Cooling

More than 50% of energy used in combustion goes into heat[citation needed]. Heat is also generated by the turbulence of the air in the intake and cylinder, as well as friction from the engine's internals. A system is needed to keep the engine within it's operational temperature range.

Theory

Cooling systems are designed to dissipate the unwanted thermal energy. Systems are often designed around heat exchangers (HEXs), allowing for efficient exchange of heat from a hot fluid to a cooler one. There are three main methods of heat transfer;

• Conduction: Heat transfer over a temperature differential without motion between the materials
• Convection: Heat transfer over a temperature differential with fluid motion between the materials
• Radiation: Heat transfer due to by energy emitted from the unstable nature of a hot material (shitty definition, but the best I have)
  • Heat transfer in the form of electromagnetic radiation emitted by bodies above absolute 0 (wikipedia says its a function of distributing entropy, not sure we're gonna get a simple, and easy answer here)

A heat exchanger (HEX) is normally designed to optimize the heat transfer between two fluids using conduction and convection. The most common HEX is an water to air cooler, meaning it transfers heat between the hot water and the cooler air. These HEXs have a few distinct characteristics, full metal construction, thin metal fins in the streamwise direction, water inlets on top and bottom, with air inlets on the front and back. The metal construction is due to a low conductive heat transfer coefficient within the metal in addition to a low specific heat. These factors allow the metal rapidly conduct heat from the hotter internal water channels to the cooler metal fin tips. Aluminum is nearly universally used in automotive radiators. While materials such as copper may notionally provide more cooling due to higher thermal conductivity, the thermal resistance of aluminum sheet metal is so low that the heat transfer from the water circuit to the air is limited by the convective coefficients. Aluminum also is light and strong as fins or sheets. The fin structure is to maximize convection heat transfer by increasing the surface area the air flows over. The convection heat transfer coefficient is also a function of the airspeed passing the fin, allowing for 'forced convection' where a fan and or vehicle speed is used to impart an inlet speed to the system.Behavior(function?) of radiators vary heavily based upon water channel sizes, fin spacing, and a plethora of other characteristics. For a more detailed understanding of theory, any heat transfer textbook such as Incropera and Dewitt will serve. Kays and London's heat exchanger text is invaluable as a practical reference. It includes heat transfer coefficients for various fin and tube geometries. It is possible to measure the geometry of your radiator's fins, determine what type of fin geometry you are using, and then look up the appropriate set of coefficients for a rather robust heat exchanger model.

Cooling Power

The amount of thermal power that the engine puts into the water has to be the same as the thermal power the radiator dissipates at steady state.

Needed Cooling Power

A rule of thumb is 1/3 of the power you put into the engine in the form of fuel flow turns into heat. 1/3 becomes the power that turns the wheels and the last third comes out the exhaust or gets dissipated over the air [citation needed]. This ratio means that the power the radiator has to dissipate is approximately the same as the power sent to the wheels.

Keep in mind though that you don't drive full throttle all the time, so you have to average the engine power over some window of the driving event. Finding average power output of the engine is one way to determine an approximate necessary cooling power for the engine. This can be accomplished by measuring fuel consumption or engine torque/vehicle velocity (P = FxV).

Getting that Cooling Power

There are a couple of things that influence how much power the cooling system has. The best way to do this is likely to build a script in MATLAB/python and do parametric sweeps to see how your system behaves with various modifications. Some examples are:

