As a happy resident of sunny Florida I have to deal with the side effects of a hot an humid weather most of the year; as a result I spend a fair amount of money (and electricity) on AC (turning my AC on, costs me $100 a month). This year so far I've been able to go by with fans (which are substantially cheaper to operate) but soon those will only circulate hot air.
I've been looking for alternatives and one I found is water cooled air systems, but those tend to be extremely expensive ($500 - $2500), therefore I'm thinking on doing one myself.
My idea is to use a car radiator (I found this (http://www.autopartswarehouse.com/search/?Ntt=W0133-1650774&N=0&uts=true) for ~$60) a cheap electric water pump and with a simple reservoir and a regular fan make the system.
Does anyone know something on the subject? Any recommendations? Warnings?
What's the plan? The radiator goes in the house with the fan blowing air over it , while on the roof the reservoir side is open to evaporation? Or the fan blows outside air over the reservoir?
Don't know much about A/C but would suspect that the high ambient humidity you talk about might sink the idea, and that you might even get a temperature gain from the water pump heat generation (unless it's outside). A typical central heating pump (at least in the U.K.) dumps about 0.1KW when running.
I'd suggest a Google search for "evaporative cooler" and/or check if anyone else uses them in Florida, or only in more arid places.
There are loads of evaporative coolers on the intreweb - the downside seems to be water is heavy, but that is from a fatigued person's viewpoint.
I dont have any idea how much my unit (non-evaporative, no outside unit either, a gem) costs to run. It was supposed to increase the value of my home but that's gone pear shaped - lack of hot weather and economic downturn in the housing market.
You may do better to wait til global warming kicks off the imminent ice age Zono.
Actually I was thinking in something far simpler: a fan blows air into the radiator which cycles cool water from the reservoir which can be open and even (manually) receive ice from the fridge, all indoors as a single unit. I'll have to make a duct and use a high flow fan.
I imagine that the downside is the noise of the fan, but if I can make the air cooler by 8-10C and the power usage is lower it could be functional. I would be counting on the ice maker from the fridge but that energy (to power the fridge) is already been used. I guess I'm also counting with a level of de-humidification from the system provided that the water pump will not end up heating the water.
Zono, it sounds like one of my typical home improvements. Like the sound of it.
I have alternative suggestion.
Get one of these:
(http://tbn0.google.com/images?q=tbn:6i0uV3-eM1iJvM:http://www.systemsaxis.net/images/clp/017714.jpg)
Punch holes in side and finish off with rubber to fit cricumference of your arms. Punch hole in lid likewise with rubber to seal to size of neck.
Optional: hole for feet or fit hand operated wind up to turn wheels.
Fill withh water and ice chunks.
Climb in. Adjust arms and head to comfortable and tight fit round neck.
Fully mobile and definetely green.
How high is the humidity level where you are? Most water cooled air systems are evaporative in nature. Much different from an air-over-cool metal system.
Depends on average humidity level as to whether it'll help. In Florida, you might not have such great luck.
http://www.coolmax.com.au/evaporative-cooling/evaporative-cooling-areas.htm
According to the map, it's too humid to have much success. Water-cooling is done with pads that hold the water, not a radiator. Whether the material of the radiator will provide enough surface area to cool the temps to a point that the 'ambient costs' aren't counterproductive is a good question. Radiators are designed to radiate heat, not cold, so that's an issue as well. What type of baffle system is there in order to maximize heat loss? Much like a heat pump, your ambient temp and humidity will affect the outcome.
You might do better by limiting the amount of heat gain with a reflective glass or glass application and running fans to circulate the air more efficiently. When we moved to Houston in the '60s, I started putting aluminum foil on my windows in summer. Even before we had AC, it was easier to MAINTAIN cool that create it. Open windows for high winds and cool nights, close it down before daylight or at least the hottest part of the day.
http://eartheasy.com/live_naturalcooling.htm has some info as well.
To actually help, you're going to have to devote a LOT of extra energy to the ice making, as your ice is going to melt fast. You're in a condo, right? And no deep lakes nearby...
Good luck.
Ice pits. Dig Ice Pits. Digging may be the hard work part :ROFL:
market opening: sell ice pit diggers
in fact: with the immigration rows going on over here, we can probably sell you some cheap labourer
*ahem* I'm in the A/C biz myself.
You can reduce the cost of your electrical A/C by simply shading the outside part.
Electrical A/C units work by compressing a working gas (usually Freon in home A/C), which raises it's temperature to around 120 degrees F.
Move this hot gas through a radiator. Even if it's 100 degrees F outside, that's still cooler than 120-ish. Hot freon looses it's heat, so that it's now only at ambient temp (100 in this example).
Then, the freon is allowed to expand, which thanks to physics, it's temperature drops roughly 40 degrees (around 60-ish in this example). The now cool gas passes through another radiator, and the inside air is forced over this. The freon gets hot, from the inside air, to whatever the inside temp is (roughly 78 degrees F). Rinse and repeat.
Thus, if you cool your outside unit with shade, it is more efficient-- the hot gas gets cooler, and when it expands, cooler still.
The greater the difference between one and the other, the quicker the heat goes to the colder item.
A water-source A/C uses some form of water, instead of air, to dump it's heat.
.....
Evaporative coolers. There's two basic types, the kind that Chatty mentioned and another type (will describe in a minute). The former uses the fact that when water evaporates, it requires heat. It will remove heat from the air, if needed.
In Arizona, where it's very dry (Except Phenox) these things work extremely well. But, in Florida (or Oklahoma for that matter) too much nearby water, and the relative humidity is always greater than 50%.
An evaporative cooler just increases this number, and you may get cool air, but it'll feel like a damp cave-- who cares if it's 70 degrees, if the humidity is 90%?
Not recommended.
----
The second type puts the evaporation completely outside. It's quite simple, really, and works very well.
You _can_ "roll your own" easily enough. The heat added by the pump is minimal, if you use a small pump. A car radiator would work for the inside unit, provided you had a catch-basin under it. The cooled water should hopefully get cool enough to help reduce your inside humidity, which will collect on the cool radiator. You'll either need to periodically dump the catch basin, or plumb it to the outside. The amount won't be all that much.
But for the rest. You'll need tubing, a pump, and some sort of cooling tower. Home-made ones work well enough. This must be outside. Basically, you need to get the water moving over many surfaces, so that the air will evaporate some of it. This will cool the water, which you pump back inside through the radiator. You'll need a system to check the water level, to top it up every day or so.
I've seen very small cooling towers made out of plastic trashcans, and a very small electric fan to blow the outside air over the assembly. One can is the catch basin. A smaller one, upside down, with many holes in it, over which the water flows. Fan inside the inside can, blowing through the holes. Need a chimney in the top of the inner can, to permit air to be drawn into the whole assembly. Pump mounted in the bottom of the larger can, forces cooled water though the house-loop, back outside, drains over the top of the upside down can. An outdoor pond pump works very well for this.
You can even use an ordinary toilet-tank valve assembly to automatically top-up the reservoir (the large can). Nice thing about using city water, is that it's usually chlorinated, and this keeps the alge growth low.
Here's a sketch of what I meant:
(http://i127.photobucket.com/albums/p133/BobQuantumFaith/evaporatorassembly.jpg)
My AC unit doesn't have an outside bit.
Unico range here (http://www.heatbusters.com/easifit/products/all-products).
It's ace.
But I don't know how to answer your questions in relation to it.
Quote from: Griffin NoName on April 06, 2008, 07:21:53 AM
My AC unit doesn't have an outside bit.
