Heat pump having a charge management receiver

A heat pump system, comprising:

• a compressor;
• a flow reverser;
• a first heat exchanger;
• a second heat exchanger;
• a receiver assembly, the receiver assembly including:
• a first receiver volume,
• a second receiver volume,
• a fluid line configured to connect the first receiver volume and the second receiver volume, and
• a controllable valve disposed along the fluid line, the controllable valve configured to regulate flow between the first receiver volume and the second receiver volume,
• wherein the first receiver volume is configured to accommodate an amount of refrigerant based on a difference between a refrigerant charge for cooling operations of the heat pump system and a refrigerant charge for heating operations of the heat pump system;
• an expander connecting the second receiver volume of the receiver assembly to the second heat exchanger, and the first receiver volume, the second receiver volume, and the expander in series connecting the first heat exchanger to the second heat exchanger;
• and
• a hot gas injection line providing fluid communication between the compressor and the second receiver volume.

A method for operating a heat pump system, comprising:

• operating the heat pump system in a cooling mode having a first working fluid charge level, wherein when the heat pump system is in the cooling mode, working fluid flows through a first receiver volume and a second receiver volume in a first flow direction;
• operating the heat pump system system in a heating mode having a second working fluid charge level, wherein when the heat pump is in the heating mode, storing an amount of the working fluid that is the difference between the first working fluid charge level and the second working fluid charge level in the first receiver volume, and the working fluid flows through the first receiver volume and the second receiver volume in a second flow direction opposite to the first flow direction;
• and
• controlling a variable quantity of refrigerant stored in the second receiver volume based on one or more operational parameters of the heat pump system;
• wherein the first receiver volume and the second receiver volume are connected by a fluid line including a controllable valve.