Search results for: thermal gravimetric analysis (TGA)

Authors: Raviteja Chintala

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Water shortage in many areas of the world have predominantly increased the demand for efficient methods involved in the production of drinking water, So purification of water invoking cost effective and efficient methods is a challenging field of research. In this regard, Reverse osmosis membrane desalination of both seawater and inland brackish water is currently being deployed in various locations around the world. In the present work an attempt is made to integrate these existing technologies with novel method, Wherein carbon nanotubes at the lab scale are prepared which further replace activated carbon tubes being used traditionally. This has proven to enhance the efficiency of the water filter, Effectively neutralising most of the organic impurities. Furthermore, This ensures the reduction in TDS. Carbon nanotubes have wide range in scope of applications such as composite reinforcements, Field emitters, Sensors, Energy storage and energy conversion devices and catalysts support phases, Because of their unusual mechanical, Electrical, Thermal and structural properties. In particular, The large specific surface area, as well as the high chemical and thermal stability, Makes carbon nanotube an attractive adsorbent in waste water treatment. Carbon nanotubes are effective in eliminating these harmful media from water as an adsorbent. In this work, Candle soot method has been incorporated for the preparation of carbon nanotubes and mixed with activated charcoal in different compositions. The effect of composition change is monitored by using TDS measuring meter. As the composition of Nano carbon increases, The TDS of the water gradually decreases. In order to enhance the life time for carbon filter, Nano tubes are provided with larger surface area.

Keywords: TDS (Total Dissolved Solids), carbon nanotubes, water, candle soot

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Authors: Ana Paula Gomes Nogueira, Pietro Tonolini, Andrea Bonfanti

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Automotive braking systems must convert kinetic into thermal energy by friction. Nowadays, the disc brake system is the most widespread configuration on the automotive market, which its specific configuration provides a very efficient heat dissipation. At the same time, both discs and pads wear out. Different wear mechanisms can act during the braking, which makes the understanding of the phenomenon essential for the strategies to be applied when an increased lifetime of the components is required. In this study, a specific characterization approach was conducted to analyze the worn surfaces of commercial pad friction materials and its conterface cast iron disc after dynobench tests. Scanning electronic microscope (SEM), confocal microscope, and focus ion beam microscope (FIB) were used as the main tools of the analysis, and they allowed imaging of the footprint of the different wear mechanisms presenting on the worn surfaces. Aspects such as the temperature and specific ingredients of the pad friction materials are discussed since they play an important role in the wear mechanisms.

Keywords: wear mechanism, surface characterization, brake tests, friction materials, disc brake

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Authors: Marco Picco, Mahmood Alam

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Improving the energy performance of existing buildings can be challenging, particularly when facades cannot be modified, and the only available option is internal insulation. In such cases, the choice of the most suitable material becomes increasingly complex, as in addition to thermal transmittance and capital cost, the designer needs to account for the impact of the intervention on the internal spaces, and in particular the loss of usable space due to the additional layers of materials installed. This paper explores this issue by analysing a case study of an average office building needing to go through a refurbishment in order to reach the limits imposed by current regulations to achieve energy efficiency in buildings. The building is simulated through dynamic performance simulation under three different climate conditions in order to evaluate its energy needs. The use of Vacuum Insulated Panels as an option for energy refurbishment is compared to traditional insulation materials (XPS, Mineral Wool). For each scenario, energy consumptions are calculated and, in combination with their expected capital costs, used to perform a financial feasibility analysis. A holistic approach is proposed, taking into account the impact of the intervention on internal space by quantifying the value of the lost usable space and used in the financial feasibility analysis. The proposed approach highlights how taking into account different drivers will lead to the choice of different insulation materials, showing how accounting for the economic value of space can make VIPs an attractive solution for energy retrofitting under various climate conditions.

Keywords: vacuum insulated panels, building performance simulation, payback period, building energy retrofit

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Authors: Jinyoung Kim, Jinuk Kwon, Haksoo Han

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Polyimide is widely used in electronic industries, and heat dissipation of polyimide film is important for its application in electric devices for high-temperature resistance heat dissipation film. In this study, we demonstrated a new way to increase heat dissipating rate by adding carbon black as filler. This type of polyimide composite film was produced by pyromellitic dianhydride (PMDA) and 4,4’-oxydianiline (ODA). Carbon black (CB) is added in different loading, shows increasing heat dissipation rate for increase of Carbon black. The polyimide-carbon black composite film is synthesized with high dissipation rate to ~8W∙m−1K−1. Its high thermal decomposition temperature and glass transition temperature were maintained with carbon filler verified by thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC), the polyimidization reaction of polyi(amide-mide) was confirmed by Fourier transform infrared spectroscopy (FT-IR). The polyimide composite film with carbon black with high heat dissipating rate could be used in various applications such as computers, mobile phone industries, integrated circuits, coating materials, semiconductor etc.

Keywords: polyimide, heat dissipation, electric device, filler

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Authors: Tania Sharmin

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Energy use, overheating and thermal discomfort in low-income tropical housing remains an under-researched area. This research attempts to explore these aspects in the Loving Community, a housing colony created for former leprosy patients and their families in Ahmedabad in India. The living conditions in these households and working practices of the inhabitants in terms of how the building and its internal and external spaces are used, will be explored through interviews and monitoring which will be based on a household survey and a focus group discussion (FGD). The findings from the study will provide a unique and in-depth account of how the relocation of the affected households to the new, flood-resistant and architecturally-designed buildings may have affected the dwellers’ household routines (health and well-being, comfort, satisfaction and working practices) and overall living conditions compared to those living in poorly-designed, existing low-income housings. The new houses were built under an innovative building project supported by De Montfort University Leicester (DMU)’s Square Mile India project. A comparison of newly-built and existing building typologies will reveal how building design can affect people’s use of space and energy use. The findings will be helpful to design healthier, energy efficient and socially acceptable low-income housing in future, thus addressing United Nation’s sustainable development goals on three aspects: 3 (health and well-being), 7 (energy) and 11 (safe, resilient and sustainable human settlements). This will further facilitate knowledge exchange between policy makers, developers, designers and occupants focused on strategies to increase stakeholders’ participation in the design process.