Unico range here (http://www.heatbusters.com/easifit/products/all-products).
It's ace.
But I don't know how to answer your questions in relation to it.
It draws air from the outside, into the unit, and then back outside. It has to, else it couldn't possibly work. :)
We have these over here, too-- my partner call'em PTAX units, after a major brand-name. Common in motels.
It's basically a glorified window unit.
Look for air-ducts somewhere or other. I've seen the air ducted to and from, under the house.
If it's mounted in a wall, it will have some outside grilles.
As for assisting it's efficiency? Basically your only option is to plant shade on that side of your house-- be careful to avoid blocking the airflow from the vents.
Big shade trees all around the house works No Matter What. If you can reduce or eliminate direct sunlight onto your house with trees, etc, you can cut your cooling bill literally in 1/2 or more.
Windows are the worst, for heat-gain. Glass acts like a "one way valve" letting heat in, but blocking infra-red (re-radiated heat waves from your furniture, walls, floors, etc) from getting back out. Think "green house". :)
If you can arrange to have your windows shaded by trees or awnings, you can cut quite a bit off your cooling bill. Shade the roof-- cut some more.
The walls are usually the least affected, but there is some heat gain from them, too (especially if your house was built prior to 1970, when energy was CHEAP..... insulation? Who needs stinkin' insulation? We gots ATOMIC 'lectricity! Pract'ly free.....)
Griffin-- you kill me!
anyway, Zono it's called a 'swamp cooler' and we never had anything but in Arizona-- of course they do add moisture to the air -- like Bob says. I like them, the ones we had were like 5 moving parts and they you just buy the pads for them and keep the water supply going (do not like my first husband decide to shut off the water supply by simply putting a crimp in the copper line running up to the roof--- water spout-- dumb boy) anyway not bad at all.
The only real drawback we ever had was that from time to time someone (ME) had to take the metal louvered doors and scrape and clean the hard water deposits off of them-- that sucked-- I am sure that there are water softeners for them now (and probably then).
But they add moisture to the air-- and you are already humid enough in Florida! so unless you can make the low humidity one, not recommended for your area.
As I remember, Zono's in a condo, so outside is probably not available, unless it's a patio home situation.
I'm all about keeping the heat out. Drapes with foam-backing in white that are drawn against the sun are an inexpensive 'help'. Duette shades, with the better ratings especially, http://www.hunterdouglas.com/hdg_product_detail.jsp?id=6
are wonderful, but expensive. Both are much more attractive than the aluminum foil...
Quote from: Bob in a quantum-state-of-faith on April 06, 2008, 06:28:35 AM
The second type puts the evaporation completely outside. It's quite simple, really, and works very well.
You _can_ "roll your own" easily enough. The heat added by the pump is minimal, if you use a small pump. A car radiator would work for the inside unit, provided you had a catch-basin under it. The cooled water should hopefully get cool enough to help reduce your inside humidity, which will collect on the cool radiator. You'll either need to periodically dump the catch basin, or plumb it to the outside. The amount won't be all that much.
But for the rest. You'll need tubing, a pump, and some sort of cooling tower. Home-made ones work well enough. This must be outside.
This sound close to what I have in mind, except for the 'outside' part:
(http://i98.photobucket.com/albums/l252/anon1mat0/WAC.jpg)
As a proof of concept, while explaining it to a relative we did a base experiment using a small fan, an empty sodacan box and a few soda cans out from the fridge, using the box as a duct and placing the cool cans inside and checking the temperature of the air before and after and there is a drop in temperature, plus a slight level of dehumidification.
Have in mind that I'm not looking to a fully automated system, so I don't care if I have to put ice in the box every 2 hours. Also my relative suggested using a portable cooler as a reservoir (which makes a lot of sense).
Quote from: Sibling Chatty on April 06, 2008, 04:38:37 PM
As I remember, Zono's in a condo, so outside is probably not available, unless it's a patio home situation.
Indeed. BTW the honeycomb shades are nice!
I have a bad feeling about the energy balances here, unless the refrigerator making the ice is outside the region being cooled. But my a/c knowledge is minimal.
Quote from: Sibling Zono (anon1mat0) on April 06, 2008, 04:57:38 PM
Have in mind that I'm not looking to a fully automated system, so I don't care if I have to put ice in the box every 2 hours. Also my relative suggested using a portable cooler as a reservoir (which makes a lot of sense).
Quote from: Sibling Chatty on April 06, 2008, 04:38:37 PM
As I remember, Zono's in a condo, so outside is probably not available, unless it's a patio home situation.
Indeed. BTW the honeycomb shades are nice!
Quote from: beagle on April 06, 2008, 07:27:59 PM
I have a bad feeling about the energy balances here, unless the refrigerator making the ice is outside the region being cooled. But my a/c knowledge is minimal.
What beagle said.
Heat has to go
somewhere.
Your system can be effective at cooling a small space, like the immediate area around a chair, or a very small room.
Using the ice from your frige, you won't be able to keep up with demand. I know, a typical frig can make about a 1/2 pound of ice every 4 hours or so (or less). Your setup would go through that much every hour, so you'd be behind pretty quickly.
Your cooler need not be huge. Do you have a patio that you could put an outside radiator of some sort in or on?
I remember another easy home-rolled system, uses compressed air. You need a small QUIET air compressor, and a radiator capable of relatively high pressures.
Pump room-air into the radiator (which is preferably either outside, or in a window, with air blowing outside with a small fan). This air needs to be at least 100 psi or more while in the radiator. You'll need a water trap of some sort, because pressurizing the air will condense out some of the water in it. Anyway, the air flows under high pressure through the radiator, where the inside room air blows over it, cooling the air to near room temperature before flowing back to your point-of-cooling.
Then, you release the high-pressure air into the space you're trying to cool. If you wish to cut the noise, a long pipe with many holes in it, and the far end capped will let the air expand over a large area. This pipe will need a water drain, too, as the expanding air will cool quite a bit, and much of the remaining humidity will condense out. Let the air blow into your small-space, or over your favorite chair/bed/etc.
A small fan can help distribute the cooled air around the space, if desired. Let the air out just behind this fan.
You'll want a filter on your compressor. You'll want a control valve in the line, that lets you regulate the air-flow (a simple ball valve works, but is finicky to adjust precisely). You'll want the out-flow to just balance the in-flow from the compressor, so as to maintain approximately 100 psi in the cooling radiator (or higher). Higher pressures means you remove that much more heat. You
have to get the air's internal temperature [in the radiator] above ambient, or it won't work. A pressure switch mounted somewhere or other, set to cycle the compressor on and off at preset pressures would make this automatic. Pump comes on at say 90psi, turns off at say 150 psi. You can add a large air-tank between compressor and the radiator to make the pump cycle less often. Put the pump, tank and radiator on your patio if you can, or mount in a window-box hanging from a window. Or you can box-in the pump with noise padding-- just allow adequate ventilation to the pump's cylinder (they are almost always air-cooled).
This system is simple, cheap to make, and can potentially run forever.
The problem areas are:
- pump/compressor noise
- water condensation in the system can rust steel materials
- dust coming into the system can clog the final pressure-drop openings (input filter is a must)
- A home-brew system will only be effective for small areas. A system to do a whole-house would need a huge compressor.
Advantages:
- can be cheap or even free, if you convert junk-pumps yourself.*
- easy to maintain. Rust and water condensate are the biggest headaches, and preventative maintenance solves this easily.
- it Just Works.
---------------
* Old automobile A/C pumps/compressors can often be had for free at auto salvage yards, or nearly so. But you have to add an electric motor, and a belt-drive.
