Ideal expansion for heat engine?
Ideal expansion for heat engine?
(OP)
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 considered using a smaller and larger unit in a compound configuration or installing a cutoff device at the inlet. My questions are:
1) What is the ideal expansion ratio for efficiency regardless of resulting power/speed output?
2) What is the correct sizing steps for double and triple compound expansion?
3) Does throttling behave in any way like the results from a admission percentage cutoff device?
Thanks
1) What is the ideal expansion ratio for efficiency regardless of resulting power/speed output?
2) What is the correct sizing steps for double and triple compound expansion?
3) Does throttling behave in any way like the results from a admission percentage cutoff device?
Thanks





RE: Ideal expansion for heat engine?
If the working fluid is always gaseous, then you expand to the lowest achievable temperature (usually ambient conditions). Ideal efficiencies are constrained by the high temp and low temp reserviors for any heat engine--review Carnot. Your situation almost seems like a Brayton cycle, but I would have to crack open a book to know for sure.
RE: Ideal expansion for heat engine?
Thanks for your response.
RE: Ideal expansion for heat engine?
In steam cycles (Rankine) they caution against forming excessive liquid droplets prior to turbine exit. The droplets can lead to erosion of turbine blades. I don't know if this would be a problem for your application.
I am glad I found your question, because I need the review as well. I may not have the right cycle, but the expansion process sounds about right for your application.