I just joined and found that many are interested in ORC Power generation. I have developed a 10KW ORC Unit. I tried smaller version but the heat exchanger and heat source of low capacity was difficult to design.
My first loop is Power Loop - Turbine----> Condenser---> Compressor----> Evaporator---> Turbine---
The second loop is Heat Loop - Biomass/gas fired Thermic Fluid heater ---- 300 LPH of 250C ---> Evaporator Inlet ----> Discharge back to heater----
If you use LPG, you require 0.1M^3 per Hour. When CNG/PNG is used, the system will consume 0.13M^3 per Hour. If Biomass of 2300K.Cal/Hour is used, you require about 500 Kg fuel per hour.
The fuel is fed automatically.
The complete system costs US$ 36,000 C.I.F....Major Port of any Country directly connected with Indian Port. You may contact me at email@example.com for any assistance.
Been away from this for way too long.
About the high RPM Auto Alternator: would it not be better to use an Axial Flux Home made Alternator ?? They get big output at under 1000 Rpm's. One could be wound for whatever voltage and Amperage you require ??
They use Perm magnets, magnet wire and a fiberglass reinforced solid resin stator. Trailer axle spindles work fine, and, Auto spindles can be used for more output, if desired.
I have seen these described on most wind generator websites. A permanent magnet large diameter generator such as you describe may be more efficient than an auto alternator due to the power the auto generator needs to power it's rotor winding to make magnatism. Unfortunatly, you have to BUILD one from scratch and there is cost in both time and treasure. - ALSO - A permenant magnet alternator is much more wastefull once you add the required voltage regulator. The way most PM alternator regulators work is by shorting out some of the alternator windings to reduce the output power. Most motorcycle alternators and regulators operate this way, the argument is that since the output from the shorted winding is producing "0" volts the short is not creating a power loss - WELL - calculations may indicate that since power (watts) is calculated by multiplying the output volts X amps, "0" volts has to equate to "0" watts, but in reality the output is not really "0" volts since there will be some voltage created across the Silicone Control Rectifier that is used to create the short. Since the winding is nearly shorted it is producing it's MAX amps as an output, even a small voltage at max amps can create a LOT of heat, this is why most motorcycle alternator windings burn out after a few years at best.
There are more efficient regulator circuits that can be built using Pulse Width Modulation and switching regulator technology but these also can have drawbacks. First, I don't know of any that are available off-the-shelf, you have to build them yourself. Another problem has to do with the physics of the alternator winding itself. If the output of the alternator winding is not connected to some load the voltage created by the permanent magnets flying past it becomes VERY high, it can be on the order of several hundred volts. Voltages this high will likely exceed the voltage rating of the coating on the wire that the winding is made from so you run the risk of the coating breaking down and allowing a spark to jump between the winding wires and/or to ground. Once a spark jumps you will have an internally shorted winding that will no longer produce output power for the alternator but WILL produce heat internal of the alternator. So, the most efficient regulator for a permanent magnet alternator gets a bit complicated as it must provide SOME load for each winding to keep the voltager from becoming excessivly high and still convert whatever voltage is available from the alternator winding into the desired regulated output voltage and current.
It may be more doable with one of these home built PM alternators since you can bring out both the ground and the plus end of each winding, this would give you far more control of the regulation. I will have to read more about the most recent designs folks have come up with. Regulation is not as much of a problem if you are dumping the alternator output into a big battery bank as the batteries can absorb all the power but a small battery bank can easily become overcharged unless the alternator output is diverted into some other load, like a heating element, or maybe a motor to lift a 5 ton weight used to turn a gravity powered generator?
