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2KW low temp Rankine cycle electricity and cooling
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Hi Tim, all the pumps (except the 12v centrifugal main circulator) are 240V 5 meter head centrifugal type for domestic heating. They are cheap and easy to come by.

I did some more tests today (once rain eased off) and managed to get the turbine really whizzing round, but again only for short bursts. My pressure balancing/equalising tube works very well, by equalising the pressure to the main reservoir it forces the liquid under gravity into the vapouriser. The tube does not seem to divert too much of the vapour away from the turbine as once the pressure is balanced all the vapour heads in the direction of the condenser. The problem with the equaliser is that it creates a high pressure in the main reservoir which means the surge tank cannot empty into it, thus breaking the cycle. The main reservoir then has to cool down until it is equal to the surge tank temp and pressure at which point the DAB shunt pump can move the liquid and another power cycle can begin.

What my system needs now is 2 operating reservoirs fed from one surge tank with a non return valve between them. Each of these operating reservoirs would require a means of cooling and solenoid valves to control the flow. As one of the operating reservoirs is feeding the vapouriser the other would be cooled to receive liquid from the surge tank. Once it is full and the other is empty the solenoid valves divert the flow so that it feeds the vapouriser and the other cools and fills, so on and so forth.

I have drawn this system out and it seems to be fairly simple.

I reckon this is the way you should go Tim instead of trying to find big hefty pumps which will cope with the high pressures you intend to run.

Hope that description makes some sense.

Stu.
 
Registered: October 30, 2010Reply With QuoteReport This Post
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I am confused - If you equalize the pressure between the low pressure side fluid collection reservour and the high pressure side vaporizer I understand how gravity could move the fluid between them (thought there was a couple of check velves in this area someplace that woild imped the flow a good bit?, or are these bypassed or replaced by a solenoid isolation valve or something?) but there won't be any pressure across the expander.

The Matteran system uses isolation valves before and after the collection tank, as well as moving cool, then hot, water around the outside of the same collection tank. They first condense the vapor from the expander into liquid, then heat the tank to produce higher pressure vapor above the liquid and use the vapor pressure, along with gravity, to push the bottom liquid back in to the boiler. A lot of valve switching and water pumping goin on there. They claim it uses less energy than simply running one small high pressure liquid pump after a condenser but it sure seems like a long way to go to save just a few watts of power.

Pump - The problem that I am concerned about is the overall max pressure specs that I am seeing for the centrifugal water circulation pumps, the DAB pump in your system seems to have a max pressure spec of 10 bar, just a bit under 150 psi. From the vapor pressure tables for propane I expect the pressure even on the low pressure side (condenser side) of a propane system will be around 200 PSI. Small hydraulic gear pumps with high pressure specs are available for well under $100.00 U.S., even the cheapest of these are designed to work with pressures up to 1500 pounds, most are specked at up to 3000 pounds pressure.

Surpluscenter.com has a new small aluminum bodied hydraulic pump specked to move .o7 cubic inch of fluid per revolution that sells for $79.00. They occasionally have other surplus pumps even cheaper, I bought a new .05 CI/Rev hydraulic pump for $49.95 in the past. That pump is basically a 3 inch cube of cast iron. These low volume pumps have relatively small gears, something like 3/8 to 1/2 inch diameter, so are easy to turn using something like an Ebay 12-24 volt DC salvaged sidewalk scooter motor costing around $25.00. Being a DC motor it will be easy to control the speed/flow of the liquid through the pump.

This type of pump should allow me to draw liquid propane directly from the bottom of the condenser and inject it into what ever I end up using as a vaporizer. Being able to control the flow of both the externally heated fluid used to heat the boiler, as well as the flow of the frig fluid into the boiler, should allow very precise regulation of the overall power output of the system. This should make it reasonably doable to automate the system using a pretty simple microprocessor based control circuit to adjust the speed of the pumps as the electrical load changes.

Using a speed controllable gear pump on the output of the condenser should also allow me to draw the pressure on that side way down, due to pump suction, if need be. lowering the pressure on the condenser side of the system at the same time the pump moves the max amount of condensed frig fluid back into the boiler, along with cranking up the hot water pump to flow the max amount of hot water to the boiler, should allow max power from the expander.

