Hi Julian,
I tried the following with the first case in your file:
On the System Design page:
Design point DNI = 850 W/m2
Target solar multiple = 2
On the Solar Field page:
Header design min flow velocity = 2 m/s (cold and hot headers)
Header design max flow velocity = 3 m/s (cold and hot headers)
Then, on the Parametrics page, I tried a range of target solar multiple values between 2 and 3 with the following results:
Best regards,
Paul.