“Just add Water” Pt. 1
How many of us despised that physics class? Or, decided that “I’m not really into that science-y stuff”? Well guess what? Once you own an automobile you are actually interacting with science (on a commercial scale of course). Forgive me for asking if you can recall the different types of heat transfer methods? No, no, no, this is not a test…I promise you! Stay with me and it’ll get clearer as you read on! There are 3 types of heat transfer methods:
- Conduction: Have you ever ever put a metal spoon into a wall socket? No, if not let me enlighten you…DON’T DO IT! If you have (and lived to tell the tale), the result was a very shocking one I’m sure. Well that’s conduction, where, high-speed electron particles collide with slower-speed particles (your hand) thereby transferring their energy to you. That’s why the body of your car gets hot when parked in the open on a sunny day!
- Convection: this is when you have a really heated discussion (aka argument) and you are ushered out of the space “to cool off”. Along the way you will dissipate all (hopefully!) that energy. That’s Convection! Where you allow that built up energy to ‘dissipate’ as you move to that cooler space.
- And finally, Radiation: As kids we have all done something silly usually in eye-shot of our parents and we get “the eye”! It was non-verbal, but, the intent clearly communicated to bring about adjustment! Radiation works the same way, its intent is clearly communicated through the emission of electromagnetic waves. It’s the energy that moves from one place to another like the invisible rays of the sun.
If I say anymore on heat transfer I’ll definitely scare you away, but, that’s not the reason for the lesson, your automobile’s cooling system is what we want to chat about.
Without your cooling system the excessive heat generated from the combustion process (aka ‘d’ engine running) cannot be removed quickly enough by convection (Point 2 above) to avoid engine failure. Like the bung on a pressure cooker (for those of us who cook), the cooling system is there to manage the temperature of the engine through some cleverly designed parts. Lets look at the symphony of these parts:
- The Thermostat or Temperature Regulator: as the name suggest, has a very vital role in managing the engine’s ideal temperature (usually between 81deg C and 98deg C). This is done by opening its valve when the coolant (the liquid in the radiator) temperature get to 80deg C. If the temperature is below that it keeps the valve shut deliberately as to hasten the ideal operating temperature of the engine.
- Radiator: the radiator functions on the three principles of heat transfer mentioned above. Its’ design allows hot water from the engine to come into its metal / aluminum tubes where through conduction heat is transferred from the water to the tubes (heat transfer point 1). As the name suggest, that heat now has the ability to radiate, from the fins into the surrounding environment (heat transfer point 3). That radiation process takes time, so to assist in hastening it, engineers and designers located the radiator to the front of the vehicle (in most designs). Here it can get the coolest air as the vehicle is travelling in a forward direction. For standstill traffic, they (ie engineers and designers) employ the use of a “modern” convection device (heat transfer point 2) called an engine cooling fan. The cooling fan, once running, moves the warm / hot radiated air surrounding the radiator to a cooler place. This then causes cooler air to replace the hot radiated air, this process initiates a cooling cycle where cool air continuously replaces hot air from the radiator. The result is a cooler running engine that would perform at it maximum.
- Radiator fan: the radiator fan can either be, electric and controlled by engine temperature sensors or it can be mechanical, driven by a belt and pulley from the engine. There are various and more complex versions of both but the principle of operation are the same. The only purpose of the radiator fan is to create air flow across the radiator (aka convection). The fans are usually mounted less than one inch (1") from the fins of the radiator within a shroud in the case of electric. For the mechanical fans the depth of the shroud is greater and can range from six inches (6") upwards. These fans usually are mounted to the rear of the radiator and pull cool air through the radiator causing the convection cooling effect.
- Radiator hoses and coolant lines: these lines and hoses are necessary to allow movement of coolant through the cooling system without failure. If any of these hoses fail, the cooling system fails.
- Coolant: This is the “coloured water” in your system and is the medium used to remove excessive heat from around the engine.
- Water Pump: without the water pump, nothing can happen! It is the primary mover of the medium (aka coolant) within the system and has a very critical role to play in keeping your engine cool.
- Overflow Reservoir or expansion tank: this is where excess coolant goes when the cooling system does not have an immediate need for the volume of coolant within the system.
- Radiator Cap: the radiator cap carries the ‘weighted’ responsibility of keeping the coolant within the radiator while applying a predetermined spring force on the entire cooling system. Once the cooling system overcomes that predetermined force, coolant is allowed to pass from within the cooling system to the expansion tank or overflow bottle (see point 7 above). Once the system’s pressure reduces, the radiator cap will allow the expelled coolant to return to the radiator.
Here’s a simplified cooling system flow chart for a six (6) cylinder rear wheel drive engine.
In Pt.2 we will look at the principles of operation of the cooling system (spoiler alert: it’s gonna be a lot of fun!).