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Hood low noise Bernoulli for gases

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Added 32 commentary
Hello !

I want to talk about my homemade based on a fan (cooler).
Hood low noise Bernoulli for gases


I decided to make a hood for soldering.
I wanted it to be not noisy, productive enough and at the same time the outlet pipe would be small in diameter so as not to drill huge holes in the walls.

I decided to use the fan that is used in computers.
Why? They are brushless, so little noisy, quite productive and durable.

At my fingertips was this:



Thermaltake
Power 12 V, consumption 0.13 A. I was of little interest.
I needed to know its performance.
And I went online, on the fan brand TT-9025A, I found 56 CFM.
CFM is an Old English measure of water flow rate. Cubic Feet per Minute.
But, it applies now to the air flow, to the fans, for example.
I came to the conclusion that 56 CFM is enough for me for this installation, especially since this cooler blows well, I knew from the previous work with it.

Decorative - protective lattice to him I had, I found it. The fan is powerful enough, high-speed, the impeller has seven blades and easily cuts fingers. As it turned out later, this grill helped me understand how to achieve a positive result in the manufacture of this hood.



Some base was needed to mount the components of the hood.
The choice fell on a rectangular plaque for of furniture. I used to collect my homework on this plate. Four glued shock absorbers from the packaging material of the Chinese laser pointer are visible.


According to my idea, a tin plate and a tube with a diameter of ten millimeters were required so that they could be soldered. I saw the cover from a disassembled, outdated, CD-ROM drive and a frame dowel with a knocked-down thread.

Sharged from this the output part of the hood. Roughly cut the drive cover with scissors for metal. Straightened with pliers and a hammer. I marked holes in the piece of iron for the tube and for connecting to the fan. He screwed and drilled holes with drills of the required diameters.

I cleaned the edges of the hole for the tube and one end of the outer part from the useless frame dowel. Soldered the tube to the piece of iron. I applied the so-called solder fat. It solders steel parts well. And it does not spread, like some other active fluxes. The fact that the parts are steel, first checked with a magnet.

I soldered with two soldering irons at the same time, since it is difficult to warm the glands. He heated 80 watts with one soldering iron, and 40 watts, in fact, soldered with another. After cooling the structure, the remnants of solder grease were washed off with solvent 646. I checked the strength of the connection and if there were any gaps around the circumference of the solder.

There were slots in the tube from the frame dowel (according to the principle of its operation). The drive cover also had slots and holes for various purposes. I shook it, sealed it with electrical tape.



When I was wondering how I would assemble the structure, the first thing I did was carefully examine the cooler from the sides. On one of them I found arrows showing in which direction the fan wheel rotates and where it is blowing. Accordingly, I brought the power wire to the side and additionally secured it with a clamp.

After that, he laid out all the components in series, according to his idea of ​​creating this hood. Then he connected them with screws. Self-tapping screws had to be selected different in length and thread. Screwed and twisted them more than once.

After that, using small metal corners and wood screws, I fixed the entire structure to the base.

The most exciting moment has come. Test the installation in action.

According to the polarity of the cooler wires (as usual, plus - red), I connected my laboratory power supply to it, after setting the voltage to 12 V.

The fan began to spin. First of all, I brought a sheet of A4 paper to the decorative - protective lattice. He was attracted to the grate. So, everything is assembled correctly.

After that, I brought the sheet to the output tube. The sheet declined. That's right too. But, he deviated very weakly. I do not need such a hood.

Then I began to conjure with holes and crevices. It:

Slots in the joints of the components of the installation, holes in the decorative-protective grate. I reliably glued everything except the grill with high-quality electrical tape.

Strange, but the hood began to work worse. Then I began to peel, sometimes cut off the electrical tape.

The results changed randomly.
I began to come to a standstill.

And, suddenly, I remembered the Bernuli law!
Which says that in liquids and gases, with increasing flow velocity, its pressure decreases. And vice versa.

I realized that I need to make a smooth adjustment in some way, and by glueing and unsticking the electrical tape I will achieve nothing.

In the center of the decorative and protective grille, I drilled a hole commensurate in diameter with the inner diameter of the outlet tube.

And he made a special, adjustable damper or gate valve, and you can call it that.