Keywords: thermal comfort, energy use, low-income housing, tropical climate

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Authors: Maryam Karimi, Rouzbeh Nazari

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Introduction: Understanding thermal distribution in the micro-urban climate has now been necessary for urban planners or designers due to the impact of complex micro-scale features of Urban Heat Island (UHI) on the built environment and public health. Hence, understanding the interrelation between urban components and thermal pattern can assist planners in the proper addition of vegetation to build-environment, which can minimize the UHI impact. To characterize the need for urban green infrastructure (UGI) through better urban planning, this study proposes the use of RayMan model to measure the impact of air quality and increased temperature based on urban morphology in the selected metropolitan cities. This project will measure the impact of build environment for urban and regional planning using human biometeorological evaluations (Tmrt). Methods: We utilized the RayMan model to estimate the Tmrt in an urban environment incorporating location and height of buildings and trees as a supplemental tool in urban planning and street design. The estimated Tmrt value will be compared with existing surface and air temperature data to find the actual temperature felt by pedestrians. Results: Our current results suggest a strong relationship between sky-view factor (SVF) and increased surface temperature in megacities based on current urban morphology. Conclusion: This study will help with Quantifying the impacts of the built environment and surface properties on surrounding temperature, identifying priority urban neighborhoods by analyzing Tmrt and air quality data at the pedestrian level, and characterizing the need for urban green infrastructure cooling potential.

Keywords: built environment, urban planning, urban cooling, extreme heat

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Authors: Surupa Shaw, Debjyoti Banerjee

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Enhancing heat transfer in compact volumes is a challenge when constrained by cost issues, especially those associated with requirements for minimizing pumping power consumption. This is particularly acute for electronic chip cooling applications. Technological advancements in microelectronics have led to development of chip architectures that involve increased power consumption. As a consequence packaging, technologies are saddled with needs for higher rates of power dissipation in smaller form factors. The increasing circuit density, higher heat flux values for dissipation and the significant decrease in the size of the electronic devices are posing thermal management challenges that need to be addressed with a better design of the cooling system. Maximizing surface area for heat exchanging surfaces (e.g., extended surfaces or “fins”) can enable dissipation of higher levels of heat flux. Fractal structures have been shown to maximize surface area in compact volumes. Self-replicating structures at multiple length scales are called “Fractals” (i.e., objects with fractional dimensions; unlike regular geometric objects, such as spheres or cubes whose volumes and surface area values scale as integer values of the length scale dimensions). Fractal structures are expected to provide an appropriate technology solution to meet these challenges for enhanced heat transfer in the microelectronic devices by maximizing surface area available for heat exchanging fluids within compact volumes. In this study, the effect of different fractal micro-channel architectures and flow structures on the enhancement of transport phenomena in heat exchangers is explored by parametric variation of fractal dimension. This study proposes a model that would enable cost-effective solutions for thermal-fluid transport for energy applications. The objective of this study is to ascertain the sensitivity of various parameters (such as heat flux and pressure gradient as well as pumping power) to variation in fractal dimension. The role of the fractal parameters will be instrumental in establishing the most effective design for the optimum cooling of microelectronic devices. This can help establish the requirement of minimal pumping power for enhancement of heat transfer during cooling. Results obtained in this study show that the proposed models for fractal architectures of microchannels significantly enhanced heat transfer due to augmentation of surface area in the branching networks of varying length-scales.

Keywords: fractals, microelectronics, constructal theory, heat transfer enhancement, pumping power enhancement

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Authors: E. Karimi-Sibaki, A. Kharicha, M. Wu, A. Ludwig

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The standard electroslag remelting (ESR) process can ideally control the solidification of an ingot and produce homogeneous structure with minimum defects. However, the melt rate of electrode is rather low that makes the whole process uneconomical especially to produce small ingot sizes. In contrast, continuous casting is an economical process to produce small ingots such as billets at high casting speed. Unfortunately, deep liquid melt pool forms in the billet ingot of continuous casting that leads to center porosity and segregation. As such, continuous casting is not suitable to produce segregation prone alloys like tool steel or several super alloys. On the other hand, the electro slag rapid remelting (ESRR) process has advantages of both traditional ESR and continuous casting processes to produce billets. In the ESRR process, a T-shaped mold is used including a graphite ring that takes major amount of current through the mold. There are only a few reports available in the literature discussing about this topic. The research on the ESRR process is currently ongoing aiming to improve the design of the T-shaped mold, to decrease overall heat loss in the process, and to obtain a higher temperature at metal meniscus. In the present study, a 3D model is proposed to investigate the electromagnetic, thermal, and flow fields in the whole process as well as solidification of the billet ingot. We performed a fully coupled numerical simulation to explore the influence of the electromagnetically driven flow (MHD) on the thermal field in the slag and ingot. The main goal is to obtain some fundamental understanding of the formation of melt pool of the solidifying billet ingot in the ESRR process.

Keywords: billet ingot, magnetohydrodynamics (mhd), numerical simulation, remelting, solidification, t-shaped mold.

