Effects Of Mass Fraction Research Articles

Environmentally Friendly, Dual-Responsive Actuator Based on Nafion, Carboxylated Multiwalled Carbon Nanotubes, and Polyethylene.

As a type of smart material, flexible stimulus-responsive actuators have become a hot research topic nowadays. However, flexible actuators responding to a single stimulus source are susceptible to external perturbations, which may lead to an unstable function or even failure. Therefore, in this paper, we proposed a bilayer actuator that can be driven by both humidity and light by combining the humidity-sensitive Nafion, carboxylated multiwalled carbon nanotubes (cMWCNT) with excellent photothermal conversion properties, and commercial polyethylene (PE) tape with good humidity insensitivity and thermal expansion. First, the cMWCNT-Nafion film was prepared by a solution casting method and bonded together with PE tape to obtain a bilayer actuator. Then, the effects of the cMWCNT mass fraction and film thickness on the humidity and light response performance of the bilayer actuator were investigated. The optimal ratios of raw materials were obtained for different stimulation sources, respectively. Furthermore, the performance of the bilayer actuator with the optimal ratios was tested; it was verified that the proposed dual-responsive actuator can realize different degrees of bending deformation under different relative humidity (RH) and ultraviolet (UV) light intensity with good stability. Finally, the application potential in multiple scenarios was further verified by applying the prepared cMWCNT-Nafion/PE bilayer actuator to a smart window, crawling robot, and flexible gripper. This paper will provide a meaningful reference for the development and performance optimization of high-performance dual-responsive actuators.

Supramolecular porous phase change materials for encapsulation of nitrate with amino-expanded graphite by cucurbit[7]uril

The demand for oil and natural gas energy is increasing dramatically, and the extraction of conventional oil and gas reservoirs is in a stage of exhaustion. In order to stabilize the functionalized properties of oil-based drilling fluids (OBDF) during the extraction of oil and gas reservoirs in ultra-deep wells, the present experiments were carried out on the material (EG-NIT/CB[7]) obtained by encapsulating nitrate (NIT) in expanded graphite (EG) with porous structure through the supramolecular self-assembly property of cucurbit[7]uril (CB[7]). The structural properties were analyzed using various analytical tools and the results showed that our material synthesis was successful. And the effect of mass fraction of EG, CB[7] on the heat transfer and storage of EG-NIT and EG-NIT/CB[7] materials was investigated. The increase in mass fraction of EG can increase the thermal conductivity of EG-NIT up to 7.4 times and the introduction of CB[7] further improves the thermal conductivity of EG-NIT/CB[7] by up to 1.38 W/m·k. The latent heat value of EG-NIT/CB[7] decreased by only 4.7% after 200 cycles. Meanwhile, under the condition of 150 °C, adding EG-NIT/CB[7] to drilling fluids can reduce the temperature of drilling fluids by 2.8 °C. And it improves the stability of drilling fluids, the viscosity almost does not change, and it can also play a certain role in inhibiting the leakage of drilling fluids. Therefore, the EG-NIT/CB[7] developed by us can be practically applied in ultra-deep drilling projects.

Energy and exergy analysis of a novel two-stage ejector refrigeration cycle using binary zeotropic mixtures

