Search results for: thermal stability

Authors: Rahmat Ali, Inamullah Khan, Amjad Naseer, Abid A. Shah

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Hydronic Heating and Cooling systems in concrete slab based buildings are increasingly becoming a popular substitute to conventional heating and cooling systems. In exploring the materials, techniques employed, and their relative performance measures, a fair bit of uncertainty exists. This research has identified the simplest method of determining the thermal field of a single hydronic pipe when acting as a part of a concrete slab, based on which the spacing and positioning of pipes for a best thermal performance and surface temperature control are determined. The pipe material chosen is the commonly used PEX pipe, which has an all-around performance and thermal characteristics with a thermal conductivity of 0.5W/mK. Concrete Test samples were constructed and their thermal fields tested under varying input conditions. Temperature sensing devices were embedded into the wet concrete at fixed distances from the pipe and other touch sensing temperature devices were employed for determining the extent of the thermal field and validation studies. In the first stage, it was found that the temperature along a specific distance was the same and that heat dissipation occurred in well-defined layers. The temperature obtained in concrete was then related to the different control parameters including water supply temperature. From the results, the temperature of water required for a specific temperature rise in concrete is determined. The thermally effective area is also determined which is then used to calculate the pipe spacing and positioning for the desired level of thermal comfort.

Keywords: thermally activated building systems, concrete slab temperature, thermal field, energy efficiency, thermal comfort, pipe spacing

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Authors: Nahia H. Sassine, Frédéric-Victor Donzé, Arnaud Bruch, Barthélemy Harthong

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Thermal Energy Storage (TES) systems are central elements of various types of power plants operated using renewable energy sources. Packed bed TES can be considered as a cost–effective solution in concentrated solar power plants (CSP). Such a device is made up of a tank filled with a granular bed through which heat-transfer fluid circulates. However, in such devices, the tank might be subjected to catastrophic failure induced by a mechanical phenomenon known as thermal ratcheting. Thermal stresses are accumulated during cycles of loading and unloading until the failure happens. For instance, when rocks are used as storage material, the tank wall expands more than the solid medium during charge process, a gap is created between the rocks and tank walls and the filler material settles down to fill it. During discharge, the tank contracts against the bed, resulting in thermal stresses that may exceed the wall tank yield stress and generate plastic deformation. This phenomenon is repeated over the cycles and the tank will be slowly ratcheted outward until it fails. This paper aims at studying the evolution of tank wall stresses over granular bed thermal cycles, taking into account both thermal and mechanical loads, with a numerical model based on the discrete element method (DEM). Simulations were performed to study two different thermal configurations: (i) the tank is heated homogeneously along its height or (ii) with a vertical gradient of temperature. Then, the resulting loading stresses applied on the tank are compared as well the response of the internal granular material. Besides the study of the influence of different thermal configurations on the storage tank response, other parameters are varied, such as the internal angle of friction of the granular material, the dispersion of particles diameters as well as the tank’s dimensions. Then, their influences on the kinematics of the granular bed submitted to thermal cycles are highlighted.

Keywords: discrete element method (DEM), thermal cycles, thermal energy storage, thermocline

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Authors: Nagmani Lnu

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Test automation is a vital requirement of any organization to release products faster to their customers. In most cases, an organization has an approach to developing automation but struggles to maintain it. It results in an increased number of Flaky Tests, reducing return on investments and stakeholders’ confidence. Challenges grow in multiple folds when automation is for UI behaviors. This paper describes the approaches taken to identify the root cause of automation instability in an extensive payments application and the best practices to address that using processes, tools, and technologies, resulting in a 75% reduction of effort.

