Research and results of mathematical modeling of block ion-exchange water treatment plants operating modes and regeneration

The problem of water treatment at thermal power plants using ion-exchange technologies is a multi-parameter task. Mathematical modeling is essential for research and optimization of ion exchange technology. The analysis of hydrodynamic processes during the operation of ion-exchange filters was carried out according to the developed mathematical model. Also, a physicochemical analysis of the composition of the water treatment plant solutions under real conditions was carried out. It is shown that in the cationite and anionite filters, the flow movement occurs mainly in a mixed hydrodynamic mode. This mode of regeneration and the filter design do not allow achieving the minimum consumption of the reagent for regeneration, the minimum volume of wastewater and the maximum output of demineralized water. The mixed mode of the anion exchange filter operation allows division of the outgoing solution flow into fractions, which can be successfully used in the TPP water cycle.

A hydrogen generator coupled to a hydrogen heater for small scale portable applications

This study aims to build and test a small scale portable device able to couple a hydrogen generation system (based on a NaBH4 solution as liquid H2 carrier) to a hydrogen heater (based on the exothermic catalytic combustion of the released H2). The hydrogen generating system is based on the hydrolysis of stabilized solutions of NaBH4 (fuel solutions) which are pumped into the hydrolysis reactor. The generated H2 feeds the catalytic combustor. Two catalysts have been developed for the H2 generation and the combustion reactions able to operate at room temperature without need of additional energy supply. For the NaBH4 hydrolysis a Co-B catalyst was supported on a perforated and surface treated stainless steel (SS316) home-made monolith. For the flameless H2 catalytic combustion a Pt catalyst was prepared on a commercial SiC foam. The device was automatized and tested for the on-demand production of heat at temperatures up to 100ºC. In steady state conditions the NaBH4 solution flow is controlling the H2 flux and therefore the heater temperature. Once the steady-state is reached the system responds in a few minutes to up and down temperature demands from 80 to 100 ºC. The catalysts have shown no deactivation during the tests carried out in several days.

The Bent-Tube Nozzle Optimization of Force-Spinning With the Gray Wolf Algorithm

Force-spinning is a popular way to fabricate various fine fibers such as polymer and metal nanofibers, which are being widely employed in medical and industrial manufacture. The spinneret is the key of the device for spinning fibers, and the physical performance and morphology of the spun nanofibers are largely determined by its structure parameters. In this article, the effect of spinneret parameters on the outlet velocity is explored and the spinneret parameters are also optimized to obtain the maximum outlet velocity. The mathematical model of the solution flow in four areas is established at first, and the relationship between outlet velocity and structure parameters is acquired. This model can directly reflect the flow velocity of the solution in each area. Then, the optimal parameters of outlet diameter, bending angle, and curvature radius are obtained combined with the gray wolf algorithm (GWA). It is found that a curved-tube nozzle with a bending angle of 9.1°, nozzle diameter of 0.6 mm, and curvature radius of 10 mm can obtain the maximum outlet velocity and better velocity distribution. Subsequently, the simulation is utilized to analyze and compare the velocity situation of different parameters. Finally, the fiber of 5 wt% PEO solution is manufactured by a straight-tube nozzle and optimized bent-tube nozzle in the laboratory, and the morphology and diameter distribution were observed using a scanning electron microscope (SEM). The results showed that the outlet velocity was dramatically improved after the bent-tube parameters were optimized by GWA, and nanofibers of better surface quality could be obtained using optimized bent-tube nozzles.

Effect of phase transitions on operation of air-to-air heat exchangers with drop irrigation

The article presents the results of experimental studies of the thermal and humidity parameters of air flows of a regenerative air-to-air heat exchanger with drop irrigation and an intermediate heat carrier when operating in winter conditions with negative outside temperatures. The dependences of temperature and humidity efficiency of the heat exchanger on saline solution flow rate were determined, while the maximum temperature efficiency in the heating column was more than 70%. It is shown that under all investigated regimes in the heating column, moisture evaporated from the saline solution, and the air entering the room became more humid, which is a positive factor that increases the comfort of premises at negative outside temperatures.

