## 3 Algorithmic Logic Construction
### System Sensitivity Analysis  
The sensitivity analysis model mainly includes variable evaporation pressure and condensation temperature system models, calculated by MATLAB. Both models follow the same essential steps. Variable evaporation pressure was used as an example in the following introductory analysis, which consisted of the following steps:  
1. Define the target parameters.
2. Determine the input parameters.
3. Preliminarily give the range of variable evaporation pressures: 1. Lower the limit of the interval. In order to ensure that the temperature difference or pressure difference in the system drives heat conversion, the lower limit setting value of the evaporation pressure cannot be lower than or equal to the condensation pressure value.
2. Since the mass flow rate is iteratively obtained by setting the pinch point temperature difference value, and taking into account the critical parameters of the working fluid, there are initially two judgment conditions for the upper limit value: a. The evaporation pressure is generally set to about 5 kPa lower than the critical pressure. b. Assuming that the evaporator does not have any heat exchange, the temperature of the heat source water at the pinch point temperature difference is the heat source water inlet temperature. As of right now, the evaporation temperature value is the difference between the heat source water inlet temperature and the evaporator pinch point temperature difference. This value is the upper limit value. Since the heat source water inlet temperature and the pinch point temperature difference are both settable parameters, the upper limit value is modified each time the set value fluctuates. c. It is not possible to continuously raise the evaporation pressure due to changes in other parameters. These need to be located by running multiple sets of working conditions during program operation and debugging.
4. Ascertain the quantity and content of judgment conditions based on the parameters that may cause errors and require debugging under the aforementioned fundamental presumptions. Apart from modifying the variable interval, the set input parameter values are subject to the following constraints: (1) The heat source water temperature cannot be increased endlessly as an input value. The maximum heat load of the heat exchanger or the actual heat exchange area must be taken into consideration. Having too high of a heat source water temperature and flow rate can exceed the heat exchanger load and fail to converge.  
(2) Considering that the evaporation pressure value is too high, the temperature value of the working fluid at the evaporator outlet is equal to or higher than the heat source temperature value.  
(3) The heat transfer coefficient of the heat exchanger limits the upper limit of the interval.  
Figure 4: The actual working process of the ORC system.  
(4) The difference in temperature between the saturated gaseous point of the working fluid and the corresponding water temperature of the heat source is too small due to an excessively high condensation temperature or evaporation pressure. To begin the procedure, a fair initial value must be chosen; if the issue still exists after a given number of iterations, the interval's upper limit must be decreased.  
(5) Establish calculating models for each component.  
(6) Determine the output parameters and curves of the system.  
(7) Perform program debugging.  
The algorithm logic diagram of the system sensitivity analysis is shown in Figure 5.  
Figure 5: The algorithmic logic diagram of the system sensitivity analysis.