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Authors: K. J. Sannapapamma, H. Malligawad Lokanath, Sakeena Naikwadi

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Eco-friendly textiles are gaining importance among the consumers and textile manufacturers in the healthcare sector due to increased environmental pollution which leads to several health and environmental hazards. Hence, the research was designed to cultivate and develop the organic cotton knit, to prepare and characterize the Vetiver oil microcapsules for textile finishing and to access the wash durability of finished knits. The cotton SAHANA variety grown under organic production systems was processed and spun into 30 single yarn dyed with four natural colorants (Arecanut slurry, Eucalyptus leaves, Pomegranate rind and Indigo) and eco dyed yarn was further used for development of single jersy knitted fabric. Vetiveria zizanioides is an aromatic grass which is being traditionally used in medicine and perfumery. Vetiver essential oil was used for preparation of microcapsules by interfacial polymerization technique subjected to Gas Chromatography Mass Spectrometry (GCMS), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric Analyzer (TGA) and Scanning Electron Microscope (SEM) for characterization of microcapsules. The knitted fabric was finished with vetiver oil microcapsules by exhaust and pad dry cure methods. The finished organic knit was assessed for laundering on antimicrobial efficiency and aroma intensity. GCMS spectral analysis showed that, diethyl phthalate (28%) was the major compound found in vetiver oil followed by isoaromadendrene epoxide (7.72%), beta-vetivenene (6.92%), solavetivone (5.58%), aromadenderene, azulene and khusimol. Bioassay explained that, the vetiver oil and diluted vetiver oil possessed greater zone of inhibition against S. aureus and E. coli than the coconut oil. FTRI spectra of vetiver oil and microcapsules possessed similar peaks viz., C-H, C=C & C꞊O stretching and additionally oil microcapsules possessed the peak of 3331.24 cm^-1 at 91.14 transmittance was attributed to N-H stretches. TGA of oil microcapsules revealed that, there was a minimum weight loss (5.835%) recorded at 467.09°C compared to vetiver oil i.e., -3.026% at the temperature of 396.24°C. The shape of the microcapsules was regular and round, some were spherical in shape and few were rounded by small aggregates. Irrespective of methods of application, organic cotton knits finished with microcapsules by pad dry cure method showed maximum zone of inhibition compared to knits finished by exhaust method against S. aureus and E. coli. The antimicrobial activity of the finished samples was subjected to multiple washing which indicated that knits finished with pad dry cure method showed a zone of inhibition even after 20^th wash and better aroma retention compared to knits finished with the exhaust method of application. Further, the group of respondents rated that the 5^th washed samples had the greater aroma intensity in both the methods than the other samples. Thus, the vetiver microencapsulated organic cotton knits are free from hazardous chemicals and have multi-functional properties that can be suitable for medical and healthcare textiles.

Keywords: exhaust and pad dry cure finishing, interfacial polymerization, organic cotton knits, vetiver oil microcapsules

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Authors: Luo Guidong, Song Hang, Jim Song, Virginia Martin Torrejon

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Due to their excellent properties, polymer packaging foams have become increasingly essential in our current lifestyles. They are cost-effective and lightweight, with excellent mechanical and thermal insulation properties. However, they constitute a major environmental and health concern due to litter generation, ocean pollution, and microplastic contamination of the food chain. In recent years, considerable efforts have been made to develop more sustainable alternatives to conventional polymer packaging foams. As a result, biobased and compostable foams are increasingly becoming commercially available, such as starch-based loose-fill or PLA trays. However, there is still a need for bulk manufacturing of bio-foams planks for packaging applications as a viable alternative to their fossil fuel counterparts (i.e., polystyrene, polyethylene, and polyurethane). Gelatin is a promising biopolymer for packaging applications due to its biodegradability, availability, and biocompatibility, but its mechanical properties are poor compared to conventional plastics. However, as widely reported for other biopolymers, such as starch, the mechanical properties of gelatin-based bioplastics can be enhanced by formulation optimization, such as the incorporation of fibres from different crops, such as bamboo. This research aimed to produce gelatin-bamboo fibre foams by mechanical foaming and to study the effect of fibre content on the foams' properties and structure. As a result, foams with virtually no shrinkage, low density (<40 kg/m³), low thermal conductivity (<0.044 W/m•K), and mechanical properties comparable to conventional plastics were produced. Further work should focus on developing formulations suitable for the packaging of water-sensitive products and processing optimization, especially the reduction of the drying time.

Keywords: biobased and compostable foam, sustainable packaging, natural polymer hydrogel, cold chain packaging

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Authors: Eunsong Lee, Gae Baik Kim, Young Pil Kim

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Bisphenol A (BPA) is one of the endocrine disruptors (EDCs), which have been suspected to be associated with reproductive dysfunction and physiological abnormality in human. Since the BPA has been widely used to make plastics and epoxy resins, the leach of BPA from the lining of plastic products has been of major concern, due to its environmental or human exposure issues. The simple detection of BPA based on the self-assembly of aptamer-mediated gold nanoparticles (AuNPs) has been reported elsewhere, yet the detection sensitivity still remains challenging. Here we demonstrate an improved AuNP-based sensor of BPA by using fluorescence-combined AuNP colorimetry in order to overcome the drawback of traditional AuNP sensors. While the anti-BPA aptamer (full length or truncated ssDNA) triggered the self-assembly of unmodified AuNP (citrate-stabilized AuNP) in the presence of BPA at high salt concentrations, no fluorescence signal was observed by the subsequent addition of SYBR Green, due to a small amount of free anti-BPA aptamer. In contrast, the absence of BPA did not cause the self-assembly of AuNPs (no color change by salt-bridged surface stabilization) and high fluorescence signal by SYBP Green, which was due to a large amount of free anti-BPA aptamer. As a result, the quantitative analysis of BPA was achieved using the combination of absorption of AuNP with fluorescence intensity of SYBR green as a function of BPA concentration, which represented more improved detection sensitivity (as low as 1 ppb) than did in the AuNP colorimetric analysis. This method also enabled to detect high BPA in water-soluble extracts from thermal papers with high specificity against BPS and BPF. We suggest that this approach will be alternative for traditional AuNP colorimetric assays in the field of aptamer-based molecular diagnosis.

