Ethylene glycol and engine cooling

[atanatizante]

Split from the W11 speculation thread.

Going to ask a silly question here: why add glycol to F1 engine coolant anyway? In road cars, the glycol protects against freezing damage but this isn't a problem for F1 cars. Does the glycol do other things besides freeze protection? I thought that other additives were used for corrosion protection etc.

Glycol transfers heat more efficiently than water and raises the boiling point. You could go with a 100% Ethylene glycol coolant systems, like they did on the early RR Merlin engines, but that had a greater risk of fire and was more prone to leaks. When they could improve the cooling sufficiently to introduce a 70% glycol/30% water mix it solved various problems associated with using glycol by itself (I think that's when they started pressurising the coolant as well). If you went to water only, you'd need bigger radiators.

Ethylene glycol vs. Propylene glycol as engine coolant

Ethylene glycol (EG) is the main component of most coolants, having a long use, especially in the automotive industry.

Undiluted ethylene glycol has a boiling point of 197.6 ° C (387.7 ° F) and freezing point of -13 ° C (8.6 ° F). Due to its high viscosity, it carries heat by 15% less efficiently than water. Thus, its use in undiluted form would lead to overheating of the engine, with adverse implications on its operation.

By diluting the ethylene glycol with 50/50 water, the boiling point is 107 ° C (225 ° F), respectively the freezing point of -37 ° C (-34 ° F). (Boiling point increases with increasing operating pressure.)

By diluting the ethylene glycol with water in 70/30 proportion (ethylene glycol/water), the boiling point is 116 ° C (240 ° F), respectively the freezing point of -64.44 ° C (-84 ° F). At this dilution (70% concentrated antifreeze) the lowest freezing temperature is obtained. Above this ratio, the freezing point begins to increase. Thus, it is not recommended to use the coolant in concentration above 70% (by volume) antifreeze concentrate, as it decreases its ability to dissipate heat and at the same time increases the freezing point.

Also, the coolant should not be used in a concentration of less than 33% (by volume) of concentrated antifreeze, as higher dilutions decrease the concentration of corrosion inhibitors.

Ethylene glycol is a toxic compound with an oral dose of LDLO = 786 mg/kg for humans. Swallowing it can be fatal. After ingestion, ethylene glycol is metabolized to oxalic acid, which in turn is toxic (oxalic acid is the toxic component of poisonous fungi). By ingestion, the central nervous system is affected first, then the heart and finally the kidneys. Ingestion of quite small amounts can be fatal if no immediate treatment is given.

Propylene glycol (PG) is the main component increasingly used in antifreeze as it is not toxic. Due to its non-toxic nature, it is also recommended for use in cooling/heating systems in the food industry or in other systems where accidental inhalation or ingestion may occur.

Undiluted propylene glycol has a boiling point of 188 ° C (370.4 ° F) and a freezing point of -59 ° C (-74.2 ° F). Its density is 1.036 g / cm³ (Water = 1), being less viscous compared to ethylene glycol. Unlike concentrated ethylene glycol antifreeze, propylene glycol antifreeze can also be used in concentrated form for those applications that require protection at high temperatures. For these reasons, the propylene glycol antifreeze is used, in concentrated form, as a cooling agent for racing car engines. This ensures better cooling, as there is no water vaporizing in the hot area of the cylinders.

By diluting the propylene glycol with 50/50 water, the boiling point is 105 ° C (221 ° F), respectively the freezing point of -32.2 ° C (-26 ° F). (Boiling point increases with increasing operating pressure.)

By diluting propylene glycol with water to 60/40 (propylene glycol/water), the frost protection of the coolant drops to -51 ° C (-60 ° F).

And in this case too, the propylene glycol-based coolant should not be used in a concentration of less than 33% (by volume) of concentrated antifreeze, as higher dilutions decrease the concentration of corrosion inhibitors.

[PlatinumZealot]

Going to ask a silly question here: why add glycol to F1 engine coolant anyway? In road cars, the glycol protects against freezing damage but this isn't a problem for F1 cars. Does the glycol do other things besides freeze protection? I thought that other additives were used for corrosion protection etc.

Glycol transfers heat more efficiently than water and raises the boiling point. You could go with a 100% Ethylene glycol coolant systems, like they did on the early RR Merlin engines, but that had a greater risk of fire and was more prone to leaks. When they could improve the cooling sufficiently to introduce a 70% glycol/30% water mix it solved various problems associated with using glycol by itself (I think that's when they started pressurising the coolant as well). If you went to water only, you'd need bigger radiators.

