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Stepwise electrocatalysis can remarkably accelerate the kinetics of two consecutive reactions in sulfur electrochemistry. However, the significant difference between the catalysis and diffusion rates of polysulfides results in persistent shuttling in the stepwise electrocatalysts. Here, a stepwise electrocatalytic strategy of catalysis‐immobilization‐deposition is proposed for achieving the consistency of diffusion and catalysis of polysulfides. Accordingly, a sandwich‐like stepwise electrocatalyst is designed, which is composed of Co nanoparticles (Co‐NP), mesoporous SiO2, and iron single atom (Fe‐SA) (denoted as Co‐NP@SiO2@Fe‐SA), serving as catalysis core, immobilization interlayer, and deposition shell, respectively. Benefitting from the dynamic equilibrium between production and consumption of polysulfides achieved by the spatial synergistic effect of the triple sites, the S/Co‐NP@SiO2@Fe‐SA cathode delivers a high reversible capacity of 731 mAh g−1 over 500 cycles at 1 C with a small capacity decay of 0.039% per cycle. Moreover, a high areal capacity of 3.8 mAh cm−2 at a sulfur loading of 4.5 mg cm−2 is achieved with a low electrolyte/sulfur ratio of 5.9. This work sheds light on a new host design concept with high catalytic activity, stability, and selectivity to enable high performance lithium‐sulfur batteries. [ABSTRACT FROM AUTHOR]

In many aeronautics and marine applications, the unsteady forces generated by propulsion rotors due to turbulence ingestion are a significant source of noise and create serious concerns. The understanding of rotor turbulence ingestion and the rotor noise generation mechanisms is vital to achieve an optimal design or apply noise control strategy. The current study is the first attempt to numerically investigate an underwater rotor ingesting grid-generated turbulence by large eddy simulation combined with the Ffowcs-Williams and Hawkings equation. The flow characteristics of two directly simulated turbulence grids with a mesh spacing of 4 and 6 in. are investigated and proved to be adequate for the rotor turbulence ingestion study. The simulated unsteady force spectra of the rotor show better agreement with the experimental results in terms of amplitudes and frequency ranges of the first haystack and broadband components compared to previous theoretical and numerical studies. The unsteady forces and noise of the rotor downstream of the 4-in. grid are slightly higher than those downstream of the 6-in. grid. A far-field noise prediction approach based on the time derivatives of the rotor axial and radial unsteady forces are investigated and validated. The far-field noise spectra and the rotor noise directivities predicted by the time derivative approach agree well with the Ffowcs-Williams and Hawkings equation in the main frequency range of underwater rotor noise. The noise directivities are found to be dominated by axial force related dipole sources. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) have become an important research topic due to their wide range of applications and potential to meet the future air transportation demands. In many configurations of UAVs, the rotors interact with the wake of upstream bodies, which is of pivotal importance to the aerodynamic and aeroacoustic performance. The studies of flow structures and noise sources for rotors interacting with adjacent upstream bodies at Reynolds numbers lower than 105, which is the operating condition of most small UAVs, are limited. In the current study, numerical simulations are conducted to investigate the interaction between a rotor and the wake of an airfoil at low Reynolds numbers around 104 using the Spalart–Allmaras delayed detached eddy simulation method and acoustic analogy based on Farassat's formulation 1 A. The results show that the axial forces and the surface pressure perturbations of the airfoil are closely coupled with the rotor rotation. The effect of interaction on the rotor blades depends on the relative angle of attack. Furthermore, an analysis of the surface pressure fluctuations corresponding to the noise sources shows that the tonal noise at the blade passing frequency and its harmonics is mainly caused by periodical interaction, and the high-frequency noise is produced by the shedding vortex at the trailing edge of the rotor. [ABSTRACT FROM AUTHOR]

Slurry mixing is a key process in the production of lithium-ion batteries. The interphase mass transfer and refinement problems involved in the shear mixing process have important engineering significance and research value. In this study, a CFD-DEM numerical simulation method is constructed for high shear flow, which based on the internal frictional momentum transfer mechanism and liquid-solid traction. The reliability of the proposed model was verified by single particle settling and particle cluster entry cases, and the computational results showed that the proposed model was in good agreement with the analytical results and literature. High Shear Mixer (HSM) as a typical multiphase shear equipment. We apply the developed multiphase shear flow model to study the effect of its operating conditions on the mixing and mass transfer performance. The results show that the appropriate rotation speed can effectively reduce the local accumulation of solid-phase particles, but the width of the inner shear zone is not related to the stator rotation speed; the shear jet forms a local circulation in the stator gap and reduces the through-flow capacity; the shearing effect of the inner shear zone is obvious for the declustering of large particle clusters, and the particle collision plays a certain role in the early stage of declustering. The CFD-DEM model developed in this paper improves the accuracy of interphase trajectory capture and provides a reliable numerical simulation method for the study of multiphase shear flow. • A multiphase flow computing framework for high shear environment is proposed. • The correctness of the proposed multiphase shear calculation model is verified. • The gas-liquid-solid shear mixing performance of HSM is investigated. • Analyzed the internal declustering characteristics of HSM. [ABSTRACT FROM AUTHOR]

This study is aimed at identifying potential molecular mechanisms and candidate biomarkers in the left atrial regions for the diagnosis and treatment of valvular atrial fibrillation (VAF). Multibioinformatics methods, including linear models for microarray analysis (LIMMA), an SVA algorithm, CIBERSORT immune infiltration, and DNA methylation analysis, were employed. In addition, the protein-protein interaction (PPI) network, Gene Ontology (GO), and molecular pathways of differentially expressed genes (DEGs) or differential methylation regions were constructed. In all, compared with the normal rhythm group, 243 different mRNAs (29 downregulated and 214 upregulated) and 26 different lncRNAs (3 downregulated and 23 upregulated) were detected in the left atrium (LA) of atrial fibrillation (AF) patients, and the neutrophil and CD8+ T cell were infiltrated. Additionally, 199 different methylation sites (107 downregulated and 92 upregulated) were also identified based on DNA methylation analysis. After integration, ELOVL2, CCR2, and WEE1 were detected for differentially methylated and differentially transcribed genes. Among them, WEE1 was also a core gene identified by the competing endogenous RNA (ceRNA) network that included WEE1-KRBOX1-AS1-hsa-miR-17-5p, in VAF left atrial tissue. We combined the DNA methylation and transcriptional expression differential analysis and found that WEE1 (cg13365543) may well be a candidate gene regulated by DNA methylation modification. Moreover, KRBOX1-AS1 and WEE1 can compete endogenously and may mediate myocardial tissue infiltration into CD8+ T cells and participate in the AF process. [ABSTRACT FROM AUTHOR]

Soft abrasive flow (SAF) finishing has advantages in precise processing for titaniferous alloy parts with large-area surfaces. However, the processing efficiency and surface quality of current SAF methods require to be improved. To address the issues, a novel gas–liquid-solid three-phase rotary abrasive flow polishing method (RGLSP) is proposed based on the microbubble cavitation effect. Referring to the energy conservation principles of bubbles group movement, an improved realizable k-ε turbulence model is set up. Based on the above model, a mechanical dynamic model of the machining apparatus is established to obtain the flow field distribution of different structural parameters. The simulated results show that the pitch-down angle determines the distribution of the rotary flow field, and an optimized processing apparatus is developed. The machining experiments show that the proposed RGLSP method can improve the machining efficiency by 60%, and the surface roughness can reach Ra 0.1 μm with lower surface defects. The RGLSP can provide an important reference direction for low-carbon emission processing. [ABSTRACT FROM AUTHOR]

