Theory of Fine and Micro Bubbles
If you drop a stone from a height, it will fall very quickly to the ground. If this same stone is crushed, the larger pieces will fall faster, smaller ones more slowly. However, if the stone is crushed into the fine powder, air will blow the dust more far and wide, some pieces will spread and fly for several days in the air. If the same stone can be crushed into molecular dust, it would go into the eternal movement of air currents. But the weight of dusty air will always be equal to the specific weight of air plus the weight of the stone from which the dust is formed. It follows that the dusty air is holding near the ground until all the dust particles would not fall to the ground. A good example is the smoke in the cities, smoke microparticles increase the specific gravity of air, so it stays close to the ground. You can imagine the same with an air bubble in the water. The bigger is the air bubble; the faster will come to the surface. The smallest is the more slowly will rise. This rule applies to molecular size. Therefore, the specific weight of water can also be adjusted with the microbubbles.
If We have thermoclines pool at the bottom of it is 4 C but on the surface is 10 C. 1m3 of water at 4 C weighs 1000kg, 1m3 water at 10 C weighs about 999.7 kg. If we want to eliminate such thermoclines, we need to put in the cold water more than 0.3 liters of air in the form of microbubbles per 1000 liters of water. This cooler water mass at least for some time will slowly rise to the surface. So the new water from the bottom of the pool will always come back to the aeration area.
Microbubbles also have a small defect. Transfer of gasses between them and the water is complete within a few seconds, and from now on they have only the function of the lift. Some scientific experiments show that the ideal size of the air bubble is 2,2mm. In laboratories, that may be true, but in practice, it is almost useless information. My argument is that every pool has their particular characteristics, so we always need to adjust the quantity and especially the ratio of the size of air bubbles for a particular pool.
Air or oxygen transfer?
Many manufacturers mix these two concepts and thus mislead their customers.
Air transfer: if the aeration basin using a compressor with a capacity of 1 liter of air per second and it is powered by the power of 1kW. We can say that the transfer is 3600 liters of air per kWh. This coefficient does not vary with the size and shape of the aeration basin. It is a constant determined by the manufacturer and on energy efficiency, it says nothing.
Oxygen transfer: this is the actual transfer of oxygen, which can be subsequently consumed by organisms in the water. What will it be this transfer, depends not only on the air compressor but more than many other factors. The form, size, air and water currents, temperature, amount of organisms, shape and arrangement of diffusers of a swimming pool and many other factors are also imperative. If in such aeration tank using a compressor with the power of 3600 lit / h, and oxygen tester measures the amount of oxygen in the bubbles coming out of the pool, we get a basis for the calculation of oxygen transfer. For example, an oxygen tester Shows 18% of oxygen in the outlet air bubbles; we get the information that the oxygen transfer shows 108 lit. O2 / kWh, or about 150g. O2 / kWh.
These figures apply only to this configuration and to this environment, and cannot be considered as general technical data for the manufacturer, but only as an example of energy efficiency in a particular environment.
Air aspirating turbine
In the development of the oxyTurbine, it was important that we will transform at least 5% of the air into the microbubbles and the remaining air into bubbles of standard dimensions (1 to 2.5 mm). It has been shown that the optimum depth for this ratio is between 1.5 m to 2 m. Due to the adverse effects of greater depth, it was determined that the optimum working depth of the turbine on between 0.6 and 1.2m. With pools deeper than 2 m and the ratio between the depth and length more than 10m, it is necessary to set the turbine in the buoyancy tube. The buoyancy tube should be wide between 700 and 900mm. Buoyancy tube should be raised from the bottom around 500mm, and the same must be below the surface. It is recommended that at both ends are slightly extended. With this system we make the movement of the water in the entire pool, thereby it will cyclically move the whole water through the aerating tube.
If above the pool blows strong enough wind, we can shut down one turbine. With this method, we can speed up the movement of the water in the pool since both systems push the water in the same direction. It is important that works only the turbine, one from where the wind is blowing.
Here it shows the same phenomena as in the C2, with the difference that there is wind blowing in the opposite direction, so here the turbine is activated at the other end of the pool. If above the pool will blow some very strong wind, the oxygen tester will show a high percentage of oxygen coming out of the pool. In this case, we could also turn off the turbine because the wind is aerating the water in the pool sufficiently.
Each pool or lake has its particular characteristics, so for this is necessary to determine empirically the regime of operations of aeration systems for each pool individually.