Stefan Stojanovic

CEng PhD test development engineer.
Learning about air cleaner design.
Tweets,RT,♥=Opinion
❌Endorsement/professional advice
Mastadon @[email protected]

[Stefan Stojanovic @PlasticFull]

https://t.co/9T5BGEaEwf

[@CleanAirClassrm is on Bsky @CleanAirClassrm]

Download the Storyboard Build Document
https://t.co/ZyccnSdrzf

DIY #CRBox #AirCleaner Testing by @PlasticFull

Thx
@JimRosenthal4 @CorsIAQ @JbcLiftec

For more info #CRBox and #AirCleaningDevices
@CleanAirCrewOrg
@CleanAirStars
https://t.co/1ZIE4zAf1e
https://t.co/sNxmhIQzIE

[Stefan Stojanovic @PlasticFull]

@CleanAirStars @mishwoz @CleanAirClassrm @DouglasBooker @nathan_wood_8 @hugx4pets @BESAGroup @EllaRobertaFdn @HenryBurridge @CamdenCleanAir @KAPlastics @ventilationpro @JimRosenthal4 @CorsIAQ @jljcolorado @MumsForLungs @robwiss Yeah they will be higher resistance than Filtrete mpr 1900. Lower cadr. Larger difference between smoke and dust/salt cadr. Slightly higher noise than Filtrete.

Min speed of that fan would be same as vent axia fan on max speed >50dba. Can be sourced from JASUN filters in UK.

[Stefan Stojanovic @PlasticFull]

@adsquires Faced choice as teen with friends in car.

Brakes failed leaving motorway.

Happened so fast.

Engine breaking & handbrake not enough 📉

Ditching was terrifying, costly, friends confused, screaming 😱

Bruised, no complaints after.

Better than stopped cars or roundabout t-bone.

[Stefan Stojanovic @PlasticFull]

@DavidElfstrom @sri_srikrishna @AltenbergLee @built_envi Face velocities vary greatly across the panel too. Highly non uniform. Biased to one side typically and show patterns that indicate static pressure waves that I think are driven by fan blade passing frequency and quarter wave resonances.

Best to test whole unit at sub micron.

[Stefan Stojanovic @PlasticFull]

@SprkJoy4BtrDays @PeteUK7 @SharonBurnabyBC Simple answer is mini purifiers are far from ideal shaped like a traditional purifier/Cr box.

Unless in a small space like a car.

Best to blow at you, through a filter, if flow is low. Qt3 is ok for that.

Will share test results of cheaper slim & short, plug in builds soon.

[Stefan Stojanovic @PlasticFull]

@TomPMarshall @fearnley_k @KateCushing2 @guardian Being stuck on waiting lists with potential post covid symptoms is depressing.

[Billy Hanlon @bhanlon15]

"YouTuber "Physics Girl" dealing with long COVID as her sister helps from Denver"

"I can't talk...I can't move," said Cowern in a video on Facebook"

@thephysicsgirl

https://t.co/9wA6iy2jF9

[Stefan Stojanovic @PlasticFull]

@ianwrob @DavidElfstrom Think it's todo with fake reviews. Not sure. This purifier is rebranded under many names anyway. Like Russel Hobbs in UK. Good feedback. All from same original manufacturer's. I've tested it personally, passed data to @CleanAirStars and have donated to family and schools.

[Stefan Stojanovic @PlasticFull]

@SmartAirFilters @PeteUK7 @EPA Will be case specific & need testing.

It's so complex in terms of flow dynamics that can't make generalisation between different geometries. Why CFD used to model and tweak designs for HVAC applications.

Eg vane axial tube fan (cannon) & simple axial (box) fan v different.

[Stefan Stojanovic @PlasticFull]

@RealSexyCyborg Hard to spec test without a threshold. Id guess standard purifier test chambers going to be difficult to differentiate residual environment particulates vs shedding at low p/cm3. Needs recirculation to be representative. True clean room / environmental chamber could maybe do it🤷

[Stefan Stojanovic @PlasticFull]

@AltenbergLee @sri_srikrishna @JbcLiftec There's also https://t.co/kMu8jireoh but I don't know how reliable their results are. Filtrete performs well with good durability and structural rigidity during our tests. Why I decided to specify that to avoid variability in performance.

[Stefan Stojanovic @PlasticFull]

@RealSexyCyborg Not sure how to test it without equipment like ashrae has. Will have to dig into literature. I know in my rough chamber, plantower neph reads zero across all particle counts eventually with filtrete. But that's orders of magnitude higher than ashrae paper p/cm3 resolution.

[Stefan Stojanovic @PlasticFull]

@AltenbergLee @sri_srikrishna @JbcLiftec tested aerostar in EU and found high filtration Vs spec on a flat piece of material. High resistance though, very coarse pleats and glue at edges came away easily. I wouldn't recommend them.

[Stefan Stojanovic @PlasticFull]

@CleanAirStars @robwiss @eddericu @JimRosenthal4 @CorsIAQ @JbcLiftec @DavidElfstrom @Stoffel78179983 @CRBoxKits think should stick to EPA11 with these fans close to a single filter. Epa12 of IKEA may be too close to hitting pc fans limit or have no headroom for filter loading. Could be wrong if more power fans used.

[Stefan Stojanovic @PlasticFull]

@RealSexyCyborg Wonder if it's single radial blower open both sides? Trend of quieter high flow units designed that way. Open both sides radial blower means higher flow, less prone to high pitch resonating, but typically lower pressure capability. Which 2 filters compensates for.

[Stefan Stojanovic @PlasticFull]

@RealSexyCyborg Wonder if there are studies on MERV in similar way with pre cleaned air.

There are different design points for Merv vs HEPA in terms of pressure vs flow.

CR box is much lower than typical MERV13 use, eg 10 pascals or less delta pressure. Around 0.5m/s face velocity.

[Stefan Stojanovic @PlasticFull]

@eddericu @sri_srikrishna @ee_kelsey Stators good for boosting pressure, at expense of noise, narrowing outlet flow in pull config.

Rule of thumb for boosting axials
-bell mouth inlets
-outlet stators
-tubed outlet to media.
or
2 in series

Bigger media certainly helps. keep to EPA11 like QT3 or sqair.

[Stefan Stojanovic @PlasticFull]

@RealSexyCyborg At what level of microplastics release should we be concerned?

The ashrae study reported very low counts 👇 Without recirculation back through the filter.

For context I end DIY smoke tests below 1 particle/cm3 due to resolution, below 1ug/m3 on a standard pm2.5 sensor.

[Shiven Taneja @ShivenTaneja]

I collaborated with @PeteUK7 to create a step-by-step guide to building a #CorsiRosenthalBox in the UK. Thank you to @PlasticFull @mishwoz @hazardscampaign @LibDemPatrick. You can download the PDF here: https://t.co/frKrK6UUUA.

[Stefan Stojanovic @PlasticFull]

@ShivenTaneja @PeteUK7 @mishwoz @hazardscampaign @LibDemPatrick @CorsIAQ @JimRosenthal4 Great job, thank you so much!