Although many patents have introduced the principle of bypass downlink system for automatic drilling, and the downlink systems have been used to communicate from the surface equipment to the bottom-hole-assembly (BHA) for thousands of meters, there are few literature reports of propagation theory of the downlink telemetry. In order to increase the transmission rate of downlink system, it is necessary to study mathematical model of the downlink communication channel. In this paper, a frequency-domain model of the downlink communication for the bypass downlink system is established based on the transfer matrix method, which describes the relationships between the transmitted flow rate pulses from the downlink equipment on the surface and the received voltage signals from downhole turbine generator, and can be used to predict downhole signal waveform. The prediction result is compared to that of the method of characteristic (MOC) algorithm and validated by the experiments. Simulation and experimental results show that the proposed model is correct and feasible. [ABSTRACT FROM AUTHOR]

Mud pulse generators have been widely used for the real-time transmission of valuable directional and formation data from downholes with depths of thousands of meters. There have been numerous studies on the design of mud pulse generators in which the pressure waves were typically nonsinusoidal. Sinusoidal waves provide improved long-distance data transmission and signal noise suppression compared with nonsinusoidal waves. Although sinusoidal pressure wave generators have been studied in the published literature, the influence of the risks of clogging on the design of the generator for producing sinusoidal pressure waves has rarely been considered. To generate sinusoidal pressure waves and to reduce the risks of clogging, a mathematical model for the design of a sinusoidal pressure wave generator is developed in this paper. The effects of the axial and radial clearances between the rotor and stator on the design of the generator are considered in the model. An optimum design method for the generator is provided by combining the developed model and a computational fluid dynamics analysis. Finally, an experimental platform was built and experiments at frequencies 2 Hz and 10 Hz were conducted to validate the design result. The simulation and experimental results show that the optimized pressure waves closely approximate sine waves. Therefore, the developed mathematical model and optimization approach can be used to design a sinusoidal pressure wave generator. [ABSTRACT FROM AUTHOR]

A novel combustion gas and steam mixture cycle (GSMC) power generation system was simulated and studied in this paper. The system integrates the technologies of NG/O 2 combustion, energy storage, peak-shaving and CO 2 capture with LNG/LO 2 cold energy utilization, which has remarkable features such as high efficiency, low first/operation/maintenance costs, zero CO 2 and NO x emission and massive off-peak power shifting. A calculation case is presented and the impacts of turbine inlet parameters, condensing pressure/condenser outlet temperature and feedwater temperature on the net electric efficiency excluding ASU and equivalent net electric efficiency as well as CO 2 capture features are analyzed. The steam content in vapor phase of the condenser outlet is considered which requires more cooling capacity for CO 2 capture. Under the conditions that the condenser outlet temperature/condensing pressure is 30 °C/30 kPa and feedwater temperature is 300 °C, with fully CO 2 capture, the net electric efficiency excluding ASU and equivalent net electric efficiency are 0.4386 and 0.4105 respectively with turbine inlet parameters of 600 °C/30 MPa, and they can reach 0.5327 and 0.5046 respectively with turbine inlet parameters of 1000 °C/40 MPa. [ABSTRACT FROM AUTHOR]

A two-dimension two phase flow model was established to simulate the falling film flow of LiBr solution on a horizontal hydrophilic tube with different solution sprinkle density and tube surface wettability, and the latter has been an overlook factor. The transient characteristics of solution spreading as well as steady film thickness were analyzed. The results show that a continuous film can only be obtained at sufficiently greater sprinkle density with real surface wettability, the liquid coverage of tube surface increases with the increase of sprinkle density or the decrease of static contact angle. The obvious asymmetric distributions of film thickness and film velocity over the horizontal tube surface are demonstrated in a steady state. The thinnest film thickness or maximum film velocity takes place at circumferential angle around 120°. A modified Nusselt equation for predicting the film thickness is suggested and verified by available both simulation and experimental data. [ABSTRACT FROM AUTHOR]

Transition metal oxides@carbon(C) nanocomposites with hierarchical three-dimensional (3D) core-shell nanoarchitectures, large surface area and high electrical conductivity as anode materials for lithium ion batteries (LIBs) are very desirable. Herein, we developed a simple and feasible route to fabricate novel hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres with well-defined hollow microstructures via one-step carbonization of Zn/Fe-metal organic frameworks for the first time. The as-prepared hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres were carefully characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, thermogravimetric analysis, N 2 adsorption/desorption isotherm, transmission electron microscopy and electrochemical techniques. The results showed ultrafine ZnO and ZnFe 2 O 4 nanocrystals were uniformly encapsulated by few carbon layers which was derived from in-situ carbonization of the organic ligands. Benefiting from their special hollow nanoarchitectures, ultrafine ZnO and ZnFe 2 O 4 nanocrystals encapsulated by a few carbon layers, large specific surface area and high electrical conductivity, the hierarchical 3D ball-in-ball ZnO/ZnFe 2 O 4 @C nanospheres presented high reversible capacities of 1283 and 1100 mA h g −1 after first 100 cycles and the following 100 cycles at current density of 100 and 200 mA g −1 , respectively. A high specific capacity of 155 mA h g −1 was obtained at relatively large current rates of 20 A g −1 . [ABSTRACT FROM AUTHOR]

Inferior specific capacity and sluggish redox kinetics are the most stubborn problems lithium-ion and lithium-sulfur batteries (LIBs and LSBs) are facing, respectively. Here we report a facile fabrication of self-supported hollow Co 3 O 4 @carbon nanotubes on carbon cloth (H-Co 3 O 4 @CNT/CC) through a mild pyrolysis-oxidation process. The additive- and binder-free H-Co 3 O 4 @CNT/CC shows excellent electrochemical performances as both LIBs and LSBs electrodes. As a robust integrated anode for LIBs, the areal capacities are 2.72 mAh cm−2 at the current density of 0.5 C over 1000 cycles. While as a durable cathode host for LSBs, favorable areal capacities of 2.37 mAh cm−2 are maintained with a low capacity decay of 0.11 % per cycle at the sulfur loading of 6 mg cm−2 and current density of 1 C after 400 cycles. Electrochemical technology, ex situ Raman spectroscopy and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC via thermodynamics and kinetics. It is demonstrated that the hierarchically hollow interior structure, strong adsorb ability of Co 3 O 4 toward polysulfides and three-dimensional (3D) inter-connected conductive carbon framework are responsible for the high areal capacity, fast redox kinetics and cycling durability. [Display omitted] • The integrated electrode possesses the merits of hollow nanostructured Co 3 O 4 and 3D inter-connected conductive network. • Electrochemical technology and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC. • H-Co 3 O 4 @CNT/CC delivers high areal capacities of 2.72 mAh cm-2 after 1000 cycles at 0.5 C as anode. [ABSTRACT FROM AUTHOR]

