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RoboTech · 10-16-2002, 03:58 PM

Water-coolant chemistry… some useful Facts

Surfactants are used in PC water-cooling systems to promote better heat transfer. They do two things: 1) surfactants REDUCE water surface tension, which increases waters surface wetting ability (increased contact between water molecules and heat transfer surfaces) and 2) helps release numerous, tiny air bubbles, which get trapped on heat transfer surfaces (trapped microscopic air bubbles block heat flow). Two of the more popular commercial brands are Water Wetter and Purple Ice (both developed for high performance race car cooling systems).

Adding a surfactant (in the low concentrations used in PC cooling systems) does not change the viscosity of water.

Surfactants (Surface active agents) are also known as wetting agents
Surfactants are organic chemicals that reduce the surface tension of water
(Water has a naturally high surface tension – water likes to cling to itself – beads up)
There are many different kinds of surfactants
Soaps AND detergents are both surfactants
Soap falls into one class of surfactants (anionic surfactants) made from animal fats and vegetable oils
Detergents include several different types of surfactants (anionic and nonionic surfactants) made primarily from petrochemicals

A surfactant molecule is made up of two parts. On one end is a carboxylate group (alkylated carboxylic acid) and on the other end is a long straight hydrocarbon chain. The carboxylate end is attracted to water. This is the (hydrophilic – water loving) end. The hydrocarbon chain end is repelled by water (hydrophobic – water hating) but is attracted to other molecules and surfaces. When a surfactant is added to water, it acts as a “bridge”, which allows the water to fully wet or spread out along surfaces that might otherwise repel the water molecules. (It is this same wetting ability that allows soaps and detergents to attach and suspend oil and grease for cleaning.)

Commercial soap and detergent products can be used in a coolant system (VERY small amount – 1 drop) but I do NOT recommend it as these products generally contain many other additives (emulsifiers, sudsing agents, smelly stuff, etc.) that are not beneficial for PC water-cooling applications.

pH

pH is a measure of how acidic or basic a solution is. The scale ranges from 1 to 14 (1 being extremely acidic, 7 being neutral, and 14 being extremely basic).

In a PC water-cooling system we generally want the pH to be slightly on the basic (alkaline) side to help minimize corrosion. pH values between 8 and 10 are desirable. This also helps retard the growth of biological organisms, as most bacteria, algae, and fungi prefer slightly acidic growing environments to grow in.

Here are some actual pH measurements of several coolant mixes I use:
(Beckman Model 340 pH meter)

3% Water Wetter in distilled water pH = 8.61
(4 oz. ww / quart water)

0.4% Chlorox bleach in distilled water pH = 10.21
(1 Tablespoon / quart water)

3% Water Wetter – 15% Prestone – distilled water pH = 8.75
(4 oz – 19 oz – 105 oz)

3% Water Wetter – 10% Prestone – 30% Methanol - distilled water pH = 8.38
(4 oz – 13 oz – 38 oz – 73 oz)

Note 1: Chlorox bleach (6% sodium hypochlorite in water) is very corrosive to aluminum and SS.

Note 2: Methanol is poisonous and toxic. I only use it in chill water systems operating below freezing.

Note3: It is important to periodically (6 mos – 1 yr) flush out the old and renew the chemical additives in your system. It seems like I am always tinkering with my systems, so they never get the chance to go that long without a refill.

Well there are a few facts… I hope they help answer more questions than they raise…

RoboTech

10-16-2002, 03:58 PM	#59
RoboTech Cooling Savant Join Date: Sep 2002 Location: Cincinnati, OH Posts: 229	Water-coolant chemistry… some useful Facts Surfactants are used in PC water-cooling systems to promote better heat transfer. They do two things: 1) surfactants REDUCE water surface tension, which increases waters surface wetting ability (increased contact between water molecules and heat transfer surfaces) and 2) helps release numerous, tiny air bubbles, which get trapped on heat transfer surfaces (trapped microscopic air bubbles block heat flow). Two of the more popular commercial brands are Water Wetter and Purple Ice (both developed for high performance race car cooling systems). Adding a surfactant (in the low concentrations used in PC cooling systems) does not change the viscosity of water. Surfactants (Surface active agents) are also known as wetting agents Surfactants are organic chemicals that reduce the surface tension of water (Water has a naturally high surface tension – water likes to cling to itself – beads up) There are many different kinds of surfactants Soaps AND detergents are both surfactants Soap falls into one class of surfactants (anionic surfactants) made from animal fats and vegetable oils Detergents include several different types of surfactants (anionic and nonionic surfactants) made primarily from petrochemicals A surfactant molecule is made up of two parts. On one end is a carboxylate group (alkylated carboxylic acid) and on the other end is a long straight hydrocarbon chain. The carboxylate end is attracted to water. This is the (hydrophilic – water loving) end. The hydrocarbon chain end is repelled by water (hydrophobic – water hating) but is attracted to other molecules and surfaces. When a surfactant is added to water, it acts as a “bridge”, which allows the water to fully wet or spread out along surfaces that might otherwise repel the water molecules. (It is this same wetting ability that allows soaps and detergents to attach and suspend oil and grease for cleaning.) Commercial soap and detergent products can be used in a coolant system (VERY small amount – 1 drop) but I do NOT recommend it as these products generally contain many other additives (emulsifiers, sudsing agents, smelly stuff, etc.) that are not beneficial for PC water-cooling applications. pH pH is a measure of how acidic or basic a solution is. The scale ranges from 1 to 14 (1 being extremely acidic, 7 being neutral, and 14 being extremely basic). In a PC water-cooling system we generally want the pH to be slightly on the basic (alkaline) side to help minimize corrosion. pH values between 8 and 10 are desirable. This also helps retard the growth of biological organisms, as most bacteria, algae, and fungi prefer slightly acidic growing environments to grow in. Here are some actual pH measurements of several coolant mixes I use: (Beckman Model 340 pH meter) 3% Water Wetter in distilled water pH = 8.61 (4 oz. ww / quart water) 0.4% Chlorox bleach in distilled water pH = 10.21 (1 Tablespoon / quart water) 3% Water Wetter – 15% Prestone – distilled water pH = 8.75 (4 oz – 19 oz – 105 oz) 3% Water Wetter – 10% Prestone – 30% Methanol - distilled water pH = 8.38 (4 oz – 13 oz – 38 oz – 73 oz) Note 1: Chlorox bleach (6% sodium hypochlorite in water) is very corrosive to aluminum and SS. Note 2: Methanol is poisonous and toxic. I only use it in chill water systems operating below freezing. Note3: It is important to periodically (6 mos – 1 yr) flush out the old and renew the chemical additives in your system. It seems like I am always tinkering with my systems, so they never get the chance to go that long without a refill. Well there are a few facts… I hope they help answer more questions than they raise… RoboTech Last edited by RoboTech; 10-16-2002 at 08:06 PM.