Keywords: bisphenol A, colorimetric, fluoroscence, gold-aptamer nanobiosensor

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Authors: Vladimir A. Vinnikov

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The paper proposes a model of an inhomogeneous rock mass with initially random distribution of microcracks on mineral grain boundaries. It describes the behavior of cracks in a medium under the effect of thermal field, the medium heated instantaneously to a predetermined temperature. Crack growth occurs according to the concept of fracture mechanics provided that the stress intensity factor K exceeds the critical value of Kc. The modeling of thermally induced acoustic emission memory effects is based on the assumption that every event of crack nucleation or crack growth caused by heating is accompanied by a single acoustic emission event. Parameters of the thermally induced acoustic emission memory effect produced by cyclic heating and cooling (with the temperature amplitude increasing from cycle to cycle) were calculated for several rock texture types (massive, banded, and disseminated). The study substantiates the adaptation of the proposed model to humidity interference with the thermally induced acoustic emission memory effect. The influence of humidity on the thermally induced acoustic emission memory effect in quasi-homogeneous and banded rocks is estimated. It is shown that such modeling allows the structure and texture of rocks to be taken into account and the influence of interference factors on the distinctness of the thermally induced acoustic emission memory effect to be estimated. The numerical modeling can be used to obtain information about the thermal impacts on rocks in the past and determine the degree of rock disturbance by means of non-destructive testing.

Keywords: degree of rock disturbance, non-destructive testing, thermally induced acoustic emission memory effects, structure and texture of rocks

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Authors: Cecilia Espindola, Juan Carlos Palacios

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Flavonoids are a large group of natural compounds which are found in many fruits and vegetables. A subgroup of these called flavanones display a wide range of biological activities, and they also have an important physiological role in plants. The ionic liquid (ILs) are compounds consisting of an organic cation with an organic or inorganic anion. Due to its unique properties such as high electrical conductivity, wide temperature range of the liquid state, thermal and electrochemical stability, high ionic density and low volatility and flammability, are considered as ecological solvents in organic synthesis, catalysis, electrolytes in accumulators, and electrochemistry, non-volatile plasticizers, and chemical separation. It was synthesized ionic liquid IL 1-butyl-3-methylimidazolium bromide free-solvent and used as reaction medium for flavanones synthesis, under several reaction conditions of temperature, time and production. The obtained compounds were analyzed by melting point, elemental analysis, IR and UV-vis spectroscopy.

Keywords: 1-butyl-3-methylimidazolium bromide, flavonoids, free-solvent, IR spectroscopy

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Authors: A. J. Cobley, L. Krishnan

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The demand for multi-functional lightweight materials in sectors such as automotive, aerospace, electronics is growing, and for this reason fibre-reinforced, epoxy polymer composites are being widely utilized. The fibre reinforcing material is mainly responsible for the strength and stiffness of the composites whilst the main role of the epoxy polymer matrix is to enhance the load distribution applied on the fibres as well as to protect the fibres from the effect of harmful environmental conditions. The superior properties of the fibre-reinforced composites are achieved by the best properties of both of the constituents. Although factors such as the chemical nature of the epoxy and how it is cured will have a strong influence on the properties of the epoxy matrix, the method of mixing and degassing of the resin can also have a significant impact. The production of a fibre-reinforced epoxy polymer composite will usually begin with the mixing of the epoxy pre-polymer with a hardener and accelerator. Mechanical methods of mixing are often employed for this stage but such processes naturally introduce air into the mixture, which, if it becomes entrapped, will lead to voids in the subsequent cured polymer. Therefore, degassing is normally utilised after mixing and this is often achieved by placing the epoxy resin mixture in a vacuum chamber. Although this is reasonably effective, it is another process stage and if a method of mixing could be found that, at the same time, degassed the resin mixture this would lead to shorter production times, more effective degassing and less voids in the final polymer. In this study the effect of four different methods for mixing and degassing of the pre-polymer with hardener and accelerator were investigated. The first two methods were manual stirring and magnetic stirring which were both followed by vacuum degassing. The other two techniques were ultrasonic mixing/degassing using a 40 kHz ultrasonic bath and a 20 kHz ultrasonic probe. The cured cast resin samples were examined under scanning electron microscope (SEM), optical microscope, and Image J analysis software to study morphological changes, void content and void distribution. Three point bending test and differential scanning calorimetry (DSC) were also performed to determine the thermal and mechanical properties of the cured resin. It was found that the use of the 20 kHz ultrasonic probe for mixing/degassing gave the lowest percentage voids of all the mixing methods in the study. In addition, the percentage voids found when employing a 40 kHz ultrasonic bath to mix/degas the epoxy polymer mixture was only slightly higher than when magnetic stirrer mixing followed by vacuum degassing was utilized. The effect of ultrasonic mixing/degassing on the thermal and mechanical properties of the cured resin will also be reported. The results suggest that low frequency ultrasound is an effective means of mixing/degassing a pre-polymer mixture and could enable a significant reduction in production times.

