## 2 Establishment of Model and Experiment
### Simulation  
#### 2.2.1 Energy Thermodynamic Model  
The simple modeling of the two systems was conducted using EES software. The energy analysis is only based on the changes in refrigerant and parameters and is not related to the parameters of the external environment.  
The energy thermodynamic model is outlined as follows:  
(i) Unit work input to compressor (k)/kg):  
\[w_{comp\text{-}sub}=h_{2(2^{\prime},2^{\prime\prime})}-h_{1(1^{\prime},1^{ \prime\prime})} \tag{6}\]  
\[w_{comp\text{-}tran}=h_{2}-h_{11} \tag{7}\]  
(ii) Unit heating capacity (kJ/kg):  
\[q_{h\text{-}sub}=h_{2(2^{\prime},2^{\prime\prime})}-h_{3(3^{\prime},3^{\prime \prime})} \tag{8}\]  
\[q_{h\text{-}tran}=h_{2}-h_{3} \tag{9}\]  
(iii) \(COP_{h}\) is given by:  
\[COP_{h\text{-}sub}=\left(h_{2(2^{\prime},2^{\prime\prime})}-h_{3(3^{\prime},3^ {\prime\prime})}\right)/\left(h_{2(2^{\prime},2^{\prime\prime})}-h_{1(1^{ \prime},1^{\prime\prime})}\right) \tag{10}\]  
\[COP_{h\text{-}tran}=\left(h_{2}-h_{3}\right)/\left(h_{2}-h_{11}\right) \tag{11}\]  
where \(h\) is the enthalpy value of state points (kJ/kg). The enthalpy values of state points were obtained according to the temperature and pressure of state points measured by experiments and combined with REFPROP9.0 [32].  
It is worth noting that as this paper focuses on experiments rather than practical engineering applications, in order to find a heat source (such as industrial waste heat) that matches the actual engineering application when building an experimental platform, we applied electric heating to heat water to construct industrial waste heat. However, in the actual process, electric heating is not required to produce such waste heat, so the power consumption of this part is not considered in the calculation reported in this article.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **R1234 ze** & **R515B (R1234 ze/R227 ea)** & **R515B-1 (R1234 ze/R227 ea/RE170/R245 fa)** \\ \hline Chemical formula & C\({}_{3}\)F\({}_{4}\)H\({}_{2}\) & C\({}_{3}\)F\({}_{4}\)H\({}_{2}\)/C\({}_{3}\)HF\({}_{7}\) & C\({}_{3}\)F\({}_{4}\)H\({}_{2}\)/C\({}_{3}\)HF\({}_{7}\)/C\({}_{2}\)H\({}_{6}\)O/C\({}_{3}\)H\({}_{3}\)F\({}_{5}\) \\ Critical pressure & 3.63 MPa & 3.57 MPa & 3.88 MPa \\ Critical temperature & 382.51 K & 381.62 K & 387.71 K \\ Molar mass & 114.04 kg/kmol & 117.48 kg/kmol & 103.7 kg/kmol \\ Normal boiling point & 254.18 K & 253.82 K & 256.36 K \\ GWP & 6 & 299 & 433 \\ ASHRAE Classification & A1 & A1 & A1 \\ \hline \end{tabular}
\end{table}
Table 6: Thermophysical properties of the three refrigerants (subcritical heat pump system).  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Proportion of R744/\%** & **R744/R1234 yf** & **R744/R1234 ze** & **R744/RE170** \\ \hline
**Parameters** & **P\({}_{\text{cr}}\)/MPa** & **T\({}_{\text{cr}}\)/K** & **P\({}_{\text{cr}}\)/MPa** & **T\({}_{\text{cr}}\)/K** & **P\({}_{\text{cr}}\)/MPa** & **T\({}_{\text{cr}}\)/K** \\ \hline
60 & 8.13 & 333.93 & 8.15 & 337.36 & 8.54 & 361.22 \\
70 & 8.13 & 326.01 & 8.08 & 328.11 & 8.78 & 350.26 \\
80 & 8.02 & 318.55 & 8.13 & 320.89 & 8.78 & 337.48 \\
90 & 7.8 & 311.49 & 7.87 & 312.81 & 8.41 & 322.63 \\ \hline \end{tabular}
\end{table}
Table 7: Critical parameters of R744 mixtures (transcritical heat pump system).