Solution Mass Concentration Research Articles

Various Types of Light Guides for Use in Lossy Mode Resonance-Based Sensors

A comparative study of figure-of-merit fiber sensors of the mass concentration of NaCl solutions based on single-mode and multi-mode fibers was carried out. Lossy mode resonance is realized on chemically thinned sections of optical fibers to various diameters (from 26 to 100 μm) coated with ZnTe. Thin-film coatings were applied using the method of metalorganic chemical vapor deposition (MOCVD). Samples of single-mode and multi-mode fiber sensors were created in such a way that the depth and spectral position of resonances in aqueous NaCl solutions coincided. Sensors implemented on a single-mode fiber have a higher sensitivity (5930 nm/refractive index unit (RIU)) compared to those on a multi-mode fiber (4860 nm/RIU) and a smaller half-width of the resonance in the transmission spectrum. According to the results of experiments, figure-of-merit sensors are in the range of refractive indices of 1.33–1.35 for: multi-mode fiber—25 RIU−1, single-mode fiber—75 RIU−1. The sensitivity of the resulting sensors depends on the surface roughness of the ZnTe coating. The roughness of films synthesized on a single-mode fiber is four times higher than this parameter for a coating on a multi-mode fiber. For the first time, in the transmission spectrum during the synthesis of a thin-film coating on a multi-mode fiber, the possibility of separating the first nine orders of resonances into electric and magnetic transverse components has been demonstrated. The characteristics of sensors with the operating wavelength range in the visible (500–750 nm) and infrared (1350–1550 nm) regions of the spectrum are compared. The characteristics of multi-mode lossy mode resonance sensors are demonstrated, which make them more promising for use in applied devices than for laboratory research.

Liquid desiccant-based deep dehumidifier working with a novel ionic liquid: Prediction model and performance comparison

Deep dehumidification system with energy conservation and stable operation is expected to be used in industrial occasions with low-humidity environment. Compared with solid desiccant dehumidification, liquid desiccant-based dehumidification is a promising alternative because of its advantages of continuous operation and low regeneration temperature. However, corrosion and crystallization problems exist with liquid desiccant-based deep dehumidifier (LDDD) using salt solutions. In this work, LDDD using a novel ionic liquid (IL) was introduced, and the heat and moisture transfer model was established based on the finite difference method. Meanwhile, the moisture transfer characteristics were numerically simulated under different operating parameters (i.e., inlet humidity ratio wa,in, air velocity va, solution mass concentration X, solution temperature ts and solution volume flow Vs). Besides, the significance of various factors and their interactions were analyzed based on response surface methodology. The numerical model is validated against the experiment of the LDDD test bench with a relative deviation of 3%-8%. Numerical results show that the LDDD using IL can achieve deep air dehumidification, and outlet humidity ratio of less than 4 g/kgda is possible. In particular, the order of significance for influencing factors of outlet humidity ratio is: wa,in > X > ts > va > Vs. Moreover, it is found that dehumidification rate of 60% LiBr solution (saturated state) is less than that of 90% IL. This study establishes a prediction model of moisture transfer between IL and air under the coupling of multiple physical fields, and provides guidance for the application of LDDD using ILs.

Performance improvement of NH3–H2O absorption chiller with a combined generator

The present experimental work investigates the impact of an innovative falling-film and plate combined generator, associating vapor production and purification, on the performance of an NH3–H2O absorption chiller of 5-kW cooling capacity. The impact of the flooding of the lower part of the exchanger on the performance of the machine is investigated: It decreases the COP by 33% and cooling capacity by 38%. Solution sub-cooling at the combined generator inlet improves the purity of the ammonia vapor produced, but degrades the performance of the chiller. A design of experiments is defined to characterize the performance of the combined generator, which is highly impacted by the solution mass flowrate and concentration. Then, two correlation forms are used to predict the performance, and the adapted NTU model yields better results. Finally, for an air-conditioning application, a low solution mass flowrate allows the energy consumption to be reduced by approximately 15% but it requires a higher temperature for the heat source; while the increase in the solution mass flowrate degrades the performance but enables the machine to self-regulate at a low heat source.