To improve the ejector refrigeration cycle performance, this paper presents a theoretical thermodynamic analysis of a novel two-stage ejector refrigeration cycle (TSERC) with a gas-liquid separator using R134a/R32 and R600a/R290 as refrigerant. By separating the relatively low-boiling-point and high-boiling-point refrigerants, the cycle compression ratio decreases, the cycle performance increases, and the energy utilization efficiency can be improved. Energy and exergy analysis were conducted for the traditional single-stage ejector refrigeration cycle (SSERC) and TSERC. The effect of the mixture mass fraction on cycle performance under a fixed external heat source operating condition was studied, and the cycle performance comparisons between TSERC and SSERC at different evaporation temperature, condensation temperature and generation temperature were conducted. Results show that for TSERC, the maximum COP values 0.126 and 0.11, the maximum exergy efficiency 4.51 % and 4 % are obtained as the low-boiling-point mass fraction equals 0.6 and 0.4 respectively for R134a/R32 and R600a/R290. It is found that exergy destruction mainly occurs in the low-pressure sub-cycle of TSERC, the top three largest exergy destruction components are ejector 1, condenser 1 and generator 1, while the smallest exergy destruction occurs in pump 2. In addition, cycle performance comparison between SSERC and TSERC shows that the maximum COP improvement increased by 41.6 % and 89.6 % for 134a/R32 and R600a/R290 for TSERC, while the maximum entrainment ratio improvement increased by 32.4 % and 87.6 %. Moreover, it is concluded that the cycle performance improvement of TSERC is more significant at lower evaporation temperature, higher condensation temperature, and lower generation temperature compared to SSERC.

Temperature and composition dependence modeling of viscosity and electrical conductivity of low-activity waste glass melts

The development of models that accurately relate the properties of a glass melt to its temperature and composition is important for glass formulation, melter control, and modeling the melt flow, refractory corrosion, and production rate. Using a database consisting of more than 4,000 data points measured between 900 °C and 1250 °C for over 600 unique low-activity waste glass compositions, we developed models for the melt viscosity and electrical conductivity. Models based on the Gaussian process regression approach outperformed models based on the Vogel–Fulcher–Tammann equation according to four standard metrics and yielded reliable prediction intervals. The models found primarily linear effects between properties and individual components, except for the effect of the Na2O mass fraction on the electrical conductivity. The effects were found to be consistent with current theories on physical processes involved with those properties.

Effect of inlet water vapor mass fraction on flow characteristics in Laval nozzle

Abstract The Laval nozzle is an important component of the supersonic cyclone to achieve the change of gas–liquid two-phase, and the condensation characteristics of the Laval nozzle have an important influence on the separation performance of the supersonic cyclone. In this work, the effect of inlet water vapor mass fraction on the condensation characteristics in the Laval nozzle was investigated using numerical simulation and experimental methods by establishing a three-dimensional numerical model of air-water vapor supersonic condensation flow. The flow field structures in the Laval nozzle under different inlet water vapor mass fractions were investigated, including Mach number, pressure, and temperature and the effects of the inlet water vapor mass fraction on the liquefaction characteristics in the Laval nozzle were investigated. In addition, the droplet distribution in the Laval nozzle were also tested by a particle image velocimetry (PIV) experimental system. The comparison of simulation and experimental results indicates that the numerical model established in this work can effectively describe the real flow situation in the Laval nozzle. The results show that the inlet water vapor mass fraction has a little effect on the flow field structure in the Laval nozzle, and has the significant impact on the water vapor condensation characteristics. With increasing the inlet steam mass fraction from 5 % to 12.5 %, the nucleation rate, droplet number, and separation efficiency in the Laval nozzle increase to 4.05 × 1021 kg−1 s−1, 3.67 × 1014 kg−1, and 79.4 %, respectively, and when further increasing the inlet steam mass fraction to 15 %, these parameters decrease.

Anti-temperature anti-salinity anti-shear C18MAAC / NaAA Amphiphilic Copolymer: Preparation, characterization and properties

For improving the temperature resistance, salt resistance and shear resistance of conventional copolymers, the new hydrophobic monomer C18MAAC was prepared by substitution, then C18MAAC/NaAA amphiphilic dicopolymer was prepared by micellar polymerization. The synthetic parameters were optimized using the single-variable method: reaction temperature 50°C, mass fraction of initiators to the total monomers 0.7 wt%, mass fraction of hydrophobic monomer C18MAAC to NaAA and C18MAAC 2 wt%, and the mass fraction of two monomers 25 wt%. The structure of the C18MAAC and the C18MAAC/NaAA copolymer were characterized, and the morphology of the copolymer was observed. Effect of mass fraction of the copolymer and the salt, temperature, shear rate on viscosity of the aqueous solution were investigated. With the increase of copolymer's mass fraction, the viscosity of the aqueous solution increased slowly first, and the viscosity increases rapidly after reaching 0.4 wt% of copolymer concentration. Therefore, 0.5 wt% concentration of copolymer aqueous solution was selected in the experiment, and the rotor was selected for the rheological performance test. The results showed that the temperature resistance, salt resistance and shear resistance of the copolymer reached 90 °C, 1 wt% salt and 150 s-1 respectively. The C18MAAC/NaAA copolymer/surfactant composite system is very stable in 1wt% salt at 90 °C, and has good synergistic effect to improve the viscosity of the solution, which making it is a promising candidate as an oil-displacing agent.

