Confirm Parallel Radiators = 1/2 Flow Rate

Purchased most of the stuff, just need to confirm a theory to decide on ordering a 2nd pump to put in series.

I'm using Martin's spreadsheet and calculating the estimated flow rate. Let's say, 0.5 GPM to keep it simple.

When running two identical radiators in parallel (all things being equal to y-splitter and tubing, etc), this cuts the flow rate in half for each radiator, correct?

So, each radiator would have a flow rate of 0.25 GPM, correct?

I'm thinking of instead of increasing pump speed, that I'll go with Skinnee Lab's recommendation of running two pumps in series to keep the noise down. As noise is my #1 concern with this build (you can litterly hear a pin drop in my office, and I aim to keep it that way).

Two pumps in series gives me about an 80% increase in flow rate (per Martin's spreadsheet). Makes sense.

Thanks in advance!

I don't think it's as simple as cutting it in half, no. There are a lot more factors to those fluid mechanics that I'm not educated enough to figure out. My uneducated guess would say it loses about 1/4 of the flow as opposed to running them in series, but that is literally just a guess.

That said, why wouldn't you just run the radiators in series?

If it's all equal, yes. A .5gpm flow split to two radiators gives each one .25gpm.
However like Hokie said, you lose flow rate running series as well, in the high heatload world of car radiators and charge coolers you never run in series if you can avoid it, you lose a lot.
That's a different world however.

Thanks guys. Not talking about series what-so-ever. They are in parallel, no choice. So, with a given flow rate, each rad gets 1/2 the flow.

Thanks for confirming! I'll order the 2nd pump.

it'll be half the flow rate if EVERYTHING is the same..all the way around. The flow rate through each leg will depend on pressure drop. So, for example, if one leg has longer tubing, then the flow rate will change. The main thing you will have to worry about is if something happens to one leg which causes the pressure drop to increase, thereby sending more fluid thru one radiator - which could possibly overload it..rare, but something to think about.

The resistance of a parallel system can be described simply as "The total resistance of a parallel system will always be lower than the smallest resistor". the formula to describe this is 1 / ( (1/r1) + (1/r2) + (1/r3) ) continuing until all resistances are calculated in. Given 2 identical resistance loads the total restriction to flow will be halved or doubled (parallel / series). simple as that, if your pump is rated 1gpm but systems restriction only allows 0.5gpm moving from series to parallel would improve flow rate to ~ 0.75-0.8 GPM halved(two paths) yeilding ~0.35gpm through each radiator. While this is less flow though each rad the total flowrate has improved which when all things are considered is better.