[rlt]

A large piece of aluminum with ammonia pumped through it?

[aorloff]

Nothing about this is sounding economically competitive with ground based solutions

[jacquesm]

Right up to the radiation limit and then you'll either have to throttle your precious GPUs or you'll be melting your satellite or at least the guts of it. You're looking at an absolutely massive radiator here, many times larger than the solar panels that collect the energy to begin with.

[DoctorOetker]

not really, for A_radiator / A_PV = ~3; you can keep the satellite cool to about 27 deg C (300K) check my example calculation (Ctrl-F: pyramid)

[pyrale]

Where does the heat collected by amminia get evacuated?

[littlestymaar]

Through thermal radiation, it's called radiative cooling.

But it's not trivial indeed, especially if you want good power density in your space data center.