5th Annual BLF OL Comp Build. Can A Flashlight Flash? The Naked Truth. Update post 151. Night shots added. 16.12.171

SU-PER-B

I have a hunch that the fan would be more efficient (due to much less turbulence in the chamber) sucking though the holes than blowing though them.

The fan is what was available quick as there is a time limit on the build.
As for sucking rather than blowing I think it will work better blowing through the holes as the intakes will be a lot larger than the outlets. Then again maybe not. Iā€™ll just get it together and if more work needs to be done Iā€™ll worry about it then.
On a side note I may try and taper the sides of the recess on top of the fan for more of a venturi shape.

Looks great sofar!!! Following your work in awe again! :slight_smile:

Sucking is better, always.

Man I miss this stuff, feels like im peering through a window at a party I canā€™t join. Toss one back for me too, will ya?

Lovely craftmanship :+1:

The air output vents would be best adding up to the air intake area, maybe larger or thereabouts I think, plus taking in considerations for right angled bends, reducings, friction etc, there are calculations for that type of thing Iā€™m sure.
Of course I could be wrong about that as itā€™s not my field but it looks great.
Nice to see you RBD.

A good time to have a wee dram of the ever dwindling supply of Mortlach :+1: :star:

Jusht won mor

Still sitting on the edge of my chair waiting :smiley:

Cheers David

Thanks for the input Agro. I may come across a bit like that (agro) at times but dont mean to. :wink:
Iā€™m always open to suggestions.
I may have to restrict the three holes that dont travel directly under the leds as they may end up shorter in the final shape of this block. My thinking is the shorter tubes will flow more air than the longer tubes travelling under the leds which I dont think will be good.

Good to see you dropped in for a visit RBD. You are sadly missed but then you do have a life away from here. :slight_smile:
Looks like Don is about to throw that drink to you. Thanks Don.

Crx. Like your builds you have me lost, with your input. :person_facepalming: Iā€™m just a simple Moose. :stuck_out_tongue: RBD has spent a lot of time and effort explaining all sorts of topics around here to me and for some reason seems to understand the Mooseā€™s inability to communicate better than lots of others, my wife included. :stuck_out_tongue:

Weā€™re getting to the pointy-end :+1: Sorry, I canā€™t have a drink for you yet, as Iā€™m about to head off for work :nerd_face:

Your build is really taking shape.

Yes, shorter tubes will flow more air. How much? I canā€™t tell.
Cooling strength is proportional too temperature delta * airflow * cooling area.
By closing the shorter tubes you put much more more airflow to where temperature delta is higher. But you get lower total airflow (not 4 times, but much lower nevertheless) and much lower area. Is it a good idea? I donā€™t know, but something tells me itā€™s not.
It will certainly be better initially as heat will arrive in that tube much earlier than in the others.
But as the block saturates with heat, there delta T will not be several times higher in one place than elsewhere.

I believe TomE has some experience with thermal analysis of flashlights. Maybe he could tell something about the expected temperature deltas?

nice steve keep the updates coming

Some very basic preliminary tests which will be repeated when I have time to double check the first tests were correct.
With a single MTG2 mounted and run at 20 watts the temp stabilised at 45 degrees C with the air sucking through the tubes. With the fan blowing through the tubes the temp stabilised at 38 degrees C.
I have a feeling my fan will not flow enough air as this light will run around 60 watts with the leds picked and the fan will never see a full 12 volts which it was run at for testing.
Larger holes through the copper may help as it will restrict air flow less and give a larger area for the air to work on.

Surprise.
I just checked my sources, they agree with what I knew, sucking should be betterā€¦Anyway, itā€™s good that you tested.

I appreciate the input Agro.
Maybe its the size of the holes in the tubes that are just restricting to much?
I should of also mentioned that I severely restricted without blocking three of the six tubes so more airflow would travel out the tubes under the leds and the temp rose.

You have 2 sides, on 1 you have higher resistance, on the other you have lower. On the high-resistance side you create either positive or negative pressure.
Regardless of actual resistance and pressure values, positive pressure is expected to cause more turbulences and lower airflow.

Maybe the turbulences actually increase the airflow directly next to the fan cavity surface and enable better capture of heat from that place?

Beats a finite element analysis :+1:

Iā€™m sorry for offering another piece of unsolicited advice (this project is so cool i couldnā€™t help) but there might be a possibility to multiply the dissipation surface area if you did some grooves on the back side of the ā€œpillā€ and covered it with a sheet of aluminium to force the sucked air to go though it, did some painstaking modeling in solidwork to illustrate the idea:

Air would be forced through where the red arrows point

Your on the money jamesb

Surface area is king even doubling the number
Of holes and leaving the copper tubes out would
improve things.
The copper though looks pretty and adds significantly
to the frustration of the build.
Thanks for trying different ideas steve.

Where you have drawn the black lines James and they finish on the sides will either be a slot or series of holes for the air to pass through. I havenā€™t started this yet as I have to do the grooves for wiring to travel through which Iā€™m not sure where that will be until the section for the driver is completed. This will be the final piece to do.