4. Heat input during expansion

As the technical work required for compression is minimized when the compression is cooled, the technical work "recovered" on the shaft of an expansion machine is greater (in modulus) when heat is added during expansion [equations (25) ] in order to approach isothermal expansion. But heat input has a cost, directly linked to the amount of energy input, which cooling does not. As a result, isothermal expansion is not necessarily envisaged, but more generally adiabatic expansion. However, for certain applications, this isothermal expansion or, at the very least, this heated expansion is envisaged. These are applications where heat is involved in the overall system....