This work explores for the first time bump-on-tail (BOT) instability excited by energetic electrons in helicon plasma. The Berk-Breizman model that developed for the wave-particle interaction and resulted instability in magnetic fusion is used. Details of the BOT instability are computed referring to typical helicon discharge conditions. Parameter studies are also conducted to reveal the effects of collisionality and energetic drive, to account for high-pressure and high-power senarios respectively. It is found that under the HXHM (high magnetic field helicon experiment) experimental parameters, the disturbed distribution function oscillates explosively at the initial stage of BOT instability excitation, and the wave frequency shift does not appear, i.e., the steady-state solution always exists under this mode. In the process of restoring stability, the exchange of energetic particles and wave energy is concurrent with the change of wave amplitude. As the Krook operator increases (i.e., from 0.1 to 1), the saturation level of the electric field and the instability enhance. Additionally, there have a bigger disturbance for the initial EEDF (electron energy distribution function) in high-power helicon devices, so that the energy exchange between waves and energetic particles is stronger as well. Moreover, BOT instability effects the density and flux of bulk plasma, and the flux increases with the Krook operator. The effect of BOT instability is one order of magnitude larger on rotating plasma than that on stationary plasma.These findings present a full picture of BOT instability in helicon plasma and are valuable to controlling it for efficient and safe applications, e.g., high-power space plasma propulsion and plasma material interactions using helicon source.

To reuse low-temperature wasted heat as a thermal resource for high temperature, a direct-contact adsorption thermal storage was focused using humid air and zeolite 13X particles as the working fluid and adsorbent, respectively. Only a few previous studies have chosen the working fluid in gaseous form because it is unavailable for latent heat in generating heat sources. Recovering waste heat in humid air to generate hotter steam is unique and becomes an originality of our present work. The time required to regenerate zeolite particles and the maximum temperature of the generated steam were investigated assuming a warm-up device for a vehicle. The time required to regenerate zeolite was investigated by changing the dew point, temperature, and superficial velocity of the inlet humid air. It was mainly affected by the temperature of the inlet air. The absorbent was regenerated within 30 min when the humid air preheated to 200 degrees C was supplied. On the other hand, the maximum steam temperature was investigated by changing the superficial velocity and temperature of saturated inlet humid air. As one of the significant and novel finding in this work, the steam of >200 degrees C was obtained as a high-temperature heat source even with saturated humid air unavailable latent heat. Moreover, as theoretical knowledge, it was revealed that the maximum temperature of the heat source can be estimated by the relationship between the heat balance on the packed bed and adsorption equilibrium.

Although adsorption heat pump systems consist of adsorption and regeneration processes, almost no re-ported work has investigated regeneration in detail for a packed bed of zeolite particles. Here, we con-ducted experimental and theoretical analyses on the effects of temperature, dew point, and the flow velocity of high-temperature moist air on the regeneration rate. Normal superficial velocities of 0.108, 0.216, and 0432 mN/s, and inlet temperatures of 140 and 200 degrees C with various dew point temperatures were examined. Originally, the purpose was to make saturated steam of 180 degrees C or higher from factory waste heat of 100 degrees C or lower. Regeneration of the zeolite particle layer with high-temperature moist air was analyzed with respect to the effect of air conditions. Numerical simulations of zeolite energy stor-age were performed using a one-dimensional adsorbent regeneration model. Practical applications of the numerical model were also examined. A sufficient regeneration rate was obtained by raising the temper-ature, even when environmental air was used. Significant improvements were obtained at a 0.432-mN/s normal superficial velocity and a 200 degrees C inlet temperature. In the particle layer containing only adsorbed water, dew point effects on the regeneration rate and temperature response were small at high temper-atures. In the particle layer containing both adsorbed and free water, the effect of the dew point on the regeneration rate was also small. The heat pump efficiency decreased because of the increased dew point; however, the decrease in efficiency was mitigated by increasing the temperature.(c) 2022 Elsevier Ltd. All rights reserved.

