billvelek
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I've been kicking an idea around for awhile and did a google-search but couldn't find anything directly on point. A recent post about peltier devices made me think about this again. What about coupling a peltier with a heatpipe?
For those who don't know, a 'heat pipe' is a very simple device with no moving parts and requiring no power, but which helps transfer heat from one place to another. In its simplest form, it would be a length of straight copper pipe sealed at both ends, partially filled with alcohol or freon or some other liquid to act as a refrigerant. To cool a carboy, it would be inserted into the neck of the carboy and extend from the bottom and protrude through the neck for some distance -- perhaps a foot (30cm) or a bit more. The liquid refrigerant (alcohol, freon, or whatever) pools at the bottom of the pipe, picks up heat from the fermenting wort which causes some of the refrigerant to evaporate and rise to the top (into the part of pipe extending outside the carboy) where it condenses, releasing heat to the upper part of the pipe where it is dissipated into the air, and the condensed refrigerant runs back down the pipe into the lower portion within the carboy to repeat. The cycle is continuous so long as there is a temperature differential, helping move heat from the inside to the outside of the carboy. The thinnest gauge copper would be used to improve conductivity, and even convoluted pipe could be used to increase surface area and efficiency.
By itself, I'm not sure a heatpipe would help very much because it can't cool below ambient temperature, and I can do better than that with a fan and evaporative cooling. But heatpipe performance should be improved immensely by adding a peltier device to the top portion of the pipe, and I think it would probably lower temps more than evaporative cooling, based on my readings. For those who don't know, a peltier device uses solid state electronics and a flow of direct current to move heat from one side to the other; an example is those ice chests which can be plugged into a car's cigarette lighter socket. Coupling a peltier to a heatpipe would also solve a couple of problems for people who want to use a peltier with a carboy: first, it solves the problem of how to connect to the carboy; second, it reaches to the center of the wort which is hardest to cool; third, because it runs up the center, convective currents should be uniformly distributed within the fermenter for greater efficiency and uniformity of temperature. The pipe would be easy to sanitize and since it isn't permanently mounted, the whole thing could easily be moved to other fermenters such as a bucket or a conical, if they have a sufficient opening in their lids. A thermostatic coupling for the peltier could run along the side of the pipe, thereby measuring temp at the center of the fermenter to regulate the peltier.
There are some downsides, but nothing significant in my mind. First, you won't be able to use a Burton Union on your carboy, but I don't know anyone who does anyway, even though they are available. Second, you won't be able to use a blow off tube or a conventional airlock. How bad is that? Well, if properly designed, the heatpipe should act as an airlock itself. If the pipe has a flange or is widened at the point where it enters the fermenter so that the weight of the pipe rests on a sanitized rubber gasket between it and the lid or carboy neck, I think it will provide a sufficient seal. Pressure inside the fermenter would merely lift the entire pipe and peltier device just enough to release CO2, and whenever it vents in that way, the positive pressure inside the fermenter should prevent oxygen and contaminants from entering.
Would that create too much pressure inside the fermenter, risking an explosion of the carboy? Most of the weight of the portion of the pipe which is submerged in wort would be offset by buoyancy; in fact, depending upon the gauge of the pipe and how much it is filled with refrigerant, that portion of the pipe might even have a positive buoyancy. That leaves the portion of pipe extending above the level of wort, plus the weight of the peltier, heat sink (if any), and fan. I've tried to find some weight specifications to use as examples, but unfortunately haven't found any yet. But some of these devices that are available are mounted on CPUs inside computers, and don't look like they could weigh much more than a pound -- but let's use 3 pounds (1.36kg) as an example and as an upper limit of total negative buoyancy, i.e., the weight on the gasket at the carboy neck or lid. The inside diameter of the neck on my carboys is about one and an eighth inches (2.86cm), for a surface area of .994 square inches (6.41 square cm) -- "close enough for government work" to call one square inch. Assuming three pounds of weight on that one square inch, it would require 3 psi to break the seal, causing a pressure of 3psi throughout the carboy. I tried to research whether that was too much or not, and couldn't find an answer; I did find this thread -- http://tinyurl.com/fvned -- which was inconclusive. But assuming that 3psi is not too much, the pipe and peltier should cause a good seal. Now, another bad downside with not being able to use a blow off tube is that, with a really vigorous fermentation, each time the seal is momentarily broken to vent pressure, we're likely to have some kraeusen squirt out; this can at least be deflected downward by adding to the heatpipe a small sleeve which overhangs the neck of the carboy, but then we would still have a mess with kraeusen running down the sides of the carboy -- although it could be set inside a small pan or tub to minimize the mess. However, if the heatpipe and peltier are successful in holding the temp of the wort down to a nice low temp of, let's say, 64F/18C, will fermentations really be that vigorous? I don't know because I've never been able to ferment that low; I've had some pretty violent fermentations, but I've seldom been able to keep my temp down below 70F/21C. With lower temps, fermentations will be slower, but I don't know how slow.
This is just some thinking on my part; I've never attempted any of this and don't know if it would work or not. Seems to me like it would, and I'd love for some of the more knowledgeable engineering types here to comment on this. If anyone thinks they can make this work and market it, you have my permission; just send me a 'beta' unit to try out. ;-) Also, if anyone tries this, please let me know how it works out. I might give it a try myself, but I'll need to find out a lot more about how to make the heat pipe -- how much liquid to put in it, etc. But there's no sense in even trying if calculations say it won't work.
I'm posting this to a lot of forums to try to get as many responses as possible. Also, I'm sorry this is so long; I hope you folks don't mind.
Thanks.
Cheers, Bill Velek
Join "HomeBrewers" international grid-computing team and help mankind by donating spare computer power for medical research such as cancer; we're in the top 8%, and we beat the MillerTime team: http://tinyurl.com/b7ofs The life that your computer can help save ... might be someone you love.