Effect of sepiolite on the rheological properties of shear thickening fluid and improvement mechanism analysis

To improve the performance of shear thickening fluids (STFs), we propose the addition of fibrous sepiolite. Through macroscopic rheological tests and microscopic characterization, the effects of different sepiolite mass fractions (0 wt%, 1 wt%, 2 wt% and 3 wt%) on the shear thickening of a SiO2-STF system (with a PEG200 dispersion medium) at different ambient temperatures (20 °C, 30 °C, 40 °C and 50 °C) were investigated. Rheological experiments revealed a significant improvement in the shear thickening of SiO2-STF with the addition of sepiolite (Sep/SiO2-STF), with 7.11- and 1.94-fold increases in absolute and relative shear thickening, respectively. As the sepiolite mass fraction increased from 0 wt% to 3 wt%, the temperature sensitivity coefficient decreased from 13.493 to 4.839, indicating that the Sep/SiO2-STF system still exhibited favourable shear thickening at 50 °C. Dynamic oscillatory shear testing revealed that with an increase in sepiolite mass fraction from 0 wt% to 3 wt%, the maximum energy storage modulus, maximum energy dissipation modulus and shear stress increased by 5196.25 %, 1676.16 % and 377.54 %, respectively. Microscopic characterization revealed that sepiolite induced the formation of more clusters in the STF system primarily through the physical adsorption of silica particles and Si–OH on its surface, leading to a significant increase in the shear thickening effect.

Microstructure, corrosive-wear and electrochemical performance of laser cladded NiTi–xAl2O3 coatings in 3.5%NaCl solution

PurposeThe aim of this study is to investigate the effects of Al2O3 mass fraction on the corrosive-wear and electrochemical performance of NiTi coating in 3.5% NaCl solution.Design/methodology/approachThe NiTi–xAl2O3 coatings were fabricated on S355 steel by laser cladding, and their corrosive-wear and electrochemical performance were investigated using a wear tester and electrochemical workstation, respectively.FindingsThe wear rates of NiTi–5%Al2O3, –10%Al2O3 and –15%Al2O3 coatings are 82.33, 54.23 and 30.10 µm3 mm−1 N−1, respectively, showing that the wear resistance of NiTi–15%Al2O3 coating is the best. The wear mechanism is abrasive wear, which is attributed to the increase of coating hardness by the Al2O3 addition. The polarization resistance of NiTi–5%Al2O3, –10%Al2O3 and –15%Al2O3 coatings is 3,639, 5,125 and 10,024 O cm2, respectively, exhibiting that the NiTi–15% Al2O3 coating has the best corrosion resistance.Originality/valueThe roles of Al2O3 in the corrosive-wear and electrochemical performance of NiTi–xAl2O3 coating were revealed through the experimental investigation.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0044/

Adhesive and rheological properties of Polyisobutylene-based adhesives with different white carbon black fillers

Different types of white carbon black (WCB) and polyisobutylene (PIB) were mixed to prepare WCB/PIB-based adhesives, whose adhesive and rheological properties were emphatically studied. The effects of different preparation methods, particle sizes, and different mass fractions of WCB on the performance of adhesives were systematically investigated. According to the results, large particles make the adhesive have better initial viscosity and peel strength at a low mass fraction, while small particles show excellent shear strength and peel strength at a high mass fraction. In addition, WCB was modified with KH570 to improve the dispersibility and compatibility of WCB in the matrix. When the amount of KH570 added was 5 wt% and 10 wt%, the two different adhesives had the best adhesive performance. The modification of WCB increased the shear performance of adhesives by 1–2 times and the initial tack by 1–2 grades.