Old refrigerator/freezer compressors work just as well, and these are almost always free at the dump. They work on mains-power already. Most old refrigerator/freezers were tossed out NOT because the compressor quit, but because they were dirty or out-of-style. Just remember to keep some oil in the compressor's casing from time-to time. If you keep the compressor low, and run the lines into and out of it from a higher elevation, the oil will stay inside the compressor's can. And when it quits, finally, just toss it back in the dump and salvage another one.
My dad used to use a swamp cooler when he had an apartment. It worked pretty well. But our humidity is usually >30%, so that's why.
Buy some of those bamboo window shades and put 'em over the windows. They are fabulous. Also, there's a type of screen that's very effective at blocking the sun. We have some on the backdoor. Keep plants near the entrances.
Quote from: Bob in a quantum-state-of-faith on April 06, 2008, 10:15:37 PM
Your system can be effective at cooling a small space, like the immediate area around a chair, or a very small room.
Which is my intention. I'm perfectly aware of the limitations, and the intention is to use it on my den during the day (when I'm home alone). In the evenings is cooler so I may be able to avoid turning the AC on until it's too hot.
Quote from: Bob in a quantum-state-of-faith on April 06, 2008, 10:15:37 PM
Heat has to go somewhere.
I guess the suggestion would be to replace the water from the reservoir with cold water if it becomes warm (as it should) otherwise I would expect the cooler (reservoir) to delay it's radiation.
Quote from: Sibling Zono (anon1mat0) on April 06, 2008, 04:57:38 PM
Quote from: Bob in a quantum-state-of-faith on April 06, 2008, 06:28:35 AM
The second type puts the evaporation completely outside. It's quite simple, really, and works very well.
You _can_ "roll your own" easily enough. The heat added by the pump is minimal, if you use a small pump. A car radiator would work for the inside unit, provided you had a catch-basin under it. The cooled water should hopefully get cool enough to help reduce your inside humidity, which will collect on the cool radiator. You'll either need to periodically dump the catch basin, or plumb it to the outside. The amount won't be all that much.
But for the rest. You'll need tubing, a pump, and some sort of cooling tower. Home-made ones work well enough. This must be outside.
This sound close to what I have in mind, except for the 'outside' part:
(http://i98.photobucket.com/albums/l252/anon1mat0/WAC.jpg)
As a proof of concept, while explaining it to a relative we did a base experiment using a small fan, an empty sodacan box and a few soda cans out from the fridge, using the box as a duct and placing the cool cans inside and checking the temperature of the air before and after and there is a drop in temperature, plus a slight level of dehumidification.
Have in mind that I'm not looking to a fully automated system, so I don't care if I have to put ice in the box every 2 hours. Also my relative suggested using a portable cooler as a reservoir (which makes a lot of sense).
Quote from: Sibling Chatty on April 06, 2008, 04:38:37 PM
As I remember, Zono's in a condo, so outside is probably not available, unless it's a patio home situation.
Indeed. BTW the honeycomb shades are nice!
I have my doubts about you being able to save money with this system. The problem is that your freezer works pretty much the same as an AC unit, except the heat it is dumping is into your house rather than outside. So the heat you have removed from the ice is just being transfered into the air inside the house, which you are then transferring back into the ice...round and round.
So to get any gain, you are going to have to put your freezer outside or in the garage...which is going to decrease its efficiency because the ambient air will be warmer.
Also, while I am not sure of the figures (it has been a long time since I took Thermo) I think you are going to have to use a LOT of ice to get much effect.
That's actually the measure commonly used to size A/C units.
For a 2400 sq foot house - 4.5 tons of Ice a day.
For a 1200 sq foot house - 2 to 3 tons of Ice a day...
This thread has got me jumping around wikipedia... I have come to the conclusion that I should take a stab at jury-rigging a misting system for the patio this summer. Even if I don't achieve flash evaporation, it'll be good for the plants.
Quote from: Aphos on April 07, 2008, 04:06:53 PM
I have my doubts about you being able to save money with this system. The problem is that your freezer works pretty much the same as an AC unit, except the heat it is dumping is into your house rather than outside. So the heat you have removed from the ice is just being transfered into the air inside the house, which you are then transferring back into the ice...round and round.
So to get any gain, you are going to have to put your freezer outside or in the garage...which is going to decrease its efficiency because the ambient air will be warmer.
Which is why it would be used in a different (and closed) room.
Quote from: The Meromorph on April 07, 2008, 04:42:23 PM
That's actually the measure commonly used to size A/C units.
For a 2400 sq foot house - 4.5 tons of Ice a day.
For a 1200 sq foot house - 2 to 3 tons of Ice a day...
Mmm... which scaling would mean that for the 100sqf room I want to cool I would need aprox 160kg of ice, although I imagine that it would mean a frosty 60F (or less) with such a system. If I can get it to 75-80F and dehumidifies the room I would be more than happy.
Again I'm not planing to replace my central AC unit, much less with the fridge!
Quote from: Agujjim on April 07, 2008, 05:00:53 PM
This thread has got me jumping around wikipedia...
:tjack: :offtopic:
It's much more fun jumping around Facebook :ROFL:
OK, the latent nerd in me is wondering about a window installed unit of Peltier junctions...could be reversed for winter as well.
Guys?
Quote from: Sibling Chatty on April 07, 2008, 07:17:18 PM
OK, the latent nerd in me is wondering about a window installed unit of Peltier junctions...could be reversed for winter as well.
Guys?
PK junctions are efficient, but they are expensive and very small.
For anything large enough to cool an entire room? You'd need a huge array-- I'd guess 6 foot by 6 foot wouldn't be too big.
They work well for spot applications, and even tiny little fridges (2 cubic feet). I don't think they'd be very viable.
On the other hand, if you can get a bunch second-hand (they tend to be quite expensive) for free or cheap, then putting huge heat sinks on them.... let's see how would you do it?
Okay, two rectangular tubes, side-by-side. One for air coming in, the other for air going out. Put a fan on each, just to be sure (they WILL fail if they overheat). Put the junctions in the common wall of the tubes, with heat-sink fins going into each tube. Test each, and ensure the heat is going to the tube-going-out. Room air out, picks up heat from heatsinks and exits the building. Outside air comes in, looses heat and goes into the building. Filters at each end.
An array big enough would consume quite a bit of juice, though. I wonder if it would be more or less than a very, very small room A/C unit?
The one I bought http://www.heatbusters.com/easifit/products/all-products/unico-star-85-heating-cooling does cool or heat..... and has no outside unit... what you get is what you see... but it wouldn't solve the cost element - or at least I suspect it wouldn't.... but maybe worth investigating how it works.
Just thinking... my gut feeling says that in the middle of a Florida summer, a dehumidifier might be more effective than an evaporative cooling device. It wouldn't reduce the actual ambient temperature, but by reducing humidity, it would improve your body's ability to evaporate heat away itself. Effectively, it should reduce the humidex/"feels like" temperature.
Another part of my gut says that a normal freon-or-similar-based system is probably going to give you the biggest cool-for-the-buck of any active system. Is it a viable option to just close the vents in the unoccupied rooms (and either switch the A/C system on & off manually, or wire in a switch to a second thermostat in the room you're in), or to get a small window air conditioner for the one room you need cooled?
I find that leaving all the windows closed except for one room on the main floor and one room upstairs creates a nice amount of breeze by natural convection... though the stack effect up the stairwell probably helps a fair bit. Are you on one level or two?
I'm on a condo on a 3rd floor.
What I have in mind should work as a dehumidifier (and it is NOT an evaporative cooler), in fact it should work better as a dehumidifier than a cooler unit in itself.
