Working fluid composition and refrigerator

A working fluid composition comprising:

• a refrigerating machine oil;
• and
• a refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)) and 2,3,3,3-tetrafluoropropene (HFO-1234yf),
• wherein the working fluid composition has a refrigerant fraction at 80° C. and 2.5 MPa of 80% by mass or less,
• wherein the refrigerating machine oil comprises:
• at least one base oil selected from the group consisting of a polyol ester and a polyvinyl ether;
• at least one epoxy-based acid scavenger selected from the group consisting of a glycidyl ester-based acid scavenger and a glycidyl ether-based acid scavenger;
• a phenol-based antioxidant;
• and
• a phosphorus-containing antiwear agent, and
• wherein a P/E ratio represented by the following formula (A) is 0.2 or more and 1.1 or less:
• P
• /
• E
• ⁢
• ratio
• =
• (
• W
• P
• ×
• N
• P
• /
• M
• P
• )
• /
• (
• W
• E
• ×
• N
• E
• /
• M
• E
• )
• (
• A
• )
• wherein WP represents a content (% by mass) of the phosphorus-containing antiwear agent based on a total amount of the refrigerating machine oil,
• NP represents a number of a phosphorus atom in one molecule of the phosphorus-containing antiwear agent,
• MP represents a molecular weight of the phosphorus-containing antiwear agent,
• WE represents a content (% by mass) of the epoxy-based acid scavenger based on the total amount of the refrigerating machine oil,
• NE represents a number of an epoxy-based group in one molecule of the epoxy-based acid scavenger, and
• ME represents a molecular weight of the epoxy-based acid scavenger.