Auto alternator - The speed that the alternator needs to be turned for full output is directly proportional to the diameter of the alternator rotor. Most newer auto alternators are designed to be as small as practical to reduce there size and the amount of copper wire that is required in them thus they need to turn quite fast, upwards of 4000 rpm. There small diameter also requires them to use a good amount of current through there rotor windings to produce the magnatism needed to produce full output power. During the 1970's and 80's Chrysler full sized vehicles like station wagons and actual Chrysler cars used what was refered to as a "high output" 100 amp alternator, this was also available on any vehicle as an option. These high output alternators have a larger overall diameter but are still only 9 inches in diameter including the mounting tabs, they are available at junkyard prices of around 25-30 bucks. These alternators will produce there rated 100 amps and 12 volts at about any speed over roughly 1000 RPM, If you use or build a 24 or 36 volt regulator to control there rotor current they will output almost as many amps at these higher voltages at someplace above 2000 RPM (they will run hotter so you need to be aware of that).
I find the large diameter auto alternator option to be the most practical and I can keep several on hand as spairs. They take less than 10 minutes to swap out and you can still order rebuilt ones through your local auto parts store.
I am still trying to get the old outboard motor power hear apart, snapped off several rusty screws already so am taking more time to allow the penetrating oil to soak in, looks like it may be a few weeks before I know it it will work as an expander or not.
Web searching I ran into THIS interesting 129 page PDF research paper, it is for a theoretical 2KW ORC system but also has real world testing using a converted scroll air compressor as the expander engine. It also has an understandable description of which working fluid to choose and why as well as info on flat plate condensor heat exchanger efficiencies and calculations.
That was quite a write up, Tim.
Only reason I mentioned the Auto Alternator, was, there are guys making motors using these Alternators. Electronic Engineers are saying, the material in the Stator windings is a very poor choice for flux currents. The steel is not the correct blend of steels. Also, the use of the claw type rotor is also very inefficient.
I converted one, using Donut shaped magnets inside the rotor claws. I need to take the Alternator apart, which will need a special puller build, because of those magnets. Then, place Hall Sensors in the correct areas of the stator, so a sensored controller will start the alternator turning. My claws were not driven back on, and, I'm sure they twisted out of relation to each other, just a bit.
In battery charging, I have concluded the batteries will control the amount of voltage allowed to flow, but, I know the Amperage will overcharge and boil or heat the batteries. I was thinking of using Water heater elements in a water tank, to use as a dump controller. We always need hot water, anyways.
I ran across another guy that is deeply into this ORC device, and, he sent me some info, that I will need to print out, take out in my shop, and sit and read and re-read, to understand what his ideas are. I can't do that in the house, while my wife is around. Just can't concentrate.
Your thinking is way ahead of mine, and, if I glean anything useful out of this new info, I will put it on here, for you to de-cypher.
I wonder how many watts one may be able to produce off of a huge alternator salvaged from a huge industrial diesel? I know "huge" isn't too exact a term, but I think you bros see where I'm going with that. Perhaps respectable higher wattage ORCs can be made using something like the alternator off the engine(s) from a trans oceanic container ship...
The most basic decision one has to make about choosing the generator/alternator has to do with what you intend to power. My use of a small solar ORC system is for charging batteries in an off-grid application, this requires low voltage DC power so some version of a small 12-24 volt alternator makes sense, the cheapest and most available source of these are some version of automotive alternators, there output power is also easy to regulate using some inexpensive compatible automotive voltage regulator.
Any size DC generator can be used if you have the power to turn it. One aspect of a DC generator is that you don't have to control the speed of the motor powering it. If you are using a normal self-exciting AC alternator (your normal small gas engined generator type thing) you have to control the speed of the generator to insure 60 cycle AC voltage, as well as control the actual voltage output. If you use an externally excited induction generator you do not have to control the speed of the unit as closely, it just needs to turn somewhat faster than the frequency you are exciting it with, not sure how the output voltage is controlled with one of these. An induction generator is not quite as efficient as other types but much easier to synchronize to match the existing power line frequency.