Keywords: degassing, low frequency ultrasound, polymer composites, voids

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Authors: Jure Galović, Peter Hofmann

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Thermochemical energy storage (TCES), as a long-term and lossless energy storage principle, provides a contribution for the reduction of greenhouse emissions of mobile applications, such as passenger vehicles with an internal combustion engine. A prototype of a TCES system, based on reversible sorption reactions of LiBr composite and methanol has been designed at Vienna University of Technology. In this paper, the selection of reactive and inert carrier materials as well as the design of heat exchangers (reactor vessel and evapo-condenser) was reviewed and the cycle stability under real operating conditions was investigated. The performance of the developed system strongly depends on the environmental temperatures, to which the reactor vessel and evapo-condenser are exposed during the phases of thermal conversion. For an integration of the system into mobile applications, the functionality of the designed prototype was proved in numerous conducted cycles whereby no adverse reactions were observed.

Keywords: dynamic applications, LiBr composite, methanol, performance of TCES system, sorption process, thermochemical energy storage

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Authors: Daniel Assefa, Engeda Dessalegn, Chetan Chauhan

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Moringa stenopetala is a socioeconomic valued tree that is widely available and cultivated in the Southern part of Ethiopia. The leaves have been traditionally used as a food source with high nutritional and medicinal values. The present work was carried out to evaluate the effect of thermal treatment on the total phenolic content, antioxidant and alpha-amylase inhibition activities of aqueous leaf extracts during maceration and different decoction time interval (5, 10 and 15 min). The total phenolic content was determined by the Folin-ciocalteu methods whereas antioxidant activities were determined by 2,2-diphenyl-1-picryl-hydrazyl(DPPH) radical scavenging, reducing power and ferrous ion chelating assays and alpha-amylase inhibition activity was determined using 3,5-dinitrosalicylic acid method. Total phenolic content ranged from 34.35 to 39.47 mgGAE/g. Decoction for 10 min extract showed ferrous ion chelating (92.52), DPPH radical scavenging (91.52%), alpha-amylase inhibition (69.06%) and ferric reducing power (0.765), respectively. DPPH, reducing power and alpha-amylase inhibition activities showed positive linear correlation (R2=0.853, R2= 0.857 and R2=0.930), respectively with total phenolic content but ferrous ion chelating activity was found to be weakly correlated (R2=0.481). Based on the present investigation, it could be concluded that major loss of total phenolic content, antioxidant and alpha-amylase inhibition activities of the crude leaf extracts of Moringa stenopetala leaves were observed at decoction time for 15 min. Therefore, to maintain the total phenolic content, antioxidant, and alpha-amylase inhibition activities of leaves, cooking practice should be at the optimum decoction time (5-10 min).

Keywords: alpha-amylase inhibition, antioxidant, Moringa stenopetala, total phenolic content

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Authors: Wiqar Hussain Shah

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The electrical and thermal properties of the doped Tellurium Telluride (Tl10Te6) chalcogenide nano-particles are mainly characterized by a competition between metallic (hole doped concentration) and semi-conducting state. We have studied the effects of Sn doping on the electrical and thermoelectric properties of Tl10-xSnxTe6 (1.00 ≤x≤ 2.00), nano-particles, prepared by solid state reactions in sealed silica tubes and ball milling method. Structurally, all these compounds were found to be phase pure as confirmed by the x-rays diffractometery (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. Additionally crystal structure data were used to model the data and support the findings. The particles size was calculated from the XRD data by Scherrer’s formula. The EDS was used for an elemental analysis of the sample and declares the percentage of elements present in the system. The thermo-power or Seebeck co-efficient (S) was measured for all these compounds which show that S increases with increasing temperature from 295 to 550 K. The Seebeck coefficient is positive for the whole temperature range, showing p-type semiconductor characteristics. The electrical conductivity was investigated by four probe resistivity techniques revealed that the electrical conductivity decreases with increasing temperature, and also simultaneously with increasing Sn concentration. While for Seebeck coefficient the trend is opposite which is increases with increasing temperature. These increasing behavior of Seebeck coefficient leads to high power factor which are increases with increasing temperature and Sn concentration except For Tl8Sn2Te6 because of lowest electrical conductivity but its power factor increases well with increasing temperature.

Keywords: Sn doping in Tellurium Telluride nano-materials, electron holes competition, Seebeck co-efficient, effects of Sn doping on Electrical conductivity, effects on Power factor

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Authors: Margarita S. Tikhonova, Alireza Baniasad, Anton G. Kalmykov, Georgy A. Kalmykov, Ralf Littke

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There is a high complexity in the pore structure of organic-rich rocks caused by the combination of inter-particle porosity from inorganic mineral matter and ultrafine intra-particle porosity from both organic matter and clay minerals. Fluids are retained in that pore space, but there are major uncertainties in how and where the fluids are stored and to what extent they are accessible or trapped in 'closed' pores. A large degree of tortuosity may lead to fractionation of organic matter so that the lighter and flexible compounds would diffuse to the reservoir whereas more complicated compounds may be locked in place. Additionally, parts of hydrocarbons could be bound to solid organic matter –kerogen– and mineral matrix during expulsion and migration. Larger compounds can occupy thin channels so that clogging or oil and gas entrapment will occur. Sequential extraction of applying different solvents is a powerful tool to provide more information about the characteristics of trapped organic matter distribution. The Upper Jurassic – Lower Cretaceous Bazhenov shale is one of the most petroliferous source rock extended in West Siberia, Russia. Concerning the variable mineral composition, pore space distribution and thermal maturation, there are high uncertainties in distribution and composition of organic matter in this formation. In order to address this issue geological and geochemical properties of 30 samples including mineral composition (XRD and XRF), structure and texture (thin-section microscopy), organic matter contents, type and thermal maturity (Rock-Eval) as well as molecular composition (GC-FID and GC-MS) of different extracted materials during sequential extraction were considered. Sequential extraction was performed by a Soxhlet apparatus using different solvents, i.e., n-hexane, chloroform and ethanol-benzene (1:1 v:v) first on core plugs and later on pulverized materials. The results indicate that the studied samples are mainly composed of type II kerogen with TOC contents varied from 5 to 25%. The thermal maturity ranged from immature to late oil window. Whereas clay contents decreased with increasing maturity, the amount of silica increased in the studied samples. According to molecular geochemistry, stored hydrocarbons in open and closed pore space reveal different geochemical fingerprints. The results improve our understanding of hydrocarbon expulsion and migration in the organic-rich Bazhenov shale and therefore better estimation of hydrocarbon potential for this formation.

