Hot refrigerator coils...(Fun Finder)

FWIW, what is happening in the top, condenser coil is condensing pure liquid ammonia- the cooler you can make the coil, the more ammonia is produced. From here the ammonia goes down to the freezer, which contains the hydrogen (or Helium). Due to Dalton's law, which basically states that in a mixture of gasses, the total pressure is the sum of each gasses partial pressure, and hydrogen has a very low partial pressure, lower than ammonia, so the liquid ammonia evaporates, which takes requires heat, which comes from the inside of the box.

So, the evaporator coil will be the hottest, but it is where the most heat needs to be removed (other than inside the box :) )