Lubricant base oil, refrigerator oil and working fluid composition for refrigerators

A working fluid composition for a refrigerating machine oil, comprising:

• a refrigerating machine oil comprising a base oil comprising an ester synthesized from:
• a first component that is at least one selected from polyhydric alcohols having 2 to 4 hydroxyl groups;
• a second component that is at least one selected from polybasic acids having 6 to 12 carbon atoms;
• and
• a third component that is at least one selected from monohydric alcohols having 4 to 18 carbon atoms and monocarboxylic acids having 2 to 12 carbon atoms,
• wherein the first component comprises
• a first alcohol that is at least one selected from neopentyl glycol, trimethylolpropane and pentaerythritol;
• and
• a second alcohol that is a butanediol, and
• a refrigerant comprising at least one selected from hydrofluorocarbons, hydrofluoroolefins, hydrocarbons having 2 to 4 carbon atoms, and carbon dioxide.