Solidification enhancement in a multi-tube latent heat storage system for efficient and economical production: Effect of number, position and temperature of the tubes

Copyright: © 2021 by the authors. Thermal energy storage is an important component in energy units to decrease the gap between energy supply and demand. Free convection and the locations of the tubes carrying the heat-transfer fluid (HTF) have a significant influence on both the energy discharging potential and the buoyancy effect during the solidification mode. In the present study, the impact of the tube position was examined during the discharging process. Liquid-fraction evolution and energy removal rate with thermo-fluid contour profiles were used to examine the performance of the unit. Heat exchanger tubes are proposed with different numbers and positions in the unit for various cases including uniform and non-uniform tubes distribution. The results show that moving the HTF tubes to medium positions along the vertical direction is relatively better for enhancing the solidification of PCM with multiple HTF tubes. Repositioning of the HTF tubes on the left side of the unit can slightly improve the heat removal rate by about 0.2 in the case of p5-u-1 and decreases by 1.6% in the case of p5-u-2. It was found also that increasing the distance between the tubes in the vertical direction has a detrimental effect on the PCM solidification mode. Replacing the HTF tubes on the left side of the unit negatively reduces the heat removal rate by about 1.2 and 4.4%, respectively. Further, decreasing the HTF temperature from 15◦C to 10 and 5◦C can increase the heat removal rate by around 7 and 16%, respectively. This paper indicates that the specific concern to the HTF tube arrangement should be made to improve the discharging process attending free convection impact in phase change heat storage

Optimum placement of heating tubes in a multi‐tube latent heat thermal energy storage

Data Availability Statement: Data is contained within the article.Utilizing phase change materials in thermal energy storage systems is commonly considered as an alternative solution for the effective use of energy. This study presents numerical simulations of the charging process for a multitube latent heat thermal energy storage system. A thermal energy storage model, consisting of five tubes of heat transfer fluids, was investigated using Rubitherm phase change material (RT35) as the. The locations of the tubes were optimized by applying the Taguchi method. The thermal behavior of the unit was evaluated by considering the liquid fraction graphs, streamlines, and isotherm contours. The numerical model was first verified compared with existed experimental data from the literature. The outcomes revealed that based on the Taguchi method, the first row of the heat transfer fluid tubes should be located at the lowest possible area while the other tubes should be spread consistently in the enclosure. The charging rate changed by 76% when varying the locations of the tubes in the enclosure to the optimum point. The development of streamlines and free-convection flow circulation was found to impact the system design significantly. The Taguchi method could efficiently assign the optimum design of the system with few simulations. Accordingly, this approach gives the impression of the future design of energy storage systems.Funding: This research received no external funding

Co-pyrolysis of Rice Husk with Underutilized Biomass Species: A Sustainable Route for Production of Precursors for Fuels and Valuable Chemicals

In this study, co-pyrolysis of rice husk with underutilized biomass, Napier grass and sago waste was carried out in a fixed bed reactor at 600 �C, 30 �C/min and 5 L/min nitrogen flowrate. Two-phase bio-oil (organic and aqueous) was collected and characterized using standard analytical techniques. 34.13–45.55 wt% total boil-oil yield was recorded using assorted biomass compared to pure risk husk biomass with 31.51 wt% yield. The organic phase consist mainly benzene derivatives with higher proportion in the oil from the co-pyrolysis process relative to the organic phase from the pyrolysis of the individual biomass while the aqueous phase in all cases was predominantly water, acids, ketones, aldehydes, sugars and traces of phenolics. This study has demonstrated a good approach towards increasing valorization of rice husk in a single reaction step for the production of high grade bio-oil, which can be transformed into fuel and valuable chemicals

Optimum Placement of Heating Tubes in a Multi-Tube Latent Heat Thermal Energy Storage.

Utilizing phase change materials in thermal energy storage systems is commonly considered as an alternative solution for the effective use of energy. This study presents numerical simulations of the charging process for a multitube latent heat thermal energy storage system. A thermal energy storage model, consisting of five tubes of heat transfer fluids, was investigated using Rubitherm phase change material (RT35) as the. The locations of the tubes were optimized by applying the Taguchi method. The thermal behavior of the unit was evaluated by considering the liquid fraction graphs, streamlines, and isotherm contours. The numerical model was first verified compared with existed experimental data from the literature. The outcomes revealed that based on the Taguchi method, the first row of the heat transfer fluid tubes should be located at the lowest possible area while the other tubes should be spread consistently in the enclosure. The charging rate changed by 76% when varying the locations of the tubes in the enclosure to the optimum point. The development of streamlines and free-convection flow circulation was found to impact the system design significantly. The Taguchi method could efficiently assign the optimum design of the system with few simulations. Accordingly, this approach gives the impression of the future design of energy storage systems

Fluoridated hydroxyapatite nanorods as novel fillers for improving mechanical properties of dental composite: Synthesis and application