The sensitive detection of dipicolinic acid (DPA) as an excellent biomarker of Bacillus anthracis , especially through visual point-of-care testing, is significant for accurate and rapid diagnosis of anthrax to timely prevent anthrax disease or biological terrorist attack. Herein, an acoustofluidics-based colorimetric platform with the integrated ratiometric fluorescence probe (INT-probe) was fabricated, which improved the sensitivity of visual detection for DPA and overcame the poor reproducibility of the existing acoustofluidics-assisted colorimetric analysis. For the design of INT-probe, Eu3+-EDTA complex as sensing moiety was grafted onto the surface of blue organosilane-functionalized carbon dots (SiCDs)-doped SiO 2 nanoparticles (NPs). Upon exposure to DPA, Eu3+ was sensitized by DPA to emit red luminescence, while the SiCDs as reference inside the SiO 2 NPs still kept the blue fluorescence unchanged. Attributed to the acoustic radiation force-driven enrichment of the INT-probe, slight color changes caused by low concentration of DPA could be amplified and distinguished by naked-eyes/smartphone. With the increase of DPA concentration, obvious color variations of INT-probe/DPA aggregates from blue to pink could be observed, and the color information of the fluorescent aggregates was converted to red, green and blue values for quantitative analysis, whose lowest detectable concentration reached 100 nM that is about 2–3 orders of magnitude lower than the infectious dosage of Bacillus anthracis spores (60 μM). Importantly, benefiting from the great color signal enhancement by acoustofluidic sensing platform, the usage of Eu3+ reduced to as low as 0.273 μmol per gram of SiO 2 NPs, providing a meaningful way to utilize lanthanide resource efficiently. [ABSTRACT FROM AUTHOR]

[Display omitted] • The b-SiCDs covalently bind in SiO 2 NPs to exhibit strong internal standard robustness. • The triple-emission probe is constructed by two ratiometric fluorescent composite NPs. • The probe shows more profuse and wider color variations using two-step response strategy. • Sensitivity for colorimetric assay of Hb is further improved by acoustofluidic technology. • RGB values got by chromaticity analysis APP are used for accurate Hb quantification. Acoustofluidics-assisted colorimetric method, a promising point-of-care test (POCT) strategy, has been applied in convenient detection of target molecules using the sensing nanomaterials, but remains a formidable challenge to design fluorescent probe with profuse color evolution, realizing sensitive, simple and accurate determination of analyte. Here, a novel triple-emission fluorescent probe is constructed through a simple blend of two ratiometric fluorescent probes (blue-organosilane-polymerized carbon dots@SiO 2 nanoparticles@red-CdTe/CdS quantum dots (b@SiO 2 @r) and blue-organosilane-polymerized carbon dots@SiO 2 nanoparticles@green-CdTe/CdS quantum dots (b@SiO 2 @g)) at the optimized volume ratio of 11:8. As signal reporters of the triple-emission probe, outer modified "r" and "g" will be quenched in sequence by target via two-step response strategy while the inner "b" as internal standard remains constant. When acoustic field is applied, the effect of acoustofluidics-based nanoparticles concentration makes triple-emission probe aggregate completely, accompanying fluorescence color signal being enhanced, sensitivity of colorimetric assay being improved and multicolor-variation (from orange to dark-goldenrod to dark-olive-green to sea-green to dark-cyan to final steel-blue) with the increase of analyte amount. For POCT demonstration, hemoglobin (Hb) is used as a model target and the captured fluorescence photos of triple-emission probe aggregates are analyzed by a chromaticity analysis application on the smartphone to calculate the red, green and blue values, which are used for accurate Hb quantification with the limit of detection of 1.99 mg/L. Whole test is finished within ∼12 min. The acoustofluidics-manipulated triple-emission probe biosensing strategy has also been applied to the rapid and visual quantitative detection of Hb in human blood. [ABSTRACT FROM AUTHOR]

The vertical condensers have advantages of small occupation area, convenient in assemble or dismantle tube bundle and simple structure etc. However, the low heat transfer performance limits their applications. To enhance the heat transfer, a novel type of vertical condensers was designed by introducing trisection helical baffles with liquid dams and gaps for facilitating condensate drainage. Four configurations of vertical condensers with trisection helical baffle are experimentally studied and compared to a traditional segment baffle condenser. The enhancement ratio of trisection helical baffle schemes is about 1.5–2.5 and the heat transfer coefficient of the dual-thread trisection helical baffle scheme is superior to that of the single-thread one by about 19%. Assistant by the theoretical study, the experimental data is simulated and the condensation enhancement mechanisms by applying trisection helical baffle in vertical condenser are summarized as condensate drainage, short tube construct and reduce steam dead zone functions of the helical baffles. [ABSTRACT FROM AUTHOR]

In this work, we demonstrated an accessible and facile method to prepare hierarchically porous carbon (HPC)/Co 3 O 4 nanocomposites (HPCC). Biomaterials-derived HPC was used as the appropriate carrier to load Co 3 O 4 nanoparticles due to its hierarchically porous structure and high surface area of 163 m 2 g −1 . The HPCC nanocomposites were used as an anode material for lithium-ion batteries (LIBs) and showed good electrochemical performance, delivering an initial discharge of 1566 and charge capacity of 1314 mA h g −1 with a initial coulombic efficiency of 83.9%. Additionally, it could still maintain a high reversible capacity of 1215 mA h g −1 after 100 cycles at a specific current of 100 mA g −1 , which is much better than that of HPC, and Co 3 O 4 and some Co 3 O 4 -based nanocomposites. The good electrochemical performance was mainly attributed to the good distribution of small Co 3 O 4 on HPC, the high surface area and hierarchical pores of HPC to effectively load a number of small Co 3 O 4 , alleviate the severe volume expansion during cycling and improve the electrical conductivity of nanocomposites, and the synergistic effects from the HPC and Co 3 O 4 . Therefore, the HPCC nanocomposites were expected to be an advanced anode material for LIBs. [ABSTRACT FROM AUTHOR]

Hollow nitrogen (N)-doped Fe 3 O 4 /carbon (C) nanocages with hierarchical porosities have been successfully synthesized by carbonizing polydopamine (PDA)-coated Prussian blue (PB). Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and N 2 adsorption/desorption isotherms were employed to characterize the hollow N-doped Fe 3 O 4 /C superstructures. Owing to their well-defined hierarchical porous structure and high electric conductivity originated from N-doped carbon matrix, the unique hollow nanocages as anode materials for Lithium ion batteries (LIBs) exhibited a specific capacity of 878.7 mA h g −1 after 200 cycles at the specific current of 200 mA g −1 , which is much better than that of N-doped Fe 3 O 4 /C derived from pure PB (merely 547 mA h g −1 ). The novel construction with hollow interior nanoarchitecture, hierarchical porosity, high electrical conductivity, N-doped carbon, and the Fe 3 O 4 nanoparticles incorporated into porous interconnected carbon framework make the special nanocomposites be very promising Fe 3 O 4 -based anode materials. [ABSTRACT FROM AUTHOR]

Periodic pressure waves propagating in drilling fluids along the wellbore are widely used to transmit the downhole information through the drillstring. Although various evaluation models for the wellbore and periodic pipe flows have been studied in published literature, the influence of the frequency and multi-boundary conditions on these models for the non-Newtonian drilling fluid is rarely considered. The paper presents a one-dimensional equivalent model to simulate the propagation of the periodic pressure waves in drilling fluids along the wellbore based on the assumption that the system is isothermal and the internal diameter of drillstring is a constant value. Specially, the periodic pressure waves are divided into low-frequency part (such as pump-on pulse) and high-frequency part (such as pressure wave generated by mud pulse telemetry system). The interactions of these two parts with the turbulence and Bingham fluid are investigated based on the Navier–Stokes equation for a 2D axisymmetric transient flow subjected to the five boundary conditions including the pump, air chamber, mud pulse telemetry system, drill bit and the outlet. A finite difference method with second-order accuracy is used to solve the numerical model. Experiments in the shallow and deep wells are conducted to validate the model. The simulated results are in good agreement with the experiment measurement. Finally, the influence of the frequency on pressure wave attenuation is analyzed and the result is compared with those calculated from acoustic attenuation formula. Both results show consistent trend with increasing frequency. [ABSTRACT FROM AUTHOR]