Microstructure and tribological properties of laser cladded TiC reinforced WC-10Co4Cr coatings at 500 °C

WC-10Co4Cr-xTiC coatings were fabricated on H13 steel by laser cladding to improve their wear resistance. The effects of TiC mass fraction on the friction-wear properties at 500 °C were investigated using a high-temperature wear tester, and the wear mechanism was discussed in detail. The results show that the WC-10Co4Cr-xTiC coatings are composed of WC, W2C, Co3W3C, Cr7C3, and TiC phases, and the porosity is reduced by the addition of TiC. The average coefficients of friction of WC-10Co4Cr-xTiC coatings are increased with the TiC mass fraction; while the wear rates are opposite, showing that the addition of TiC plays a key role in wear resistance. Moreover, the wear mechanism of WC-10Co4Cr-xTiC coatings is primary abrasive wear, slight adhesive wear, and oxidative wear.

Effects of Polyethylene Microplastics on Soil Nutrients and Enzyme Activities

The threat of microplastic pollution in soil ecosystems has caused widespread concern. In order to clarify the effect of polyethylene microplastics on soil properties, a 4-month soil incubation experiment was conducted in this study to investigate the effect of different mass fraction (1 %, 2.5 %, and 5 %) and particle sizes (30 mesh and 100 mesh) of polyethylene microplastics on soil chemical properties, nutrient contents, and enzyme activities. The results showed that:① When the particle size was 100 mesh, microplastics at the mass concentrations of the 2.5 % and 5 % treatments significantly reduced soil pH, and the exposure of polyethylene microplastics had no significant effect on soil conductivity. ② Compared to that in CK, the addition of microplastics reduced soil available potassium, available phosphorus, and nitrate nitrogen to varying degrees. The addition of 100 mesh microplastics significantly increased soil organic matter and ammonium nitrogen. ③ When the particle size was 100 mesh, compared to that in CK, treatments of all concentrations significantly increased soil catalase activity and alkaline phosphatase, showing an increasing but not significant trend, and the 5 % concentration treatment significantly decreased soil sucrase activity. ④ Changes in soil properties were influenced by the addition of microplastics of different concentrations and sizes, with higher concentrations and smaller particle sizes having more significant effects. In conclusion, the effects of microplastics on soil properties were not as pronounced as expected, and future research should focus on the mechanisms involved in the different effects.

Experimental study on Corn Straw Fiber (CSF) toughening EPS concrete

The natural Corn Straw Fiber (CSF), it has the advantages of light weight, high strength, good toughness and renewable, can delay the cracking and improve the toughness of cement-based materials. The effects of different mass fractions of CSF and Expanded-Polystyrene (EPS) particles on the compressive strength, flexural strength, splitting tensile strength and their failure modes, load-displacement curves and toughness of EPS concrete were analyzed by full factorial experimental design method. The compressive toughness index (I0, I1) and fracture energy (Gf) were defined to evaluate the effect of CSF on toughening EPS concrete. The results show that the addition of CSF can improve the compressive strength, flexural strength and cracking toughness of EPS concrete to a certain extent. The maximum compressive strength occurred in the E1F3 specimen with a CSF content of 3 % in Group I, which was 1.12 MPa, and the improvement rate was also the highest among the four groups, reaching 69.7 %. The compressive toughness index I1 also reached its maximum in the E1F3 specimen; The maximum flexural strength occurred in the E3F4 specimen with a 4 % CSF content in Group III, which was 0.885Mpa, with the highest improvement rate of 127.38 %. The maximum fracture energy Gf reached 0.827 in the E3F4 specimen. However, another additive, EPS particles, did not significantly improve the physical and mechanical properties of concrete. According to the SEM images and toughening mechanism analysis, it was discovered that tight adhesion between EPS particles and CSF with cement matrix, and the failure mode of CSF was tensile fracture, which could maximize the effect of CSF high tensile toughness. On the basis of mechanical properties and toughening effect, the relationship formulas between variable factors and strength, toughness index were fitted, and the optimal content of EPS and CSF were determined to be 1.3 % and 3 %, respectively.

