Search

• A compact fluidized bed carbonator is firstly studied under hot conditions. • The effect of scale limitation on capture efficiency is found. • A normalized capture efficiency model is developed for the carbonator. • Operating conditions and sorbent characteristics has effects on active space time. Even though calcium looping application for pre-combustion carbon dioxide capture itself has been demonstrated at TRL 6, modification on carbonator/gasifier structure is still desired for further enhanced sorption and tar reforming intensification. A lab-scale dual fluidized bed within a compact fluidized bed carbonator is the first time constructed and tested under electric-heating hot conditions, which is a critical step to develop to self-heat and pilot-scale system. The compact fluidized bed carbonator takes advantage under two coupled different fluidization regimes and reaction temperatures, and has more commonality and flexibility in future application. In this work, feasibility of long-term stable state operation on the lab-scale hot rig was proved and several tests were conducted to study its operation characteristics by calcium looping process. Normalized capture efficiency model for the compact fluidized bed carbonator is developed. Constructional constraints of reactor, different operating conditions and sorbent characteristics have strong effects on capture efficiency and active space time. This work provides a solid basis for future investigation of calcium-based sorption enhanced gasification or tar cracking intensification on this facility. [ABSTRACT FROM AUTHOR]

This paper discussed the procedure of an optimization design method involving a small lab-scale wind turbine rotor. To simulate the aerodynamic performance of a prototype wind turbine at utility-scale by scaled model experiments (especially, the visualization measurements of wake flow in small wind tunnels), an appropriate similar design of the small lab-scale rotor is needed. However, the similar design of blade performance from a prototype wind turbine for small scaled model is rare. In this paper, using a 2.5 MW utility-scale wind turbine as the prototype, we set up a new optimization process of similar design for a model wind turbine with a 320 mm rotor based on the Lifting-Line Theory (LLT) with wake-induced corrections. Results show a dramatic deviation in performance of the geometric scaled model compared to the objective values, which demonstrates the significance of the Reynolds number effects. With the optimized blade, the distribution of normal thrust force is very similar to the objective values. Geometric characteristics variations along the blade span are similar to the prototype. With the tip speed ratio runs at a roughly matched rated condition, the optimized rotor gives a better performance than other models used in previous wind tunnel studies. • A new small lab-scale wind turbine similar to the prototype has been designed. • The design process provides a hybrid model blade similar to the prototype. • Performance of geometric scaled model is significantly less than the objective value. • A better performance of the optimized rotor has been comparably reached. [ABSTRACT FROM AUTHOR]

Real wind turbines experience a wide range of turbulent shear flows that naturally occur within the atmospheric boundary layer, however, these are often difficult to simulate in experiments. An active grid was used to expand the testable parameter space compared to conventional methods. Specific focus was placed on decoupling the shear from the turbulence intensity. Particle image velocimetry was used to capture the mean velocity and velocity fluctuation fields in the near-field wake of a model wind turbine subjected to seven different combinations of shear and turbulence intensity. It was found that if the incoming mean profile was removed, the velocity deficit is approximately symmetric about the hub, even for highly sheared cases. The absolute wake velocity deficit profiles are asymmetric for the sheared cases, and the combination of the wake and shear flow results in a local increase in shear on the high-velocity side of the wake immediately downstream of the turbine. This in turn leads to higher turbulence production within that region, leading to larger velocity fluctuations. It is also demonstrated that the mean power of the model turbine is not particularly sensitive to the incoming shear, but the power fluctuations scale linearly with the incoming turbulence intensity. • A model wind turbine is tested in seven different tailored turbulent shear flows. • The relative wake velocity deficit is symmetric, even for high incoming shear. • The turbulence production is biased toward the high-velocity side in the near wake. • The power fluctuations scale with incoming turbulence intensity but not shear. [ABSTRACT FROM AUTHOR]