Reflecting on your reference to having your condenser pressure gauge located on the output of the condenser - Unless you have a HIGHLY restrictive condenser it should not make much difference where the gauge is located as long as it is someplace on the low pressure side of the system. Your low pressure gauge reads about 6 pounds lower than the high pressure side gauge even though it is on the output of the condenser, if the pressure on the input to the condenser was even higher (due to flow restrictions inside the condenser) it would indicate that the expander was running on even LESS differential pressure than the 6 pounds indicated, hard to think it could run at that low a differential pressure and still overcome even the friction losses of the seals and bearings. The DENSITY of the fluid in the condenser will be different from the input to the output (light vapor in, heavy liquid out) but it sure seems that the pressure should be almost the same anyplace on the condenser side of the system.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Hi everyone, it's my first post in this forum. I'm sorry to interfere your interesting discussion.

I've begun a thesis regarding the design and building of a ORC.
The fluid has already been chosen: R236fa.
Some components of the plant (regenerator, condenser, pump) have been dimensioned as well.

I am going to use a car air con scroll compressor used as an expander, the idea is to look for it in a car wrecker. Unfortunately, I haven't found any specifications about the scroll compressors used in this field on the internet (apart from Copeland scroll compressors for buildings air conditioning).

Firstly, do you have any suggestion about guidelines/books/manuals which teach how to build a rankine plant? Overall building, framework, pipelines design, connections...

Thank you very much for the help!
 
Registered: October 05, 2011Reply With QuoteReport This Post
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Hi driver78

The best info i found for ORC is at: http://organicrankine.com/?pag...c_theory#top_of_page

and a few good papers circulating the web like :

http://www.labothap.ulg.ac.be/...inS/TFE_SQ010607.pdf

If you dig deeper you will find the later updates to this study, although i expect you have probably seen them already.

Tim,

It will hopefully not divert too much of the vapour once the pressure has equalised, initially it will take some flow to raise the pressure in the reservoir but once pressure is stable the vapor will try to force its way to the lower pressure in the condenser via turbine. If the reservoir is almost full then there will only be a small volume of vapour required to raise the pressure, as the reservoir empties through the pump the equaliser tube will add more vapour but the path of least resistance will still be through the turbine to get to the condenser?

If i have 2 operating reservoirs then solenoid valves can isolate the equalising flow of high pressure vapour so that one can fill while the other empties.

I would also need 2 solenoid valves to control the flow of cooling water so that only the one that is filling receives coolant.

The total power consumption of 4 solenoid valves is 40 to 50 Watts although i have seen valves which consume as little as 5W each. The high pressure pump for the system linked to in the above paper draws up to 550 Watts which has a huge impact on their system's net output. The question is whether the vapour flow lost during the equalisation process would have as big a negative impact on power, if so it is obviously pointless, to answer it i will just have to give it a try.

My latest update video shows my system running using the pumps to circulate butane with the equalising tubes isolated. I have experimented running the system without the pumps by opening the equaliser tube, this works quite well but without a second reservoir i cannot achieve a continuous cycle yet.

If used along with the low power feed pump the equalising tube fitted to my current prototype massively increases the power output at the turbine because it makes it easy for the pump to feed the vapouriser (boiler) which increases the flow rate of the liquid. The operating reservoir is separated from the surge tank using a check valve, so as the equaliser opens the flow cannot short circuit through the surge tank into the condenser but the equaliser itself does not have a check valve. The surge tank can still receive liquid from the condenser even though the pressure in the lower operating reservoir is high, so all i need to do is add another operating reservoir and i can run a continuous cycle by alternating the flow between the two.

I had no idea high pressure pumps were so cheap, thanks for that website address.
 
Registered: October 30, 2010Reply With QuoteReport This Post
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Thank you very much for the help. The links are very helpful, although unfortunately there aren't recommendations regarding how to build the plant piping and framework.

My question is now more specific: I have found out that the car conditioning scroll compressors rotate thanks to the belt linked to the car engine driving shaft. In my case it would be more useful and opportune a scroll compressor/expander straight connected to the electric motor. Do you have any suggestions, especially regarding where can I find it? I've thought about residential conditioning plants, or big-sized coaches/trains air con...

Thank you.
 
Registered: October 05, 2011Reply With QuoteReport This Post
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driver,
You may want to consider removing the pulley and clutch from an automotive compressor, rather than buying one for some other application. It will almost certainly be less expensive if you use parts from a wrecking yard. If you're in the US, then identifying a make and model that uses a scroll compressor may be difficult, but if you do, please let us know.
Cheers,
JohnO
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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Hi everyone,

Unfortunately I'm not in the US, I'm in Italy... (but I'm going to come to the US soon!).

