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The objective of this study is to assess the viability of implementing the methodology proposed in the SFERA-III project for the assessment of key performance indicators (KPIs) of thermal storage prototypes in a specific packed-bed device. SFERA-III project is an EU funded project aiming, among others, to upgrade the infrastructures and services related to Concentrating Solar Thermal technologies. In order to improve the quality of services in relation to the testing of thermal energy storage prototypes, a protocol and KPIs were defined and validated with different types of devices, though none of them was a packed-bed. This study elucidates the challenges encountered in the implementation of the protocol on a packed-bed prototype, alongside the proposed alternative solutions and their influence on the resulting KPIs. The analysis demonstrates that the SFERA-III Key Performance Indicators are an appropriate means of evaluating packed bed thermal energy storage prototypes. Consequently, the use of these KPIs as a standard is supported. • ● Analyse standardization activities related to thermal energy storage prototypes • ● Testing of sensible and latent thermal energy storage prototypes • ● Key performance indicators applied to a packed-bed prototype [ABSTRACT FROM AUTHOR]

Thermal energy storage is an essential subsystem for periodic energy generation sources, such as solar energy, whereby rapid energy storage and recovery are key aspects of every energy storage medium. Phase change materials are desirable due to their higher storage density and slight temperature variation in thermal energy storage systems. This study aims to evaluate the thermal performance of packed-bed thermal energy storage (PBTES) by conducting an experimental study and numerical simulations. For this purpose, cylindrical storage is built as part of the experimental setup for validation purposes, where capsules containing paraffin are randomly embedded in the tank, and then integrated with a constant-temperature water tank for further assessment. Meanwhile, the numerical study has been developed towards assessment using two-phase change material (PCM) in the shell and core of spherical capsules. The obtained results indicate an average reduction of 46 % in melting time when the capsule size decreases from 75 mm to 54 mm. Additionally, using two PCMs in the spherical capsule is considered to increase the temperature difference between the melting point of the PCM and the charging temperature to compensate for the low heat transfer rate. Five cases with different volume ratios for two PCMs are compared to the base case with one PCM. The results indicate that the new model can reduce melting time by 16.38 %–45.19 % compared to the base model with a single phase. [ABSTRACT FROM AUTHOR]

Decarbonising the industrial sector is a key part of climate change mitigation targets, and Solar Heat for Industrial Process (SHIP) is a promising technology to achieve this. However, one of the drawbacks of SHIP systems is that they rely on an intermittent energy source. Therefore, sensible energy storage has emerged as a potential solution. In addition, solid byproducts have been proposed as a low-cost but effective material for thermal energy storage (TES). This work presents a SHIP system model coupled with a copper slag-packed-bed TES (PBTES) model using air as heat transfer fluid. The TES has been implemented to preheat the makeup water of the tank where steam is generated. A system design was carried out using a parametric analysis to find a solar field size and a corresponding TES volume. The resulting system was simulated, and the operating variables were analysed in detail. The results show that it is possible to generate 20% more energy due to the storage system. Additionally, a techno-economic analysis indicates that the SHIP with PBTES system results in a payback period of 14 years and a savings of C O 2 emissions of 30 t C O 2. • Integration of a SHIP system with copper slag packed-bed TES • Dynamic simulation and analysis of the system's main variables • System performance assessment and control improvement • Techno-economic analysis of the entire system and carbon savings • SHIP system with TES presents a payback of 14 years and annual savings of 30 tCO2 [ABSTRACT FROM AUTHOR]

Concentrated Solar Power (CSP) is a critical technology for the renewable energy transition, offering high power output at elevated temperatures. However, further integration of CSP plants requires a reduction in investment costs. This study investigates the use of cost-effective, sustainable, waste-based TES materials—such as Electric Arc Furnace Black Slag (BS) and Tundish (TN) from the steel industry, as well as Demolition Waste (DW) from urban regeneration projects—as packing materials in TES systems to reduce the capital expenditure of CSP plants. A One-Dimensional Continuous Solid Phase (1D-2P) model was employed to evaluate and compare the performance of DW, TN, and BS. The results revealed that all materials demonstrated comparable properties, with TN exhibiting the highest energy storage capacity (44.7 kWh) and energy storage density (296 kWh/m³). With high utilization rates of 73–75 %, waste-based TES systems show strong potential for application in CSP plants. The TES systems were scaled for a 110 MW CSP plant, which currently operates with a 2-tank molten salt TES system providing 4648.4 MWh of storage capacity. TN required the smallest storage volume of 22,273 m³ for the 110 MW CSP plant. The reduction of molten salt usage by up to 31,000 tons in the waste-based packed-bed TES system could significantly enhance the economic feasibility of CSP plants. [Display omitted] • Packed beds can reduce amount of molten salt required by 77 % in TES for CSP. • Using waste-based packing provides both economic and environmental benefits. • Efficiency of waste based packed-bed TES is in the range of 79%–82 %. • Tundish waste, with the highest heat capacity, requires the least storage volume. [ABSTRACT FROM AUTHOR]

The real-time change of solar radiation intensity leads to the instability of the outlet temperature of the collector, which has an important influence on the thermal performance of the thermal energy storage system. Therefore, the dynamic thermal performance of a packed-bed latent heat storage system integrated with a solar parabolic trough collector is studied in this paper. Moreover, the effects of different mass flow rates on the total charging capacity, total exergy input, total exergy storage and exergy efficiency of the system are investigated. The result indicates that the steady-state and unstable-state inlet boundary conditions show significant differences in thermal performance. Under the unstable-state boundary conditions, when the mass flow rate increases from 0.1 to 0.2 kg/s and 0.1–0.4 kg/s, the maximum temperature difference between the PCM capsules and the air decreases to 24.11% and 47.39%, respectively. The larger the mass flow rates, the smaller the temperature difference, which is the opposite of the steady-state situation. Under steady-state inlet temperature conditions, the exergy efficiency gradually decreases with the increase of mass flow rate. Under unstable-state inlet temperature conditions, the mass flow rate has little effect on the exergy efficiency, and which is about 41.00%. • The packed-bed latent heat storage system integrated with the solar parabolic trough collector is modeled. • The thermal performance under the steady-state and unstable-state inlet boundary conditions is compared. • The instantaneous energy efficiency decreases as the mass flow rates increases. • The exergy efficiency is about 41.00% under unstable-state inlet temperature conditions. [ABSTRACT FROM AUTHOR]

