Hello, dear readers and homemade products!
Surely almost everyone is familiar with the signs of a lack of fresh air in the room. As you know, for the functioning of the human body oxygen (O функционирования) is necessary, and the “waste product” is carbon dioxide (CO₂). An interesting fact is that even while maintaining a high concentration of oxygen in the air, an increase in the concentration of carbon dioxide strongly affects health.
Most often, this problem is solved by conventional ventilation, less often – with the help of supply and exhaust ventilation. Both methods are convenient during periods when the temperature outside and in the house is relatively the same. In hot summers and in cold seasons, after airing, you have to restore the temperature in the room, spending energy on it.
In this article, the author of the YouTube channel “DIY YARI” will tell you how to make a simple and energy efficient air recuperator.
This device is a kind of supply and exhaust ventilation system. The principle of operation of the air recuperator is the exchange of heat between the outgoing and incoming air flows through the heat exchanger. Thus, the air leaving the room (for example, in winter) heats up the incoming stream.
Note that there is another type of recuperation systems. It uses heat-absorbing material (glass beads, coarse gravel) to fill a long duct. A pair of such air ducts is installed in one room, and at one point in time, air is blown out through the first, heating the filler, and through the second, air from the street is taken in, which is heated from the filler. After some time (5-10 minutes) the direction of the flows changes to the opposite.
This scheme has a lot of disadvantages. Condensation will inevitably form on the surface of the filler, and mold and other nasty things will settle with it. It is also problematic to install air filters. You will need two fans for each pipe, plus electronics for control.
The project proposed by the master is devoid of these shortcomings, is compact, easy to manufacture, and can be easily done at home. The author made a couple of parts on a 3D printer , but they can be done without it.
Materials needed for homemade products.
– PETG plastic filament for 3D printing
– Aluminum tube 8 mm diameter
– Plastic ventilation duct 110 × 55 mm
– Ventilation elbows, tees, external grille caps d100 mm, internal grilles
– PWM motor speed controller DC 6V-28V 3A
– Centrifugal fan « snail “, 12V 2.4A
– Duct fans
– Power supply 12V
– Mini digital thermometer, hygrometer.
Tools used by the author.
– 3D printer – Step drills, countersink
– Hacksaw for metal, tape measure
– Digital anemometer ANENG GN301
– Air quality analyzer (CO₂ TVOC HCHO).
So, in a hardware store, the craftsman bought almost all the components for this project.
The main elements of the heat exchanger will be aluminum tubes with an outer diameter of 8 mm and a wall thickness of 1 mm.
The thickness of the walls is very important, and the smaller it is, the better heat will be transferred between the internal and external air streams. With a smaller wall thickness, the inner diameter of the tube will increase, which will allow more air to pass with less resistance.
The components of the ventilation system were bought there – a 110 × 55mm box, elbows, tees and grilles.
Two plastic parts, which will serve as both tube holders and chamber separators, were printed by the master on a 3D printer . A model of these parts can be downloaded from the link provided by the author.
If you have there is no 3D printer, then you can order these parts in your city. You can quickly find people who provide such services on the following site.
These details are very simple and can be made from thick plastic sheet , acrylic, plexiglass. It just takes a lot of time to drill a whole mesh of 5 × 11 identical 8mm holes. Only 55 pieces.
Aluminum tubes are most often sold in lengths of 1 or 2 m. The master cuts meter-long tubes into two halves of 50 cm.
To prevent additional turbulence from creating at the tube inlet, you need to clean the ends and remove the internal chamfers with a step drill, or countersink.
Now you can assemble the heat exchanger. The ends of the tubes should be flush with the outer planes of the cassettes.
It is also advisable to seal the pipe connections with plastic parts with two-component epoxy glue, or silicone sealant.
The total weight of the heat exchanger was 1500 grams.
Tees are put on on both sides. At the same time, plastic cassettes will serve as partitions separating the outside air from the inside.
As a result, in winter, the air leaving the room passes through the round holes in the tees, and around the outer surface of the tubes, heating them. The stream from the street passes inside the tubes, and heats up, taking heat from them.
Of course, between the tees, the heat exchanger is placed in the ventilation box.
Two duct sections with elbows are connected to the main module. Here you need to immediately take into account the location of future holes in the wall, and choose the required length of the boxes.
The surfaces of the pipes can be pasted over with foil-coated foam insulation to improve thermal insulation. You can also use car noise insulation, this will somewhat reduce the noise from the street. The author pasted over the body with vibroplast. It all depends on how the system will be mounted.
So, the construction is assembled and looks like this.
The author took into account in the design an important moment of condensation formation. It will form inside the exhaust air tubes. This flow will go down through the tubes, and the condensate will flow out through the lower elbow.
You can drive air using conventional duct fans. The author decided to use 12-volt centrifugal fans “snails” in this model. They have a fairly high power (28 W), are cheaper, safer than the 220-V version, and even much easier to manage.
To measure the volume of the blown air, the master attached a plastic bag to the fan and measured the time. The measurements were carried out at different voltages. The results are in the photo.
Snails are installed in the outer grilles as follows. < br> Fan speed control can be done using simple PWM controllers . By turning the potentiometer, you can decrease or increase the voltage.
Each fan is controlled by a separate regulator, and all of them are powered by a 12-V 6A unit.
Tests are now being carried out on the volume of air blown through the heat exchanger Of course, due to the resistance of the heat exchanger, the volume dropped.
Of course, there is noise during operation. Its level reaches acceptable values at a fan voltage of about 5-7V.
To measure the efficiency of the system, the author installed sensors of a digital thermometer-hygrometer in the grilles inside the room, and measured the temperature difference.
Here are data from the first version of the recuperator with duct fans and 6 mm pipes. As you can see, the efficiency of the system decreases with an increase in the volume of passing air. This is solved by increasing the length of the heat exchanger tubes.
He measured the air flow rate using a digital anemometer, and found out that the volume of outgoing air is 1/5 more.
The same tests are carried out with the new version of the device (8 mm tubes, centrifugal fans).
Air speeds are almost the same, but overall efficiency is slightly lower.
The following graph shows the effect of CO₂ on the human body, depending on the concentration of this gas in the air.
To check the air quality (content of CO, formaldehyde, volatile substances and dust), the author uses a special analyzer . This model is quite expensive, but there is also a more affordable air quality analyzer .
These devices can warn you in time about exceeding the parameters, and the need for ventilation.
Before the start of the test, two people were in a room with an area of 30 m2 for two hours. The CO₂ level has risen from 430 ppm (parts per million) to almost 1400. At this level, performance decreases noticeably, but most often you attribute this to other reasons – fatigue, lack of sleep.
At a voltage on the fans of 5V (minimum power) to decrease level up to 480 units took 5 hours.
minimum, and there were 2 people in the room. As you can see, the CO₂ level was always within the normal range.
Thank the author for the simple design of the air recuperator!
Good mood, good health, and interesting ideas to everyone!
Subscribe on the telegram channel site so as not to miss new articles.
The author's video can be found here.
Hello, dear readers and homemade products!