scholarly journals Insights from Mathematical Modelling into Energy Requirement and Process Design of Continuous and Batch Stirred Tank Aerobic Bioreactors

2019 ◽  
Vol 3 (3) ◽  
pp. 65
Author(s):  
John J. Fitzpatrick
Keyword(s):  
Oxygen Transfer ◽  
Energy Requirement ◽  
Electrical Energy ◽  
Stirred Tank ◽  
Input Design ◽  
Trade Offs ◽  
Design Variables ◽  
Minimum Total Energy ◽  
Working Volume ◽  
Aerobic Bioreactors

Bioreaction kinetics, oxygen transfer and energy modelling were applied to stirred tank aerobic bioreactors. This was done to investigate how key input design variables influence bioreactor size, feed and wasted substrate, and electrical energy requirements for aeration and cooling, and to compare batch and continuous modes of operation. Oxygen concentration in the liquid is a key input design variable, but its selection is challenging as it can result in design trade-offs. Reducing its value caused a decrease in electrical energy requirement, however this tended to increase the working volume of the bioreactor. The minimum or near-to-minimum total energy requirement for oxygen transfer occurred when operating at the onset of flooding throughout the bioreaction time. For typical KS values, continuous mode of operation required a much smaller bioreactor volume, due to higher operating cell concentration, and this is a major advantage of continuous over batch.

scholarly journals Insights from Mathematical Modelling into Process Control of Oxygen Transfer in Batch Stirred Tank Bioreactors for Reducing Energy Requirement

2020 ◽  
Vol 4 (2) ◽  
pp. 34 ◽  
Author(s):  
John J. Fitzpatrick ◽  
Franck Gloanec ◽  
Elisa Michel
Keyword(s):  
Oxygen Transfer ◽  
Energy Savings ◽  
Energy Requirement ◽  
Minimum Energy ◽  
Stirred Tank ◽  
Time Segment ◽  
Control Approach ◽  
Working Volume ◽  
Batch Bioreactors ◽  
Sudden Decrease

Significant energy savings can be made in aerobic stirred tank batch bioreactors by the manipulation of agitator power (Pag) and air flowrate per unit working volume (vvm). Control is often implemented to maintain the oxygen concentration in the bioreaction liquid (COL) at a constant value. This work used model simulations to show that controlling the Pag and vvm continuously over time, such that it is operated at or near the impeller flooding constraint results in the minimum energy requirement for oxygen transfer (strategy Cmin); however, this might prove impractical to control and operate in practice. As an alternative, the work shows that dividing the bioreaction time into a small number of constant Pag time segments (5–10), where a PID controller is used to control vvm to maintain COL constant in each segment, can achieve much of the energy saving that is associated with Cmin. During each time segment, vvm is increased and a sudden decrease in COL is used to detect the onset of flooding, after which there is a step increase in Pag. This sequence of Pag step increases continues until the bioreaction is completed. This practical control approach was shown to save most of the energy that is associated with Cmin.

scholarly journals Application of Mathematical Modelling to Reducing and Minimising Energy Requirement for Oxygen Transfer in Batch Stirred Tank Bioreactors

2019 ◽  
Vol 3 (1) ◽  
pp. 14 ◽  
Author(s):  
John Fitzpatrick ◽  
Franck Gloanec ◽  
Elisa Michel ◽  
Johanna Blondy ◽  
Anais Lauzeral
Keyword(s):  
Total Energy ◽  
Oxygen Transfer ◽  
Energy Savings ◽  
Energy Requirement ◽  
Minimum Energy ◽  
Power Input ◽  
Minimum Total Energy ◽  
And Control ◽  
Manipulation And Control ◽  
Selection Of

In this study, microbial kinetic and oxygen transfer modelling coupled with energy analysis was applied to investigate how manipulation and control of agitator power input and air flowrate can reduce and minimise the total energy requirement in a batch aerobic bioprocess subject to constraints. The study showed that major energy savings can be made by appropriate selection of these variables and how they are controlled throughout a bioprocess. In many bioprocesses, the oxygen concentration in the liquid is controlled at a constant value. This may be achieved by maintaining the agitator power at a constant value and varying the air flowrate or vice versa, or by continuously varying both. The modelling showed that the minimum or near-minimum total energy requirement occurred when operating at the onset of impeller flooding throughout the bioprocess by continuously varying both impeller power and air flowrate over the bioprocess time. Operating at the onset of flooding may not be practical to implement in practice. However, the minimum energy can be approached by dividing the bioprocess time into a small number of time segments with appropriately chosen constant agitator powers and varying the air flowrate within each segment. This is much more practical to implement.