Lastly, a typical (small) AC window unit uses 125V*15A=1850Watts. My main AC unit uses from 4KW to 5KW. For comparison the tower fan I have besides me uses 42W, double that for a ceiling fan at high speed (~80-100W). If my power usage is 200W I would be using 9 times less electricity than a window unit and 25 times less than my main unit.
Again, why cool the whole house when I spend most of the time in one room? And I don't need it to be chilled, just enough to be bearable.
The one caveat I can think of is that you won't actually be using 'already spent' energy to make the ice. Placing 'warm' materials (such as liquid water) into the freezer will make the freezer run harder (if not, it'd raise the temperature of everything else in order to cool the water).
Still might be a net reduction in energy, but you'd need to hook some kind of a power meter up to the freezer to check how the usage changes when you are making ice.
(I've wondered if it might be efficient to run this sort of air-conditioning using good ol' winter-frozen ice, stored in an underground cistern or an ice shed bored into a hillside. Mero's numbers seem to indicate otherwise - up here it's probably better to simply send the cooling circuit into the ground where it stays close to 4o Celcius)
Quote from: Agujjim on April 07, 2008, 09:52:09 PM
The one caveat I can think of is that you won't actually be using 'already spent' energy to make the ice. Placing 'warm' materials (such as liquid water) into the freezer will make the freezer run harder (if not, it'd raise the temperature of everything else in order to cool the water).
Still might be a net reduction in energy, but you'd need to hook some kind of a power meter up to the freezer to check how the usage changes when you are making ice.
I imagine there will be a hike in energy use from the fridge but not a very significant one. A typical fridge uses ~400W, a 100W hike would still be on target.
Quote from: Agujjim on April 07, 2008, 09:52:09 PM
(I've wondered if it might be efficient to run this sort of air-conditioning using good ol' winter-frozen ice, stored in an underground cistern or an ice shed bored into a hillside. Mero's numbers seem to indicate otherwise - up here it's probably better to simply send the cooling circuit into the ground where it stays close to 4o Celcius)
If I lived in a house with permafrost under it... ;) :mrgreen:
Quote from: Sibling Zono (anon1mat0) on April 07, 2008, 10:08:18 PM
I imagine there will be a hike in energy use from the fridge but not a very significant one. A typical fridge uses ~400W, a 100W hike would still be on target.
You could probably run a quick calculation based on the mass of water you think you'll need and the temperature drop necessary. The energy used for cooling still has to come from somewhere, but for the small space you need to cool it may be just fine.
Given that you will be able to get quicker freeze times out of containers with high surface areas, you could build an ultra-low tech system simply by placing a number of cold packs (ziplock bags filled with water, then frozen while laying flat on baking sheets work too) on a wire rack or shelf and blowing a fan past them. No need for a pump or radiator.
In the '50s before we had AC, my grandfather used rubber tubing tied off at the ends, filled with water and then frozen overnight to drape around his neck (and mine) when we worked at the cooperage. Old wooden building with a tin roof--if there was no breeze, 110 wasn't unheard of on a summer afternoon.
He actually used inner tubes from bicycle tires, cut in half and heat sealed on one end, tied on the other. He'd break up the ice so it would wrap, and with the fans on, it was tolerable.
I used to use my cold packs from the chiropractor's office for cooling down when my tumor burden was high. (Carcinoid causes a sensation of burning up from the inside out...among the less disgusting but more irritating side effects.) That gooshy gel stuff in a refreezable pad kinda thing....
Quote from: Agujjim on April 07, 2008, 10:26:16 PM
Given that you will be able to get quicker freeze times out of containers with high surface areas, you could build an ultra-low tech system simply by placing a number of cold packs (ziplock bags filled with water, then frozen while laying flat on baking sheets work too) on a wire rack or shelf and blowing a fan past them. No need for a pump or radiator.
Actually that is a wonderful idea! I can make the duct out of plywood to work as a rack for the trays at the same time. The condensed water would fall in the trays themselves and it would be relatively easy to check how long takes the ice to melt in the duct, and to freeze in the fridge.
Thx! :woot: :thankyou:
You're welcome!
I like projects.
Quote from: Griffin NoName on April 07, 2008, 08:34:16 PM
The one I bought http://www.heatbusters.com/easifit/products/all-products/unico-star-85-heating-cooling does cool or heat..... and has no outside unit... what you get is what you see... but it wouldn't solve the cost element - or at least I suspect it wouldn't.... but maybe worth investigating how it works.
From the description:
QuoteAn elegant, self contained unit simply requiring two vents through an external wall,
The unit sucks air into the inside box with one vent, blows that across the condenser radiator and the now-hot air exits out the other vent.
It does provide a very clean look on the outside.
And, you can put these in temp, with an adapter plate in a window-- that is, the window shuts onto the plate, which has two holes for the two vents.
If you live on the first floor, and the unit is to be on an interior wall, you can vent under the house to the outside (assuming you're not on a slab).
I would imagine these are about as efficient as a quality window unit.
The size is everything, obviously, and too big is worse by far (for a number of reasons) than too small.
Why? Because, too big will get the temperature down quickly.... too quickly, and leave in all that nasty humidity. It's like being in a damp cave....
_______________________
Quote from: Sibling Lambicus the Toluous on April 07, 2008, 08:56:59 PM
Just thinking... my gut feeling says that in the middle of a Florida summer, a dehumidifier might be more effective than an evaporative cooling device. It wouldn't reduce the actual ambient temperature, but by reducing humidity, it would improve your body's ability to evaporate heat away itself. Effectively, it should reduce the humidex/"feels like" temperature.
Another part of my gut says that a normal freon-or-similar-based system is probably going to give you the biggest cool-for-the-buck of any active system. Is it a viable option to just close the vents in the unoccupied rooms (and either switch the A/C system on & off manually, or wire in a switch to a second thermostat in the room you're in), or to get a small window air conditioner for the one room you need cooled?
You DO NOT want to close off too many rooms-- if you have central. Your A/C unit DEPENDS on a certain load-- if you close off too many vents, it will freeze up and possibly ruin the compressor. Not good.
If you just want a room or three cooled, and the rest ambient, then 2 or 3 window units is the way to go, if you've a medium-large house.
If you've a small one, the break-even point is at about 1 window unit, vs the whole house one.
Commercial de-humidifiers are basically a small window A/C unit. They work pretty well, but unless plumbed, you have to empty them daily.
Quote from: Bob in a quantum-state-of-faith on April 08, 2008, 07:31:20 AM
It does provide a very clean look on the outside.
It does indeed.
And mine seems effective. The few times I used it last summer.
*thread resurrection*
As it's starting to warm up here, I'm mulling over what would be the best way to help keep this place cool in the summer.
(number one will be to get some curtains on the place, and perhaps some awnings over the south windows, but let's ignore that bit)
My bedroom in particular could probably benefit from some sort of jury-rigged system. I'm in a small house built circa 1946, with removable storm windows on the outside of the (original) interior windows. The bedroom window is east-facing, and gets morning sunlight. Since I like it dark, I've mounted fibreboard and a mirror on the interior of the storm window. The house is in a slightly dodgy part of town, and aside from the effectiveness of the exterior-mounted 'curtain', I'm disinclined to remove the storm window in order to catch the night breezes. There are, however, two ~3 cm diameter holes in the bottom portion of the frame of the storm window which will admit some air.
At the moment, those little holes do a fine job of admitting some cool night air, but during the summer it gets seriously hot (>40oC during the day, and sometimes can remain above 30oC at night). The advantage relative to Zono's issue is that we are semi-desert in the summer and it's also very, very dry.
