## 5 Conclusions  
This study developed a refrigeration cycle prediction model for an air-source heat pump system using air-side measurement data that are easy to measure in situ. The main operation data, COP, and cooling capacity, were predicted using the proposed prediction model, and the results were evaluated. The proposed refrigeration cycle measurement method of the air-source heat pump system was analyzed and evaluated using the data from NIST. The air enthalpy change calculation method was summarized by measuring the temperature and humidity of the inlet and outlet air of the evaporator and condenser of the air-source heat pump system. The refrigerant enthalpy change calculation method was summarized using the air enthalpy change and airflow rate. A refrigeration cycle measurement method that considers the characteristics of evaporation, compression, condensation, and expansion processes was proposed by dividing it into five steps. The proposed refrigeration cycle measurement method was evaluated by comparing the refrigerant pressure and enthalpy of evaporation and condensation inlet and outlet points with the existing refrigeration cycle. The differences between the refrigerant pressure and enthalpy at each point and the distance function after normalization were analyzed, and the distance function of the maximum error of the pressure and enthalpy measurement device was compared with that of the total data used in the analysis. All data had low distance function values compared to the maximum error, confirming the reliability of the proposed refrigeration cycle measurement method. The power consumption predicted using the proposed measurement method and the power consumption measured by the watt-hour meter were compared. In addition, the COP prediction value of the proposed refrigeration cycle and the existing refrigeration cycle measurement results were analyzed. The _MBE_ of the power consumption and COP predicted using the proposed refrigeration cycle measurement results was 0.15% and 0.04%, respectively, and the _Cv(RMSE)_ was 8.967% and 7.14%, respectively. This confirmed that the measurement data validation criteria presented in ASHRAE Guideline 14 were met. Moreover, the measurement uncertainties of power consumption and COP are \(\pm\)4.06% and \(\pm\)2.24%, respectively. The refrigeration cycle measurement method developed in this study is expected to complement the limitations of technologies that can reduce energy consumption, such as fault detection and diagnosis technology and performance improvement control measures.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Category** & **MBE** & **Cv(RMSE)** & **R\({}^{2}\)** & **Uncertainty** \\ \hline Power consumption & 0.15\% & 8.97\% & 0.86 & \(\pm\)4.06\% \\ COP & 0.04\% & 7.14\% & 0.98 & \(\pm\)2.24\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: Accuracy analysis result.  
Figure 11: Comparisons of the predicted and actual COP measurements for the system.  
**Author Contributions:** All authors contributed to this work. [PERSON]-[PERSON] investigated and wrote the original draft; [PERSON]-H.C. carried out project administration and supervisor; [PERSON]-[PERSON] gave investigation and resources. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20202020800360).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.