Water Jacket Flow Rates

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One concern I have with watercooling is flow rates – how much water flowing through the water jacket will impact CPU Cooling. When I first saw the Senfu unit, the very small (2mm) inlet/outlet diameter was the smallest I have seen on any unit around. I recently tested CoolChip’s unit which has a 1/4″ inlet/outlet diameter and thought a comparison between the two would be interesting.

As the picture below shows, there is a marked size difference between the two units overall; the inset picture shows the difference between both unit’s intake diameters. I decided to test the difference using a peltier setup. I used the Senfu radiator (very nice unit) and a Beckett 150 gph pump. I was concerned about the pressure the hoses would experience with the Senfu as the constriction should increase pressure – it’s like having a straw for a fire hose nozzle.


I made sure all hose connections were tight with the Senfu and turned it on – I immediately got water all over the place. I had to use different hose diameters to fit the Senfu’s small hoses to the larger hoses (1/2″) of the Beckett and Senfu radiator (which I modified so it takes a 3/8″ hose); the resulting pressure found any leak possible.

I tightened clamps tighter and stemmed the flow. I ran the whole setup with two power supplies – one for the peltier and one for the fans on the radiator. The pump is 120 AC. I then changed out the Senfu water jacket for the CoolChip unit which uses 1/4″ hosing. There was less pressure and I had no problems adapting hoses to fit. I then took the outlet hose and pumped water out into a measured vessel to calculate flow rates through each setup.


CoolChip: Peltier -28.0 C with 30 gph flow rate.
Senfu: Peltier -24.8 C with 11.3 gph flow rate.

Surprisingly I found some difference but not the magnitude I expected. It could be that the radiator is so large compared to the water flow that it compensates a lot for the Senfu’s decreased flow rate. In any event, I will do further testing to see how these parameters affect performance.

PS: Just for fun, I tossed a bunch of ice cubes into the water and ran the peltier to see how cold it would get – with the CoolChip unit, it got down to -41.3 C.


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