This work investigated the generation of high-temperature steam by feeding saturated moist air through a steam generation system containing a zeolite 13X packed bed. The use of moist air was a unique aspect, which demonstrated a novel approach to steam generation system design. The issue with the steam generation system in previously existing published research works is that it needs high regeneration energy. In order to solve this issue, it is desirable to employ moist air as the working medium. In order to better understand the physical processes involved, numerical modeling of zeolite energy storage was also performed in addition to the exper-imental work. As the result, when the temperature of the moist air was raised from 30 to 95 degrees C, the maximum temperature of the resulting water vapor reached to about 200 degrees C. The maximum temperature of the water vapor was not greatly affected by the superficial velocity of the moist air between 0.108 and 0.216 mN/s. In the case that the moist air temperature was high, the maximum temperature of water vapor could be predicted based on correlations between the heat balance and adsorption equilibrium, assuming that temperatures of the moist air and zeolite were identical. The numerical technique also included a comparison between Arrhenius and linear driving force models. At higher temperature input moist air, both models resulted the close tendency.

Selenium and its compounds in high concentration are toxic for humans, especially selenate (VI) is the most toxic due to its high solubility in water. To promote the reductive reaction of Se(vi) to Se(iv) or Se(0), which is relatively easy to remove in water, noble metal particles were added as reaction sites with a reductant. The highest removal performance of selenate in aqueous solution was achieved using rhodium particles supported on TiO2 (Rh/TiO2). Selenate was rapidly reduced with hydrazine on the metal particle, leading to a selenium deposition on the particle inhibiting the stable reductive reaction. On the other hand, when a weaker reductant such as formaldehyde was used for the selenate reduction, the selenium deposition was suppressed due to its low reactivity, resulting in a stable reductive reaction of selenate in water.

About 60% of the energy input in the chemical industry is discarded from the plant. Energy saving can be achieved in the entire plant by recovering these waste heats and reusing them as power and heat sources in the power plant. An adsorption heat pump has been developed for the purpose of regeneration of such unused energy. In this study, saturated humid air was supplied to a device packed with 13X zeolite particles of 4 mm in diameter. The time variation of temperature in the apparatus was measured experimentally. Then, the maximum temperature was estimated from the relationship between heat balance and adsorption equilibrium. The trend of the maximum temperature calculated from the heat balance is consistent with experiment. Further, it was found from the result of the heat balance equation that the sensible heat of the humid air supplied and the heat of adsorption of the zeolite are mainly distributed to the sensible heat of the zeolite. In the future, it is important to make effective use of the sensible heat of this zeolite. In order to extract more thermal energy from the device, it is necessary to improve the heat transfer between the packed bed and medium. A double pipe heat exchanger having a zeolite packed bed on the annular side was proposed as an apparatus. Flow direction of the humid air supplied to device was changed in two different ways. The one of them is supplying humid air radial flowly to the device and another is supplying the air in parallel flow. The influence of flow direction on heat transfer between packed bed and medium is studied with numerical simulation.

In printed electronics, uniform and solute film formation by the inkjet method is very important. This study aims to clarify the relationship between Marangoni convection generated by adding surfactant and thinning of solute film. First, four types of surfactants were added one by one to the anisole-polystyrene solution with varying concentrations, and then a little amount of fluorescent polymer was added as tracer to each solution. Next, each solution was dropped on a hydrophilic substrate with a droplet diameter of 80 micrometers using an inkjet method, and the flow in the evaporation process and the shape of the solute film after drying were observed. As a result, Marangoni convection occurred when any surfactant was added at a certain concentration or more, and the solute film after drying of the droplets to which two kinds of surfactants were added became thin and approached a uniform shape. In addition, the measurement of surface tension showed that the visualized flow is the Marangoni convection.

In a water-cooled rotary stoker combustor (WRC) used in industrial waste treatment, the effect of the preheating temperature of the combustion air on clinker generation and the concentrations of lead, zinc, and chromium in the incineration residue was examined. First, the temperatures and gas components in the WRC were measured. It was confirmed that the vapor phase temperature rises rapidly near the WRC outlet when the combustion air temperature is room temperature, whereas this rapid rise is eliminated when the combustion air temperature is 180 degrees C. By eliminating the high temperature field and forming a relatively mild combustion field, the interval between occurrences of clinker trouble at the combustion air temperature of 180 degrees C could be extended to about twice that at room temperature. Next, the mass balance of ash, lead, zinc, and chromium in the waste throughout the process was examined, and reasonable results were obtained. Comparison of the concentrations of the three heavy metals in the incineration residue and fly ash further revealed increasing migration of the metals from waste to fly ash with increasing preheated air temperature. This was explained in relation to the measured temperature distribution in the WRC.