I am sorry you are incorrect. Very incorrect!

[izzy]

Glycol transfers heat more efficiently than water and raises the boiling point. You could go with a 100% Ethylene glycol coolant systems, like they did on the early RR Merlin engines, but that had a greater risk of fire and was more prone to leaks. When they could improve the cooling sufficiently to introduce a 70% glycol/30% water mix it solved various problems associated with using glycol by itself (I think that's when they started pressurising the coolant as well). If you went to water only, you'd need bigger radiators.
For these reasons, the propylene glycol antifreeze is used, in concentrated form, as a cooling agent for racing car engines. This ensures better cooling, as there is no water vaporizing in the hot area of the cylinders.

actually the exact opposite is true: even propylene glycol has much worse thermal conductivity than water, like 340mW/m-K compared to 677, worse specific heat and worse viscosity too, so i don't think the higher boiling point will be enough to make it into the Mercedes. i don't suppose corrosion is much of an issue. They're all looking at nanofluids

for example:

Both glycols have lower heat-transfer efficiencies
than water and are more dense, resulting in higher volumetric flowrates or heat-exchange
areas required to maintain the same temperature levels

http://www.veoliawatertech.com/crownsol ... Glycol.pdf

[Lotus102]

To clarify, ethylene glycol transfers temperature more efficiently at higher temperatures - apologies for missing this qualification out, but I thought it was implicit. As water approaches boiling point, its cooling properties degrade substantially, so water-cooled systems have to be maintained at a lower temperature than high performance engines can be made to run at. In the unpressurised cooling systems common before WW2, the difference in boiling point between water and ethylene glycol meant that when Curtiss-Wright introduced a version of the Conqueror and D-12 engines using pure ethylene-glycol in the late 1920s, they had radiators 70% of the size of the water-cooled version. Rolls-Royce made a similar change in the 1930s partly at the behest of Vickers-Supermarine who wanted to use smaller radiators on the Spitfire than could be cooled with water, even given the lower efficiency of glycol at lower temperatures.

This is less relevant with pressurised systems, but there’s a reason glycol still forms part of the coolant of high performance engines, and it’s not just about antifreeze properties.

[izzy]

To clarify, ethylene glycol transfers temperature more efficiently at higher temperatures - apologies for missing this qualification out, but I thought it was implicit. As water approaches boiling point, its cooling properties degrade substantially, so water-cooled systems have to be maintained at a lower temperature than high performance engines can be made to run at. In the unpressurised cooling systems common before WW2, the difference in boiling point between water and ethylene glycol meant that when Curtiss-Wright introduced a version of the Conqueror and D-12 engines using pure ethylene-glycol in the late 1920s, they had radiators 70% of the size of the water-cooled version. Rolls-Royce made a similar change in the 1930s partly at the behest of Vickers-Supermarine who wanted to use smaller radiators on the Spitfire than could be cooled with water, even given the lower efficiency of glycol at lower temperatures.

This is less relevant with pressurised systems, but there’s a reason glycol still forms part of the coolant of high performance engines, and it’s not just about antifreeze properties.

there are several factors aren't there, what pressure do you think F1 systems run at? 6 bar gives a boiling point of 160C for pure water and according to https://www.process-heating.com/article ... lternative glycols degrade above 150.

Then there's this: from https://thermtest.com/thermal-conductiv ... r-mixtures
and although as you say water does taper off at higher temperatures the glycols don't get near it even at 180. Water is an amazing liquid! But so far i haven't found anything about nanoparticles in pure water

[PlatinumZealot]

To clarify, ethylene glycol transfers temperature more efficiently at higher temperatures - apologies for missing this qualification out, but I thought it was implicit. As water approaches boiling point, its cooling properties degrade substantially, so water-cooled systems have to be maintained at a lower temperature than high performance engines can be made to run at. In the unpressurised cooling systems common before WW2, the difference in boiling point between water and ethylene glycol meant that when Curtiss-Wright introduced a version of the Conqueror and D-12 engines using pure ethylene-glycol in the late 1920s, they had radiators 70% of the size of the water-cooled version. Rolls-Royce made a similar change in the 1930s partly at the behest of Vickers-Supermarine who wanted to use smaller radiators on the Spitfire than could be cooled with water, even given the lower efficiency of glycol at lower temperatures.

This is less relevant with pressurised systems, but there’s a reason glycol still forms part of the coolant of high performance engines, and it’s not just about antifreeze properties.