The large commercial ORC power producers are grid intertied and produce synchronized 60 cycle high voltage. From what I am reading about the commercially available turbine generators used on these systems they use a somewhat modified off-the-shelf centrifical rotary air conditioning compressor as there turbine expander/generator. In the air conditioner application the centrifugal compressor is turned by a directly attached high HP AC electric induction motor, when using this same package as the turbine expander they simply use to motor as an induction generator by applying AC mains power to one of the 3-phase windings as a source of the generators magnetic force, this also automatically synchronizes the phase and frequency of the generators AC power output to the power lines that it is feeding power to. I don't know exactly what the specs are for this motor/generator but I suspect is 3-phase and probably either 440 or 880 volts AC, the voltage output of the induction generator could then be transformed up to whatever is needed to match the power lines it is feeding, could be 1600 or 3200 volts, possibly even higher.
THIS LINKS TO a past Popular Mechanics magazine article about the two 200 KW ORC AC generator systems installed at the Chena Hot Springs off-grid resort in Alaska, they are using hot underground water as there heat source and cool surface water for there cooling. They use something like 250 KWs of AC power continuously to power everything at the site so there generators are AC motors converted to work as AC induction generators.
This picture is of one of there 200 KW turbine/induction generator modules. The turbine is the thing with the tapered nose at the top left of the picture and the 200 KW induction generator (motor) is the big cylinder mounter horizontally on the left end of the turbine.
turbine_and_induction_generator_assembly.jpg (16 Kb, 8 downloads)
I'm sure you guys have already seen Robert Green's steam engine (http://www.greensteamengine.com/index.html). According to him, the engine can be used as an expander in an ORC system but it has to be enclosed so that the vented working fluid can be captured and recycled. Has anyone here considered using one of these engines or would they just not be efficient enough for use in an ORC? Green offers plans for building a 2 cylinder version that, using steam, can output up to about 10 hp. I believe he states somewhere on his website that it can be built from off-the-shelf parts using ordinary workshop tools (nothing more than just a drill press). Would these work?
Hi Guys, looks like there has been plenty of action in this thread since my last visit months ago so will try to catch up.
The main idea underlying my project is to construct a DIY biomass boiler ORC system which is built using a majority of recycled parts and at low cost. Quite a task!.
I have now constructed a prototype ORC system using mostly scrap parts and i'm playing around with it at the moment trying to work out how to use it!!. At the moment i have a vapouriser which consists of 66 plates and although it is very under sized it still produces enough vapour to spin my scroll turbine (car air con compressor) albeit pretty damn slowly. Ideally i would have 3 times the vapourising capacity to get decent power, but that will have to wait until the scrap man has the required merchandise!
I also need to find a decent sized condenser which has a good flow rate as this is a major weak point in my system at the moment.
So, although not fully working yet the project is moving in the right direction and does have some potential, i hope!.
I have put a video on youtube showing my current prototype, perhaps you could have a glance and give some feedback. Please disregard any invitations to buy memberships to my website as i regard anybody who contributes valuable information in forums as having helped me out, therefore qualifying for a free membership if they want to join. The membership fee is really for people who like the idea of the project but can'y contribute anything other than a small fee to help out (3.99).
The video does show the turbine spinning but due to me having over filled the system with butane it is not operating as well as it can do due to the condenser and surge tank being too full. I will hopefully rectify this in the coming week and make a better video.
Hi Guys, i'm going to give a detailed description of my system in the hope that you guys can suggest some improvements. I have been all over the web looking at forums concerning self building ORC systems and i can say with confidence that this forum is by far the best in terms of ideas,links and effort put into posts, good work fella's.
The system you see in the video i linked to in my previous post uses vapourised butane to drive the turbine. The system is operating in an anti clockwise fashion with the vapourisers below the turbine and the condenser to the left of turbine.
Vapouriser: (Located bottom right of mounting board) 5 different small plate heat exchangers salvaged from the scrap man (total 66 plates), they are piped in parallel from a 1/2 inch headers. The flow header which feeds the turbine reduces to 10mm micro bore before entering the turbine inlet port. All joints on high pressure side of the vapouriser have been silver brazed for high strength.