Acoustically induced birefringence in polymer aqueous solutions: The case of polyvinyl alcohol

Transient and stationary ultrasonically induced birefringence traces of various relatively dilute poly-vinyl alcohol aqueous solutions were measured over a range 500–1400 kHz of ultrasonic frequencies and 0.02–0.13 W/cm2 of acoustic field amplitudes. The intrinsic value of the stationary birefringence for all polymer solutions investigated in this study was found to be proportional to the solution mass concentration, the square root of the ultrasonic intensity and the frequency of the ultrasound in agreement with theoretical predictions. Systematic analysis of the transient birefringence signals caused by the applied ultrasonic field has been performed in order to evaluate the orientational relaxation times from the viewpoint of dynamics of polymer chain orientation and anisotropy changes in polarizability. The results are discussed in the context of recent experimental studies and theoretical predictions of the ultrasonically induced birefringence in terms of transport phenomena.

Adsorption, separation, and purification of cyclosporine A using reversed-phase liquid chromatography

环孢素A(cyclosporine A, CsA)是由11个氨基酸组成的中性环状多肽,是临床拮抗器官和组织移植后排异反应的首选药物。高效液相色谱法广泛应用于CsA的分离分析,开展CsA色谱行为的研究是使用制备高效液相色谱纯化CsA的关键。该文首先在C18固定相上比较了CsA在甲醇-水和乙腈-水两种流动相体系中的保留行为,结果表明其保留时间对有机相比例变化比较敏感。控制甲醇比例在84%~88%,或者乙腈比例在75%~85%, CsA的保留因子(k)在3~7范围内。考察了上样量对CsA峰形的影响。随着上样量增加,在两种流动相体系中,CsA的峰形都由对称开始变得拖尾,保留时间前移。因此在进行CsA纯化时,需要特别注意前杂的去除情况。然后采用吸附等温线描述CsA的保留行为,当流动相中CsA的质量浓度较低时,有机相比例对溶质在固定相上的吸附量影响并不明显。随着溶质的质量浓度增加至0.5 g/L以上,有机相比例降低有助于提高CsA在固定相上的吸附量。和甲醇-水体系相比,在乙腈-水体系中固定相对溶质有更大的吸附容量。用模型对CsA的等温吸附曲线拟合,在甲醇-水体系中符合Langmuir模型,在乙腈-水体系中为Moreau模型。由模型参数可知在两种体系下,CsA在C18固定相上均为单层吸附,区别在于乙腈-水体系中CsA会产生较大的分子间作用力。最后,实验采用0~60 min 65%~75%乙腈、60~80 min 75%乙腈的条件开展了环孢素A纯化的探索实验,可将CsA的杂质控制在0.2%以下。本研究结果对采用制备高效液相色谱纯化CsA具有指导意义。

Technical Analysis of Enhanced Oil Recovery by Polymer Flooding

Polymer flooding is one of the effective technologies to improve oil recovery. This paper briefly introduces the mechanism of polymer flooding, and describes the application advantages of polymer flooding in heavy oil sandstone reservoirs in China. Combined with the application practice of polymer flooding EOR technology, the scheme of polymer flooding EOR technology is further explored from the aspects of polymer flooding oil supply, polymer flooding oil injection mode and polymer solution mass concentration, hoping to provide some references for the improvement of reservoir recovery.

Computational Fluid Dynamics Modeling of Hollow Membrane Filtration for Concentration Polarization

Based on CFD and film theory, filtration’s two-dimensional CFD model of the hollow membrane was established by integrating the mass transformation and the hydrodynamic transportation. Parameters of concentration polarization in the membrane channel (i.e., solute mass concentration, concentration polarization factors, and concentration polarization layer thickness) were estimated under different hydraulic conditions. In addition, the algorithm for the thickness of the concentration polarization layer has been improved. The results showed that decreasing the feed Reynolds number or increasing the transmembrane pressure can enhance the concentration polarization phenomena. Concentration polarization parameters increased sharply at the initial place (X/H < 25, where H is the entrance width, X is the distance from entrance) and then flatten out (X/H > 25) along the membrane channel; solute concentration and concentration polarization factors were arranged in a U-shape in the membrane channel’s cross-section. The improved algorithm could match well with cross section data, δ2H at X/H = 1, 25, and 200 are 0.038, 0.11, and 0.25, respectively, which can reasonably reflect the distribution of the concentration polarization phenomenon in the membrane channel.

