The Science Behind Coolants

[AllAgainstPaul]

Warning: This Post Contains Mathematical Formulas.

1. Preface:

I have look around and there are several threads and pages on the Internet concerning which coolants are better for liquid cooling and why. I decide to dig up my old textbooks and figure out all the different aspects of liquids and how each property affects is merit as a coolant. Some of these properties play a more pivotal role but to be thorough I might as well list them all. Also I would like to note that I use SI units rather than metric or empirical.

2. Basic Terms:

Watt

Symbol: W
SI Measurement: J / s
Definition: Unit of work defined as the dissipation of one joule in one second.

Joule

Symbol: J
Definition: The basic unit of energy.

3. Density:

Symbol: p
SI Measurement: kg / m³
Reasoning: Density is defined as mass per unit of volume. This is relevant to WC as the more dense a given liquid is, the more energy a single ml can take in to raise it a degree. As a coolant, the greater the density the better.

4. Pressure:

Symbol: p
SI Measurement: N / m²
Reasoning: As far as WC goes, pressure does not affect coolant that much unless it is a more exotic liquid. Some liquids display vast differences is thermodynamic properties when under differing pressures. Usually the difference in pressures has to be very large.

5. Specific Heat Capacity:

Symbol: c
SI Measurement: J / (kg * K)
Reasoning: Specific Heat Capacity is defined as heat capacity per unit of mass. Basically it means that, How much energy can a kilo of liquid take in before its temperature raises one degree. As coolants go, the larger the Specific Heat Capacity, the better.

6. Temperature:

Symbol: T
SI Measurement: K
Reasoning: Temperature has a large affect on coolants. Similar to pressure some exotic liquids display differing properties as temps change. But the big concern for WCers is some coolants gum up as temperatures drop to 273 Kelvin.

7. Thermal Conductivity:

Symbol: λ
SI Measurement: J / (s * m * K)
Reasoning: Thermal Conductivity is defined as energy transferred over a given amount of time, distance, and temperature difference. The higher the thermal conductivity the faster a liquid can absorb energy.

8. Viscosity:

Symbol: η
SI Measurement: N * s / m²
Reasoning: Viscosity is defined as a property of a liquid by virtue of which they offer resistance to flow. It is basically the coefficient of friction for liquids. The larger the value of viscosity a liquid has, the harder it is for that liquid to flow.

Warning: if a liquid exists that works better on all of these fronts under Standard Pressure and Temperature there is probably a catch, whether it be a major health hazard, incredibly flammable, damaging to your components, rarity and cost of procurement, or just a chaotic and unstable liquid to work with. I presume, though, that if you are going to take the time to find out all the scientific information about a liquid you would also have to common sense to see if any of the previously stated problems exist.

If I have accidentally omitted anything of importance when it comes to coolant please post it.

[Ic3man]

Colour

You don't really want to be using blue pentosin G11) if you want a red loop - vice versa etc etc. Hardly scientific but an important factor to consider if you are using dyes.