Bayou cooled (open loop) water source air conditioning?
Hey guys, I've been very interested in water source/ ground source cooling (not much heating needed down here, but it would be nice) for quite a while and A/C hacker has had me highly interested for years.
That said the relatively high labor barrier (time) of digging up a yard to bury a loop field has kept me out of the game. However, my camp is located on a small bayou Bayou - Wikipedia, the free encyclopedia that always flows a little, but often a bit and during large rain events a lot, never ever freezes, feels cool year round (sorry no numbers yet), is about 20 feet horizontal and 15 feet vertical from existing window units. A loop field in the bayou is essentially out of the question due to constant dredging, and the crawfish farmers across the bayou dropping their pumps on the bottom. That leaves me with pumping bayou water to the A/C's and returning it with some of the camps heat. Unfortunately, the water is loaded with mud/ silt/ stuff that I've been afraid would plug up a conventional brazed plate heat exchanger pretty quickly requiring attention that I would like to avoid. However I know that boats with water cooled A/c's often operate in similar water conditions, so what are they using? Quick google search lead me to these guys (and plenty others very similar) Self Contained Marine Air Conditioning Systems - Prices & Specifications is sure looks to me like approx 3/4 copper (they are using copper nickel for salt water resistance) with 1/4 ish A/c line in side it. The unit on the top of the page is 16,500 btu's and my quick estimation is that it has about a 12 foot long heat exchanger. I would think that it would be pretty difficult to plug up such a heat exchanger as long as I was running an inlet screen and kept the flow rate reasonably high. Any thoughts? I'm not sure how efficiant such a heat exchanger would be, but I can't see any reason not to just make it longer if it didn't exchange enough heat, I wouldn't think that the flow resistance would be dramatically higher than the tubing running to and from the bayou? Any thoughts? So at the moment I'm thinking about building something similar to what they are selling(for more money than I can spend on such projects) out of an existing window unit. Proposed steps. 1) remove condenser (or should I leave it so that if pumping fails I still have conventional A/C?) 2 ) if condenser is removed, cut fan off of shaft to reduce load on blower motor, hopefully countering some of the added draw of a pump. 3) build heat exchanger very similar to the marine units, it looks like copper is available in 30 foot coils, and I have 2 units, so I was thinking 15 feet each. More thoughts on this below. 4) Select pump install plumbing. I'm thinking that if I run the return pipe all the way down to bayou level my pump should only have to over come friction losses and counter the thermo siphon that will work against me since I'm heating on the top and cooling on the bottom. More thoughts below. 5) I'm thinking an expansion valve is the way to go here, any thoughts? There is an existing capilary tube, but I have no idea if it would be properly sized for new setup. Any ideas? 6) solder it together, add service ports charge. I'm pretty sure existing units are r-22, which I do have access to a gauge set, I also have a 2 stage vaccume pump(mine) so I just have to come up with a small quantity of r-22 unless I can figure out a good way to recover the existing refrigerant. Any easy ideas? 7) test. Plenty small enough for a kill-a-watt, and since I have 2 identical units, easy to gauge air vs water performance. I'll have to measure, but I'm guessing 40 feet of plumbingeach direction to and from the bayou. Anybody have a calculator for pump sizing? I'd like to use the same pipe that A/C hacker uses in his field (cost, durability), but connection difficulties may change my mind (only 3-4 connections per A/C all of which are easily accessible so maybe mechanical would be ok?). The marine units want 500 gallons/ hour/ ton, so my 6000 btu's should want 250 ish gallons per hour (or 4 ish gallons per minute) through about 100 feet of tubing and a strainer basket. I'd like a pump that has the ability to make 15 foot head pressure so it could self prime, but I guess that isn't strictly necessary. Any thoughts highly appreciated. Although the 16,500 btu unit uses a shorter heat exchanger coil than I am considering AND I'm only 6,000 btu per unit, I'm not seeing virtually any efficacy information on the marine units, I realize it is hard to provide due to changing water temperatures, but I AM defiantly after some improvement in efficacy and the extra copper cost isn't all that much in the total cost. Any thoughts highly appreciated here. Anybody ever use / find info on such a heat exchanger? |
First serious thought on the pump.