Variational multiscale stabilized finite element analysis of non-Newtonian Casson fluid flow model fully coupled with Transport equation with variable diffusion coefficients

This paper presents a new subgrid multiscale stabilized formulation for non-Newtonian Casson fluid flow model tightly coupled with variable diffusion coefficients Advection–Diffusion–Reaction equation (VADR). Both the subscales are chosen to be time dependent and the stabilized formulation has been reached through the complete elimination of the unresolvable scales in terms of the coarse scale solution. Hence the resultant formulation emerges as a set of equations involving only the coarse scale solution instead of multiple scales and makes the formulation simpler to handle. In this study the shear-rate dependent Casson viscosity coefficient is assumed to be a function of the solute mass concentration, resulting in a two way coupling. This paper investigates the stability and the convergence properties of the stabilized finite element solution, without imposing any additional regularity condition other than the admissible space requirement on it. The proposed expressions of the stabilization parameters play a significant role in obtaining optimal order of convergences. During various theoretical derivations the estimations of the non-linear apparent viscosity coefficient have been carefully carried out assuming sufficiently regular exact solution. The performance of the scheme has been numerically validated with lid driven cavity problem. The theoretically established rate of convergence results are appropriately verified through numerical studies. In addition the transient Casson fluid flow behavior in a flow past square cylinder has been analyzed thoroughly.

Luminescence measurements: reference materials for composition of sodium adenosine triphosphate aqueous solution

The authors evaluated the possibility of using the luminometry method which allows checking the level of sanitation and hygiene in industries and is one of the most effective methods of «rapid microbiology». Such key stages of development of reference material for sodium adenosine triphosphate with the certified values as analysis of similar reference materials, selection of source material of the reference material, conducting experimental studies, and establishing the metrological characteristics of reference material with traceability to state primary measurement standard were provided in the paper. Considering that the selective optical density at the characteristic wavelength is directly proportional to the concentration of the absorbing component (sodium adenosine triphosphate), the stability of R M was studied by spectrophotometry. The stability of the RM material to assess the uncertainty of the measurement results was carried out by the isochronous method. The result of the study is the possibility of ensuring the traceability of measurement results based on luminescence to primary measurement standard by sodium adenosine triphosphate concentration. In addition to the above, the authors selected the optimal value of that concentration and established metrological properties for GSO 11606-2020 R M for the composition of sodium adenosine triphosphate aqueous solution (mass concentration: from 0,09 to 0,11 g/dm3; extended uncertainty: 0,015 g/dm3). Usage of this CRM in performing tests, calibrations, and verification of measuring instruments allows providing the unbiased assessment of the measuring capabilities of luminescent measuring instruments, including in terms of determining the error of the measurements carried out.

A comparative study of bubble formation characteristics in non-Newtonian and high-viscosity Newtonian fluids by a laser image technique

A laser image measurement system has been established to study the problem of dynamic bubble formation from a submerged orifice in two kinds of high-viscous fluids, namely Newtonian glycerol aqueous solution and non-Newtonian carboxymethylcellulose (CMC) aqueous solutions. The bubble generation process was measured accurately by means of He-Ne laser as light source using the beam expanding and light amplification technology. The whole formation process, including bubble expansion, stretching and detachment three stages, and the dynamic characteristics of each stage, were investigated experimentally by analyzing comparatively the evolution of the instantaneous shape, volume, surface area, and deformation rate in both fluids. The influences of solution mass concentration, gas chamber volume and orifice diameter on bubble detached volume were discussed respectively, and the results reveals that bubble begins to grow spherically due to the predominant role of surface tension, and then is elongated gradually owing to the increasing buoyancy force. Compared with Newtonian fluid, bubble formed in non-Newtonian fluid presents a slim shape as a result of the shear-thinning effect of CMC solution. Bubble detachment volume in both kinds of fluids increases with solution mass concentration and gas chamber volume, but declines with orifice inner diameter, respectively.