Keywords: automation stability, test stability, Flaky Test, test quality, test automation quality

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Authors: Jens Friedrich, Matthias A. Gebele, Armin Lechler, Alexander Verl

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Chatter vibrations and process instabilities are the most important factors limiting the productivity of the milling process. Chatter can leads to damage of the tool, the part or the machine tool. Therefore, the estimation and prediction of the process stability is very important. The process stability depends on the spindle speed, the depth of cut and the width of cut. In milling, the process conditions are defined in the NC-program. While the spindle speed is directly coded in the NC-program, the depth and width of cut are unknown. This paper presents a new simulation based approach for the prediction of the depth and width of cut of a milling process. The prediction is based on a material removal simulation with an analytically represented tool shape and a multi-dexel approach for the work piece. The new calculation method allows the direct estimation of the depth and width of cut, which are the influencing parameters of the process stability, instead of the removed volume as existing approaches do. The knowledge can be used to predict the stability of new, unknown parts. Moreover with an additional vibration sensor, the stability lobe diagram of a milling process can be estimated and improved based on the estimated depth and width of cut.

Keywords: dexel, process stability, material removal, milling

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Authors: K. Chethana, A. S. Guru Prasad, H. N. Vikranth, H. Varun, S. N. Omkar, S. Asokan

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This paper describes a novel application of Fiber Braggs Grating (FBG) sensors on an unstable platform to assess human postural stability and balance. The FBG sensor based Stability Analyzing Device (FBGSAD) developed demonstrates the applicability of FBG sensors in the measurement of plantar strain to assess the postural stability of subjects on unstable platforms during different stances in eyes open and eyes closed conditions on a rocker board. Comparing the Centre of Gravity (CG) variations measured on the lumbar vertebra of subjects using a commercial accelerometer along with FBGSAD validates the study. The results obtained depict qualitative similarities between the data recorded by both FBGSAD and accelerometer, illustrating the reliability and consistency of FBG sensors in biomechanical applications for both young and geriatric population. The developed FBGSAD simultaneously measures plantar strain distribution and postural stability and can serve as a tool/yardstick to mitigate space motion sickness, identify individuals who are susceptible to falls and to qualify subjects for balance and stability, which are important factors in the selection of certain unique professionals such as aircraft pilots, astronauts, cosmonauts etc.

Keywords: biomechanics, fiber bragg gratings, plantar strain measurement, postural stability analysis

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Authors: S. Cheragh Dar, M. Saljooghi, A. Babrgir

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In the last couple of decades researchers' attitudes were focused on developing and enhancing heat transfer processes by using new components or cellular solids that divide into stochastic structures and periodic structures. Open-cell metal foams are part of stochastic structures families that they can be considered as an avant-garde technology and they have unique properties, this porous media can have tremendous achievements in thermal processes. This paper argues and surveys postulating possible in industrial thermal issues which include: compact electronic cooling, heat exchanger, aerospace, fines, turbo machinery, automobiles, crygen tanks, biomechanics, high temperature filters and etc. Recently, by surveying exponential rate of publications in thermal open-cell metal foams, all can be demonstrated in a holistic view which can lead researchers to a new level of understanding in different industrial thermal sections.

Keywords: heat transfer, industrial thermal, cellular solids, open cell metal foam

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Authors: Shahram Naghizadeh Raeisi, Ali Alghooneh, Seyed Jalal Razavi Zahedkolaei

