Patent ID: 8635879

Claim:
A heat pump, comprising: a coolant main circuit that includes a compressor, a condenser that condenses coolant compressed by the compressor, an expander that expands coolant condensed by the condenser, and an evaporator that evaporates coolant expanded by the expander; a first coolant injection circuit that extends from a first point on the cooling main circuit between the condenser and the evaporator to a first point on the compressor between a coolant inlet and a coolant outlet thereof; a second coolant injection circuit that extends from a second point on the cooling main circuit between the condenser and the evaporator and a second point on the compressor between the coolant inlet and the coolant outlet thereof, wherein the first and second points on the compressor are different to correspond to respective preset middle pressures based on an evaporation temperature of the coolant; and a controller configured to selectively open and close the first and second coolant injection circuits are opened and closed to generate the respective preset middle pressures, wherein the controller is configured to de-activate the first coolant injection circuit or the second coolant injection circuit when a respective supercooling degree exceeds a preset supercooling degree corresponding to a condensation temperature of the coolant.