Laser cladded Co08–xTi3AlC2 coatings: Microstructure, corrosive–wear and electrochemical corrosion

MAX phase played the positive role during the corrosive–wear process of metal coatings, and Ti3AlC2 was added into Co08 coating by laser cladding to improve its corrosive–wear and electrochemical properties. The effects of Ti3AlC2 mass fraction on the corrosive–wear and electrochemical properties of obtained coatings in 3.5 % NaCl solution were investigated using a reciprocating wear tester and electrochemical workstation, respectively. The results show that the Co08–xTi3AlC2 coatings are composed of Co (Ni, Cr, W, Mo), AlFe and Ti3AlC2 phases, and their hardness is increased with the Ti3AlC2 mass fraction. The average coefficients of friction of Co08–5 %Ti3AlC2, –10 %Ti3AlC2 and –15 %Ti3AlC2 coatings are 0.56, 0.47, and 0.41, respectively, and the corresponding wear rates are 418.99, 389.67, and 339.33 μm3 N−1 s−1, respectively, showing that the Co08–15 %Ti3AlC2 coating has the best friction reduction and wear resistance among the three kinds of coatings. The wear mechanism of Co08–5 %Ti3AlC2, –10 %Ti3AlC2 and –15 %Ti3AlC2 coatings are abrasive wear, adhesive wear, and abrasive wear/adhesive wear, respectively. Moreover, the corrosion resistance of Co08–xTi3AlC2 coatings is increased by the Ti3AlC2 mass fraction, which is attributed to the protection role of corrosion products by the addition of Ti3AlC2.

Microstructure and tribological behaviors of laser cladded CuAlMnTi–xTiC composite coatings at elevated temperature

CuAlMnTi-xTiC composite coatings were prepared on Ti6Al4V alloy by laser cladding to enhance its tribological properties. The effects of TiC mass fraction on the friction–wear properties of CuAlMnTi–xTiC composite coatings at high–temperature were investigated using an ball–on–disc tester. The results show that the grains of CuAlMnTi–xTiC composite coatings are refined by the addition of TiC, and the metallurgical bonding is formed between the coating and the substrate. The hardness of CuAlMnTi–15%TiC composite coating is higher 1.98 times than that of CuAlMnTi coating, in which the TiC as wear–resistant framework prevents micro–cutting to enhance wear resistance. The average coefficients of friction of CuAlMnTi–0%TiC, –5%TiC, –10%TiC and –15% TiC composite coatings in the stable wear period are 0.465, 0.491, 0.514, and 0.587, respectively, and the corresponding wear rates are 116.8, 111.3, 107.8, and 95.4 μm3•N–1•mm–1, respectively, showing that the wear rate is decreased with the increase of TiC mass fraction. The wear mechanism is transferred from adhesive wear to abrasive wear and slight oxidation wear by the addition of TiC, which is attributed to the improvement of hardness by the refined grain strengthening effect of TiC.

Improvement of carbon fiber/phenolic composite properties by low-loading graphene oxide and SiO2 nanoparticles

As an ablative thermal protection material, the mechanical properties and ablative resistance of carbon fiber/phenolic (C-Ph) composite should be improved to meet the high requirements in deep space exploration. Herein, the properties of C-Ph composites were improved by the synergistic effect of low-concentration graphene oxide (GO) solution and low mass fraction of SiO2 nanoparticles. Compared to the unmodified C-Ph composite, the compressive strength of the modified composites was increased by 40.75 % and the linear and mass ablation rates were reduced by 17.78 % and 43.95 %, respectively. The introduction of GO effectively improved the interfacial bonding between the fiber and phenolic resin. Meanwhile, the uniformly dispersed SiO2 nanoparticles resisted the applied loads, thus synergistically enhancing the mechanical properties of the composites. In terms of improving ablation resistance, GO promoted the graphitization of fibers and enhanced the stability of the char layer. Concurrently, SiO2 nanoparticles reacted with the carbon matrix under high temperatures to form ablation-resistant SiC, thus synergistically enhancing the ablative properties of the composite.