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Herein, a shelf stable (no refrigeration required) UHT processed, aseptically packaged whey protein drink was formulated by using a new strategy in microparticulate process. Applying thermal and two-dimensional mechanical treatments simultaneously, a modified protein (MWPC-80) was produced. Then the physical, thermal and thermodynamic properties of MWPC-80 were assessed using particle size analysis, dynamic temperature sweep (DTS), and differential scanning calorimetric (DSC) tests. Finally, using MWPC-80, a new RTD beverage was formulated, and shelf stability was assessed for three months at ambient temperature (25 °C). Non-isothermal dynamic temperature sweep was performed, and the results were analyzed by a combination of classic rate equation, Arrhenius equation, and time-temperature relationship. Generally, results showed that temperature dependency of the modified sample was significantly (Pvalue<0.05) less than the control one contained WPC-80. The changes in elastic modulus of the MWPC did not show any critical point at all the processed stages, whereas, the control sample showed two critical points during heating (82.5 °C) and cooling (71.10 °C) stages. Thermal properties of samples (WPC-80 & MWPC-80) were assessed using DSC with 4 °C /min heating speed at 20-90 °C heating range. Results did not show any thermal peak in MWPC DSC curve, which suggested high thermal resistance. On the other hands, WPC-80 sample showed a significant thermal peak with thermodynamic properties of ∆G:942.52 Kj/mol ∆H:857.04 Kj/mole and ∆S:-1.22Kj/mole°K. Dynamic light scattering was performed and results showed 0.7 µm and 15 nm average particle size for MWPC-80 and WPC-80 samples, respectively. Moreover, particle size distribution of MWPC-80 and WPC-80 were Gaussian-Lutresian and normal, respectively. After verification of microparticulation process by DTS, PSD and DSC analyses, a 10% why protein beverage (10% w/w/ MWPC-80, 0.6% w/w vanilla flavoring agent, 0.1% masking flavor, 0.05% stevia natural sweetener and 0.25% citrate buffer) was formulated and UHT treatment was performed at 137 °C and 4 s. Shelf life study did not show any jellification or precipitation of MWPC-80 contained beverage during three months storage at ambient temperature, whereas, WPC-80 contained beverage showed significant precipitation and jellification after thermal processing, even at 3% w/w concentration. Consumer knowledge on nutritional advantages of whey protein increased the request for using this protein in different food systems especially RTD beverages. These results could make a huge difference in this industry.

Keywords: high protein whey beverage, micropartiqulation, two-dimentional mechanical treatments, thermodynamic properties

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Authors: H. Zou, B. Wang

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Thermal distortion of the machine tool plays a critical role in its machining accuracy. This study investigates the thermal performance of a high-precision machine frame with future-oriented mineral casting components. A thermo-mechanical finite element model (FEM) was established to evaluate the thermal behavior of the frame under environmental thermal fluctuations. The validity of the presented FEM model was confirmed experimentally by a series of laser interferometer tests. Good agreement between numerical and experimental results demonstrates that the proposed model can accurately predict the thermal deformation of the frame with thermo-mechanical coupling effect. The results also show that keeping the workshop in thermally stable conditions is crucial for improving the machine accuracy of the system with large scale components. The goal of this paper is to investigate the feasibility of innovative mineral casting material applied in high-precision drilling machine and to provide a strategy for machine tool industry seeking a perfect substitute for classic frame materials such as cast iron and granite.

Keywords: thermo-mechanical model, finite element method, laser interferometer, mineral casting frame

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Authors: M. Riaz, Inamur Rehman, Abhishek Sharma

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The present work is the development of an experimental method for determining the thermal diffusivity variations with temperature of selected regular shaped solid fruits and vegetables subjected to forced convection cooling. Experimental investigations were carried on the sample chosen (potato and brinjal), which is approximately of spherical geometry. The variation of temperature within the food product is measured at several locations from centre to skin, under forced convection environment using a deep freezer, maintained at -10°C.This method uses one dimensional Fourier equation applied to regular shapes. For this, the experimental temperature data obtained from cylindrical and spherical shaped products during pre-cooling was utilised. Such temperature and thermal diffusivity profiles can be readily used with other information such as degradation rate, etc. to evaluate thermal treatments based on cold air cooling methods for storage of perishable food products.

