CLose but the evaporator=the radiator and the air =coolant, the slower both move(air/coolant) the longer they are in/over the evap/rad.

The cooler they both get.

Keep in mind with the a/c on max it closes the outside air door and recirculates the air in the cabin, with the fan on low and the setting on "MAX" it acts very similar to a rad, water pump setup.


David

 

evilundisguised gave you the answer. And its not the one you assumed.

The evaporator has a fixed capacity in terms of the amount of heat (BTU's) is can absorb. By running the air slower, heat absorbed by the evaporator causes the air temp to be lower. If you ran the air through faster, the air temp would not drop as much, but the total BTU's transferred would be the same. The fix capability of the evaporator to absorb BTU's results in either a large mass of air with a small temperature drop, or a small mass of air with a large temperature drop. The important thing is, no matter how fast the air is moving, the total number of BTU's of cooling remains (roughly) the same.

The A/C analogy is really not a good one.

 

The MYTH about water can flow too fast is from the days of old when the radiator cap was on the inlet of the radiator. At high rpms the flow would be restricted by the radiator and pressure would build under the cap and overflow and people assumed it had overheated.

I will try and find the source I read that from, it was a waterpump manufacturer and has been backed up by ALL the reading I have done on thermodynamics.

 

i just had to get some info from someone. in our local circle track we have cars with serious cooling systems and with no thermostat they will overheat, but putting a reducer where the tstat was will cause the engine to stay cool and not overheat. in college we had this discussion and had a instructor from a radiator company and never got the real reason.
i had to provide proof of this because they said i was nuts. i was told the water flowed to fast and would not allow the water to transfer. (it ran hotter with a tstat but did not overheat 240-250degrees)


i just want to find some publication on this(i went to college 10 years ago) hope someone has seen this

 

I was told running distilled water is better. With out the natural minerals, it wont rust as easy. Distilled water doesnt actually boil either. It reaches the temperatures to boil but without the impurities of non distilled water, it cant make the bubble effect. Whether this makes any difference or is even true, I have no idea. Just what Ive been told.

 

Somebody's been watching MythBusters. Distilled water boils at the same temperature as mildly "contaminated" water. It is possible, under very extreme conditions, to make highly distilled and filtered water, in a container with a specially prepared surface, appear not to boil until the temperature is higher than 212*F. But when that visible indication of boiling does take place, rather than a few little bubbles forming at the interface of the container and the water, there will be a fairly violent flash vaporization of water to steam, producing what almost appears to be an explosion. What you are seeing is the result of things like how much air is in the water, and what the surface of the container is made of, and how smooth it is. In extremes - no air entrainment, ultra-smooth glass container - the popular concept of boiling - formation of bubbles - may not occur until temperatures as high as 240*F. But the conditions required to achieve this had nothing to do with an automotive cooling system.

In one successful attempt to duplicate this process, the water was first double distilled (still too dirty), then passed through a molecular filter to get it really pure. It was then placed in a container that has extremely smooth surfaces. It was placed in the container slowly, to avoid air entrainment. The object was to eliminate any possibility of tiny air bubbles being left on the surface of the container, because this is where the first visible signs of boiling occur. The water, which starts turning to vapor phase at 212*F starts to mix with the air until the air gets saturated, then the "bubble" of water vapor and air detaches and floats to the surface. Without visible bubbles, you don't know what is actually happening.

All of this is irrelevant to the automotive cooling system, because the instant you pour distilled water into a rough cast iron block, the iron starts to contaminate the water. And, there is no way to prevent the presence of air bubbles when you fill the system.

Distilled water is used to eliminate contaminants that will be left behind when the water vaporizes, not to reduce rust. Those contaminants, mainly calcium, form scale on the surface of the exchanger and reduce the overall heat transfer coefficient. Distilled water is not used to reduce corrosion (rust)... in the presence of pure water, any oxygen in the system will cause the iron to oxidize even faster. In boiler systems, using deionized water, it is necessary to add oxygen scavengers to the circulating water to prevent high rates of corrosion.

 

well actually the water dosent need to be THAT pure to superheat it. NYC tap water does it at my house. my father got burned while trying to nuke some water. microwave makes it easier cause it heats it very rapidly. but as soon as an impurity like sugar or a spoon is introduced BOOM.

there were warning ads in japan about nuking water

http://youtube.com/watch?v=ZAqqpDF4bVw

also see super cooling

http://youtube.com/watch?v=lISK1YFcZBM&feature=related

 

I believe Pyrex was having some trouble with their glass being smooth enough to superheat water back in the 80's or 90's. Most microwaveable glass containers have a "seam" now to prevent that from happening.