Keywords: Bazhenov formation, bitumen, molecular geochemistry, sequential extraction

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Authors: Mary-Luz Olivares-Tenorio, Ruud Verkerk, Matthijs Dekker, Martinus A. J. S. van Boekel

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Cape gooseberry, the fruit of the plant Physalis peruviana L. has gained interest in research given its contents of promising health-promoting compounds like contents. The presence of carotenoids, ascorbic acid, minerals, polyphenols, vitamins and antioxidants. This project aims to study thermal stability of β-carotene, ascorbic acid, catechin and epicatechin and antioxidant activity in the matrix of the Cape Gooseberry. Fruits were obtained from a Colombian field in Cundinamarca. Ripeness stage was 4 (According to NTC 4580, corresponding to mature stage) at the moment of the experiment. The fruits have been subjected to temperatures of 40, 60, 80, 100 and 120°C for several times. β-Carotene, ascorbic acid, catechin and epicatechin content were assessed with HPLC and antioxidant activity with the DPPH method. β-Carotene was stable upon 100°C, and showed some degradation at 120°C. The same behavior was observed for epicatechin. Catechin increased during treatment at 40°C, at 60°C it remained stable and it showed degradation at 80°C, 100°C and 120°C that could be described by a second order kinetic model. Ascorbic acid was the most heat-sensitive of the analyzed compounds. It showed degradation at all studied temperatures, and could be described by a first order model. The activation energy for ascorbic acid degradation in cape gooseberry was 46.0 kJ/mol and its degradation rate coefficient at 100 °C was 6.53 x 10-3 s-1. The antioxidant activity declined for all studied temperatures. Results from this study showed that cape gooseberry is an important source of different health-promoting compounds and some of them are stable to heat. That makes this fruit a suitable raw material for processed products such as jam, juices and dehydrated fruit, giving the consumer a good intake of these compounds.

Keywords: goldenberry, health-promoting compounds, phytochemical, processing, heat treatment

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Authors: John Sweeney, Martin Leeming, Raj Thaker, Cristina L. Tuinea-Bobe

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Shrink wrapping is widely used as a method for secondary packaging to assemble individual items, such as cans or other consumer products, into single packages. This method involves conveying the packages into heated tunnels and so has the disadvantages that it is energy-intensive, and, in the case of aerosol products, potentially hazardous. We are developing an automated packaging system that uses stretch wrapping to address both these problems, by using a mechanical rather than a thermal process. In this study, we present a comparative study of shrink wrapping and stretch wrapping materials to assess the relative capability of candidate stretch wrap polymer film in terms of mechanical response. The stretch wrap materials are of oriented polymer and therefore elastically anisotropic. We are developing material constitutive models that include both anisotropy and nonlinearity. These material models are to be incorporated into computer simulations of the automated stretch wrapping system. We present results showing the validity of these models and the feasibility of applying them in the simulations.

Keywords: constitutive model, polymer, mechanical testing, wrapping system

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Authors: H. Niranjan, S. Sivasankaran, Zailan Siri

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This study investigates mixed convection heat transfer about a thin vertical plate in the presence of magnetohydrodynamic (MHD) and heat transfer effects in the porous medium. The fluid is assumed to be steady, laminar, incompressible and in two-dimensional flow. The nonlinear coupled parabolic partial differential equations governing the flow are transformed into the non-similar boundary layer equations, which are then solved numerically using the shooting method. The effects of the conjugate heat transfer parameter, the porous medium parameter, the permeability parameter, the mixed convection parameter, the magnetic parameter, and the thermal radiation on the velocity and temperature profiles as well as on the local skin friction and local heat transfer are presented and analyzed. The validity of the methodology and analysis is checked by comparing the results obtained for some specific cases with those available in the literature. The various parameters on local skin friction, heat and mass transfer rates are presented in tabular form.

Keywords: MHD, porous medium, soret/dufour, stagnation-point

Procedia PDF Downloads 375

Authors: Tsung-Yen Tsai, Naveen Bunekar, Ming Hsuan Chang, Wen-Kuang Wang, Satoshi Onda

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The structure-property relationship and initiator effect on bulk polymerized poly(methyl methacrylate) (PMMA)–oragnomodified layered silicate nanocomposites was investigated. In this study, we used 2, 2'-azobis (4-methoxy-2,4-dimethyl valeronitrile and benzoyl peroxide initiators for bulk polymerization. The bulk polymerized nanocomposites’ morphology was investigated by X-ray diffraction and transmission electron microscopy. The type of initiator strongly influences the physiochemical properties of the polymer nanocomposite. The thermal degradation of PMMA in the presence of nanofiller was studied. 5 wt% weight loss temperature (T5d) increased as compared to pure PMMA. The peak degradation temperature increased for the nanocomposites. Differential scanning calorimetry and dynamic mechanical analysis were performed to investigate the glass transition temperature and the nature of the constrained region as the reinforcement mechanism respectively. Furthermore, the optical properties such as UV-Vis and Total Luminous Transmission of nanocomposites are examined.

