Computational modelling and simulation has become a key stone in many studies and in the design and testing of the equipment. The advantage of the modelling and simulation is that it saves time, is flexible, and various process scenarios can be performed [105]. The IPSEpro software was used in this study; it is a set of software
M. A. Al-Washahi 81 Newcastle University modules that can create, analyse, optimize, and even study the process from economic aspects. IPSEpro is highly flexible and comprehensive for modelling and analysing processes in engineering, chemical engineering, and many other related areas [152].
IPSEpro is characterised by its short calculation time, allowing you to change existing or even build components, which can then be integrated into the software. IPSEpro is COM-based software, and this increases its potential to interact with other software [152]. Moreover, it shows extreme flexibility in modelling the mass and heat balances and simulating the studied process. It has gained credit in the industry and with research companies, such as Rolls-Royce. IPSEpro simulated output results have been validated in many studies by comparison with actual process data and show good agreement [94, 105, 141]. In addition, the IPSEpro calculates the thermodynamics properties for any stream within the process, enabling the researcher to perform many related calculations, such as the energy and exergy analyses. On other hand, the disadvantage of the IPSEpro is it is not easy to find the exact error in the process modelling from error log file.
Process model creation in IPSEpro passes through two level: the first level in which the model is represented mathematically and graphically using the Model Development Kit (MDK). The IPSEpro calculation and results generation are performed by the second level, the process simulation environment (PSE) [105].
4.3.1 Model Development Kit (MDK)
SimTech built different libraries in the MDK that cover a wide range of different processes. In this study, libraries are used to develop models of the cogeneration plant at different operational scenarios and with heat recovery technologies: single stage LiBr–H2O AC, the ORC, and the IHE.
4.3.1.1 Advanced power plant library
The advanced power plant library contains 49 units representing most of the equipment available in the power plant, for example turbine, compressor, boiler, and pump. Flexibility of the IPSEpro allows development of the equipment not available in the MDK library. The library provides the researcher the data base of the physical
M. A. Al-Washahi 82 Newcastle University and chemical properties of common liquids used in this process, such as water, steam, gas, and combustion [153]. In this study, this library is used to model the different scenarios for the power plant.
4.3.1.2 Desalination process library
The desalination library contains all necessary equipment that represents both types of desalination plant thermals and membranes. The desalination library covers different desalination technologies, such as MSF, MED, TVC, MVC, and RO. The library includes most of the equipment used in the desalination, such as heat exchanger, membranes, flashing stages, pumps, compressor, and ejectors. Moreover, the library includes the physical properties of most fluids in the desalination plants, for example, distillate water, seawater, and vapour [154]. However, this study focuses on MSF desalination only.
4.3.1.3 Refrigeration process library
The refrigeration process library is a component model library that enables its user to calculate the thermodynamic properties of more than 50 refrigerants. The library enables researchers and designers to model a number of advanced thermal compression processes and to evaluate environmental refrigerants. The library includes the physical properties database that covers a wide range of refrigerants and refrigerant mixtures for both compression and absorption [105]. This library is utilized to build and simulate the model of the single stage LiBr–H2O AC and ORC
cycle.
4.3.2 Process Simulation Environment (PSE)
The Process Simulation Environment (PSE) provides a series of MDK models to set up different process. The user selects the required components from the library menu and arranges them in a series form that represents realistic plant configuration. The user enters all process parameters directly to the system, and after executing, PSE generates output protocols automatically at the end of the simulation step.
The PSE uses an equation-oriented approach, and optimized mathematical methods guarantee fast and accurate calculations. To solve a system of equations, the PSE adopts a two-phase approach: analyzing and a numerical solution. In the analysis phase, the PSE first checks the model for errors in the process specifications; if the
M. A. Al-Washahi 83 Newcastle University specifications are correct, it determines the optimum solution method. In the numerical solution phase, the PSE solves the equations with the numerical methods; specifically, it uses the Newton–Raphson method for finding the iterative root solution [152]. This method is easy, rapidly convergent, and the best known method for finding good approximation to the value of x using the iterative equation. Figure 4.4 shows the Newton–Raphson method, whereas following equations are used to find the solution:
where is n is the number of the iteration, and is a derivative of the function.
Figure 4.4: Newton–Raphson method root estimation
The PSE is a part of the IPSEpro software package used for economic evaluation of the engineering project [94]. This analysis is an important task to decide whether to accept the project implementation or to reject it. It enables the user to enter the project capital cost project investment, taxes, discount rate, revenues, and life of the project. It uses financial formulae to calculate a project’s detailed annual net present value, payback period, cost-benefit ratio, and average rate of return. Any change in project costs or revenues reflects on the results of project profitability analysis.
M. A. Al-Washahi 84 Newcastle University