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Here is the first post regarding an old idea lying in the drawer for several years: Small sized Organic Rankine Cycle Heat Motor. Project name is Thermodyna. Step by step we will publish the latest results regarding 1. cycle configuration, 3. working fluid, 4. generator… Today we start with the logical number 2, the expander.

How much mechanical energy, i.e. exergy could one extract from a gaseous, pressurized  fluid at a pressure P1 and temperature T1 when it expands in an adequate engine?

All kind of Rankine or steam engines need a suitable fluid, that reacts to heating with an increase in pressure. The increased pressure of the fluid will be used to drive a piston, a turbine blade, lift a mass … and generate power. In this sense the fluid can be called “power fluid”. The following charts show graphs of the vapor pressure (bar) versus the temperatures (°C) for several fluids. The second chart uses a logarithmic vertical axis.