I took a fairly elastic plate from some alloy, from a disassembled technique.
I cut the desired shape with scissors for metal. At one end of the plate, I drilled a hole for mounting. I wrapped the plate with electrical tape and glued a pad of elastic material that caught my eye.

For a long time I bent the plate in every way, trying to ensure that the damper overlapped a large hole in the center of the decorative - protective grille to the necessary degree. In this case, the damper must not spontaneously change its position. For this, we need an elastic plate and pad.

As a result, it turned out. The damper made it possible to very accurately regulate the ratio of incoming and outgoing air flows.

Moreover, I managed the incredible! Make the fan designed strictly for blowing, without changing the direction of rotation of the impeller, without moving it in the casing, work on suction!

The blades spun in the same direction, and the cooler sucked in air!

I decided to make sure that this is not a dream.
He put a fingertip on the output tube and tightly wrapped it with electrical tape. In one position of the damper, the fingertip inflated, that is, overpressure was created in it, and in the other position of the damper it contracted - in it a vacuum was created. When the fan power was turned off, the fingertip took its usual form (the pressure in it equalized with atmospheric pressure). At a certain position of the valve, with the fan running, there was no air movement, which does not contradict the laws of science.

I have a video of this test. I am enclosing screenshots from this video with my explanations:

Rear view of the installation


A fingertip is put on the output tube


High pressure inside the fingertip


Inside the fingertip


Flap adjustment process



With a sharp change in the position of the valve, due to changes in the speed and pressure of the air flow, there was a short-term, peculiar sound, similar to smacking. When working in normal mode for hood or suction, the fan was almost inaudible, even when I was nearby.

Now I will show a simplified installation diagram.


1 - output tube, a flexible hose of small diameter is connected to it, which is displayed outside the premises.

2 - plate

3 - fan (cooler)

4 - decorative - protective lattice

5 - adjustable shutter

The arrows indicate that the air can move in both directions or not move at all (depending on the position of the damper).

After some time, I decided to improve this system. Its dimensions will decrease, and the noise level will not change, the power will increase. I know how to achieve this.

I hope you were interested in familiarizing myself with my homemade product and, based on the foregoing, make something like that.

Sincerely, author.
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32 commentary
0
Reply To quote A complaint
I talked about the effect when the wind blows directly into the pediment, in which the windows are already inserted and closed (or there are none at all), and the wind is not clogged.
By the way, I came across such an effect of "pneumatic accumulator" in this case:
They decided to make an office out of the old warehouse at the factory. The ceiling was hung from PVC panels. After some time, the ceiling was torn off and hung, bent down "whole sheet". Restored. Somehow I went into this room, I see - the ceiling is a "bubble", but until it comes off. I tried, screwing it on the table, fasten it with several screws with a wide hat, in the center, raising the “bubble” ... When I broke it, air came from hissing ... Then I noticed that it comes from the cracks around the perimeter (from under the baseboard ) I went outside, examined. The building is a panel board, bricked. From above they did not report to the very end tightly. ("Leaving" under the overhang of the roof, it is not visible there). It was autumn, the wind blew for several days in one direction, right into this wall. And, resting, he blew up into a "trap" between the wall and the overhang of the roof. Apparently, there were cracks in the wooden shields. When plasterboard was lined to the ceiling from the inside, all this air could only penetrate into the slots that were above the ceiling (between the old ceiling and the new suspended ceiling) and the wind “pumped” this cavity until the ceiling pulled out. The panels are fixed with a stapler. Foamed on top. All. More did not fall.))))
0
Reply To quote A complaint
Do not forget that on the reverse side, depending on the form, a vacuum will form. As a result, two forces tear the roof, increased pressure from the inside, and rarefaction from the outside. Moreover, it is vacuum that works to a greater extent from the outside, because how to “pump up” the attic is not so easy)))
0
Reply To quote A complaint
Don’t correlate, you need a very revolving motor so that you can drive a large amount of air through a tube of small diameter.
Author 0
Reply To quote A complaint
Dmitrij, the goal of this our work is to create without valves. FROM valves anyone can.
0
Reply To quote A complaint
If you do not put a valve in front of him, he will not be able to work! A “hanging” water column will heavily load the impeller.