Keywords: thermal diffusivity, skin temperature, precooling, forced convection, regular shaped

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Authors: Nancy Sakr, Mohamed Abou-Zeid

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World energy consumption has increased rapidly in the past few years. Due to population growth, total energy consumption is increasing; a large amount of energy is wasted on the cooling and heating processes in buildings. However, using thermal heating management can minimize costs, heat consumption and create a management system for the heat insulation for buildings. This concept is being implemented through different approaches. Based on analysis and research, there is evidence in the energy consumption before and after testing and applying construction approaches for thermal heating management in building units. This investigation addresses the evaluation of the influence of external coatings on energy consumption. Coatings are considered one of the smart effective available approaches for energy efficiency. Unfortunately, this approach is not widely applied in the construction industry. It needs more data to prove effectiveness and credibility between people to use it as a smart thermal insulation approach. Two precedents have been analyzed in order to monitor buildings’ heat exposure, and how the buildings will be affected by thermal insulation materials. Data sheets from chemical companies which produce similar coatings are compared with the usual products and the protective thermal products.

Keywords: energy consumption, building envelope, thermal insulation, protective coatings

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Authors: M. Obaid, Nasser A. M. Barakat, Fadali O.A

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Low stability in oil media and the hydrophobicity problems of the ploysulfone electrospun membranes could be overcome in the present study. Synthesis of super-hydrophilic and highly stable in oil polysulfone electrospun nanofiber membrane was achieved by electrospinning of polysulfone solution containing NaOH salt followed by activation of the dried electrospun membrane by deposition of polyamide layer on the surface using m-phenylenediamine and 1,3,5-benzenetricarbonyl chloride. The introduced membrane has super-hydrophilicity characteristic (contact angle=3o), excellent stability in oil media and distinct performance in oil-water separation process.

Keywords: electrospinning, oil-degradability, membrane, nanofibers

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Authors: Dalia Elsawy Abulyazied, Samia Mohamad Mokhtar, Ahmed Magdy Motawie

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This article studies the effects of nano-bentonite on the structure and properties of polymer blends nanocomposites, based on polyvinyl chloride (PVC) and styrene co-maleic anhydride (SMA) blend. Modification of Egyptian bentonite (EB) is carried out using organo-modifier namely; octadecylamine (ODA). Octadecylamine bentonite (ODA-B) is characterized using FTIR, XRD and TEM. Nanocomposites of PVC/SMA/ODA-B are prepared by solution intercalation polymerization from 0.50 up to 5 phr. The nanocomposites are characterized by XRD and TEM. Thermal behavior of the nanocomposites is studied. The effect of different content of ODA-B on the nano-mechanical properties is investigated by a nano-indentation test method. Also the swelling and electrical properties of the nanocomposites are measured. The morphology of the nanocomposites shows that ODA-B achieved good dispersion in the PVC/SMA matrix. The thermal stability of the nanocomposites is enhanced due to the presence of the ODA-B. Incorporation of 0.5, 1, 3 and 5 phr. ODA-B into the PVC/SMA blends results in an improvement in nano-hardness of 16%, 76%, 92%, and 68% respectively. The elastic modulus increased by 37% from 4.59 GPa for unreinforced PVC/SMA blend to 6.30 GPa for 3 phr. The cross-link density and the electrical conductivity of the nanocomposites are increased with increasing the content of ODA-B.

Keywords: PVC, SMA, nanocomposites, nano-bentonite, nanoindentation, crosslink density

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Authors: Rishindra M. Sarviya, Ashish Agrawal

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Solar energy is available abundantly in the world, but it is not continuous and its intensity also varies with time. Due to above reason the acceptability and reliability of solar based thermal system is lower than conventional systems. A properly designed heat storage system increases the reliability of solar thermal systems by bridging the gap between the energy demand and availability. In the present work, two dimensional numerical simulation of the melting of heat storage material is presented in the horizontal annulus of double pipe latent heat storage system. Longitudinal fins were used as a thermal conductivity enhancement. Paraffin wax was used as a heat-storage or phase change material (PCM). Constant wall temperature is applied to heat transfer tube. Presented two-dimensional numerical analysis shows the movement of melting front in the finned cylindrical annulus for analyzing the thermal behavior of the system during melting.

