How NASCAR Drivers Keep Cool

It’s critical for NASCAR drivers to keep their cool — mentally and physically. That’s not easy when the interior of the car can easily reach 120ºF to 130ºF.

So how do NASCAR drivers keep their cool?

Are Today’s Drivers Just Wimps?

We’re also much more aware of the dangers of heat exhaustion today than we were twenty or thirty years ago. At the same time, improvements to the car for speed and safety also make it hotter for the driver.

• The car runs hotter
  • Unleaded fuel burns hotter. The exhaust is 40-50°F hotter, which translates to a 10°F-20°F temperature rise in the car.
  • Keeping the car sealed to the ground decreases airflow under the car, which decreases under-car cooling.
  • Aerodynamics and safety issues have produced a more-tightly-sealed up car. Today’s drivers have more firewalls and less air coming in from the outside.
• Drivers utilize much more safety gear
  • Multilayer firesuits, gloves, balaclavas and close-fitting full-face helmets cover the driver from head-to-toe to protect against fire and debris.
  • Seven-point restraints keep the driver tight in the seat and don’t allow for much movement or airflow.
  • The safest seats wrap around the driver, but don’t allow much air to pass through.

Why Worry About Temperature?

Heat stroke (a body’s core temperature rising to 104 ºF or higher) can be very dangerous. Untreated, heatstroke can damage your brain, heart, kidneys and muscles. You can die.

But heat affects the human body well before it becomes life threatening. The human body wants to stay around 98.6 ºF. When it gets hot or cold, the your body has to expend energy to get the temperature back to the right place.

Surprisingly, the human body needs to exert more energy to cool itself than it does to heat itself up.

When you use energy to cool your body, that energy isn’t available for other things. Your reaction times slow and your decision-making ability decreases. Keeping drivers cool isn’t just a matter of their comfort: It directly impacts their performance and their safety.

How Air Conditioning Works

A liquid changing to a gas absorbs heat. You have to put heat into water to make it boil. The water boiling takes heat away from the stove. But water boils at a pretty high temperature.

If we had a substance that turns from liquid to gas at a lower temperature, we could use it to take heat out of warm air. That’s exactly what Freon (and its many replacement refrigerants) do. The diagram below shows a cycle, but we have to start somewhere, so lets start at the evaporator coils.

If you have a split AC (meaning some of it is outside and some is inside), the evaporator coils part of the inside unit.

• Cold, liquid refrigerant flows into the evaporator coils.
• The evaporator coils pull heat out of the air they come into contact with. A fan/blower blows the cool air where you want it to go through ducting.
• Because the liquid absorbed heat, it turns into a gas.
• The gas goes back through a compressor (outside) that uses pressure to turn it back from a gas to a liquid.
• The condenser coils extract more head from the refrigerant.
• Finally, an expansion valve cools the refrigerant further and meters how much continues into the evaporator coils.

This cycle repeats, constantly vaporizing and liquefying the refrigerant, cooling the air inside and exhausting heat to the outside.

Why This Won’t Work for Racecars

NASCAR requires driver air conditioning to provide air to either the driver’s helmet and/or the seat. Some drivers blow cool air into a cushion between them and the seat.

But NASCAR also prohibits using any type of refrigerant or pressurized gases or liquids. If the air conditioner were breached in an accident, refrigerant would escape into the atmosphere. While newer refrigerants aren’t as bad as Freon, they’re not exactly good, either.

Even if NASCAR did allow traditional air conditioners, they use huge amounts of energy. If you don’t believe that, come look at my electric bill. Crew chiefs and engineers are loathe to use engine power for anything except speed.

Air conditioning a racecar would take a lot of energy and the unit would be a lot larger than the one in your passenger car because we’re talking about getting rid of a lot more heat.

The driver isn’t going to feel much of that air if it comes out via a vent. If you put it all through his helmet, that won’t help his core (the center of the body) stay cool.

And finally, you just know the driver would be fiddling with the vent the entire race and that would driver the crew chief nuts.

So How Do NASCAR Drivers Stay Cool?

The first way NASCAR drivers deal with extreme heat is to be in good shape and stay properly hydrated. You hear them talk about their ‘hydration programs’ a lot because it is really that important.

There are three mechanism for heat transfer: conduction (two things in contact with each other), convection (the transfer of heat by a moving fluid, which could be liquid or gas), and radiation.

Radiation

Radiation is the kind of heat you get from the sun. A hot engine, exhaust pipes and oil lines all radiate heat.

Most racecars use thermal shields: materials with a thermal insulator on one side and a foil on the other to reflect heat. You will often find these materials on the floorboards and in driver heel shields.

Convection

Convection cooling is simply replacing warm air (or fluid) with cooler air (or fluid). A fan is a good example of convective cooling.

Ice

In the 1990s-2000s, as engineers were sealing up cars to improve their aerodynamics, carbon monoxide became a problem. It wasn’t unusual to have drivers become sick at the ends of races. Carbon monoxide exposure ended the career of Rick Mast. Someone came up with the idea of blowing clean, filtered air through the driver’s helmet.

And if you’re going to go to all that trouble, you might as well cool the air on its way there.

Drivers may use one NACA duct to bring air into their helmet. The air runs through an ice-packed cooler/heat exchanger before going to the fitting on the driver’s helmet. Some systems include inline filters for dust and carbon monoxide (CO) as well.

The diagram above shows all of the parts of an ice-cooled system. This one happens to do double duty by connecting to a cool shirt. We’ll get to that later.

The main disadvantage of this kind of system is (again) that ice melts. The cooling you get at the start of the race is the best you’re going to have. And these aren’t systems you can change out during a pit stop.

