Coolant

August 18, 2006

What brand of coolant do we all use. And at what mix rate. Seems to be vaying opinions on this.

regards

gtblu

PaulN · August 19, 2006

Interesting you should ask. I've been observing a few CT flyers discussing coolants on their forum. Apparently some of them fly from "hot" locations and have been experiencing overly warm CHTs. Theyare of the mind thatthe fix is to use a coolant called Evans NPG which they say keeps its cool better than normal glycol.

I have discussed this with Wal from Bert Flood Imports who reckons that unless I am operating in anabnormally hotclimate (which I think Cooma is not) the Rotax is quite happy with normal glycol. He is willing to part with the Evans product but warns that the system must be flushed of old coolant before changing over ... and the cost is a bit scarey ($80 per US gallon for the coolant and $53 for the same amt of flushing liquid).

On his advice I have recently replaced my old glycol coolant with the same (Nulon, 1060gm glycol per litre). On the advice of my Level 2 I've added a little water (4 parts glycol: 1 part water). He tells me that with added water the coolant removes heat more efficiently.

Paul

hiperlight · August 19, 2006

I think it is important to understand that themost effective'coolant' is pure water.

Glycol is added to reduce the freezing temperature of the coolant.

But glycol also reduces the efficiency of the water as a coolant. Other additives areused to provide inhibitors to electolysis. These also reduce the effectiveness of the water as a coolant.

Cooling systems are pressurised to increase the boiling temperature of water.

The answer is to use water with the minimum of glycol and inhibitors to provide the required protection.

Difficult to determine I know, but if these facts arekept in mind you willcreatethe most effective coolant for each application.

Bruce

Admin · August 19, 2006

Boiling Point Elevation in Solutions

The boiling point of pure water is 100Ã‚Â°C, but that boiling point can be elevated by the adding of a solute. A solution typically has a measurably higher boiling point than the pure solvent.

A treatment of boiling point elevation is given by Ebbing. The boiling point elevation DTb is a colligative property of the solution, and for dilute solutions is found to be proportional to the molal concentration cm of the solution:

DTb = Kbcm

Where Kb is called the boiling-point-elevation constant.

Solutions may be produced for the purpose of raising the boiling point and lowering the freezing point, as in the use of ethylene glycol in automobile cooling systems.

The ethylene glycol (antifreeze) protects against freezing by lowering

the freezing point and permits a higher operating temperature by

raising the boiling point.

Gee I feel smarter now ;)

hiperlight · August 19, 2006

Unless your engine and cooling systemare made ofthesamehigh quality stainless steel DO NOT ADD A SALT TO THE COOLANT.

Bruce

PaulN · August 19, 2006

That's all Greek to me Ian . PaulN

August 19, 2006

So from that the suggestion is that even though you have a higher boiling point, the heat is transferred less efficiently with more glycol?

Wilfred · August 20, 2006

I have used the Valvoline product on beach vehicles with a noticable improvement in cooling efficiency

<T>

<TR>

</TD>

Valvoline Racing Super Coolant is a cooling system corrosion inhibitor concentrate race-tested by Valvoline's Winston Cup team. It is proven to provide a 25% improvement in heat transfer over conventional glycol-based engine coolants. Available at NAPA.

<UL>

<LI>Provides advanced anti-corrosion protection

<LI>Formulated to provide improved heat transfer

<LI>Prolongs the working life of water pumps and heat exchangers

<LI>Track-tested and proven by the Valvoline's NASCAR team </LI>

<T>

<TR>

<TD>Part Number</TD>

<TR>

<TR>

hiperlight · August 20, 2006

Hello gtblu

The following is an extract from

www.koolance.com/technical/cooling101/102.html

Thermal Conductivity

Thermal Conductivity is the amount of heat a particular substance can carry through it in unit time. Usually expressed in W/m K, the units represent how many Watts of heat can be conducted through a one meter thickness of said material with a one Kelvin temperature difference between the two ends.

(Note: "Thermal Conductivity" is the measure of heat flowing through a length, not to be confused with "Thermal Conductance", which is the measure of heat though a surface.)