Little Giant PE-2.5F-PW Pond Pump 566612, Little Giant Pumps Looks around 13 foot max lift (only needed to prime) and keeps my 250 gph up to 9 ft lift which seems excessive. I'd like to do a bit more measuring, to get to 15 foot max head I'd be looking at 150+ watts running current, 80 actually seems a bit much, but I think would be acceptable. I'm thinking of putting a 5 gallon bucket in the bank perforated with 1/4" (maybe smaller?) drill holes as super corse screen, and some sort of ridgid wire screen inside the 5 gallon bucket to keep most stuff out with the pump screen after that. |
Dremd,
From what I could read in the specs, the units have a coarse SEER rating of 10.5 - 13 ish. This is about what a window AC unit has in terms of BTU cooling/power input. I bet the efficiency could be WAY increased with little modification with a larger copper exchange coil instead of the keel cooler they use. The concept of doing direct exchange has been around a long time. This simply means that instead of a long exchange tube, you substitute a shorter, but much more efficient tubing or plate. A roll of copper tubing, as you suggest would work very well. Then we need AC to look at it to determine how to better increase the EER. The unit has all the making of efficiency as it has a scroll compressor, co-axial heat exchanger - so it should not be hard. Steve |
Stevehull, where did you find the SEER ratings on those marine units? I never could locate them.
Amazing what being sick can do for project planning, I just saw randens heat exchanger here http://ecorenovator.org/forum/geothe...-pressure.html and thought of a much cheaper heat exchanger than I previously proposed. PEX on the outside, copper on the inside, use drilled pex plugs soldered to the evaporator line to keep the water side leaks away, and a simple T to feed/ remove bayou water from the heat exchanger. PEX is about 1/4 the price per foot, so I could run a much longer heat exchanger for the same $ if my selection is correct, I could make them for about $2/ ft, so 25-50 feet would not be out of the question. That said, with 1/4" refrigeration tube(my guess on stock size) a 25 ft exchanger would only have 1.6 square feet of exchange surface. |
dremd,
If it were me, I'd start out small to prove the effectiveness. Just spew water out of your pond pump pipe onto the existing evap somewhere it would only sling a little of water in the fan. Maybe up high near the top left corner? You could put in a vertical strip of something waterproof at the edge to block airflow. At a few gallons per minute, the drain hose for your window unit should be able to handle that volume of water. See if you gain any performance over air-only. My guess is that you will. Water conducts and carries heat MUCH better than air. After preliminary testing, you can decide if you want to do better. The next step could be to add a txv where the capillary tube exists now. Then maybe add water cooling to the line between the condenser discharge and the txv. This way, you would get your existing air cooling plus water subcooling. Grab a small pack of the next tube size up from your existing line and a styrofoam 6-pack chest. Twist the tube up into some shape that will fit in the ice chest with room to run to the splice point, poke a few holes above water level to break out of the chest. Rig up an overflow drain to collect warm water, then figure out how to secure the chest before you cut or braze anything. With only 1/2 ton of heat flow, you would not need a very large exchanger. Good luck, this stuff is addictive if you have the skill and patience! jeff |
Dremd,
A quick calculation of the SEER can be had by dividing the btu output by the power in watts input. Not perfect, but a close approximation. Steve |
Dremd,
Another thing to consider doing with the smaller units is using them in "reverse polish" mode. I have found that the heat exchangers in the smaller units can only be pushed so hard before they become the bottleneck in your quest for high efficiency. The outdoor heat exchangers in these units are designed for massively more airflow and exchange area than the indoor coils. By installing the unit backwards in the window, reversing the connections at the compressor, and adding to the smaller (now outdoor) exchanger to gain heat transfer, you can run the unit at a lower speed to save motor energy while still pumping maximum btu's. This also has the benefit of being able to work on the unit indoors where it's a comfortable temperature. Most window openings are at a height where you can comfortably sit in a chair or barstool to do work and take measurements. Don't laugh, this works, really! I am using this method to do testing of some suction line heat exchangers now. It really helps your patience factor when you're in a normal environment. No need to worry about rain, snow, wind, heatwave, frostbite, etc. |
Quote:
It sure would be useful if you could get some loops into the Bayou water. I certainly understand why you can't, but it sure would be useful. So, as I understand it, you're 15 feet above and 20 feet back from the bayou, right? So, your water table is 15 feet beneath your camp. Other than getting loops into the bayou, your answer is 15 feet below your feet. Too deep to trench, but a rotary water drill just might work really fine. You ought to do a little asking around about your soil conditions near your lodge. Ask well drillers, ask GSHP drillers (for use in A/C). All of the drilling problems that I had personally, were due to rocks that were left after prehistoric recessions of ancient glaciers. In fact the other folks that I know in this area, who had problems drilling, had those problems because of fist-sized to football-sized rocks and cobbles. I just bet that it has been many, many, many millennia, since Louisiana has seen any glaciers. I have heard of very easy drilling done by some of our Southern Brothers, who encountered nothing more serious than sand and clay... so before you pull the plug on the idea of drilling or trenching, tap into the knowledge of some of your local drillers. They may tell you that it is truly unreasonable to DIY something like that, and that you need Very Big Power to punch holes in the ground. If that is the case, then don't proceed down that road. But if you are not up against cobbles or bedrock... you could have a very good chance of success. It's amazing how, once you start asking around, local lore on this issue starts to come out of the woodwork. Some closed loops sunk down into the water table a pretty good way would sink a lot of heat, and you wouldn't need to worry about anything ever silting up or getting clogged by some kind of green swamp growth. But then there's that bayou... how deep do they dredge it??? I don't know if you have gone over any of Brad_C's posts on EcoRenovator, but he is doing a DIY open loop A/C, in Perth, Australia. He isn't on a bayou, but he is utilizing flowing ground water, and he has had to deal with filtering out stuff that could clog his HXs (yes, he is using a huge brazed plate). Brad_C is Brad_C, and he seems to be pretty much unstoppable. But for you, a mortal, you are right, an open loop system is not the place for brazed plate HXs. Acuario, over in Spain did some interesting work with homemade HXs... In fact I think he really started a DIY tube-in-tube trend. Then it looks to me like randen, up near Toronto, Canada, took Acuario's idea of how to DIY a tube-in-tube and made it simpler and even better. So, you can build your own tube-in-tube that wouldn't be prone to clogging. Hope I've been able to get your gray matter bubbling just a little bit here... And yeah, those marine units do look pretty nice, if you have the cash... but they still need water. Good Luck! -AC |
I woke up this morning thinking about your bayou camp cooling problem...
I realized that there are quite a few issues that I had assumed about your camp, that I really shouldn't have.
Please advise. -AC |
Quote:
|
Quote:
Thanks for thoughts for sure, and for making me feel a bit less wacko. |
Quote:
Quote:
Quote:
Quote:
Quote:
That said, drillers start seeing large solids around 500-1000 feet and that is typically coral (I've got a nice piece of coral on my shelf from 2,900 feet below a few miles from my house). The majority of the well drillers I know drill for oil, not water. Quote:
They may tell you that it is truly unreasonable to DIY something like that, and that you need Very Big Power to punch holes in the ground. If that is the case, then don't proceed down that road. [/QUOTE] I have known people to DIY vertical wells near camp, apparently not terrible. Quote:
Quote:
Quote:
Quote:
Quote:
[QUOTE=AC_Hacker;29459 Good Luck! -AC[/QUOTE] Much awesomeness, thank you very much! |
Quote:
I'm not entirely sure how to describe my self, my skills, nor what I do, but I'll give it a shot by listing some of the things I've done in the recent past with little outside help. 1) built 3d printer(s) (well, this was 2009) 2) built fiberglass mold/ production setup/shop. Built lots of 4ft fiddles 3) setup chineeseum lathe to make 3d printer parts, ended up making lots of other stuff as well (I really like this darn thing). 4) built 4x4 CNC plasma cutter (most impressive tool in the shop) to add to fairly extensive metalworking shop (MIG welder, handheld plasma, brake, sheer, anvil, cones, swede blocks,casting setup, presses, etc, etc. ) 5) in progress of swapping a Diesel motor + 6 speed manual trans in to a turbo gasoline automatic VW wagon. 6) built tire mounting/ balancing gear (cheated on mount bar). 7) swapped a new bottom end in to my dads Freightliner sprinter (van) after some dealer monkey failed to torque any of the rods. I generally just do it/ figure out how to make it happen. Quote:
Unfortunately, loot is a department I'm short on (not desperately so), if I had lots of it I'd just spend it on more/ nicer tools. Quote:
No one pays to stay at camp, but it would be nice, I do have a buddy living there right now while he moves from the New Orleans area. Quote:
Hopefully my rent free tenant will fix it up enough so that it would be used a large portion of the time, say 25-50%? Then again, I get 200 meg Cable Internet there, and here (from which I can see a McDonald's, churches chicken, 2 gas stations etc if I stand on the roof) I have to WiFi 6 meg unreliable DSL a mile to use in my house, so maybe more. Please advise. -AC[/QUOTE] |
I've been thinking a lot about tube in tube heat exchanger construction, and realized the guys running plastic external tubes are doing heat only so their heat exchangers are COLD (duh). Mine would be hot, so I'd need copped at least on the hot side.
