I found youtuber MissouriWindandSolar to be the most informative:
In the video, he warns that one must place the 5 gallon bucket outside the room containing the dryer.
The reason for this is because if one keeps the 5 gallon bucket inside the room with the dryer, that room's humidity will increase and so will its temperature.
Imagine trying to dry your damp wet clothes in high humidity as opposed to drying your clothes in very dry air: if you place the 5 gallon bucket in the same room as the dryer, your dryer will have to work longer, increasing your electric bill.
NOTICE: IF YOU DO THIS WITH A GAS DRYER, YOU WILL DIE
BTW: One can dry their clothes on the line in the middle of the winter in places where the ambient temperature is 10 F below freezing. Yep, I know, sounds impossible but it works: your clothes will first stiffen and then dry. I saw a couple do this in the mountains of New Mexico and was completely dumbfounded that it worked (until I looked at the fact that all the moisture has been frozen out of the air)!
A dryer is being used in this house by three people who have no will to hang their clothes on a line in sub-freezing temperatures, so if one cannot convert people to one's point of view, give people an alternative which doesn't totally waste all the excess heat from drying their clothes: behold the dryer vent heater!
Whoa! that looks like a 55 gallon drum! Didn't the video say a 5 gallon bucket???
Yep, I'm lousy with instructions like that. NOT.
I sometimes use thought experiments to modify an idea. I imagined three or four over-worked, sleep deprived people bumping about a laundry room which also contains mops, brooms, etc....
This thought experiment did not bode well for a bucket, even with a liter of water, made tipsy with a single hose pulling on it.
More importantly, I want the hot air from the dryer to be as effective as it can in heating this house. Without any calculation, it would seem to me running that hot air over a dense mass such that the dense mass's temperature would rise significantly (2 or more degrees), the dense mass would radiate heat back out once the dryer turned off.
The 55 gallon drum allows me to experiment with mass and insulation whereas a smaller 5 gallon bucket pretty makes this more difficult given the conditions I have to experiment in.
Lastly, I wanted to push the hot air into another shared living space other than the laundry room. Which in this case meant I needed an exit hose of significant length so the 5 gallon design simply wouldn't provide a large enough lid for two 4" vent hoses.
Behold the 55 gallon drum dryer vent heater!
Yep, pretty much. It was that or cinnamon. Better than toluene or iodine in my opinion. Hate to read the MSDS on toluene.
Behold the 55 gallon drum vannilla dryer vent heater!
Guess which one is more expensive??
End result:-After four minutes of drying, hot air instead of cool air is vented into the shared living room;
-After one load of clothes is dried, the humidity in the shared living space goes up about 20% from the ambient humidity
-After one load of clothes is dried, the temperature in the laundry room goes up 4 F and atleast 2 F in the large shared living space (which shuts the furnance off for a minimum of 1 hr).
Conclusions:-The laundry room contains both the furnance and the water heater: by simply raising the ambient temperature 4 F for both the furnance and the water heater, I can conclude I've captured energy what would be normally vented as waste heat. This is an example of "systems feeding systems synergistically" or permaculture.
The reason the laundry room gets warmer should be obvious due to the surface area of the 55 gallon drum and the fact that no insulation was used at all on the dryer vent hoses. Clearly the laundry room is much smaller than the living room also.
-By raising the large living room by 2 F and shutting off the furnance for a minimum of 1 hour and there being three people who dry clothes once a week, I've saved the household 12 hours of furnance run time per month using waste heat.
I'll update this with real thermodynamic calculations once I get my hands on a IR thermometer. I will also be able to add things like insulation on the outside bottom of the barrel and bricks to the inside bottom to determine what the appropriate amount of mass is for high temperature heat storage.