Has anyone done any research on reversing the airflow? AND even putting the fan on the other end and pulling the air through?
https://bitcointalksearch.org/topic/m.43446447Re: Z9 list of working pools/Fork updates
Today at 04:55:03 AM
Reply with quote +Merit #637
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https://preview.ibb.co/modtYz/IMG_20180803_090110.jpghttps://preview.ibb.co/nCEHtz/Screenshot_2018_08_03_08_55_10_483_com_android_chrome.pngI only reversed the airflow
My temps at 750mhz:
Before: 67-71° at 80%
Now: 54-59 at 70%
Is it possible that your fan had been set the wrong way from the factory? Can you confirm which direction the air flows now after you switched? And how about sound, did it change in any way (especially the pitch)?
The fan used to suck air in, now its blowing out. Speed is about 1k rpm less.
To avoid confusion, it pushed air in, now it is pulling air out, correct?
correct
I actually just tried this out and now my fan is pulling air out (blowing out and not through the machine) and my PCB temps dropped 9-11 degrees per PCB and about 4-6 degrees per chip. Fan on auto also it spinning about 1k RPM lower and doesn't do the constant up and down ramping when I had it the other way. Seems strange they wouldn't try this configuration and ship it that way...
Pulling air is a better method of cooling. Proven in data centers, A/C units,.. I will be moving my fans to the back of the unit and the blank metal plate to the front of the unit in my data center on Tuesday and give a report on it.
A/C units pull air because the coil is very close and larger than the fan and an even air flow through the coil is desired.
Also be carefull when pulling air over uneven coil as in the Z9 mini, the air will flow more with the least resistance areas, if you push air and the coil/ fins are close like the Z9, the static pressured air will not have time to find another course through the fins. In other words its better to push in on the Z9.
I just took the Z9minis and put them into the garage with the fan on the back end. The first two are of them running with the fan on the front pushing the air (original). The second two are them running with the fan on the back pulling the air through.
---FAN ON THE FRONT---https://i.imgur.com/8LTEUYf.jpghttps://i.imgur.com/3PrT67Z.jpg---FAN ON THE BACK---https://i.imgur.com/3j2azZU.jpghttps://i.imgur.com/6lnaiIB.jpgWhat did you do with the rear grill and fan grill?.
I put the entire grill that was on the back onto the front. I took the fan and plate from the front and put it on the back.
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Ok, a couple of things to think about.
The original fan setup pics show that the fans are stepping in speed, this is a good thing, as the chip temp changes the fan adjusts. is the suction fan stepping, if its not and is constant thats not good.
The fan speed changes with pcb sensor, not completly sure if the temp chip sensor engages fan speed, could be secondary limit. Either way the drop in fan speed between the suction fan setup is due to lower pcb sensor temp, not necessarily from a better setup.
Have a look at the heatsink setup, the top of the unit has little restriction, and air can flow easily through this area, also the left side is board no 3 (bottom sensor) it has always the hottest readings, but it should be the coolest you would think, why because it flows more air near it, notice the gap between the board and the side case, a good 15mm, now have a look at the other side, board no 1 top sensor its always the second hottest and you would think it would be the hottest, it has less space than the rest, its jammed against the side wall.
This is a good example in the original setup of static pressure forcing air into the restricted board no 1, where as board no 3 the static pressure on the fins are lost and escapes around the 15mm gap in the side wall, more air passes but its hotter.
Im being objective here only to theroise what is happening with suction setup.
Nowing the air will suck easly through that big 15mm side gap and through the single fins at the top of the unit and through the gaps between the boards and swirl the air causing a pcb and chip temp drop. As i have suggested in the first post with the sensors being at the rear, The reason i suggest this is i have been able to reduce the pcb temps by redirecting the air and forcing it to flow closer to the sensors.
The suction setup could be good, i'm just not confident that its better due to all the factors in play, some ways you could improve the unit without changing the fan setup, firstly remove the rear grill and put it aside. second, remove the fan grill, i made a new grill like a mouse cage and fitted it over the fan approx 50mm deep, also raise the unit off the table so the air can go through the cage bottom into the fan. third make a thin metal plate, best if i send a pic its a bit complicated, the plate improves pcb temps and brings down board no 3 now board no 1 is the hottest, its working well for me hope it does the same for you.
https://imgur.com/suA5T9qhttps://imgur.com/EOK7lxd