A method of suppressing chaotic oscillations in a tubular reactor with mass recycle is discussed. The method involves intervention in the temperature of the input flow by the recirculation flow and the temperature set from the exterior. The most advantageous solution was proved to be heat coupling elimination and maintenance of the reactor input temperature on the set level. Moreover, the reactor modelwas identified on the basis of a chaotic solution, as it provides the biggest entropy of information.
Chemical heat pumps (CHP) use reversible exothermal and endothermal chemical reactions to increase the temperature of working fluids. In comparison to the “classical” vapour compression chemical heat pumps, CHP enables us to achieve significantly higher temperatures of a heated medium which is crucial for the potential application, e.g. for production of superheated steam. Despite the advantages presented, currently, there are no installations using CHP for lowgrade waste heat recovery available on the market. The scaling up of industrial processes is still one of the greatest challenges of process engineering. The aim of the theoretical and experimental concept study presented here was to evaluate a method of reclaiming energy from low temperature waste streams and converting it into a saturated steam of temperature from 120 to 150 ◦C, which can be useful in industry. A chemical heat pump concept, based on the dilution and concentration of phosphoric acid, was used to test the method in the laboratory scale. The heat of dilution and energy needed for water evaporation from the acid solutionwere experimentally measured. The cycle of successive processes of dilution and concentration has been experimentally confirmed. A theoretical model of the chemical heat pump was tested and coefficient of performance measured.
In this study, batch fermentation of glucose to ethanol by Saccharomyces cerevisiae (ATCC 7754) was carried out using 2.5 dm3 BioFlo®115 bioreactor. The main objective of this study was to investigate the kinetics of ethanol fermentation by means of the non-structured model. The fermentation process was carried out for 72 h. Samples were collected every 4 h and then yeast growth concentration of ethanol and glucose were measured. The mathematical model was composed of three equations, which represented the changes of biomass, substrate and ethanol concentrations. The mathematical model of bioprocess was solved by means of Matlab/SimulinkTM environment. The obtained results from the proposed model showed good agreement with the experimental data, thus it was concluded that this model can be used for the mathematical modeling of ethanol production.
The effect of rotating magnetic field on the heat transfer process in a magnetically assisted bioreactor was studied experimentally. Experimental investigations are provided for the explanation of the influence of the rotating magnetic field on natural convection. The heat transfer coefficients and the Nusselt numbers were determined as a function of the product of Grashof and Prandtl dimensionless numbers. Moreover, the comparison of the thermal performance between the tested set-up and a vertical cylinder was carried out. The relative enhancement of heat transfer was characterized by the rate of the relative heat transfer intensification. The study showed that along with the intensity of the magnetic field the heat transfer increased.
Linden honey ultrafiltration (15 kDa MWCO ceramic membrane) was performed as honey solution pre-treatment before spray drying. Feed and retentate solutions with the addition of maltodextrin as a carrier were spray dried. Drying yield and physical properties of powders were studied (after drying and after 12 weeks of storage). During ultrafiltration it was possible to remove some amount of sugars responsible for honey low glass transition temperature, while keeping protein compounds. Yet, it did not have a significant impact on the drying performance and improvement of powder physical properties immediately after drying and after storage. However, the possibility to remove sugars from honey solution by ultrafiltration can be an encouragement for further research.
Carbon paste electrode (CPE) was modified with F-300 commercial activated carbon or Norit SX- 2 powdered activated carbon. CPEs were prepared for detection of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,6-dichlorophenoxyacetic acid (2,6-D) and 2,4,6-trichlorophenoxyacetic acid (2,4,6-T). The electrochemical behavior of these materials was investigated employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The modifier was found to enhance the electroactive surface area and the peak current in comparison to the bare (unmodified) carbon paste electrode. The intensity of the signal increased with the increase in adsorption ability of the modifiers. Compared to the unmodified electrode, all the new paste electrodes showed a much greater sensitivity for detection of chlorinated phenoxyacetic acids in water samples.
Evaluation of moisture absorption in foodstuffs such as black chickpea is an important stage for skinning and cropping practices. Water uptake process of black chickpea was discussed through normal soaking in four temperature levels of 20, 35, 50 and 65 °C for 18 hours, and then the hydration kinetics was predicted by Peleg’s model and finite difference strategy. Model results showed that with increasing soaking temperature from 20 to 65 °C, Peleg’s rate and Peleg’s capacity constant reduced from 13.368×10-2 to 5.664×10-2 and 9.231×10-3 to 9.138×10-3, respectively. Based on key results, a rise in the medium temperature caused an increase in the diffusion coefficient from 5.24×10-10 m2/s to 4.36×10-9 m2/s, as well. Modelling of moisture absorption of black chickpea was also performed employing finite difference strategy. Comparing the experimental results with those obtained from the analytical solution of the theoretical models revealed a good agreement between predicted and experimental data. Peleg’s model and finite difference technique revealed their predictive function the best at the temperature of 65 °C.