The software will not know about surface area and so on. Every element will be known as a data set of flow/backpressure or heat/flow, or both (for rads and waterblocks).
So for a rad you'll need at least 2 data sets:
backpressure vs flow
total heat transfer vs flow
Of course a problem arises there, air flow.
We can solve this by adding, for example, a heat transfer coefficient vs air flow, then (after fixing air flow) applying the resulting coefficient to the heat transfer vs water flow data.
That means for rads -> we need at least 3 data sets.
Heat up your Excel sheets