In this work, the self-assembled nanostructures of chitosan on mica surface formed from various solvents were investigated by using atomic force microscopy. The effects of various factors on the self-assembled nanostructures of chitosan on mica surface, including solvents, the concentration of chitosan, the pH of solution and the drying temperature, were explored in detail. Our experimental data resulted in the conclusion that chitosan molecules could self-assemble on mica surface to form various nanostructures such as nanoparticles, fibril and film. Nanoparticles were always formed on mica surface from CCl 4 , C 6 H 6 , CH 2 Cl 2 solution, fibril preferred to form on mica surface from CH 3 CH 2 OH and CH 3 OH solution and the optimal solvent to form film was found to be CH 3 CN. Low concentration, pH and temperature were helpful for the formation of nanoparticles, medium concentration, pH and temperature resulted in fibril and high concentration, pH and temperature were often beneficial to forming chitosan films. The study of self-assembled nanostructures of chitosan on mica surface would provide new insight into the development of chitosan-based load-bearing materials. [ABSTRACT FROM AUTHOR]

The search of advanced anodes has been an important way to satisfy the ever-growing demands on high rate performance lithium-ion batteries (LIBs). It was observed that the capacity of Fe 3 C as an anode is larger than its theoretical one, which might be attributed to the pseudocapacity on the interface between the carbide and electrolyte. In this work, a novel carbon sphere doped with Fe 3 C nanoparticles was fabricated and tested as the anode in LIBs. In the first place, iron precursors were embedded in the cross-link polymer resorcinol-formaldehyde (RF) spheres via a facile hydrothermal reaction, in which RF served as the carbon source and ethanol as a dispersant agent. Consequently, the hydrothermal products were carbonized successively at 700 °C under inert atmosphere to obtain porous carbon spheres doped with Fe 3 C. When the composite severed as an anode in LIBs, its discharge capacity increased to the largest during the first 250-400 cycles, then dropped down to a similar level of that after 1000 cycles at different current rates. The discharge capacity of the composite increased from ∼300 mAh g −1 to ∼540 mAh g −1 at the current of 100 mA g −1 during the initial hundreds cycles, and even a discharge capacity of ∼230 mAh g −1 at the current of 2000 mA g −1 . Moreover, it was observed that a discharge plateau gradually appeared between 0.7∼1.1 V during the first hundreds of cycles. The electrochemical behaviors of the anode before 1000 discharge/charge cycles were compared with that after 1000 discharge/charge cycles by cyclic voltammetry and electrochemical impedance spectroscopy to find out the differences between their features. The high rate performance of LIBs might result from the decomposition of electrolyte and the pseudocapacity behavior presented on the interfacial (surface) lithium storage of the active materials. [ABSTRACT FROM AUTHOR]

For enhancing the vapour absorption in LiBr solution systems, a novel absorber with tube and mesh packing alternating structure is designed and investigated. Stainless steel mesh screens are folded as the longitudinal trough mesh packing, and inserted to the gaps of horizontal tubes to make the absorbent flow through the tube and mesh packing regimes successively, thus forming an alternating heat and mass transfer absorption process. Experimental investigation is conducted to characterize the absorption performance of the absorption bodies of this alternating structure and conventional horizontal coils. The results show that the average mass transfer rate and cooling load are increased by 17.2% and 6.23% respectively, which confirms that the alternating structures can promote the absorption. The mesh packing provides extended absorption area, slows down the flow and well mingles the solution, which are all beneficial for vapour absorption. [ABSTRACT FROM AUTHOR]

The widely used fin-and-tube heat exchangers have a low air-side heat transfer capacity. Enhancing the air-side thermo-hydraulic performance is a key point of the relevant research. Vortex generators have been proven to be one of the most promising techniques to improve the air-side heat transfer capacity of the fin-and-tube heat exchangers. Herein, this paper proposed an original sinusoidal wavy winglet type vortex generator to achieve high heat transfer performance with moderate increased pressure drop penalty. A three-dimensional numerical simulation was conducted to explore the air-side thermo-hydraulic performance with Reynolds number ranging from 1027 to 2054. The longitudinal vortex is generated in the channel so as to enhance the intensify of convective heat transfer. Especially, the wave-shaped vortex generators can produce many local small-scale secondary flows. And it is confirmed that the frontal area of the vortex generator can be effectively extended by such wavy shape and a more intensified disturbance can be caused in the air-side. Furthermore, the effects of the attack angle (α), dimensionless height (H p) and especially arrange position of the vortex generator were investigated. Additionally, the ranges of the Nusselt number ratio, friction factor ratio and surafece goodness factor in this study are 1.09–1.52, 1.09–2.31, and 1.06–1.24, respectively. Moreover, it is also very crucial to evalute the grade of energy and to explore the irreversible loss druing the heat tranfer process in view of the second law of thermodynamics. And the thermal dissipation can be reduced by up to 5.85% compared with the plain fins from the perspective of exergy analysis. [ABSTRACT FROM AUTHOR]

In this work, we propose the using of a transient acoustic imaging technique to analyze blade-vortex interaction (BVI) noise, which is considered as one of the dominant noise sources from rotorcraft. A simplified but representative set-up with a two-bladed rotor in the presence of a moving flow is considered herein. First, we conducted a delayed detached-eddy simulation to reveal the associated flow physics and to identify the distinctive flow structures during the BVI process. The numerical analysis complements the physical understanding gained from the following acoustical imaging analysis, where a recently developed phase-averaged wavelet-based beamforming method in the time-frequency domain is adopted. Compared to transient flow structures, which have been visualized in the numerical study, the acoustic imaging results clearly demonstrate the transient analysis capability of the proposed approach. It is impossible to achieve such a transient analysis capability by simply using the classical beamforming method. In particular, the transient analysis shows that the dominant noise sources would move along the blade in the radial direction, by essentially following the corresponding BVI positions on the blade, which is also consistent with the numerical results. Overall, the proposed method can help achieve a deepened physical understanding of transient aerodynamic and aeroacoustic process and could find applications in low-noise rotorcraft designs. [ABSTRACT FROM AUTHOR]

In recent decades, the Timed Elastic Band (TEB) algorithm is widely used for the AGV local path panning because of its convenient and efficiency. However, it may make a local detour when encountering a curve turn and cause excessive energy consumption. To solve this problem, this paper proposed an improved TEB algorithm to make the AGV walk along the wall when turning, which shortens the planning time and saves energy. Experiments were implemented in the Rviz visualization tool platform of the robot operating system (ROS). Simulated experiment results reflect that an amount of 5% reduction in the planning time has been achieved and the velocity curve implies that the operation was relatively smooth. Practical experiment results demonstrate the effectiveness and feasibility of the proposed method that the robots can avoid obstacles smoothly in the unknown static and dynamic obstacle environment. [ABSTRACT FROM AUTHOR]

Abstract: A visualization study is conducted to investigate condensation flow in wide rectangular silicon microchannels with the hydraulic diameter of 90.6 μm and width/depth ratio of 9.668. Droplet-annular compound flow, injection flow, and vapor slug-bubbly flow are observed along the channel, which differ from that in other cross-sectional shape microchannels. In the droplet-annular compound flow region, the vertical walls (short side) of the channel are completely covered by the condensate, while droplet condensation still exists on the horizontal wall (long side) of the channel. The location of the injection flow will be postponed with the increasing inlet vapor Reynolds number. The injection frequency will increase with the increasing inlet vapor Reynolds number and condensate Weber number. More specifically, the frequency in the wide rectangular microchannels is lower than that in triangular microchannels having the same hydraulic diameter. It is confirmed that the cross-sectional shape of the microchannel plays a significant role on the instability of condensation flow. In addition, the correlation of Nusselt number is also presented. [Copyright &y& Elsevier]