Optimization and design of full-scale membrane distillation (MD) systems usually require Sherwood and Nusselt correlations that are developed from lab-scale systems. However, entrance effects in lab-scale systems can significantly impact heat, mass and momentum transfer in the reactor, therefore affect the accuracy of the developed experimental Sherwood and Nusselt correlations. Here, Computational Fluid Dynamics (CFD) simulations using OpenFOAM are performed to understand the effects of right-angled bends and inlet design on flow dynamics, temperature and concentration polarization in MD systems. Simulation results show that the presence of right-angled bends and inlets with sudden expansions lead to the formation of Dean vortices. Dean vortices enhance perpendicular mixing in MD systems and reduce both temperature and concentration polarization. Temperature and concentration polarization coefficients in MD systems with right-angled bends and inlets with sudden expansions vary significantly for the same volumetric flow rate. Our studies show that lab-scale systems with the same volumetric flow rate but different designs lead to significantly different Nusselt and Sherwood correlations. This study demonstrates the importance of CFD-informed design of lab-scale systems to minimize entrance effects and suppress Dean vortices for consistent model development and calibration across multiple scales. [Display omitted] • The bends and inlets affect polarization coefficients at moderate and high Reynolds numbers. • Both bends and inlets with sudden expansions result in Dean vortices. • Dean vortices reduce polarization for the same volumetric flow rate. • Correlations must be developed on lab-scale systems with suppressed Dean vortices. [ABSTRACT FROM AUTHOR]

Cryogenic freezers are commonly applied in the food processing and healthcare industries, and offer a highly effective preservation method without significant product degradation. The modelling of freezers has been conducted mainly around food processing, to observe the cooling rate during the chilling process. Typically, cryogenic freezers operate with a mix of air and nitrogen as the working fluid, with the effects on the heat transfer coefficient being thoroughly noted, in a range of applications. The effect of the heat transfer coefficient has not been investigated in a liquid nitrogen application, with a cryogenic applicability. This paper will focus on the CFD visualisation of the circulation of air around a lab scale cryogenic batch freezer. The effect of the heat transfer coefficient will be investigated in a number of scenarios, such as shelf loading conditions, product configuration and thermal profiles. The cryogenic batch freezer will be simulated in a range of room temperatures starting from -70°C, using a thermal profile which was obtained experimentally. [ABSTRACT FROM AUTHOR]

• A lab-scale ultra-high-temperature tungsten solar receiver is designed. • Optical-thermal-mechanical performance of the receiver is evaluated. • High receiver efficiency of 81.88–89.08% is achieved under different conditions. • The receiver can work safely at ultra-high outlet temperature of above 1573 K. The key to raising the cycle efficiency of the solar power tower plant is to improve the operating temperature of the solar receiver. However, only a few receivers can operate at a temperature above 1573 K, and it is still very challenging to harvest solar energy safely and efficiently under such ultra-high temperatures. In this paper, firstly, a lab-scale tungsten receiver with the designed thermal power of 7 kW th was designed for ultra-high-temperature solar energy harvesting. Then, an optical-thermal–mechanical coupling model was constructed and validated with experimental data. Based on this model, the receiver performance under different cylinder lengths was evaluated. It is found that the solar receiver with a 150 mm length cylinder was able to operate safely and efficiently under the most extreme condition, which was suggested as the optimized design. Then, the effects of key operating parameters on the performance of the optimized receiver were analyzed, finding that the receiver efficiency increases with increasing inlet mass flow rate, decreasing inlet temperature, or increasing incident power. Moreover, performance evaluation indicates that high receiver efficiency of 81.88%-89.08% can be achieved by the optimized receiver while the inlet mass flow rate is within 0.07–0.12 kg·s−1, the average fluid temperature is within 833.9–1384.7 K, and the incident power is within 5.5–8.0 kW. Results from the present study can provide a reliable and useful reference for developing ultra-high-temperature solar receivers. [ABSTRACT FROM AUTHOR]