I went to an Alfa Romeo car repair shop this morning. Since I know the shop's owner he gave me for free this:

http://www.sanden.com.sg/openc...Product.jsp?pid=1005

which is a fixed displacement compressor.

Is it possible in your opinion to use it as an expander? After that, I think that I could use a pulley to make a shaft rotate through a fly-wheel, and put the electric motor at the opposite side of this shaft.

JohnO, with "automotive compressor" do you mean the volumetric compressor of a engine with turbo or the A/C compressor??

Thank you very much.
 
Registered: October 05, 2011Reply With QuoteReport This Post
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Driver78,

I think the compressor you have will be difficult to use, being a piston type. If you go to a scrap yard and look for a car air con compressor that has the inlet and outlet side by side down the length of the body instead of side by side at the top like yours then there is a good chance it is a scroll type.

If you can't find one in Italy then buy one of these:

http://www.ebay.co.uk/itm/FORD...d0fbc7#ht_2021wt_952

It definitely has a scroll as its the same type i use.

If you have any problems, email me (stustu41@yahoo.com) and i will ship one to you, same goes if anyone else who wants one.

As Johno said you could then directly couple it to a motor shaft. However, i would leave the pulley attached because it acts as a fly wheel??, the clutch automatically disengages if you remove the power source, so that won't be a problem.

I would build the piping using copper tube and silver solder/brazing for the high pressure side, copper with standard plumbing solder is adequate for the low pressure side. If you have steel tubing you could use threaded fittings and lock tight 55.
 
Registered: October 30, 2010Reply With QuoteReport This Post
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Driver - Back up and read the last 2-3 pages of this discussion,

By following the links in Driver's SANDEN link (above) I got to a Sanden Scroll Compressor page indicating they have 4 models of auto frig compressors that ARE scroll type. will try to find specs on these as I have found Sanden compressors in scrap yards here in the U.S.

I dropped by my local salvage yard today and copied down part numbers from some of the auto frig compressors they have, just getting started researching if any of these are scroll types?

STU - It will be interesting to see how your duel collection tank idea works out. I will start by using a high pressure liquid pump between thew bottom of the condenser and the boiler, at least I will be able to get some real figures on the amount of power such a pump requires. I will be real happy if the basic system actually works even if at a power LOSS at first.

Your success so far has convinced me that a scroll compressor is worth trying, it is so much simpler than all the flow valving and control needed to put pressure pulses into a piston expander.

The salvage yard had a nice BIG liquid-to-air condenser. About one foot square and 4 ft long with something like 3/4 inch tubing, problem is it is all Aluminum, not sure if the aluminum tubing will
survive at 400 pounds pressure, have to do a bit more rading on this.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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This links to an university research paper that has a nice description of the testing of a Sanded TRS90 scroll compressor being used as an expander. They used compressed air for the testing but show how one can measure the power out of the expander in a practical way. The Expander testing starts on page 46.

Ebay has several Sanden TRS90 compressors listed but even the used ones start at around $150.00.

One sale gives the following list of vehicles that the compressor was used on.
-----------------------
95 96 97 98 99 00 CHRYSLER CIRRUS 2.0L 2.4L 2.5L (ALL)

96 97 98 99 00 01 02 03 CHRYSLER SEBRING 2.4L & 2.7L CONVERTIBLE AND SEDAN ONLY TO PRODUCTION DATE 7/21/03

96 97 98 99 00 CHRYSLER SEBRING 2.5L CONVERTIBLE ONLY

95 96 97 98 99 00 DODGE STRATUS 2.0L 2.4L & 2.5L (ALL)

01 02 03 DODGE STRATUS 2.4L & 2.7L SEDAN AND CONVERTIBLE ONLY TO PRODUCTION DATE 7/21/03

96 97 98 99 00 PLYMOUTH BREEZE 2.0L 2.4L (ALL)
________________________________
More vehicle -

