Heres the skinny, single stage refrigeration systems are limited in the tempature range due to the refigerants used.
Yes, in some cases thats fine. Some people use ln2 in combination with a ultra low temp chiller.
Yes, sort of. The type of refrigeration system used is called a cascade system.In a cascade system there are two heat pumps, the first cools the second stage. By doing this they can employ the use of two different boiling refrigerants. The first stage uses a more commen refrigerant such as r-12 or r-134a. The second stage will run a much lower boiling point refrigerant. Without the first stage cooling the second the compressor wouldent be able to run due to the high pressures.
