System-Level Modelling

Another example is the systematic analysis undertaken by Palsson et al. on combined SOFC and gas turbine cycles [36]. In combination with a robust and accurate 2-D SOFC model, the system-level model attempts to provide an unbiased evaluation of performance prospects and operational behaviours of such systems. The 2-D SOFC model was integrated into a process simulation tool. Aspen Plus , as a user-defined model, whereas other components constituting the system are modelled as standard unit operation models. Parametric studies can be carried out to gain knowledge of stack and system behaviour such as the influence of fuel and air flow rate on the stack performance and the mean temperature and the effects of cell voltage and compressor pressure on the system efficiency. The pressure ratio is shown to have a large impact on performance and electrical efficiencies of higher than 65% are possible at low-pressure ratios. 

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In each of the studies described above, the reader is encouraged to watch the development of the two phases from the original homogeneous mixture. Note that there is significant clustering of like molecules well before two discrete phases form. Another observation is the ragged nature of the interface. It is not a smooth discrete separation in this molecular system level model. 

Systemic poisons, 21 836 Systemic toxicity, 25 202-203 System-level modeling for reliability, 26 990 Systems... 

As described, PBPK models are systems of mass balance equations describing the mass or concentration of chemicals at various loci within the tissues. Most often the loci have been at the level of the whole organ. However, the mass can be described at as fine a resolution as is necessary and as knowledge allows. For example, a PBPK model can describe the concentration at the cellular or subcellular level (Blancato and Bischoff 1993). Ultimately, the chemical input into pharmacodynamic and systems level models could easily be the output of PBPK models at whatever the necessary resolution. For example, if a perturbation in a specific cell is directly related to a concentration or mass of chemical at that cell, the PBPK model would be expanded to describe that mass or concentration. This though raises... 

Therefore, fuel cell power plant system level models, detailed component models, and their analysis are needed to determine the performance targets for the WGSMR, subject to the power plant cost, weight and performance targets set by the Department of Energy (DOE), USA, for future automotive applications with an on-board fuel processing system as shown in Table 14.1 [7]. Keeping these criteria in mind, the fuel cell power plant must now be considered. 

System Level Models of Fuel Cell Power Plants... 

Mathematical models of SOFCs have been developed at scales from the molec-ular/atomic level through the system level. At the nanoscale, molecular dynamics and density functional theory (DFT) models have been developed to investigate the transport of species on the surfaces of the electrodes [6] while at the macroscale, system-level models are used to consider the controls of an SOFC system [7j. The... 

Figure 26.4 Schematic of system-level modeling of an APU SOFC system.

System-level modeling of SOFCs aims to ensure that nearly uniform temperatures, currents, and fuel and air flows are seen by each individual SOFC cell in the system. This can be a daunting task in large power systems however, modeling can help in the design of the systems to ensure that there are a sufficient number of sensors, valves, and so on, to control the system and its operation correctly. 

SOFC system-level models provide valuable insight into the overall operation and design of SOFC power systems. They provide a means to investigate an SOFC... 

Chen, W.Y, J.W. Tsai, Y.R. Ju, et al. 2010. Systems-level modeling the effects of arsenic exposure with sequential pulsed and fluctuating patterns for tilapia and freshwater clam. Environ. Pollut. 158 1494—1505. 

Minutillo M, Perna A, Jannelli E (2014) SOFC and MCFC system level modeling for hybrid plants performance prediction. Int J Hydrogen Eneigy 39 21688-21699... 

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