Answer
It is valid.
Work Step by Step
For the isentropic process:
$T_{2s}=T_1\left(\dfrac{P_2}{P_1}\right)^{(k-1)/k}$
Given $T_1=573\ K,\ P_2=100\ kPa,\ P_1=1200\ kPa,\ k=1.395$:
$T_{2s}=283.5\ K$
From the energy balance:
$\dot{W}_s=-\dot{m}\Delta h = -\dot{m}c_p(T_{2s}-T_1)$
With $\dot{m}=1\ kg/s,\ c_p=1.013\ kJ/kg.K$
$\dot{W}_s=293\ kW$
Since this is greater than the power claimed by the inventor, the claim is valid.