Thats for different reasons.
Planes have to be made freeze proof so thats why glycol is used. Also why they have to use kerosine instead of deisel if they are to be flown in cooler condition. (kerosine wont gel up when cold).

In the tropics, there are many vehicle coolants without glycol in them. Doesnt have to do with the boiling point. The systems are presurized to prevent boiling.

[Lotus102]

Thats for different reasons.
Planes have to be made freeze proof so thats why glycol is used. Also why they have to use kerosine instead of deisel if they are to be flown in cooler condition. (kerosine wont gel up when cold).

In the tropics, there are many vehicle coolants without glycol in them. Doesnt have to do with the boiling point. The systems are presurized to prevent boiling.

Kerosene is jet fuel, I’m talking about piston engines which used petrol just like car engines - RR engines started out using 85 octane and had reached about 120 octane by the end of the war. However these were unpressurised until 1941. It was pressurisation that allowed water to be able to be used in the mix again. In the US, military liquid cooled aero engines were using pure glycol systems for most of the 1930s. The UK was late to the party because they’d gone down a dead end with steam cooling until about 1936. The reason for this was better cooling with glycol, thanks chiefly to its higher boiling point. Pure glycol has a habit of leaking past gaskets though.

This is not terribly relevant to Mercedes circa 2020 so I’ll leave it there but there’s plenty of literature on the development of high performance aero engine liquid cooling in the 20th century, which is the basis for a lot of subsequent car engine technology. Chap called Calum Douglas is doing some really interesting work around 1940s engine tech with current F1 teams.

[101FlyingDutchman]

Kerosine definitely does gel up when cold! Chief reason why there are icing inhibitors added to it. Also a reason why there is a minimum fuel temperature in the tanks that the pilot has to obey. when that temp is reached, the pilot either finds a different temperature layer (normally a descend) or speed up to increase the Total Air Temperature experienced by the skin.

Not relevant to the discussion in many ways but thought I’d mention it as a comment to one of the above posters

[dans79]

Kerosene is jet fuel, I’m talking about piston engines which used petrol just like car engines - RR engines started out using 85 octane and had reached about 120 octane by the end of the war.

Just as an aside, they got it to 150 octane by late 43 or early 44, I can't remember specific dates. The mark 9 spitfires with the Merlin 66 used it to chase down V1s.

[Sierra117]

I wish you guys had the time to maybe do a podcast discussing just these fine details. I'd listen the heck out of it!

[Lotus102]

Kerosene is jet fuel, I’m talking about piston engines which used petrol just like car engines - RR engines started out using 85 octane and had reached about 120 octane by the end of the war.

Just as an aside, they got it to 150 octane by late 43 or early 44, I can't remember specific dates. The mark 9 spitfires with the Merlin 66 used it to chase down V1s.

That must've needed some serious anti-det

If memory serves, the 'emergency power' of the Merlin 130 series used on the DH Hornet was double what the earliest Spitfires had available, and without particularly exotic fuels

[Just_a_fan]

Yes, the Merlin II fitted to the Spitfire Mk1 was 1030hp, the Merlin 130/131 fitted to the Hornet was 2060hp.

Beautiful aircraft, the Hornet.

(now the thread's been moved out of the Merc thread, here's a nice piccy of the Hornet)

[PlatinumZealot]

Kerosine definitely does gel up when cold! Chief reason why there are icing inhibitors added to it. Also a reason why there is a minimum fuel temperature in the tanks that the pilot has to obey. when that temp is reached, the pilot either finds a different temperature layer (normally a descend) or speed up to increase the Total Air Temperature experienced by the skin.

Not relevant to the discussion in many ways but thought I’d mention it as a comment to one of the above posters

Diesel gels around -8 degrees Celcius.
Kerosene about -40 degrees Celcius.
If your plane is only flying in warm conditions no need for Kerosene. I think it world war two where they resorted to diesel fuel for the aircraft. Anyway..

F1 cars engines are always warmed up before starting so no need for lowering the freezing point of the coolant. Possibly all you need is some corrosion inhibitors and maybe some dispersing agents. I am pretty sure f1 coolant is very close to water anyway.

[3jawchuck]

... I am pretty sure f1 coolant is very close to water anyway.

So, you're saying that F1 engines use Budweiser as their coolant?

[PlatinumZealot]

... I am pretty sure f1 coolant is very close to water anyway.

So, you're saying that F1 engines use Budweiser as their coolant?

Only Haas. Works quite well too.