## 3 Result  
### Sensitivity Analysis  
The simulation results (Figure 6) show the mole fraction of the gas produced in the steam reformer at 500-900 \({}^{\circ}\)C. As the temperature of the steam reformer increases, the mole concentration of hydrogen increases, and the thermal efficiency of the fuel processor increases, and they are stabilized at 700 \({}^{\circ}\)C or higher. The highest thermal efficiency of the fuel processor is confirmed to be 89.15% at 900 \({}^{\circ}\)C, 88.38% at 800 \({}^{\circ}\)C, and 86.36% at 700 \({}^{\circ}\)C. In order to prevent the degradation of the catalysts, the operating temperature should be lower than 800 \({}^{\circ}\)C [42]. Figures 7 and 8 are the simulation results of the mole fraction and thermal efficiency of the fuel processor according to the HTS and LTS temperatures. For the HTS, the thermal efficiency of the fuel processor was 86.36%, regardless of temperature. For the LTS, the thermal efficiency of the fuel processor was decreased by 2% when the temperature was increased from 200 \({}^{\circ}\)C (86.36%) to 300 \({}^{\circ}\)C (84.36%). Since the HTS and LTS generate a relatively smaller amount of hydrogen compared to the steam reformer, the contribution to the thermal efficiency of the fuel processor according to the temperature change of the HTS or LTS is not significant. Therefore, the operating temperature of the HTS was fixed at \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Symbol** & **Value** & **Unit** & **Description** & **Reference** \\ \hline A\({}_{\text{MEA}}\) & 300 & cm\({}^{2}\) & MEA area & - \\ F & 96,500 & C/mol & Faraday constant & - \\ \(n_{cell}\) & 160 & EA & Number of cells & - \\ R & 8.314 & J/mol K & Universal gas constant & - \\ \(T_{cell}\) & 150 & \({}^{\circ}\)C & Temperature of cells & - \\ \(\delta_{aCL}\) & 0.015 & mm & Thickness of anode/cathode GDLs, CLs & [37] \\ \(\delta_{cell}\) & 0.015 & mm & Thickness of anode/cathode GDLs, CLs & [37] \\ \(\delta_{mem}\) & 0.35 & mm & Thickness of anode/cathode GDLs, CLs & [37] \\ \(\kappa\) & 300 & S/m & Electronic conductivity & [37] \\ \(j_{0,a}^{ref}\) & 10\({}^{9}\) & A/m\({}^{2}\) & Reference exchange current density in anode & [36] \\ \(\alpha_{a}^{ref}\) & 10\({}^{4}\) & A/m\({}^{2}\) & Reference exchange current density in cathode & [36] \\ \(\alpha_{a}\) & 0.5 & & Anode transfer coefficient & [38] \\ \(\alpha_{c}\) & 0.65 & & Cathode transfer coefficient & [38] \\ \(C_{H_{2},ref}\) & 40.88 & mol/m\({}^{3}\) & Reference H\({}_{2}\) molar concentration & [38] \\ \(C_{O_{2},ref}\) & 40.88 & mol/m\({}^{3}\) & Reference O\({}_{2}\) molar concentration & [38] \\ \(v_{aCL}\) & 0.4 & & Porosity of CL & [38] \\ \(v_{cCL}\) & 0.4 & & Porosity of CL & [38] \\ \(v_{GDL}\) & 0.6 & & Porosity of CL & [38] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: PEMFC parameters used in the combined fuel processor and PEMFC simulation. 400 \({}^{\circ}\)C [26], and the operating temperature of the LTS was fixed at 200 \({}^{\circ}\)C in the simulation so that the HTS and LTS each showed the highest efficiency. The dependence of the CO tolerance of the HT-PEMFC was experimentally confirmed by [PERSON] and co-workers, who found that the CO tolerance of the HT-PEMFC increased with increasing temperature. According to their study, the CO tolerance of the HT-PEMFC increased by up to 5% of CO at 180 \({}^{\circ}\)C [43]. They also found that no degradation in performance was observed below 0.6 A/cm\({}^{2}\) at 180 \({}^{\circ}\)C as the CO concentration increased from 2% to 5%. On the other hand, at 140 \({}^{\circ}\)C and 160 \({}^{\circ}\)C, the performance degradation was 17.5% and 12.5%, respectively. This CO tolerance enables options for different CO removal processes in fuel processing systems. The CO generated at the HTS and LTS in Figures 7 and 8 are 5.03% and 0.46%, respectively. Based on this result, a single water-gas shift reactor may be sufficient to supply H\({}_{2}\) to the HT-PEMFC.