Abstract: A steady one-dimensional model for annular condensation flow in triangular microchannels is developed. The curvature radius distribution of the condensate stream along the channel has been determined numerically. The results indicate that the curvature radius of the liquid phase would increase rapidly at the beginning, and then as the condensation process progresses along the length of the microchannels, the radius increase would proceed more slowly. At the end of the condensation flow, the radius increases rapidly again. A smaller contact angle and heat flux or a larger hydraulic diameter and steam pressure will all result in a longer condensation length. [Copyright &y& Elsevier]

Drilling fluid continuous wave (DFCW) technology is an advanced downhole information telemetry technology and has broad application prospects, and its generation, transmission and reception technology has been studied extensively. However, the research on the waveform characteristics of downhole DFCW is still insufficient. In this paper, the characteristic model for describing sinusoidal DFCW in deep wellbore is established by combining the Navier-Stokes equations, orifice throttling theory and Fourier transform method, and the effects of the frequency, wave speed, reflective distance and well depth on the waveform characteristics of DFCW are analyzed based on the proposed model. The research results show that: (1) well depth will influence the amplitude of the DFCW in low frequencies because of the slight compressibility of drilling fluid, (3) smaller reflection distance and larger wave velocity will lead to longer periods of the amplitude-frequencies curves of the DFCW because of the superposition of the pressure wave, (4) the peak value of DFCW is proportional to the wave velocity, but the reflection distance has little effect on the peak or trough of the DFCW amplitude, (5) the DFCW amplitude varies periodically with frequency. The research results can provide critical technical support for the development of downhole DFCW generator and the study of its working characteristics. • The influences of reflected pressure wave at the bit on the characteristics of DFCW are analyzed. • The characteristic model for describing sinusoidal DFCW in deep wellbore is established. • The effects of frequency, propagation speed, the reflection distance and well depth on characteristics of DFCW are analyzed. • The amplitude-frequency curve is used to analyze the characteristics of the DFCW. • The results can provide the guide for the rotary valve design. [ABSTRACT FROM AUTHOR]

The nature gas and pure oxygen (NG/O2) combustion gas and steam mixture cycle (GSMC) is a novel power generation cycle using NG/O2 combustion product and circulation H2O as the turbine working medium, which can implement efficient power generation, CO2 capture and energy shifting. In GSMC, cold energy of liquefied natural gas (LNG) and liquefied oxygen (LO2) is used for CO2 capture. The CO2 capture schemes are analyzed to improve the CO2 capture as well as the system efficiency. The main means to increase the CO2 capture and extend CO2 full capture range include the reduction of CO2 liquefaction enthalpy drop and the conservation of cooling energy consumption in CO2/moisture separation. Lower efficiency is always a penalty of the full CO2 capture especially with higher condenser outlet temperature. The optimal scheme is different under different conditions such as parameters of turbine inlet, cooling water, and CO2 liquefaction. At turbine inlet of 30MPa/1000 °C and condenser outlet of 18kPa/38 °C, the efficiency drop is 1.18% for the full CO2 capture of the improved scheme, while the CO2 capture ratio of the original GSMC scheme is less than 60%. The distinctive CO2 capture of GSMC is summarized as system indispensable, scheme optional and method promotable. • Schemes are designed and discussed for full CO2 capture of the novel GSMC system. • Separation of CO2/H2O moisture is further considered and re-planed in new schemes. • Efficiency penalty with full CO2 capture increases at high ambient temperature. • Efficiency drop is 1.18% at proper design to raise CO2 capture from 60% to 100%. • CO2 capture reformation in power plant with GSMC system is of great significance. [ABSTRACT FROM AUTHOR]

Purpose: Conventional electric heaters mostly use U-shaped electric heating tubes and the hollow tube electric heaters are new type ones that rely on the heat transfer tubes as heating elements. However, in the original design, the fluid flows through the annular gaps between the shell wall and the supporting plates, the chambers between supporting plates are generally stagnant zones. The purpose of study is to overcome these deficiencies. Design/methodology/approach: A modified approach is proposed in which the heating tubes are surrounded by holes on the supporting plates, thus the stagnant flow zone can be eliminated and the heating surfaces of both inside and outside the tube can be fully used. Numerical simulations were carried out on four schemes of hollow tube electric heaters, i.e. plate blocked, countercurrent, parallel and split. The results show that the two schemes of parallel and split can reduce the temperature difference between the two sides of the fixed tube plate, and thus reduce thermal stress and prolong the service life. Findings: The split scheme of electric heater has the highest comprehensive index, moderate heat transfer coefficient and minimum pressure drop on the shell side. Its average heat transfer coefficient and comprehensive index are, respectively, 15.7% and 52.9% higher and its average pressure drop and tube wall temperature are, respectively, 57.6% and 19 K lower than those of the original plate blocked scheme, thus it can be recommended as the best scheme of the hollow tube electric heaters. Originality/value: Based on the original design of hollow tube electric heater with plate blocked scheme, three plate perforated schemes were proposed and investigated. The thermal and flow features of the four schemes were compared in terms of heat transfer coefficient, pressure drop and comprehensive index ho·Δpo−1/3. The split scheme can reduce the temperature difference between two sides of the fixed tube plate with reduced thermal stress. It has moderate tube wall temperature and heat transfer coefficient, the smallest shell side pressure drop and the highest comprehensive index ho·Δpo−1/3, and it can be recommended as the optimal scheme. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent test pen filled with a mixing ink of blue carbon dots (CDs) and red CdTe quantum dots (CdTe QDs) is introduced for portable assay of silver ion (Ag(I)) on paper. The mixing ink was tuned with ratiometric fluorescent intensity of 1:5, and then filled into a vacant commercial fluorescent pen core. Writing/painting a random word/figure on a blank paper can make the most portable nanoprobe determining Ag(I) by visualization. Ag(I) can adsorb onto the surface of CdTe QDs, which leads to the formation of surficial Ag2Te layer by an ion-exchanging reaction. This enables the red fluorescence of CdTe QDs (with excitation/emission maxima at 360/628 nm) to be quenched. Due to the unchanged blue fluorescence of CDs (with excitation/emission maxima at 360/440 nm) as internal standard, the solution color evolves gradually from red to blue with the increase of Ag(I) concentration with a detection limit of 3.48 nM. This is at least 2 orders of magnitude lower than the limit defined by World Health Organization (WHO) in drinkable water. The fluorescent test pen has also been used for the determination of Ag(I) in wastewater. [ABSTRACT FROM AUTHOR]

A modified Allam cycle (Allam-Z cycle) with a simpler system was proposed and investigated using NG (natural gas)/O 2 combustion products mixing with the circulation CO 2 as the working medium for power generation with high efficiency, zero CO 2 emission and peak load shifting. The modifications are that all the working media are pumped to high pressure by pumps instead of compressors, the cold energy of both liquid oxygen and LNG is used for degrading the cooling water for CO 2 liquefaction and a set of regenerative heat exchangers are arranged for turbine exhaust heat recovery. The influences of turbine parameters on the performances of the cycle were investigated. The comparison was performed under the conditions of condensation temperature of 30 °C, turbine inlet pressure of 30 MPa, inlet temperature of either 700 °C or 900 °C and the turbine outlet pressures of Allam-Z cycle and Allam cycle are 7.21 MPa and 4 MPa respectively. The results show that the output power efficiency and the equivalent net efficiency of the Allam-Z cycle with full CO 2 capture are 43.64% and 40.83% respectively or 50.87% and 48.05% respectively, which are 2.15% or 2.96% higher than those of the Allam cycle under the same condition. • A modified Allam cycle was studied with combustion product and CO 2 as working medium. • Cycle system is simplified with higher turbine back pressure to eliminate compressor. • The cycle integrates power generation with CO 2 capture and energy shifting. • Equivalent net efficiency is adopted considering 1/4 ASU consumed off-peak power. • Equivalent net efficiency is 48.05% with turbine inlet parameters of 30 MPa/900 °C. [ABSTRACT FROM AUTHOR]

