Bong_Bong_Aircon by charlesmouse

Last crawled date: 3 years, 3 months ago

Bong_Bong_Aircon
What..?
While on a flight to Kefaloina to view a house for sale I was a bit bored. Fresh with the words of my wife in my ear "I hope it's got aircon" I set to with this design.
Important!
This is not something to 3D print, unless you should want a model for some reason.
This is a concept for a DIY household air conditioning system, I have not built it!
Concepts:
-Is it possible to make a serviceable, reliable, cheap and effecient aircon system for your home?
-Can it be done using readily available, inexpensive, parts?
-Can it be done in such a way that I can give it a silly name?
...I believe so. :-D
The basic ingredients for a Bong_Bong_Aircon are:
-Large diameter household PVC pipe, the larger the better
-Standard PVC plumbing pipe
-A couple of small PVC shower heads
-Heavy duty, preferably black, hose
-Connectors
-Something to make a large, shallow, box
-Some glass to put in the top of said box
-A couple of decent capacity household water pumps
-A couple of high capacity positive pressure fans
-Some wiring
-Calcium Chloride for making up to a roughly 35% solution in water
-A house
-Some sun
The included files are pictures to illustrate this "Thing" and a .123Dx file for 123D Design to allow anyone interested to examine the concept more closely.
Construction:
The plan is to make two "Bongs" and one box in to which the black hose will be coiled, then connected together as illustrated in the pictures and .123Dx file.
The left-most "Bong" is the one plumbed in to your house to provide the cooling and the right-most "Bong", along with your "snake in a box" is where the magic happens.
If you are mad enough to try my thoroughly untested design the "Bongs" are drawn exactly to scale and most importantly as each will be filled with fluid the piping at the bases needs careful attention - You want the connections low enough so circulation by the pumps is via the bottom of the water column in the pipes but not so low that there is nowhere for any particulates to settle for easy removal rather than running though the pumps and chewing them up.
In a running state all the tubing should be full of "water" and the "Bongs" should be filled close to the connection with the "fan pipes" but certainly not higher. You do want a reasonable amount of "water" in the system to allow for changes in height within the "Bongs" to reduce the need for regular maintenance and to be sure the pumps don't run dry - pumps rarely like this!
Explanation:
The left-most "Bong", the one connected through the wall, is what does the cooling.
-Air is drawn in via the fan (green) and blown back in to the room through the top
-The pump (again green) pumps the "water" to a shower attachment at the top of the "Bong" and the "water" sprinkles through the air flowing up through the "Bong"
This forms a basic counter current "swamp cooler". Energy required to evaporate the "water" is taken from the air circulating through the "Bong" which cools as a result. You have aircon!
Anyone who has used a swamp cooler will know they work pretty well but have one big drawback. They add a lot of moisture to the air they are cooling which makes then unsuitable for indoor applications unless you live in a very dry place...
...that's what the rest of the gubbins is for.
The "water" isn't water at all. It's a roughly 35% solution of Calcium Chloride. You can get sacks of it for buttons. This works as a liquid dessicant, so offseting the tendency of swamp coolers to add humidity to the air they are cooling. Calcium Chloride solution works very well for this job and once the system is charged is not used up so maintance is no more than occasionally ensuring the levels are correct. If there is a down side desiccating the air running through the system does cost a little energy, so reducing the performance of the cooler a little, but I don't expect that to be significant.
The rest of the Bong_Bong_Aircon is all about regenerating the desiccant. If water is removed from the cold air going in to the building it's going to end up in the Calcium Chloride solution cycling through the system. That will:
-Dilute the solution making it progressively less efficient
-Fill the system with extra water to the point where it may overflow (probably not that bad)
The diluted desiccant collects in the bottom of the left Bong, flows to the "snake-in-a-box", to be heated up a good deal by the sun. If it's heating your house and essentially free energy why not make use of it?
From the "snake-in-a-box" the hot but dilute desiccant goes to the rightmost Bong and is pumped to the top, just as with the left Bong. This Bong is constructed much like the other, but with the following very important differences:
-It's input an output are open to the external environment
-The cone-cap on the top of the left bong has two functions. To prevent stuff falling in and as a
surface for water evaporated from the desiccant to condense. The cap should be wider than the Bong tube so the condensed water drips don't end up back in the Bong!
-The air intake needs some kind of filter to prevent guk getting in, casually illustrated by a flap of wood
-Below it's shower head is a catch-tank with small holes in it to allow the desiccant to sprinkle through the Bong
-There are also some large holes to allow air to flow, more or less unobstructed, though the Bong
...and why doesn't the water drop through the large holes? Each of these will have a short length of PVC pipe glued to it so the desiccant solution can't, except in the event of an overflow.
