Filters, Filters, Filters, Why aren't there any?
 

Hi all,
My latest task at my day-job involved a ductwork which had 2 sets of pre-filters Incorporated in its design to protect the inner filters of an industrial blower. The following occurred to me.

* Dust buildup inside a computer casing is the common major cause of overeating and fan failure in a computer

* Fan failure is probably the main type of computer hardware failure

* Why is there (if indeed there isn't any) no cleanable/changeable air filters Incorporated in the computer Case design?

* Why is there no market/in-market externally mountable filter box that covers the air input grills of a computer/laptop casing which hold washable/changeable air filters to eliminate the most major maintenance headache associated with computers.

Thank you for your time and input.:smile:

[QUOTE=a1call;498393]

* Dust buildup inside a computer casing is the common major cause of overeating and fan failure in a computer

* Fan failure is probably the main type of computer hardware failure

* Why is there (if indeed there isn't any) no cleanable/changeable air filters Incorporated in the computer Case design?

* Why is there no market/in-market externally mountable filter box that covers the air input grills of a computer/laptop casing which hold washable/changeable air filters to eliminate the most major maintenance headache associated with computers.

Thank you for your time and input.:smile:[/QUOTE]

1) Are Americans desperate enough for food to eat computer dust now ?

2) First thought is airflow, second is maintenance.

Airflow will be reduced but it is a calculable, simulateable (CFD) exact science. The filter "Open Area" can be made equal to the grills Open-Area resulting in negligible flow reduction. Plus in the long run the performance should be better than a dust covered grill and internal components.

I think the maintenance of filters is much more ergonomic and effective than routine dusting and vacuuming of computer casing.
Thank you for the reply SM.

[QUOTE=science_man_88;498395]1) Are Americans desperate enough for food to eat computer dust now ?
[/QUOTE]
That would be cannibalism. In case you didn't know - most of the modern apartment/office dust is ... your own skin cells.

[QUOTE=a1call;498393]* Why is there no market/in-market externally mountable filter box that covers the air input grills of a computer/laptop casing which hold washable/changeable air filters to eliminate the most major maintenance headache associated with computers.[/QUOTE]
There isn't?!
Even my 10-year old computer case has washable/changeable air filters.

Exercise: [SPOILER]type newegg.com, search "case air filter" -- you will get dozens![/SPOILER]

Thanks for that Batslov. I have never owned a PC or laptop with the"Removeable Dust Filters" that I know of.
The prices don't seem to be very prohibitive. I wonder why it's not a more common feature.

[QUOTE=a1call;498399]Thanks for that Batslov. I have never owned a PC or laptop with the"Removeable Dust Filters" that I know of.
The prices don't seem to be very prohibitive. I wonder why it's not a more common feature.[/QUOTE]
No one but the more knowledgeable users would ever clean/change the filter(s). This would cause the machine to fail sooner than letting the dust build up in the heat sinks, especially for those that don't drive their machines hard.

InWin 909 dust filter
 

I have an [URL="https://www.in-win.com/en/gaming-chassis/909/"]InWin 909[/URL] case with two fans installed at the bottom blowing up. Directly below them is a removable metal plate covered with very small holes which catch a lot of dust. The plate attaches to the bottom of the case with magnets so it can just be pulled out and taken outside to brush off. This picks up a surprising amount of dust.

That's a beautiful Machine. I would find the internal bluish LEDs problematic in a bedroom location though.
I will make sure my next PC is equipped with Removeable dust filters.
I would even invest in externally mounted filters of if they exist.

Mine doesn't have liquid cooling or the blue lights. They are just showing off a high-end build.

The one that I had for many years was Newegg's own (Rosewill = Newegg) [URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16811147107&cm_re=rosewill_blackhawk-_-11-147-107-_-Product"]Blackhawk[/URL].
I think they discontinued it, but they and CoolerMaster have many like it. And these are not really exotic or obscure brands.

I wash the filters once a year or so and let them dry. It helps because we have a cat :-)

Many cases do come with dust filters, but I still wouldn't rely on them. I am very guilty of never cleaning them until something goes wrong. Without a filter, it is more visible when you have a dust problem on the heatsink, as opposed to a hidden blocked airflow problem.

[QUOTE=mackerel;498417]... a hidden blocked airflow problem.[/QUOTE]Yeah. There should be airflow sensors. Why aren't there! :mad: [quote]Warning: The airflow in this computer is less than the design specs. Your filters are probably blocked. You may find that your cooling efficiency is reduced and see your power bills go up. Please clean the filters before it's too late. If you fail to act soon you may find that your system begins to throttle and your performance will reduce, eventually leading to catastrophic failure (and possibly death).

Press "Okay" to acknowledge this warning. Press "Cancel" to acknowledge this warning. Press "Retry" to see this warning again. Press "Help" to go to our website and view lots of advertising (but no help). Press "Ignore" to watch Armageddon unfold.[/quote]That should definitely be a thing.

There are two filter types I'm aware of, thin mesh that slides in or some smart designers attach to the case via magnetic strips, and cutouts of washable foam about 3mm thick held in place by clips that is more of a pain. You normally put filters on the intakes and leave the exhausts open.

