Number of Radiator Passes

[tok3n]

Can anyone clear this up or give some feed back? Is it better to use a radiator (computer WC specific / not car style heatcores) with more passes, or less? And why? It seems that more passes would allow the water to be cooled more, but with a single pass, water is forced thru all the tubes on one shot so it would seem the same in cooling. I'm confused.

[Player0]

All WC specific radiators are car radiators of some sort. Heater cores or transmission coolers, or even radiator radiators.

More passes is better. That means water is in the radiator longer and it looses more heat along the way. The shorter the run through the radiator, the less efficiently you will cool the water (this is also why too high of a flow rate and reduce radiator efficiency).

[sn_85]

yeah more passes are better. but if you think a/b it if you have too many passes that requires a pump that flows a lot more then your average eheim, hydor, or via aqua. heatercores out of cars use a single pass design, meaning they go in and come out after just one loop. a radiator such as a lytron might take like 16 or 32 loops or even more or less depending on its model. the less passes the less flow restriction there is. obviously if your gonna use a average pump then it wont do you good. but if you used something like an Iwaki pump then you can deal w/ more passes.

[tok3n]

Thats what I originally thought. More passes the better. But someone explained it to me like this (not sure what to think now):

Most efficient cooling works with greatest temperature difference. Multiples passes, when the water comes back, it will already be acooled a bit so it won't extract the heat as well on the other passes. With a single pass thru all the tubes of the radiator, the temp difference is maximal.

[Drake]

I think he's saying the water loses the most heat and least flow resistance on the first pass.

[Player0]

Originally posted by tok3n
Most efficient cooling works with greatest temperature difference. Multiples passes, when the water comes back, it will already be acooled a bit so it won't extract the heat as well on the other passes. With a single pass thru all the tubes of the radiator, the temp difference is maximal.

Yes, radiators work best with the greatest difference in temperature. So you start dealing with the law of diminishing returns. So say the first pass releases heat with 75% efficiency, and the second pass works at 50%, and then the next pass at 30% efficiency. Yes, the third pass isnt working very much. However, it is contributing at least some more cooling potential. So more passes will always create better cooling, even if they arent working as well as the previous passes.

[volse]

I think the diminishing return law is definitely applied here. The problem is finding the ever elusive "sweet spot"; true..with more passes you will take away more heat...but like the others say...the more passess, the lower the flow rate...then of course if you get a bigger pump you also have to worry about dumping more heat into the loop...sooooo....time to run some tests. Personally, I would go with a larger rad (bix 2..or thermochill) and stay with the single pass....an increase in surface areaa is always a huge plus. Again, you won't get below ambient no matter what combo you use, unless of course you chill or use pelts...I'll do some research and see what I can come up with in the meantime.....Peace:alienbird

[tok3n]

What confuses me then is it seems most 1/2" 120mm sized radiators are dual pass whereas 3/8" are quad pass. Then 3/8" would cool better then right?

[Player0]

No. Water will move faster through 3/8" tubing than 1/2" tubing.

[tok3n]

Originally posted by Player0
No. Water will move faster through 3/8" tubing than 1/2" tubing.

So you mean because its moving faster thru 3/8" tubing, it's not getting cooling as much?

[Drake]

Yes, it's spending less time and there's less water in the radiator.

[tok3n]

So that makes up for the fact that 1/2" radiators are dual pass but 3/8" are quad pass?