The viscosity η m of dense fluid mixtures of carbon dioxide and ethanol was determined from the pressure drop between the inlet and outlet of a packed bed using the Ergun equation at temperatures from 313.2 K to 343.2 K and pressures from 15 MPa to 30 MPa over the entire range of ethanol composition. The η m values for the fluid mixtures decreased with increasing temperature and increased with increasing pressure under isocratic conditions. In addition, the values measured η m with Ergun eq. were correlated with the equation combining the Eyring theory and the perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) and with that based on the rough hard-sphere (RHS) model proposed by Dymond and Assael. The accuracies of the Eyring + PC-SAFT EoS and the RHS model were 8.7% and 12%, respectively, in terms of average relative deviation for 80 conditions over the entire range of ethanol composition. [Display omitted] • Ergun equation described pressure drop of dense CO 2 +ethanol flowing in packed bed. • Constants in Ergun equation were modified as functions of temperature and pressure. • Viscosity of dense mixture was determined in packed bed by Ergun equation. • Combined method of Eyring theory+PC-SAFT EoS well expressed CO 2 +ethanol viscosity. [ABSTRACT FROM AUTHOR]

The current paper investigates the radial gradient arrangement of phase change material capsules effect on the thermal behavior of a packed-bed latent thermal energy storage system. A transient two-dimensional dispersion-concentric model is developed to analyze the phase transition of phase change materials. Moreover, the heat transfer characteristics between air and phase change material capsules in four different packed bed systems are discussed in detailed. The results indicate that the use of radial gradient arrangement in the phase change material capsules significantly enhances the heat transfer performance of the system. The system pressure drop is apparently decreased when the radial gradient arrangement is taken into consideration. From case 1 to case 4, the overall energy efficiency is 84.16%, 80.43%, 83.55%, and 82.46%, respectively. The capacity ratio of case 1 is higher than all studied cases by 5.03%, 1.11%, and 3.74%, respectively. The utilization ratio of case 1 is higher than all studied cases by 5.15%, 1.45%, and 3.43%, respectively. Furthermore, considering the loss of pressure drop, it is found that case 3 is the most viable option of all the studied cases. This study provides a numerical basis for the thermal stability output and the structure optimization of packed bed system. • A new packed-bed LTES system with radial gradient arrangement is suggested to improve the thermal performance. • The thermal performance of four different layouts is compared. • The radial gradient arrangement is proposed to reduce the pressure drop. • The use of radial gradient arrangement significantly enhances heat transfer performance of the system. [ABSTRACT FROM AUTHOR]

Based on the local thermal non-equilibrium theory, a modified transient two-dimensional numerical model is developed to investigate the simultaneous charging and discharging performance of a molten-salt packed-bed thermocline tank employed in concentrated solar power plants. Two different types of operation including that of stable and periodic charging with steady discharging are analyzed. Three different solid fillers are utilized, including quartzite rock, slag pebbles, and alumina ceramics. The effects of charging/discharging flow rate ratio and non-charging periods on thermocline thickness and energy storage power have been investigated. The results show significant influences of the charging/discharging flow rate ratio. When charging is steady, the discharge performance of a packed-bed tank is better than that of a pure molten-salt tank at lower flow rate ratios. The thermocline thickness of the packed-bed tank is higher than that of a pure molten-salt tank for different solid materials. Compared with quartzite rock and slag pebbles, alumina ceramics achieves a higher thermal gradient. In periodic charging mode, as the cycle's number of charging periods increases, thermocline thickness increases linearly. Operating at higher charging rates and shorter non-charging periods, the discharge outlet temperature of molten-salt becomes more stable for the steam generation process and hence, the discharge performance is improved. [Display omitted] • Simultaneous operation of molten-salt energy storage in porous packed-bed tank presented. • Local non-equilibrium thermal model for simultaneous operation adopted. • Periodic and stable charging with simultaneous discharging process of molten-salt tank investigated. • Influences of flow rate mixing ratio, non-charging period and charging flow rate revealed. [ABSTRACT FROM AUTHOR]

• Laboratory scale packed bed TES was developed to store heat at medium temperatures. • The new STESM developed from demolition wastes was used as packing material. • Demolition waste as STESM was more efficient and cheaper than alternatives. • The results from lab-scale packed-bed with new STESM will be valuable for scaling up. Thermal energy storage (TES) is essential for cost-effective use of solar energy in industries. The most energy intensive processes in industry operate below 200 °C. This study tested a new sustainable and low-cost sensible thermal energy storage material (STESM) based on demolition wastes in a lab-scale packed bed TES system, specifically built to analyze its performance in industrial solar applications below 200 °C. This system was investigated both experimentally and numerically under different operating conditions. One-dimensional continuous phase model used verified that experimental results were in good agreement with numerical ones during charging and discharging steps. Performance of demolition waste STESM was compared with Therminol 66 synthetic oil as a liquid heat storage media. The maximum system energy efficiency of the packed-bed filled with demolition waste STESM was 67% at charging temperature of 150 °C and superficial fluid velocity of 0.95 mm s−1, while it was 63% for Therminol 66. Packed bed TES system with demolition waste STESM showed good performance up to 180 °C in fully laminar flow regime (Re p < 10) and Bi number < 0.1. The material cost of demolition waste STESM is at least tenfold cheaper than the alternative natural rock based packing materials. Packed bed TES systems using demolition wastes can be recommended for low cost and sustainable solar applications in industry. [ABSTRACT FROM AUTHOR]

• Steel making slag pebble as reliable storage medium in central receiver systems. • Metallurgical by-product waste revalorized as a cost-effective storage material. • Comparison between slag pebble and other thermocline filler materials. • Slag pebble used as packed-bed filler in a solar hybrid storage configuration. • The pumping tanks allow to increase the maximum thermocline tanks storage capacity. This work focuses on the reliable use of the steel making slag pebble as filler material of thermocline tanks which are combined with conventional molten salt tanks in a hybrid thermal storage configuration. The use of this hybrid configuration not only improves the efficiency and operation of the plant when there is solar radiation fluctuation but also includes pumps in separate molten salt tanks in order to increase the maximum height of the thermocline tanks and its useful storage volume, i.e. its storage capacity. A packed-bed numerical model has been used to study the potential of the slag pebbles in this hybrid storage configuration, comparing it against other well-known potential filler materials for thermocline tanks as the taconite and quartzite rock. The study carried out considers a storage capacity of 9 full load hours for a central receiver system of 110 MWe gross power. The results show that two thermocline tanks of 20 × 20 m, filled with steel making slag pebbles, reaches a capacity of 6.61 full load hours. An economic analysis is included which shows that the hybrid storage solution using slag pebbles represents a cost reduction of 13.7% against the state of the art solution. Additionally, comparing it against other filler materials, the slag hybrid storage solution has a cost reduction of 3.8% and 13% against the quartzite and taconite hybrid storage solution, respectively. [ABSTRACT FROM AUTHOR]