Main circulator: (Located bottom left of board)12v, 6 watt pump supplying the return header to the vapouriser. Each vapouriser heat exchanger has an isolation valve which is used to balance the flow delivery. The main pump draws liquid Butane from the main reservoir (which holds about 1 litre). The main pump can deliver up to 7 litre per min, which is ample. The use of a 6 watt pump is possible due to the pressure equalising tube which balances the pressure between the high pressure side of the vapouriser and the main reservoir, preventing high pressure differentials and the necessity to have a large and powerful pump.
The balancing tube diverts a small amount of the butane vapour flow to the main reservoir which reduces the amount of flow available to the turbine and therefore the power (bad news) but i hope this is offset by the low power requirement of the main pump.
Turbine: (Located Top Right) Air conditioning compressor with scroll element taken from: Ford Mondeo mk3 (2002) 1.8l Petrol. They are very cheap and very effective. The turbine was modified by removing the internal check valve and running in reverse. very simple mod. Purpose built to handle HFC refrigerants so perfect to use with Butane.
The turbine is self starting which is a major bonus and it can cope with liquids without blowing a seal. I had looked at trying to modify a 2 stroke engine but soon ditched the idea when i found out just how good these modified auto air con compressors are. It will run at 5 Bar inlet no problem so long as you can maintain a pressure drop by using a big condenser. I added a few squirts of engine oil to help it seal and lubricate.
Condenser: (Located top left in bucket) Currently a coil of micro bore copper submerged in a bucket of water!!. It is not yet big enough to dump enough heat to maintain the pressure drop across the turbine so i can't run the system for long. I will need a large plate heat exchanger with good flow rate in order to condense the vapour fast enough.
Surge tank: (located under the bucket) A disused Rothenberger propane cylinder. As the condensed liquid leaves the condenser coil it flows into the surge tank where it collects, when the surge tanks fills up i turn on the shunt pump to transfer the liquid into the main reservoir. The shunt pump circulates through a double check valve which prevents vapour from bypassing the turbine into the condenser. Once the surge tank is empty the pump turns off.
Shunt Pump: (left of centre)a 240v DAB domestic central heating pump with 5m head. Consumes 85 watts.
Main Reservoir: (bottom left) A black Rothenberger propane cylinder
Working Fluid: Butane, (more info) http://www.altenergy.com/Downl...blic/PropDataPdf.PDF
I received and fitted a 40 plate heat exchanger as the condenser today, expecting to see some marked improvement in performance. However, i still have the same problem as before:
As i open the throttle to feed butane vapour to the turbine the pressure in the condenser starts to rise until it equals the turbine inlet. At this point the turbine stops spinning as one would expect.
When i initially tested the new heat exchanger with compressed air it seemed to be very restrictive and i could'nt get much flow rate through it. Once fitted the same is true on both the cooling water side and butane side. I am hoping it is not knackered (ie, blocked with swarf).
So at the moment i am confused as to how i should solve this condensing problem. I know my vapouriser is delivering enough flow rate to spin the turbine, but spinning can only happen if the condenser is creating a pressure differential across the turbine, therefore a flow of vapour, right?.
All the other prototypes i have read about have a condenser which is smaller than the vapouriser and they seem to be able to get a constant pressure differential without problem, so i'm wondering what i am doing wrong??
Guys, any suggestions much appreciated.
After giving the heat exchanger a good power flush i refitted it.
Slight improvement but still not perfect, can only achieve about 5 litres per minute cooling flow but i'm pleased to report that 5 lpm is enough to get it running.
Achieved about 300 rpm today and posted a new video on youtube, see link:
At last some success!!
Great work, it looks like you have done the most actual development on this. I still think about it and hope to do more testing eventually.
