FrankChong
Koi Lover
Aug 22, 2005, 11:42 AM
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Vortex filter is it worth your Ringgit?
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VORTEX FILTER IS IT WORTH THE RINGGIT ?
The process in raising Nishikigoi is both art and science. We learned from the experience of fish farmers and then we introduce scientific principles to explain why they carry out certain routine. We also use scientific principles to try to duplicate what we thought is the best environment for our koi. But still we are far from the truth. There is no pond in the world at this moment could duplicate the success of Japanese mud ponds in producing quality koi with superb skin quality. In actual fact there are still many factors involving nishikigoi husbandry could not be explained by scientific principles at this moment.
I played with Hi-Fi system all my life. Anyone would think that this is a piece of scientific equipment. I discovered it was not so after I tried to duplicate one very expensive amplifier. You can comply with every scientific principles there is on earth. But you cannot duplicate the sound quality of the original amplifier. Granted I may not have the type of resistor or capacitor they have but in science one ohm resistor is one ohm there is no scientific theory to tell you which type of one ohm resistor sounds better. What I am trying to say is science can only get you to as far as we know and there are still a lot we don’t know and cannot be explained by scientific principles. At the highest level of Hi-Fi, it became an art form. The engineer put together a piece of amplifier with the knowledge he gained from his experience and countless hours of trial and error and not from a few electrical formulas we now have. On the otherhand, if someone tries to sell you four conical shape support leg claiming it would improve the sound quality of your amplifier if you use it to support your amplifier. You cannot find any logical theory why it should work but in reality it could in some cases. Again do not be quick to write off things people do without any scientific theory, sometimes it works for reasons unknown to us. However, we have to verify and see the proof ourselves.
Similarly, if anyone claims to have found an answer or the secret to raising nishikigoi with his invention take it with a bowl of salt. Beware of snakes.
The principle behind Vortex filter
When I was a kid, I kept gold fish in gold fish bowl without any aeration nor filtration. Back then I do not know what is ammonia or nitrite. All I know is, to keep them alive I have to do 50 % water change daily. To keep the water clean all I do was to stir (with the fish in) and keep the water rotate in one direction. Then use a plastic tube to siphon all the poo that gathered at the center of the bowl. That was my first vortex filter. The principle of vortex filter is very simple, if one rotates a pool of water inside a circular container the suspended particles and sediment would move to the center of rotation. If the particles were heavier than water it would settle at the bottom of container, if particles were light it would remain suspended in water column but would always migrate towards the axis of rotation. Do not confuse this principle with centrifuge, which works on creating great G forces to act on particles by rotating tubes at high rotational speed. Particles under high G force would settle at much faster speed than gravity.
Why would particles in water always migrate towards the axis of rotation ? A particle in motion has certain kinetic energy. When the particles in water collides with water molecules and other particles it looses kinetic energy, as a result particles would always migrate towards the axis of rotation where the velocity is lower. This is one principle one can reproduce regardless whether it is in stainless steel vessel or fibreglass or in a gold fish bowl. Also regardless whether the vessel has rough surface (thick boundary layer) or ultra smooth surface (thin boundary layer) But whether the pooh can settle to the bottom of the vessel depends on its buoyancy. Heavy particles settle under gravity, light particles float, particles having similar density as water remain in suspension.
Just the other day a friend of mine asked me to help design a vortex filter based on boundary layer concept. I had to waste half a day explaining to him, vortex filter does not work that way. Boundary layer may sound high tech, but it is just a concept. No instrument is available to measure the thickness of boundary layer. Inside the vortex tank a pool of water is made to rotate by the action of the inlet pipe, which is mounted tangent to the tank. Right at the inner surface of the tank in contact with water, the water velocity is zero. A small distance out from the tank surface, water would have little velocity, then as the distance from the tank surface increases the water velocity increases. It is this little imaginary layer we termed boundary layer. The thickness of this layer can vary. If the volume of water is rotating fast the tangential velocity of water would be large. Against a fast flowing water the boundary layer would be very thin. Boundary layer is also dependent on the smoothness of the inner tank surface. Rough surface thick boundary layer, smooth surface thin boundary layer. If I have to design a vortex filter using boundary layer to trap dirt particles. I would need to have very rough surface to create thick boundary layer. What would happen is if the tank surface is made rough, the body of water inside the tank would not be easily rotated. The eddy current created would just flush out all dirt particles along the wall.
What actually happens is, we often see a dirty layer sticking to the side wall of the tank then someone concluded this is caused by boundary layer. In actual fact this is just dirt glued to the wall by the bio film nothing more than that.
