# Simulation of Hybrid Photovoltaic Solar Assisted Loop Heat Pipe/Heat Pump System
## 4 Simulation Results and Discussion
### Comparison of HP Mode and LHP/HP Mode under Typical Weather Conditions
#### 4.1.1 On Sunny Days in Spring or Autumn  
The operating performances of independent HP and hybrid LHP/HP mode were simulated when the solar irradiation \(E_{S}\) was assumed to be 600 W/m\({}^{2}\) and the ambient temperature \(t_{a}\) was 15 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c} \hline
**Component** & **Type and Main Parameters** \\ \hline PV/T evaporator & aluminum plate: 780 mm \(\times\) 1270 mm \\  & copper tube: 9.52 mm (inner diameter) \\  & insulating layer: 50 mm (thickness) \\ \hline compressor & type: QD123Y \\  & theoretic displacement: 12.9 cm\({}^{3}\)/stoke \\ \hline throttle device & capillary: 2 m (length); 2 mm (inner diameter) \\ \hline condensing tank & volume: 150 L \\  & condensing tube: 18 m (length); 10 mm (inner diameter) \\ \hline \end{tabular}
\end{table} 
Table 1: Numerical values of parameters used in experiment. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline
**HP** & \(\mathbf{E_{s}}\) & \(\mathbf{t_{a}}\) & \(\mathbf{t_{wi}}\) & \(\mathbf{t_{wo}}\) & \(\mathbf{t/min}\) & \multicolumn{2}{c}{**Q\({}_{w}\)/MJ**} & \multicolumn{2}{c}{**\(N_{com}\)/MJ**} \\ \cline{2-13}  & **W/m\({}^{2}\)** & \({}^{\circ}\)C & \({}^{\circ}\)C & \({}^{\circ}\)C & **exp** & **sim** & **exp** & **sim** & **exp** & **sim** & **exp** & **sim** \\ \hline
1 & 686 & 35.2 & 30.4 & 54.1 & 200 & 209 & 14.89 & 14.28 & 3.86 & 3.71 & 3.79 & 3.85 \\
2 & 743 & 33.3 & 30.3 & 53.9 & 200 & 197 & 14.70 & 14.96 & 3.81 & 3.76 & 3.86 & 3.98 \\
3 & 699 & 36.1 & 30.4 & 54.2 & 200 & 202 & 14.97 & 14.83 & 3.85 & 3.79 & 3.89 & 3.94 \\ error/\% & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) & 4.5 & 4.1 & & 3.8 & & 3.1 \\ \hline
**LHP** & \(\mathbf{E_{s}}\) & \(\mathbf{t_{a}}\) & \(\mathbf{t_{wi}}\) & \(\mathbf{t_{wo}}\) & \(\mathbf{t/min}\) & \multicolumn{2}{c}{**Q\({}_{w}\)/MJ**} & \multicolumn{2}{c}{**\(\mathbf{t_{hi}}\)/\%**} & \multicolumn{2}{c}{\(\mathbf{\eta_{pp}}\)/\%**} \\ \cline{2-13}  & **W/m\({}^{2}\)** & \({}^{\circ}\)C & \({}^{\circ}\)C & \({}^{\circ}\)C & **exp** & **sim** & **exp** & **sim** & **exp** & **sim** & **exp** & **sim** \\ \hline
4 & 630 & 37.7 & 31.4 & 47.7 & 420 & 418 & 10.3 & 10.59 & 37.36 & 36.9 & 9.23 & 9.32 \\
5 & 736 & 37.5 & 32.5 & 50.8 & 420 & 407 & 11.58 & 11.7 & 36 & 37.3 & 8.82 & 9.17 \\
6 & 741 & 37 & 32.3 & 51.3 & 420 & 404 & 11.93 & 11.74 & 36.97 & 37.5 & 9.37 & 9.06 \\ error/\% & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) & 3.8 & & 2.8 & & 3.6 & & 3.7 \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of simulation values and experimental values. HP, heat pump; LHP, heat pump; COP, coefficient of performance. \begin{table}
\begin{tabular}{c c c c c} \hline
**Parameter** & **Value** & **Unit** & **Parameter** & **Value** & **Unit** \\ \hline \(A_{p}\) & 4 & m\({}^{2}\) & \(\beta\) & 0.86 & \\ \(C_{p,w}\) & 4200 & J/(kg\(\cdot\)K) & \(\delta_{\text{m}}\) & 0.001 & m \\ \(d\) & 9 & mm & \(\varepsilon\) & 0.9 & \\ \(k_{m}\) & 386 & W/(m\(\cdot\)K) & \(\eta_{0}\) & 0.097 & \\ \(R_{\text{glass}}\) & 0.00356 & (m\({}^{2}\cdot\)K)/W & \(\eta_{\text{v}}\) & 0.65 & \\ \(R_{\text{{{EVA}}}}\) & 0.00143 & (m\({}^{2}\cdot\)K)/W & \(\sigma\) & 5.67 \(\times\) 10\({}^{-8}\) & W/(m\({}^{2}\cdot\)K\({}^{4}\)) \\ \(V_{h}\) & 0.4 & m\({}^{3}\)/h & \(\tau_{\text{g}}\) & 1.0 & \\ \(\alpha\) & 0.9 & & & & \\ \hline \end{tabular}
\end{table} 
Table 3: Numerical values of parameters used in simulation. Figures 4 and 5 show the simulated operating performances for independent HP mode and hybrid LHP/HP mode on sunny days in spring or autumn. Independent LHP mode was not discussed here since the system would not work efficiently for the reason that the weather condition cannot satisfy this passive mode. Figure 4 illustrates that the independent HP mode would need only 195 min to heat water from 15 \({}^{\circ}\)C to 50 \({}^{\circ}\)C, and the COP decreased from 6.1 at the beginning to 3.08 at the end of the heating process. While for hybrid LHP/HP mode, the total time of water heating was 360 min.