In developing a higher activity for NOx abatement from stationary emission sources, photo-assisted selective catalytic reduction (photo-SCR) was systematically investigated over TiO 2 supported on a spherical α-Al 2 O 3 /γ-Al 2 O 3 . The formation of NO 2 was virtually suppressed in the reaction temperature range of 110–200 °C. The NOx removal efficiencies of TiO 2 /γ-Al 2 O 3 photocatalyst at 120 °C for real flue gas (in pilot-scale photoreactor) and simulated flue gas (in lab-scale photoreactor) were 68–75% and 43.5%, respectively, in the presence of reducing reagent (C 4 H 10 ). SEM and XPS techniques revealed that sulfur temporarily occupied the active sites of the photocatalyst, causing deactivation. Spent TiO 2 /γ-Al 2 O 3 photocatalyst was regenerated via desulfurization by either air or hydrogen at 400–500 °C. The effects of regeneration temperature and regeneration time on the photocatalytic activity are methodically investigated, demonstrating that using hydrogen at 500 °C in 1 h could completely regenerate the spent photocatalyst. [ABSTRACT FROM AUTHOR]

In the present study, we developed an efficient composting process for the solid fraction of dairy manure (SFDM) using lab-scale systems. We first evaluated the factors affecting the SFDM composting process using different thermophilic phase durations (TPD, 6 or 3 days) and aeration rates (AR, 0.4 or 0.2 l min −1 kg −1 -total solid (TS)). Results indicated that a similar volatile total solid (VTS) degradation efficiency (approximately 60%) was achieved with a TPD of 6 or 3 days and an AR of 0.4 l min −1 kg −1 -TS (hereafter called higher AR), and a TPD of 3 days resulted in less N loss caused by ammonia stripping. N loss was least when AR was decreased to 0.2 l min −1 kg −1 -TS (hereafter called lower AR) during the SFDM composting process. However, moisture content (MC) in the composting pile increased at the lower AR because of water production by VTS degradation and less water volatilization. Reduced oxygen availability caused by excess water led to lower VTS degradation efficiency and inhibition of nitrification. Adding sawdust to adjust the C/N ratio and decrease the MC improved nitrification during the composing processes; however, the addition of increasing amounts of sawdust decreased NO 3 − concentration in matured compost. When an improved composting reactor with a condensate removal and collection system was used for the SFDM composting process, the MC of the composting pile was significantly reduced, and nitrification was detected 10–14 days earlier. This was attributed to the activity of ammonia-oxidizing bacteria (AOB). Highly matured compost could be generated within 40–50 days. The VTS degradation efficiency reached 62.0% and the final N content, NO 3 − concentration, and germination index (GI) at the end of the composting process were 3.3%, 15.5 × 10 3 mg kg −1 -TS, and 112.1%, respectively. [ABSTRACT FROM AUTHOR]

A fixture has been designed and fabricated to facilitate accelerated electromigration (EM) testing with in situ imaging capability of wire-like specimens. This fixture design has enabled microstructural evolution studies in microscale (100 μm–500 μm in dimension) solder volumes. The fixture allows application of thermal and electrical stimulus to wire-like solders in situ during multi-modal characterization. The design is compatible with surface (2D) characterization techniques including optical microscopy (OM) and scanning electron microscopy (SEM) based analyses. SEM characterization using the fixture has also been coupled with electron back-scatter diffraction (EBSD). Grain orientation image maps (OIMs) were obtained for in situ crystallographic microstructural analysis of the test volumes. The fixture is also compatible with X-ray computed tomography (non-destructive and 3D), or XCT, analysis of microstructure volume. To apply 2D techniques, a facet has been polished into the solder volumes prior to mounting within the fixture, though this surfacing requirement is not required for XCT characterization. A demonstration of the fixture's successful EM testing function is provided. The compatibility of the fixture with these characterization tools is also demonstrated. Both functional thrusts of the new in situ fixture's design have been accomplished through the fixture's form which is provided in reproducible detail. [ABSTRACT FROM AUTHOR]