1996 Honda Prelude S Coupe 2-Door 2.2L 2156CC l4 GAS SOHC Naturally Aspirated
1996 Honda Prelude Si Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1996 Honda Prelude VTEC Coupe 2-Door 2.2L 2156CC l4 GAS DOHC Naturally Aspirated
1995 Honda Prelude S Coupe 2-Door 2.2L 2156CC l4 GAS SOHC Naturally Aspirated
1995 Honda Prelude SE Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1995 Honda Prelude Si Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1995 Honda Prelude VTEC Coupe 2-Door 2.2L 2156CC l4 GAS DOHC Naturally Aspirated
1994 Honda Prelude S Coupe 2-Door 2.2L 2156CC l4 GAS SOHC Naturally Aspirated
1994 Honda Prelude Si 4WS Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1994 Honda Prelude Si Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1994 Honda Prelude VTEC Coupe 2-Door 2.2L 2156CC l4 GAS DOHC Naturally Aspirated
1993 Honda Civic del Sol Si Coupe 2-Door 1.6L 1590CC 97Cu. In. l4 GAS SOHC Naturally Aspirated
1993 Honda Prelude S Coupe 2-Door 2.2L 2156CC l4 GAS SOHC Naturally Aspirated
1993 Honda Prelude Si 4WS Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1993 Honda Prelude Si Coupe 2-Door 2.3L 2259CC l4 GAS DOHC Naturally Aspirated
1993 Honda Prelude VTEC Coupe 2-Door 2.2L 2156CC l4 GAS DOHC Naturally Aspirated
1993 Hyundai Elantra Base Sedan 4-Door 1.6L 1596CC l4 GAS DOHC Naturally Aspirated
1993 Hyundai Elantra GL Sedan 4-Door 1.6L 1596CC l4 GAS DOHC Naturally Aspirated
1993 Hyundai Elantra GLS Sedan 4-Door 1.8L 1836CC l4 GAS DOHC Naturally Aspirated
1992 Honda Prelude S Coupe 2-Door 2.2L 2156CC l4 GAS SOHC Naturally Aspirated
1992 Hyundai Elantra Base Sedan 4-Door 1.6L 1596CC l4 GAS DOHC Naturally Aspirated
1992 Hyundai Elantra GL Sedan 4-Door 1.6L 1596CC l4 GAS DOHC Naturally Aspirated
1992 Hyundai Elantra GLS Sedan 4-Door 1.6L 1596CC l4 GAS DOHC Naturally Aspirated

This is a picture of the Sanden TRS90 compressor from the Ebay sale.

This message has been edited. Last edited by: Tim c cook,

ImageSanden_TRS90_compressor_pic.jpg (10 Kb, 7 downloads)
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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The Sanden TRS105 looks to not be used in as meany vehicles as the TRS90?

One Ebay listing is for this vehicle - OEM AC COMPRESSOR MERCEDES SL500 1999-2002

This is a picture of the Sanden TRS105 compressor.

ImageSanden_TRS105_compressor_pic.jpg (13 Kb, 4 downloads)
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post



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This links to "heat engine" web page that has more links to info for scroll expanders as well as another list of vehicles.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Hello everyone,

Finally I found another compressor at a car wrecker: Sanden TRV090. I can't find on the internet which is the difference between the TRS model (Scroll one) and this one.

After that I have to find the check valve (I hope it's the correct term) and remove it...
I'll get you up-to-date!!

Thank you.



EDIT:

The Sanden TRV090 is an evolution of the Sanden TRS which is a scroll expander, but it's different in fact I found that it's a "variable displacement type". I would have liked to investigate but I couldn't open it due to the return policy of the car wrecker. So I gave them back the TRV and I found at the end the Denso SC08, which is a scroll compressor for air con in some cars, as you may read at page 9 of this:

http://napabeltshose.com/file_...ntals_1-Basic_AC.pdf

In another forum I read that someone managed to build a ORC using this scroll compressor, through the removal of the check valve.

This message has been edited. Last edited by: driver78,
 
Registered: October 05, 2011Reply With QuoteReport This Post
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I did a web search for Sanden TRV090 and found THIS discussion (and over 6000 more hits) concerning replacement of the control valve on a Sanden TRV090 compressor. The discussion indicates that this is another PISTON type compressor and not a scroll. I suspect the "V" in TRV indicates a "veriable" type compressor, these will likely all be piston type compressors. I also suspect the "S" in TRS indicates a "scroll" type compressor.

Sometimes you have to look at a lot of web pages that don't seem to directly apply to the question but they may lead to an answer.

STU - I went back and treeked the brightness of the ebay sale photo of the Euro Ford compressor that you linked to earler in this discussion. I thought the metal tab near the rear might be some sort of control lever (didn't seem like a scroll compressor should be lever controlled?). The tweeked photo shows that is is a hold-down tab for something electrical, do you know if this is a Pressure sensor or a temperature sensor?

This is the tweeked picture.

Imagetweeked_picture_of_European_Ford_compressor_showing_tab_holding_something_electrical.jpg (11 Kb, 12 downloads)
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Tim: you are correct, The metal tab is for some type of sensor, probably controlling clutch engagement. I cut straight through the wire with my snips and have never regretted it, it seems to seal fine so i just left the sensor alone, of course if it were to be removed you could maybe put another type of sensor in.