Thermoelectric Cooling

In a search for cooling without ice, some companies have turned to use thermoelectric cooling or the Peltier effect.

Jean Charles Athanase Peltier discovered the Peltier effect in the 1830s. He found that if you connected two different metals and ran current through the wires, one junction would get warmer and the other would get cooler. Which junction gets warmer or cooler depends on the current direction. I’ve included a more detailed explanation of the Peltier effect at the end. What you need to know is that it took about a hundred years and the development of semiconductors before Peltier’s invention became viable.

The Koolbox line uses the Peltier effect for helmet cooling, as does the Steele Racing Products Jetcool system. The primary advantages of Peltier-effect coolers is that they have no moving parts, and require no.

The disadvantage is that these systems are more expensive. The SRP product is about $8,000 and that doesn’t include the helmet.

As I mentioned before, conduction is of limited use because there’s only so much air you can put through a driver’s helmet. It does nothing for the rest of the body. And a driver with a warm core will not have a cool head, even if his head actually is pretty cold.

Conduction

Cooling by conduction just means putting something cold next to the thing you want to cool.

The lowest of low-tech conduction cooling schemes is putting bags of ice in your fire suit. They are cheap and readily available, but they they melt quickly and can get messy.

Cool Shirts/Suits

If you see a driver walking down Pit Road with a couple of tubes hanging out, chances are he or she is using a ‘cool shirt’. The shirt (or sometimes a vest) has medical grade capillary tubing sewn into it, as shown below. Cold water circulates through the suit, absorbs heat from the driver, and then returns to be re-cooled.

The cooler is literally, the same cooler shown in the first picture. It’s filled with ice at the start of the race. Most of these systems also have a control button for the driver to decrease the cooling if, say, you’re running a day to night race.

FAST makes the suit shown. It is modeled on a device developed by a surgeon who needed a lead apron during surgery because he was working with x-rays. He based his design on designs used by NASA in the space program. FAST’s version has 50 feet of tubing. Conduction depends on surface area. You want as much contact with the body as possible.

The shirt shown above is fire-resistant Carbon-X. They also come in Nomex and cotton. Some racing series don’t allow cotton, even under the firesuit, but cotton cool shirts are much cheaper.

Most cool shirt systems need between 3 and 6 Amps of power and work off the car’s 12 V system. The CarbonX shirt by FAST will cost you around $290 and the cooling system another $1250 or so.

But again, the problem is that ice melts.

The Goldilocks Solution

Traditional air conditioning systems, like the one described at the start of this post, are optimized for about 500W of cooling. Thermoelectrics are good for small tasks, but too inefficient to cool large volumes.

Personal cooling devices (like coolshirts) need to work in the 200W range of heat removal. Like many other technologies, the demand from motorsports isn’t enough to justify the basic research necessary to realize such devices.

But the sheer number of American soldiers deployed to places like the Middle East make the economics work out. A number of companies have developed cooling technology for NASA, the military or first responders. Their requirements are similar to motorsports: Small, lightweight, low power, able to operate in challenging environments, and long lasting.

Enter the mini air conditioner. Chillout offers the Quantum Pro Cooler, which weighs 10.5 lbs and takes up a volume of 438 cubic inches (11.25″ x 6.5″ x 6″). You can set the temperature on a color LCD screen and there’s a dash-mountable remote control. A big advantage of the mini system is that it uses only 1.75 oz. of refrigerant. In the case of a breach, you’re not dumping a huge amount of chemicals into the air. The controller is $3,700.

The technology I’m most excited about is from Rini Technologies. Their coolshirt (below) is controlled by the (literal) black box that contains the entire air conditioner.

That box is four pounds and 94 cubic inches (2.7″ x 5.2″ x 6.7″). The car version runs off 12V and pulls about 6A, but they also have a version that can be worn, so this device is also usable by pit crew members. They’ve basically miniaturized an air conditioner using micromachining.

Micromachining uses tools like lasers, precision computer-controlled machining and lithography to create devices with dimensions down to one thousandth of a millimeter.

The downside? About $8,000 for the cooling system.

Conclusions

Keeping your driver cool isn’t just a matter of comfort: It’s a matter of safety and performance. While brute force methods are still employed, science is providing more and more options for drivers, as well as for those in the military and emergency responders who must wear extensive PPE in extreme conditions.

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Lemma: The Peltier Effect

The Peltier effect was discovered by (duh) Jean Charles Athanase Peltier in the 1830s. He found that if you connected two different metals (as shown below), and ran current through the wires, one junction would get warmer and the other would get cooler. Which junction gets warmer or cooler depends on the direction of the current.

Here’s a schematic of what he found:

It’s a very small effect — even if you made a whole bunch of junctions. The phenomenon was of more interest from an abstract science point of view than an applications view for about a hundred years.

To get a large enough cooling effect to be useful, you need materials with good electrical conductivity and bad thermal conductivity. Most metals are good electrical and thermal conductors.

Enter semiconductors. Not just any semiconductors. Low thermal conductivity means you need large atoms, so we’re looking at materials like bismuth telluride, lead telluride, or silicon germanium. Bismuth telluride is the most used, but there are a lot of scientists looking for better materials.

Indian motorcycles offer thermoelectrically-cooled seats and Sony has a Peltier-effect personal air conditioner that fits in a pocket in your shirt. (Yes, you do have to buy special shirts.) You can even buy a thermoelectric personal-sized air conditioner on Amazon.

While their uses are limited by the amount of cooling possible, researchers continue to create better materials that will increase the cooling range and efficiency.