Highlights • High-temperature packed-bed thermal energy storage of volume 175,000 m3 is studied. • One-dimensional, two-phase transient model is developed. • Parametric study is carried out to analyze the dynamic behavior. • Energy and exergy efficiencies exceeded 98% for most of the cases investigated. Abstract The packed-bed thermal energy storage technology has gained a significant market worldwide as it offers a huge potential for high-temperature air based storage with no adverse environmental impact. The present paper numerically investigates a high-temperature 175,000 m3 truncated conical shaped packed-bed thermal energy storage. One-dimensional, two-phase model is developed to simulate the transient behavior of the storage where the energy balance of both phases, the fluid and the solid, are based on modified equations of the Schumann model. The model developed is used to carry out a parametric study where it is subjected to different design and operating parameters such as storage shape, rock diameter, charge-discharge rate and insulation thickness. The storage performance is assessed through energy and exergy efficiencies taking energy stored and recovered into account. The model satisfactorily predicts the dynamic behavior of a large-scale packed-bed storage system within the range of parameters investigated. Results obtained denote that the truncated conical shaped storage with rock diameter of 3 cm, insulation thickness up to 0.6 m and charging-discharging rate of 553 kg/s leads to lower thermal losses estimated under 1% of the energy recovered during discharge. Furthermore, energy and exergy efficiencies of thermal cycles are found to exceed 98% for most of the selected parameters in the study. The model developed can assist in identifying more advance and cost-effective storage design solutions for a large-scale application. [ABSTRACT FROM AUTHOR]

The paper aims to study the impact of Thermal Energy Storage (TES) technology on the dynamic characteristics of Concentrated Solar Power (CSP). An integrated dynamic model of a CSP plant is firstly established, which combines the concentrating system, the TES system, and S–CO 2 Brayton power cycle system. Three TES alternatives are considered: two-tank molten salt TES (TT-TES), packed-bed TES with solid fillers (PBS-TES), packed-bed TES with phase change materials (PBP-TES). Using this integrated dynamic model, the thermal performance and economic feasibility of different TES technologies applied to CSP are compared and analyzed. The results indicate that utilization of packed-bed TES primarily impacts the optical efficiency of the heliostat field and the thermal efficiency of the power cycle, while having minimal effect on the receiver's thermal efficiency. Furthermore, during the vernal equinox, the daily average system efficiencies of CSP configurations integrating TT-TES, PBS-TES, PBP-TES technologies are 26.0 %, 25.5 %, and 24.5 %, respectively. Meanwhile, the use of packed-bed TES systems significantly reduces the material cost of the TES. In comparison to the TT-TES, the PBP-TES and the PBS-TES can reduce cost by 21.2 % and 42.3 %, respectively, and decrease TES volume by 83.0 % and 63.8 %, respectively. • An integrated dynamic model of a concentrated solar power is established. • The influence of three TES technologies on the dynamic characteristics of CSP is studied. • The TES technologies include two-tank molten salt TES, packed-bed TES with solid fillers, and packed-bed TES with PCMs. • Packed-bed TES affects charging and discharging processes, causing energy loss. • Packed-bed TES reduces cost and volume compared to two-tank molten salt TES. [ABSTRACT FROM AUTHOR]

Abstract This work investigates the behavior during freeze-drying of packing structures formed by spray-frozen microparticles. A multi-scale approach is used to study spray freeze-drying, and in particular, mass transfer during primary drying and its duration. The procedure starts with the generation of realistic packings of microparticles using DEM, and CFD simulations are used to determine some relevant characteristics at pore scale, i.e., porosity, tortuosity, the average size of the particle-to-particle voids, and permeability. Finally, these parameters are used to describe mass transfer within the packed-bed. This procedure is used to describe some actual case studies and evaluate drying time and mass transfer resistance within the packing. We also investigated the role of packing structure on freeze-drying by generating packings from monodisperse and Gaussian-polydisperse microparticles, demonstrating that polydispersity increased the mass transfer resistance, and, finally, drying time. Graphical abstract Unlabelled Image Highlights • A multi-scale approach was proposed to investigate freeze-drying of microparticles. • DEM and CFD were used to estimate structural parameters of microparticles in packed-bed. • The procedure was experimentally validated upon data from the literature. • Packing structure had a significant influence on mass transfer resistance and drying time. [ABSTRACT FROM AUTHOR]

Highlights • The valorisation of steel slag as low cost TES material is proposed. • The compatibility between a molten nitrate salt (Solar Salt) and steel slag is investigated. • All corrosion mechanisms occurring between the salt and the slag are not detectable with XRD and SEM. • A deeper analysis of the salt and slag chemical compositions revealed a migration of cations. • The migration mechanism leads to the modification of the thermo-physical properties of the salt. Abstract Thermal energy storage (TES) systems based on packed bed arrangements are proven to be a very promising route to decrease the levelized cost of electricity (LCOE) in concentrated solar power (CSP) plants. However, the compatibility between the TES material and the heat transfer fluid (HTF), which operate in direct contact, is known to be a major limitation for such configuration. In this regard, the compatibility between a molten nitrate salt (Solar salt) and a ceramic by-product from the steel production, the steel slag, is investigated in this work. The obtained results show that the standard criteria used for determining any chemical incompatibility phenomena like the formation of a corrosion layer or the appearance of structural modifications, are not enough to draw a conclusion on the materials compatibility. A deep analysis of the TES material and the HTF chemical compositions revealed a migration of cations from the slag to the salt, and the formation of nitrites in the latter boosted by the presence of the slag. These two mechanisms lead to the modification of the thermo-physical properties of the salt. [ABSTRACT FROM AUTHOR]

Molten-salt packed-bed thermal energy storage using thermocline technology is more cost-competitive than the conventional two-tank thermal energy storage, due to its integrated design and the employment of a low-cost packed-bed. However, such a storage configuration suffers the main drawback of a low capacity factor when applied to concentrating solar power because of the adoption of conservative cut-off temperatures. The present work evaluates the feasibility of taking less conservative cut-off temperatures to improve the utilization of the packed-bed thermal energy storage from the perspectives of a system-level operation and storage economy. The investigations are carried out on two levels. The first-level investigation reveals the effects of both the charging and discharging cut-off temperature on the thermal performance of the packed-bed thermal energy storage under ideal operating conditions. Three typical packed-bed configurations are involved. The results show that the capacity factor of the packed-bed thermal energy storage increases as the charging cut-off temperature increases and the discharging cut-off temperature decreases, especially for the configurations using latent-heat when the adopted cut-off temperatures jump over the phase change points of the encapsulated phase change materials. The second-level investigation discusses the impacts of different levels of deep charges (using high charging cut-off temperatures) on the scale design of the packed-bed thermal energy storage, the daily operation of the low temperature molten-salt pump (LT-pump) and the central receiver of a 100 MW e conventional concentrating solar power tower plant. The results indicate that a deeper charge operation is always accompanied with a smaller required packed-bed size as well as a higher required delivery capacity and higher pressure head of the LT-pump and that it always results in a larger daily pumping consumption, a higher peak inlet temperature ramping rate and a higher receiver pressure drop. The maximum allowable charging cut-off temperature is identified to be 500 °C for each packed-bed configuration, according to the operating limitations on the pump and receiver. Moreover, a cost analysis is carried out to obtain the optimum charging cut-off temperature for each packed-bed configuration. The obtained results show that performing deep charges with the cost-optimized charging cut-off temperatures can effectively improve the cost competitiveness of the molten-salt packed-bed TES integrated into concentrating solar power plants. [ABSTRACT FROM AUTHOR]