Keywords: initiator, bulk polymerization, layered silicates, methyl methacrylate

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Authors: D. V. S. Praneeth, V. R. Sankar Cheela, Brajesh Dubey

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Coal Combustion (CC) residues are the major by-products from thermal power plants. The disposal of ash on to land creates havoc to environment and humans. The leaching of the constituent elements pollutes ground water. Beneficiary use of coal combustion residues in structural components is being investigated as a part of this study. This application reduces stress on the convention materials in the construction industry. The present study involves determination of leaching parameters of the CC residues. Batch and column studies are performed based on Leaching Environmental Assessment Framework (LEAF) protocol. The column studies are conducted to simulate the real time percolation conditions in the field. The structural and environmental studies are performed to determine the usability of CC residues as bricks. The physical, chemical, geo environmental and mechanical properties of the alternate materials are investigated. Scanning electron microscopy (SEM), X-Ray Diffraction analysis (XRD), X-ray fluorescence (XRF) and Energy Dispersive X-ray Spectroscopy tests were conducted to determine the characteristics of CC residue ash and bricks.

Keywords: coal combustion residues, LEAF, leaching, SEM

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Authors: Obsi Terfasa, Bhanupriya Das, Shiao-Shing Chen

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Converting coal fly ash (CFA) waste into ceramic membranes presents a promising alternative to traditional disposal methods, offering potential economic and environmental advantages that warrant further investigation. This research focuses on the creation of ceramic membranes exclusively from CFA using a uniaxial compaction technique. The membranes' properties were examined through various analytical methods: Scanning Electron Microscopy (SEM) revealed a porous and flawless membrane surface, X-Ray Diffraction (XRD) identified mullite and quartz crystalline structures, and Fourier-Transform Infrared Spectroscopy (FTIR) characterized the membrane's functional groups. Thermogravimetric analysis (TGA) determined the ideal sintering temperature to be 800°C. To evaluate its separation capabilities, the synthesized membrane was tested on wastewater from denim jeans production at 0.2 bar pressure. The results were impressive, with 97.42% removal of Chemical Oxygen Demand (COD), 95% color elimination, and a pure water flux of 4.5 Lm⁻²h⁻¹bar⁻¹. These findings suggest that CFA, a byproduct of thermal power plants, can be effectively repurposed to produce ultrafiltration membranes suitable for various industrial purification and separations.

Keywords: wastewater treatment, separator, coal fly ash, ceramic membrane, ultrafiltration

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Authors: Nor Azian Binti Aziz, Muhammad Afiq Bin Tambichik, Zamri Bin Hashim

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The rapid development of the construction industry has contributed to increased construction waste, with concrete waste being among the most abundant. This waste is generated from ready-mix batching plants after the concrete cube testing process is completed and disposed of in landfills, leading to increased solid waste management costs. This study aims to evaluate the engineering characteristics of foamed concrete with waste mixtures construction and agricultural waste to determine the usability of recycled materials in the construction of non-load-bearing walls. This study involves the collection of construction wastes, such as recycled aggregates (RCA) obtained from the remains of finished concrete cubes, which are then tested in the laboratory. Additionally, agricultural waste, such as rice husk ash, is mixed into foamed concrete interlock blocks to enhance their strength. The optimal density of foamed concrete for this study was determined by mixing mortar and foam-backed agents to achieve the minimum targeted compressive strength required for non-load-bearing walls. The tests conducted in this study involved two phases. In Phase 1, elemental analysis using an X-ray fluorescence spectrometer (XRF) was conducted on the materials used in the production of interlock blocks such as sand, recycled aggregate/recycled concrete aggregate (RCA), and husk ash paddy/rice husk ash (RHA), Phase 2 involved physical and thermal tests, such as compressive strength test, heat conductivity test, and fire resistance test, on foamed concrete mixtures. The results showed that foamed concrete can produce lightweight interlock blocks. X-ray fluorescence spectrometry plays a crucial role in the characterization, quality control, and optimization of foamed concrete mixes containing construction and agriculture waste. The unique composition mixer of foamed concrete and the resulting chemical and physical properties, as well as the nature of replacement (either as cement or fine aggregate replacement), the waste contributes differently to the performance of foamed concrete. Interlocking blocks made from foamed concrete can be advantageous due to their reduced weight, which makes them easier to handle and transport compared to traditional concrete blocks. Additionally, foamed concrete typically offers good thermal and acoustic insulation properties, making it suitable for a variety of building projects. Using foamed concrete to produce lightweight interlock blocks could contribute to more efficient and sustainable construction practices. Additionally, RCA derived from concrete cube waste can serve as a substitute for sand in producing lightweight interlock blocks.

Keywords: construction waste, recycled aggregates (RCA), sustainable concrete, structure material

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Authors: Hrachuhi Galstyan, Lucian Sfîcă, Pavel Ichim

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The purpose of this study is to analyze the temporal and spatial variability of thermal conditions in the Republic of Armenia. The paper describes annual fluctuations in air temperature. Research has been focused on case study region of Armenia and surrounding areas, where long–term measurements and observations of weather conditions have been performed within the National Meteorological Service of Armenia and its surrounding areas. The study contains yearly air temperature data recorded between 1961-2012. Mann-Kendal test and the autocorrelation function were applied to detect the change trend of annual mean temperature, as well as other parametric and non-parametric tests searching to find the presence of some breaks in the long term evolution of temperature. The analysis of all records reveals a tendency mostly towards warmer years, with increased temperatures especially in valleys and inner basins. The maximum temperature increase is up to 1,5 °C. Negative results have not been observed in Armenia. The patterns of temperature change have been observed since the 1990’s over much of the Armenian territory. The climate in Armenia was influenced by global change in the last 2 decades, as results from the methods employed within the study.