Keywords: latent heat, numerical study, phase change material, solar energy

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Authors: Mahvish Anwaar

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Research Question: In this paper, we explore the causal relationship between banking competition, banking stability, and economic growth. Research Findings: The unbalanced panel data starting from 2000 to 2018 is collected to analyze the causality among banking competition, banking stability, and economic growth. The main focus of the study is to check the direction of causality among selected variables. The results of the study support the demand following, supply leading, feedback, and neutrality hypothesis conditional to different measures of banking competition, banking stability, and economic growth. Theoretical Implication: Jayakumar, Pradhan, Dash, Maradana, and Gaurav (2018) proposed a theoretical model of the causal relationship between banking competition, banking stability, and economic growth by using different indicators. So, we empirically test the proposed indicators in our study. This study makes a contribution to the literature by showing the defined relationship between developing and developed countries. Policy Implications: The study covers various policy implications regarding investors to analyze how to properly manage their finances, and government agencies will take help from the present study to find the best and most suitable policies by examining how the economy can grow concerning its finances.

Keywords: competition, stability, economic growth, vector auto-regression, granger causality

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Authors: Abdelhafid Zenati, Mohamed Tadjine

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The mathematical formulation of biomedical problems is an important phase to understand and predict the dynamic of the controlled population. In this paper we perform a stability analysis of a coupled model for healthy and cancerous cells dynamics in Acute Myeloid Leukemia, this represents our first aim. Second, we illustrate the effect of the interconnection between healthy and cancer cells. The PDE-based model is transformed to a nonlinear distributed state space model (delay system). For an equilibrium point of interest, necessary and sufficient conditions of global asymptotic stability are given. Thus, we came up to give necessary and sufficient conditions of global asymptotic stability of the origin and the healthy situation and control of the dynamics of normal hematopoietic stem cells and cancerous during myelode Acute leukemia. Simulation studies are given to illustrate the developed results.

Keywords: distributed delay, global stability, modelling, nonlinear models, PDE, state space

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Authors: Maged Assem Soliman Mossallam

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One of the main prospectives on the demand of space exploration is to reduce the costs and efforts for satellite design. Concerning this issue satellite down scaling attracts space scientists and engineers. Picosatellite is the smallest category of satellites. The overall mass is less than 1 kg and dimensions are 10x10x3 cm3. Thermal control target is to keep the Pico-satellite board temperature within the permissible limits of temperature. Thermal design is completely passive which relies mainly on the enhancement of the thermo-optical properties of aluminum using anodization. Transient analysis is given for two different orbits, ISS orbit and 600 km altitude orbit. Results show that board temperature lies within 3 oC to 22 oC using black anodization which is a permissible limit for the satellite internal electronic board.

Keywords: satellite thermal control, small satellites, thermooptical properties , transient orbit analysis

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Authors: Prashant Sharma, Jyotsna Dutta Majumdar

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The present study concerns development of a composite thermal barrier coating consisting of a mixture of La2O3 and YSZ (with 8 wt.%, 32 wt.% and 50 wt.% 50% La2O3) by plasma spray deposition technique on a CoNiCrAlY based bond coat deposited on Inconel 718 substrate by high velocity oxy-fuel deposition (HVOF) technique. The addition of La2O3 in YSZ causes the formation of pyrochlore (La2Zr2O7) phase in the inter splats boundary along with the presence of LaYO3 phase. The coefficient of thermal expansion is significantly reduced from due to the evolution of different phases and structural defects in the sprayed coating. The activation energy for TGO growth under isothermal and cyclic oxidation was increased in the composite coating as compared to YSZ coating.

