrees so that when at 70degree jet a 90degree angle is formed, but I am not sure because there isn' that much interpretation of the graph. __________________ Epox 8RDA+ v1.1----------Tyan K8SDPro 1700+ JUIHB 0310XPMW (12.5x200Mhz@1.792v)--------2xOpteron246 (2Ghz 1MB L2) 2x256MB Kingston PC3000 (BH5?) 2-2-2-8 2.7v---2x512MB Corsair Reg.&ECC PC3200 ATi Radeon 9800Pro (stock, too hot)-----ATI RageXL WD800JB+WD2500JB-------WD1600JD Sony DVD/CDRW-------NEC 3520A Black Forton350W--------Antec TruePower2.0 550W EPS12v

04-29-2003, 01:46 PM	#2
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	More importantly, how does this relate to watercooling a PC?!? More specifically, what relation do you see with that information?:shrug: __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

04-29-2003, 02:03 PM	#3
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	I see the relationship. If you angle the barb/jet at 70 degs to the baseplate, you can (by his data) get better results. This only works, though, in cases with one inlet and one outlet. In cases where there are two opposing outlets like WW (or my project for that matter) this wouldn't work. It also wouldn't be optimized for using ridges or fins like WW, and would only work on pin style configurations. This makes absolute sense as it would allow the old coolant to be cleared from "ground zero" more effectively than direct 90 deg impingement. How to utilize it effectively is another matter altogether. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

04-29-2003, 02:17 PM	#4
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Yeah but look at the Reynolds rating of the tested flows: 5'000, 10'000 and 20'000: our pumps don't do that, unless that's a turbulence rating at the surface of the windshield?!? [edit] For those interested, here's the very relevant, accompanying text (PDF, 15 pages). [edit2]...and the 4 page primer. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

04-29-2003, 03:32 PM	#5
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	I'm just playing devil's advocate here, not suggesting a change in design philosophy. Nooge. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

04-29-2003, 03:35 PM	#6
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Note that the whole experiment is for AIRFLOW, not waterflow. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

04-29-2003, 03:39 PM	#7
Alchemy Cooling Savant Join Date: Oct 2002 Location: Boston Posts: 238	Seems Ben is learning. One does not look at a pretty picture and jump to conclusions about what the picture means. I don't think anyone could realize without reading the article that this simulation was for air flow and thus serves no purpose for waterblocks. Although, looking at the realm of Reynolds numbers in the charts should have been a clue. Their theoretical equations seem right, if it helps anyone. Alchemy

04-29-2003, 04:22 PM	#8
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	I would imagine that water would provide similar result (having NOT read the article, looked at the graphs, or anything). Both results are probably going to be similar because both of them probably are caused by the same thing: clearing out the old and bringing in the new balanced with maximal pressure against the target area. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

04-29-2003, 04:59 PM	#9
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	The (big) paper claims that an angle of 75 deg provides maximum heat transfer, but does make a note that the airflow is restricted at the bottom of the "windshield", by the "dash". At least, that's the way I read it. Anyone else catch this any different? __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

04-30-2003, 01:19 AM	#10
LiquidRulez Cooling Savant Join Date: Sep 2002 Location: In Hell Posts: 322	Well ,most us understand how it means nothing for our uses Ben... Hes talking about a none submerged jet of water ,shooting into the wind versus a submerged jet impingment creating velocity and forcing the boundary layer into a smaller envelope, and thus bring the thermal resistance down, to acheive a lower C/W. __________________ GOt H20 ?

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