Alphacool drops some new radiators and some new coolant, or is it?

lobstar

Limp Gawd
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Nov 24, 2004
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241
Heat in = heat out when in equilibrium. If you're dissipating more heat, your loop temperatures are dropping.
"Heat out" increases with volume of water able to move through a cooling structure where "Heat in" doesn't change. My hardware isn't suddenly generating 200w more heat because I added a pump.
 

BrotherMichigan

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Apr 8, 2016
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Heat in = heat out when in equilibrium. If you're dissipating more heat, your loop temperatures are dropping.
Yes, but you can dissipate MORE heat at the same temperature (so still in equilibrium) at higher flow rates. This isn't controversial.
 

Tsumi

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"Heat out" increases with volume of water able to move through a cooling structure where "Heat in" doesn't change. My hardware isn't suddenly generating 200w more heat because I added a pump.

You are confusing heat with temperature.

Yes, but you can dissipate MORE heat at the same temperature (so still in equilibrium) at higher flow rates. This isn't controversial.

You cannot dissipate more heat than you are putting in. Your average water to air delta T for the same heat input is going to be the same regardless of whether you're running 1 GPM or 10 GPM.
 

lobstar

Limp Gawd
Joined
Nov 24, 2004
Messages
241
You are confusing heat with temperature.
Nope. My equipment doesn't generate temperature does it?
You cannot dissipate more heat than you are putting in.
Right, but if my equipment is not operating at it's peak efficiency due to not meeting the flow it's designed for that means I'm more efficiently dissipating the existing heat. Since I can't increase the static pressure or add more fans to my existing radiators I can still increase the flow.

https://www.xtremerigs.net/2015/03/25/alphacool-nexxxos-monsta-360-radiator-review/all/1/
 
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BrotherMichigan

Limp Gawd
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You cannot dissipate more heat than you are putting in.
Correct (at constant temperature, anyhow.)
Your average water to air delta T for the same heat input is going to be the same regardless of whether you're running 1 GPM or 10 GPM.
Incorrect. At greater flow rates, you can dissipate more heat at the same delta as you can with a lower flow rate. Say you dissipate 250 W at 1.0 GPM for a 10 C delta, you might be able to dissipate 300 W at 1.5 GPM while maintaining that 10 C delta.

If you don't want to believe the actual physicist, here is some empirical data from XtremeRigs. The below chart lists power dissipated for a 10C delta at various combinations of flow rate, fan speed, and fan configuration:
w10dt.png
(source)

Notice how the number goes up with the flow rate?
 
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Tsumi

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Correct (at constant temperature, anyhow.)

Incorrect. At greater flow rates, you can dissipate more heat at the same delta as you can with a lower flow rate. Say you dissipate 250 W at 1.0 GPM for a 10 C delta, you might be able to dissipate 300 W at 1.5 GPM while maintaining that 10 C delta.

If you don't want to believe the actual physicist, here is some empirical data from XtremeRigs. The below chart lists power dissipated for a 10C delta at various combinations of flow rate, fan speed, and fan configuration:
View attachment 348336
(source)

Notice how the number goes up with the flow rate?

Notice how the numbers change very little at the lower fan speeds for most radiators? Especially at flow rates above 1 GPM? In some cases, it even went down going from 0.5 to 1 GPM, which begs the question of measurement accuracy as well and confounding factors. Furthermore, your very source itself states that most radiators care little about flow rates, and they admit that very small changes in measurement can lead to big swings in heat dissipation numbers.

The large increases in heat transfer at higher fan speeds are easily explained by looking at the data as well. At the lower flow rates, the water is cooling down to near ambient in the middle of the radiator, underutilizing the rest of the radiator, which I did state as a caveat to flow rates not mattering.

As your flow rates go up, the difference between inlet and outlet temperature goes down, and it quickly becomes a rate of diminishing returns. On the XE360, at 0.5 GPM you have a maximum of 2 C difference. At 1 GPM, 1 C. At 1.5 GPM, 0.6 C. I stand by my statement that testing at different flow rates offer very little meaningful data, at least as far as radiator cooling performance is concerned.
 

