# Colder water better thermal conductor?

• Pengwuino
In summary, the question being discussed is whether colder water is a better thermal conductor than warmer water. The answer is that while colder water may have a higher potential for cooling, the approach temperature between the water and the heat source also plays a significant role. Increasing the flow rate can help bring the two temperatures closer together and improve heat transfer. However, in water-cooling computer systems, there are opposing constraints between the heat source and heat sink, and matching equipment for maximum performance is important.
Pengwuino
Gold Member
Is colder water a better thermal conductor then warmer water?

Say for example you nee dsomething to be cooled at 70C and you run water to it in a system. Which would cool this "something" quicker, 10C water or 20C water?

10C water will. But its not a question of thermal conductivity, but rather approach temperature. Since heat transfer rate is proportional to temperature difference, the greater temperature difference (approach temperature), the greater the heat transfer. So 70-20=50 and 70-10=60. 60 is 20% bigger than 50, so 10C water has the potential to cool something 20% better than 20C water. I say "potential" because flow rate makes a big difference.

Ok check this out. I am on a forum with a lot of people who like to water-cool theri computer systems. Its not... literal water cooling lol, but a series of tubing going to the main components into water blocks and make use of a radiator and pump. This one guy proposed that:

Well, if you have time, check it out http://www.overclock.net/showthread.php?t=20358

Guess who i am on that forum :D

Ehh, this is a really tough issue because the he source and heat sink have similar, but opposing constraints: for the heat source (the cpu) you want the coldest water possible and the highest flowrate possible, but for the heat sink (the radiator), you want the warmest water possible (but again, highest flowrate). Increasing the flowrate will bring the two temperatures closer together.

Your idea that if you double the flowrate, you simply cut the delta-T in half and the overall heat transfer stays the same is close but not quite right. Because of the approach temperature issue I mentioned above, it isn't a linear relationship: you will get more heat transfer by increasing the flow rate. Its easiest to see this by looking at it the other way: what if you decrease the flow rate to the point where the water ends up at 70C? It can't get any warmer, so that's a limit to your delta-T.

In HVAC, you match your equipment to each other to maximize performace and efficiency, looking at performance curves and such. The way most overclockers seem to do watercooling, though, they have an absurdly large radiator - and that's a good thing. The best cooling comes from the lowest possible temperature and the highest possible flowrate entering the CPU block.

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Lol some of these guys have radiators out of Buicks and Pontiacs :P

## What is thermal conductivity?

Thermal conductivity is a measure of a material's ability to conduct heat. It is defined as the amount of heat that is transferred through a unit area of a material in a unit time, when there is a temperature difference of one degree between the two sides.

## Why is colder water a better thermal conductor?

Colder water is a better thermal conductor because the molecules in colder water are closer together, allowing for more efficient transfer of heat. Additionally, cold water has a higher density, which also aids in heat conduction.

## How does thermal conductivity affect heat transfer?

The higher the thermal conductivity of a material, the faster heat can be transferred through it. This means that materials with higher thermal conductivity will feel colder or hotter to the touch, depending on the temperature difference between the object and the surrounding environment.

## What factors affect the thermal conductivity of water?

The thermal conductivity of water can be affected by factors such as temperature, pressure, salinity, and the presence of impurities. For example, saltwater has a higher thermal conductivity than freshwater due to the presence of dissolved ions.

## How is the thermal conductivity of water measured?

The thermal conductivity of water is typically measured using a thermal conductivity meter, which measures the rate of heat flow through a sample of water. Alternatively, it can also be calculated using the thermal conductivity equation, which takes into account the specific heat capacity and density of water.

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