This catch tank, in combination with the shower head above, performs two important tasks, I hope. -It allows for evaporation of the heated desiccant so getting the Calcium Chloride concentration back up
-It performs the same job as the shower head in the left Bong. Once some water has evaporated from the desiccant solution it is still going to be pretty warm so we want to use the same technique to cool it before it is circulated back to the left Bong. Although the mechanics are the same the process is different. We are using ambient air to cool the hot desiccant not the desiccant to cool the air. Yes the right Bong will "try" to function as a swamp cooler, possibly even concentrating the desiccant further, but the primary "heat flow" will be from desiccant solution to air as the temperature gradient is the other way round... I hope!
Q & A:
Q: Ok, this seems highly dodgy. I do see an issue with your pumps. How does the "water" from the left Bong flow "uphill" through the snake-in-a-box before it gets to the pump?
Fair question.
A: I arranged the layout like this partly for pleasing symmetry but mostly because Calcium Chloride solution is a good deal heavier than water. To ease the pump's job I placed it as near to the point it has to pump against gravity as possible. If the system if properly primed, no air bubbles, there should be no issue with "water" getting to the pump. If there is install the pump before the snake-in-a-box and get a bigger pump if required.
Q: Am I going to fill my house with Calcium Chloride vapor?
A: Nope! It's functioning as a desiccant so water is always flowing from the house to the Bong_Bong_Aircon.
Q: You mentioned the placement of the pipes in the bottom of the Bongs is important to allow for a particulate trap. How do I empty the traps?
A: I didn't include it in the mock-up but I would suggest putting barrel-taps right at the bottom of each Bong. Draining to remove particulates should be a very uncommon requirement and the bongs can be topped-up from the top if more fluid is needed to flush them through.
Q: Is your scheme for regenerating the desiccant really going to work?
A: I think so, probably. If it's not sufficiently effective for cooling the desiccant one can always add a radiator, possibly suspended in flowing water to help. If the desiccant itself isn't regaining sufficient concentration one could run it through a third Bong or an evaporation tank post snake-in-a-box, just be sure it's got a lid capable of directing run-off to keep the critters out.
Q: How do I regulate this thing?
A: My cunning plan it that is should be self-regulating:
-Because the circulating desiccant is exposed to external ambient air it's concentration will ultimately be dependent on ambient humidity.
-The snake-in-a-box isn't just free heating for the desiccant, being solar powered there is an element of auto-regulation there.
...paradoxically the hotter it gets the more efficient the system will become, until it's capacity to flow heat is saturated.
-One can always add a speed controller to the fan running the left Bong to adjust cooling. Even the same to the right Bong to fine-tune it's adjustment.
Q: Isn't the liquid desiccant going to evaporate away eventually?
A: Bound to. But only very slowly, and with the aid of cunning design this set up is hopefully tied to external ambient humidity making net losses even smaller.
Q: Maintenance?
A: Bound to be, but beyond keeping an occasional eye on fluid levels and build up of guk in the traps there shouldn't be much.
Q: How do I fill the darn thing?
A: Having set up your Bongs leave the connection off the top of the left Bong. Make up a darn good load of your liquid desiccant, about 35%.
-Tip a good load of the liquid in the the left Bong, don't worry if you over fill it just be sure the level is higher than your snake-in-a box.
-When it's taken as much as it can start to run the right Bong pump, preferably on a low setting at first. You should see the trap at the bottom of the right Bong start to fill as the pump runs. Do take care, most pumps really don't like being run dry!
-With the right Bong filled to an appropriate level start the left Bong pump running and watch the whole thing for a bit...
...bubbles will work their way out of the pipes and the level in each of the Bong traps should even out, fiddle with the pump settings if you need to. Add more desiccant solution until you are happy the levels are right. You can pull to cap on the right Bong if you need direct access to there.
-Once you are happy, it shouldn't take long, expect to be running both pumps at the same speed!
-Start up the fans and enjoy your Bong_Bong_Aircon!
Notes:
i) There's no reason why you couldn't scale this up or down depending on availability of pipes
ii) It should be pretty cheap to run as well as build. Swamp coolers are pretty efficient and heating the liquid desiccant is solar powered. Snake-in-a-box heating works amazingly well and if there's no sun to drive it you probably don't need the aircon running!
iii) This concept based on simple thermodynamics principles that are well understood. It should work as-is but don't forget engineers are paid to fine tune the principles physicists come up to make such things practicable. Fine tuning will be required.
iv) In an effort to simplify the whole thing I have played pretty fast and loose with the right Bong. I can't guarantee it will work as I hope. If all else fails you can add a third Bong to separate out the right Bong's two jobs for greater efficiency and control. Hell, you can ditch the right Bong all together if favor of proper evaporators and radiators for recovering the liquid desiccant. That would certainly work but would require more plumbing, pumps, and complication. I wanted to design a concept easy on the eye, easy on the mind, and easy on the wallet. Feel free to test it out and tell me if it's an utter failure or not.