“Antifreeze increases the efficiency of the heat transfer between the metal and the solution.”
Sorry, but the heat transfer equation for the film coefficient has the fluid’s thermal conductivity, density, and heat capacity in the numerator, and the viscosity in the denominator. Therefore, since water has a higher thermal conductivity, higher density, higher heat capacity, and lower viscosity than antifreeze, water clearly will transfer heat from a hot surface more efficiently than antifreeze.
(FWIT, the above is based on the Colburn form of the Sieder-Tate equation.)
[Edit: Antifreeze actually has a slightly higher density than water; see follow-on comments.]
I think you are wrong on water having a higher thermal conductivity and it certainly doesn’t have a higher density. What it has is a higher heat capacity. That means that it take more units of heat to change a given volume (or weight in the old days) of liquid by one degree.
I agree with alot of these post but you need to determine 3 things before you go any further ! is there water in your oil if there is your problem is simple cracked or warped head or blown headgasket or blown intake gasket ! if there is no water in the oil have a compression test done that will eliminate that worry ! check to see if its coming out of the exhaust ! If none of these are happening do you smell a rotine egg smell or sweet water smell inside the vehicle if so you could have a stopped up heater coil that would restrict the flow of water ciculating through the cooling system! make sure both of the cooling fans are working thats a must then install a new thermostat or your vehicle will never read the right temperature there for creating other problems with your computer system ! but with my experience with general motors as a owner and employer . sounds like you have air in your system created by not having a thermostat in the vehicle ! creating whats called a vapor lock ! trappimg air in your system!
^Except that cooling systems are designed around a ethylene glycol/H2O mix. Pure water–even under pressure–runs the risk of boiling where in contact with particularly hot metal, meaning that the metal of the cylinder wall is in contact with steam bubbles, not water. The heat transfer properties of steam are far inferior to water.
You can see this (Leidenfrost) effect for youself: lick your finger, and touch a hot iron! Your finger will not burn (at least if you’re quick about it) because the boiling spit causes your finger to effectively “float” atop the hot iron.
Yeah, Kieth, you’re right about the density. Antifreeze (50%) is about 4% more dense than pure water (red face). But the thermal conductivity of water is about 70% greater than antifreeze. This has the greatest effect on the rate of heat transfer through the boundary layer at the metal surface. By definition, the boundary layer is not hardly moving and acts as an insulating blanket between the metal and the bulk coolant. Water gets the heat from the metal to the bulk coolant faster than antifreeze.
Your thinking on the effect of heat capacity on heat transfer is not correct. Because a higher heat capacity fluid changes less in temperature with a given amount of heat added (as you correctly point out), the boundary layer and bulk fluid will remain cooler for a given amount of heat transferred into it. Therefore, the temperature difference (heat driving force) between the metal and the fluid will be greater and more heat will be transferred (greater heat transfer efficiency).
If the OP was a master mechanic or engineer they would be giving advice not requesting it. I don’t think advanced thermodynamics is helping them very much. Hasn’t their problem been solved?
“I don’t think advanced thermodynamics is helping them very much.”
Lol, Sarge, I couldn’t agree more. I just couldn’t let a statement that contradicts my years of education and experience designing heat transfer equipment go unchallenged.
insightful I am well aware of your reasons. I also have a compulsion for things to be correct. I spent 30 years dealing with military pilots who were always right even when they were wrong. As far as I recall only one was an engineer and he drove trains.
insightful, your second paragraph is correct. I stand corrected, but in my defense, you did bring this up with your first link. It was all about the thermal capacity of water over antifreeze.
I know that water is a poor conductor of heat, but I’d like to see some documentation that antifreeze is worse or that the water/antifreeze mix is worse. Sometimes two liquids when combined will work much better than either does individually.
Back in the 60’s when manufacturers began designing their cooling systems around the antifreeze/water mix, using only water would cause overheating issues. In warm climates such as SoCal, they used to sell a product in a small bottle, about a pint, that was supposed to increase the efficiency of your cooling system if you were using water only. It worked very well. Turns out you only need a small amount of antifreeze to break the surface tension of water and improve the thermal transfer between the metal and the coolant.
Surface tension does not appear in any of the formulas for the film heat transfer coefficient for a hot surface in contact with a flowing liquid (no boiling). I’ll be interested to read your source for this.
Excuse me if I missed it but I don’t believe anyone’s mentioned the water pump, of course the fans essential the thermostat, on my Firebird I thought by removing the thermostat it would run cool enough to turn the heater on a blow cold air. Wrong! I went through the entire cooling system thing colluding the water pump as well as both fan motors radiator hoses left the heater core but it sounds like with the boiling water you are not getting the circulation you need and be sure to use no less than 30 to 40% distilled water because of how well The temperature coefficient of water is. Or how well it displaces the heat as opposed to coolant itself, which I used to use only before learning about the necessity for some water. Kudos for ensuring that your radiator as well as your condenser for your air-conditioner are able to breathe but the fans are a must as well as the water pump to circulate. Also if you have a multimeter with a temperature sensor on it or a temp gun see if it is accurate with your gauge? The boiling water is a dead giveaway that it is not circulating.
Thanks for letting me reply. Good luck with your vehicle sir
-RAHOOTER
Yes both houses in theory and engineering should be hot and firm although my father has a Toyota Tacoma 1997 with 300,000 miles on it runs great but for some reason the lower radiator hose is cold when the motor is warm? I don’t get it I let it be because it’s running great if it’s not broken don’t fix it.
As for your vehicle it sounds like you may have a poor connection or a bad temperature sensor to your gauge possibly, it should run cooler on the freeway because I can breathe easier going back to the radiator and condenser, not being clogged. Your temperature gage should not fluctuate that quickly I would definitely take a look at that a poor connection to the temperature sensor (gage) on my Acura RL caused A similar issue. If it runs hot on the highway I would say definitely a radiator or your air-conditioner condenser has debris or needs to be cleaned.
Well insightful, you have overwhelmed me with data. I will have to accept your arguments even though they run counter to several personal experiences that I have had. I can only guess that the only possible explanation is that inside the engine, the metal is so hot that a boundary layer of steam is formed if pure water is used and that a glycol mix reduces that or eliminates it.
I will stand by my premise that the glycol mix may help for that reason. It won’t hurt. Since the OP has stopped participating right after he said he was going to put in the antifreeze, I have to wonder if is problem is now solved and if so, did he do anything else besides adding the antifreeze. It would be nice to hear from him with an update.
Rahooter, if the lower radiator hose is cool, that means the radiator is working. Hot coolant enters the top of the radiator and is pulled down through the cooling fins by the water pump. On its way down, it gives up heat to the outside air. By the time it gets to the bottom of the radiator and the lower hose, you want it to be cold so that it can absorb heat from the engine and keep it cool. A hot top hose and cold bottom hose is a good sign, not a bad one.