A new heat pump system with variable composition was proposed to enhance heating capacity of air source heat pumps in winter. Experimental research was conducted under different operating conditions using mixture refrigerant R32/R134a. The results show that heating capacity
power consumption and coefficient of performance(COP)of the system increased as the composition of the highly volatile component of the mixture refrigerant increased. Compared with constant compositions
the heating capacity of the system with variable compositions at lower ambient temperatures was higher and its COP could increase by 5% when the inlet temperature of the evaporator was -14 ℃. The capacity of the heat pump can be continuously adjusted to meet the requirements of the heating load.
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