Effects of Water Management on Soil Properties and Cd Behavior of Typical Paddy Soils

To explore the effects of water management mode on Cd environmental behavior in different parent-material-developed paddy soils, two parent-material-developed paddy soils (yellow clayey soil and granitic sandy soil) under three exogenous Cd levels (0.5, 2.0, and 5.0 mg·kg-1) with different water management modes (long-term flooding, moistening irrigation, and wet-dry rotation) were cultured in this study. The soil redox potential (Eh value), pH value, Cd concentration in soil solution, and Cd fractionation were also determined. The results showed that water management mode had different effects on the pH and Eh values of soils developed from different parent materials. The change rates of soil pH value were as follows:long-term flooding:-2.61% (yellow clayey soil), 2.25% (granitic sandy soil); alternation of dry and wet:-1.96% (yellow clayey soil); 0.52% (granitic sandy soil); wet irrigation:-4.08% (yellow clayey soil) and -0.52% (granitic sandy soil). The Eh value of the soils was negatively correlated with the pH value. The influence pattern of water management model on Cd mass concentration of soil solutions in two parent-material soils was consistent. The Cd mass concentration of soil solutions in granitic sandy soil was higher than that in yellow clayey soil. The mean values of Cd concentration were 1.03 μg·L-1 for yellow clayey soil and 1.07 μg·L-1 for granitic sandy soil. Water management mode had no significant effect on the proportions of organic bound Cd or Fe-Mn bound Cd in two different parent-material-developed soils. The long-term flooding mode promoted the transformation of exogenous Cd to residual Cd, and this promotion in yellow clayey soil was higher than that in granitic sandy soil. In conclusion, during the process of regulating soil Cd bioavailability through water management, the role of soil parent materials needs to be considered.

Thermodynamic analysis and performance optimization of the supercritical carbon dioxide Brayton cycle combined with the Kalina cycle for waste heat recovery from a marine low-speed diesel engine

With the continuous rise in world oil prices and increasing environmental awareness, how to improve ship energy efficiency and reduce ship pollution emissions has become a common concern of the shipping industry. Waste heat recovery technology is an effective method to improve the fuel economy of ships and help the future ships to meet the increasingly stringent Energy Efficiency Design Index of the International Maritime Organization. Under the thermodynamic analysis results of the 8S90ME-C10.2 low-speed marine diesel engine, this paper proposed a waste heat recovery scheme that combined the supercritical carbon dioxide Brayton cycle power generation system with the Kalina cycle power generation system. According to the energy and exergy balances of the combined cycle system, a MATLAB program based on the REFPROP database was established. With the application of control variate method, the influence of the key operating parameters including the main compressor inlet temperature, the turbine inlet temperature, the main compressor outlet pressure, the expander inlet pressure, and the ammonia solution mass concentration on the system performance was thoroughly analyzed. Moreover, the multi-objective optimization matching between the diesel engine and the combined power generation system was carried out from the viewpoints of the thermodynamic performance and economic performance and the impact of the system on the fuel economy and the Energy Efficiency Design Index of the ship was calculated. The results showed that the combined power generation system was used to recycle the waste heat of diesel engine exhaust gas and bypass exhaust gas to generate electricity, which reduced the annual fuel consumption and the Energy Efficiency Design Index to 16.62% and 15.01%, respectively. Finally, this study provides a reference for researchers to study the combined use of supercritical carbon dioxide Brayton cycle and Kalina cycle to recycle the waste heat of the marine diesel engine.