Incineration is one of the most common methods for the treatment of industrial waste. Large amounts of bottom ash are buried without being reused. By reducing components such as toxic metals contained in bottom ash under suitable incineration conditions, landfill waste can be reduced, and re-use of bottom ash can be increased. In this study, effects of the air supplied to the bottom of a commercialy used rotary stoker furnace was investigated as the first step to improve incineration conditions. Bottom ash content must be controlled against various types of industrial waste whose content changes from day to day. The characteristics of industrial waste containing typical components were numerically investigated using a combustion simulation program. It was found that if the primary air used for combustion is not preheated, auxiliary fuel is required to burn waste. Preheated primary air increases the drying rate of the input material, and allows burning of waste without auxiliary fuel. At the furnace, components and calorific values of input raw material are controlled by mixing different types of waste together. Preheated primary air enables reduction of bottom ash, reduction of auxiliary fuel consumption, and stabilization of furnace operation.

インクジェット液滴から生成する膜形状は，乾燥工程におけるバルク流れに支配される。そのバルク流れを発生させる三つの要因を表面変形の観点から解説する。その因子の一つであるマランゴニ対流は膜形状を制御するために重要な役割をもつ。そこで，マランゴニ対流の制御方法を説明した後，それを利用したいくつかの実験を紹介する。

Adsorptive heat transformer is a promising technology for waster heat recovery and global energy conservation. A novel cyclic adsorption heating system based on direct contact heat exchange method has been established for the purpose of high-temperature steam generation from hot water. Pre-adsorption is originally proposed before generation phase to enhance the system performance with composite zeolite 13X and MgSO4 in the open-loop adsorption heating system. Composite zeolite is prepared by impregnation method. Experimental results show steam with temperature higher than 200 degrees C is generated from inlet water at 72.0 degrees C. During regeneration phase, dry air at 130 degrees C and relative humidity of 7.37% is employed. Gross temperature lift is 95.0 degrees C to 103 degrees C for different pre-adsorption conditions. The effective steam generation time with pre-adsorption temperature at 90.0 degrees C is prolonged by 27.4%. Meanwhile, the mass of steam is elevated by 16.2% compared with the cycle without pre-adsorption. Exergy coefficient of performance is upgraded by 14.7% and specific heating power for steam generation is increased by 16.0%. The pre-adsorption operation achieved the goal of recovery of low-grade waste steam on adsorbents to enhance the subsequent high-temperature steam generation. After pre-adsorption operation, the packed bed reaches adsorption and thermal equilibrium more quickly during generation phase. Thus, dynamic steam generation is significantly intensified and then system performance is improved correspondingly.

High-temperature steam generation in adsorption heat pump with composite zeolite-CaCl2 has been experimentally investigated by introducing heat and mass recovery. A direct contact heat exchange method is utilized to enhance the overall heat transfer rate. Composite zeolite (CZ) is prepared by immersing zeolite particle in CaCl2 solution at mass concentration of 40%. Cyclic experiment consists of two processes: regeneration with 130 degrees C dry air and steam generation with 80 degrees C hot water. The heat and mass recovery with steam below 90 degrees C is added before generation process. Mass of generated steam above 200 degrees C is increased by 9.12%. The effective time for steam generation is dramatically extended by 18.33%. Adsorption and thermal equilibriums inside the packed bed are achieved more quickly with heat and mass recovery. Gross temperature lift for one-stage adsorption heat pump is above 100 degrees C. Coefficient of performance for heating (COPh) and specific heat power (SHP) are elevated by 9.55% and 9.23%, respectively. The increase in mass of generated steam contributes to the improvement of COPh. Meanwhile, only a short time used for heat and mass recovery enables the rise in SHP.

A mathematical model describing the drying behavior of solution droplets deposited on a substrate is numerically solved to predict the morphology of the formed solid layer. The model includes the fluid dynamics, heat transfer, and mass transfer, and also considers wettability of the substrate and deformation of the free surface. The calculated morphologies of solid fllms agree reasonably with those formed experimentally from polystyrene/anisole solution droplets. The model predicts drying behavior that has not been previously reported. First, when a coffee ring is formed, solutal Marangoni forces deform the free surface while the solvent fully remains. Second, the deformation yields an outward bulk flow, enhancing solute transport toward the edge. Third, the effect of droplet size on the receding distance is related to the deformation. Consequently, the effects of droplet size, surface tension, viscosity, evaporation rate and wettability on film morphology can be explained by the deformation behavior.