This thread reminds me: I need to clean my computer case filters.

[QUOTE=Batalov;498397]That would be cannibalism. In case you didn't know - most of the modern apartment/office dust is ... your own skin cells.[/QUOTE]
Not exactly. Most house dust is what's left of your skin cells after they're run through the digestive tracts of dust mites (including the production of dust mite bodies). [URL]https://en.wikipedia.org/wiki/House_dust_mite[/URL]

[QUOTE=a1call;498396]Airflow will be reduced but it is a calculable, simulateable (CFD) exact science. The filter "Open Area" can be made equal to the grills Open-Area resulting in negligible flow reduction.[/QUOTE]
That's not how fluid mechanics works.
As a degreed mechanical engineer I take exception to calling fluid mechanics, much less simulation of it, an exact science. The literature is full of scatter in experimental data, for things as seemingly simple as liquid flow in a straight round pipe. There's considerable nonreproducibility and hysteresis in transitional flow.
Equal total open area does not mean equal flow conductance (flow rate per unit pressure). And even if it did, putting a filter over a grille would halve the conductance, just as putting two one-ohm resistors in series gives two ohms resistance, one half mho conductance. That means half the air flow for the same head, so unless you change out the fans for higher-head models to compensate, cooling is reduced.
Try breathing through a normal snorkel. Then try breathing through one which has that same total flow area divided into 100 passages each of which is1/10 the diameter; it will be difficult; pressure drop is 100 times greater for the same laminar flow, because while you have 100 passages instead of one, the resistance of each is 10,000 times greater (pressure/flow is proportional to 1/R[SUP]4[/SUP] for radius R for one channel of laminar flow) [URL]https://en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation[/URL]
The usual equations for orifice flow support the assumption of equal area equivalence, but the underlying restrictions on those equations include the assumption of negligible frictional losses, inviscid flow, which is no longer applicable when scale gets down to flow between individual filter fibers. As the total open area is subdivided, more and more of the total area is near a solid interface. [QUOTE]In turbulent flow regimes (Re >> 1), viscosity can typically be neglected, however this is only valid at distances far from solid interfaces.[/QUOTE] [URL]https://en.wikipedia.org/wiki/Inviscid_flow[/URL]

[QUOTE]
exact science
: a science (such as physics, chemistry, or astronomy) whose laws are capable of accurate quantitative expression
[/QUOTE]


[url]https://www.merriam-webster.com/dictionary/exact%20science[/url]


I would argue that Computational-Fluid-Dynamics satisfies the definition of Exact-Science.

Please see the "Methodology" section in the related Wikipedia article:
[url]https://en.m.wikipedia.org/wiki/Computational_fluid_dynamics[/url]

I do not believe or intended to imply that flow simulation or its related results are infallible. However, given valid/accurate input using accurate 3-D Models can yield quantitative and highly accurate results which is the 1st step in related product design only surpassed by much more expensive prototyping and flow testing.
In sciences such as meteorology you are only capable of simulation for forecasting and any actual Measurment will be after/during the fact.

As for equal resistors in series, you are quite correct,
I should have mentioned that the Open-Area of the externally mounted filter can be made much larger than the Open-Area of the grill in which case the bottleneck of the flow would be the existing grill, resulting in marginal performance reduction. Very much like 2 largely differing resistors in series. Most of the current will be a factor of the value of the largest-valued resistor. Presence or lack thereof the smaller valued resistor will be largely inconsequential.

[QUOTE=a1call;498585][url]https://www.merriam-webster.com/dictionary/exact%20science[/url]


I would argue that Computational-Fluid-Dynamics satisfies the definition of Exact-Science.

Please see the "Methodology" section in the related Wikipedia article:
[url]https://en.m.wikipedia.org/wiki/Computational_fluid_dynamics[/url]

I do not believe or intended to imply that flow simulation or its related results are infallible. However, given valid/accurate input using accurate 3-D Models can yield quantitative and highly accurate results which is the 1st step in related product design only surpassed by much more expensive prototyping and flow testing.
In sciences such as meteorology you are only capable of simulation for forecasting and any actual Measurment will be after/during the fact.[/QUOTE]

[url]https://www.youtube.com/watch?v=WepOorvo2I4&app=desktop[/url]

Just to indicate that I am fairly familiar with CFD simulation please see the animation below created by yours truly:

[url]http://apgn.19.lc/3-D/BJL-320-C.mp4[/url]

[QUOTE=a1call;498585][URL="https://www.merriam-webster.com/dictionary/exact%20science"]https://www.merriam-webster.com/dictionary/exact%20science[/URL]
I would argue that Computational-Fluid-Dynamics satisfies the definition of Exact-Science.

Please see the "Methodology" section in the related Wikipedia article:
[URL]https://en.m.wikipedia.org/wiki/Computational_fluid_dynamics[/URL]

I do not believe or intended to imply that flow simulation or its related results are infallible. However, given valid/accurate input using accurate 3-D Models can yield quantitative and highly accurate results which is the 1st step in related product design only surpassed by much more expensive prototyping and flow testing.
In sciences such as meteorology you are only capable of simulation for forecasting and any actual Measurment will be after/during the fact.