Keywords: air temperature, long-term variability, trend, climate change

Procedia PDF Downloads 298

Authors: Mara F. Müller, Simon C. Griffith, Tara L. Crewe, Mirjam Kaestli, Sydney J. Collett, Ian J. Radford, Hamish A. Campbell

Abstract:

The intensity and frequency of heat waves have been progressively increasing because of climate change. Passerines that inhabit very hot regions are already close to their physiological thermal limit and are thus considered highly susceptible to increased ambient temperatures. However, the extent by which passerines behaviorally compensate for extreme heat in their natural habitat has rarely been assessed due to monitoring challenges. To address this knowledge gap, coded VHF-nano transmitters were attached to a tropical passerine (Gouldian finch, Chloebia gouldiae). Fine-scale activity and movement were monitored throughout the hottest and driest period of the year using an array of static VHF-receivers. The finches were found to typically show a peak activity for a few hours at sunrise and remained relatively quiescent for the rest of the day. However, on extremely hot days (max temperature >38ºC), finches showed higher activity levels earlier in the morning and presented a second peak in the afternoon. Gouldian finches are physiologically challenged when ambient temperatures exceed 38ºC, suggesting the shift in movement activity reflects a behavioral mitigation strategy to extreme heat. These tropical finches already exist on an energetic knife-edge during this time of the year due to resource scarcity. Hence, the increased energetic expenditure to mitigate thermal stress may be detrimental. The study demonstrates the value of VHF-telemetry technology in monitoring the impact of global change on the biology of small-bodied mobile species.

Keywords: animal tracking, biotelemetry, climate change, extreme heat, movement activity, radiotelemetry, VHF-telemetry

Procedia PDF Downloads 92

Authors: Abdulrahman Alajlan

Abstract:

While the sun serves as a robust energy source, the frigid conditions of outer space present promising prospects for nocturnal power generation due to its continuous accessibility during nighttime hours. This investigation illustrates a proficient methodology facilitating uninterrupted energy capture throughout the day. This method involves the utilization of water-based heat storage systems and radiative thermal emitters implemented across thermometric devices. Remarkably, this approach permits an enhancement of nighttime power generation that exceeds the level of 1 Wm-2, which is unattainable by alternative methodologies. Outdoor experiments conducted at the King Abdulaziz City for Science and Technology (KACST) have demonstrated unparalleled performance, surpassing prior experimental benchmarks by nearly an order of magnitude. Furthermore, the developed device exhibits the capacity to concurrently supply power to multiple light-emitting diodes, thereby showcasing practical applications for nighttime power generation. This research unveils opportunities for the creation of scalable and efficient 24-hour power generation systems based on thermoelectric devices. Central findings from this study encompass the realization of continuous 24-hour power generation from clean and sustainable energy sources. Theoretical analyses indicate the potential for nighttime power generation reaching up to 1 Wm-2, while experimental results have reached nighttime power generation at a density of 0.5 Wm-2. Additionally, the efficiency of multiple light-emitting diodes (LEDs) has been evaluated when powered by the nighttime output of the integrated thermoelectric generator (TEG). Therefore, this methodology exhibits promise for practical applications, particularly in lighting, marking a pivotal advancement in the utilization of renewable energy for both on-grid and off-grid scenarios.

Keywords: nighttime power generation, thermoelectric devices, radiative cooling, thermal management

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Authors: A. Ghadbane, M. N. Bouaziz, S. Hanini, B. Baggoura, M. Abbaci

Abstract:

The spacer grids are used to fix the rods bundle in a nuclear reactor core also act as turbulence-enhancing devices to improve the heat transfer from the hot surfaces of the rods to the surrounding coolant stream. Therefore, the investigation of thermal-hydraulic characteristics inside the rod bundles is important for optima design and safety operation of a nuclear reactor power plant. This contribution presents a feasibility study to use the ribbed spacer grids as mixing devices. The present study evaluates the effects of different ribbed spacer grids configurations on flow pattern and heat transfer in the downstream of the mixing devices in a 2 x 2 rod bundle array. This is done by obtaining velocity and pressure fields, turbulent intensity and the heat transfer coefficient using a three-dimensional CFD analysis. Numerical calculations are performed by employing K-ε turbulent model. The computational results obtained are promising and the comparison with standard spacer grids shows a clear difference which required the experimental approach to validate.

Keywords: PWR fuel assembly, spacer grid, mixing vane, swirl flow, turbulent heat transfer, CFD

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Authors: B. SahaRoy, T. Medhi, S. C. Saha

Abstract:

To understand the friction stir welding process, it is very important to know the nature of the material flow in and around the tool. The process is a combination of both thermal as well as mechanical work i.e it is a coupled thermo-mechanical process. Numerical simulations are very much essential in order to obtain a complete knowledge of the process as well as the physics underlying it. In the present work a model based approach is adopted in order to study material flow. A thermo-mechanical based CFD model is developed using a Finite Element package, Comsol Multiphysics. The fluid flow analysis is done. The model simultaneously predicts shear strain fields, shear strain rates and shear stress over the entire workpiece for the given conditions. The flow fields generated by the streamline plot give an idea of the material flow. The variation of dynamic viscosity, velocity field and shear strain fields with various welding parameters is studied. Finally the result obtained from the above mentioned conditions is discussed elaborately and concluded.

Keywords: AA6061-T6, CFD modelling, friction stir welding, material flow

Procedia PDF Downloads 521