When the pump is running, the water column in any case hangs, and not only hangs, but also moves in the opposite direction)) And it’s hard because of the airing, of course, the air then “stretches”, it's like air in the brake system of a car.The valve is only needed to hold water in the pipe after the pump is turned off, it does not help the pump in any way, on the contrary it interferes, as it creates resistance.
0
Reply To quote A complaint
It is easier for the pump because it needs to create excess pressure in a small cavity, and not in a huge reservoir, which is a mattress.


He is absolutely violet where to create pressure. If he created pressure, it’s already hard for him. It will give its maximum both when pumping directly, and through valves or diffusers ... The valve farts due to the equalization of pressure between the tanks.

But there may be nuances in the design of the compressor, there is no arguing without a design photo. If there are few blades, or the outlet opposite the blades of small diameter, the air flow can go jerky, then when the blade leaves, part of the air can go back, thereby reducing the efficiency. Maybe, but it's all about the design.
Author 0
Reply To quote A complaint
Thanks, Dmitrij. By the way, when I fell asleep, the idea came up about the desired ratio of the diameters of the input and output tubes.
0
Reply To quote A complaint
Here on this prince tears off roofs if the wind board is not beaten. It really happens. If the wind (even weak) for a long time blows in one direction, and directly into the pediment, then through the gap between the slate and the pediment he manages to "pump" the attic to such an extent that, at some point, the entire slate is "explosively" bursting out .. Not literally all, of course. Just a few sheets with the weakest nails - and there the pressure drops sharply. At the same time, it’s interesting that even the same gap on the other hand does not save, although it would seem that through it it can exit as much as it enters ...
I think the effect is based on the energy of large masses of air (or liquid).
For example, now I am welding a heating system in the house. It is interesting that if one very strong exhale blows into a 32-pipe (PPR), which is only some 60-70 meters long, but with a large number of turns, then we get such an effect. First, we blow it like in a closed pipe (like in a rubber chamber))), at some stage, when the exhalation of our lungs becomes weaker, we even get a backward blow inflating the cheeks)))). Then the air begins to come out of the return, so much so that in the end our lips begin to suck in the supply pipe!)))). That is, the accelerated mass of air, without stopping, leaves and creates FOR YOURSELF (!!!) a vacuum. (I’m talking about a very strong exhalation. If you blow a little, the pressure manages to equalize and there is no such effect).
I was even scared that somewhere "brewed" the fitting and a diffuser formed. But, a professional plumber said that everything is correct, it will be so !!! And the truth is - after filling, the circulation pump easily, at the slowest speed, shifted the entire mass of water and there was no "plug" there.
0
Reply To quote A complaint
That's why I wrote "figuratively speaking." I said that the “fart” valve begins only at the end. That is, when the pump can swing easily, it is always open. But when it is already squeezing back, it closes, while the pump continues to pump into the chamber in front of the valve. When a bit exceeds the pressure, it passes the excess, and closes again ... The pump is easier because it needs to create excess pressure in a small cavity, and not in a huge reservoir, which is the mattress.
This is why it will not work, it’s not a hydraulic ram))) The system will simply “air” when the pump is turned off.

I am not familiar with ejector ones (I said), but with the usual sign it is very, very good ... If you do not put a valve in front of it, it will not be able to work! A “hanging” water column will heavily load the impeller.
Even if the valve passes a little (so that the airing of the pump comes in a few days) - it is already very difficult for the pump !!!
So I recently wrote that I was changing the opposite at the dacha ... My father-in-law called me and says that the hydrophore is abruptly, somehow straining, buzzing, and the productivity has fallen - you open the hose, the jet hits first (while the receiver is pumped up), and then it is sluggish sagging ... I was symptomatic and realized that the valve was "dead." Took off - for sure. The sand hit, scratched and it back a little "blowing". Replaced.The pump immediately became more fun.))))
I don’t know, maybe in the “impeller” pumps there is some kind of “reverse fluid swirl” that interferes with them if you do not periodically block the inlet, but all the pumps are “more fun” if you put a valve at the inlet. As it turned out in my case with air - and at the output too.))))
+1
Reply To quote A complaint
Here is an example, the "power" option and the "volumetric".

