A	heat transfer area, [m2]
COP	coefficient of performance, [-]
CTQgen	generalized number of heat transfer units, [-]
f, g	functions defined in the model
Kgen	generalized conductance, [W K−n]
$\dot{m}{c}_p$	heat rate capacity, [W K−1]
n	exponent of the heat transfer law, [-]
$\dot{Q}$	heat transfer rate, [W]
$\tilde{q}$	dimensionless heat transfer rate, [-]
$\dot{S}$	entropy production, [W K−1]
$\tilde{s}$	dimensionless entropy production, [-]
T	temperature, [K]
U	overall heat transfer coefficient, [W m−2 K−1]
$\dot{W}$	mechanical power, [W]
w̃	dimensionless mechanical power, [-]
Greek Symbols
λ	Lagrange multiplier
θ	non-dimensional temperature
ξ	function defined in the model
Subscript
gen	generalized
H	working fluid, at the machine hot temperature side
HS	source, at the machine hot temperature side
i	internal
L	working fluid, at the machine low temperature side
LS	source, at the machine low temperature side
T	total
Abbreviations
C	constraint
FO	objective function
L	Lagrangian function