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A month has transpired since I posted this question and I determined that I am limited in possible expansion due to mechanical reasons. I am now going to put two of the same expanders in series with the second one running twice as fast as the primary. They will be coupled via belt. This should...

I'll let you know what happens. I still have to build the motor, feedwater preheat & condenser circuit before I can run the R134a. Thanks!

I can insulate the downcomer, I guess I'll have to wait and see about the instability. Exactly what happens with parallel instability? symptoms? I think the heat transfer surface far exceeds my demand (over 15 sq feet in the 3 coils alone) Perhaps this lower demand allows slower flow and...

Indeed, I have 3 parallel (1/4" Cu x 60 ft) coils connected from the bottom to the middle of a 1-1/4 ss pipe with caps. At the top of the pipe it goes to a 3/8 x 15ft Cu superheater coil (through the hottest layer of water), then to the outside world. The feed"water" enters at the...

Unfortunately, the heat source is quite variable (solar/wood) The only modulation is the fact that the water storage mass is large. I commited to a coil design that has a large pipe that will behave like a downcomer. I might be able to place some sort of level sensor in it's wall and maintain...

How can I calculate the pressures encountered above the critical temp? All my refs stop at 213F for R134a refrigerant.

Are these the same pelton wheels used in hydro power? If so, are they as efficient with a vapor as liquid?

Would this reheated gas go through another expander downstream of the first? Would it have to be a higher displacement unit as to match torque and/or speed of primary expander so they could be coupled together on the load?

davefitz I wont nearly have those expansion ratios. I'm hoping that since I am using a positive displacement rotary expander, I'll be able to capture most of the pressure gradient energy between boiler and condenser (~500psi) As long as I dump the excess heat exiting the motor. One dump would be...

To all respondants: Thank you for your valuable inputs. I now have a better understanding of a portion of an area of knowledge I must utilize in my project. Now that your here, I have another question I need to know about. I am constructing a small electric generating solar/solid fuel system...

25362 Yes, you are correct about lack of experience with steam or rankine. My project requires some knowledge in this area, hence the post for basic answers. Thanks for taking the time to explain my query. It gave me some real information to ponder in my design. Bob

25362 The danger, in my mind, is only the product of the unknown (to me) concerning super critical fluid/vapor state. I'm just being cautious.(see generalblr's response above) Does superheat mean heat added above the critical point? Is there a system advantage to add heat above the critical...

Ah ha,...I see. Do you know if the super critical working fluid/gas is usable in a closed Rankine cycle heat engine scheme? I just need to know if I can increase highside pressure for more power or is this not advised or dangerous? Thanks for the response. Bob

Would the pressure continue to rise if you applied more heat after the critical point? Or, is there a cap on pressure generated? Thanks

What exactly happens if you heat a given working fluid above its critical temp? Does the pressure stop rising? Is there any benefit in a closed heat engine system to do so? I am working with R134a for a working fluid Thanks

Thanks for the great resource, it is bookmarked. Actually I'm still fumbling with the theory and math. What I eventually want to know is how much work can I expect from R134a for a given heat input. I am utilizing the refrigerant in a heat engine loop instead of steam. If I could compare with...

What is the gas constant # for R134a refrigerant vapor @ 180 degrees F? Thanks

I am considering using an a/c rotary vane compressor as an expander in a solar generating project. The working fluid is R134a refrigerant. From volume measurements I've determined it takes a 12cc space to a 36cc space before dumping, or 1:3. From what I've heard it should be more like 1:9. I've...

I am constructing a hybrid solar/ solid fuel generator system. An insulated water tank will evaporate R134a, in a coil(s) configuration,always below the boiling point of water open to the atmosphere for safetys sake. The vapor will drive one or more rotary vane a/c compressors modified as...

I am constructing a hybrid solar/ solid fuel generator system. An insulated water tank will evaporate R134a, in a coil(s) configuration,always below the boiling point of water open to the atmosphere for safetys sake. The vapor will drive one or more rotary vane a/c compressors modified as...