Beyond the Known: Detecting Novel Feasible Domains Over an Unbounded Design Space

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Wei Chen ◽  
Mark Fuge
Keyword(s):  
Real World ◽  
Adaptive Sampling ◽  
Design Space ◽  
Fundamental Problem ◽  
Domain Boundary ◽  
Sampling Technique ◽  
Standard Test ◽  
Worst Case ◽  
Trade Offs ◽  
Design Variables

To solve a design problem, sometimes it is necessary to identify the feasible design space. For design spaces with implicit constraints, sampling methods are usually used. These methods typically bound the design space; that is, limit the range of design variables. But bounds that are too small will fail to cover all possible designs, while bounds that are too large will waste sampling budget. This paper tries to solve the problem of efficiently discovering (possibly disconnected) feasible domains in an unbounded design space. We propose a data-driven adaptive sampling technique—ε-margin sampling, which learns the domain boundary of feasible designs and also expands our knowledge on the design space as available budget increases. This technique is data-efficient, in that it makes principled probabilistic trade-offs between refining existing domain boundaries versus expanding the design space. We demonstrate that this method can better identify feasible domains on standard test functions compared to both random and active sampling (via uncertainty sampling). However, a fundamental problem when applying adaptive sampling to real world designs is that designs often have high dimensionality and thus require (in the worst case) exponentially more samples per dimension. We show how coupling design manifolds with ε-margin sampling allows us to actively expand high-dimensional design spaces without incurring this exponential penalty. We demonstrate this on real-world examples of glassware and bottle design, where our method discovers designs that have different appearance and functionality from its initial design set.

scholarly journals Tailoring of Composite Links for Optimal Damped Elasto-Dynamic Performance

1989 ◽  
Author(s):  
D. A. Saravanos ◽  
C. C. Chamis
Keyword(s):  
Optimal Design ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Performance Criteria ◽  
Modal Damping ◽  
Trade Offs ◽  
Design Variables ◽  
Material Systems ◽  
Structural Composite ◽  
Selective Minimization

Abstract A method is developed for the optimal design of composite links based on dynamic performance criteria directly related to structural modal damping and dynamic stiffness. An integrated mechanics theory correlates structural composite damping to the parameters of basic composite material systems, laminate parameters, link shape, and modal deformations. The inclusion of modal properties allows the selective minimization of vibrations associated with specific modes. Ply angles and fiber volumes are tailored to obtain optimal combinations of damping and stiffness. Applications to simple composite links indicate wide margins for trade-offs and illustrate the importance of various design variables to the optimal design.

Effect of Palm Oil on Oxygen Transfer in a Stirred Tank Bioreactor

2010 ◽  
Vol 10 (21) ◽  
pp. 2745-2747 ◽  
Author(s):  
Suhaila Mohd Sauid ◽  
Veluri V.P.S. Murthy
Keyword(s):  
Palm Oil ◽  
Oxygen Transfer ◽  
Stirred Tank ◽  
Stirred Tank Bioreactor

scholarly journals Combining scaling relationships overcomes rate versus overpotential trade-offs in O2 molecular electrocatalysis

2020 ◽  
Vol 6 (11) ◽  
pp. eaaz3318 ◽  
Author(s):  
Daniel J. Martin ◽  
Brandon Q. Mercado ◽  
James M. Mayer
Keyword(s):  
Energy Efficiency ◽  
Reaction Rate ◽  
Electrical Energy ◽  
Reduction Reaction ◽  
Iron Porphyrin ◽  
Scaling Relationships ◽  
Anionic Ligand ◽  
Trade Offs ◽  
Rate Versus ◽  
Molecular Catalysts

