## 4 Conclusions  
This paper proposes, for the first time, the research concept of comparing energy and economy between transcritical cycle high-temperature heat pumps and subcritical cycle  
Figure 13: The effect of charge amount on the system performance of different high-temperature heat pumps (T\({}_{\text{e}}\) is 293 K, T\({}_{\text{e-w-i}}\) is 313 K, T\({}_{\text{h-w-i}}\) is 313 K, and T\({}_{\text{co}}\) is 365 K).  
high-temperature heat pumps with new refrigerants. Experiments and simulations were conducted to compare the system performance and economy of two heat pumps, and the effect of different factors on the performance of two heat pumps was analyzed. The following conclusions can be obtained:  
1. R744/R1234 yf (90/10) and R515-1 are the preferred refrigerants for transcritical cycle heat pumps and subcritical cycle heat pumps, respectively.
2. The COP of the R744/R1234 yf (90/10) transcritical heat pump is generally higher than that of the R515B-1 subcritical heat pump, and the power consumption of the R744/R1234 yf (90/10) transcritical heat pump is generally lower than that of R515B-1 subcritical heat pump.
3. Compared to the R515B-1 subcritical heat pump, the cost recovery period of the R744/R1234 yf (90/10) transcritical heat pump is about 9-15 years. It is recommended that users who use heat pumps for a long time choose transcritical cycle heat pumps.
4. With the change in T\({}_{\text{e}}\), the system COP and heating capacity of the R515B-1 subcritical heat pump and R744/R1234 yf (90/10) transcritical heat pump increased by 61.11%, 11.3% and 65.91%, 13.59%, respectively.
5. With the change in T\({}_{\text{h-w-i}}\), the system COP of the R515B-1 subcritical heat pump and R744/R1234 yf (90/10) transcritical heat pump decreased by 6.74% and 13.17%, respectively. The heating capacity of the R515B-1 subcritical heat pump and R744/R1234 yf (90/10) transcritical heat pump increased by 3.24% and 5.19%, respectively.
6. The optimal charge amount of the R515B-1 subcritical heat pump is lower than that of the R744/R1234 yf (90/10) transcritical heat pump, which is only 81.8% of that of R744/R1234 yf (90/10) transcritical heat pump.  
According to the research conclusions, comparing two types of heat pumps with new refrigerants not only promotes the development of high-temperature heat pumps, as well as energy conservation and emission reduction, but also provides users with multiple choices for heat pump use. In the future, further optimization of transcritical heat pumps should be carried out from the perspectives of cost and performance.  
Conceptualization, D.S. and J.Q.; methodology, Z.L.; software, Z.L.; validation, Z.L.; resources, J.Q.; writing--original draft preparation, D.S.; writing--review and editing, D.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability Statement: Data not publicly due to privacy.  
This project was supported by Dalian Yuanshuo Energy Chemical Technology Co., Ltd. Tianjin Aoborui Technology Co., Ltd. is greatly appreciated by the authors for providing the refrigerant.  
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.