As for equal resistors in series, you are quite correct,
I should have mentioned that the Open-Area of the externally mounted filter can be made much larger than the Open-Area of the grill in which case the bottleneck of the flow would be the existing grill, resulting in marginal performance reduction. Very much like 2 largely differing resistors in series. Most of the current will be a factor of the value of the largest-valued resistor. Presence or lack thereof the smaller valued resistor will be largely inconsequential.[/QUOTE]
(Some of the following may be very familiar to a1call and is included for other readers)

I'm quite familiar with some of the computational techniques your link describes, have used FEM and finite differences, and identified for NASA software engineers some bugs in some of their FEM software. Various FEM codes developed for structural analysis or heat transfer have been extended to other analysis types, for marketing purposes, to enable linked-multiple-field analyses, and because there are often similarities in the equations for different problem types. For example, a heat transfer analysis may be done to determine a temperature field, then stress and deflection analysis to determine the combined effect of thermal stresses and externally applied loads. In some cases the properties are variable, the problem nonlinear, and iteration is required. In one analysis I did long ago involving intense heat transfer (keep this beam stop from melting while blasted with a sub-millimeter 3KW electron beam), the thermal conductivity of copper versus temperature, thermal expansion changing the shape and therefore the localized heat load, and mainly the boiling heat transfer coefficient versus temperature difference between surface and bulk were so variable, that of the change per iteration the computation predicted, I could only add to the starting temperature field, as little as 10-15%, or the solution would diverge. It took days of iterating on a minicomputer to get a believable run for a single case. Multiple cases were required to determine tradeoffs and pick design parameters. These were steady state solution attempts. I recall considering using transient analysis to aid converging to a steady state solution. Design goal was 10 year machine life. The beam stop worked for 25 years of regular use without needing replacement before the one-of-a-kind prototype research machine was decommissioned. There were a lot of things we were very careful of on that machine, at 600KV, high xray output, and narrow 3KW beam aimed at a live human's head with only a few mm of material between. The whole original design and analysis project was done without computer graphics; FEM gave arrays of numbers printed on tractor fed 14 7/8" green line paper. Then I studied the printouts, described what I saw in my mind's eye to colleagues, and hand drew graphics to convey it. Computer graphics like today's can be a real time saver for that part, and professional judgment and skepticism about inputs and outputs are always warranted. (On a separate project, I saw some student generated beautiful modeling and animation. However, they had given priority to economy over precision, neglected to consider proper tolerancing, and mistakenly set the pitch circle of the pinion at the outer tip rather than the pitch line of the rack, so the loose as-built tolerances overwhelmed the partial mesh, and the pinion and rack went in and out of mesh in the actual hardware they built, making the prototype useless and uneconomical to correct. Not so good for something delivering the oxygen to an anesthetized lab subject, rodent in this case.)

I note though, that this "exact science" link for CFD is well salted with words like simplification and approximate. The dictionary term is optimistic at best, if not hyperbole.
Calculable seems a better term than exact.

One of the assignments given us in the second required computer science class in college was to compute an integral relating to predicting the diameter of a fluid stream such as from a sink faucet, within a small per-run computing budget. After a week of effort, with best available techniques, no one knew the answer within 1%.

What saves fluid mechanics calculations is that generally engineering interest relates to some sort of average, to some acceptable inaccuracy that is often large compared to 1%, and not the localized detail of fluctuations from the average. (Engineers generally care how big a pipe or pump or fan to buy, to get a job done, not the details of the localized velocity structure versus 3 coordinates plus time. Commercially available steps in pump motor power may be 25% or larger.) Some spend considerable time in the lab with hot wire or laser doppler anemometry trying to measure, without disturbing too much, the local and time varying velocities in flows. Local variations are important in some fields, such as internal combustion engines and emissions control, where nitric oxide production rate is a strong function of local temperature and composition. (Ratios of thousands to one on cylinder average.)

Meteorological forecasts (predictions about large scale fluid flows with state change on occasion) are frequently divergent for the same forecast date/time and geographical location versus time/date when forecast is made. Usually one can trust the forecast a day or two ahead, but not always. A recent example was for US zip code 54661 recently. Successively viewed, day by day it looked like good painting weather for a recent date, no precipitation, adequate temperature. Morning of, the forecast for the same day and location had changed to rain/snow mix all day, 3C high, -1C low. Even day of, it's common for the forecast to miss the high or low temperature prediction by 3F or more. One of the local tv stations would give out an umbrella to some viewer when they missed their "4 degree guarantee" (temperature falling outside +-4F of the forecast value; 9 values total). They gave out a lot of umbrellas over a year's time. In an area where the 40-year extreme temperature range was 140F. They were unreliable hitting within 9/140=6.4% (or worse if using more reasonable seasonally adjusted expectations for temperature range) with fancy computer models.
[URL]http://www.aos.wisc.edu/%7Esco/clim-history/stations/msn/msnext.html[/URL]

Re open area ratios, the 1/R[SUP]4[/SUP] relationship will swamp some fairly hefty area ratios.