This is the same principle at work in air cyclones. During my industrial training years ago I had the opportunity to work in a multi national detergent manufacturer. The process of making detergent powder involved spraying chemical slurry down a tall drying tower. By the time the wet slurry drops to the bottom of the tower it would become dried detergent powder. However, there are also very fine detergent powders that are blown upward by the exhaust fume of the drying tower. To collect these fine powder the exhaust fume would circulate through three air cyclones in series to collect / recover fine detergent dust before the exhaust fume get discharged to the atmosphere. The air cyclone works to minimize air pollution.
Is Vortex filter worth your 2 cents ?
Before I answer the above question, we have to evaluate the performance of the filter versus its cost. Can a vortex filter traps debris and fish pooh effectively ? It definitely can trap solids and garden debris such as leaves, which sink. Fish pooh ? You have to tell me !
When a fish discharge, we see a cloud of pooh coming from the anus of the fish. Have you observe how long it takes for the pooh to eventually all settle to the pond floor. A portion of it quite fast, a portion seemed never settles. If you intend to trap a portion of fish pooh that can settle, first you must measure the terminal velocity of the fish pooh. That is to measure the downward falling velocity of the fish pooh. I have never tried it but I guess we could put a couple of fish into a clean fibre tank to collect some pooh. Then drop the pooh into a meter high glass cylinder column of water. By timing the fall of the pooh one can measure the terminal velocity of the pooh. Terminal velocity means the steady state of falling velocity. When the pooh is first dropped it would fall quickly but after about 30 cm or so it should reach a steady speed. This is called the terminal velocity. With this measurement you probably would have some idea of what is the proportion of fish pooh you think you can trap with vortex filter.
Next, we have to calculate what is the uplift water velocity of the vortex filter. Water is piped in at mid level of the vortex tank. The column of water is being push upwards to be discharged at the top of the tank. To calculate the upward velocity of water column we divide the pond water turn over rate by the cross sectional area of the vortex tank.
After the dirt particles is drawn inside the vortex it has to settle by gravity. All particles which has a terminal velocity larger than the uplift velocity of water could settle. The rest of the particles would be discharged to the second vortex filter in series. For this reason many system fails to trap solids in the first settlement tank because the uplift velocity of water is high. To improve the efficiency we can have multiple settlement vortex tank mounted in parallel. If we have 3 series of tank in parallel we reduce the uplift velocity of water by 3 times.
In comparison to the conventional in ground settlement chamber, the vortex chamber is not able to do more than the law of physics dictates.
For conventional in ground settlement chamber the same law applies, i.e. the terminal velocity of the particles must be greater than the uplift velocity of water in the chamber otherwise particles would not settle. The reason we build a large settlement chamber is to achieve a low water uplift velocity to improve settlement. The law of physics dictates if the total cross sectional areas of the vortex settlement equals to the cross sectional areas of the in ground settlement chamber. Both will perform with equal efficiency.
The second chamber of vortex filter will be filled with Japanese mat. Which only means the water will not rotate or the most only the portion of water below the water inlet pipe rotate. Would the second chamber of vortex filter be more efficient than the second chamber of the in ground filter? The same law is at work here, it depends on the uplift velocity of the chamber. Rotation of the water inside the vortex chamber only works to migrate the dirt particles toward the center of drum. If your in ground chamber had a steep conical base, the dirt would also works its way down towards the discharge pipe.
In conclusion, if the vortex filter is having the same cross sectional area as the in ground filter, they should perform the same provided all things being equal. The choice of equipment one chooses would be decided by its operational ease and availability rather than by its performance.
Ideas on improvement to Vortex Filter
From my experience it is very difficult to trap any fresh waste in the settlement chamber of vortex system and in ground system. There are people fitting stainless steel wire mesh at the outlet pipe of the vortex settlement tank to help trap particles that do not settle. This would work so long as you brush the wire mesh daily without fail. ( this reminds me of the routine I carried out on gold fish bowl ) Otherwise the pores in the mesh would be blocked in matters of days by bio film, resulting in pumps running dry. The better solution would be placing a layer of Japanese mat about 4 inches below the top of outlet pipe to block large particle from escaping from settlement tank.
The main purpose of this layer of Japanese mat is to block all string algae, they are the only substance that can choke up the second and third bio tank. Let the fresh waste escape to second and third bio tank for filtration.
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Re: [FrankChong] Vortex filter is it worth your Ringgit?
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. (I've been wrong before, so if it happened again I wouldn't be shocked). 