Member Contributer MadScientist Posted January 10, 2016 Member Contributer Share Posted January 10, 2016 A 50:50 mix actually boils at a higher temperature that either water or anti-freeze alone... This statement is correct, right? No, that would be a high boiling azeotrope. When boiling point of the mixture is either below or above that of both substances alone, then separation becomes difficult and is by definition an azeotrope. Boiling points of water: Atmospheric - ~100 degC @ 14.6 psig - ~120 degC Boiling point of ethylene glycol Atmospheric - ~197 degC @ 14.6 psig - ~224 degC Edit: We don't use ethylene glycol directly for a couple reasons - higher viscosity than water, lower thermal conductivity, and lower specific heat. Water alone would be better choice if we didn't need to worry about freezing. The main benefit of using the mixture is the freezing point depression but most automotive coolant formulas also have the added benefits of improved lubrication, corrosion resistance, reduced surface tension, and contaminant "holding". Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted January 10, 2016 Member Contributer Share Posted January 10, 2016 My view, which has nothing to do with chemistry, is that when somebody selling something uses an inapplicable comparison (e.g., compares coolant to water that is not contained in a pressurised cooling system, compares its high-tech battery with a conventional lead-acid battery type no one uses anymore, uses a silly animated graphic showing forks bulging without a fork brace, etc.), they're engaging in hype. It's a huge turn-off for me, and undermines the credibility of whatever they're saying. If the actual product is that good, everyone will know soon enough. Which was why I mentioned that Evans Waterless Coolant has been around for ages... Ciao, Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted January 10, 2016 Member Contributer Share Posted January 10, 2016 A 50:50 mix actually boils at a higher temperature that either water or anti-freeze alone... This statement is correct, right? No, that would be a high boiling azeotrope. When boiling point of the mixture is either below or above that of both substances alone, then separation becomes difficult and is by definition an azeotrope. Boiling points of water: Atmospheric - ~100 degC @ 14.6 psig - ~120 degC Boiling point of ethylene glycol Atmospheric - ~197 degC @ 14.6 psig - ~224 degC Edit: We don't use ethylene glycol directly for a couple reasons - higher viscosity than water, lower thermal conductivity, and lower specific heat. Water alone would be better choice if we didn't need to worry about freezing. The main benefit of using the mixture is the freezing point depression but most automotive coolant formulas also have the added benefits of improved lubrication, corrosion resistance, reduced surface tension, and contaminant "holding". Great info Doc... Ethylene glycol is a major ingredient of most anti-freeze but not the only one, what's the boiling point of a 50:50 mix of an approved anti-freeze and distiiled water? I remember a graphic on the back of an anti-freeze bottle that showed the boiling point of the different mixture ratios with the peak at 50:50. ...maybe I have it backwards and it was showing the freezing point depression was greatest at 50:50, it is called anti-freeze after all Based on your info the Eth glycol actually boils at a higher temp then the waterless coolant... Link to comment Share on other sites More sharing options...
Member Contributer MadScientist Posted January 10, 2016 Member Contributer Share Posted January 10, 2016 Great info Doc... Ethylene glycol is a major ingredient of most anti-freeze but not the only one, what's the boiling point of a 50:50 mix of an approved anti-freeze and distiiled water? I remember a graphic on the back of an anti-freeze bottle that showed the boiling point of the different mixture ratios with the peak at 50:50. ...maybe I have it backwards and it was showing the freezing point depression was greatest at 50:50, it is called anti-freeze after all Based on your info the Eth glycol actually boils at a higher temp then the waterless coolant... On the freezing point side: % Ethylene Glycol : Temp 0%: 0 degC 40%: -23.5 degC 50%: -36.8 degC 60%: -52.8 degC 100%: -12.9 degC The lowest point is around 70% ethylene glycol. There will be some very minor variation in this because, as you stated, automotive coolant is not pure eth glycol. Additionally, other glycols are often mixed with ethylene glycol or completely replace it in some formulas. Propylene glycol is common and it has roughly similar freezing point performance as ethylene glycol, with greatly reduced toxicity. Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted January 11, 2016 Member Contributer Share Posted January 11, 2016 Two different brands of Honda compatible anti-freeze in my garage (Zerex & Prestone) both state the 50:50 boiling point as 265F (129C). The Zerex further clarified in the fine print that this temp is in a system with a 15 psi radiator cap... based on this data the 50:50 mix boils at 17F (9C) higher than 100% water within the pressurized cooling system. Link to comment Share on other sites More sharing options...
Member Contributer MadScientist Posted January 11, 2016 Member Contributer Share Posted January 11, 2016 Two different brands of Honda compatible anti-freeze in my garage (Zerex & Prestone) both state the 50:50 boiling point as 265F (129C). The Zerex further clarified in the fine print that this temp is in a system with a 15 psi radiator cap... based on this data the 50:50 mix boils at 17F (9C) higher than 100% water within the pressurized cooling system. Sorry, forgot you asked this too. Yes, that number (129 degC) agrees with my data as well (pure EG and H2O) at 1 atm (14.6 psig). At atmospheric, 50/50 boils at about 108 degC. There is no peak on the boiling point curve, it is roughly a parabolic curve with minimum of 120C at 0% to 224C at 100% EG. Link to comment Share on other sites More sharing options...
jerritt Posted January 21, 2016 Share Posted January 21, 2016 If water is so wonderful and waterless is so bad why does our bikes have an oil cooler. Just saying Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted January 22, 2016 Member Contributer Share Posted January 22, 2016 If water is so wonderful and waterless is so bad why does our bikes have an oil cooler. Just saying Because oil goes places that water, or antifreeze, or waterless coolant can't... and one of the many functions of oil is the transfer heat away from critical components. ... just saying. Link to comment Share on other sites More sharing options...
jerritt Posted January 22, 2016 Share Posted January 22, 2016 But how can oil cool the engine if there's no water in the oil Link to comment Share on other sites More sharing options...
Auspanglish Posted January 22, 2016 Author Share Posted January 22, 2016 Vía the oil cooler radiator maybe? Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted January 22, 2016 Share Posted January 22, 2016 But how can oil cool the engine if there's no water in the oil Link to comment Share on other sites More sharing options...
Arri Posted January 22, 2016 Share Posted January 22, 2016 For warm places, as spain, VW recomended 42% of G12 Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.