Hey guys, I'm looking at designing a heat pump system that uses CO2 as the working fluid. I'm not exactly sure how to pick the components that I need like a compressor, expansion valve, etc. Im trying to create an experimental device that will work in conjunction with my CO2 thermosyphon to take heat from low temperature sources. Is there a design guide? Does anyone know of a manufacturer of such components or prebuilt assemblies? Your help is greatly appreciated!