In the first case, the pressure inside the fan housing will increase to the maximum that the fan can give out. And then this flow will more or less evenly go into the tank, slowly filling it. The output of such a tube (in the absence of a reservoir or other load) will be a high flow rate.

And the second case is volumetric, the load on the motor and the pressure inside the fan grows as the tank fills. The fan output is volumetric, the flow rate is lower, and under load the flow rate will be generally minimal.
0
Reply To quote A complaint
But is it nothing that the already pumped air into the tank prevents the valve from opening? The valve does not reduce the load, it increases it.

This is why it will not work, it’s not a hydraulic ram))) The system will simply “get air” when the pump is turned off.

By the way, if the height difference is less than 9-8 meters, then I will not be “airy,” because the ejector is worth it))) That is the valve is generally not needed.
Well, if more, the water will boil from a drop in pressure
0
Reply To quote A complaint
He did not increase power. He unloaded the impeller. After, figuratively speaking, one blade pushed its portion into the tank, the air does not press back and does not prevent the next blade from delivering its portion ... By the way, your hydrophore will not work without a valve either ...
+1
Reply To quote A complaint
Yeah, but I didn’t understand how the valve increased the compressor power)) Well, put a valve on the vacuum cleaner, and what, does its power somehow change? In general, nothing, the valve will only add. output resistance. Although he may have narrowed the way out, the result was a more "power", but less "volumetric" compressor. Those. the case works like a receiver, IMHO ...
Author 0
Reply To quote A complaint
Valery successfully develops the topic. I already took the idea into service. No doubt, Dmitrij did the same thing. drinks drinks drinks xaxa
+3
Reply To quote A complaint
Inflate the fingertip, the ball with a fan, not a compressor. Nobody has thought of such a thing.

And I, here I’m inflating a boat and mattresses with a Chinese pump, once bought for a long time roofing felts in Dino-Direct, roofing felts on DilExtreme ... I only remember that Ali Express was definitely not there then ...
The pump, as it turned out, contrary to the assurances of the Chinese that it could inflate almost receivers for production lines, I couldn’t inflate anything in the stock version!))))
Having disassembled its “non-separable” case with a knife and a hammer, I found out that there was just an impeller with a 12 volt motor inside. The impeller, however, is rotary (and not a fan), but this does not change the essence. On each blade I glued a piece of varnished fiberglass a little larger (so that the protruding parts a little "scratched" along the body). The flow intensified, but ... the impeller is the impeller! Slightly in the inflated reservoir the pressure increased - and that’s it! Zatyk !!!
Added a self-made check valve at its output with rubber petals that deviate freely from the flow, but tightly block the return flow !!!
Fathers are holy !!! It was almost possible to inflate the wheels in the car !! .... Only the valve at the end farts very loudly!)))) ... A kind of alarm ... When I put up the tent, the mattress is pouted ... When I get carried away, the valve fart reminds that my mattress is already almost round!))))
+1
Reply To quote A complaint
R555
We will compare prefixes ... maybe it will reach balloons.
I suggest
through a narrow tube
and at the output a whistle, who has louder
I’m quite seriously saying ... Nobody has thought of such a thing (except me)
xaxa
+1
Reply To quote A complaint
In the hood, volume is important, not suction, and smoke exhaust.
Author 0
Reply To quote A complaint
Initially, I did it under a hood for soldering, so as not to make a lot of noise and to let out smoke through a narrow tube (at the exit to the street). This is so as not to drill holes 15 centimeters in diameter in the walls. Well, then, when I got the desired effect, I thought about how else I could use this operating time. And as for the motor, I think so. We put someone at hand and for their tasks. It’s not about the motor - the fan, but the prefix to it. Prefixes and we will compare. Like to bring pieces of paper to the entrance and exit, to inflate fingertips, maybe it will reach balloons. I’m quite serious. Inflate the fingertip, balloon fanrather than a compressor. Nobody has thought of such a thing (except me) xaxa Most importantly, it partially worked out. Tomorrow I will slowly begin to assemble a new installation. And the name has already been invented.
0
Reply To quote A complaint
Installation for what is needed, for soldering? Let's. I also need a hood, I solder stained-glass windows and other home-made products ... But I need to decide on the basis of what, which motor? Or no difference?
Author 0
Reply To quote A complaint
Even when the shutter is completely closed, small gaps remain through which air continues to circulate. For good, I need to finalize the article. And it did not reflect many important points, it is not clear to everyone. I wrote in the comments that I have a video about the test of this homemade product, but I swear very much there with joy that I did it. xaxa I want to remove the sound, transcode (to take to the site) and show. Then it becomes clear the seriousness of this homemade. But, in general, I just need to finalize this installation. It’s normal, lucid to present the material, show more photos and videos. Post under a different name. And let's Dmitrij , arrange a contest whose installation will work out better. drinks I propose to appoint independent judges Korolev and Ivan_Pokhmelev
+1
Reply To quote A complaint
Well, like a hell))