BrotherMichigan

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Notice how the numbers change very little at the lower fan speeds for most radiators? Especially at flow rates above 1 GPM? In some cases, it even went down going from 0.5 to 1 GPM, which begs the question of measurement accuracy as well and confounding factors. Furthermore, your very source itself states that most radiators care little about flow rates, and they admit that very small changes in measurement can lead to big swings in heat dissipation numbers.

The large increases in heat transfer at higher fan speeds are easily explained by looking at the data as well. At the lower flow rates, the water is cooling down to near ambient in the middle of the radiator, underutilizing the rest of the radiator, which I did state as a caveat to flow rates not mattering.

As your flow rates go up, the difference between inlet and outlet temperature goes down, and it quickly becomes a rate of diminishing returns. On the XE360, at 0.5 GPM you have a maximum of 2 C difference. At 1 GPM, 1 C. At 1.5 GPM, 0.6 C. I stand by my statement that testing at different flow rates offer very little meaningful data, at least as far as radiator cooling performance is concerned.
Numbers change very little at the low end because you're restricted in how much heat you can remove from the loop for a given delta by the low airflow. As for your claim about decreasing difference between inlet and outlet temperatures, you're still talking about a constant heat load, which is not what the data above is presenting. Notice how you can get improvements over 20% for some radiators going from 0.5 GPM to 1.5 GPM? That's saying the loop is capable of handling more than 20% more heat while maintaining the same coolant temperature, meaning the cooling performance of the loop has increased. This is in direct contradiction to you claim about the water cooling down in the middle of the radiator.

You can stand by your statement all you want, you're still wrong.
 

Tsumi

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Numbers change very little at the low end because you're restricted in how much heat you can remove from the loop for a given delta by the low airflow. As for your claim about decreasing difference between inlet and outlet temperatures, you're still talking about a constant heat load, which is not what the data above is presenting. Notice how you can get improvements over 20% for some radiators going from 0.5 GPM to 1.5 GPM? That's saying the loop is capable of handling more than 20% more heat while maintaining the same coolant temperature, meaning the cooling performance of the loop has increased. This is in direct contradiction to you claim about the water cooling down in the middle of the radiator.

You can stand by your statement all you want, you're still wrong.

You're still not reading and you're still misinterpreting the data. First of all, they are not heating the water to a constant temperature. They're heating it with a constant heat load, and then extrapolating that to heat dissipated at a constant temperature. You can see in the table below that at 0.5 GPM, the air exhaust temperature essentially matches the water outlet temperature. Their testing methodology clearly has the water dropping to ambient by the time it is in the middle of the radiator at 0.5 GPM. This also has the chance of happening at 1850 RPM, where heat is being removed very fast from the water.

XE-Thermal-Data-Table.png

Other quotes from the article that you may have conveniently skipped over:

Retrospect​

In retrospect it might have been better to increase and decrease heater power so that approximate deltas always remain the same. Running a 15C delta at all times for example would really help the high air flow cases were errors will be larger due to smaller deltas in the current setup.

Nearly every radiator performed the same way, i.e. at the air flow rates of interest increasing flow above 1GPM does not seem to help or hurt the radiator performance. However dropping to 0.5GPM can show some loss of performance at high airflow.

From the huge flow rate data summary section that's in the spoiler:

The variation is quite small indeed with many radiators moving only a few percent over the 3x flow rate changes (for 750 RPM). As expected this is not a strong effect. Let’s move on to 1300 RPM where the difference should be larger.

At 1300RPM we start to see some definite shifts. While the changes are small (again only a handful of percent between each data point) they are emerging beyond the noise floor and consistently across the flow rate. In total we are seeing about a 5-10% shift across this 3x range of flow rate. Again not a sizeable amount of difference in performance given the large variation in flow, but worth noting nonetheless. Now let’s look at 1850RPM where the effect should be greater still.

While the difference is small but noticeable between the 1.0GPM data and 1.5GPM, the much larger gap occurs at 0.5GPM where the flow rate is now starting to throttle back performance on some radiators. It should be noted that Hardware Labs radiators which have an “opti-flow” front to back flow design do not suffer as much at these low flow rates. This is the reason they have the more expensive flow design. The XE360 for example drops almost 10% from 1.0GPM to 0.5GPM. But the Nemesis GTX for example only drops about 4%. This is the power of the opti-flow design. For most radiators though this means that at higher airflows you will be wanting to keep your flow rate above 0.5GPM to avoid limiting performance.
 
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