Five new compounds including two stilbenes, designated thujasutchins A (1) and B (2), two phenolic compounds namely thujasutchins C (3) and D (4), as well as one sesquiterpene thujasutchin E (5), were isolated from the 95% ethanolic extract from the trunks and roots of Thuja sutchuenensis. Their structures were determined by means of extensively spectroscopic analysis including UV, IR, HRESIMS, 1H and 13C NMR (COSY, HSQC, HMBC). Moreover, compounds 1 , 3 – 5 were evaluated for in vitro cytotoxic activities against SF-268, MCF-7, HepG-2, and A549 tumor cell lines. Unlabelled Image [ABSTRACT FROM AUTHOR]

A modified Kalina cycle with parallel cogeneration of power and refrigeration abbreviated as PPR-KC was proposed and investigated. The cycle cogenerates refrigeration by further reclaiming heat resource from the boiler. A parallel branch of work solution is split at the outlet of the mid-p-absorber, and it undergoes pumping, generation, rectification and condensation before evaporation for refrigeration. Then the vapor from the evaporator goes to a mixer at the low-p-absorber inlet via a subcooler, while the dilute solution from the generator heats the basic solution in the second recuperator before going to the mixer via a throttle valve. The split fraction which determines the relative percentage of work solution flow rate for power generation or refrigeration can be altered arbitrary at user’s demand. The parameter optimization was conducted and the optimum work concentration is 0.5 and the optimum basic concentration shall be adjusted with different split fraction. Under temperatures of heat resource/cooling water are 400 °C/30 °C and minimum pinch temperature differences in heat exchangers with/without flue gas are 20/5 K respectively, the comprehensive power recovery efficiency of the PPR-KC reaches 27.2%, which is 9.85% and 20.24% respectively higher than those of the cogeneration cycle proposed by Liu et al. and the Kalina cycle. [ABSTRACT FROM AUTHOR]

A unilateral ladder type helical baffle heat exchanger (ULHBHX) which is a novel countercurrent U-tube heat exchanger was proposed and investigated for better characteristics of high heat transfer coefficient, low resistance, anti-vibration and anti-fouling with a spiral flow pattern than those of the conventional segment one. The numerical model of ULHBHX was established and simulated by CFD software with 38 heat transfer tubes and 2 rod and spacing tube assemblies in the lower half cylindrical space under the parameters of subcooling of a high pressure feedwater heater in power plants. Different views such as on baffle-parallel slices and polygonal slices were presented to show the flow patterns of the main helical flow, secondary vortex flow and the leakage flow. The influences of geometrical parameters of baffle pitch and projection length of the inclined section on heat transfer and pressure drop were discussed quantitatively. The results show that the shell-side heat transfer coefficient h o of the ULHBHXs is 13.2%–18.2%, with an average of 16.0%, higher than those of the corresponding segment schemes, and the comprehensive index h o Δ p o −1/3 is 15.7%–46.4%, with an average of 28.3%, higher than those of the corresponding segment schemes with identical baffle pitches in the discussed range. [ABSTRACT FROM AUTHOR]

In the contemporary era, energy demands are ever-growing and a significant number of people are concerned about environmental pollution caused by the burning of fossil fuels. Therefore, it is a striking problem for the researchers to pursue renewable energy and sustainable energy to deal with the environmental and energy crisis. In this work, a novel hybrid hollow porous ZnO/C nanocages with high specific surface areas of 256 m 2 g −1 and high carbon content in weight of about 50% used as anode materials for lithium ion batteries (LIBs) were synthesized by a one-step pyrolysis of hollow metal organic framework material MOF-5 as both precursor and self-sacrificing template under N 2 atmosphere. The hollow porous ZnO/C nanocages released an initial discharge capacity of 1928 mA h g −1 at the current density of 100 mA g −1 and remained a high reversible capacity of 750 mA h g −1 after 100 cycles. According to the results of electrochemical measurements, the hollow porous ZnO/C nanocages also showed a good rate capability of 351 mA h g −1 at a relative large current density of 2 A g −1 . The excellent electrochemical performance was mainly due to the special nanostructures of the fabricated materials. Hence, the as-resulted hollow porous ZnO/C nanocages are promising anode materials for LIBs. [ABSTRACT FROM AUTHOR]

A gas and steam mixture cycle (GSMC) is presented with a mixture of LNG/O 2 (liquid natural gas/oxygen) combustion product and feedwater as working medium, integrating features of high efficiency power generation, peak shaving, energy storage and CO 2 capture. The liquefied oxygen is produced during off-peak hours. During the operation hours, the cryogenic liquids of both LNG and oxygen are pumped to a high pressure and preheated before entering the combustors through the burners. The combustion product heats and mixes with the atomized feedwater to form supercritical H 2 O/CO 2 mixture vapor for power generation in a turbine unit. The CO 2 vapor is separated from condensate water in the condenser and liquefied by the cryogenic liquids of both LNG and oxygen after being compressed to a higher pressure. The circulation feedwater is injected to the annular channel between flame tube and shell cylinder of modular combustor via feedwater heating system. The results show that under the conditions of turbine inlet parameters of 40 MPa/800 °C and condensation temperature of 30 °C, the output power efficiency based on the thermal value of LNG fuel is 49.2% and the equivalent net efficiency is 46.4%, which accounts for 1/4 off-peak electricity consumption for liquid O 2 production. [ABSTRACT FROM AUTHOR]

Axial separation is a novel baffle connection configuration of circumferential overlap helical baffle heat exchangers which makes baffle incline angle seriation possible. The adjacent baffle plates are separated by sleeve tubes to form a greater pitched helix for enhancing heat transfer under required pressure drop with the least number of molds for reducing baffle manufacture cost. Numerical simulations of flow and heat transfer performances were conducted and the calculation results were verified by the experimental ones. Performance investigation was conducted on eight normal trisection helical baffle schemes with baffle incline angles from 15° to 23° and five axial separation schemes of equivalent 17–22° angles using 15° baffles. In the calculation scope the average deviations of heat transfer coefficients and pressure drops of the normal helical schemes are respectively about −1.97% and −8.11% per 1° deviation of incline angle. The axial separation schemes using 15° baffles with equivalent 21° and 22° incline angles have deviation values of heat transfer coefficient 1.21% and 1.33% lower and pressure drop 4.96% and 5.55% higher respectively than those of the normal 21° and 22° incline angle schemes. By adopting axial separation approach the seriation step of baffle incline angles can be extended to 8°. [ABSTRACT FROM AUTHOR]