The objective of this research was to use a stepwise approach to develop a temperature-dependent prediction model for scale-up of forward osmosis. A Sobol sensitivity analysis confirmed that water permeability (A) of Forward Osmosis (FO) membrane has significant effect on water flux while salt permeability (B) has limited impact. Statistical analysis indicated that the stepwise model prediction provided improved agreement with experimental measurements of water and salt fluxes compared to prediction from a lumped parameter model over the range from 15 °C to 35 °C. The temperature predictions from the stepwise model were in close agreement with experimental temperatures; with deviations of less than 0.2 °C. When simulated with the increase in the length and width of the flow channel, the differences in predictions between the stepwise and lumped model increased. These results emphasize that parameter variations along the channel length should be accommodated by the stepwise model. In simulations using the stepwise model, the co-current flow mode was found to generate higher water flux than the counter-current flow mode. The results and analysis from this investigation demonstrate the advantages of the stepwise model for prediction of water flux for scale-up of FO operations. • Accurate estimation of water permeability is essential for FO water flux prediction. • Permeability of membrane increases with increase in temperature. • Proposed stepwise model provides closer agreement in water flux and temperature. • Stepwise model would be more desirable to use in large-scale. • Stepwise model can be used to determine flow direction to generate higher flux. [ABSTRACT FROM AUTHOR]

Pulp and paper industry generates large quantity of sludge, up to 1 m 3 /ton paper produced. Anaerobic digestion (AD) is a potential treatment to stabilize sludge and produce biogas for renewable energy. The aim of this study was to investigate the potential of AD of paper sludge (PS) generated from primary and secondary wastewater treatment and to compare the effect of cow manure to paper sludge. For the reactor with PS only, biogas production was observed starting on the 5 th day with 6.3% of methane with a steady increase. The cumulative methane yield attained to 14.7 ml/g volatile solid (VS) until day 28. The second reactor containing PS and cow manure produced methane 269 ml/g VS until day 28. This study shows a more optimal AD process of paper sludge mixed with cow manure due to a more optimum C/N ratio and also higher VS. [ABSTRACT FROM AUTHOR]

Highlights: [•] PVA membrane for the separation of methanol and dimethyl carbonate identified. [•] Steady-state experiments performed in lab- and pilot-scale vapor permeation plants. [•] Mass-transfer model for description of experimental data identified and parameterized. [•] Model-based scale-up using a rate-based model validated with experimental results. [•] Guideline for scale-up of vapor permeation from lab to industrial-scale developed. [Copyright &y& Elsevier]

Abstract: A new meshing method for fixed beds consisting of monodisperse spherical particles is presented. The particles are flattened near the particle–particle and particle–wall contact points, respectively, to avoid bad cell qualities. Compared to known methods from literature the modifications are so small that a subsequent correction of these modifications is not necessary. CFD simulations are performed for tube to particle diameter ratios of 3≤ D/d ≤10 in the laminar, transitional and turbulent flow regime and are compared with results from literature concerning porosity and pressure drop. The flow pattern within the bed is also investigated. The random fixed bed is generated with a DEM-code and the fluid domain is meshed with the commercial CFD code STAR-CCM+. The focus of this work is to verify, that physically correct results as well as meshes with a low number of cells and therewith short calculation time can be obtained with this new meshing method. [Copyright &y& Elsevier]

Microbial communities were analyzed in six full-scale anaerobic digesters and a lab-scale digester using the random cloning method. The purposes were to confirm the applicability, reproducibility, and error range of this method; to discuss the difference in the dominant microbes determined by this method in different operational conditions of temperature (mesophilic and thermophilic) and substrate (garbage, sewage sludge, and livestock waste); and to determine key microbes in each digester. Each sample was analyzed in triplicate. In one of the samples, 373 clones were analyzed to study the composition of microbial community in the digester. Time course analysis was conducted from the start-up period for approximately one year in one of the digesters. Similar microbial diversity was obtained corresponding to the type of substrate change (sewage sludge to garbage). Operational taxonomic units (OTUs) closely related to Coprothermobacter sp. and unidentified bacterium clones TUG14 and TUG22 disappeared during the first 40 d, while OTUs closely related to Bacillus sp. and Clostridium sp. increased later. Microbial diversity in digesters is strongly affected by the operational conditions, and similar microbial diversity can be obtained in triplicate analysis and under similar operational conditions. The present study verified the applicability of this method to discuss the overall difference in microbial communities. [Copyright &y& Elsevier]