Shear thickening is an intriguing phenomenon in the fields of chemical engineering and rheology because it originates from complex situations with experimental and numerical measurements. This paper presents results from the numerical modeling of the particle-fluid dynamics of a two-dimensional mixture of colloidal particles immersed in a fluid. Our results reveal the characteristic particle behavior with an application of a shear force to the upper part of the fluid domain. By combining the lattice Boltzmann and discrete element methods with the calculation of the lubrication forces when particles approach or recede from each other, this study aims to reveal the behavior of the suspension, specifically shear thickening. The results show that the calculated suspension viscosity is in good agreement with the experimental results. Results describing the particle deviation, diffusivity, concentration, and contact numbers are also demonstrated.

High-temperature adsorptive heat transformer for steam generation has been experimentally investigated by introducing composite zeolite/CaCl2-water working pair based on a direct contact method. Composite adsorbents are prepared by immersing zeolite into different mass concentrations of CaCl2 solutions. SEM (Scanning Electron Microscope) is used to observe the surface structure of the composite zeolite. XRF (X-Ray Fluorescence) is selected to analyze the element mass ratios in adsorbents. BET (Brunauer-Emmett-Teller models) is employed to calculate the pore characteristic of pores inside zeolite. Characterization results confirm the success of preparation for composite zeolite. Adsorption properties including equilibrium water uptake and integral adsorption heat are measured for basic evaluation. Overall volumetric adsorption heat is increased by 13.1% for CA40% (immersion of zeolite in CaCl2 solution concentration at 40%) compared with that for 13X. Cyclic experiments are conducted to test the design of system. Superheated steam above 200 degrees C is generated for 13X and different composite zeolites from hot water below 80 degrees C. Dry gas at 130 degrees C is used for regeneration. Gross temperature lift is more than 100 degrees C for single stage zeolite adsorptive heat transformer. Dynamic steam generation on interface between water and zeolite is enhanced with more heat released by using composite zeolite. Subsequently, adsorption equilibrium is easier to be achieved inside the whole range of the packed bed. Effective time ratio for steam generation is elevated by 18.6% for CA40% compared with that for 13X. Mass of generated steam is raised by 12.9% simultaneously. Both the time and mass of generated steam have been obviously promoted with the increase of CaCl2 impregnated in zeolite. COPex (Exergy Coefficient of Performance) is kept constant while SHP (Specific Heating Power for steam generation) is increased by 12.6%.

Aggregates of carbon black with various shapes in a suspension were investigated to understand their behavior in fluid flow. At a lower aspect ratio, the particles exhibited tumbling or rotational motion, and the fluid flow was deflected in regions where the density of particles was higher. The contact between the particles promoted partial particle grouping when the aspect ratios of the particles were low. The average transitional motion of the particles was greatest at the lowest aspect ratio case. This led to weaker rearrangement event than those when the particles were nearly spherical. The elongated particles could act as bridges to promote the formation of particle groups. We believe that our study provides insight for suspensions containing particles with various shapes, which can be used to control the suspensions rheologically.

The performance of steam generators to generate high-temperature steam using waste heat from industrial processes was investigated. Two types of steam generators were constructed. One is a bench-scale cylindrical generator having similar structure to the laboratory-scale reactor used in the authors previous research. The other is a scaled-up generator whose flow passage area is extended to store a large amount of adsorbent for further scale-up on practical application. Temperature measurements in the bench-scale generator in the atmospheric steam generation process showed that a high-temperature region is formed above the water level due to adsorption of water vapor, while a low-temperature region below saturation temperature is formed below the water level. The mass of steam generated per unit mass of adsorbent increased with increasing energy supplied from the regeneration air and approached an asymptotic value depending on the temperature of the regeneration air. The mass of steam generated per unit mass of adsorbent increased with decreasing heat capacity of the generator.

The increase in temperature, reduction in partial pressure, reduction in concentration, purging with an inert fluid, and displacement with a more strongly adsorbing species are the basic things that occur in the practical method of desorption. In this study, dry gas at constant temperature and pressure was employed as the aid to reduce the partial pressure in the water desorption on the zeolite 13X. The objective of this study is to confirm the feasibility of desorption using dry gas experimentally and numerically. The implication of heat and mass transfers were numerically investigated to find the most influential. The results of numerical simulation agree with the experimental ones for the distribution of local temperature and average water adsorbed in the packed bed.