A new type of double-flow accumulator was developed

which can automatically adjust the amount of circulating refrigerant on the system of multi-functional air-conditioning/hot-water heater so that the system was more stable and efficient under multi-working modes. Based on the principle of maximum COP

the optimal refrigerant charge of the variable refrigerant flow rate system was determined by experiment for the modes of refrigeration only and both refrigeration and hot water in the summer. The tested results showed the optimal amounts of charge for the two modes were 6.5 kg and 7.5 kg respectively

and its maximum COP were 3.80 and 5.88 respectively when the outdoor temperature was 32 ± 1℃. When the refrigerant charge changes

by controlling the throttle valve

the COP could be close to the case with the optimal refrigerant charge. Moreover

a series of performance parameters

such as COP

the refrigerating capacity

the degree of subcooling and superheat at optimal refrigerant charge

were investigated with the opening degree of the throttle valve. The results show that when refrigerant charge is the same

the COP and the refrigerating capacity of both refrigeration and hot water mode is bigger compared with refrigeration only mode. Experimental results also show that the double throttling accumulator plays an important role in regulating the refrigerant cycle and saving energy.