## 5 Conclusions  
Variable working condition parameters in ORC systems are typically derived from design values, artificial givens, or experiments, without taking into account their correlations with the operating parameters in the model. Analyzing the performance changes in the system based on the performance parameter changes in the heat exchangers is insufficient. In addition, a model perspective of the system control solution is absent from the steady-state control of the system when the heat source varies. In order to solve the above problems, this paper included the following working steps:  
1. A system model for the application scenario of a 100-200 kW ORC system with BPHEs was designed. 2. A sensitivity analysis of the system was carried out based on the performance changes in the heat exchangers. 3. To make sure the system could continue to produce a steady power output even when the heat source's temperature fluctuated, an adjustment strategy and modeling computation were proposed. 4. The model results were compared and verified with the results of the R245 fa-ORC experimental test papers, which provided a foundation for the design and practical application of the ORC system. The main results were the following:  
Figure 16: The linear relationship between the \(K_{e}\), \(m_{r}\), and heat flux in the evaporator. Figure 15: The curve of the evaporator-phase zone ratio varying with \(T_{hw}\). When the heat source temperature was 125 \({}^{\circ}\)C and the condenser temperature was 45 \({}^{\circ}\)C, as the evaporation pressure increased from 600 to 1410 kPa, the two-phase zone in the evaporator accounted for the largest proportion, increasing from 70.22% to 75.83%. The supercooled zone followed, decreasing from 27.56% to 20.72%. The superheated zone, which accounted for the smallest proportion, increased from 1.53% to 3.44%. The decrease in the mass flow rate and heat flux made the heat transfer coefficient decrease from 46.32 kW/m\({}^{2}\) to 14.04 kW/m\({}^{2}\). The evaporator utilization ratio decreased from 74.85% to 38.32% and the condenser utilization ratio from 66.61% to 13.69%. The output power had a maximum value of 153.11 kW. When the output power reached its maximum, the system efficiency was 7.78% and the mass flow rate was 9.13 kg/s. The system efficiency increased from 5.74 to 11.04%. 2. When the heat source temperature was 125 \({}^{\circ}\)C and evaporation temperature was 104 \({}^{\circ}\)C, the increase in the condensation temperature from 28 to 48 \({}^{\circ}\)C made the mass flow rate have a tiny increase of 0.02% and an average value of 3.36 kg/s. The two-phase zone and superheated zone slightly increased from 74.91% to 75.81% and from 3.28% to 3.32%, respectively. The ratio of the supercooled zone decreased from 21.80% to 20.87%. The heat flux increased from 52.83 kW/m\({}^{2}\) to 63.94 kW/m\({}^{2}\), while the heat transfer coefficient increased from 1721.31 W/(m\({}^{2}\cdot\)K) to 237.77 W/(m\({}^{2}\cdot\)K). The evaporator utilization ratio dropped from 70.56% to 51.91%, and the condenser utilization ratio dropped from 95.94% to 45.71%. The system efficiency dropped from 13.64% to 10.43%, and the expander output power dropped from 116.95 kW to 80.60 kW. 3. When the heat source temperature increased, fluctuations in power generation were produced. The was in order to balance out these fluctuations and simulate the law that the mass flow rate was controlled by the working fluid pump and remained basically unchanged during actual stable operation. The evaporation pressure increased from 814.46 kPa to 1136.46 kPa, while the condensation temperature increased from 294.46 kPa to 412.01 kPa. System efficiency increased from 7.83% to 7.95%. At this time, in the BPE, the two-phase zone proportion decreased from 69.65% to 67.82%, the supercooled zone proportion increased from 28.70% to 30.12%, and the superheated zone proportion increased from 1.86% to 2.06%.