Condenser - I have not watched the vid (SLOW dialup web connection) or studied your system closely yet but from general reading is seems that the condenser needs to be MUCH larger than the evaporator due to exchanging heat from the much less dense vapor rather than a dense liquid, how much bigger depends on how the condenser is cooled.
I intend to use salvaged tube-n-fin type radiators like are used as the evaporator and condenser found in home type window or larger whole-house air conditioners. I have pulled several large flat 6-7 sq ft area fin-n-tube radiators from my local salvage yard, these have at least 5/16 inch ID tubing, some even have 3/8 tubing, and one has 1/2 inch tubing. Some have more than one circuit in the same radiator, the outputs are parallel plumbed into a large 1 inch manifold pipe and each input is fed from the liquid source by it's own copper capillary tube, these will all need to be refitted to flow higher volumes of vapor by replacing the tiny capillary tubes with much larger tubing. I will have to do testing to determine if these need to be plumbed as several smaller parallel radiators or one large serial radiator, I suspect one large serial radiator will work best as the lower section of it can be used to hold the condensed liquid rather than using a separate accumulator tank?
These are normally cooled by air pushed by an electric fan but if I mount them almost flat (horizontal) they should cool by convection flow of the air they heat. There will be no fan used to save power. The system will probably require several seriesed radiators to do the condensing. By placing each radiator on a slight angle from horizontal, and placing each individual radiator lower than the one before it, the condensed liquid should migrate to the lowest point no matter where in the radiators the actual condensing takes place.
From testing I have done using this concept to condense vaporized propane, It appears that the condensation takes place in sort of "glugs" rather than a smooth flow. I had pressure gauges at several points in the setup, the vapor pressure in the source tank stayed pretty steady until the vapor was all removed, at that point the pressure dropped at the rate based on how fast the tank was being emptied. The pressure gauge on the condensate tank would show a few pounds rise in pressure and then instantly drop back a few pounds as a slug of vapor condensed, apparently the drop in pressure was enough to stop the condensation until the pressure built back up to the point vapor would again condense. The general pressure at the collection tank was dependant on the temperature of the pressurized vapor.
The setup I was using was a small converted 5000 BTU window air conditioner, I left the fans in place to move air through both the condenser and evaporator radiators, I replaced the capillary tube between the condenser and evaporator with 1/4 inch ID tubing. vapor was fed into the input of the stock frig compressor, the output of the compressor fed into what was originally the condenser radiator. By replacing the capillary tube with a larger tube the original condenser and evaporation radiators effectively just became one larger radiator. The output of the last radiator fed into another propane tank used to store the liquid.
I did not have enough radiator surface in this to condense the vapor in the radiators so the condensation actually took place in the collection tank. The tank ran quite warm due to the adding heat from the compressed vapor. Running the setup using only air cooling the pressure required for condensation ran up above 400 pounds, by cooling the collection tank with a spray of water the pressure would drop down around 350 pounds, by adding a water spray to the radiators, along with the fan moved air, the pressure was around 300 pounds, with water spraying on both the radiators and the collection tank the condensing pressure was down around 250 pounds. This was at a summer day temp of about 80 deg f.
For your testing an air cooled tube-n-fin type radiator could be submerged in a few gallons of water to improve it's efficiency.
More condensing square footage than might actually be required won't hurt anything so erring in that direction looks like the better error.
Scroll compressor as expander - Nice that this is working. Does your unit have an I.D. tag with the manufacturer and part number shown, my local salvage yard has a couple barrels full of auto frig compressors but no clue as to what vehicles they came from.
Stu: I didn't see any mention of temperatures in the postings, are they mentioned in the videos (I'm also on slow dialup, so I haven't seen them)? Heat exchanger performance is determined by temperature deltas, flow rates, and the working fluid characteristics, as I'm sure you know. The smaller the temperature difference between the air and the refrigerant you're trying to condense, the larger the heat exchanger needs to be. If you are trying to condense butane vapor that is "cool" from expanding through the turbine, then the heat exchanger needs to be even "cooler". Perhaps all your system needs is to operate at warmer temperatures, in order for the condenser to work. I think it was Tim Cook who suggested submerging it in water, and I'd add to try really cold water, maybe with ice in it, just as a means to get things going long enough to get some performance numbers.
