Scale-Down Simulators

Scale-Down Simulating Large-Scale Cultures in the Laboratory... 

Figure 2.3 The two most common scale-down simulators. The graphics below each picture depict the substrate concentration that a cell circulating in the simulator would experience, (a) Two interconnected stirred-tank reactors (STR-STR) with independent environmental parameter control. Cells are circulated between them, experiencing a square oscillation as depicted in the graphic at the bottom. The liquid volumes and flow rate determine the average to be evaluated, (b) A plug-flow reactor connected to a stirred-tank reactor (STR-PFR). Environmental perturbations...

Neubauer, P. and Juime, S. (2010) Scale-down simulators for metabolic analysis of large-scale bioprocesses. Curr. Opin. Biotechnol, 21, 114-121. 

Figure 2.3.1 (Wachtel, et al, 1972) shows the ARCO reactor that tried to simulate the real reaction conditions in a fluid cracking unit. This was a formal scale-down where many important similarities had to be sacrificed to get a workable unit. This unit was still too large for a laboratory study or test unit, but instead was pilot-plant equipment that could still give useful empirical results Since this serves a very large industry, it may pay off to try it, even if it costs a lot to operate.

A predator and prey simulation. The population of gazelles (the higher line) has been scaled down since, in reality, it would be many times that of the lions. 

A similar simulation was also carried out by McKeen and Pugsley (2003). They also found an overestimation of the bed height, compared to their experimental results. They argued that a factor should be used to scale down the... 

Such an approach, based on the experimental simulation of an industrial reactor at laboratory scale, was proposed by Zufferey [11, 12] the scale down approach. In order to simulate the thermal behavior of full-scale equipment at laboratory scale, it is necessary to combine process dynamics and calorimetric techniques. 

Zuflerey, B. (2006) Scale-down Approach Chemical Process Optimisation Using Reaction Calorimetry for the Experimental Simulation of Industrial Reactors Dynamics, EPFL, n°3464, Lausanne. 

Now that the top-down internal state variable theory was established, the bottom-up simulations and experiments were required. At the atomic scale (nanometers), simulations were performed using Modified Embedded Atom Method, (MEAM) Baskes [176], potentials based upon interfacial atomistics of Baskes et al. [177] to determine the conditions when silicon fracture would occur versus silicon-interface debonding [156]. Atomistic simulations showed that a material with a pristine interface would incur interface debonding before silicon fracture. However, if a sufficient number of defects were present within the silicon, it would fracture before the interface would debond. Microstructural analysis of larger scale interrupted strain tests under tension revealed that both silicon fracture and debonding of the silicon-aluminum interface in the eutectic region would occur [290, 291]. 

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