Heat pump system for a vehicle

A heat pump system for a vehicle, comprising:

• a compressor configured to compress a refrigerant;
• a heating, ventilation, and air conditioning (HVAC) module including an internal condenser, an evaporator connected to the compressor via a refrigerant line, and an opening/closing door configured to adjust air having passed through the evaporator to selectively flow into the internal condenser, depending on a cooling mode or a heating mode of the vehicle;
• a heat-exchanger connected to the internal condenser via the refrigerant line;
• a first expansion valve provided on the refrigerant line between the heat-exchanger and the evaporator;
• a first connection line having a first end connected to the refrigerant line between the heat-exchanger and the first expansion valve and having a second end connected to the refrigerant line between the evaporator and the compressor;
• a second expansion valve provided on the first connection line;
• and
• a heat-exchanger module connected to the first connection line and configured to exchange heat between a coolant selectively introduced via a coolant line and the refrigerant introduced via the first connection line, wherein the heat-exchanger module is connected to the refrigerant line and configured to exchange heat between the refrigerant supplied from one of the internal condenser or the heat-exchanger and the refrigerant supplied from one of the evaporator or the first connection line.