Yersiniabactin, a nonribosomal peptide-polyketide complex natural product with a strong affinity for metals, was immobilized to a polymeric XAD16 resin (forming Ybt-XAD) and used as packing for a successive series of columns designed for scaled removal of Cu 2+ , Mg 2+ , and Ni 2+ from industrial wastewater. Ybt-XAD showed regenerative capacity for two cycles in metal removal and a relatively higher degree of selective for copper within the largest column (5 × 50 cm). System pH variation influenced metal removal and the potential for metal recovery (or stripping) from the column setup. The system was also characterized using Thomas and dose response models for the 2.5 × 10 cm column, providing valuable information on the resin capacity of Cu 2+ , Mg 2+ , and Ni 2+ to inform future column designs for enhanced metal removal. [ABSTRACT FROM AUTHOR]

In the study, a transient, two-dimensional and axisymmetric model of the packed-bed thermocline tank is developed. Based on the model, the cyclic thermal performance of a traditional Single-Layered and of a novel Multi-Layered Packed-Bed molten salt Thermocline Tank (SLPBTT, MLPBTT) are analyzed. First, the analysis of cyclic thermal performance of SLPBTT shows the performance can be enhanced by reducing the retention thermocline thickness. Second, this is the first time for a detailed investigation of the expanding and the shortening effects on thermocline thickness at the interface between two kinds of filler. In addition, a novel MLPBTT is designed utilizing the above interface effects for improving the performance by controlling thermocline expansion. Finally, the studies on the performance of MLPBTTs adopting three fillers (quartzite rock, cast iron, and high-temperature concrete) with different heights present that the useful energy can be increased while thermal efficiency will be reduced with the increasing cast iron's height. An optimized MLPBTT shows a significant improvement in the useful energy of 10.5% and a small drop in thermal efficiency of 2.1% in discharging process compared with those of SLPBTT using the quartzite rock. The results can be beneficial for the design and optimization of PBTT. [ABSTRACT FROM AUTHOR]

Packed-bed thermal energy storage (PBTES) systems utilizing phase change capsules have found extensive applications in thermal energy harvesting and management to alleviate energy supply-demand imbalances. Nevertheless, the sluggish thermal charging rate of phase change materials (PCMs) capsules remains a significant impediment to the rapid advancement of PBTES. Here, bionic PCMs capsules are proposed by mimicking the internal and external structure of chloroplast-granum. The heat transfer and flow characteristics of the bionic PCMs capsules in the packed-bed are analyzed by experiments and numerical simulations. The results illustrate that the chloroplast-fin type PCMs capsule exhibits significantly faster heat storage compared to the sphere type PCMs capsule. This improvement is attributed to the bionic folded shape and inner membrane structure, which generate multiple local vortices to enhance heat convection, and shorten the heat transfer distance between the capsule wall and center PCMs to facilitate heat conduction. The PCMs capsules are further filled into the packed-bed in a staggered arrangement, resulting in increased heat transfer area and enhanced disturbance flow as compared to an aligned arrangement. Consequently, the melting time of the packed-bed filled with chloroplast-fin type capsules is reduced by 33.2%, meanwhile the average exergy storage rate and exergy efficiency are enhanced by 48.4% and 8.3%, respectively, compared to the packed-bed filled with sphere type capsules. This research offers a novel approach for designing high-performance PBTES system utilizing bionic capsules. • Chloroplast-granum inspired PCMs capsules are proposed for fast thermal charging. • Heat transfer mechanism is revealed for the bionic capsules and the packed-beds. • Chloroplast-fin type PCMs capsules reduce the melting time by 49.9%. • Packed-beds with bionic capsules increase the exergy efficiency by 8.3%. [ABSTRACT FROM AUTHOR]

Numerical simulations of chromatography are conventionally performed using reduced-order models that homogenize aspects of flow and transport in the radial and angular dimensions. This enables much faster simulations at the expense of lumping the effects of inhomogeneities into a column dispersion coefficient, which requires calibration via empirical correlations or experimental results. We present a high-definition model with spatially resolved geometry. A stabilized space–time finite element method is used to solve the model on massively parallel high-performance computers. We simulate packings with up to 10,000 particles. The impact of particle size distribution on velocity and concentration profiles as well as breakthrough curves is studied. Our high-definition simulations provide unique insight into the process. The high-definition data can also be used as a source of ground truth to identify and calibrate appropriate reduced-order models that can then be applied for process design and optimization. • Stabilized space–time finite element method used on massively parallel computers. • Packed bed chromatography simulated at unprecedented spatial resolution. • Packings with up to 10.000 particles simulated. • Impact of particle size distribution and wall effects on band broadening quantified. • Calibration data for reduced order models generated. [ABSTRACT FROM AUTHOR]

The sensible heat storage in low-cost secondary fillers using a single tank thermocline system offers a cost-effective storage option for concentrating solar power (CSP) plants. A comprehensive numerical simulation of 125 MWh t thermocline tank is performed by adopting a transient, two-dimensional, two-phase model to investigate the thermal performance of packed-bed thermocline thermal energy storage (PBTC-TES) system. The effect of relevant design and operating parameters on the performance of TES system are examined by analysing the thermocline expansion and local variation of salt and filler temperature. It is observed that the operating temperature difference (ΔT) has ample role on thermal performance of TES system as the efficiency is found to reduce by 12% with increase in ΔT from 50 K to 150 K. Discharging efficiency is estimated to be high at low operating temperature ranges and tend to decrease with increase in ΔT. Also with increase in power output, discharging efficiency tends to reduce slightly since it demands higher flow rates and operating temperature range. In case of inlet salt velocity, discharging efficiency drops by 3.5% when velocity is increased thrice the initial value. Further, a comparative study is performed to figure out the most dominant efficiency determining operating parameter. It is observed that relative to inlet salt velocity, operating temperature range seems to have more influence on the thermal performance of TES system. When the operating range is increased from 50 to 150 K, efficiency drops by about 10% whereas a reduction of only 2.5% is observed when power output is increased from 15 to 35 MW t for similar ΔT values. Hence, operating temperature range is identified as the dominant efficiency determining parameter of PBTC-TES system. [ABSTRACT FROM AUTHOR]