Removal of isopropyl alcohol by electrical discharge from an aqueous solution with microbubbles

The removal of isopropyl alcohol impurities with an initial volume concentration of 20 % in a cell with a working area volume of 831 cm 3 in a water flow with fine air bubbles with a solution flow rate of 2 m 3/h by a quasi-volume electric discharge obtained using a multi-electrode system of sectioned needle electrodes has been experimentally investigated. At an alternating voltage of an industrial frequency of 50 Hz, the creation of a finely dispersed phase with air bubbles in an electric discharge cell increases the efficiency of isopropyl alcohol removal from the water flow by 6 %.

The Influence of Supercooling and Hydrodynamics on the Mosaic and Radial Inhomogeneity of K2NiXCo(1–X)(SO4)2·6H2O Mixed Crystal

The mosaic and radial inhomogeneity of shaped mixed crystals of K2NixCo(1–x)(SO4)2·6H2O (KCNSH) were studied depending on the supercooling of solution, its velocity and its method of supply into the shaper. It was shown that mosaic inhomogeneity could be suppressed when solution is supercooled to about 2 °C. Peripheral supply of the solution (tangential to the wall of the shaper to create a “swirling” flow) with a rate of 55–135 cm/s provides better composition uniformity along the crystal surface in comparison with upright supply of the solution (flow is perpendicular to the crystal surface).

Experimental study on dehumidification performance of liquid desiccant system with aqueous HCO2K solution

The liquid desiccant systems are one of the promising technologies in dehumidification applications. The experimental study on dehumidification performance of a counter flow structured packing liquid desiccant system is done with Aqueous HCO2K as working fluid. The HCO2K solution at different mass flow rate of air and solution is tested. The airflow rate is varied from 0.187 kg/s to 0.272 kg/s and the solution flow rate is varied from 0.053 to 0.115 kg/s. The output parameters, specific moisture change, moisture removal rate, dehumidification effectiveness and latent heat removal capacity varied in following ranges 3-4.2 g/kg of dry air, 2.4-3.1 kg/h, 0.12-0.21 and 1.7-2.1 kW respectively. Particularly when air flow rate increases from 0.187 kg/s to 0.272 kg/s the moisture removal performance improves about 11% whereas when the solution flow rate increases from 0.055 to 0.115 kg/s, improvement in moisture removal performance about 20%. The results imply that increase in solution flow rate always have the positive impact on dehumidification performance. The increase in airflow rate has the negative impact on specific moisture removal and effectiveness, but the impact is positive in case of the moisture removal rate and latent heat removal capacity. The Overall results show a promising dehumidification performance and further improvement is possible by incorporating a cooling system.

Origami Paper-Based Electrochemical (Bio)Sensors: State of the Art and Perspective

In the last 10 years, paper-based electrochemical biosensors have gathered attention from the scientific community for their unique advantages and sustainability vision. The use of papers in the design the electrochemical biosensors confers to these analytical tools several interesting features such as the management of the solution flow without external equipment, the fabrication of reagent-free devices exploiting the porosity of the paper to store the reagents, and the unprecedented capability to detect the target analyte in gas phase without any sampling system. Furthermore, cost-effective fabrication using printing technologies, including wax and screen-printing, combined with the use of this eco-friendly substrate and the possibility of reducing waste management after measuring by the incineration of the sensor, designate these type of sensors as eco-designed analytical tools. Additionally, the foldability feature of the paper has been recently exploited to design and fabricate 3D multifarious biosensors, which are able to detect different target analytes by using enzymes, antibodies, DNA, molecularly imprinted polymers, and cells as biocomponents. Interestingly, the 3D structure has recently boosted the self-powered paper-based biosensors, opening new frontiers in origami devices. This review aims to give an overview of the current state origami paper-based biosensors, pointing out how the foldability of the paper allows for the development of sensitive, selective, and easy-to-use smart and sustainable analytical devices.