Abstract: Two feeding strategies for start-up of continuously stirred tank reactors (CSTR) treating source-sorted organic fraction of household municipal solid waste (SS-OFMSW) at 55°C were evaluated. Two reactors were started up separately with a limited amount of initial inoculum (i.e. 10% of the final volume of 3.5l) and operated in a fed batch mode until the reactors were filled (30 days). A reference reactor was filled up with 3.5l of inoculum and fed at a constant rate (11.4g volatile solids (VS)/d). Loading at progressively increasing rate (from 1.7 to 15gVS/d), as calculated based on an activated biomass concept, showed superior process performance compared to a fixed feed rate (5.7gVS/d). Methane yield of 0.32m3/kg VS was produced during the start-up in reactor filled at progressively increasing rate and was comparable to the reference reactor. On the contrary, significant inhibition due to volatile fatty acid (VFA) build-up, mainly due to butyrate, was noticed in the reactor filled at constant rate. Thus, low initial and progressive increasing inoculum loading rate could be used as a strategy for a successful start-up of CSTR treating SS-OFMSW as it allowed a gradual acclimation of the biomass. Lab-scale results were further reaffirmed from the start-up of a full-scale plant (7000m3 total capacity) which was supplied with inoculum corresponding to approx. 16% of final volume and operated in a fed batch mode until the reactors were filled (58 days). Stable biogas production with low VFA (<3g/L; based on titration method) were noticed during the start-up period when fed at progressively increasing rate. Thus, a controlled and reliable start-up procedure was found essential, which could allow rapid process stabilization and time to focus on other technical aspects of plant operation. In addition, the influence of substrate to inoculum amount (1.5–30% TS) and temperature (5–65°C) on anaerobic degradation and methane production of SS-OFMSW was investigated in batch assays as a protocol for start-up procedure. [Copyright &y& Elsevier]

Improving conformance control in reservoirs with a heterogeneous permeability distribution is the objective of many enhanced oil recovery (EOR) methods. In recent years, the injection of preformed Particle Gels (PPGs) is suggested as an effective EOR method to control the in-depth conformance of waterfronts. In this study, a new mathematical transport model of PPG injection in mature waterflooded reservoirs is developed. The model is based on the experimental results of PPG swelling ratio and entrapment analyses in a carbonate rock sample. The entrapment is considered as a function of the PPG-to-pore size ratio, fluid velocity, temperature, salinity, PPG concentration, and swelling ratio. The formulations of the resistance factor (RF) and residual resistance factor (RRF) are obtained from the injection experiment results at various fluid velocity and PPG concentrations. The entrapment model is coupled with the transport equations of the MATLAB Reservoir Simulation Toolbox (MRST). The model is validated by predicting the pressure drop changes during the 1D PPG injection experiments at three different flow rates. The validated model is then used to predict PPG transport behavior in several 3D field-scale scenarios. The sensitivity analysis results show that a higher recovery increment can be achieved when the reservoir permeability contrast is increased. There is an appropriate PPG-to-pore size ratio (i.e., D P T of 1.75) that can guarantee deep conformance control and avoid PPG washing out during post-waterflooding. Furthermore, the PPG concentration of 1750 ppm resulted in a significant entrapment in the porous medium. [Display omitted] • Conformance control of PPG injection was modeled at the core- and reservoir-scale. • Various parameters were considered for the estimation of the PPG entrapment amount. • PPG swelling ratio was considered as a function of reservoir temperature and salinity. • The introduced PPG transport model validated against 1D core flooding experiments. • Field-scale sensitivity analyses were performed to obtain key injection properties. [ABSTRACT FROM AUTHOR]

Planar particle image velocimetry was conducted upstream and in the near-wake of a lab-scale free-rotating wind turbine model and compared to several actuator disks with the same dimensions. The Reynolds number of the incoming flow is order 104. Actuator disks with different designs and solidities were tested, and the process of actuator disk selection is explicitly shown. The drag, mean velocity and mean vorticity in the wake of the disks were compared to that of the rotating model. For the disk that was the best match, the Reynolds stresses and swirling strength are also presented. The instantaneous swirling strength illustrated that despite similar mean fields, the instantaneous phenomena were significantly different. Distinct tip vortices were present in the wake of the rotating model but were absent from the wake of the actuator disk. Proper orthogonal decomposition was used to further investigate the underlying phenomena in the two flows, again demonstrating the importance of tip vortices when studying the rotating model and the lack of such distinct vortices when using the actuator disk. Hence, despite well-matched mean characteristics, the instantaneous structures in the two flows remain distinct. Image 1 • Investigation of different popular actuator disk geometries with varied blockage. • Comparison to a free-rotating wind turbine model used in the literature. • Assessment of drag, mean velocity, Reynolds stress, vorticity, and swirl fields. • Distinctly different instantaneous phenomena in the wakes. • Different upstream effects of the rotating model and the actuator disks. [ABSTRACT FROM AUTHOR]

