Definition
In an aircraft refrigeration or air conditioning system, the additional heat absorbed by a refrigerant vapor after it has fully evaporated, raising its temperature above the boiling point that corresponds to its pressure. Superheat ensures that only vapor — not liquid refrigerant — leaves the evaporator and enters the compressor.
Plain English
Once a refrigerant has finished turning from liquid into gas, any extra warming it picks up before reaching the compressor is called superheat. It's a way of confirming the refrigerant is fully vapor and safe to compress.
Context Anchor
Seen in aircraft air-conditioning and refrigeration system maintenance, especially when checking refrigerant temperature and pressure.
Derivation
From Latin 'super' meaning 'above' or 'beyond,' combined with 'heat.' Literally 'heat beyond' — in this case, heat beyond the point where the refrigerant has finished boiling into vapor.
Why Pilots Care
Liquid refrigerant entering the compressor can damage it, since compressors are designed to compress gas, not liquid. Measuring superheat is how technicians confirm the system is operating safely and efficiently.
Grounding Statement
Picture water boiling in a kettle: once all the water has turned to steam, any extra heat the steam picks up is superheat. The refrigerant works the same way.
Intuition Check
Superheat does not mean extreme heat or overheating. It means a measured number of degrees above the boiling point for the substance at its current pressure.
Example Sentence 1
The technician measured the superheat at the evaporator outlet to confirm the refrigerant charge was correct.
Example Sentence 2
Low superheat readings indicated the expansion valve needed adjustment to prevent liquid refrigerant from reaching the compressor.