So, given that I have dry air and that the side of the house I'm on doesn't get sun except in the coolest part of the day, I'm wondering if I can concoct a little evaporative cooling system here.
Now, I still don't want the added humidity, so what I'm speculating about is a system that cools a set of coils through which air from the room to be cooled is passed. Some sort of little tube or duct fan would be required to move air through the coils. With the two holes in the window frame, I could pass the tubing in and out without any modifications.
The coils themselves could be cooled in a couple of ways; one would be to be sew a tight-fitting terry-cloth cover out of an old towel to fit the stacked coil, and then use a small pond pump to circulate water over the cover. Similar to Bob's cooling tower design in principle, but the towel has much more surface area for evaporation, and would also slow the passage of water to allow greater cooling.
What might also work is to place the coil inside a terracotta pot (a large planter with the bottom hole plugged off would do) full of water, which would function similar to a pot-in-pot refrigerator (http://en.wikipedia.org/wiki/Pot-in-pot_refrigerator). Essentially, this would be a water-to-air heat exchanger running through a large thermal mass of water, which itself is being cooled by evaporation (plus, cools down every night). It may even work better in full sun, if the pot was fairly light in colour (perhaps whitewashed). The evaporation would occur entirely outside of the building, so there'd be no additional humidity to the air. There's some potential for condensation to occur within the coils, but it wouldn't be hard to build a trap that could be drained out from the bottom of the coils (remember the hole in that pot? put it out through there). A coil of copper tubing would be ideal as it would conduct heat well, but I've got a bunch of scrap 5/8" polyethylene tube kicking about. The stuff is (IIRC) about $30 for 100 ft, so it would be more economical to use a longer tube of cheaper material than a short copper coil, perhaps.
EDIT: I took a peek and found some 1" HDPE tubing at ~$60/100 ft; smaller diameters will make better heat exchangers, but larger diameters will be easier to push air through. Am I correct in thinking that since air friction and energy transfer are proportional to surface area, it might not make much of a difference either way in terms of efficiency?
With a large, porous container, you could even stick this near a down-spout and have a combination air-conditioner/rain-barrel (hmm. should patent that, perhaps). Worst case, you'd have to top it up with water every morning - no big deal. I'd move the air through the coil from top to bottom, which should be counter-current to the temperature gradient and would make it no big deal if the pot wasn't totally full to the top of the coil. If a terry-cloth jacket was used on the coil, having the water level low might actually help with the cooling. It could even be used as an intentional pre-stage; if the towel protrudes down into the water, it'll wick up enough moisture to stay wet.
Now, the biggest issue I can see with this is how to move the air through the tube. The best thing I can see at the moment is perhaps electric ducted fan units used for RC aircraft, like this:
(http://images.nitrosell.com/product_images/9/2065/GWSEDF50-450.jpg)
They don't make these things quite as small as I'd need, but they are cheap-cheap (under $20). I imagine the system might be a little noisy, but probably no worse than a compressor (unless it whistled). Now, these suckers are meant to produce thrust, so I imagine they would be capable of compressing the air a bit. If you mounted the fan outside the house, just before the cooling coil, then put a condenser to drop the diameter from whatever fit the fan to whatever diameter you were using for the coil, there would be a (slight?) increase in air temperature at that point. However, this heat would be removed as the air passed through the coil, and there would be an equal (slight) drop in temperature as the air was decompressed from the coil into the room. Bonus!
I'm not sure what the power consumption is, but since they're for battery-powered aircraft, you might be able to run one with a small, cheap hobby-size solar panel. If so, it's possible that you could plunk the entire unit outside of a small room and run it entirely by the sun, which would be adequate for taking the edge off the hottest part of the day. I imagine you wouldn't move enough air to get things really cold, but from what I've heard about the pot-in-pot refrigerators (some designs can generate temperatures as low as 6C), it's not impossible that this could be effective as a small-scale cooling system.
Hmmm... any glaring errors in all that?
You might want to look at computer cooling fans (cheap, readily available, fairly high volume, designed for long continuous running) instead of expensive, ultra- lightweight model aircraft fans... :)
This was my first thought (simply to put a small computer fan against the holes in the window), but would a computer fan be appropriate for driving air through 100 feet of small-diameter tubing? I.e, can they work continuously with a significant load? ???
For the price, they'd certainly be worth a try. It'd be easier to build a square duct for the fan-box than to size tubing for the little RC ducted fans.
If you use small diameter tubing? (not a bad idea, actually)
You are going to need multiple paths to get any worthwhile airflow. 8 or 10 is not out of the question here-- or more.
The easiest way to push air through multiple tubes at the same time, is to plumb them all into a single box-- make it airtight. Now cut a hole in the opposite end of the box from where the tubes all come in-- mount a fan there. Or possibly two holes and two fans.
The fans will pressurize the box, with will then force the air through the multiple tubes. Coming out the other end? You could split them up to dump the cooler output air anywhere you like-- but keep in mind, a small diameter tube won't have much volume coming out, even if at relatively high velocity.
Such a setup might work for a single room, which was your goal, right?
Another thing you'll want to do: on the return-path for your tubes, after the air's been cooled? Insulation. A goodly bit, too-- once it's cooled down, but still outside? I'll pick up heat quickly, if you don't insulate those tubes. The tubes going from inside to the barrel ought to be insulated too-- no point in adding needless heat to your barrel, as once the system is up and running, the inside will be cooler than the outside air temp, so any point you can prevent unneeded heat is a must.
Finally? Heat rises, cool air falls: place your box-with-fans-and-tubes up high in the room-- near the ceiling. (on the inside, there's no need to insulate your tubes-- the air will be nearly the same temp at that point).
Now-- were to put your output, cooler air-tubes? High or low? Both have advantages. But your goal is to mix-up the total air in the room. So, since these are cheap, and small? (and once back inside, no need to insulate once again) I'd either string them across the ceiling to the opposite wall from the intake, exiting high (or at the ceiling), or dump them near the floor, if on the same wall as the intake box.
The opposite wall has the nice effect of forcing a circular motion in the room: the cool air will naturally fall down, causing warmer air to rise up to be collected by the intake box.
But the same wall-but low-down, would work nearly as well, as it'd blow across the room, letting the warming air rise up to the ceiling, where it'd be drawn in by the intake fans.
Of course-- you could just dump the air anywhere, and intake nearby, and then use an ordinary room fan (or fans) to mix-up the air to a relatively constant temperature. That would work too, and mean less tubing all over.
------------------
As for your clay pot? You're going to need one that is large. Really, really large-- I'm talking 30 gallon size or so here. The surface area of evaporation has to be big, since you are depending on a purely passive system, on the evaporation side of things-- i.e the wind, etc, to move the outside air past your pot. Normal evaporation will create modest air currents, but not nearly as much as you need, here.
Now you could opt for a ridiculously large pot to get the needed surface area... or... you could go multiple, small pots-- say one pot for each of your 10 tubes? Then a system of cisterns to deliver (and top-up) your rainwater to each? The nice thing about piping the air in insulated tubes, is that you can put your pots low to the ground, and have your cistern (say a used 55 gallon barrel? Up on blocks? ) higher than your pots, and let gravity deliver the water. A simple float-valve (like you'd find in a toilet water tank) will admit enough water to keep the pot full. Coil the tube inside the pot, and then back out-- no insulation while in the pot, obviously.
You'd still want larger (than smaller) pots, though, for the thermal mass of more water in the system, since you are also depending on nighttime cool-down.