• Radiator size: This is that you want to get right. Radiator dimensions are not created equal as lower temperature water will be cooled less than high temperature water. Therefore, increasing the width of the radiator is more economical with respect to weight than increasing the length.
• Water flow rate: Diminishing returns, if you have 0 water flow rate, you'll get close to 0 cooling no matter what else you do, if you have a properly sized water pump and swap to a bigger one, you'll see limited gains. If the water flow is too low, you won't be able to send enough heat from the engine to the radiator. Upgrading a water pump can be a serious investment in time and resources. Note that the water pumps on the stock engine are designed to pump coolant for an unrestricted engine running at significantly higher power, and these engines are designed to be run hard if they are for supersports like the 600rr. Therefore, it is unlikely but certainly possible that upgrading the water pump is a good step for your team. If you switch from a average sized pump to one with twice the flow rate you just get 1 or 2 Watt of additional power. Let's say the air has 30°C and your water 100°C when it enters the radiator and 95°C at the exit of it. Now you swap pumps and the bigger one makes the water leave the radiator at 97°C. You now have increased the temperature difference between the air and water from 67.5K to 68.5K or by 1.5%. This means your cooling power also increased by 1.5%. Measuring water flow rate is invaluable, but it is essential to understand that flow rate depends both on engine RPM and pressure rise imposed by the radiator and the rest of the cooling circuit, as these are generally centrifugal pumps.
• Airflow: A front wing could make the air go over your radiator and make the engine go boom.
  • Also shrouds are said to do stuff.
  • Fan - forced convection. Generally, fans are ideally not running during normal operation. Because the margin between running temperature (about 90C) and disaster (100C) is so tight, the fans might have to run fairly aggressively especially on a hot day when chaining autocross laps. A tight seal between fan shroud and the radiator is key to avoid leakage. Spacing between the fan and radiator is also key: you want a uniform pressure difference across the radiator to achieve a uniform flow rate.
• The angle of the radiator: You can angle it to about 30° (some even say 45°) relative to the airflow without any significant loss in cooling power. [citation needed]
• single pass v double pass

Radiator Types

cross flow / downflow radiator, radiator form factors, and why we all use them

Radiator Placement

Side

The most common radiator placement in FSAE is on the side of the vehicle, usually within the sidepod. This is a space that is usually free of other systems, somewhat unobstructed airflow, and for most bike engines it is a favorable routing position.

The sidepod design allows the team to guide air into the radiator. A properly constructed duct will dramatically increase cooling power and can reduce drag.

Rear

A few teams rear-mount the radiator. Rear mounting is usually to take advantage of diffuser airflow, free up space on the side for aero devices, or to tune weight distribution. The disadvantages can be the reduced free air flow, yaw inertia, and possible routing complications.

Multiple

As far as I know, teams that run multiple rads use one for water and one for oil. Common FS/FSAE electric mounting scheme is to run two symmetric radiators.

System Design

must be cooled w water only(IC and EV) or oil(EV).
no additives
Must be able to pass 45 deg tilt test w no leaks

Hosing

type and sizing

Routing

keep it short and straight

Ducting

Further Reading

• https://www.racetechmag.com/2017/08/willem-toet-explains-air-ducts/
• http://www.glasairproject.com/GlasairI/AirSig/CoolingSystems/cooling2/CoolingSystems2.htm

Catch Can

According to rules T.5.6, catch cans must meet the following criteria:

1. Must have a minimum capacity of 10% of the fluid being contained or 0.9 liter, whichever is greater
2. Capable of containing boiling water without deformation
3. Located rearwards of the firewall below the driver’s shoulder level
4. Positively retained, using no tie wraps or tape
5. Must vent through a hose with a minimum internal diameter of 3 mm down to the bottom levels of the Chassis.

There are commercially available solutions for automotive catch cans. There are many ways to make lighter or more package-able catch cans than what is sold off the shelf.

Data and Data collection

see Data Acquisition

Other applications

Brake cooling

• Convective
  • ducting
  • theyre spinning hot disks, they have natural convection
• Radiation

Oil cooling

Many engines have an OEM oil/water heat exchanger. From my experience with the 600rr, these are very compact and well integrated with the original powertrain system. Most teams use what is close to the manufacturer's recommended engine oil and the water coolant should be a perfectly fine substitute for the antifreeze solution on the OEM bikes.

why you would want to cool oil

• If it boils or denatures bad things happen - Novotny
• thanks, lol, just a placeholder, isnt meant to be a question, poor phrasing on my end - simon
• all good, I was confused :')

Driver cooling

lmao