At the 50 C operating temperature, the ammonia operates at 20 bar, which is about four times higher than the water vapor pressure for the 146 C heat pipe.
(the ammonia; operates; T:At the 50 C operating temperature) (20 bar; is; about four times higher than the water vapor pressure for the 146 C heat pipe)
the ammonia 20 bar
operates is
T:At the 50 C operating temperature
about four times higher than the water vapor pressure for the 146 C heat pipe