Using the damper, you create a load on the fan, thereby increasing the vacuum inside. The smaller the inlet diameter, the higher the suction flow rate.
Well, yes, the fingertip will be inflated, and what, isn't that the idea?

In general, these propellers work shitty on suction, in general, suction is a parasitic phenomenon that reduces efficiency by half when looking at paddle propellers. Such screws make sense for helicopters and airplanes, where on the one hand the pressure rises and on the other it drops. Take a closer look at the profile of the cooler blades.
But since everything is in the casing, and the air comes out by forcing it to the outlet, it is logical that its absence should be compensated for something through the suction.

But why is it rarefied? Your shutter is closed, there is no way to suck the propeller from, and therefore it cannot blow.
The fan will spit out a certain amount of air, so the pressure inside will be lower than outside, that's all mysticism.
+2
Reply To quote A complaint
do not insert
Rake +3
Reply To quote A complaint
At your advice, I decided to check and oh my God, I lost a finger on my left hand after I inserted it into the blades of a computer cooler!
Moreover, it was not possible to sew a finger back; the finger was cut like a sliced ​​sausage.
Guest Serge 0
Reply To quote A complaint
Have you tried it yourself? Only so easily, I almost have to sew up.
Author 0
Reply To quote A complaint
Vladislav Balykov! Fold a sheet of paper into a tube and put it into a working computer fan, but it’s better to immediately finger and tell us whether it was chopped or not. After that, continue reading my article on the hood.
Vladislav Balykov +3
Reply To quote A complaint
Will a computer cooler hit your fingers? After such a stupid statement, I did not even read further.
0
Reply To quote A complaint
About 30 years ago I wanted to make an influx of fresh air into the bedroom. The brick wall is thick. A thick tube with a narrow fan from a hair dryer. It’s also heated, since it’s cold in winter and the windows are closed ... It didn’t work, of course. Calculations for ventilation and the rest in the air have been done for a long time.
"... and the real pressure drop was in the right direction." And what was the difference measured?
He made ventilation (only influx) in the bedroom of a panel house. Through the loggia. There was no ventilation at all ...
Author 0
Reply To quote A complaint
Pronin! I say, it worked for you, not just a muzzle, but a real pressure drop was in the right direction. I disassembled, showed everyone, now I improve. I can’t show the original video, I swear there with surprise because of the results. I can only show the scientific commission that they too will immediately start swearing in surprise ...
+1
Reply To quote A complaint
You simply set the output to the resistance ... The hood will not work.
In order for it to work according to the proposed scheme with a channel fan, you need to make a channel ... and at the output put a gearbox with a smaller hole ...
Guest Igor +1
Reply To quote A complaint
collective farm chervone drawbar
+2
Reply To quote A complaint
Ivan_Pokhmelev
The cooler is a radiator with a fan
Cooler (from English. cooler) - literally translated as a cooler. Essentially a device designed to cool a heating element.
An ice bucket in which the divine drink (champagne) is also so spectacularly and solemnly served as a cooler
A rare situation in a poker hand, in which a very good combination of cards comes into your hands and your opponent is even better. There’s no reason to drink champagne anymore, it remains to drink a cup of chamomile tea brewed using a water cooler (dispenser, water heater, water receiver, water cooler)
smile
0
Reply To quote A complaint
this cooler blows well
examined the cooler from the sides
A cooler is a radiator with a fan.

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