© 2015 Elsevier Ltd. Fluoridated hydroxyapatite (FHA) in nanorod morphology and hexagonal cross section were synthesised via hydrothermal process using Apricot Tree Gum (ATG) as a surfactant. The synthesised FHA nanorods were then used as reinforcement in bisphenol A-glycol dimethacrylate (Bis-GMA) as base monomer of composite matrix. The FHA nanorods with different ratios were incorporated in the matrix to examine fluoride ion release and pH changes in the Simulated Body Fluid (SBF) and their mechanical properties. The resin without FHA reinforcement was used as the control sample. The Diametral Tensile Strength (DTS), Flexural Strength (FS), and Flexural Modulus (FM) of the reinforced composite were found to be higher compared to the control sample; the values increased from 34.8 to 45.4. MPa, 76.5 to 99.4. MPa, and 1.7 to 2.5. GPa, respectively. Moreover, findings revealed that the pH is reduced by releasing the fluoride ions into the SBF which can be effective for preventing secondary caries. The most optimum mechanical properties were achieved with 0.2. wt% of FHA reinforcement. The FHA nanocomposite meets the minimum standard requirements for dental applications and compared to other dental composites has advantage of preventing formation of secondary caries due to release of fluoride

The fabrication and characterization of PCL/rice husk derived bioactive glass-ceramic composite scaffolds

The present study was conducted to fabricate a 3D scaffold using polycaprolactone (PCL) and silicate based bioactive glass-ceramic (R-SBgC). Different concentrations of R-SBgC prepared from rice husk ash (RHA) were combined with PCL to fabricate a composite scaffold using thermally induced phase separation (TIPS) method. The products were then characterized using SEM and EDX. The results demonstrated that R-SBgC in PCL matrix produced a bioactive material which has highly porous structure with interconnected porosities. There appears to be a relationship between the increase in R-SBgC concentration and increased material density and compressive modulus; however, increasing R-SBgC concentration result in reduced scaffold porosity. In conclusion, it is possible to fabricate a PCL/bioactive glass-ceramic composite from processed rice husk. Varying the R-SBgC concentrations can control the properties of this material, which is useful in the development of the ideal scaffold intended for use as a bone substitute in nonload bearing sites. © 2014 Farnaz Naghizadeh et al

Characterization and biological evaluation of silver containing fluoroapatite nanoparticles prepared through microwave synthesis

Nanosized hydroxyapatite is a material that is commonly used as a matrix for bone tissue engineering. Although its chemical property is similar to that of natural bone, its limited antibacterial property has made it less desirable for use in present-day clinical applications. In the present study, we have investigated the possibility of improving the antibacterial and bioactivity of hydroxyapatite, by producing nanosized silver-containing fluorapatite, using the microwave technique. Nanosized silver-fluorapatite particles were synthesized using 0.5 and 1=x fluoride through co-precipitation and the microwave refluxing treatment at 800 W, for 8 min. The crystalline phase, chemical composition, and morphology of the prepared samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The chemical analysis indicated the presence of a nanosized silver-fluorapatite phase. Transmission electron microscopy analysis showed a spheroid-like morphology, with an approximate diameter of ±76-92 nm. The bioactivity of the prepared samples, which was evaluated using simulated body fluid (SBF) immersion for 28 days, demonstrated good apatite layer formation. The antibacterial activity was evaluated using the disk diffusion method and showed good growth inhibition, while the osteoblast culture studies indicated that the presence of silver and fluoride provided superior cell attachment and growth. The antibacterial and cell culture results indicated that this new nanosized silver-fluorapatite bioceramic material had good antibacterial qualities, but remained biocompatible with osteoblasts. These findings suggested that nanosized silver-fluorapatite could potentially be used for bone regeneration applications

Solidification Enhancement in a Multi-Tube Latent Heat Storage System for Efficient and Economical Production: Effect of Number, Position and Temperature of the Tubes

Thermal energy storage is an important component in energy units to decrease the gap between energy supply and demand. Free convection and the locations of the tubes carrying the heat-transfer fluid (HTF) have a significant influence on both the energy discharging potential and the buoyancy effect during the solidification mode. In the present study, the impact of the tube position was examined during the discharging process. Liquid-fraction evolution and energy removal rate with thermo-fluid contour profiles were used to examine the performance of the unit. Heat exchanger tubes are proposed with different numbers and positions in the unit for various cases including uniform and non-uniform tubes distribution. The results show that moving the HTF tubes to medium positions along the vertical direction is relatively better for enhancing the solidification of PCM with multiple HTF tubes. Repositioning of the HTF tubes on the left side of the unit can slightly improve the heat removal rate by about 0.2 in the case of p5-u-1 and decreases by 1.6% in the case of p5-u-2. It was found also that increasing the distance between the tubes in the vertical direction has a detrimental effect on the PCM solidification mode. Replacing the HTF tubes on the left side of the unit negatively reduces the heat removal rate by about 1.2 and 4.4%, respectively. Further, decreasing the HTF temperature from 15 °C to 10 and 5 °C can increase the heat removal rate by around 7 and 16%, respectively. This paper indicates that the specific concern to the HTF tube arrangement should be made to improve the discharging process attending free convection impact in phase change heat storage