In a recent paper, box-shaped or cuboid packed bed devices have been proposed as alternative to columns for chromatographic separations. We first propose a mathematical model for residence time distribution in such devices. Based on it, we examine factors likely to affect separation performance, and verify the predictions of our mathematical model by conducting tracer experiments. We then compare the performance of two commercial columns with their respective equivalent cuboid packed-bed devices, i.e. containing the same chromatographic media, and having the same bed-height and bed-volume. Parameters compared include the number of theoretical plates, attributes of flow-through and eluted protein peaks, and resolution in model binary protein separations. For each of these metrics examined, the cuboid packed-bed device outperformed its equivalent commercial column. Other potential advantages likely to be gained from using a cuboid packed-bed instead of a column are elucidated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient nitrogen removal was achieved under influent nitrate and temperature variation. • Nitrate removal loading was more sensitive to temperature than other factors. • Nitrogen gas was the prominent inducement to clogging. • Using gas-venting could save 90% time and energy than conventional back-washing. • No functional instability or "treatment short-circuit" occurred in S0AD biofilter. Elemental sulfur autotrophic denitrification (S0AD) is viewed as a promising alternative to conventional heterotrophic denitrification due to lower running costs, zero carbon dioxide emission, and minimum excess sludge production. However, its scale-up capability and robustness in treating real-life wastewater have not been convincedly demonstrated. In this study, a pilot-scale S0AD packed-bed with over 1000 m3/d of actual wastewater treatment capacity was operated for 197 days. The S0AD packed-bed could effectively remove nitrate to below 12 mg-NO 3 −-N/L that is 20% stricter than China's national standard (15 mg-TN/L). The temperature effect coefficient Q 10 was calculated as 1.01, illustrating that denitrification efficiency could be doubled when the temperature increased every 10 °C. Mass balance calculations indicated that 85% of removed nitrate was contributed by S0AD process, and the rest 15% was by heterotrophic and assimilative processes. A total of 2684 kg sulfur was consumed during the course of the experiment which was attributed to 16.1% DO oxidation and 83.9% denitrification. Nitrogen gas produced through denitrification, could be trapped in the S0 packed-bed that was the primary causality of clogging. Daily gas venting instead of conventional back washing, could effectively recover the packed-bed flux and promote denitrification efficiency. In addition, a weekly thorough back washing was deemed necessary to deeply clean the trapped SS and sloughed overgrowing biofilm. The predominant S0AD bacteria belonged to the genus Thiobacillus, was enriched throughout the packed-bed providing robust and stable denitrification. Overall, we provided some guidance to the design and operation of S0AD packed bed in practical engineering. [ABSTRACT FROM AUTHOR]

• Unified thermo-economic optimisation framework for compressed-air energy storage. • Comparison of different configurations and materials at different scales. • Packed-bed stores perform better than liquid stores under the studied conditions. • Roundtrip efficiencies of up to 76% can be attained by these systems. • Costs of 140 $/kWh and 970 $/kW can be achieved for 50 MW and 300 MWh systems. Compressed-air energy storage is an attractive option for satisfying the increasing storage demands of electricity grids with high shares of renewable generation. It is a proven technology that can store multiple gigawatt hours of electricity for hours, days and even weeks at a competitive cost and efficiency. However, compressed–air energy storage plants need to be designed carefully to deliver these benefits. In this work, a consistent thermo-economic optimisation framework is applied to assess the performance and costs of different compressed–air energy storage configurations across different scales. Special attention is paid to the thermal energy stores, with both solid packed-bed stores and liquid stores examined as viable options for advanced compressed–air energy storage plants and different storage materials proposed for both options. The comprehensive thermo-economic optimisation, considering different system layouts, thermal energy storage technologies and storage materials, and system scales is a key novelty of the presented work. A configuration with two packed–bed thermal energy stores using Basalt as the storage material is found to perform best, achieving an energy capital cost of 140 $/kWh, a power capital cost of 970 $/kW and a roundtrip efficiency of 76% at a nominal discharge power of 50 MW and a charging / discharging duration of 6 h. The best-performing liquid storage material is solar salt, which is associated with an energy capital cost of 170 $/kWh and a power capital cost of 1,230 $/kW. Systems with liquid thermal energy stores however are found generally to perform worse than systems with packed–bed thermal energy stores both in terms of cost and efficiency across all scales. [ABSTRACT FROM AUTHOR]

The lack of mass-producible, high-performance medium-high temperature phase change materials (PCMs) is one of the core problems restricting the efficient utilization and application of renewable energy. In this paper, a new type of composite phase change materials (CPCMs) based on starch pore-forming porous SiC ceramic skeleton combined with high enthalpy ternary chloride (NaCl–KCl–MgCl 2) is proposed. The preparation process of CPCMs is optimized, and many characterization and experimental studies are carried out. The SiC skeleton with adjustable porosity (48%–75%) and robust structure is obtained by simple starch pore-forming, cold pressing, and high-temperature sintering. After 200 repeated charging-discharging cycles, the structure of the SiC skeleton/paraffin composite (porosity: 60%; thermal conductivity: 19.72 W m−1 K−1) is intact, with no obvious leakage and only a 3.06% decrease in thermal conductivity, which proves its excellent cycle thermal stability. The thermal conductivity of the CPCMs-60% impregnated with ternary chloride under negative pressure is 22.65 W m−1 K−1, and the effective heat storage density is 513.462 kJ kg−1 in the temperature range of 300–500 °C. In addition, a large number of cylindrical CPCMs batteries are fabricated by this process, and a series of systematic experimental studies are carried out in the laboratory. The temperature changes throughout the charge-discharge process and the effects of the flow rates of different heat transfer fluids on the thermal performance of the system are studied in detail. All of them verified the high charge-discharge rate and thermal performance of CPCMs batteries. This work provides a promising strategy for the development and industrial application of high-temperature packed bed heat storage systems for renewable energy integration. [ABSTRACT FROM AUTHOR]

Chemical looping combustion with methane as fuel in a packed-bed reactor using Ni as oxygen carrier was numerically investigated. To this aim, a mathematical model that takes into account both oxidation and reduction phases was developed. To describe catalyst fouling due to carbon deposition, CH 4 decomposition and carbon regasification by steam and CO 2 (Boudouard reaction) were considered during reduction phase, while carbon combustion was taken into account during oxidation phase. A catalyst deactivation function due to carbon accumulation on oxygen carrier was introduced too. In the paper the effects of fouling on the operability of packed-bed reactor was studied, focusing the attention on the switch strategy adopted. Results show that a detailed description of carbon deposition and consumption phenomena is an essential prerequisite to properly operate a CLC process. Indeed, it was found that working with variable oxidation and reduction time lengths, the power produced is about three times greater than of that obtainable operating with fixed times. Although carbon deposition can be also reduced by increasing the H 2 O:CH 4 feed ratio, it was found that in this case the power produced decreases by about 30% with respect to that obtained operating with variable oxidation and reduction time lengths. [ABSTRACT FROM AUTHOR]

