Method and apparatus for a rotary thermodynamic cycle with substantially isobaric fluid admission

A method of operating a thermodynamic apparatus configured as a heat engine or heat pump,

• the thermodynamic apparatus comprising a rotatable shaft on which a rotatable piston is provided, the piston extending through an expansion chamber to define an expansion sub-chamber, wherein rotation of the shaft rotates the piston relative to the expansion chamber to change the volume of the expansion sub-chamber;
• the thermodynamic apparatus comprising, in flow series, a first heat exchanger, the expansion sub-chamber and a second heat exchanger, the method comprising transferring fluid from the first heat exchanger to the second heat exchanger via the expansion sub-chamber by rotating the shaft and the piston;
• aligning an expansion chamber inlet port with the expansion sub-chamber and admitting a fluid flow at an intake pressure from the first heat exchanger into the expansion sub-chamber by increasing the volume of the expansion sub-chamber;
• closing the expansion chamber inlet port and fluidically isolating the fluid within the expansion sub-chamber from the first heat exchanger;
• expanding the fluid within the expansion sub-chamber by further increasing the volume of the expansion sub-chamber to reduce the pressure of the fluid from the intake pressure;
• aligning an expansion chamber outlet port with the expansion sub-chamber and fluidically coupling the expansion sub-chamber to the second heat exchanger;
• and
• transferring fluid out of the expansion sub-chamber to the second heat exchanger by reducing the volume of the expansion sub-chamber,
• wherein the process of admitting a fluid flow at an intake pressure from the first heat exchanger into the expansion sub-chamber is substantially isobaric;
• wherein the thermodynamic apparatus comprises a compression sub-chamber that operates in anti-phase with the expansion sub-chamber.