-------------------
Have you considered a simpler option? Move water instead of air? Inside your house, set up a used radiator (a junkyard find) from a car, with a normal air-fan blowing across it into the room. You'll want this sitting in a trough, say those nice things that wallpaper people use to get pre-pasted wallpaper wet would work-- for it's apt to get cool enough to gather moisture, some. Since you're dry, not enough to really worry, but enough you don't want it just sitting there.
Okay-- from the radiator, you plumb water, driven by a pump of some kind-- a simple pond-pump outside in your cooling pot would do (and gets the noise outside, it does). Plumb your water lines to the inlet & outlets of the radiator-- likely you'll need to cobble up reducers, as the radiator's openings will be rather large, but your system will be using rather smallish tubes. Again, insulate the lines-- why add needless heat?
Now it gets simple: dump the "hot" water into the top of your pot, through the terry-cloth cover. And draw the coolest water from the bottom of the pot(s), via the pump sitting on the bottom(s). Again, you'll need a system of make-up water from a cistern. I would insulate the cistern well, to avoid daytime heat-pickup. Since you're using rainwater, it'll already be clean, so no mineral build-up, and the rain will come down as "cold", why add unwanted heat?
But you're just cooling the water, not the air this way-- and cooling it directly, too. If your location is dry enough? You ought to be able to get the water cool enough to be effective.
And here's a thought: you could make a fountain somewhere with this water.... the fountain will spray up into the air, really cooling the water (but evaporating it faster, too).
:)
I don't like the idea of moving water for my particular application for a couple of reasons:
1. Water. Potentially water, water everywhere if something goes haywire, but also the condensation on the radiator inside the room.
2. Energy use. Instead of a single blower fan, I now have to run a water pump plus an indoor fan. That fan inside is going to be noisy for sleeping (the small fan driving the tubes may be worse, but perhaps not so bad after passing through the tubing, plus the unit'll be outdoors). As for moving water... that stuff's HEAVY! No chance of avoiding a plug-in.
3. Indoor real-estate. I've got a small room, and there's no practical place to put the radiator. With the air unit, I'd only have the hoses coming in. Since I'm effectively trying to spot-cool the bed, which is adjacent to the window (vent holes are near my torso - perfect), I'm not even that concerned about running the hoses beyond the window. Perhaps I'd put the intake hose up to the ceiling, but I could stick to 1" diameter tubing for that and do any manifolding downstream of the fan-box (which I'll need anyways). For night-time comfort (my only goal here - I love the heat in the day), only the bottom 4 ft or so of the room needs to be cooled, and hot air trapped near the ceiling is a non-issue. There are small, easily removable basement windows adjacent to where I'd be doing the install, so I could even source the air from the basement or get really fancy and put a coroplast air-to-air precooler down there.
(of course, the lowest-tech version would be just to bury my cooling 'coil' in a long, deep trench underground. I've got a glazed-pottery pot of kimchi using traditional ground-based refrigeration on the north side of the house. Hmm.. that could benefit from a damp cloth cap once it starts warming up).
I'm not convinced that multiple small tubes is going to be better than one large-ish one (1" diameter), provided a longer length of the large-diameter stuff was used. The key factor for cooling is going to be surface area, but that's also going to determine the amount of friction limiting the airflow. Sure, if I had a air-water exchange tapped into a small but well-chilled water cooler or the like, it'd make sense to do multiple small tubes, but since I need a very large pot (I'm thinking about stacking and sealing two planters in the 36 - 48" range, with the top one inverted, or just finding an alternate construction material* to build a box with the same properties). I'll have the capacity to use a very long coil... 100 ft would not be an issue. The coil would sit towards the outside of the cavity in the cooler, which would place it close to the evaporating surface. Plus, with the need for a condensation trap, it'd be wise to stick to a single tube. I concur on the size - I was picturing something similar to a barrel (55 gal).
Now, if you want to take the multiple-paths evaporative cooler to an extreme, the best way to do this would be to construct a panel cooler using a sheet of coroplast, and cover it with terrycloth (get some cheap beach towels). You'd need to rig a manifold for either end of the coroplast (not too difficult, I think) and would still need a fountain-pump plus a little drip manifold and catch tray to keep the terrycloth wet, but that sucker would cool air like crazy. You could set up as many of these panels as you needed in a parallel configuration at one end of a porch lllllll , blow a fan through the fins to give you cool (damp) air on the porch plus boost evaporation rates, and pass air through the coroplast to give you cool, dry air indoors. In a dry climate, this should work quite well and still be heaps cheaper than phase-change cooling. If they were mounted vertically, any condensation inside the panels could be collected and trapped in the bottom manifold.
Here's one more spin on this idea... get some soaker hose - the kind designed to work at low pressures - and inside this hose insert a smaller-diameter polyethylene tubing to carry your airflow. You'll need to do some jury-rigging to make sure you can still get the soaker hooked up to a tap (some y-joints and a little sealant should do the trick). Now, either hook it up to a water supply using a pressure regulator, or simply have a gravity-fed reservoir to create enough flow to keep the surface of the soaker hose moist (the reservoir could be a self-cooling terracotta pot). Gravity-fed will probably be better - you'd want less than 10 psi, probably much less, to keep the hose from actively weeping. This could be either set up as a freestanding coil or wound into a panel. Black soaker hose would probably work in a shady spot, but hypothetically, a light-coloured hose could be used in full sunlight, with the caveat that most light-coloured plastics aren't UV-stable.
*hey, how about unglazed clay tiles as an outer 'skin' for the cooler? You could up the surface area considerably by building a box that was wide and tall but thin - say, four units W & H by one unit deep. There is likely an equilibrium point between what's going to heat up fast due to ambient temperature and what's going to cool down faster by evaporation, but if this idea works in the first place, presumably more surface area is a good thing. A triangular prism, set on end, might be a good choice, too.
Are cinder blocks water-tight?
Question, is this for the land you were planning to buy, or in a place where you can do stuff in the roof/garden? I was looking a bit and it turns out that wind turbines are starting to go down in price enough to be economical mid term, for instance this:
http://homegardenoutdoors.com/product/26539_Home-Wind-Turbine-2kw-48V-wind-generator-for-home-use.html
is capable of generating up to 2KW and costs about ~U$1700. That should be able to power a small AC window unit and you should recover your investment in about two years.
The other thing was discussed before, can you bury the pot/tank? IIRC once underground the water temp would remain at a low temperature and depending on the size of the tank you should be able to pump water in/out without much trouble.
The last thing that popped into my mind was measuring wind speed in the shadowed part of the house, possibly near to the roof wind speeds may be higher and you may be able to duct that cooler air inside (while pumping out hot air from the roof).
This is for the house I'm in (rental), on a small lot. I've got more-or-less free range to do anything that doesn't require putting big holes in house (holes in the ground are OK).
I'm mostly trying to cool my bedroom, but my roommate lives in the 'attic' (finished loft under the roof) and could use a way to cool her space too. I'm not interested in major investments for this place, at this point, and we aren't seriously considering putting in a real AC unit. We are both lizards who love the heat*, but I prefer a cool room to sleep in.
*first priority will be some screens to replace the storm windows; there's a few here but not enough
Digging a hole to sink a small cistern is possible, but as stated before, it'd be easier to just directly cool the air line in the ground. A pot of water in the ground will give some heat up to the earth, but I suspect the cooling effect may be somewhat limited (short of using a metal container with fins to conduct faster). Evaporative cooling should do better in responding to the hottest days, and the bonus will be the nightly chill-down. I've some ideas on how to augment the night-time cooling by radiating heat to space, but that's beyond what I'm trying to achieve at the moment.
