🌑 Как сделать АКУСТИЧЕСКИЙ ХОЛОДИЛЬНИК или Холод из пробирки Thermoacoustic cooler Игорь Белецкий

How to make an acoustic refrigerator, or even better, an air conditioner. By the way,

I recently saw news online about such a device. I think this topic will be

very relevant at the beginning of summer. Today I will explain how it works and

show the cooling effect on simple models that skilled craftsmen can replicate at

home if they wish. Let's start with the simplest. I have already shown an experiment

on thermoacoustics with a regular test tube. If you place a small piece of steel

wool in it and heat it from one side, then due to the resulting temperature

gradient, sound vibrations arise, the frequency of which directly depends on the length of the

test tube. The longer it is, the lower the frequency, and vice versa.

This is a primitive model of a thermoacoustic engine, which in turn is a type

of Stirling engine, and therefore is reversible. In other words, if we heat the steel

wool from one side and cool it from the other, we will get air vibrations

or mechanical energy at the exit of the test tube.

And vice versa, if we supply a sound wave to the input of the test

tube, we will get a real heat pump. The place where we heated will now

be actively cooled, taking energy from the environment, and the place we cooled will heat

up, and this heat needs to be dissipated for the pump to work efficiently. There

are already videos online where a regular speaker is connected to such a test tube

and a temperature difference of several degrees is achieved. But I won't do that because

I don't have a powerful speaker, and a small tweeter is useless. I will do

it differently. We take our test tube and, using sealant, glue a plumbing adapter to

it. Then I will need a glass syringe. I happened to have such a beauty

lying around, waiting for its hour. I was very lucky that it completely disassembles and

its front part can be

removed. After that, I also glue an adapter to it.

Now we screw everything together and place it on a stand. The idea is to

create an air pressure difference inside this system by moving the rod with the piston

by hand, and thus make the heat pump work.

This is not a pure sound wave, of course, but the principle is roughly the

same. Unfortunately, I could not achieve any noticeable effect this way, obviously due to the

low frequency. And I decided to mechanize the process. I turned a new piston out

of graphite.

It should move freely inside the syringe with minimal clearance. This

is not an easy task, but I have experience. At the same time, I immediately

checked the design for tightness and

operability by running it as an engine from a piece of solid fuel. Excellent.

The piston is connected to the electric motor by a connecting rod, and the oscillation

frequency increases. This is another matter. Using an electronic pyrometer, I can measure

the temperature difference at the ends of the metal filler. In the future, I will

call it a regenerator. The room temperature was 24 degrees, and a difference of about

15 degrees was formed at the ends of the regenerator. In such a primitive experiment,

I didn't bother with heat dissipation.

Although this would certainly improve the performance of the heat pump. You can check. And

I'm just demonstrating the effect to you. Using a longer test tube, you can significantly

improve the result and lower the temperature at the cold end of the regenerator more.

This is because for each length of the test tube, there is its own ideal

frequency of air

vibrations. And unfortunately, for these small test tubes, it is significantly higher than what I

could provide with this homemade mechanical air oscillator. To further lower the temperature, and in

general to make the structure more efficient, it needs to be coiled into a ring,

or something like that.

For those who remember, a little over a year ago I showed something similar, namely

this model of

a thermoacoustic generator. A link to the video on how to make it from almost

nothing will be at the end of the video.

And since this is a reversible engine, it can easily be turned into a refrigerator.

I didn't bother redoing this model, as it was easier to make a new one.

Now let's briefly analyze its operating principle as a refrigerator. As you can see, it's

just a ring pipe filled with ordinary air, a steel wool regenerator, and an inlet

through which, using a piston compressor, we will increase and decrease the pressure inside the

system, i.e., simulate sound vibrations. The only part that distinguishes this design from the test

tube is an elastic membrane, which plays the same role as a flywheel in a

conventional engine, because the air inside the system will move back and forth in a

circle. To make it easy to monitor the temperature drop, I installed a temperature sensor

from a regular multimeter and connected it to the cold end of the regenerator. I

think a few words should be said about the regenerator itself, as the most important

part of this device. In this model, it is made of the finest steel wool,

also called "zero-grade". The parameters of the regenerator, such as fiber thickness, density, material, and

length, are very important for the efficient operation of the refrigerator and depend on both

the frequency of air vibrations and the

dimensions of the installation, particularly its diameter. Therefore, the process of selecting a regenerator takes

some time, without which it is simply impossible to achieve good performance. This time, I

will use an aquarium compressor as the source of pressure oscillations. I managed to get

a very successful model. If you remove the front cover with the check valve, which

we won't need anyway, you will see a 45 mm piston that moves back and

forth under the action of electromagnets inside the housing. A very simple and reliable design.

The only thing I had to modify again was an adapter that allowed me to

quickly connect the compressor to the installation and also quickly remove it. This was very

useful when I was experimentally selecting the optimal type of regenerator. Let's see how this

homemade refrigerator works. The initial temperature of the cold end

of the regenerator, like the room temperature, is 24 degrees. After turning on the compressor,

it starts to decrease quite rapidly, about a degree per second. This is a very

good result. But starting from about 15 degrees, the drop noticeably slows down. Each subsequent

degree takes more and more time. For the temperature to

drop from 10 degrees to 9 takes 15 seconds, from 9 to 8 it takes

20 seconds, and so on, increasing. In principle, this may be normal, given the simplicity

of the design and the power of the compressor. Unfortunately, the minimum temperature I managed

to achieve with this model is only 0 degrees. Not much, of course. I hoped

to go about 10 degrees lower. I found the design of this model to

be not ideal, mainly due to the corners where the air moving inside inevitably encounters

resistance and loses some of its energy. Therefore, I decided to make a new model

from a piece of 20 mm metal-plastic pipe. The idea was to bend it into

a ring to reduce energy

losses due to friction and thus achieve higher performance. Otherwise, the design remained exactly the

same. Let's see how it works. We start as before from 24 degrees. The temperature

begins to drop, almost as quickly as in the previous model. But then the drop

still slows down, and

no significant difference in readings is observed. I'm still stuck at the 0-degree mark. What's

the

matter? Upon closer inspection, you can notice that starting from 10 degrees and below, condensation

forms on the glass where the cold end of the regenerator is located, both inside

and outside the test tube. This did not happen with the first model because it

had a glass with a wall thickness of 2 mm, but here I used a

test tube with a wall thickness of only 0.5 mm. It conducts heat better, naturally.

From all this, I can conclude that moisture actively condenses on the tiny fibers of

the regenerator and simply clogs it, preventing free air passage. As a result, the regenerator

simply stops working properly. This is my personal opinion. Perhaps you will find another reason.

Then write to me in the comments or by email. Although, if you

think about it, 0 degrees is not that little. It's perfect for an air conditioner.

The design is extremely simple. No mechanics inside. Easily scalable.

Can be made from plumbing plastic pipes. Works on ordinary air, not freon. No leaks.

Eco-friendly. Add a fan and blow cold air into the room. A great idea for

a startup. For those who want to build a trial experimental model themselves, look at

how I did it. The main assembly points are visible here.

If anything is unclear, there will be a link at the end of the video

to the video on assembling the thermoacoustic generator that I showed more than a year

ago.

There I explained all the subtle points of this design in

detail. I hope you learned something new and useful for yourself today. Subscribe and you'll

know even more. There's a lot of interesting stuff ahead.

Don't miss it.