In this study, monotonic and reversed-cyclic loading tests were conducted on six diagonally reinforced cold-formed steel (CFS) shear walls sheathed with a gypsum board (GYP) and a magnesium crystal board (MCB), respectively, to evaluate the effects of sheathing panels and different types of diagonal bracings on the shear capacity, lateral stiffness, ductility, and energy dissipation capacity of CFS shear walls. The results revealed that the stiffness of the skeleton, the sheathing material, the performance of the screw connections, and the construction of the splice of the wall panels have a distinct effect on the shear performance of the wall. The cooperative work effect of the rigid and strap bracings was excellent, and the ultimate strength and lateral stiffness of the wall were effectively improved by using an extra steel strap bracing. The shear performance of the wall sheathed with the MCB was higher than that of the wall sheathed with the GYP. When a flat steel strap was used to connect the panel splices, the torsion of the flat steel strap reduced the overall performance of the wall panels. This should be considered in practical engineering applications. • Six full-scale CFS shear walls were tested under monotonic and cyclic load. • The cooperative work effect of rigid and strap bracings was excellent. • The mechanical properties of the wall sheathed with MCB were better. • The diagonal braceing should be strengthened in the joint area. [ABSTRACT FROM AUTHOR]

Novel rotating-cylinder sliding vane rotary compressors (RC-SVRCs) are promising machines in energy conversion systems due to extremely low friction. However, three-dimensional visual investigations on geometrical optimizations of RC-SVRCs are highly limited. Besides, most flow mechanisms and leakage flow affected by geometric structures have not been fully revealed yet. Therefore, the sliding vane number, gap heights at vane tips and length-to-diameter ratio are numerically studied in this work. The results show that more sliding vanes (4∼12) lead to more uniform flow and temperature fields, lower mass flow rates and outlet temperature, less leakage between rotor and rotating cylinder. The mass flow rate, leakage m L1 between rotor and cylinder and leakage m L2 at vane tip of 8-sliding-vane scheme are 2.944 × 10−2, 9.949 × 10−4 and 3.692 × 10−5 kg·s−1, respectively. Gap height at vane tips has vital effects on flow fields. As the gap increases (0.01∼0.05 mm), mass flow rate and isentropic efficiency are decreased by 12.68% and 18.26%, the outlet temperature, leakage m L1 and m L2 are increased by 91.5 K, 69.60% and 22 times, respectively. High-temperature areas and leakage flow increase with the increase of cylinder length, which is recommended no longer than 0.6 diameters. This work allows making recommendations for designing RC-SVRCs. [ABSTRACT FROM AUTHOR]

Rational design of cost-effective and efficient bifunctional oxygen electrocatalysts for sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is urgently desired for rechargeable metal–air batteries and regenerative fuel cells. Here, the Fe3C nanoparticles encapsulated in N and F codoped and simultaneously etched graphene/CNTs architecture catalyst (Fe3C@N-F-GCNTs) was synthesized by a simple yet cost-effective strategy. The as-prepared Fe3C@N-F-GCNTs exhibited excellent ORR and OER performances, with the ORR half-wave potential positive than that of Pt/C by 14 mV, and the OER overpotential lowered to 432 mV at the current density of 10 mA·cm−2. In addition, the ΔE value (oxygen electrode activity parameter) increased to 0.827 V, which is comparable to the performance of the best nonprecious metal catalysts reported to date. When it was applied in a Zn–air battery as a cathode, it achieved a peak power density of 130 mW·cm−2, exhibiting the potential for large-scale applications. [ABSTRACT FROM AUTHOR]

High-accuracy temperature measurement plays a vital role in biomedical, oceanographic, and photovoltaic industries. Here, a highly sensitive temperature sensor is proposed and demonstrated based on cascaded polymer-infiltrated Mach–Zehnder interferometers (MZIs), operating near the dispersion turning point. The MZI was constructed by splicing a half-pitch graded index fiber (GIF) and two sections of single-mode fiber and creating an inner air cavity based on femtosecond laser micromachining. The UV-curable polymer-infiltrated air cavity functioned as one of the interference arms of MZI, and the residual GIF core functioned as the other. Two MZIs with different cavity lengths and infiltrated with the UV-curable polymers, having the refractive indexes on the different sides of the turning point, were created. Moreover, the effects of the length and the bending way of transmission SMF between the first and the second MZI were studied. As a result, the cascaded MZI temperature sensor exhibits a greatly enhanced temperature sensitivity of −24.86 nm/°C based on wavelength differential detection. The aforementioned result makes it promising for high-accuracy temperature measurements in biomedical, oceanographic, and photovoltaic applications. [ABSTRACT FROM AUTHOR]

A new alternate absorption scheme of both horizontal tubular cooling absorption and mesh layer adiabatic absorption was investigated with longitudinal corrugated M–W mesh guiders inserted to the gaps of the staggered horizontal tube bundle, leading solution film flows from the lower edge of each tube to the upper edges of its lower position neighbouring tubes at both sides. The mirror symmetric M–W mesh guiders facilitate uniform distribution and dual-side exposing solution film to the vapour for adiabatic mass transfer. The VOF CFD models were established for vapour absorption with aqueous LiBr solution falling film on the alternate absorber and bare tube one. The distributions of liquid film, temperature and concentration of the solution and local heat transfer coefficient on the tube surfaces were demonstrated for both absorbers. The simulation results demonstrated that the average heat and mass transfer coefficients with the alternating absorber are respectively 33.4% and 55.4% higher than those of the bare tube one. [ABSTRACT FROM AUTHOR]

The feed water heaters in power plants are actually the condensers using turbine extracting steam to heat feed water. The vertical feed water heater occupies less area than the horizontal one and convenient to lift tube bundles out in maintenance. However, the lower heat transfer coefficient due to thick condensate film limits its application. A novel trisection helical baffled vertical condenser (feed water heater) is proposed with liquid dams and gaps for facilitating condensate drainage. The flow and condensation heat transfer characters of two vertical condensers with variable angled trisection helical baffles of both single-thread and dual-threads and a variable spanned segmental baffled one were numerically studied with Mixture model of Fluent software. The distributions of velocity, pressure, volume fraction of condensate, and local heat transfer coefficient in these heat exchangers were demonstrated. The simulation results show that the inclined baffles with liquid dam and drainage gaps could drain condensate effectively from tube bundle surfaces and prevent liquid film from entraining into vapor, and that the variable angled trisection helical baffled vertical condenser with dual-threads could greatly improve the condensation heat transfer coefficient up to 35.7% higher than that of the variable spanned segmental baffled one. [ABSTRACT FROM AUTHOR]

The integrated system of AWKRC (ammonia–water Kalina–Rankine cycle) is a novel cycle operated on KC (Kalina cycle) for power generation in non-heating seasons and on AWRC (ammonia–water Rankine cycle) for cogeneration of power and heating water in winter. The influences of inlet temperatures of both heat resource and cooling water on system efficiencies were analyzed based on the first law and the second law of thermodynamics. The calculation is based on following conditions that the heat resource temperature keeps 300 °C, the cooling water temperature for the KC or AWRC is respectively 25 °C or 15 °C; and the temperatures of heating water and backwater are respectively 90 °C and 40 °C. The results show that the evaluation indexes of the power recovery efficiency and the exergy efficiency of KC were respectively 18.2% and 41.9%, while the composite power recovery efficiency and the composite exergy efficiency of AWRC are respectively 21.1% and 43.0% accounting both power and equivalent power of cogenerated heating capacity, including 54.5% heating recovery ratio or 12.4% heating water exergy efficiency. The inventory flow diagrams of both energy and exergy gains and losses of the components operating on KC or AWRC are also demonstrated. [ABSTRACT FROM AUTHOR]

