[AT] Airflow calculations of perforated metal for radiator screens

Fri Jun 18 06:09:37 PDT 2021

I got a $20 handheld anemometer from Amazon I use for measuring airflow
now. Takes the guesswork out of it. I got it when my son built a wind
tunnel project for school and now I use it when working on cooling
calculations for my RF generators. Well, that and my pawn-shop FLIR camera.
Now you can get a FLIR add on for a cell phone too. I got the FLIR when I
was working on a 200kW RF system and for some reason I didn't want to put
my hand in it to see where the hotspots were. Handy tools. :)

Now I'm trying to figure out how to upgrade my old R-12 based R4 compressor
to a more modern and efficient Sanden compressor on my 86 Blazer. Of course
it worked when it was cooler but now that we're in the mid teens it's not
keeping up. Around 118 and I had 90 degree air coming out. bleh. Already
upgraded the fan clutch to the big-block version and that helped but that
was before the heat got here.

Ken in AZ

On Fri, Jun 18, 2021 at 5:46 AM Cecil Bearden <crbearden at copper.net> wrote:

> Steve:
>
> I remember all that and had to work with it in hydrology and flow
> calculations for the last 40 years.  However for the last 10 I have had a
> computer program available that does all that stuff and all I have to do is
> plug in some numbers.  Back when I was approving plans for new
> construction, I could look at an applications, the spillway size and the
> location and ddo it in my head....
> Cecil
> On 6/18/2021 4:55 AM, Stephen Offiler wrote:
>
> I haven't done flow calculations in a long, long time, and Fluids was not
> among my favorite subjects back in school... so with that said, my gut
> feeling is that Mark's 56% blockage is probably somewhere in the right
> ballpark but dependent on factors like whether the airflow is laminar or
> turbulent, maybe Reynold's numbers.... now I'm just spewing stuff I learned
> 40 years ago.  Mostly to say, there might not *be* a good way to calculate
> this outside of a lab with a flow bench; really, the thing to do is try it,
> and take measurements.  No idea if you can see high-side pressure while on
> the road but I doubt it.  Any readouts for coolant or trans temperatures?
>
> SO
>
>
> On Fri, Jun 18, 2021 at 1:03 AM magreer67 <magreer67 at gmail.com> wrote:
>
>> Wouldn't that be 56% blockage and 44% open to flow through?
>> Mark Greer
>>
>>
>>
>> Sent from my Verizon, Samsung Galaxy smartphone
>>
>>
>> -------- Original message --------
>> From: Cecil Bearden <crbearden at copper.net>
>> Date: 6/17/21 11:34 PM (GMT-05:00)
>> To: at at lists.antique-tractor.com
>> Subject: Re: [AT] Airflow calculations of perforated metal for radiator
>> screens
>>
>> The .188 diameter staggered pattern gives .444 sqin hole area over a 1 sq
>> in area.  So I guess it would result in a 44% blockage.  However it would
>> be tabout 5 inches from the grille and then the A/C condensor sets about 6
>> inches back from that.  I think there would be sufficient room to pull air
>> from above and below.  It just may cause some additional drag at high
>> speeds.  I think I will try it and make it easy to remove in case it blocks
>> too much airflow.  I have to do something.  Time and ability to work on
>> this stuff gets more valuable daily...
>> Cecil
>> On 6/17/2021 7:48 PM, Brad Loomis wrote:
>>
>> The 455 diesel lawn tractor I use at work has a pull out screen ahead of
>> the radiator. I'm not there so I can't measure it. But I will try tomorrow
>> and report back. It does keep the foxtails, thistle, mustard, and whatever
>> else I kick up out of the radiator.
>> Brad
>>
>> On Thu, Jun 17, 2021 at 5:23 PM Cecil Bearden <crbearden at copper.net>
>> wrote:
>>
>>> I had to wash the A/C condensor and radiator out on my 2011 Chevy truck
>>> yesterday before I could make a trip to pick up some auction items.   I
>>> put the gauges on my a/c system and it showed 35 low and 350 high.
>>> before I did anything I went to the water hose and got it down to 150
>>> pretty quickly on the high side.  The amount of bugs was crazy.  I will
>>> have to remove the radiator and condensor to get them clean as there is
>>> no room to get anything in the front or behind the fan.   I have one of
>>> those heavy cowcatcher style grill guards in the front.  This truck has
>>> about 170K miles and has made 3 trips to Alaska, so it may have more
>>> bugs than usual, but the bugs and thi8stle seeds are terrible here and
>>> getting worse.  I want to put a piece of perforated metal behind the
>>> grill guard to catch the bugs. If it cuts the air down, it can still
>>> come in between the screening and the grill.  I don't think it will make
>>> a lot of difference in the amount of air entering the radiator, but
>>> maybe catch the bugs and fluffy crap in the air...     When we figure
>>> airflow into a home, we cut the flow through a window in half when a
>>> screen is used.    I am looking at a peforated metal with holes .188in
>>> in diameter and offset centers so it gets the most holes per square
>>> inch.   Does anyone have any experience with this type of screening or
>>> have a formula to determine if it will cut the airflow too much. I think
>>> the area behind the grill guard and the grill is wide enough to keep
>>> from cutting down the air flow.  Traveling down the road at 60mph it may
>>> deflect some air around the grill instead of through..
>>>
>>> I just don't want to have to remove this radiator again.  I have to use
>>> a stepladder to work on the d&%$^d thing it is so tall.  It is stock for
>>> that year, but the manufacturers want to see how far the drivers can
>>> jump to get into a pickup nowdays.  I remember a 63 and 66 chevy 1/2 ton
>>> pickup we worked out of on the farm every day.  Hauled 20 head of cows
>>> in a bumper  trailer with no brakes into OKC Stockyards.  Loaded 60
>>> bushels of wheat to haul to the elevator when the lines were long and
>>> the grain truck had not returned.  Now, I have a 3/4 ton that I have to
>>> jump into or pull myself in with the steering wheel and 30 bushels of
>>> rye in the bed causes it to squat, with twice as much tire under it than
>>> the old ones had..   It doesn't ride all that much better,  just cooler
>>> when the A/C works.   OK  rant off.....
>>>
>>> Cecil
>>>
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>>
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