Clay pots are fantastic coolers, if the volume-to-surface is right. A tall, skinny pot for example, would expose a lot of "skin" to the evaporative air compared to the volume of water.
On the other hand, anything in the shade would work well enough, as you don't want direct sunlight heating up the water anyway.
100 feet of pipe buried 3 feet deep would work quite well, with air or water (running through the pipe). If you can get below the ground-water table? Fantastic... but even if not, it ought to work well.
I would pour sand around your pipe, then re-bury it. The sand will let the pipe move a bit, and I think will work better than plain dirt.
Ah, but unless you're below the water table, the sand will reduce contact and transmission of heat. Better to put it in with a clay slurry, I would imagine. Clay's HEAVY and would have a lot of thermal mass, even in the immediate vicinity of the pipe.
Also, at the depth I'm interested in, it's all clay. ;) Groundwater appears to be deeper, from the few holes I've dug.
I am more interested in the evaporative model at the moment, due to portability. This could be used in some otherwise unlikely places such as vehicles and RVs.
I haven't been able to get a straight answer on whether the process is more effective in direct sunlight or in the shade. I think it would depend strongly on the wetting rate of the outer surface... if you could keep a constant film of moisture on the outside of the vessel, I think the cooling from the increased evaporation might outweigh the amount of incoming infrared. I think the key here would be a light-coloured surface; either a white terrycloth or a whitewashed clay surface. If it was dark, the intercepted visible light will cause direct heating. The actual goal of the process is to evaporate as much water as possible over the course of the day, without having any just leak down and drip. You also don't want the outer surface of the pot to be too cold... if it's cold enough to cause condensation, you're now heating instead of cooling. There will be an equilibrium point based on humidity, I suspect.
I need to get some waterproof temperature loggers (these have been on my wishlist for a while), and a bunch of bench-scale (12") flower pots to test out various configurations. A heavy felt gasket between the two pots might be ideal, rather than sealing them off completely; there's no harm and probably some advantage in allowing a little extra wicking of water, provided it didn't cause bulk flow. If the clay itself wasn't working fast enough, a fabric cover could also be connected to the inner reservoir with a few wicks (the same way that a towel left draped over the edge of the tub can effectively transfer water from tub to floor. If using this kind of a cover, the clay pots wouldn't be strictly necessary; a fabric-coated metal barrel or even a galvanized steel trashcan would probably work great. Aluminum would be ideal to prevent rusting, of course. The covers would tend to get a bit funky over time, but they'd also be machine washable.
Hmm... an old flannelette sheet might be ideal here. Terrycloth would be good in terms of surface area, but would likely wick too much water and create pooling at the base of the tub.
I can get some food-grade plastic barrels for pretty cheap, but I'm not sure how well this stuff conducts heat compared to pottery or metal.
Shade. Definitely, definitely shade.
In the sun? Your pot's static temperature will quickly rise to well over the ambient air temperature, due to infra-red radiation absorption. This won't affect the water's evaporation rate much, if at all-- it's only a few percent with respect to the latent heat of evaporation after all.
But a 10 degree rise in temp of your air is quite noticeable.
However, the evaporative rate of your water is more affected by the relative humidity, than a few degrees one way or another of temperature.
Fortunately, humidity is like water-- it will quickly "float" to the driest spots from a higher location.
So put that pot in the shade!
I concur, and for the installation I'm planning, that's where it will be for any hot part of the day. There just seems to be a lot of anecdotal evidence suggesting that these sort of systems cool things down 'in the sun'.
Now, in a system using cloth-covered coroplast panel with very little thermal mass and a high enough surface area to make wind a significant factor, do you think it'd matter? I might try this for cooling the loft, by placing it outside of one of the windows. It could be mounted to the north, south or west. West would allow for rooftop mounting, but north has a roof over top of the front stoop that'd also likely work.
I'm assuming a "coroplast panel" is one of those plastic things that are like corrugated cardboard, only made of LDPE?
I've often thought of using a black one as a solar water heater engine-- plumbing it into my domestic hot water tank, with a thermostat testing the water coming out of the heater-- if it's hotter than the tank? The electric pump is on. If it's cooler? Shut down the pump. I would have to use a heat-exchanger loop, as I don't think the panel can withstand domestic water pressure, alas. And that's really the only thing keeping me from doing this project-- I routinely get black ones from major A/C installs (they use them to cover the fins during shipment). I just cannot think of a suitable heat-exchanger that would also be cheap.
One possible suggestion, is tube-within-a-tube, in a giant coil, and the whole thing immersed in some form of insulation-- spray foam? That is a smallish, say 1/4" tube for the low pressure hot water from the roof, inside a 3/4" higher pressure tube from the hot water tank itself. The beauty of that, is that the loop could be laid flat, below the tank itself, and let simple convection carry the hotter water up into the tank (by way of the boiler drain port). The return, cooler water would come out the top, via a T installed at the top of the tank. Convection would circulate the hotter water from the tube, into the tank. Insulation keeps the whole thing hot.
The roof-loop could even be filled with antifreeze (non-toxic) so I wouldn't have to shut it down in the winter, at night. I'd want to keep the panel pretty flat, to avoid high pressures at the bottom end. The only thing I cannot solve, is how to make a manifold between the copper tubing and the plastic corrugated sheeting: being made of polyethylene, nothing really sticks to it all that well, and I don't want leaks to have to make up-- I was going for a sealed heat-loop.
Sorry about the thread-jack....!
:D
You are correct on coroplast. :) Look around the 'net... I've seen homebrew designs on heat-exchangers made with it.
I've been thinking about that again-- what I need, is a waterproof adhesive that is heat-resistant, but remains tacky-- similar to asphalt, only some that doesn't melt with heat.
I'm thinking of some sort of polyurethane, some that does not get brittle-hard, but sets up as pliable (and somewhat tacky).
For a manifold, I was thinking of using a heat-resistant plastic tube, which I will slit down it's length using a table-saw & a jig. CPVC ought to do the trick. If I can make the slit small enough, the tube ought to "clamp" slightly onto the plastic sheet. Then plug one end with silicone (or urethane) glue, and fit up the other end to my supply/return tubing.
However, I suspect that if I rough up the plastic sheet with course sandpaper, and use simple silicone RTV, it ought to hold well enough for the low-pressure application I want.
I like your idea of covering it with terry-cloth (or similar) and allowing cooling/evaporative water to trickle down the outside-- catch it in an overflow basin (I'm thinking of a home-made trough made of 2" or 3" plastic sewer pipe, cut in half--or even just a strip cut out of the top to receive the panel & it's lower manifold. A very small pump at one end would recirculate the water back to the top. A trough made of plastic pipe with holes drilled along it's length would let the water drip out all along the width of the panel, soaking down through the terry cloth. You'd need some sort of wire across the terry, to hold it down in the wind-- perhaps some coated chicken-wire fencing? They sell fencing that is powder-coated (and vinyl coated too) that ought to resist the constant soaking it would get. A wooden frame to hold the "sandwich" together along either side. A side-channel of plastic pipe (slit to fit over the panel) would keep the water from rolling off either edge. Or simply fold the panel up a bit--holding the fold with the wooden frame.
I see no reason why this would not work-- again, I'd put it in the shade, if cooling is what you want, here. And a white panel would be better than a black one, I'd wager, for cooling.