Selective metal removal from aqueous samples has wide-spanning environmental applications as well as implications in precious or rare metal recycling. In this work, a heterologous biosynthetic system was used to produce the natural product yersiniabactin (Ybt) for incorporation into a metal removal water treatment operation. Specifically, Ybt was adsorbed to resin within a packed-bed column prototype to continuously remove copper from water samples with results that included: 1) >80% removal capability; 2) variation in removal across pH levels, providing an opportunity for in situ resin regeneration and metal recovery; 3) selective removal from a copper-zinc mixture; and 4) application to environmental field water samples. In summary, the combined biosynthetic and recovery processes offer an alternative opportunity for selective removal of copper and other metals contaminating water samples. [ABSTRACT FROM AUTHOR]

Columns with relatively short bed-height to diameter ratios are frequently used for process-scale chromatography applications such as biopharmaceutical purification. Non-uniform flow distribution within such columns could result in broad and poorly resolved eluted peaks, which could in turn affect purity, recovery and productivity of the process. Different strategies centered on improved column header design have been proposed for addressing this problem. This paper describes a radically different approach, i.e. the use of a chromatography box (or chromato-box) instead of a column, for addressing the challenges posed by flow mal-distribution in process-scale, packed-bed chromatography devices. The design of the chromatography box devices used in this study is based on a laterally-fed membrane chromatography (or LFMC) device, that has been described and discussed in several recent papers. The performances of two chromatography box devices were compared with their equivalent columns in terms of sharpness and asymmetry of flow-through and eluted peaks, number of theoretical plates per metre, and peak resolution in binary and ternary protein separations. In each of the above comparisons, the chromatography box devices performed better than their equivalent columns, clearly indicating their potential as an alternative in process-scale chromatography applications. [ABSTRACT FROM AUTHOR]

This paper presents the theoretical investigations of thermal performance characteristics of solar air heater having its duct packed with blackened wire screen matrices. The heat transfer equations for two dimensional fully developed fluid flow under quasi-steady state conditions have been developed in order to analyze the thermal efficiency and temperature rise and to study the effect of system and operating parameters. Finite difference solution algorithm has been developed for obtaining numerical solutions of the governing equations for energy transfer. A computer programme is developed in C++ language to estimate the temperature rise of the entering air for evaluation of thermal efficiency by solving the governing equations numerically using relevant correlations for heat transfer coefficient for packed bed systems. Results of temperature distributions and other performance parameters obtained from analysis have been compared with available experimental results. The percentage deviation between the experimental and the analytical values of the dimensionless air temperatures of air and thermal efficiency have been found to be in the range of 7.18 to -9.83 and 7.20 to -9.65 respectively. This establishes the validity of proposed analytical model for the investigation of thermal performance characteristics of packed bed solar air heaters. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D radiation model was solved by Monte Carlo method. • Interactions between photons and TiO 2 -coated glass rings are considered. • Presence of undesirable dark zones in the reactor can be evidenced and minimized. • Film thickness and illumination can be adjusted to get uniform photon distribution. • Useful information for design and optimization of photocatalytic reactors is given. A photocatalytic reactor under UV-LED illumination is presented. It is an annular, packed-bed reactor filled with TiO 2 -coated glass rings. The reactor is irradiated both internally and externally in order to minimize the presence of dark zones. The knowledge of the radiation distribution inside the reactor is a key aspect to optimize its design and improve its efficiency. A three-dimensional model has been developed to describe the distribution of the local rate of photon absorption inside the reactor. The Monte Carlo method was applied to solve the radiation model. Simulation results were validated with experimental measurements. The model was able to predict the influence of the catalyst film thickness and the illumination conditions on the radiation distribution and on the total rate of photon absorption. Also, degradation assays of the pharmaceutical clofibric acid were carried out in the reactor and the performance of different illumination conditions was evaluated by means of the quantum efficiency parameter. [ABSTRACT FROM AUTHOR]

In the present work the numerical analysis of an autothermal chemical looping reforming (CLR) packed-bed reactor for hydrogen production is presented. The reactor works with Ni-based oxygen carriers, methane is used as fuel and continuous cyclic operations are simulated. The proposed process poses a number of challenges, namely the choice of the time-length of oxidation and reduction phases, the start-up temperature and the cycle design. This paper theoretically quantifies these challenges through numerical simulations. A 1D numerical reactor model, validated by comparison with experimental data available in literature, was developed. Results for the cyclic process are presented, and the effects on the feasibility of the process of a variation in operating conditions are discussed. It is concluded that an appropriate choice of both the initial temperature and the length of oxidation and reduction phases is essential prerequisite for the process feasibility and performances. [ABSTRACT FROM AUTHOR]

The purpose of this study is mainly to investigate the performance of a packed-bed continuous-recirculation flow reactor at high applied electric current in removing copper, Cu(II), from simulated electrolyte by electrodeposition. The effects of pH o , circulation rate of flow, initial copper concentration, intensity of the applied current and the method of application of electric current, as to have a constant value during all the time of electrolysis or to be decreased with time, on copper electrodeposition and current efficiency are revealed. The results showed that the increase in pH (provided not lead to the deposition of Cu(OH) 2 ), initial concentration of the copper and flow rate increased the electrodeposition of copper as well as improved current efficiency. However, increasing intensity of the applied electric current led to an increase in the electrodeposition of copper and decreased electrical efficiency. It was also observed that reducing the intensity of applied electric current with time during the electrolysis process while maintaining other operating variables constant led to a significant reduction in the consumption of electrical energy used in the process of copper removal by electrodeposition; a reduction of 41.6% could be achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different particles have been developed and tested for application in a packed-bed CLC reactor. [•] Ilmenite was chosen as base material due to its good reactivity with syngas, the natural availability and related low cost. [•] A suitable oxygen-carrier was developed using ilmenite as base material and Mn2O3 as additive. [•] No significant differences in the reduction and oxidation reactivity of the different granules were observed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dynamic thermal performance of a molten-salt packed-bed TES system using PCM capsules was investigated. [•] The temperature response and phase change process within PCM capsules were revealed. [•] A quasi-isothermal region and two thermocline regions were identified for the axial molten-salt temperature distribution. [•] PCT of PCM, molten-salt inlet velocity and capsule diameter influence the effective discharging efficiency. [Copyright &y& Elsevier]