Maybe 10 feet copper-copper then the rest copper-PEX with a thermal cut off. More thoughts, maybe what would be equally energy saving would be web connected thermostat (NEST at least looks pimp) such that the cooling could be switched to a lower setting several hours prior to arriving. I suppose either a contactor, or a solid state relay with a bit of re-wiring would make that happen. This would also have the benefit of getting the thermostat away from the A/C this making it much more accurate. Anybody have any experience doing such a "conversion" to a window unit? As another note, sorry for the terribly slow response, for some reason I didn't get a forum notification, I probably have this thread open in a browser window someplace. |
Thoughts keep coming:
I have an unused water well near by (20 ft?) now that I have city water. What if I drew water from the well, and returned it to the bayou? I'd have a foot or 5 of lift involved, and not any longer be able to use a submersible pump (which would likely eliminate self prime, so a high temp limit switch would become required). However the biological slime would be nearly non existent, and particulates would likely be low with my modest flow rates. Still open loop, still limited site work, little bit more water pump requirement, but potential for reduced clogs. Thoughts? |
Quote:
Quote:
Quote:
In contrast, air-sealing and well-insulating a leaky, uninsulated building will always pay themselves back many times over and over without any upgrade of your heating or cooling source. A small solar roof vent would do magic for this little house IMHO. Especially on a sunny summer holiday weekend. |
Dremd,
Any progress on the project? Summer is right around the corner... |
Unfortunately, not yet, all of my Eco-modding is currently going in to my automatic 1.8t-> 6 speed manual TDI VW motor swap.
|
Poking this one again, sounded very interesting!
|
I'm still very interested, I've pretty much decided to start with 1 unit (there are now 6,500 BTU, 8,000 BTU, and 10,000 BTU units), draw water from the unused well, and return it to bayou, that way I don't have very much pump head, and fairly low sediment (esp at lower flow rates). Next step is selecting pump, I'd like one that could self prime, if not I'll have to engineer some sort of anti-drain back system (check valve??). Any pump suggestions?
I'm fairly settled on a tube in tube heat exchanger with the hottest 5 feet being copper, and the remainder (maybe 25 more feet) being PEX with a high temp shutoff located at the junction of the copper outer pipe to the PEX outer pipe. A thermal disc should work great, its only there so that when pumping fails I don't cook the PEX + likely the unit. I've seen few TXV's in that size range, anyone have a reliable source? Biggest hold up is MY TDI swap which is taking WAY longer than anticipated. After that, next up grade will be a NEST with 8k as stage one and 10k +8k as stage 2. Advantages of NEST for me Humidity monitoring (biggest reason A/C runs there) De-humidifier trigger (may add regular de-humidifier on a solid state relay) Ability to monitor + control A/C's remotely so I can have it cool at arival. no need to cycle Blower to sample air (wasteful of energy and makes extra noise when sleeping) |
Open Loop, Open Loop, Open Loop !