If the panel can withstand the pressure of being vertical? (and you could help, by cutting it down to say 4 feet tall or even 3 feet-- cutting your head pressure at the bottom) I see no reason why you could not put terry cloth on both sides of the panel, sticking it perpendicular to the building's side, like a flag. I'd hang it from a sturdy arm, braced out from the building's side. Let water trickle down both sides, spread out by the terry cloth. Then inside the panel itself, plumbed with manifolds top & bottom, you'd run either air directly from the room, or water going to a water-to-air heat exchanger inside the house.
One of the nicer advantages of just using air inside the panel? No worries about head pressure! Simply use slightly pressurized air flowing down the panel.... I'm thinking of a positive-pressure air pump in this case, or a fan strong enough to raise the pressure to 5 or 10 psi (silicone glue ought to be able to handle that, no problems). This would increase your airflow tremendously. Then, simply dump the output from the collection manifold directly into the room-- it ought to be pretty cool, if you've cooled both sides of your panel.
I would mount the air pump outside, in a weatherized box, to get the noise away from the living quarters. For the intake, I'd use filters too-- to keep dust and debris from clogging your panel's tiny passageways.
Since it'd be suction at that point, you're going to want a larger diameter intake than your exit pipe, to increase your efficiency, and to avoid a "sucking" sound. At least 2 to 1, here: if your output is 1"? Your intake(s) ought to be 2" or more.
This is kinda fun to speculate about, but I may just fab up a small panel to see how effective it could be. I much prefer piping water through the panel, then a water-to-air heat exchanger with a very quiet fan blowing the room's air past a used car radiator. Several advantages to that: you are moving the room's air mechanically, rather than trusting to convection. You can use an oversized radiator, to greatly increase the efficiency. If condensation becomes an issue, it's easy to make a collection trough at the bottom of the radiator-- and since it's from a car? It's already weatherized, and the water won't hurt it at all. If you mount this near a window, you can plumb your condensation directly outside, and let it dump onto the ground-- it's pretty much distilled water+dust from the room here, no worries. If you insulate the water pipes, there's no worry about condensation dripping from them, either.
I'd use an open system-- i.e. one that's not pressurized or sealed, but is open to the atmosphere. To get that, you plumb the bottom, collection manifold larger than needed, and vent it to the atmosphere. That's where you install the aquarium pump, and add a make-up line, if you like. (but if the vent is tiny, you would not lose much to evaporation at all, so manual top-up would probably work well.)
I'm thinking out to the side, for the cold water-loop pump, let the collection manifold dump into that box via gravity. So the loop goes from the collection/pump box (which is at the coldest point, and needs insulating), to the bottom of the radiator, up through and out the top opening to the top of the panel-manifold, where it trickles through the multiple channels and is cooled, to be collected by the bottom manifold and dumped back into the pump-box.
This puts the coldest water at the bottom of the indoor radiator, where if there's any condensation, it will happen here, and drip down into the collection trough, to drain into either a (closed) bucket, or outside. I would blow the forced-air fan only across the top 3/4 of the radiator, letting the bottom 1/4 be convection air (where any condensation will happen). This way you don't blow air past the wet part of the radiator, possibly blowing droplets into the room.
For an air manifold, I would probably just use Tuck tape. I concur with using a slit plastic tube to 'clamp' the tubes. In the context of an air-based unit, you could eliminate an intake manifold and just let the coroplast be the intake: Using long fins of coroplast, it'd be possible to clamp a stack of them at the tube end, and then insert dowelling or a wedge-shaped strip of wood a few inches up from that to create a fanned-out set of panels \|/ to keep the whole thing compact. Set in a breezy location, this should work well enough.
I'm currently speculating on what the wicking height of various fabrics (cotton terry, cotton flannel, any other cheap and 'fuzzy' materials) is; I may have to just run some physical tests. It might be quite reasonable to set up the cloth-covered panels without a trickle-pump, and just use the capillary action of the fabric to do the lifting. Even if it limited your panel height to 1 m or so, it would keep the project even more low-tech. All you'd need to do is sit the bottom of the panel, including manifold if necessary, into a vessel of water. With the radiator system, you could even return your condensation drip tray to that same tub to recycle the water. :)
Oh, based on a little browsing, I suspect what I'm aiming for in cooling my room is the equivalent of a small 5000 BTU/h unit, which translates to about 2.1 L/h of net evaporation. I certainly will not get the efficiency I need for that to be the actual number, since the unit will also cool the air surrounding it, and most of the cooling power is needed to chill the water in the pot and balance heat gain from the ambient air temperature.
I'm still unsure of how much of a factor ambient air temp is, as it's the heat from the air, combined with the lack of humidity, that causes the evaporation. If the entire surface is working as an evaporator, then it seems that the pot should not actually gain any heat from the surrounding environment; the surface of the pot will be the coldest point on the entire setup.
I have no clue of how to calculate the actual required evaporation rate, and in any case will have to tweak that number by experimenting with covers and wicks.
Fiber cloth as used in filter media might be a good choice for wicking material-- it has the advantage of being polyester (or nylon) and therefore not subject to bacterial attack (unlike cotton).
Which ever you use, be prepared to change it fairly often, as mildew and/or mold may be a problem eventually.
How about old T-shirt material?
:)
We don't have "tuck tape" here in the US, but I know what it is from watching DIY tv shows from Canada and other locales other that here. That's a good choice for an ad-hoc rig, which is what you have there.
Let us know the results of your experiments-- it's a fascinating project, to me.
Ever used poly for exercise wear? The stuff isn't subject to bacterial attack, but it hosts them something fierce. Cellulose based material suffer more from fungi than bacteria (mildew, etc) and are less prone to UV damage.
I'd love to use wool/felt as it's microbe resistant, but it's cost-prohibitive and some of the other properties might not be ideal.
PET-based fleece (yes, old soda bottles) is cheap and readily available, but is hydrophobic and unlikely to wick well (it's also too insulating when wet). Cotton does seem the best choice; for a single coroplast panel open at one end and with a manifold-to-pipe at the other, a t-shirt would be ideal. Cut the panel to size, base the manifold on an old plastic clothes hanger, and pull on the shirt! :D
I'll need to get my hands on some fabric samples and jimmy up a wicking-height test station. I can start with towels; the piles of the terrycloth will assist greatly in the evaporation rate I suspect; hopefully the microclimate created at the surface will allow the cloth that's touching the cooling panel/pot to shed heat effectively.
PS - no Tuck tape? Srsly? For non-load-bearing applications, it's far superior to even the venerable duct tape, IMHO. Black-market export opportunity? ;)
Quote from: Aggie on May 02, 2012, 07:34:49 PM
PS - no Tuck tape? Srsly? For non-load-bearing applications, it's far superior to even the venerable duct tape, IMHO. Black-market export opportunity? ;)
http://www.amazon.com/gp/product/B004HE1B4O/ref=olp_product_details?ie=UTF8&me=&seller=
Direct Replacement. Some Canadians apparently use it in preference, as it is slightly thicker and uses stronger glue.
That's the stuff I've seen on TV, but never seen in reality.
:)
Quote from: The Meromorph on May 02, 2012, 08:16:41 PM
Quote from: Aggie on May 02, 2012, 07:34:49 PM
PS - no Tuck tape? Srsly? For non-load-bearing applications, it's far superior to even the venerable duct tape, IMHO. Black-market export opportunity? ;)
http://www.amazon.com/gp/product/B004HE1B4O/ref=olp_product_details?ie=UTF8&me=&seller=
Direct Replacement. Some Canadians apparently use it in preference, as it is slightly thicker and uses stronger glue.
This, I will believe. The original is a little thin. I do like the fact that the glue is very adhesive but 'weak' enough to break cleanly off many surfaces.