Test Report: XSPC RX120

[Webby]

To get the thread back to the testing that Skinnee has carried out Rather than the woes of XSPC's QC and where to buy a TC rad from

Skinnee, first great test much appreciated (I can't remember if I posted a thanks before or not so here it is possibly again ) a couple of questions and potential observations.

1. The Percentage air used calculation how was this value calculated? From the numbers you present I cant work it out to get the same as you, I was taking the difference in air in to water out to be maximum capacity and air out - air in to be the fraction of the air capacity used so for the first set of data 1008rpm,

Air In = 24.01°C, Air Out = 36.10°C and Water Out = 43.37°C

Water Out - Air In = 19.36°C
Air Out - Air In = 12.09°C

So (12.09 / 19.36) x 100 = 62.45%

You report 63.64% so since I guess your table is generated by a spreadsheet you must be doing a different sum care to share? My only guess is you use Water In temp for the max instead of Water Out (which incidentally would be what I would do if it was me and I had the data) but that should lower the percentage not increase it...

2. On the subject of Water In temps it would be useful to know what this value was as a check against energy dissipated by the radiator, for example in Martin's test of the MCR220 (http://martin.skinneelabs.com/Swifte...20-Review.html) when using 1000rpm fans the drop in water temperature over the rad is 0.43°C, flowrate was 1.5gpm, and the water temperature was ~40°C (need this for a density calculation).

To calculate the watts dissipated the following equation must be solved,

KiloWatts Dissipated (kJ/s) = Mass Flowrate (kg/s) * Specific Heat (kJ/kg.K) * Temp. Change (K)

So for Martin's scenario,

Mass Flowrate = 1.5 gpm = 5.68 L/m = 0.095 L/s = 0.094 kg/s (Density @ 40°C = 992 kg/m³)
Specific Heat = 4.1813 kJ/kg.K
Temp. Change = 0.43 K

Kilowatts = 0.094*4.1813*0.43 = 0.169 kW = 169W

Martin states that the applied heat load is 302W for that much energy to have been dissipated a temp difference of 0.77 K would be required.

When the fan speed is increased to 3000rpm the temp difference rises to 0.61°C this equates to a heat dissipated of 240W much closer to the applied value of 300W.

I assume that this is an artefact of heat loss from the reservoir, tubing and other equipment in the loop which is amplified as the water temperature in the loop increases, of course what it does mean is that the C/W values are off as the rad is actually not dissipating as much energy as was assumed.

Without Water In temps for your tests I can not compare the different fan speeds to see if your testing follows the same trend, I also have not yet completed my thinking on the ramifications for what it means in terms of calculating C/W we will know how much heat was actually dissipated by the radiator but this is effected by the heat loss in the rest of the loop.

Perhaps insulating all tubing, reservoirs etc would make for a more controlled system in terms of radiator performance.

Anyway good testing hope to see some Water Temp In data so that we can see if the radiator was really dissipating 300W at each fan speed. Or of course a reason why my thinking is flawed.

[skinnee]

To get the thread back to the testing that Skinnee has carried out Rather than the woes of XSPC's QC and where to buy a TC rad from

Skinnee, first great test much appreciated (I can't remember if I posted a thanks before or not so here it is possibly again ) a couple of questions and potential observations.

1. The Percentage air used calculation how was this value calculated? From the numbers you present I cant work it out to get the same as you, I was taking the difference in air in to water out to be maximum capacity and air out - air in to be the fraction of the air capacity used so for the first set of data 1008rpm,

Air In = 24.01°C, Air Out = 36.10°C and Water Out = 43.37°C

Water Out - Air In = 19.36°C
Air Out - Air In = 12.09°C

So (12.09 / 19.36) x 100 = 62.45%

You report 63.64% so since I guess your table is generated by a spreadsheet you must be doing a different sum care to share? My only guess is you use Water In temp for the max instead of Water Out (which incidentally would be what I would do if it was me and I had the data) but that should lower the percentage not increase it...

You have the calculation right, and when I go into Excel and work the numbers, you're right. I completely goofed on the calculation, I chose the the cell for Air Out Sensor 1 rather than the average for both Air Out Sensors.

Thank you for pointing this out, I will update the calc's and charts as well as my radiator template so I don't make this mistake again.

On this, Excel's rounding makes me , 62.449 is the raw number calc to three decimals, but since Excel uses the raw numbers from the cells I point it at in the forumla, the result is 62.4697%

2. On the subject of Water In temps it would be useful to know what this value was as a check against energy dissipated by the radiator, for example in Martin's test of the MCR220 (http://martin.skinneelabs.com/Swifte...20-Review.html) when using 1000rpm fans the drop in water temperature over the rad is 0.43°C, flowrate was 1.5gpm, and the water temperature was ~40°C (need this for a density calculation).

To calculate the watts dissipated the following equation must be solved,

KiloWatts Dissipated (kJ/s) = Mass Flowrate (kg/s) * Specific Heat (kJ/kg.K) * Temp. Change (K)

So for Martin's scenario,

Mass Flowrate = 1.5 gpm = 5.68 L/m = 0.095 L/s = 0.094 kg/s (Density @ 40°C = 992 kg/m³)
Specific Heat = 4.1813 kJ/kg.K
Temp. Change = 0.43 K

Kilowatts = 0.094*4.1813*0.43 = 0.169 kW = 169W

Martin states that the applied heat load is 302W for that much energy to have been dissipated a temp difference of 0.77 K would be required.

When the fan speed is increased to 3000rpm the temp difference rises to 0.61°C this equates to a heat dissipated of 240W much closer to the applied value of 300W.

I assume that this is an artefact of heat loss from the reservoir, tubing and other equipment in the loop which is amplified as the water temperature in the loop increases, of course what it does mean is that the C/W values are off as the rad is actually not dissipating as much energy as was assumed.

Without Water In temps for your tests I can not compare the different fan speeds to see if your testing follows the same trend, I also have not yet completed my thinking on the ramifications for what it means in terms of calculating C/W we will know how much heat was actually dissipated by the radiator but this is effected by the heat loss in the rest of the loop.

Perhaps insulating all tubing, reservoirs etc would make for a more controlled system in terms of radiator performance.

I will add the Water In temps to the standard chart I use when posting the test results. I do want to point out that I only use one sensor for Water In, so we do not get the luxury of sensor averaging for water in, which I feel is needed when using the digital sensors just due to their accuracy. Basically, I need to order more sensors to accurately report Water In.

With that said, here are the Water In temps I captured on Water In Sensor 1and averaged acrossed the entire test period (the same as all other sensors)

1000RPM - 43.99
1400RPM - 39.20
1800RPM - 38.10
2300RPM - 35.39
2800RPM - 33.86

Anyway good testing hope to see some Water Temp In data so that we can see if the radiator was really dissipating 300W at each fan speed. Or of course a reason why my thinking is flawed.

Thanks...even though I made some mistakes in my calc's and data presentation. But thank you for doing the work to point them out, but I am a bit embarassed that I made that mistake. However, I appreciate you pointing it out so I can fix it and make sure it does not happen again.

I will be updating the charts tonight/tomorrow, the charts will automatically update on the first page since the images are hosted by me and not attachments. I will add a post when I have the charts updated though.

Again, thanks Webby! I appreciate the additional work you did to check over the data. You're helping me immensly to better the presentation and accuracy of information!