<T>

<TR>

<T>

<TR>

<T>

<TR>

Solids </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=122 height=6>Diamond</TD>

<TR>

<TD width=122 height=19>Silver</TD>

<TR>

<TD width=122 =#cae4ff height=19>Copper</TD>

<TR>

<TR>

<TD width=122 height=19>Aluminum</TD>

<TR>

<TD width=122 height=19>Iron / Steel</TD>

<TR>

<TR>

<TR>

<TD width=122 height=19>Concrete</TD>

<TR>

<TR>

<TD width=122 height=19>Carbon</TD>

<TR>

<TD width=122 height=19>Glass</TD>

<TR>

<TD width=122 height=19>Rubber</TD>

<T>

<TR>

<T>

<TR>

Liquids </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=140 height=6>Mercury</TD>

<TR>

<TD width=140 =#cae4ff height=19>Water</TD>

<TR>

<TD width=140 height=19>3M Flourinert FC-43</TD>

<TR>

<TD width=140 height=19>Methanol</TD>

<TR>

<TD width=140 height=19>Glycol, Antifreeze</TD>

<TR>

<TD width=140 height=19>Ethanol</TD>

<TR>

<TD width=140 height=19>Liquid Nitrogen</TD>

<T>

<TR>

<T>

<TR>

Gases </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=122 height=6>Hydrogen</TD>

<TR>

<TD width=122 height=19>Helium</TD>

<TR>

<TD width=122 height=19>Oxygen</TD>

<TR>

<TD width=122 height=19>Nitrogen</TD>

<TR>

Specific Heat Capacity

Specific Heat Capacity is the amount of heat a particular substance can hold. Typically expressed in kJ/kgK, the rate depicts how many kilojoules of energy are required to change the temperature of one kilogram of said substance by one Kelvin.

<T>

<TR>

<T>

<TR>

<T>

<TR>

Solids </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=122 height=6>Human Body (avg)</TD>

<TR>

<TD width=122 height=19>Concrete</TD>

<TR>

<TR>

<TR>

<TD width=122 height=19>Rubber</TD>

<TR>

<TD width=122 height=19>Aluminum</TD>

<TR>

<TD width=122 height=19>Glass</TD>

<TR>

<TD width=122 height=19>Carbon</TD>

<TR>

<TD width=122 height=19>Diamond</TD>

<TR>

<TD width=122 height=19>Iron / Steel</TD>

<TR>

<TD width=122 =#cae4ff height=19>Copper</TD>

<TR>

<TD width=122 height=19>Silver</TD>

<TR>

<TR>

<T>

<TR>

<T>

<TR>

Liquids </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=140 =#cae4ff height=6>Water</TD>

<TR>

<TD width=140 height=19>Methanol</TD>

<TR>

<TD width=140 height=19>Ethanol</TD>

<TR>

<TD width=140 height=19>Glycol, Antifreeze</TD>

<TR>

<TD width=140 height=19>Liquid Nitrogen</TD>

<TR>

<TD width=140 height=19>Benzene</TD>

<TR>

<TD width=140 height=19>3M Flourinert FC-43</TD>

<TR>

<TD width=140 height=19>Freon 11</TD>

<TR>

<TD width=140 height=19>Mercury</TD>

<T>

<TR>

<T>

<TR>

Gases </TD></TR></T></TABLE></TD></TR>

<TR>

<TD width=122 height=6>Hydrogen</TD>

<TR>

<TD width=122 height=19>Helium</TD>

<TR>

<TD width=122 height=19>Steam (at 110<SUP>o</SUP>C)</TD>

<TR>

<TD width=122 height=19>Nitrogen</TD>

<TR>

<TR>

<TD width=122 height=19>Oxygen</TD>

What do all of these numbers mean in a liquid cooling system?

The above thermal conductivity shows why copper is the preferred cold plate material for cooling systems. It is extremely close to silver in performance, but only 1/6 the cost. Like most metals however, copper doesn't hold heat for very long-- it needs to be absorbed by something else.

The specific heat capacities show water to be the best liquid for holding heat. Practically, it is also the best for transferring it.

This would indicate the ideal configuration is to use copper to transfer heat from the processor, and to use water to absorb and move away the heat. Although there are many other factors involved, here you have the basic foundation of a liquid cooling system.

Bruce

Yenn · August 20, 2006

A lot of theory here, but how relevant is it. What we need obviously is a copper engine with water as the coolant, but what we have is a largely aluminium engine and that does not fit well with copper as there will be massive corrosion in very short time.

I don't have the problem using an air cooled engine but personally would stick with a water glycol mix having used it in cars with aluminium heads for many years, but even a high glycol mix can freeze in the bottom of a car radiator leading to the rest of the system boiling.

hiperlight · August 20, 2006

Hello Yenn

The article is an extract from the link given. If you read the last paragraph of the extract again and then read the rest of the article on the website you will get a complete picture.