• The power plant feedwater heaters and the countercurrent U-tube heat exchangers all involve half-cylindrical shell space. • Half-cylindrical space heat exchangers with ladder helical, orifice and segmental baffles were experimentally investigated. • The ladder helical baffle scheme has superior heat transfer coefficient and comprehensive index than those of the other ones. • The orifice baffle scheme has higher comprehensive index but lower heat transfer coefficient than those of segmental ones. • The average values of h o Δ p o −1/3 of ladder helical and orifice baffle schemes are about 15% higher than that of segmental one. The superheated steam cooling section and the condensate cooling section of the power plant feedwater heaters and the countercurrent U-tube heat exchangers all involve heat transfer in half-cylindrical shell space. The overall and shell-side heat transfer coefficients (h.t.cs.), pressure drop, and the comprehensive performances of some half-cylindrical space heat exchangers with different baffle structures were experimentally investigated. The investigated structures include three ladder helical baffle types [single inclined ladder helical (SH), dual inclined ladder helical (DH) and folded ladder helical (FH)], three orifice baffle types [fillet triangle orifice (F), trefoil-orifice (T) and quatrefoil-orifice (Q)], and segmental baffles (S), and all schemes are of two baffle pitches. Under the same baffle pitch and working condition, the experimental results show that the shell-side h.t.cs. of the ladder helical baffle schemes are higher than those of the orifice baffle schemes and segmental baffle ones; and the shell-side pressure drops of the orifice baffle schemes are much lower than those of the ladder helical baffle schemes and the segmental ones. The values of average comprehensive index h o Δ p o −1/3 of the ladder helical schemes FH-40, DH-40 and the orifice baffle schemes F-40 and T-40 are respectively 14.26%, 17.58%, 15.62% and 12.82% higher than that of the segmental scheme S-40. [ABSTRACT FROM AUTHOR]

• Kalina cycle based power/refrigeration cogeneration cycle (PPRAT-KC) was studied. • Adjustable range of refrigeration temperature is about from -22℃ to 7.5℃. • Adjustment of refrigeration temperature has no effect on amounts of energy outputs. • Amount of net power or refrigeration energy output can be flexibly adjusted. • The PPRAT-KC can maintain high performance when altering refrigeration temperature. Two schemes of power and refrigeration cogeneration Kalina cycle with adjustable refrigeration temperature (PPRAT-KC) based on the efficient cogeneration cycle PPR-KC are proposed and studied. In the PPRAT-KC, the refrigerant vapor is absorbed in a pressure adjustment absorber with dilute solution either from the separator or the low-pressure pump, and by altering the flow rate of the dilute solution, the refrigeration temperature is able to be adjusted with nearly no effect on the amounts of energy outputs. The amount of net power or refrigeration capacity in the PPRAT-KC can be also adjusted by changing the flow rate of solutions fed to the power and refrigeration sub-cycles. Under temperatures of heat source and cooling water of 400℃ and 30℃, respectively, the change range of refrigeration temperature for the two schemes of the PPRAT-KC are about from -22℃ to 7.5℃, and the performances of the two schemes are similar. With the same work concentration of 0.5 and refrigeration temperature of -15℃, the effective exergy effeciency of PPRAT-KC is 0.5653, which is 4.145% and 10.97% higher than those of the PPR-KC and the triple pressure Kalina cycle, respectively. [ABSTRACT FROM AUTHOR]

• Air conditioning refrigeration achieves by guiding refrigerant vapor to mid-absorber. • Parallel PR cogeneration KC matches heat source well in cascade boiler and generator. • Leading generator dilute solution to low-pressure absorber has better performance. • Performances are improved by optimizing solution concentrations and boiler superheat. • Refrigeration/power ratio extends to 1.192 with boiler bubble point Δ t rises to 60 K. A parallel power/refrigeration cogeneration Kalina cycle (PPR-KC) system with adjustable refrigeration/power ratio that developed on the basis of the triple-pressure Kalina cycle system was analyzed. The PPR-KC system can produce refrigeration with temperature ranging in either air conditioning or ice making by switching the exhaust refrigerant vapor to the mid-pressure absorber or to the low-pressure one. The influences of the dilute solution from generator to the destination of either mid-pressure absorber (plan A) or low-pressure absorber (plan B) via recuperators on the performances of the PPR-KC system for air conditioning were investigated. The results show that the PPR-KC system matches well the heat source in cascade arranged boiler and generator thus showing excellent thermal performance by optimizing the solution concentrations, boiler superheat and other parameters. Under the given temperatures of heat source 400°C and cooling water 30°C respectively, the variation trends of the cycle parameters and performances of both plan A and plan B are presented. The power recovery efficiency of plan B is about 1.6% higher than that of plan A. When boiler bubble point temperature difference increases from 20 K to 60 K the refrigeration/power ratio of plan B climbs from 0.475 to 1.192. [ABSTRACT FROM AUTHOR]

• A novel helical baffle with small inclined angle and folded structure is proposed. • The new helical baffles can be created by cheap 2D laser cutting and folding. • The leakage between two folded helical baffles can be greatly decreased. • The novel electric heaters have excellent flow and heat transfer performances. • Folded helical baffles are more excellent at large equivalent angles in this work. The difficult manufacturing of helical baffles hinders the widespread application of the enhancement technology and the shortcut leakage between adjacent baffles impairs the enhancement effects. To solve these two issues, the promising anti-leakage and easy-to-manufacture helical baffles with small inclined angle and folded structure are proposed, which can be produced by 2D laser cutting and simple mechanical folding. The influence of different helical baffle configurations, including three normal helical schemes, three axial separation helical schemes, three novel folded axial separation helical baffle schemes and a segmental scheme on the performance of electric heaters are numerically investigated. The equivalent angles of helical schemes adopted in this work are 15°, 20° and 25°, and the inclined angle of helical baffles under axial separation connection style is 10°. Compared with the corresponding axial separation scheme without folding, the leakage can be significantly decreased, the heat transfer coefficients h and the comprehensive indices h ⋅Δ p −1/3 of FH15(10)°, FH20(10)° and FH25(10)° are increased by 6.5%/2.3%, 12.2%/7.3% and 20.4%/13.0%, and the averaged tube wall temperatures T w are decreased by 12.5 K, 25.4 K and 54.7 K, respectively. This research can provide feasibility for the extended application of helical baffles in electric heaters or heat exchangers. [ABSTRACT FROM AUTHOR]

• A novel helical baffle with small inclined angle and folded structure is proposed. • The new helical baffles can be created by cheap 2D laser cutting and folding. • The leakage between two folded helical baffles can be greatly decreased. • The novel electric heaters have excellent flow and heat transfer performances. • Folded helical baffles are more excellent at large equivalent angles in this work. The difficult manufacturing of helical baffles hinders the widespread application of the enhancement technology and the shortcut leakage between adjacent baffles impairs the enhancement effects. To solve these two issues, the promising anti-leakage and easy-to-manufacture helical baffles with small inclined angle and folded structure are proposed, which can be produced by 2D laser cutting and simple mechanical folding. The influence of different helical baffle configurations, including three normal helical schemes, three axial separation helical schemes, three novel folded axial separation helical baffle schemes and a segmental scheme on the performance of electric heaters are numerically investigated. The equivalent angles of helical schemes adopted in this work are 15°, 20° and 25°, and the inclined angle of helical baffles under axial separation connection style is 10°. Compared with the corresponding axial separation scheme without folding, the leakage can be significantly decreased, the heat transfer coefficients h and the comprehensive indices h ⋅Δ p −1/3 of FH15(10)°, FH20(10)° and FH25(10)° are increased by 6.5%/2.3%, 12.2%/7.3% and 20.4%/13.0%, and the averaged tube wall temperatures T w are decreased by 12.5 K, 25.4 K and 54.7 K, respectively. This research can provide feasibility for the extended application of helical baffles in electric heaters or heat exchangers. [ABSTRACT FROM AUTHOR]