Originally Posted by
_ForceD_
To answer the above observations;
The quoted temps were both Fahrenheit, and it was just regular tap water (filtered from the fridge dispenser). It could be ride length...BUT...The ride when the temp was in the high 20s was a 25 mile ride. The ride when the temp was 10 degrees was only a 15 mile ride (that was all I could handle). BUT...when it froze in the 20s ride I noticed that it was frozen about halfway through that ride. In both cases there was little wind. I had thought about the sun factor. But the sun was also about the same in both cases.
Dan
If there water supercooled (granted a big "if"), the filtering may be the key. The water needs to be pure to supercool which is why the guy uses bottled water in the video. Maybe your water bottle on the first ride was slightly dirtier than the second ride.
Originally Posted by
markjenn
Well, hard to say, but there are no mysterious forces or phenomena going on here - it's simple thermodynamics - so for whatever reasons, your shorter/colder ride didn't get the bottle as cold as your longer/warmer ride. Exactly why is hard to say, but probably a combo of different starting bottle temps, length of ride, effect of head/tailwinds (tail would reduce the apparent wind on the bottle and keep it warmer longer), crosswind angle and leg shielding, variations in ambient with terrain, sun intensity/angle-to-bottle, how often you used the bottle, etc.
Significant supercooling isn't possible in this scenario.
- Mark
I wouldn't say that supercooling is impossible, just highly unlikely.
The length of the ride isn't going to be significantly different. A 15 mile ride is still going to be about an hour while a 25 mile ride is about an hour and a half. At those temperatures, the bottle would be exposed to a low enough temperature that I would suspect both to be frozen within about 30 minutes.
Side or tailwinds are going to have little effect on how quickly both bottle freeze since they are both subjected to similar wind from the bike moving through the air. Having a headwind or tailwind doesn't really have a significant effect on airflow over the bike.
You may be on to something with "how often you used the bottle", however. A full bottle has more heat mass and would take longer to freeze.
If...and, again, it's a big "if"...the bottle was supercooling, a full bottle will likely have less turbulence and less reason to crystalize than a partially empty bottle that is sloshing around.