Numerical study on the heat and mass transfer characteristics of the open-type cross-flow heat-source tower at low ambient temperature

The heat-source tower heat pump (HTHP) has the advantage in preventing frosting and efficiently absorbing heat from the air in winter. Due to the low air humidity in low temperature environment (less than 0 °C), the latent heat exchange between the antifreeze solution and air is a key factor affecting the performance of HTHP. In this paper, a mathematical prediction model is established to investigate the heat and mass transfer characteristics of the heat-source tower (HST) in low temperature environment. It is found that the air temperature can be lower than the corresponding solution temperature in certain areas of HST when the inlet air-solution temperature difference is very small. Under the condition of the average heat transfer temperature difference of 5 °C, there is no significant reduction in the heat transfer when the ambient temperature drops from 0 °C to −15 °C, and the latent heat ratio is 25% and 50% at the ambient temperature of −15 °C and 0 °C respectively. The relationships between the optimum liquid-to-gas ratio of HST and the operation parameters of air and solution are also studied. The results show that air temperature, solution temperature and solution mass concentration have influences on the optimal liquid-to-gas ratio, whereas air relative humidity has no effect. This paper concludes that the latent heat has a significant impact on the heat transfer. A great amount of heat can be transferred from the air to the solution in HST by adjusting and optimizing the operation parameters in low temperature environment.

Existence of normalized solutions for nonlinear fractional Schrödinger equations with trapping potentials

AbstractIn this paper, we study the existence, nonexistence and mass concentration of L2-normalized solutions for nonlinear fractional Schrödinger equations. Comparingwith the Schrödinger equation, we encounter some new challenges due to the nonlocal nature of the fractional Laplacian. We first prove that the optimal embedding constant for the fractional Gagliardo–Nirenberg–Sobolev inequality can be expressed by exact form, which improves the results of [17, 18]. By doing this, we then establish the existence and nonexistence of L2-normalized solutions for this equation. Finally, under a certain type of trapping potentials, by using some delicate energy estimates we present a detailed analysis of the concentration behavior of L2-normalized solutions in the mass critical case.

Experimental characterisation of a novel adiabatic membrane-based micro-absorber using H2O-LiBr

In the interest of reducing the size of absorption chillers, a novel adiabatic membrane-based micro-absorber prototype is experimentally studied. Water–lithium bromide solution is used as the working fluid flowing through 50 rectangular microchannels of 0.15 mm height, 3 mm width and 58 mm length. In the present study, a laminated microporous PTFE membrane of 0.45 µm pore diameter, separating the solution from the vapour, is tested. It incorporates a supporting layer of polypropylene. Different operating parameters were tested, including the inlet solution mass flow rate, temperature and concentration and the pressure potential for absorption. The measured concentration and temperature of the solution at the absorber outlet are used to evaluate the mass transfer characteristics of the micro-absorber. It is demonstrated that the process is controlled by the solution mass transfer resistance. Calculated results of the absorption rate and the absorption ratio show the advantages of the proposed design considering its compactness. The cooling power of a hypothetical chiller equipped with the tested micro-absorber of 73.7 cm3 effective volume, for the range of variables considered in this study, is 41 W. The modular configuration of the absorber allows to easily scale-up the cooling capacity.

The minimum in-line coalescence height of bubbles in non-Newtonian fluid

The minimum in-line coalescence height of bubbles generated from a submerged nozzle was investigated experimentally in shear thinning non-Newtonian fluid at lower Reynolds number (2∼60). Carboxymethyl cellulose sodium (CMC) aqueous solution and carbon dioxide were used as the liquid phase and the gas phase, respectively. The process of the formation, movement and in-line coalescence of bubbles was visualized and recorded by a high-speed digital camera. The influences of bubble size, bubble generation frequency and liquid property on the minimum in-line coalescence height of bubbles were investigated by changing nozzle diameter, gas flow rate and the mass concentration of CMC aqueous solutions. For a given liquid, the generating frequency and size of bubbles increased but the minimum coalescence height of in-line bubbles decreased when the nozzle diameter and gas flow rate were increased. When the nozzle diameter and gas flow rate were fixed, the shear-thinning effect of CMC aqueous solution became stronger with increasing CMC mass concentration, which led to the increase in both the terminal rise velocity and average acceleration of the trailing bubble, consequently, the minimum in-line coalescence height of bubbles decreased. An empirical correlation for estimating the minimum in-line bubble coalescence height was proposed, the calculating values accords well with experimental data with a mean relative deviation only 7.6%.