In school we did "heat balance" tests on various engines and HVAC equipment. At each critical point in the system was a pressure gage and thermometer. I learned a LOT from those tests, especially that the thermal- and gas-laws were unrelenting.
I'll take my laptop to town tomorrow to watch the videos - this is a fascinating subject.
Hi Tim and Johno,
Tim the expander is an air con compressor taken from a Ford Mondeo Mk3 Petrol 1.8L. The same compressor is used on many of the ford cars and vans in the UK. Here's a link:
Luckily there are loads of them about.
The condenser will need to be at least equal to the vapouriser i think. The bigger the better as this will cause more pressure differential. I will try to recuperate the heat from the cooling water back into the butane just before it hits the vapouriser, that should boost efficiency a sniff.
Johno, here are some figures:
Simulated Boiler: 2.2KW Kettle
Boiler Flow Temp: 65 Degrees C
Boiler Return Temp: 52 Degrees C
Vapouriser Temp: 55 Degrees C
Turbine Inlet Temp: 55 Degrees C
Turbine Exhaust 40 Degrees C
Condenser In : 40 Degrees C
Condenser out: 20 Degrees C
Cooling Water temp: Mains ambient (10-15 Degrees)
Cooling water flow rate: 4-5 LPM estimated
Vapouriser Pressure: 6 Bar
Turbine Inlet Pressure: 6 Bar
Turbine Exhaust Pressure: Not known yet
Condenser Pressure 5.5 Bar
These are slightly rough as they were taken with a bi metal temp sensor which was'nt fixed to the pipe all that well, pressure is accurate enough though. i will endeavor to get more accurate temp measurements soon.
I will try to get the flow temp up but i think it will take a bigger boiler/kettle! might buy a 3kw. I need to insulate the boiler and pipework properly as well.
I took the plunge today and bought a 60 plate exchanger to use in the condenser. That should do the trick and clear this up once and for all.
No idea on torque or power output yet but i will try to rig up a small motor to use as a generator to see what i'm getting. But really without a recuperator it will be pathetically low. It may be pathetic even with a recuperator but at least it will be off grid and free if i use waste wood from the tip.
Stu - Searching to find some equivalent Ford vehicle here in the U.S. that might have the same frig compressor as the Mondeo, the MK3 was a model that was different from earlier models and reading through THIS WIKIPEDIA page seems to indicate that there is no direct equivalent for it here in the U.S. Searching the web for a compressor for the Mondeo seems to show that the same compressor used on the MK3 was also used on the earlier MK2 and wikki shows that the MK2 was sold here in the states as the Ford Contour or the Mercury Mystique so I will research them.
I downloaded the 30 sec vid from your first link so I could at least see the layout you are referring to in the text. Your second longer vid is downloading now but after 3 hour it is at the 40% point of the download, I will let it run over night.
I am a bit confused about several things you refer to in the above post.
1 - The pump you refer to as the "main circulator", Is this the green pump just below center on the left, or is this green pump the "shunt pump" you refer to later in the post? The green pump looks to me to be a hot water heating system circulation pump? You state that the main circulator pump draws liquid butane from the main reservoir, What type pump is it?
2 - What is heating your hot water and moving it through the heat exchangers?
3 - Compressor/turbine - You mention that it can handle 5 bar pressure without problems, it sure should, the compressor in the car can see pressures 2-3 times that amount in hot weather. just wondering what the "5 bar" number actually refers to.
4 - Condenser coil - You refer to the tubing as "micro bore" tubing but it looks like it has an outside diameter of something like 10 MM, what does "micro bore" refer to?