Kinetic study of ignition process of ammonia/n‐heptane fuel blends under engine conditions

AbstractPilot‐ignited ammonia‐fueled engines have drawn more and more attention for low carbon emissions compared to traditional diesel engines. The ignition processes of NH3/NC7H16 mixtures under compression ignition engine‐like conditions are numerically investigated. By comparing the ignition delay times (IDTs) calculated by six ammonia mechanisms with experimental data, the Glarborg mechanism is selected. Then, the Glarborg mechanism and the Zhang detailed n‐heptane mechanism are merged into a new mechanism, which is adopted in the present study. Results show that the negative temperature coefficient behavior of the IDTs is only observed as the ammonia mass fraction is 70%. Only temperature has a significant effect on IDTs at all research conditions, and the effect of ammonia mass fraction is significant when the temperature is lower than 1000 K. However, the effects of equivalence ratio and pressure are small, especially at high temperatures, high equivalence ratios, and high pressures. Interestingly, the IDTs are categorized into three regions by temperature and ammonia mass fraction. The sensitivity analysis indicates that the sensitivity coefficients of most reactions associated with ammonia decrease with a decrease in ammonia mass fraction, whereas only R4210 is sensitive to ammonia mass fraction for n‐heptane‐related reactions. Rates of production and consumption (ROP) analyses indicate that the ammonia mass fraction mainly affects the ROPs of NC7H16, NH3, and NNH at low and medium temperatures, whereas the ammonia mass fraction affects the ROP of H2NO before the temperature of 2000 K. The ROPs of NC7H16, NH3, and NNH significantly increase with increasing temperature, whereas the ROP of H2NO slightly increases with increasing temperature. The increase of temperature in the early and middle stages is mainly contributed by the oxidation of n‐heptane, while the increase of temperature in the middle and late stages is mainly contributed by the oxidation of ammonia.

Laser cladded Ni625–xCr3C2 coatings: Microstructure, tribocorrosion and electrochemical properties

Ni625–xCr3C2 coatings were prepared on 45 steel by laser cladding to improve its tribocorrosion and electrochemical property. The microstructure, phases and hardness of obtained coatings were analyzed using a super–depth field microscope, X–ray diffraction, and microhardness tester, respectively, and the effects of Cr3C2 mass fraction on the tribocorrosion and electrochemical properties of Ni625–xCr3C2 coatings in 3.5 % NaCl solution were investigated. The results show that the Ni625–xCr3C2 coatings are mainly composed of γ–Ni, Fe3C, Cr3C2, Mo2C, Cr7C3 and Cr23C6 phases, and their coating hardness increases with the Cr3C2 mass fraction, which are almost three times that of substrate. The coefficients of friction and wear rates of Ni625–5%Cr3C2, −10%Cr3C2 and − 15%Cr3C2 coatings are reduced compared with the Ni625 coating, and the wear mechanism is primary abrasive wear, accompanied with adhesive wear and pitting corrosion. Moreover, the polarization resistance of Ni625–5%Cr3C2, −10%Cr3C2 and − 15%Cr3C2 coatings are higher than that of Ni625 coating, showing that the corrosion resistance of Ni625–10%Cr3C2 coating was the best among the four kinds of coatings.

