## 3 Results and Discussion  
### Influence of Inlet Fuel Mass Flow  
The dynamic characteristics of the fuel temperature at the outlet of the heating section were studied with respect to changes in the inlet mass flow. In this part, the benchmark case is under an outlet pressure of 5 MPa, a mass flow rate of 1 g/s, a \(T_{foil}\) of 673.15 K, and inlet mass flow changes in the value of \(\pm\)10%, \(\pm\)20%, \(\pm\)50%, and \(+\)100%. As shown in Figure 9a, the cross-sectional average fuel and wall temperatures at the outlet of the heating section gradually increased with a decrease in the inlet mass flow in the initial stage of the response and then approached a stable value. As the inlet mass flow decreased, the stable fuel and wall temperatures gradually increased. In addition, the stable fuel temperature gradually decreased with an increase in the inlet mass flow (Figure 9b). The stable fuel temperatures and times are shown in Figure 10. With a decrease in the inlet mass flow, the higher the stable fuel temperature, the longer the stable time. Similarly, with an increase in the inlet mass flow, the stable fuel temperature was lower and the stable time was shorter. As shown in Figure 10c, with the same range of inlet mass flow variation, the outlet fuel temperature of the initial working condition was higher, and the stable time was shorter. As shown in Figure 10c, the inlet mass flow and steady velocity decreased when the \(T_{foil}\) was 373.15 K and 473.15 K. The inlet mass flow decreased and the steady velocity increased with the \(T_{foil}\) of 573.15 K and 673.15 K. A decrease in the inlet mass flow can lead to a decrease in the inlet velocity at a constant inlet temperature. Furthermore, according to the existing steady flow and heat transfer characteristics, the thermal acceleration affects the forced convective heat transfer of n-decane. With two \(T_{foil}\) values of 573.15 K and 673.15 K, as the inlet mass flow decreases, the fuel passes through the pseudo-critical temperature zone. Near the pseudocritical temperature, the thermo-physical properties of n-decane change dramatically. As a result, the increase in velocity caused by the decrease in n-decane density was much larger than that caused by the decrease in inlet mass flow. As shown in Figure 10a, with \(\Delta r_{m}\) of \(-\)10% and \(-\)20%, the overall heat transfer coefficient decreases first and then increases with the decrease in inlet mass flow at the initial stage of response. With \(\Delta r_{m}\) of \(-\)50%, the overall heat transfer coefficient decreases first  
In this study, a multivariate analysis was conducted to analyze the main physical quantities that affect the overall heat transfer coefficient. The overall heat transfer coefficient was primarily influenced by the surface convective heat transfer coefficient (Figure 11). The variation trend of the surface convective heat transfer coefficient can be explained by considering the variation trends of the adjacent wall temperature difference and the derivative of the adjacent fuel temperature. Figure 11: Dynamic process of the OHTC and the SCHTC at X = 900 mm. (**a**) \(\varDelta r_{m}\) decreases; (**b**) \(\varDelta r_{m}\) increases. Figure 10: Stable parameter distribution with \(\varDelta r_{m}\). (**a**) Stable temperature distribution with \(\varDelta r_{m}\). (**b**) Stable time distribution with \(\varDelta r_{m}\); (**c**) Stable velocity distribution with \(\varDelta r_{m}\). As shown in Figure 12a, the difference between the inner wall temperature and the adjacent wall fuel temperature first decreased and then increased at the beginning of the response and then approached a stable value. In contrast, with the increase in the inlet mass flow, the temperature difference first increased and then decreased, and the stable value was smaller (Figure 12b).