sharpstick
Computer
- Apr 23, 2008
- 4
(I apologize if this is too DIY or low tech for this forum. I hope it will be seen as at least an academic challenge/puzzle and not a target for insults like happened on another forum!)
My goal is to optimize the design of a portable swamp cooler to my camping setup, for portability, cost, and efficiency.
Burning Man has been an accelerated testing ground for technology for a while. Even the military are rumored to send observers. (They supposedly discovered the Camelbak there.) Up to 50k+ imaginative burners come back every year fine tuning their designs for comfortable desert living. Swamp cooler design is one great example of crowd sourced, internet accelerated engineering. Each year, the latest design tweaks show up, results are observed by their builders and others. Then the results are shared and discussed online, new tweaks are invented and the cycle repeats.
I'm starting with a fairly well tested design that's been used for several years, Figjam's 12 volt system, recapped on page 51 of the eplaya forum:
I'm adapting this design to my situation, which is a bit different.
- Instead of a full size cabin tent or hexayurt(700+ sq ft), I have been using a tent within a tent for several years, basically a large piece of housewrap suspended from the cabin tent, draped over an air mattress and tucked under at the edges. It has overlapping flaps on the sides for entry, or can be pulled completely out of the way to allow cross ventilation. It has an interior bamboo spreader pole over the head end, and I'm generously calling it an average height of 2 ft. (about 75 cu ft max, probably more like half of that). Figjam calls for a fan that will replace the air inside the space every 3 to 5 minutes. For my tent, that would be no more than 10 to 30 cfm. (He uses a 190CFM muffin fan) I'm happy to overkill design and loosen the fan to lower air output if needed.
My main question is fine tuning the efficiency. Typically this design is reported to give a 20 to 30 degree decrease over ambient incoming temp. I'd like to maximize that. My cooled space is very small, so a large volume of air is not needed, as in larger spaces. I'm thinking that the slower the air passes through the wet media, the more it is humidified and cooled. Too fast, not cool enough, and it passes through the tent too fast. Too slow, and not enough air passes through.
- I have access to 110VAC power in my camp, so am using AC components. My pump is a 132gph fountain pump. I'm putting a TEE and a valve at the outlet so I can bleed off extra flow. The drip ring only needs enough to keep the entire mat damp. I'll be carrying 12 volt backup pump and blower with a DC adapter also. The playa eats technology, redundancy is essential! This will also make it easier to convert to DC someday if I want to.
- I plan to have a float switch to prevent dry running in a second bucket reservoir and a siphon loop connecting them. This should give me twice the water capacity. (If I can remember to check the water daily, I might be able to forgo the switch.)
- My system will have a thermostat to narrow the range. No sense in overcooling. I have an old ductstat that should work. I have a digital Ranco controller I use for homebrewing, but that would be overkill.
- I travel from Florida so weight of cargo is critical. We now have a rental storage unit so can leave stuff out there, but there is no way we can store batteries effectively.
Why a swamp cooler? To keep cool in a tent in the desert where afternoon temps may be 100+ degrees. Swamp coolers, aka evaporative cooling have been in use commercially for decades, actually centuries, in arid climates. People who live in Florida will find it hard to believe!
Why not an AC? AC, even a small unit, requires more power than the average camper has available. It takes a considerable amount of equipment and fuel to run even the smallest of window units. A swamp cooler powerful enough to cool a shaded tent or hexayurt fits in a 5 gallon plastic bucket and the fan and pump can be run with a small solar panel or battery pack.
My goal is to optimize the design of a portable swamp cooler to my camping setup, for portability, cost, and efficiency.
Burning Man has been an accelerated testing ground for technology for a while. Even the military are rumored to send observers. (They supposedly discovered the Camelbak there.) Up to 50k+ imaginative burners come back every year fine tuning their designs for comfortable desert living. Swamp cooler design is one great example of crowd sourced, internet accelerated engineering. Each year, the latest design tweaks show up, results are observed by their builders and others. Then the results are shared and discussed online, new tweaks are invented and the cycle repeats.
I'm starting with a fairly well tested design that's been used for several years, Figjam's 12 volt system, recapped on page 51 of the eplaya forum:
I'm adapting this design to my situation, which is a bit different.
- Instead of a full size cabin tent or hexayurt(700+ sq ft), I have been using a tent within a tent for several years, basically a large piece of housewrap suspended from the cabin tent, draped over an air mattress and tucked under at the edges. It has overlapping flaps on the sides for entry, or can be pulled completely out of the way to allow cross ventilation. It has an interior bamboo spreader pole over the head end, and I'm generously calling it an average height of 2 ft. (about 75 cu ft max, probably more like half of that). Figjam calls for a fan that will replace the air inside the space every 3 to 5 minutes. For my tent, that would be no more than 10 to 30 cfm. (He uses a 190CFM muffin fan) I'm happy to overkill design and loosen the fan to lower air output if needed.
My main question is fine tuning the efficiency. Typically this design is reported to give a 20 to 30 degree decrease over ambient incoming temp. I'd like to maximize that. My cooled space is very small, so a large volume of air is not needed, as in larger spaces. I'm thinking that the slower the air passes through the wet media, the more it is humidified and cooled. Too fast, not cool enough, and it passes through the tent too fast. Too slow, and not enough air passes through.
- I have access to 110VAC power in my camp, so am using AC components. My pump is a 132gph fountain pump. I'm putting a TEE and a valve at the outlet so I can bleed off extra flow. The drip ring only needs enough to keep the entire mat damp. I'll be carrying 12 volt backup pump and blower with a DC adapter also. The playa eats technology, redundancy is essential! This will also make it easier to convert to DC someday if I want to.
- I plan to have a float switch to prevent dry running in a second bucket reservoir and a siphon loop connecting them. This should give me twice the water capacity. (If I can remember to check the water daily, I might be able to forgo the switch.)
- My system will have a thermostat to narrow the range. No sense in overcooling. I have an old ductstat that should work. I have a digital Ranco controller I use for homebrewing, but that would be overkill.
- I travel from Florida so weight of cargo is critical. We now have a rental storage unit so can leave stuff out there, but there is no way we can store batteries effectively.
Why a swamp cooler? To keep cool in a tent in the desert where afternoon temps may be 100+ degrees. Swamp coolers, aka evaporative cooling have been in use commercially for decades, actually centuries, in arid climates. People who live in Florida will find it hard to believe!
Why not an AC? AC, even a small unit, requires more power than the average camper has available. It takes a considerable amount of equipment and fuel to run even the smallest of window units. A swamp cooler powerful enough to cool a shaded tent or hexayurt fits in a 5 gallon plastic bucket and the fan and pump can be run with a small solar panel or battery pack.