Glycol in a cooling system oxidises with timeand becomescorrosive tothe point of destroying your engine. That is why premixed coolants have additives to, inter alia, neutralise those oxides.

If the high glycol mix in your engine is freezing in the bottom of your radiator to the point of blocking it then I suggest you get hold of a glycol refractometer and test the coolant.

Fiddling with coolant mixes without a reasonable knowledge of the 'theory' is quite risky.

Bruce

August 20, 2006

It would appear to me that air-cooled may be the way to go because to run a water-cooled engine you almost need to be an industrial chemist or at least know one.

Don

Admin · August 20, 2006

to run a water-cooled engine you almost need to be an industrial chemist or at least know one.Don

006_laugh.gif.0f7b82c13a0ec29502c5fb56c616f069.gif

August 20, 2006

Thanks guys, I appreciate the effort. I was concerned because my engine came back on Friday from Bert Floods after re-haul and seemed to have some corrosion in the pipes especially, or mostly anywhere that was covered by rubber as in the hoses!

What now, well I think I'll use a 50/50 mix water to glycol with alloy protection in it.

regards

gtblu

Wilfred · August 20, 2006

Why not just stick to the engine manufacturers specifications

The coolant specs fpr the engines are clearly laid out in the operating manuals.

Rotax are very clear with their requirements.

In a 912 the rotax manual staes the recommendations

http://www.rotax-aircraft-engines.com/pdf/dokus/d03377.pdf

hiperlight · August 20, 2006

HEAR, HEAR!!

Unless your engine is solid cast iron with a copper radiator and built before 1955 stick to the manufacturer's recommendations for coolants (including change times).

Bruce

August 20, 2006

Because even within that document there is a note that allows latitude and contradictions depending on the aircraft! 10.2.1 page 39

It's not that simple unfortuneately

regards

gtblu

Wilfred · August 20, 2006

I think it is that simple

Unless you have an obscure engine and aircraft, talk to the manufacturer and use what they recommend

PaulN · August 20, 2006

Even the manufacturer is inclined to change recommendations. For example, from the link that Turtle provides Rotax recommends (not specifies) 100% Evans NPG. My hard copy Rotax manual that came with the CT specifies (not recommends) 50% antifreeze and 50 % pure water. Wal at Bert Flood's (Aust Rotax agent) advises use normal antifreeze as opposed to the Evans product, providing the operating environment is "normal" conditions but consider Evans NPG if operating environment is hot and you have difficulty holding CHT within limits.

Paul

August 20, 2006

Hi all

Why not make use of electrolytic potential of different metals? Instead of working against it?

i.e. use a bar/plug of zinc as a sacrificial anode. (Repco actually sells these for new generation alumium radiator equipped vehicles) Sure would beat using aluminium (engine) as the sacrificial anode. (cathode is slighty different grades of aluminium, head gasket, steel bolts even carbon inclusions or whatever that can create a reaction inc gases.

Also the specific heat capacity of water is far in excess of glycol although glycol does change the boiling/freezing point when added so some isn't such a bad thing.

As for radiators, my preference is brass (traditional) but all manufacturers are basically turning out aluminium ones now (lighter) so need a much better solution than just adding corrossion inhibitor.

Just an idea

August 21, 2006

Also,it seems essential to use demineralised water.

Geoff · August 21, 2006

Mount a Jabiru engine in your plane problem solved.

August 21, 2006

Yes, If they could be fitted i'd put in the sacrificialzinc anoides. i had a pair of Yanmar 3 cyl diesels that were raw water cooled (salt water). They had three fitted to each engine. They would last six months. These engines ran at least 10 hrs every day. A similar engine that was not fitted with them fell apart in 18mths and it only ran half the time of the Yanmars.

I think that a lot of the corrosion that takes place in alloy engines is sped up a bit by the electrolises effect caused by the electrical system.

The above diesels were wired "above earth" during a refit and this improved the corrosion problem heaps. unfortunatly i doubt if you could get a petrol engine to run wired this way.

The only thing i would add if fitting the zinc plugs (alka selza tablets) is to fit a filter screen to stop the zinc particles from going thru the water pump. good point to consider by migrace

Ozzie

BlueSideUp · August 24, 2006

Have been using Evans for a while and it seems fine. While expensive it does not have a "life" like coolant.

It also provides some peace of mind when the CHT goes up on a long climb on a warm day.

Then again what ever works for you

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