Very interesting read. I'll be keeping an eye on this one. Might develop into a usefull new tool in fishkeeping.
Chart: Contact Time from Volume and Flow Rate
- Thread starter Jgray152
- Start date
Welp, I picked a diameter of a cylinder of 6". Since the volume does not really soly rely on the diameter but relys on the total L*W*H calculations, no matter the measurments, I figured I would be pretty safe. I found very slight variations when using other diameters compared to my 6" diameter choice.
So I used the calculator to get a velocity in the measurment of "Inches per second" at different flow rates. So 6" @ 100 GPH = ## IPS, 6" @ 1300 GPH = ## IPS.
I then figured out the length that a 6" diameter cylinder needs to be to hold a said volume, in this case, liters. I took that found length and divided it by the IPS figure which gave me the contact time at the said volume of flow according to the said cylinder volume.
Example;
20 liters = 6" x 43.18"
700 GPH through a 6" cylinder = 1.58 IPS (In/Sec)
43.18 / 1.58 = 27.33 seconds of contact time. (Supposed Contact Time)
So I used the calculator to get a velocity in the measurment of "Inches per second" at different flow rates. So 6" @ 100 GPH = ## IPS, 6" @ 1300 GPH = ## IPS.
I then figured out the length that a 6" diameter cylinder needs to be to hold a said volume, in this case, liters. I took that found length and divided it by the IPS figure which gave me the contact time at the said volume of flow according to the said cylinder volume.
Example;
20 liters = 6" x 43.18"
700 GPH through a 6" cylinder = 1.58 IPS (In/Sec)
43.18 / 1.58 = 27.33 seconds of contact time. (Supposed Contact Time)
It may or may not. Im leaning toward more of not because it doesn't seem to be accurate. The way I did the calculations is fine but its the velocity calculators that seem to be fugly.
Example;
According to the chart, the Eheim 2080 gets just about 47.63 seconds.
Well if you want to calculate 3 of them at once. That is 36 liters and roughly 900 GPH. The chart will tell you 37.04 seconds
You would think the contact time would triple. Which in reality, it would, obveously, if you have 47.63 seconds in one filter, adding two more would only multiply the number by 3.
Maybe there is a way to test it? Take your test results and somehow figure them in. Test against both of the calculators. jmo
Interesting read. I love math, although I have trouble understanding it sometimes. You've piqued my interest though.
I found your math and assumptions in the first post:
A six inch diameter circle has 28.25 square inches, not cubic inches.
The cross sectional area of the pipe is area, not volume.
I think you may have used this assumption when you entered the values for the diameter. You can't use the 'diameter' feature for calculations for a square or rectangle.Jgray152;2688642; said:
You can't compare area to volume. They are not the same. Area is two dimensions and volume is three.Jgray152;2688642; said:
A six inch diameter circle has 28.25 square inches, not cubic inches.
The cross sectional area of the pipe is area, not volume.
Jgray152;2688642; said:
Ahhh...there it is. That didn't really give you 'contact time'. But I see your line of thinking now.Jgray152;2705360; said:
You got calculations for a solid flow of water through an empty pipe. In a wet sump or canister, the media takes up space so the empty volume is less than an empty pipe. To get the same volume through a smaller space, the velocity has to be increased.
In a wet/dry sump, the problem is compounded because there is a significant amount of air between the media. Additionally gravity, viscosity, and friction are going to play a part in the final equation.
Correct, I was going to put this in my first post but figured it may not have been very important since we can not EXACTLY figure the actual contact time.
You also bring up a good point, don't know why I didn't think about that. The contact time in that sence would actually be less. I suppose the real way to figure this out is to find out how much volume of a specific media take up in a given volume space.
Agree with the wet sump as well. Well, it was a shot, but didn't hit the target.
You can. Volume is volume so a sqaure volume can have the same volume as a cylinder of certain dimensions. I perfomed an equation to do this too but I forget it. Its probubly not very accurate.
A 6" diameter cylinder that is 10.80" long equals 5 liters. I am not saying 6*10.80, saying, 6" by 10.80".
Ah, I know this. Opps, another late screw up, welp, if you had a volume of 28.25 in a cylinder that would be the same as 3.02 cubed
You can, I think you missed it.
1 liter = 61.02 cubic inches therfor, 5 liters = 305.1 cu/in (61.02*5)
305.1 / 28.25 = 10.8"
To find out the length of a cylinder when you only have the area and volume. You need to take the cubic inch volume and divide it by the area which equals the length.
If you use online calculators, you can see that a 6" diameter pipe which is 10.8" long will equal 1.32 gallons which is equal to 305.1 cubic inches
No, I mean you can't use the calculator for square shapes. The diameter is only for round pipes. You have been very loose with units and terminology. Something in your description or calculations indicated that you had used 6" in the calculator for a sump six inches across.Jgray152;2705633; said:
