HVAC Systems

The system can be operated in air-conditioning mode (Fig. 2) or in heat pump mode (Fig. 3) to cool and heat, respectively, a defined space such as the passenger compartment of a vehicle. The system has a compressor (1), an external cooler (3), a first internal heat exchanger unit (6) comprising two separate heat exchangers (6a,6b), and a second internal heat exchanger unit (8) comprising a single heat exchanger. The heat exchanger 6a is operated as an evaporator during air conditioning mode but is bypassed in favour of the heat exchanger 6b in heat pump mode. The heat exchanger 8 is used in both modes, via an expansion valve (7) for air conditioning and via a bypass valve (12) for heating.