Open loop is way easier, cheaper and THE most efficient way to go. We use 1/2 HP jet pump to feed a Trane water source heat pump (24000 BTU) to heat and cool a 2600 Sq Ft house. Saves us tons o money! Our water temp varies between 46-49 deg F. Reject into a grey water weeping field. In your case back to bayou. Coils in the ground or in the water too costly and innefficient. Keep it open loop man, especially if you have well nearby. Thumperoo
The unit’s internal heat exchanging water coil is engineered for maximum heat transfer.The coil is a tube within a tube design.The inner-water tube contains a deep fluted curve to enhance heat transfer and minimize fouling and scaling. It is available in either copper or cupro-nickel (selectable option) coil.The outer refrigerant gas tube is made from steel material. |
We bought our trane water source heat pump for $1200 on Kijiji. Just saw plug in water source heat pump on E-bay. Just saw a trane for $950.
Thumperoo |
You can also look at these marine units. Self Contained Marine Air Conditioning Systems - Prices & Specifications
|
You can also look at these marine units. Self Contained Marine Air Conditioning Systems - Prices & Specifications
They run on water pumped from sea (saltwater and crap from harbour). They just have good quality strainers and baskets to filter out nasties. Look at the condenser (tube in tube) at bottom of web page link - looks like what you are trying to do. |
Quote:
|
Quote:
|
Ok, so I see you've decided how to do this project. You're going to draw well water to feed your condenser and discharge it into the bayou. For heat exchange, you plan on doing a tube-in-tube or tube-in-shell design. You plan on keeping the capacity under a ton (12kbtu) for each unit and you're not combining compressors for some kind of multi-capacity staging. You may hack multiple units, but each will have its own supply of cool water from the well. Am I right?
To address your concerns about the condenser, a single tube or coil of copper inside plastic will do fine. You're not going to melt or burn up pex or pvc pipe with a half-ton compressor unless you lose your water jacket. The compressor would surely trip out on its own overload many times before the discharge line got hot enough to melt anything. If in doubt, just use iron pipe. The only real choice to make in the condenser design is the length. If you can deal with a big loop, you can use 1/4 inch annealed refrigeration tube (don't get icemaker line) inside 1/2 inch pex and just make a couple of large loops. If you need something short, you can wind the copper into a coil and put larger pipe around it. For 15 feet of 1/4 inch tubing, this is way more than a ton of capacity with any substantial amount of water flow. What comes to mind here: using a 3/8" iron pipe as a form, the coil would fit inside a piece of 1-1/2" pipe 3' long; using a 1" pipe as a form, the coil would fit inside a 2" pipe 18" long. If you were planning on a larger (~20kbtu or more) condenser, a more elaborate condenser (with better flow and heat transfer) would be needed to get ultra-high efficiency. Lucky for you, because your setup is small enough to be simple. TX valves can be found cheap every day on ebay, here's one today: 1 ton (12k btu) http://www.ebay.com/itm/AAS-1-HC-Eme...item35c9359d0b You can also surf to surpluscityliquidators.com and find everything you might need cheap. They have a 1 ton turbotec coax coil for $31.00 today: http://surpluscityliquidators.com/vi..._TON_COAX_COIL |
Quote:
Quote:
Quote:
What is your estimate of required water flow? I'd like to keep the pump small so as not to drain all of my efficacy gains away in pump watts. I really need to do some testing, I think I only have to pump 4-6 feet of lift with my site, but I need to verify. Quote:
QUOTE=jeff5may;30499] TX valves can be found cheap every day on ebay, here's one today: 1 ton (12k btu) Aas 1 HC Emerson Alco TXV Expansion Valve R22 | eBay You can also surf to surpluscityliquidators.com and find everything you might need cheap. They have a 1 ton turbotec coax coil for $31.00 today: TUROTEC | COILS, STEAM & WATER | 1 TON COAX COIL | Surplus City Liquidators[/QUOTE] I can't remember, I want to run a TXV that is larger, or smaller than compressor capacity? |
Ideally, you want to find a TXV that is rated the same btu capacity as your compressor, at the same temperature range, with the same refrigerant type, with the right sensing bulb gas, with the same size connections as your unit dictates. To put a TXV in a stock unit, the manufacturers say it must be the same as what came out or it will void your warranty.