Efficient mixing of yield-pseudoplastic fluids at low Reynolds numbers in the chaotic SMX static mixer

Complex rheology of non-Newtonian fluids often leads to non-homogenous mixing due to the spatial viscosity gradients. The non-intrusive electrical resistance tomography (ERT) technique was employed to study the mixing of non-Newtonian fluids in a chaotic SMX static mixer. For the first time, the effect of the rheology of the yield-pseudoplastic fluids on the quality of distributive mixing was explored in this study. The non-Newtonian fluid used in this study was the xanthan gum solution, which is a yield-pseudoplastic fluid obeying the Herschel-Bulkley model and its rheological parameters change as the solution mass concentration increases. The tomography images were utilized to investigate the efficacy of the distributive mixing of two different types of the secondary streams (Newtonian and non-Newtonian) in the primary stream of xanthan gum solutions (0.5wt%, 1.0wt%, and 1.5wt%). Experiments were conducted for three different primary flow rates ranging from 3.5L/min to 12.5L/min while keeping the center-line injection of secondary stream fixed at 100mL/min for all experiments. Our results revealed that the Newtonian secondary stream favored effective axial mixing over the non-Newtonian secondary stream. However, interestingly, for both types of the secondary streams, a more effective radial mixing was observed as the xanthan gum mass concentration increased at low Reynolds numbers.

Study on the Performance of Heat and Mass Transfer of Cross Flow Dehumidifier in an Industrial Plant

Liquid desiccant air conditioning (LDAC) system has been more and more widely used in some commercial and industrial buildings which require a relative lower humidity ratio of supply air. This paper mainly focuses on the investigation of the dehumidification performance of a cross-flow dehumidifier for an industrial plant. The theoretical model of the cross-flow dehumidifier is established based on the energy and mass conservation. The numerical solutions are obtained according to the finite difference method within the MATLAB environment. The influences of the different operation parameters and the dehumidifier geometric size on the dehumidification performance are analyzed and discussed for various operation conditions. The results show that the solution mass concentration has the most critical effect on the dehumidification performance, follows by the solution mass flow rate and air mass flow rate. The air temperature has little influence on the performance.

Bubble formation in shear-thinning fluids: Laser image measurement and a novel correlation for detached volume

A laser image system has been established to quantify the characteristics of growing bubbles in quiescent shear-thinning fluids. Bubble formation mechanism was investigated by comparing the evolutions of bubble instantaneous shape, volume and surface area in two shear-thinning liquids with those in Newtonian liquid. The effects of solution mass concentration, gas chamber volume and orifice diameter on bubble detachment volume are discussed. By dimensional analysis, a single bubble volume detached within a moderate gas flowrate range was developed as a function of Reynolds number ,Re, Weber number, We, and gas chamber number, Vc, based on the orifice diameter. The results reveal that the generated bubble presents a slim shape due to the shear-thinning effect of the fluid. Bubble detachment volume increases with the solution mass concentration, gas chamber volume and orifice diameter. The results predicted by the present correlation agree better with the experimental data than the previous ones within the range of this paper.

Experimental evaluation of a liquid desiccant air conditioning system for tri-generation/waste-heat-driven applications

The paper aims to evaluate the application of liquid desiccant air conditioning technology in the development of efficient and effective tri-generation/waste heat driven system applications, in particular with regard to solid oxide fuel cell (SOFC) technology. Using operational thermal input values typical of a SOFC combined heat and power (CHP) system, the paper’s evaluation validates the concept of integrating SOFC and liquid desiccant air conditioning technology into an efficient and effective first-of-its-kind tri-generation system. This is due to good dehumidification capacity and effective regeneration of a potassium formate solution at a 0.65-0.7 solution mass concentration. Conclusions of the paper’s evaluation include: (1) effective instantaneous balancing of the dehumidifier and regenerator across a range of environmental and operational values, (2) operation of the dehumidifier is dictated, to some degree by the available thermal energy (CHP prime mover, process heat), (3) encouraging thermal COP values, for a system of this scale, in the range of 0.4-0.66 are achievable with a low grade thermal input (45-60°C) typical of a SOFC CHP system, and (4) potential for non-synchronous operation in a tri-generation system context, bringing about improvements to peak cooling output and total system efficiency.