$B$	Heat transfer loss coefficient (W/K)
$C_v$	Specific heat at constant volume (J/(mol·K))
$E$	Ecological function (W/K)
$k$	Adiabatic index (-)
$\dot{m}$	Molar flow rate (mol/s)
$P$	Power output (W)
$P_d$	Power density (W/m3)
$\dot{Q}$	Heat transfer rate (W)
$R$	Gas constant (J/mol/K)
$T$	Temperature (K)
Greek symbols
$\gamma$	Compression ratio (-)
$\eta$	Thermal efficiency (-)
${\eta }_c$	Compression efficiency (-)
${\eta }_e$	Expansion efficiency (-)
$\mu$	Friction loss coefficient (kg/s)
$\sigma$	Entropy generation rate (W/K)
$\rho$	Pre-expansion ratio (-)
$\tau$	Temperature ratio (-)
Subscripts
$in$	Input
$leak$	Heat leak
$out$	Output
$max$	Maximum value
$P$	Max power output condition
$\eta$	Max thermal efficiency condition
$P_d$	Max power density condition
$E$	Max ecological function
$1-5$	State points
Superscripts
$-$	Dimensionless
Abbreviations
DI	Deviation index
FL	Friction loss
FTT	Finite time thermodynamics
HTL	Heat transfer loss
IIL	Internal irreversibility loss
MOO	Multi-objective optimization
OO	Optimization objective
PM	Porous medium
SH	Specific heats
WF	Working fluid