Wow, I just joined, and its amazing how this very subject is exactly what Ive been researching. I must say, though the concept of these forums is a good one, how great would a real life sit down be in a think tank of all the talent apparent here.

Ill only comment briefly and also poss a question to you all.
RColitos: As I have gathered by your post you have also found it difficult to locate a smaller version of a, true "Turbo-Expander" for your application so you turned to manipulating a scroll type compressor. I also had contacted some companies who manufacture turbo-expanders for much larger, mega watt outputs, and they had even conceded to funding R&D for smaller units in the capacity your working on but had to pull the plug do to economy backslide. They even mentioned the refrigerants you referring too. This ones exciting, I hope to hear more see where this one gos..

Heres an idea. If your looking to figure what your required flow rate, volume and pressure needs to be to meet the required torque, rpm, etc., of the turbine for your generator, why not hook up a decent sized air compressor, and tweak the pressures and volume along with any other parameters you need to meet to get a range you know your refrigerant will need to achieve.