Provided are a refrigerant vessel and a refrigeration cycle apparatus capable of suppressing accumulation of a refrigerating machine oil inside. A secondary-side receiver reserves a refrigerant in a secondary-side refrigerant circuit in which a refrigerant and a refrigerating machine oil circulate, the secondary-side receiver including a vessel body, a first refrigerant pipe connected to the vessel body, and a second refrigerant pipe connected to the vessel body, in which the refrigerating machine oil is incompatible with the refrigerant and has a higher density than the refrigerant, and the second refrigerant pipe extends downward from a bottom part of the vessel body.

A heating, ventilation, and air conditioning (HVAC) system includes a flash tank configured to receive a refrigerant and to separate the refrigerant into vapor refrigerant and liquid refrigerant. The flash tank is configured to generate a flow of refrigerant therein along a circular flow path. The flash tank has a main body having a circular cross-section with a diameter and an inlet coupled to the main body and configured to direct the refrigerant into the main body. The inlet has a center line extending in a common direction with the diameter, and the center line is offset from the diameter in a radial direction.

A cooling device is provided, which comprises a cooling circuit comprising an evaporator and a compressor connected to the evaporator by a first fluid line of the cooling circuit, wherein the compressor is adapted to compress cooling agent in the cooling circuit during an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor. The cooling circuit comprises a condenser, which is connected to the compressor by a second fluid line of the cooling circuit. The second fluid line is connected to a fluid by-pass line of the cooling circuit by a separating portion, and wherein the separating portion is adapted to physically separate lubricant oil from the compressed cooling agent, so that the lubricant oil is collected in the fluid by-pass line.