The rapid growth in the variety and quantity of contaminants of emerging concern (CEC) in wastewater indicates the necessity for developing efficient and environmentally friendly methods for their removal. This study investigates the removal efficiency of 46 CEC, including 12 bisphenols, from wastewater using a lab and pilot-scale hydrodynamic cavitation generator alone and in combination with UV illumination (pilot-scale). During lab-scale cavitation, the highest removal efficiencies of bisphenols (15–63%) for this specific design of cavitator were obtained at a rotational frequency (v cav) = 9500 rpm and time (t cav) = 10 min. Temperature and the physicochemical properties (e.g. K ow) of the studied compounds also had a significant effect on removal efficiency. At the pilot-scale, 11 CECs were quantifiable in the wastewater influent, and the generator operated at ν cav = 2290 and 2700 rpm. The highest removal efficiencies (15–90%) were obtained at a lower ν cav = 2290 rpm while neither an increase in ν cav , t cav or the presence of UV-C light increased the removal efficiency. A lower ν cav also reduced the hydrodynamic power of the cavitator from 477 W to 377 W, resulting in reduced energy consumption. Overall, the results show the potential of hydrodynamic cavitation for a large-scale application as a pre-treatment technology and pave the way for future improvements in the design of cavitation reactors. Unlabelled Image • Removal efficiencies for bisphenols observed in lab-scale HC set-ups were 15–63%. • Temperature and K ow effect HC removal efficiency. • A lower ν cav resulted in higher removal of CECs in the pilot-scale HC system. • Increasing t cav or combined HC and UV did not improve removal efficiencies. • HC shows potential for large-scale application as a pre-treatment technology. [ABSTRACT FROM AUTHOR]

• AWPA E1 grades for assessing termite damage on wood are heavily subjective. • Deep convolutional networks can be applied to help human graders judgment. • Stratified k -fold cross validation for small datasets. • Sequential AlexNet offers the best performance to predict grades of damaged wood samples. • Potential future applications in termite damage assessments using deep learning. We evaluated convolutional neural networks (CNNs) to visually classify severity of termite attack according to the rating scale from the AWPA E1 standard. The wood wafer dataset contained only 181 uniquely damaged samples. To help compensate for the lack of a large dataset, we performed stratified 5-fold cross validation in which the number of testing samples varied from 33 to 39. Data augmentation was performed on-the-fly on each training set by rotating and flipping samples to generate from 8520 to 8880 images. The CNNs tested included sequential AlexNet, InceptionV3, ResNet50, and InceptionV4-ResNetV2. Each CNN trained relatively well with no sign of overfitting. Sequential AlexNet achieved the best performance, predicting samples with an overall adjusted accuracy of 76.5%, followed by InceptionV3, ResNet50, and InceptionV4-ResNetV2 with 75.0%, 70.8%, and 67.2%, respectively. Sequential AlexNet reached a top-2 accuracy of 97.2%. Mispredictions were more prevalent in the E1 mid-grade ranges, i.e., 4–6 and 8–9. We believe that AlexNet out-performed the other CNNS because of two possible reasons: (1) the other deeper CNNs learned spurious features from the samples that led to more mispredictions; or (2) the other deeper CNNs simply require a training dataset larger than we had available. Future work will focus on developing machine-learning software to grade samples and segment the damage on early/latewood. In addition, we plan to solicit and collect more termite damage samples worldwide in order to enhance our tool and further validate our current findings based only on a limited dataset. [ABSTRACT FROM AUTHOR]