The position of the ports is all important in determining whether a second hand unit is a scroll or piston (over/under or side by side). The ports on this model have green seals which seem to do the job. I just fabricated a piece of steel bar to sit flat on the seals, then silver soldered my fitting onto the bar. I may go back and drill out the exhaust port to enlarge it.
 
Registered: October 30, 2010Reply With QuoteReport This Post
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WOW - I don't understand why I didn't use Ebay as my search source for auto scroll frig compressors before this. This links to an Ebay search for "ford scroll compressor", it found 72 hits for MANY different U.S. Ford model vehicles. The pictures seem to show basically two different style compressors? Unfortunately the sale pages simply say the compressors are "Ford scroll' compressors, and each one seems to have a different part number? I will have to research these more.

Another web search found THIS PDF catalog for DENSO compressors and parts. I have not yet read through it.
 
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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Tim c cook: I have read through your PDF link and I have looked for Denso SC08 specifications, drafts, exploded models, but there are few things online. I have phoned to Denso and they weren't.... as if to say... pleasant. They didn't want to help me.
In the next days I'm going to open the compressor so as to find out and remove the check valve and then put inside it a 8 bar compressed air to check if it's working correctly. In the meantime I keep on learning a engineering software called Aspen, through which I may make a simulation of the whole organic Rankine cycle.

If someone of you is interested, I'll translate for you the advices and suggestions given in a engineer's community Italian forum, in which a guy 6 years ago managed to build a ORC using a Denso SC08 scroll compressor converted to expander and seed oil as working fluid.
 
Registered: October 05, 2011Reply With QuoteReport This Post
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Tim, et al: one reason to be cautious searching for "scroll" in ebay is evident in the listings shown - almost all of them contain the words "scroll down", not "scroll compressor". Some actually DO refer to scroll compressors though, but you need to pay attention.

Good stuff - there ARE scroll compressors in US wrecking yards. I also see that a Google search turns up lots of discussions about worn out scroll compressors, so remember - the one you find in a wrecking yard may be worn out and not perform like you expect. If everything else seems like it ought to be ok in a test, but the expander doesn't make as much power as expected, then include a worn-out scroll expander as a potential cause.
Cheers,
JohnO
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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Hi everyone,

I've got an important question for you.

I have removed the check valve, and after disassembled, cleaned, lubricated and reassembled again the compressor. But I've noticed that when I tighten all the screws, the clutch (connected to the shaft) doesn't move and then the orbiting scroll. I've seen that the orbiting scroll is blocked by the compressor covering itself. So I've thought that probably I need to engage the clutch by exciting it through direct current. In this way the shaft displaces and then the orbiting scroll's movement is allowed. Is it correct?
 
Registered: October 05, 2011Reply With QuoteReport This Post
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Hi guys, i reconfigured the layout of my system slightly and have been doing some power tests on my system.

Video Link:

http://www.youtube.com/user/DoLpH1983?feature=mhee

The test shows the use of the equalising tube.

The test was run with a boiler flow temp of 78-80 Degrees Celsius.
The max output power of the generator was 67 Watts (7.34 Volts, 0.8 Ohms, 9.17 Amps), the generator is 50% efficient so i calculated the turbine shaft power as 135 Watts not taking into consideration any losses in the drive belt (elastic band!).

During the test the flow temperature dropped about 8 degrees C so the boiler is too small to deliver enough heat, I was hoping to be able to get an efficiency calculation but without a stable temperature i can't so i did some guess work.

I took a guess that doubling the output of the boiler to 4kW might be enough to keep a constant delivery of water at 80 Degrees C. I then theoretically calculated the efficiency (from 4kW input) as being 3.5% thermal heat to mechanical shaft power, however the boiler may need to be bigger than 4kW so this 3.5% is really just guess work.

Will try to get some decent calculations done soon, i will use the equation:

Energy = Mass Flow Rate x Specific Heat Capacity x Delta Temperature (kelvin)
Q = M x Cp x Delta T

To work out how much heat energy (Q) is being added to the butane circuit while the turbine is at max output. Before i can do this i will need to get two digital thermometers to give a measurement of the temperature drop across the vapouriser.

This way i will know exactly how much heat is being introduced into the butane circuit and therefore i can accurately calculate the efficiency of the turbine.

If someone knows an easier way then i'm all ears of course.
 
Registered: October 30, 2010Reply With QuoteReport This Post
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