why not just cool the engine with the air directly like in the early vw beetles?
2007-11-22 09:03:17 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
Sure, you can cool by air alone. The only problem is that air cooling is not uniform. The parts of the engine closest to the incoming cool air are cooled better than the parts behind that where the air in now hotter. The water cooling system, while it has the inefficiencies of requiring two exchanges, provides a benefit of uniform cooling across all the cylinders, etc. providing for somewhat better reliability.
2007-11-22 09:08:48 · answer #1 · answered by mikey 5 · 3⤊ 0⤋
I'd like to add 1 small point that might not be well known. The air cooling of the VW beetles left cylinder #3 to the mercies of the oil cooler in front of it. This resulted in cylinder #3 getting slowly roasted to death because it could not be cooled as well as the other cylinders because of the extra heat, reduced air flow in front of it. That point was recognized, eventually, and the oil cooler was set at an angle away from directly in front of cylinder #3. Water cooling is the best way to go for current technology. It has proven itself to be the best way for well over 100 years.
2007-11-22 16:41:05 · answer #2 · answered by Anonymous · 1⤊ 0⤋
Air cooling is common in some instances but the air cooling fins don't present such a large area to the cooling process as does the huge total area of the tubing and fins within a radiator.
Water absorbs much more heat from the engine than air.
As the hot water is circulated through the radiator, the large area of the tubes and fins and, the velocity of the air passing through it, provides a high cooling effect to the circulating water.
(Note in a long traffic queue, the water temperature will begin to increase due to lack of velocity of air through the radiator, (not as quickly if an electrical cooling fan is in use)).
2007-11-22 10:53:31 · answer #3 · answered by Norrie 7 · 1⤊ 0⤋
The equation for heat transfer to/from either air or water is
Q = Mc(T2 -T1)
where
Q= heat transferred in BTU
c = Specific heat of the air or water in BTU per pound per degree F.
(T2 - T1) = Temperature change of the air or water.
M = The mass of the air or water in pounds.
Air is a very poor heat transfer medium because its c = 0. 238
BTU per pound per degree F.
Water is a very good heat transfer medium because its c = 1.0 BTU per pound per degree F, or over 4 times the heat transfer capacity of air.
Water is used inside the engine cavities to carry the heat away from the metal generated by the combustion process in the cylinders. The use of water allows much less surface area of metal to be required than if air had to be used. This makes for a smaller and lighter engine.
In the radiator where the hot water is cooled by the flow of air over the radiator fins, the heat transfer to the air can be made much more efficient because the radiator design allows for very much surface area to be available to the air passing thru the radiator. Within the engine this would not be possible.
2007-11-22 15:53:28 · answer #4 · answered by gatorbait 7 · 3⤊ 0⤋
I used to have an EJ Holden panelvan in the 1980's, it wos' grouse. Built it out of wrecks and scrap parts. Back in those days, a road worthiness certificate wasn't so tight as these days. The floor had some holes in it, so on really hot summer days, we filled the foot-well with half a bag of ice each side, (2/3 seater van), then on the passenger side chuck in a dozen stubbies of beer. The control pedals were the pendulum type, not coming out of the floor, so it all worked nicely.
2016-05-25 01:11:10 · answer #5 · answered by ? 3 · 0⤊ 0⤋
The problem with just air cooling is when the car is not moving it has a tendency to overheat and cook the oil. This was/is a problem for those cars. Motorcycles have the same problem as they are cooled only by air flow.
2007-11-22 09:35:10 · answer #6 · answered by Anonymous · 2⤊ 0⤋
In a car it is also much easier to heat the passengers with a water cooled system then an air exchange system.
2007-11-22 11:51:46 · answer #7 · answered by Wormwood 2 · 1⤊ 0⤋
because the water can save much heat than water. so water is faster in cooling for the Motor. Also the water is easier to be contained and use than a gas like air
2007-11-22 12:30:01 · answer #8 · answered by sh_sunsea 1 · 1⤊ 0⤋
Air cooling only works for relatively small engines
in a unform air flow. So cars aren't cooled by
either water or air, so much as they are cooled
by fans.
2007-11-22 09:58:07 · answer #9 · answered by Anonymous · 0⤊ 2⤋
Another advantage of water cooling is that the engine thermostat accurately controls the engine temperature and maintains it at the optimum.
2007-11-22 15:50:30 · answer #10 · answered by Tim C 7 · 2⤊ 0⤋