My current understanding is that in addition to the reasons pointed out in the answer to this question here, another reason for choosing ammonia in the space station external coolant loops is that the pipes in the radiators can withstand the burst pressure of freezing ammonia.
One aspect speaking against ammonia is its low boiling point at ambient pressures, so the radiator is run at pretty low temperatures, which decreases its efficiency. Water/Glycol would be better in that respect but water develops high pressures on freezing.
Given that, how can the pressure of an expanding liquid on freezing be calculated?
And how would the combination with a liquid that contracts on freezing factor in with that?