For us, some of these rules can be bent. For instance, you can go up or down 1 size in capacity and the unit will still do its job well if you don't go out of its range. In your situation, a water-cooled condenser will develop a gob of subcooling during normal operation. This drives down your head pressure, so the TXV would open wider than it would with an air-cooled condenser to let through the same amount of liquid refrigerant. So you would want to go up one size if you can't find a cheap TXV the same capacity as your unit. That way, when you arrive to a hot home and start the unit, it could "follow the evaporator air temperature up" by opening wide without maxing out its flow. Some of the rules should be obeyed, though. You want to get a valve the same type as your refrigerant. You want to stick with a high-temperature unit that's not made for a blast freezer or a cryogenic unit. Unless you like making and assembling flare fittings, find a valve with sweat fittings. The discharge side will likely be too large, but that's ok. Sweat some "too big" tubing into the valve and run it close to the evaporator before reducing the size. It will act as an expansion chamber, allowing your refrigerant to vaporize better in the evaporator. |
Here's an article that explains TXV's practically:
http://www.emersonclimate.com/Docume...re-article.pdf |
You'll notice that those turbotec coil-in-coil have the outside tube in steel and the inner "swirled" copper tube. The refrigerant is not in the copper inner tube - its between the two tubes - better heat transfer. And they're probably cheaper, less hassle than fabricating annealed copper within pex. $32 !!!!
|
I actually ordered the 1.7 ton version for extra oomph. Not much extra $ over the 1 ton. Unfortunately shipping was about the same as the item, even shipped ground, I'll post when it arrives.
Edit : this one https://surpluscityliquidators.com/v..._TON_COAX_COIL $80 Shipped, I didn't know such a ting was available for purchase, otherwise I'd have bought one a while back. |
Sorry, I didn't see that the 'working fluid' was refrigerant... therefore no galvanic problems.
However, the 5/8" water input seems restrictive, so more pump power might be required to achieve the water flow to reach 12,000 BTU/hr. Acquario made his own HXs using ABS pipe for the shell and multiple copper coils for the refrigerant. His water input & output were sized large. -AC |
There's probably more restriction in take-up pipe and pump to hxr than whole of hxr. Our Trane 24000 BTU/hr unit has 3/4" inlet/outlet that reduce to the similar hxr with 5/8" water connections. The Trane application charts state between 4-7 feet of head thru unit for flow rates of 3.5 - 5.0 GPM. No worries there. Scaling, mineral deposits and bayou crud may prove problematic over long run.
|
Just put in fittings so you can isolate and flush the exchanger and you'll be fine. This is recommended for on demand water heaters and seems to work quite well for them. I did this when I installed mine:
http://ecorenovator.org/forum/applia...-heater-4.html http://ecorenovator.org/pictures/house450.JPG |
Agreed on Valves, I'm planning on doing pretty much exactly as your tankless is setup so I can flush both directions with city water.
I'm planning on running a very very corse sediment filter (about window screen size) that I happen to have left over (from random water recovery project) between the well and the pump to reduce the sediment load. |
Quote:
|
A little bird told me 200 gallons per hour per ton is your ballpark rate. The way the practical hackers do it is to start the unit from a hot indoor ambient (hot, summer day after 2pm) temperature, wait 15 minutes, then feel the condenser and output stream. Adjust your flow control for warm, but not hot, output temp (around 100-110 degF). Discharge pressure should be below 250 psi for r22 or r290. The little bird told me 200 psi is normal.
|
Quote:
I do realize that you are doing a pump and dump, so you don't need to contend with the relatively complex field like I had... and your pumping power will surely be less. But if you haunt the Taco Pump pages, there you will find the tables and formulas you need to calculate the head loss of your system, based on pipe diameter, pipe length, fluid velocity, fluid viscosity, and the number and size of any restrictions in your system (I believe that the 5/8" tube entrance may be a restriction). BTW, the flow rate rule of thumb fro GSHP is 3 gpm per Ton... and as a rule of thumb it is just the first-cut estimate, and not the final design criteria. -AC |
The coax coil arrived!
Significantly heavier and more solid than I expected. It appears to be never used, and of high quality, I'm very happy with it. If I didn't have someone in the camp right now I'd pull the 10k unit apart, remove the condenser and replace it with this shortly, however, in current weather all A/C's are needed to re-cool the camp after allowing it to warm while they are away at work. So this will have to wait until mid 80's return. Very good news, my TDI swap runs, so I can put some effor in to water plumbing+ pumping. |
All times are GMT -5. The time now is 04:33 AM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Ad Management by RedTyger