WORST NAMES #3 - COOLANT

It's called radiator coolant, and it serves a useful set of purposes, but the fact is, this stuff is less effective as a coolant than water straight from the tap

The coolant in your radiator - the red stuff, the green stuff … it’s not there to assist the cooling. In fact, water on its own would do a better job just cooling your engine. The most common so-called coolant is ethylene glycol - the green stuff. (The green is fake - it’s just a dye.)

Ethylene glycol has lots of interesting properties, but carrying heat from your engine is not, frankly, one of them. It’s only about half as good as water at doing that.

Water is the commonest heavy hitter of heat transport. A technically cognizant person (every mechanical engineer on the planet) knows the specific heat capacity of water: it takes 4.18 kilojoules of energy to heat one kilo of water by just one degree C.

Allow me to translate for the non-cognoscenti: water is effing hard to heat up. It takes a shitload of heat to warm water up just a bit. Therefore, it’s the perfect fluid for moving heat away from something (like a hot engine) and into a radiator, where that heat can be rejected into the air.

When you mix ethylene glycol with water about 50:50 you actually reduce the ability of the liquid blend to carry heat away from the engine by about 25 per cent. The main reason for adding it is to drop the freezing point and raise the boiling point.

More on ethylene glycol and other radiator additives >>

That same 50:50 ethylene glycol and water mix freezes at about -37 degrees C - and it’s really good if the water in the cooling system doesn’t freeze - because it expands when it does and that often breaks expensive components from within, as well as rendering the car undriveable. So that’s bad.

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As a side benefit, together with pressurising the cooling system, a 50:50 mix of ethylene glycol in water, together with 15 PSI of pressurisation raises the boiling point - to almost 130 degrees C. It’s kinda bad if the coolant boils in the engine - it leads to a generalised class of failures fairly categorised as ‘catastrophic’.

The other chemicals in the so-called coolant also have nothing whatever to do with cooling - it’s all about the lubrication (of the water pump) plus corrosion inhibitors for the engine. Different metals close together - aluminium, steel, whatever - plus water and electrolytes is a recipe for corrosion (that’s bad).

So, in short, the so-called coolant in your engine not only does not assist in cooling the engine - it actively retards the water’s ability to transport heat from the engine to the radiator. It’s there for entirely different reasons. Calling it coolant is a bullshit expression we all use.

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WORST NAMES #2 - RADIATOR

It's called a radiator, but the fact remains that the overwhelming majority of the cooling in this baby occurs due to convection

I know: What’s he got against cooling systems? Nothing. I love me a good heat exchanger. Everything from cars to nuclear power stations use them. It’s just that radiators do not cool your engine by radiating. They’d be different if that’s how they really worked.

Heat transfer for dummies. Heat is like water - it flows. Water flows from high to low heights. Heat flows from high temperature to low temperature. Thought experiment: Imagine placing an ice cube between a stripper’s surgically enhanced and thus gravity defying breasts. Heat is transferred from the relative warmth of the symmetrical silicone choosies to the ice cube, which rapidly melts.

Always get permission from the owner of the breasts before trying this experiment in the flesh. Heat flows.

There are three mechanisms for for that flow: conduction, convection and radiation. Conduction is like, you stick a piece of metal in a fire and hold the other end. Eventually you have to let go, because the end away from the fire heats up. It’s why saucepans have insulated handles. Conduction is mainly about heat transfer in solids.

Convection is why your head gets cold in winter when you go bald. Oh, the pain… Convection is all about losing heat into a fluid (pro tip: fluids are liquids and gasses). It’s why you rug up in winter. It’s why polar bears have big, thick coats. All of that stuff helps prevent heat loss into the surrounding air. Scuba divers wear wetsuits for the same reason - to block convective heat loss.

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Radiation is like: You’re sitting in front of a fire. It feels warm because: Radiation. Hot, summer day: You go stand out in the sun. Feels hot. Walk a few feet; stand under a tree. Instant cooler feeling, right? Even though the air temperature is identical in both locations.

The leaves are just blocking the radiation, which rocketed through the vacuum of space for 500 seconds, of something. That’s the only difference.

When you look at a so-called radiator, you can tell instantly that it’s not designed to radiate - if you’re scientifically literate. For starters - it’s up the pointy end of the car, and they hacked a big hole in the front of it to facilitate airflow. That’s a big hint.

Anything involving airflow and cooling is about convection. If radiators actually rejected sufficient heat by radiating, they wouldn’t need the big hole in the front of the car. The sun doesn’t need any air to radiate its heat 150 million kilometres to earth.

If so-called radiators actually radiated effectively, they would not need fans (the fans are only there to maintain airflow when you stop in traffic). They serve no other purpose.

And you can look at the design - hot water flows through a radiator, heating up the metal tubes and the fins - these are designed for maximum surface area. Meaning maximum contact with the airflow. Convection. Convective heat loss.

Don't paint your intercooler black - it hampers convection, the primary mechanism by which the intercooler rejects heat from the compressor

INTERCOOLERS

Intercoolers - same thing - they cool by convection. Unfortunately, calling them radiators causes some people to think that perhaps it would be a good idea to paint them black, under the false assumption that this will increase their thermal efficiency by boosting heat rejection by radiation.

It doesn’t - the paint only serves as an insulator that retards the ability to cool by convection, just like wearing a jumper and going for a run on a hot day. (Bad idea.)

WORST NAMES #1 - SHOCK ABSORBER

If ‘Shock Absorber’ is not the worst name in all of automotive engineering, I don’t know what is. You think about it - you drive over a pothole: the suspension droops into the hole, then the leading edge of the wheel and tyre crash into the ridge on the far side of the pothole.

The tyre compresses, then so does the spring. These are the devices that are absorbing the shock. If it’s a big pothole and you hit it hard enough, the suspension will hit the bump stop and the rubber pad there will also attempt to absorb the shock.

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If it’s a really big pothole and you hit it sufficiently hard, you might also bend or break the wheel - that’ll help absorb the shock. (But it’s probably not that helpful overall…)

The one thing that does not help absorb the shock is a so-called shock absorber (which is really a vibration damper - hence the more correct name: the damper).

So-called shock absorbers are really there to smooth out the subsequent unhelpfully bouncy response of the spring - they don’t really do very much primary absorption of shocks.

The salient difference between springs and dampers: Springs push back with a force that’s related to their displacement - dumbing this right down: how hard they push is based on how far they’re compressed or how far they’re extended.

So-called shock absorbers push back with a force that depends on how fast they are moving. Big difference. How far versus how fast. You need one device for each kind of response.

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CONCLUSION

Maybe this is not so bad - coolant, radiator and shock absorber. It’s just a disconnect between what they are called and what they in fact do. But if this keeps up, soon nothing will make literal sense.

Of course, I welcome your input over other engineering misnomers I have omitted in the comments feed below.

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