Previous research (Wang et al., 2008) shows that the refrigerant
injection affects the inner parameters of the compressor
as well as the discharge parameters, such as the discharge
temperature, specific enthalpy, and mass flow rate. The
change in these discharge parameters will influence the
performance of the condenser directly. At the same time,
the variation of the input parameters of the condenser will
affect the outlet parameter of condenser. The change of the
outlet parameters of condenser as well as the use of the
economizer will greatly impact the inlet states of evaporator,
which will influence the performance of the evaporator. Thestate variation of refrigerant in the injection tube and the
suction tube will affect the performance of the compressor
again. Finally, the system will reach a new balance. Therefore,
the optimization research on the heat pump system with
refrigerant injection should firstly begin with studying the
influence of injection on the components. Based on these
results, the optimal design and control can be pursued for
different optimization targets.