Part of Phase 5: Rebuilding Technology. The overview is Refrigeration; its sister domain is Engines.
A refrigerator is a heat engine run backwards. An engine takes heat from something hot, turns part of it into work and rejects the rest; a refrigerator is fed work, or heat, and moves heat from something cold to something warmer. The cycle, the fluid and the components are the same kind in both, which is why the compressor pages here and the piston pages in the engines domain describe such similar parts.
The domain starts with the cooling a settlement can do without any machine, then builds the four-step cycle one step at a time, then chooses a working fluid. Ammonia is the fluid a settlement can make, and it is toxic, flammable in a band of air and corrosive to copper, so every machine page that uses it is built in steel and carries a pressure-safety warning. Two machine families follow: the heat-driven absorption refrigerator, which needs a fire or the sun and no electricity, and the compressor machine, which needs steady shaft power. The last groups cover keeping the cold in, what the cold is used for, and the safety of the plant.
Every pressure, rating, test pressure and relief setting is left to a code or to a certified component. Figures that are recalled and not sourced from the overview are marked as recalled in the pages that use them.
Cooling Without A Machine
Ice, evaporation and ground temperature, and when each works.
The Four-Step Cycle
Compress, condense, expand, evaporate, and the temperature lift that sets the work.
Working Fluids
Which fluids can carry the heat, what each one costs in danger, and why ammonia leads.
Heat-Driven Absorption Machines
The cycle that runs on a fire or the sun, from the principle to the build and the faults.
Compressor Machines
The shaft-driven alternative and the pipework and seals both kinds need.
Keeping The Cold In
Insulation and the cold room built around the evaporator.
What Refrigeration Is Used For
Food, medicines and ice, and the habits that keep a cold chain unbroken.
Safety
Poisoning, fire, asphyxiation and burst risk, with ammonia and pressure vessels each given their own page.