Just received an email from MoreBeer about their Daylight Savings sale (promo code DS15) featuring their version of an immersion chiller. They moved "the coils right to the top" because "In a traditional wort chiller, the coils rest on the bottom of the pot and the hot wort on top takes a very long time to reach them." If I had been drinking a beer, I would have done a spit-take all over my screen. I had always assumed the coils are shipped compressed together to make packaging easier, and that the first thing one does with an immersion chiller is stretch out the coils so they fit from the bottom of the kettle up to wherever the typical post-boil wort level is.
Here is my understanding of the physics. As long as you connect the chiller the correct way, with the cold water being piped straight down to the bottom and then rising up through the coils, a kettle of wort and an immersion coil forms something akin to a counter-flow chiller. The wort forms a temperature gradient with the coldest at the bottom, but the water coming into the bottom is colder, and so is still able to chill the bottom wort. The water at the top of the coil is hot, but the wort at the top of the kettle is hotter, so the hot water is still absorbing heat. The gradient formed in the wort is akin to the gradient formed in the wort line of an actual counter-flow chiller.
You should never leave the coils in contact with each other. The whole point is to expose the largest surface area possible to the wort - exchanging heat between one coil and the next defeats the purpose. When the coils are close together, in what we might call "cylinder" format, two tight, downward-moving sheaths of cool water, one outside and one inside the cylinder, will prevent the lower coils from absorbing as much heat as they otherwise would have. When further apart, in "spiral" format, the cold wort "dripping" off a coil will have better opportunity to turbulently mix with surrounding wort instead of encountering the next-lowest coil. This will help establish the desirable temperature gradient.
As is, the top-only version establishes two volumes, one that is actively cooled and one that must wait for cooled wort to rain down. If the idea is to cool all the wort, how does it not make sense to have the entire volume of wort embedded with coolant line? In my opinion, MoreBeer's version will waste time, water, and energy (if ice is used for a pre-chiller or the water is pumped out of the ground) and will increase oxidative and contaminant exposure, especially if the brewer is forced, like the most recent reviewer of MoreBeer's product, to stir it. "This performs as advertised, aside from the fact that I get substantially better performance if I stir the pot every 5 minutes with a sanitized utensil." - Andrei Kunevsky. Stirring is for whirlpooling, not cooling. Am I missing something?
Here is my understanding of the physics. As long as you connect the chiller the correct way, with the cold water being piped straight down to the bottom and then rising up through the coils, a kettle of wort and an immersion coil forms something akin to a counter-flow chiller. The wort forms a temperature gradient with the coldest at the bottom, but the water coming into the bottom is colder, and so is still able to chill the bottom wort. The water at the top of the coil is hot, but the wort at the top of the kettle is hotter, so the hot water is still absorbing heat. The gradient formed in the wort is akin to the gradient formed in the wort line of an actual counter-flow chiller.
You should never leave the coils in contact with each other. The whole point is to expose the largest surface area possible to the wort - exchanging heat between one coil and the next defeats the purpose. When the coils are close together, in what we might call "cylinder" format, two tight, downward-moving sheaths of cool water, one outside and one inside the cylinder, will prevent the lower coils from absorbing as much heat as they otherwise would have. When further apart, in "spiral" format, the cold wort "dripping" off a coil will have better opportunity to turbulently mix with surrounding wort instead of encountering the next-lowest coil. This will help establish the desirable temperature gradient.
As is, the top-only version establishes two volumes, one that is actively cooled and one that must wait for cooled wort to rain down. If the idea is to cool all the wort, how does it not make sense to have the entire volume of wort embedded with coolant line? In my opinion, MoreBeer's version will waste time, water, and energy (if ice is used for a pre-chiller or the water is pumped out of the ground) and will increase oxidative and contaminant exposure, especially if the brewer is forced, like the most recent reviewer of MoreBeer's product, to stir it. "This performs as advertised, aside from the fact that I get substantially better performance if I stir the pot every 5 minutes with a sanitized utensil." - Andrei Kunevsky. Stirring is for whirlpooling, not cooling. Am I missing something?
