Heat pump technology can be used to upgrade and enhance the quality of low-grade waste heat in production and daily life. Zeotropic mixtures can achieve temperature matching during the heat exchange process of heat pump cycles

which realizes in-depth utilization of waste heat resources. This study conducts an experimental analysis of CO

2

/R1234yf

CO

2

/R290

CO

2

/R600a

and CO

2

/R32 zeotropic mixtures using a water-source heat pump experimental system. The performances of heat pumps with evaporators and condensers that simultaneously satisfy high-temperature differences were investigated using the zeotropic mixture. Results show that the amount of charge in the zeotropic mixture primarily affects the degree of cycle subc

ooling

thereby influencing the coefficient of performance (COP) of the system. When the mass composition of CO

2

/R1234yf is 15%/85%

an optimal refrigerant charge

which corresponds to a COP of 7.66 under the experimental condition (heat source inlet water temperature at 25 ℃

outlet at 5 ℃; heat sink inlet water temperature at 15 ℃

outlet at 45 ℃) is obtained. Furthermore

compared with pure R290

the CO

2

/R290 working pair exhibits an enhancement of 75.2% in the optimal COP

with a corresponding increase of 107.7% in the volumetric heating capacity (

q

v

). Similarly

the CO

2

/R1234yf working pair demonstrates an improvement of 27.7% in the optimal COP and an increase of 92.0% in

q

v

. The CO

2

/R32 working pair exhibits a 15.0% increase in the optimal COP. However

the CO

2

/R600a working pair exhibited only a 1.7% enhancement in the optimal COP

indicating a relatively low application potential.