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Originally Posted by bobo5195
I would need to punch up some numbers but two rads in parallel should have a large increase in heat dissipative capacity as they have a higher dt but no loss in performance due to lower flow.
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Comparison is two rads in water flow parallel vs same two rads in water flow series. Air flow is assumed parallel. Complexity of plumbing (T's, extra tubing) probably offsets any gains from reduction in head by each radiator. As we both agree, any impact from minor flow rate changes is going to be miniscule.
Hence, you plumb for whatever is easiest to plumb, which is typically serial.
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Originally Posted by bobo5195
i assume to use a 3 way splitter in which Q is conserved and then use dp = f(v) where you look up f(v) and use and iterative loop to solve).
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Java is OO, so keep that in mind. First I use an iterative approach to solve the flow rate. Each obj is asked to calc its head based on a set flow rate. Pumps are positive, restrictions are negative. I keep nudging the flow rate until I get near enough to zero. I worked on mathematical solution for only several minutes before I decided we have fast computers and loops in languages for a reason.
In my latest version (still in debug) I then do a second iteration to find the C/W and delta-T values, with again some objects producing positive delta-T's (pumps and blocks heat the coolant) and some objects cool the coolant (radiators) so negative detlta-T's until the coolant temp at the end is "close enough" to the coolant temp at the beginning.
I have a forumlae engine that accepts limitless additions of blocks of "x.y^z". That said, as per the graphs, most things just need two or three blocks.
Each object just needs then a PQ formulae.
Blocks need a Wattage for the thing they are cooling, and a C/W formulae to approximate the CPU temp to coolant temp delta-T.
Radiators also need a C/W formulae for their cooling efficiency. I'd love to have a three-dimensional map as the figures I have are from BillA's testing and he maintained a constant water/air delta-T, which is not what I want. Oh well.
Pumps have a wattage, and a formulae for approximating the % of that wattage added as heat based on flow rate.
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Originally Posted by bobo5195
Pumps in “manifolds” is an intrinsic problem with your approach. [SNIP]For some loops you may not be able calculate an answer.
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Yep - I just don't handle it properly so flag it as "use with caution".
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Originally Posted by bobo5195
Correction of source data for fittings is easy as pie. [SNIP]Derivation of losses for pipe diameter changes is easy.
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Yep - I have a little app that I can predict it with. The issue is time in getting to it, and also programming the GUI to enable barb selection. I got sidetracked into trying to enforce sense (ie, can't select 1/2" tubing for a 3/8" barb) but it got hard so I did something else. This is a hobby, so when it stops being fun....
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Originally Posted by bobo5195
Extrapolation good. The problem is extrapolate to what.
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Well beyond the approximator. Supply the PQ and CW graphs for a block or rad, and that's what it can do. I've done some work on modelling jet blocks and other designs, but way beyond my capabilities!
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Originally Posted by bobo5195
If you would like pressure drop calcs for a pipe I could send you a subroutine with ease.
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I can deduce a formulae using an app off the web, but the issue is it doesn't map to testing I found elsewhere. Perhaps silicon tubing is "sticky" to water flow vs the material properties of the apps?
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Originally Posted by bobo5195
The heat inputs stuff should be easy with look ups (if your not a crap programmer like me). The pump stuff I was just going to model as a singular heat input of X watts. Which I think is okay heat is mostly transferred from the pump to the water instead of the air. Could use an insulated pump to test this.
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In my latest version, I just have a selection widget where you select how many watts you want going from the thing-being-cooled into the water. It defaults to 70W.
For pumps, I use a formulae based on the stuff I found at Swiftech, where more power gets consumed when the flow rates go up, and then factor in that, like you, "most" heat goes into the water. Typically I vary from 60% to 80% of the pump wattage. Its just an approximator.
Anyway, so far it concurs with real world stuff. Eg: It too predicts the Iwaki 30 is worse to use than a 20 as the heat from the pump undoes any benefits from the flow rate.