The development of advanced chemical-to-electrical energy conversions requires fast and efficient electrocatalysis of multielectron/multiproton reactions, such as the oxygen reduction reaction (ORR). Using molecular catalysts, correlations between the reaction rate and energy efficiency have recently been identified. Improved catalysis requires circumventing the rate versus overpotential trade-offs implied by such “scaling relationships.” Described here is an ORR system—using a soluble iron porphyrin and weak acids—with the best reported combination of rate and efficiency for a soluble ORR catalyst. This advance is achieved not by “breaking” scaling relationships but rather by combining two of them. Key to this behavior is a polycationic ligand, which enhances anionic ligand binding and changes the catalyst E1/2. These results show how combining scaling relationships is a powerful way toward improved electrocatalysis.

scholarly journals Study of Hybrid PVA/MA/TEOS Pervaporation Membrane and Evaluation of Energy Requirement for Desalination by Pervaporation

2018 ◽  
Vol 15 (9) ◽  
pp. 1913 ◽  
Author(s):  
Zongli Xie ◽  
Derrick Ng ◽  
Manh Hoang ◽  
Jianhua Zhang ◽  
Stephen Gray
Keyword(s):  
Thermal Energy ◽  
Waste Heat ◽  
Energy Requirement ◽  
Electrical Power ◽  
Electrical Energy ◽  
Commercial Application ◽  
Heating And Cooling ◽  
Pervaporation Membrane ◽  
Multi Stage ◽  
Multiple Effect Distillation

Desalination by pervaporation is a membrane process that is yet to be realized for commercial application. To investigate the feasibility and viability of scaling up, a process engineering model was developed to evaluate the energy requirement based on the experimental study of a hybrid polyvinyl alcohol/maleic acid/tetraethyl orthosilicate (PVA/MA/TEOS) Pervaporation Membrane. The energy consumption includes the external heating and cooling required for the feed and permeate streams, as well as the electrical power associated with pumps for re-circulating feed and maintaining vacuum. The thermal energy requirement is significant (e.g., up to 2609 MJ/m3 of thermal energy) and is required to maintain the feed stream at 65 °C in recirculation mode. The electrical energy requirement is very small (<0.2 kWh/m3 of required at 65 °C feed temperature at steady state) with the vacuum pump contributing to the majority of the electrical energy. The energy required for the pervaporation process was also compared to other desalination processes such as Reverse Osmosis (RO), Multi-stage Flash (MSF), and Multiple Effect Distillation (MED). The electrical energy requirement for pervaporation is the lowest among these desalination technologies. However, the thermal energy needed for pervaporation is significant. Pervaporation may be attractive when the process is integrated with waste heat and heat recovery option and used in niche applications such as RO brine concentration or salt recovery.

Thermoelectric Generator–Integrated Solar Air Heater: A Compact Passive System

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Kumar Venkateshwar ◽  
Abu Raihan Mohammad Siddique ◽  
Syeda Tasnim ◽  
Hari Simha ◽  
Shohel Mahmud
Keyword(s):  
Thermoelectric Generator ◽  
Energy Requirement ◽  
Electrical Energy ◽  
Cold Weather ◽  
Space Heating ◽  
Solar Air Heater ◽  
Thermoelectric Generators ◽  
Passive System ◽  
Air Heater ◽  
Operational Range

Abstract Solar air heater is a promising, economically viable, and matured technology for space heating and drying applications. One of the primary reasons for the limited usage of a solar air heater in developing countries is the unavailability of continuous electricity supply. Although the solar air heater is theoretically passive, practically electrical energy is required to achieve a steady airflow. Therefore, the unreliability of electricity forces people to rely on firewood for heat during the cold weather, which has severe effects on health and climate change. In the present work, the potential of thermoelectric generators (TEGs) to meet the electrical energy requirement of a solar air heater is studied. Two configurations, each with three different numbers of stages of TEGs, are analyzed. The effect of the integration of TEGs on the thermal performance of solar air heater is analyzed alongside the comparison between the electrical energy required by solar air heaters and electrical energy generated upon the integration of TEGs. A numerical model is developed in matlab and validated using the experimental results. One of the designs meets the electrical energy requirement of the fan in a wide operational range but lowers the process heat generation by approximately 1–6.25%. The electrical energy generated by the other design falls short of demand posed by the system in most operating range. However, the thermal energy generation is marginally higher compared to that of the conventional solar air heater.

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