3 ms·
I guess here we want a fluid with high heat capacity, but which can perform well under lower pressure than an equivalent amount of steam. Good candidates are su
by iwwr 5y ago
I guess here we want a fluid with high heat capacity, but which can perform well under lower pressure than an equivalent amount of steam. Good candidates are substances with low mollecular weights and which don't react with the pipes and turbine materials. Alternatives here can be helium or argon etc, but CO2 is far cheaper.
Supercritical CO2 or helium also perform better when the heat source is hotter, which is suitable for the Brayton cycle. It's also why they are frequently mentioned when talking about high temperature next-gen nuclear, or concentrated solar.
- darksaints 5y agoThe operating pressures here are actually much higher than steam. Supercritical fluids are extremely interesting because they have some helpful characteristics of liquids, like density, and some helpful characteristics of gasses, like heat expansion. For this reason, supercritical fluids in general are the subject of a lot of heat engine research. I believe supercritical CO2 comes to the table because it becomes supercritical at a low enough temperature and pressure that it won't take major breakthroughs in materials science in order to build a heat engine with it.