A high-speed purification system made of packed-bed adsorber is often subject to apparent demerits (e.g., pressure drop and/or high energy consumption) when treating waste gas. As a potential alternative to such system, a denuder sorbent tube has been constructed by coating powder-activated carbon (PAC) on the inner surface of the sorbent tube with the help of polyvinyl alcohol (PVA) as adhesive. The designed denuder sorbent tube was then used to treat a gaseous stream containing 1 Pa benzene (as a model volatile organic compound (VOC)) under various volumetric flow rates (100–500 mL·min−1). The results revealed that the designed packed bed outperformed the denuder system by a factor of at least two (in terms of the breakthrough volume (BTV, L·g−1) and adsorption capacity (Q, mg·g−1) at 10% BT) when tested at upper flow rates (200–500 mL·min−1). In contrast, the pattern was reversed at the lowest flow rate of 100 mL·min−1 so that the denuder (BTV 10% = 615 L·g−1) outperforms the packed bed (330 L·g−1). According to the adsorption kinetic analysis, the surface-interaction and film diffusion have a rate-determining adsorption step in the denuder, while the boundary/pore diffusion mechanism should play a crucial role in the packed-bed system. Overall, the PAC-based denuder system is recommendable in removing VOCs at or near ambient conditions as an efficient alternative to replace traditional packed-bed columns. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A computational model for evaluating the performance of nano-material packed-bed filters was developed. The porous effects of the momentum and mass transport within the filter bed were simulated. For the momentum transport, an extended Ergun-type model was employed and the energy loss (pressure drop) along the packed-bed was simulated and compared with measurement. For the mass transport, a bulk adsorption model was developed to study the adsorption process (breakthrough behavior). Various types of porous materials and gas flows were tested in the filter system where the mathematical models used in the porous substrate were implemented and validated by comparing with experimental data and analytical solutions under similar conditions. Good agreements were obtained between experiments and model predictions. [Copyright &y& Elsevier]

Abstract: Applying empirical correlations to estimate various parameters used in a mathematical model is inevitable. In this study, a mathematical model is developed for a packed-bed air dehumidifier and the impact of some well-known empirical correlations available in literature is evaluated on the model's predictions and accuracy. The results reveal that in designing an air dehumidifier, using different empirical correlations may lead to very different predictions for the required bed height. The equations of Onda et al. (1968) and Rocha et al. (1996) to calculate the effective interfacial area, the equation of Treybal (1981) to calculate the heat transfer coefficient, and the equations of Chung et al. (1996) to calculate the mass transfer coefficient show precise results and increase the reliability of the mathematical models. [Copyright &y& Elsevier]

Abstract: A comprehensive transient, two-dimensional, two-phase model for heat transfer and fluid dynamics within a packed-bed molten salt thermocline thermal storage system has been developed in our prior paper. In the present paper, based on the developed model, the effects of various parameters, such as flow rate and temperature of inlet molten salt, porosity and height of the system, and the thermal losses on the thermal performance of the system, are investigated. The standby behavior focusing on the effects of wall structure, ambient air velocity on the thermocline expanding behavior is also studied. The results show that both the fluid inlet velocity and the inlet temperature have negligible influence on the thermocline development and hence the effective discharging efficiency, while increasing the tank height can effectively shrink the normalized thermocline region and lead to a higher efficiency. With good insulation, the heat losses from the standby system with a uniform initial temperature can be significantly lowered, and uniformly distributed molten salt temperature in the radial direction can be achieved. However, for the standby system with a thermocline region, the interior molten salt temperature can be influenced by the insulation layers and steel wall, causing temperature gradient in the radial direction. [Copyright &y& Elsevier]

A computational fluid dynamic (CFD) study has been carried out to simulate velocity, temperature, and concentration profiles in a vertical chemical vapor deposition (CVD) reactor used for growing carbon nanofibers (CNFs). CNFs were grown over activated carbon fibers (ACFs) wrapped over an especially designed perforated tube which was vertically mounted in the reactor. The numerical model analysis incorporated the conservation equations of momentum, energy, and species. Natural convection effects on the heat-transfer and the exothermic heat generation due to the decomposition of benzene were included. The model simulation results revealed that approximately uniform temperature and concentration profiles existed in the ACF-packed bed. In addition, multiple combinations of the heating length and the wall temperature of the reactor were possible to achieve the prescribed CVD temperature. Under the simulated CVD conditions, the present model predicted an average carbon deposition rate of 5 x 10-13 kg/m² s, which corresponded to the yield of ~0.OO5 g of CNFs per g of ACFs. The simulation results of this study are important for the optimization of the CVD operating conditions to achieve a high and uniform CNF growth in the vertical reactor. [ABSTRACT FROM AUTHOR]

Abstract: In this work, oxidation with a Fenton-like process of a dye solution was carried out in a packed-bed reactor. Activated carbon Norit RX 3 Extra was impregnated with ferrous sulfate and used as catalyst (7wt.% of iron). The effect of the main operating conditions in the Chicago Sky Blue (CSB) degradation was analyzed. It was found that the increase in temperature leads to a higher removal of the dye and an increased mineralization. However, it also increases the iron leaching, but the values observed were below 0.4ppm (thus, far below European Union limits). It was possible to reach, at steady-state, a dye conversion of 88%, with a total organic carbon (TOC) removal of ca. 47%, being the reactor operated at 50°C, pH 3, W cat/Q =4.1gminmL−1 (W cat is the mass of catalyst and Q the total feed flow rate) and a H2O2 feed concentration of 2.25mM (for a CSB feed concentration of 0.012mM). The same performance was reached in three consecutive cycles. [Copyright &y& Elsevier]

Abstract: In this paper, a comprehensive transient, two-dimensional, two-phase model for heat transfer and fluid dynamics within the packed-bed molten salt thermocline thermal storage system is presented. After model validation, the developed model is used to investigate the general thermal behavior of a discharging process of the pack-bed thermocline system and evaluate the interstitial heat transfer coefficient, the effective thermal conductivity and effect of the thermal conductivity of solid fillers. The results show that the thermocline region is moving upward with slight expansion during the discharging process. With the use of two insulation layers, a uniform cross-sectional temperature distribution is well achieved. The use of different correlations for the interstitial heat transfer coefficient or the effective thermal conductivity from the literature leads to negligible difference in the predicted thermal performance. It is also found that decreasing the heat transfer rate between fluid and solid fillers, or increasing the thermal conductivity of solid fillers, results in an increase in the thermocline thickness which finally decreases the effective discharging time and the effective discharging efficiency. [Copyright &y& Elsevier]

Abstract: CO2 adsorption in packed-bed reactors has potential applications in flue gas CO2 capture and adsorption enhanced reaction processes. This work focuses on CO2 adsorption dynamics on sodium oxide promoted alumina in a packed-bed reactor. A comprehensive model is developed to describe the coupled transport phenomena and is solved using orthogonal collocation on finite elements. The model predicted breakthrough curve matches very well with experimental data obtained from a pilot-scale packed-bed reactor. Several dimensionless parameters are also derived to explain the shape of the breakthrough curve. [Copyright &y& Elsevier]

