Overclock.net › Forums › Cooling › Water Cooling › delta t and real temp
New Posts  All Forums:Forum Nav:

delta t and real temp

post #1 of 3
Thread Starter 
So Ive read bunch of radiator reviews and it seems to be common to measure the water temperature.

In real life if Radiator A has delta t 15c and Radiator B has 17c.

Lets say a 7970 is 55c on load with A, would this same 7970 be 57c on load with B?


Or did I miss something, also I would think I need to fin reviews where the temperature was run long enough to stabilize temps.
Maybe runnin 5min show delta t difference only 2c, but running 5h shows difference delta t 15c etc........
Gaming Rig
(15 items)
 
  
CPUMotherboardGraphicsRAM
I7 5820k Stock clocks Gigabyte X99 UD4 2x EVGA GTX 1080 FE SLI  Corsair 64GB (4x16GB) DDR4 2133MHz CL13 Vengean... 
Hard DriveCoolingOSMonitor
Intel 530 M.2 SSD 180GB OS + Samsung 850 EVO st... Mugen 4 push pull Win 7 64bit home prem Acer 27" XG270HU 144hz TN + LG Oled 4k TV 
PowerCaseMouseMouse Pad
EVGA T2 1600W Fractal XL R2 CM Xornet Steelseries Qck+ 45cm black 
Audio
Sennheiser RS185 wireless headphones 
  hide details  
Reply
Gaming Rig
(15 items)
 
  
CPUMotherboardGraphicsRAM
I7 5820k Stock clocks Gigabyte X99 UD4 2x EVGA GTX 1080 FE SLI  Corsair 64GB (4x16GB) DDR4 2133MHz CL13 Vengean... 
Hard DriveCoolingOSMonitor
Intel 530 M.2 SSD 180GB OS + Samsung 850 EVO st... Mugen 4 push pull Win 7 64bit home prem Acer 27" XG270HU 144hz TN + LG Oled 4k TV 
PowerCaseMouseMouse Pad
EVGA T2 1600W Fractal XL R2 CM Xornet Steelseries Qck+ 45cm black 
Audio
Sennheiser RS185 wireless headphones 
  hide details  
Reply
post #2 of 3
a lot of thing come into how long it take to stabilise, manly the size or the reservoir.

now with the different rad's there will be a difference but it won't be a clear cut 2c difference as heat transfer rate is not liner but logarithmic. this is my understanding from a physic view point. the one with the lower delta T is better, but i can't tell you by how much and is it worth the extra $$$. also what fans did the rad's have on them?, what pump? so there is a few different things that come into play when finding the best.

this is my understanding but could be wrong.
Edited by Bradey - 2/6/12 at 3:46am
    
CPUMotherboardGraphicsRAM
intel i5 2500k  GA-Z68M-D2M r9 290 OCZ 4x2GB 
Hard DriveHard DriveCoolingOS
raptor Western Digital watercooled 7 
MonitorKeyboardPowerCase
3 dell 1920x1080 + 1440x900 dell stock corsair GS600 SG08 
Mouse
dell stock 
  hide details  
Reply
    
CPUMotherboardGraphicsRAM
intel i5 2500k  GA-Z68M-D2M r9 290 OCZ 4x2GB 
Hard DriveHard DriveCoolingOS
raptor Western Digital watercooled 7 
MonitorKeyboardPowerCase
3 dell 1920x1080 + 1440x900 dell stock corsair GS600 SG08 
Mouse
dell stock 
  hide details  
Reply
post #3 of 3
As a tester myself, temperatures stabilize in 5-7 minutes. Any increase in delta T after that is from failure to properly measure/control intake ambients (exhausted heated air heating up the local ambients and not measuring them accurately) or using a variable heat load.

When you first start a test, say a cpu + pump putting out 200W of heat, the radiator is not efficient enough to cool water given the small difference between ambient air and near ambient temp water (near ambient water temp when cpu was at idle or off). So at 1.5 gpm pump speed, it takes 396W to heat water by 1C so after going through cpu, the water will be heated by 0.5C per pass and radiator can only cool it by less than 0.5C because radiators are not efficient with small difference in air and water temp. Then after 5-7 minutes and many passes, the water has been heated by say 6C and now have steady state as the radiator is now efficient enough to cool the water 0.5C per pass as the pump + cpu heat the water by 0.5C per pass. Temps will not rise after that 5-7 minutes unless the heat load is increased, or unless you heat the ambient intake air and dont measure it accurately (experimental error), or heat ambient air like 5+ C to the point that you cause the cpu to leak slightly more, adding slightly more heat to loop, which will cause the cpu to go up by 0.3C or so, but delta air to water of the rad will likely be unchanged, since rad is efficient at that point to take care of extra heat.

And yes, there is a delta from core of cpu to water and that should be unchanged whether on rad A or B in your example. So if water is 2 C hotter, the core temp will be 2C higher.
My System
(15 items)
 
  
CPUMotherboardGraphicsRAM
6900K 4.4ghz  MSI X99A Krait Titan XP Gskill 32GB 3200 C14 
Hard DriveHard DriveCoolingOS
Samsung 960 Pro 1TB OS Samsung 850 pro 1TB games D5, XT45 280 rad, Nemesis 280 rad,  Windows 10 64bit 
MonitorPowerCase
Acer Predator XB271HU 144hz Seasonic Prime Titanium 850 Fractal Design R5 
  hide details  
Reply
My System
(15 items)
 
  
CPUMotherboardGraphicsRAM
6900K 4.4ghz  MSI X99A Krait Titan XP Gskill 32GB 3200 C14 
Hard DriveHard DriveCoolingOS
Samsung 960 Pro 1TB OS Samsung 850 pro 1TB games D5, XT45 280 rad, Nemesis 280 rad,  Windows 10 64bit 
MonitorPowerCase
Acer Predator XB271HU 144hz Seasonic Prime Titanium 850 Fractal Design R5 
  hide details  
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Water Cooling
Overclock.net › Forums › Cooling › Water Cooling › delta t and real temp