5 - What is the black reservoir looking device with electrical wires attached to it that is located directly below the compressor/turbine?
6 - Turbine inlet pressure - You indicate this to be 6 bar (as shown on the gauge in the vid), and you say you do not yet know the expander's exhaust pressure, but then you say the inlet pressure to the condenser is 5.5 bar, I would think the inlet pressure to the condenser would also be the pressure of the expander's output?
7 - 1/2 bar across the expander - not much pressure, only around 7 psi, somewhat surprised the expander turns at all at that low of a differential pressure, good to see that it does.
8 - The vapor table PDF is handy but unfortunately the temp/pressure table stops at 110 deg f (the web has tables that show hotter tems), I expect my propane unit to run much hotter than that as it will be located in HOT Arizona where the condensers will have to work with cooling air as hot as 120 deg. At the 120 deg condenser temp the pressure on the output of the expander and inlet to the condenser will be a bit higher than 200 PSI. The Arizona sun can easily produce temperatures hot enough to cause pressures well above 400 PSI but if this scroll compressor/expander will produce adequate torque at a far lower pressure differential it would be REAL nice. It is easy enough to control the input pressure by controlling the rate that hot water is fed to the evaporator.
The hot air temps are the reason I did the evaporative cooler (swamp cooler) temp tests that I described a few pages back in this discussion. I would rather not have to resort to that as it wasts electricity and water but I may have to use that to get the condensing temps down?
The 400 pound pressures I refered to in my propane condensing test setup were in outside temps of only about 80 deg f but the vapor supply and condensing tanks was being heated with direct sunlight and were hot enough I could not hold my hand on either of them for long.
Things have moved quickly over the last week so it is best that you just watch the most recent update video this will help avoid confusion, i have modified some pipework and layout from previous videos.
I will do my best to answer your questions,
1: The main circulator is a small 12v pump located at the bottom of the board it pulls butane from the main reservoir (black reservoir) at the bottom left. The green pump is a shunt pump to transfer liquid from the surge tank (yellow) under the condenser into the main reservoir. The green pump circulates through a double check valve before filling the main reservoir.
2:I have used a 2.2kW kettle to simulate the biomass boiler, this water is circulated by another domestic heating pump located under the turbine.
3: I have tested the compressor upto about 10 bar. It will run on a very small pressure differential as shown in my latest video, but with 0.5 bar differential the torque will be very low.
4: "Micro bore" is used in the UK to indicate a plumbing tube is smaller than 15mm (1/2")OD. 10mm and 8mm are the most widely used.
5: That is the boiler circulator. Domestic heating pump.
6: Unfortunately the condenser pressure is measured from the bottom of the 40 plate exchanger not the top, so i can't be sure what the turbine exhaust pressure is. In the latest video the turbine inlet is 4.5 bar and the condenser is 4 bar. I ran a seperate test to get pressure and temp measurements as per my last post.
7: It sure is good!
8: I am sure the scoll expander is the way forward, at least for myself and my project. It is so inexpensive that it makes the whole project achievable. I hope it can produce decent torque at low pressure drop. I don't want to exceed about 10 bar turbine inlet at the moment so that really limits how much pressure drop i can achieve, i am hoping for 5 bar pressure drop once i have replaced the condenser with a bigger one. But i may only get 1 or 2 bar drop, still this would be enough to start collecting some data.
Stu, I've studied the videos and re-read your system descriptions, but I'm still trying to understand the functions of some of the parts of your system, especially the "main circulator pump". Is it the pump that is intended to transfer the condensed butane from the low-pressure side of the system to the high pressure side, where it gets heated and vaporized? You describe is at a "domestic heating pump", which is an ambiguous description in my US-centric frame of reference. Is the main pump a positive displacement design, or a turbine/centrifugal design?