Abstract: In this work the cell growth and inulinase production by Kluyveromyces marxianus NRRL Y-7571 were investigated in a packed-bed bioreactor. For this purpose, seven experimental runs were carried out in order to verify the influence of the inlet air temperature and volumetric air flow rate on the process dynamics. The results showed that the manipulated variables affected significantly the process performance. The best condition for enzyme production was an inlet air temperature and volumetric flow rate of 30°C and 3m3 h−1, respectively, reaching an activity of around 463Ugds−1. The results obtained here can be useful in the scale-up and optimisation of packed-bed bioreactors configuration for inulinase production. [Copyright &y& Elsevier]

Abstract: In steam reformation, high thermal resistance and poor heat transfer of the packed catalyst bed can create time-lag between the moment when the heat is applied and the corresponding rise in temperature. Thus, problems arise from the dynamic requirements of the system, which can create a time-lag in the reactor''s performance and also induce temperature oscillations resulting in a degrading catalyst. Lag compensation is necessary if one uses temperature feedback control to maintain the reactor temperature. A better solution is to recognize that heat flux is more suitable as a control variable, since available heat is what sustains the chemical reaction inside the reactor. Thus, controlling heat flux can directly influence the reaction and the resultant temperature inside the reactor. A heat flux controller is implemented for two small-scale, packed-bed, steam reformers. A standard temperature feedback controller is also implemented. The two systems are compared in their transient response. Temperature and reformate gas concentrations are measured to evaluate the performance of the two controller topologies. The heat flux based controller significantly outperforms the temperature feedback controller in both geometries tested. [Copyright &y& Elsevier]

Abstract: The possibility of using iron-based adsorbents (i.e. akaganéite or goethite) to remove heavy metal ions from aqueous solutions was the aim of the present review paper. Synthesized material was used in two forms, i.e. in fine powder of nanocrystals and in the form of grains (as granular). The main examined parameters were the quantity of sorbent, the presence of ionic strength, the pH value of solution and the metals speciation, including the presence of complexing agents. The removal efficiency of the packed-bed column was examined and compared. Typical adsorption models were discussed and the bed depth–service time equation has been applied to the sorption results in order to model the column operation. [Copyright &y& Elsevier]

Packed-bed single-tank thermocline system with reduced cost is an alternative to the conventional two-tank system for thermal energy storage. This work systematically explores the wall impact on thermocline behavior of packed-bed tanks. For this purpose, adapted transient models were developed and fully exploited for the first time. Two tank configurations were investigated and compared: a high-temperature pilot-scale tank with a steel wall and a low-temperature lab-scale tank with a polycarbonate wall, both tanks being insulated by mineral wool. Results showed that the maximum energy stored in the wall at fully charged state can be up to 10% of the total stored energy. This part of stored energy has a negative impact on the discharging, causing up to 15% increase of the thermocline thickness. The energy stored in the insulation is very small so that this phase can be simplified as a thermal resistance in the modeling. The optimal wall parameters for packed-bed TES tanks were obtained that a thinner wall has a smaller impact on the energy and exergy efficiencies at the discharging cutoff time. The findings of study could provide useful design guideline for pack-bed thermocline TES tanks for different industrial applications. • Wall effect in packed-bed thermocline storage tank is studied by dynamic modeling. • Stored heat inside wall before discharging can be up to 10%. • Longitudinal wall heat conduction can be ignored. • In discharging, the stored heat in wall increase thermocline thickness by up to 15%. • Decrease wall thickness can achieve higher energy and exergy efficiency. [ABSTRACT FROM AUTHOR]

Abstract: An experimental investigation has been carried out on a packed bed solar air heater using wire mesh as packing material. Data pertaining to heat transfer and friction characteristics were collected for air flow rates ranging from 0.0159 to 0.0347kg/s-m2 for eight sets of matrices with varying geometrical parameters. The thermal efficiency of a packed bed solar air heater was compared with that of a conventional solar air heater to determine the enhancement which was found to be strong function of system and operating parameters of the bed. It was found that an enhancement of the order of 76.9–89.5% can be obtained. Experimental data were utilised to develop correlations for Colburn Jh factor and friction factor as function of geometrical parameters of the bed and the flow Reynolds number. These correlations were found to predict the experimental results with reasonable accuracy. It has also been found that the present correlations show much better agreement as compared to the values predicted by earlier correlations for such systems. [Copyright &y& Elsevier]

Abstract: CFD simulations of trickle-bed reactors are presented with radial spreading of the liquid due to mechanical and capillary dispersion. Simulations are performed with various particle sizes and the significance of the dispersion mechanisms at the industrially relevant particle size range is analyzed. The effect of the bed porosity distribution and particle size to the simulation results is also discussed. The choice of the radial porosity profile is found to have a significant impact to the simulation results, especially when the column to particle diameter ratio, D/dp , is small, in which case the wall flow is important. The dependence of the standard deviation of porosity on the sample size is determined experimentally. Introducing just random variation of porosity to the model is found to describe inadequately the dispersive flow behavior. The presented hydrodynamic model with proper capillary and mechanical dispersion terms succeeds in capturing the features of the two independent physical phenomena. Separate models are presented for each dispersion mechanisms and it is shown that they both can have a significant contribution to the overall dispersion of liquid flowing through a packed bed. The hydrodynamic model is validated against the experimental dispersion profiles from Herskowitz and Smith [1978. Liquid distribution in trickle-bed reactors. A.I.Ch.E Journal 24, 739–454], Boyer et al. [2005. Study of liquid spreading from a point source in trickle-bed via gamma-ray tomography and CFD simulation. Chemical Engineering Science 60, 6279–6288] and Ravindra et al. [1997. Liquid flow texture in trickle-bed reactors: an experimental study. Industrial & Engineering Chemistry Research, 36, 5133–5145]. The extent of liquid dispersion predicted by the presented hydrodynamic model is in excellent agreement with the experiments. [Copyright &y& Elsevier]

Abstract: Microbial community in thermophilic methane production from organic acids in a packed-bed reactor was investigated. 16S rDNA clone analysis showed that microbial populations change with hydraulic retention time (HRT) and are different in the fermentation broth and the biofilm that was developed on the surface of supporting materials. Thermoanaerobacteriaceae was mainly found in the biofilm with hydrogenotrophic methanogens whereas clones that are affiliated to Clostridiaceae were mainly found in the fermentation broth. It is also clarified that a certain amount of unknown or unidentified organisms were present in the microflora. Hydrogen evolution and consumption activity of the microflora differed between the biofilm and fermentation broth, implying that a differential in hydrogen partial pressures is generated across the interface between the biofilm and fermentation broth. It is suggested that methanogenesis in packed-bed reactor could be accomplished by the interrelated and complementary actions of the microorganisms in the biofilm and fermentation broth. [Copyright &y& Elsevier]