Flow rate measurement

Coolant flow rate is one of key attributes that determines the performance of the cooling system. The more coolant flowing through the loop, the better the cooling performance of the water blocks and the radiator, and also the smaller the rise and fall of temperature within the loop.

More flow cannot be detrimental to performance. Thoughts of "more time spent in the radiator" are incorrect. Imagine the loop as a racing car track, and the radiator as the main straight, where the main straight is 1/3rd the track distance. A car doing 1 lap per minute is thus spending 20 seconds of each minute in the main straight. A car doing 2 laps per minute is doing a lap every thirty seconds, and hence spending 10 seconds of every thirty seconds in the main straight, and hence is spending the same 20 seconds per minute in the main straight.

The only time when more flow is worse is when the pump you need to run to increase the flow rate dumps enough additional heat into the coolant due to its power that it negates the additional flow benefits.

As a guide, one litre per minute (LPM) is low enough for a pump upgrade to deliver measurable results, whilst the gains above seven LPM are often undetectable.

Measuring Flow Rate To measure your flow rate, you will need:

• One container able to fit your submersible pump, or, a small container to act as a reservoir for your non-submersible pump
• One large container
• A stopwatch
• Your watercooling loop all connected together.
• An area which can get very wet. Suggest back yard!

Your rig will be disassembled, so don't bother to fill it with glycol etc before hand!

1. Disconnect the inlet tube at the outlet barb of the component before the pump. 1.a If you pump is submersible, place the pump in the small container so that the open end of the inlet tube will be submerged when the bucket is full. 1.b If your pump is not submersible, then only the open end of the inlet tube goes into the small container, such that the open end will be submerged when the bucket is full. 2. Layout the rest of the loop to be lying neatly (and any lapped bases protected).

This means any Net-Pressure-Suction-Head on the pump inlet will be included in the testing

2. Using a measuring cup or jug (or other accurate means), calculate the volume in litres of the large container when it is full. I used a measuring jug to measure the exact volume of an ice cream container, and then used the ice cream container to fill my 40L storage container. When done, empty the container, and place the container close to the loop and first container.

3. Place the garden hose into the first container and fill the bucket. Leave the hose running. Ensure the last component's outlet barb is not going to empty into the large container, or anywhere critical (like power points, pets etc). Once the first bucket is full, turn on the pump. Adjust the garden hose flow rate so that the bucket is always full (without wasting too much water).

4. Ensure the large bucket is empty of water, and your stopwatch is zero'd. Then, at the same time, direct the flow out of the last component in your loop to fill the bucket, and start timing.

5. The complex maths is: Large container volume in litres divided by time take in minutes( so 3 mins 30 seconds = 3.5).