Need some help with math ...

[friendlyAlien]

Hi,

So I am trying to figure out my real water flow from the basement sump to the aquarium. I am re-using som unorthodox plumbing ...


The sump is about 200 gallon and the main tank upstairs the same.

All heaters are in the sump. Raising the water temperature bygone degree through the sump/ return loop takes 68 minutes the temperature in the sump fluctuate between 79 and 80 degrees and the target temperature for the display was 79.

Now I know I should be a able to deduce the flow rate from between display and sump but nothing I scribbled on paper so far makes sense (and I have a crumbled up pile worth mentioning - anyone need fire starters?)

Any help would be highly appreciated!!!

 

[Haffs09]

What size plumbing are you using? How many unions, valves, 90s, etc... are there? What pump are you using and have you looked at its flow curve?

On my system, I have a main return pump that feeds, the DT, skimmer and a refugium. Initially, I estimated 17' of head, but that didn't include effects from supplying the skimmer and fuge. I used a P3 Kill-A-Watt meter to see that my pump drew 295W. Comparing that to the flow/watt curves, I found my system ran at ~22' head (I can't remember the exact amount) and delivered ~1800gph.

 

[Randy Holmes-Farley]

This calculation is quite tricky and requires a lot of assumptions that will likely make it more error prone than other methods (like collecting the return water for a minute or two and see how much it is, etc).

The problem is that as soon as a little water transfers from one to the other, both tanks change temp, and even if you assume instantaneous perfect mixing in each, the analysis is nontrivial. There is a standard tank mixing problem solved with differential equations, but I'll leave it to the math majors if they really want to solve it for a case like this.