The heating performance of a three-heat exchanger heat pump air-conditioning system of an electric vehicle in winter is investigated experimentally. The effects of indoor

outdoor ambient temperatures and relative humidity on the outlet temperature of the heating ventilation and air conditioning (HVAC) module

coefficient of performance (COP) and other performance parameters are investigated at different compressor speeds. The results show that higher compressor speeds can improve the outlet air temperature and heating capacity of the HVAC module

but the COP of the system decreases. When the compressor speed is maintained constant

for every 5 ℃ increase in the ambient temperature

the heating capacity increases by 9%–22%

the outlet temperature increases by 6–9 ℃

and COP increases by 7%–11%. When the outdoor relative humidity increases from 40% to 80%

the heating capacity increases by 15%–20%

outlet temperature increases by 2–3 ℃

and the COP increases by 6%–9%.