Aiming at the household air source heat pump for “coal to electricity”

a capillary as a throttle element is proposed to replace the thermal expansion valve or the electronic expansion valve

and an experimental device for heat pump system was set up. The influence of different capillary length on the compressor suction pressure

exhaust temperature and heat capacity of the unit under variable frequency regulation of compressor were experimentally studied. The experimental results show that

after replacing the thermal expansion valve or the electronic expansion valve

the system can run stably for a long time. The system has the best thermal performance when the capillary length is 500 mm and the compressor frequency is 35 Hz

and the heating capacity and heating COP are the largest

but the suction pressure and the exhaust temperature are moderate.