Unit of refrigeration:
Unit of refrigeration is Ton The cooling effect produced by melting of One ton of Ice in 24Hrs is called refrigeration effect and this is measured as “Commercial Ton of refrigeration”.
Denoted by TR (ton of refrigeration).
COP:
COP means
Coefficient of Performance.
It is defined
as the cooling effect produced or performed by the given refrigerant. 
TL = Low Temperature
TH = High Temperature
T1 = High Temperature
T2 = Low Temperature