I did some rough calculations and your FPHX condensor seems sufficiently large, especially with the water temperatures given. It should be able to pull over 6kw of heat out of the condensing butane, and you're only putting in 2 kw, unless one of the pumps or some other device is adding a lot more.
If the turbine is receiving any condensed droplets from either the inlet or the outlet, it might struggle to ingest them. I'd be cautious about having the long vertical pipe on the outlet side for that reason. You have no "super-heat" HXC on the inlet side, so there is likely to be some condensation taking place in the inlet pipe, yet it seems unlikely to be drawn into the turbine by such low gas flow rates. More likely, any condensation in the inlet pipe simply runs back downhill into the boiler heat exchangers. The vertical feed pipe acts somewhat like a steam boiler "dephlegmator", allowing the liquid phase to return to the boiler, while the vapor phasee goes up the pipe. Unfortunately, this may also cool the supply vapor a little. Still, I don't imagine that would be a big loss, and doesn't explain the low performance by itself.
Is the scroll compressor designed to have some lubricant in the refrigerant? I don't recall reading if you'd added some sort of lube. It might require a lube in order to seal the small gaps in the design, and simply leaks a lot when there is no lube. I'm grasping at straws here. For that matter, I'm not sure a lubricant would travel with the vapor to the turbine from the boilers.
Is the hot water that feeds the vaporizers plumbed in a "counter-flow" direction, so that the hottest vaporizer is the last one before the vapor goes to the turbine?
That's it for now. I think this is a worth-while project, and I'm anxious to see it succeed.
In the second longer video I could see the name "DAB" on the rear of the green pump, did a web search for that manufacturer and found what lookes like the same model pump, if so, it is a hot water circulation pump. The max pressure spec on the one I looked at is 10 bar (roughly 150 pounds), other manufacturer of hot water circulation pumps show a max pressure of 125 pounds, this seems normal for houshold water systems, the blue Omnifilter water filter housing I use for filtering are also speced for up to 125 pounds pressures.
A centrifugal pump is not likely to make more than about 50 pounds pressure max so I assume these oumps are working in Stu's setup because it is running no more than about 65 pounds max pressures now. I will not be able to use these type pumps in my higher pressure propane system, bummer.
During the web search I ran into another PDF research paper of interest, it is comparing 3 different frig fluids for pressure and they also did condensor testing, one fluid tested is propane (R290 refrigerant). The paper has lots of good info describing the temps and pressures developed in different air cooled condensors as well as detailed info on size and tubing configurations used for the condensors. This paper describes a refrigeration system but the info applies to an ORC system just as well.
Johno: The "main circulator" is the pump which transfers liquid from the main reservoir into the vapouriser. In my system the Main circulator is a centrifugal, 12Volt, 6 or 7Watt, 2 meter head pump. My biggest design criteria was building a system which did not require a huge pump to feed the vapouriser. I pondered over it for a long time but eventually came up with the answer: Pressure equalisation. In the end my butane circuit will hopefully run without a pump similar to this:
I bought a new FPHX due to the other one being so restrictive that i could only get 2 L/Min through it. I measured it into a jug, so the estimate 4-5 L/min in one of my older posts is incorrect. The new HX will allow up to 30 L/min through estimated, i will measure it properly when i get time. The condenser is piped in counter flow.
My thinking is: the condenser needs to be as big as possible to pull as much heat out as possible in order to create the highest pressure differential. The lower the temp in the condenser the lower the pressure, therefore, a bigger the pressure ratio across the expander and greater output power. The heat removed could then be reintroduced in a recuperator.
The vertical pipe rising out of the turbine is the first thing i would change if i could!. The horizontal pipe has a slight fall to the condenser and that's all i could do with the layout as it is. I will insulate the vertical section to try to prevent condensation.
Turbine is lubed by a couple of squirts of engine oil which travels round with the butane.
The 5 vapourisers are piped in parallel and balanced so that they are of equal temperatures. The hot water feed is not piped counter flow at the moment.
Thanks for your help Johno.
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