For those who don't know, a 'heat pipe' is a very simple device with no moving parts and requiring no power, but which helps transfer heat from one place to another. In its simplest form, it would be a length of straight copper pipe sealed at both ends, partially filled with alcohol or freon or some other liquid to act as a refrigerant. To cool a carboy, it would be inserted into the neck of the carboy and extend from the bottom and protrude through the neck for some distance -- perhaps a foot (30cm) or a bit more. The liquid refrigerant (alcohol, freon, or whatever) pools at the bottom of the pipe, picks up heat from the fermenting wort which causes some of the refrigerant to evaporate and rise to the top (into the part of pipe extending outside the carboy) where it condenses, releasing heat to the upper part of the pipe where it is dissipated into the air, and the condensed refrigerant runs back down the pipe into the lower portion within the carboy to repeat. The cycle is continuous so long as there is a temperature differential, helping move heat from the inside to the outside of the carboy. The thinnest gauge copper would be used to improve conductivity, and even convoluted pipe could be used to increase surface area and efficiency.
By itself, I'm not sure a heatpipe would help very much because it can't cool below ambient temperature, and I can do better than that with a fan and evaporative cooling. But heatpipe performance should be improved immensely by adding a peltier device to the top portion of the pipe, and I think it would probably lower temps more than evaporative cooling, based on my readings. For those who don't know, a peltier device uses solid state electronics and a flow of direct current to move heat from one side to the other; an example is those ice chests which can be plugged into a car's cigarette lighter socket. Coupling a peltier to a heatpipe would also solve a couple of problems for people who want to use a peltier with a carboy: first, it solves the problem of how to connect to the carboy; second, it reaches to the center of the wort which is hardest to cool; third, because it runs up the center, convective currents should be uniformly distributed within the fermenter for greater efficiency and uniformity of temperature. The pipe would be easy to sanitize and since it isn't permanently mounted, the whole thing could easily be moved to other fermenters such as a bucket or a conical, if they have a sufficient opening in their lids. A thermostatic coupling for the peltier could run along the side of the pipe, thereby measuring temp at the center of the fermenter to regulate the peltier.
There are some downsides, but nothing significant in my mind. First, you won't be able to use a Burton Union on your carboy, but I don't know anyone who does anyway, even though they are available. Second, you won't be able to use a blow off tube or a conventional airlock. How bad is that? Well, if properly designed, the heatpipe should act as an airlock itself. If the pipe has a flange or is widened at the point where it enters the fermenter so that the weight of the pipe rests on a sanitized rubber gasket between it and the lid or carboy neck, I think it will provide a sufficient seal. Pressure inside the fermenter would merely lift the entire pipe and peltier device just enough to release CO2, and whenever it vents in that way, the positive pressure inside the fermenter should prevent oxygen and contaminants from entering.
Would that create too much pressure inside the fermenter, risking an explosion of the carboy? Most of the weight of the portion of the pipe which is submerged in wort would be offset by buoyancy; in fact, depending upon the gauge of the pipe and how much it is filled with refrigerant, that portion of the pipe might even have a positive buoyancy. That leaves the portion of pipe extending above the level of wort, plus the weight of the peltier, heat sink (if any), and fan. I've tried to find some weight specifications to use as examples, but unfortunately haven't found any yet. But some of these devices that are available are mounted on CPUs inside computers, and don't look like they could weigh much more than a pound -- but let's use 3 pounds (1.36kg) as an example and as an upper limit of total negative buoyancy, i.e., the weight on the gasket at the carboy neck or lid. The inside diameter of the neck on my carboys is about one and an eighth inches (2.86cm), for a surface area of .994 square inches (6.41 square cm) -- "close enough for government work" to call one square inch. Assuming three pounds of weight on that one square inch, it would require 3 psi to break the seal, causing a pressure of 3psi throughout the carboy. I tried to research whether that was too much or not, and couldn't find an answer; I did find this thread -- http://tinyurl.com/fvned -- which was inconclusive. But assuming that 3psi is not too much, the pipe and peltier should cause a good seal. Now, another bad downside with not being able to use a blow off tube is that, with a really vigorous fermentation, each time the seal is momentarily broken to vent pressure, we're likely to have some kraeusen squirt out; this can at least be deflected downward by adding to the heatpipe a small sleeve which overhangs the neck of the carboy, but then we would still have a mess with kraeusen running down the sides of the carboy -- although it could be set inside a small pan or tub to minimize the mess. However, if the heatpipe and peltier are successful in holding the temp of the wort down to a nice low temp of, let's say, 64F/18C, will fermentations really be that vigorous? I don't know because I've never been able to ferment that low; I've had some pretty violent fermentations, but I've seldom been able to keep my temp down below 70F/21C. With lower temps, fermentations will be slower, but I don't know how slow.
This is just some thinking on my part; I've never attempted any of this and don't know if it would work or not. Seems to me like it would, and I'd love for some of the more knowledgeable engineering types here to comment on this. If anyone thinks they can make this work and market it, you have my permission; just send me a 'beta' unit to try out. ;-) Also, if anyone tries this, please let me know how it works out. I might give it a try myself, but I'll need to find out a lot more about how to make the heat pipe -- how much liquid to put in it, etc. But there's no sense in even trying if calculations say it won't work.
I'm posting this to a lot of forums to try to get as many responses as possible. Also, I'm sorry this is so long; I hope you folks don't mind.
Thanks.
Cheers, Bill Velek
Join "HomeBrewers" international grid-computing team and help mankind by donating spare computer power for medical research such as cancer; we're in the top 8%, and we beat the MillerTime team: http://tinyurl.com/b7ofs The life that your computer can help save ... might be someone you love.