Experimental study and numerical simulation of water-sand two-phase flow in fracture network

ABSTRACT The flow characteristics of water-sand two-phase in fractured rock mass has an important influence on underground engineering. A series of laboratory experiments are carried out by using a self-made fracture network test system. Based on the Euler-Lagrange method, a numerical simulation study of water-sand two-phase flow is conducted. The effects of sand mass fraction w, sand particle size Φ and combination of inlet and outlet on the flow characteristics of water-sand are systematically analyzed. The results show that the water-sand outflow is directly proportional to the fracture openings, and the growth rate of water-sand outflow is significantly different under multiple inlet-outlets configurations. The final volume proportions of water-sand are 14.1%, 35.9% and 50% respectively. Fluidity I exhibits an inverse correlation with fracture opening, w and Φ. Under the condition of the single inlet and outlet, the minimum fluidity I for 0.6 mm opening is 3.28E–7 m2+ns2- n/kg, the maximum fluidity I for 2.0 mm opening, reaching 3.88E–6 m2+ns2- n/kg. Based on the response surface regression method, a multivariate regression model for three fracture openings was established, boasting exceptional predictive accuracy and reliability. Particle residence time correlates positively with w and Φ. The turbulent kinetic energy k is significantly affected by the fracture opening and decreases with the increase of w and Φ. The variation range of k is 0.38 m2/s2 ~0.63 m2/s2. The results deepen our understanding of the migration behavior of water-sand in the fracture network, and provide a theoretical guidance for groundwater resource protection and other underground engineering.

Effects of Faraday cup deterioration on Sr and Cr isotope analyses by thermal ionization mass spectrometry.

By comparing data from an extensive set of Sr and Cr isotope measurements performed on two different thermal ionization mass spectrometers (TIMS), using three sets of Faraday cups with different usage histories, we assess the effects of Faraday cup deterioration on high-precision isotope measurements by TIMS. We find that dynamic 84Sr/86Sr and 87Sr/86Sr measurements provide stable and reproducible results over the entire 56 months of this study, regardless of which set of Faraday cups is used. By contrast, static 84Sr/86Sr and 87Sr/86Sr measurements lead to deviant results, drifts over time, and in general exhibit larger scatter. For the most part, these differences can be attributed to changing Faraday cup efficiencies. For the instruments of this study we find that the center cup is most affected, consistent with this cup often receiving the highest ion beam intensities during measurements conducted in our laboratory. For Cr isotopes, we find that the correlation between mass fractionation-corrected 53Cr/52Cr and 54Cr/52Cr ratios observed for static measurements in several prior studies also reflects different Faraday cup efficiencies. Again, the changing efficiency of predominantly the center cup can account for the observed drift and correlation in 53Cr/52Cr and 54Cr/52Cr. Multi-static Cr isotope measurements reduce this drift, but still result in a residual correlation between the two ratios, suggesting this correlation in part also reflects unaccounted mass fractionation effects.

Experimental investigation of water vapor condensation from flue gas in different rows of a heat exchanger model

Condensing heat exchangers (HE) are used in many applications because of their usability with different fluids and a wide operating range in terms of pressure, temperature and power. Despite that, the thermal design of condensing heat exchangers is still not optimized, due to the complexity of the condensation process and lack of related research.This paper presents results of experimental investigations of biofuel flue gas water vapor condensation on vertical tubes in different rows of a tube bundle in a crossflow. The effects of water vapor mass fraction, inlet flue gas temperature and the Reynolds number on heat transfer when the inlet cooling water temperature and flow rate are constant were analyzed. The results obtained showed that the main parameters which had the most influence on the condensation process were the water vapor mass fraction in the flue gas and its temperature at the inlet to the test section. In the range of inlet flue gas Reynolds numbers investigated, the Re effect on heat transfer was not as significant as the effect of the parameters indicated above. However, the Re number had some influence on the heat transfer variation along the inline tube bundle. A comparison of the average Nu number in the case of dry air with the experimentally determined average Nu number, even with low condensable gas mass fraction (6 %), showed that it increased considerably. A correlation was proposed, which helps to determine the average Nu number for the heat exchanger in the range of experiments performed.