Keywords: plasma spraying, oxidation resistance, thermal barrier coating, microstructure, X-ray method

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Authors: Jian Zheng

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Three-dimensional (3D) network structure has been recognized as an effective approach to enhance the mechanical and thermal conductive properties of polymeric composites. However, it has not been applied in energetic materials. In this work, a fluoropolymer based composite with vertically oriented and interconnected 3D graphite network was fabricated for polymer bonded explosives (PBXs). Here, the graphite and graphene oxide platelets were mixed, and self-assembled via rapid freezing and using crystallized ice as the template. The 3D structure was finally obtained by freezing-dry and infiltrating with the polymer. With the increasing of filler fraction and cooling rate, the thermal conductivity of the polymer composite was significantly improved to 2.15 W m⁻¹ K⁻¹ by 1094% than that of pure polymer. Moreover, the mechanical properties, such as tensile strength and elastic modulus, were enhanced by 82% and 310%, respectively, when the highly ordered structure was embedded in the polymer. We attribute the increased thermal and mechanical properties to this 3D network, which is beneficial to the effective heat conduction and force transfer. This study supports a desirable way to fabricate the strong and thermal conductive fluoropolymer composites used for the high-performance polymer bonded explosives (PBXs).

Keywords: mechanical properties, oriented network, graphite polymer composite, thermal conductivity

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Authors: Anna Bykalyuk, Frédéric Kuznik, Kévyn Johannes

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In this paper, the influence of a vertical plate’s thermal capacity is numerically investigated in order to evaluate the evolution of the thermal boundary layer structure, as well as the convective heat transfer coefficient and the velocity and temperature profiles. Whereas the heat flux of the heated vertical plate is evaluated under time depending boundary conditions. The main important feature of this problem is the unsteadiness of the physical phenomena. A 2D CFD model is developed with the Ansys Fluent 14.0 environment and is validated using unsteady data obtained for plasterboard studied under a dynamic temperature evolution. All the phenomena produced in the vicinity of the thermal conductive vertical plate (plasterboard) are analyzed and discussed. This work is the first stage of a holistic research on transient free convection that aims, in the future, to study the natural convection in the vicinity of a vertical plate containing Phase Change Materials (PCM).

Keywords: CFD modeling, natural convection, thermal conductive plate, time-depending boundary conditions

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Authors: Ishaq Ahmad, Zhaomin Li, Liu Chengwen, Song Yan Li, Zihan Gu, Li Shaopeng

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In order to manage gas mobility in the reservoir, only a small amount of surfactant or polymer is needed because nanoparticles have the potential to improve foam stability. The aim is to enhance foam formation and stability, so it was decided to investigate the foam stability and foam ability of black rice husk ash. Several characterization techniques were used to investigate the properties of black rice husk ash. The best-performing anionic foaming surfactants were combined with black rice husk ash at different concentrations (ppm). Sodium dodecyl benzene sulphonate was used as the anionic surfactant. This study demonstrates the value of black rice husk ash (BRHA), which has a high silica concentration, for foam stability and ability. For the test, black rice husk ash and raw ash were used with SDS (Sodium Dodecyl Sulfate) and SDBS (Sodium dodecyl benzenesulfonate) surfactants under different parameters. Different concentration percentages were utilized to create the foam, and the hydrophobic test and shaking method were applied. The foam scanner was used to observe the behavior of the black rice husk ash foam. The high silica content of black rice husk ash has the potential to improve foam stability, which is favorable and could possibly improve oil recovery.

Keywords: black rice husk ash nanoparticle, surfactant, foam life, foam scanning

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Authors: Ismaila H. Zarma, Mahmoud Ahmed, Shinichi Ookawara, Hamdi Abo-Ali

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Phase change materials (PCM) are an ideal thermal storage medium. They are characterized by a high latent heat, which allows them to store large amounts of energy when the material transitions into different physical states. Concentrated photovoltaic (CPV) systems are widely recognized as the most efficient form of Photovoltaic (PV) for thermal energy which can be stored in Phase Change Materials (PCM). However, PCMs often have a low thermal conductivity which leads to a slow transient response. This makes it difficult to quickly store and access the energy stored within the PCM based systems, so there is need to improve transient responses and increase the thermal conductivity. The present study aims to investigate and analyze the melting and solidification process of phase change materials (PCMs) enhanced by nanoparticle contained in a container. Heat flux from concentrated photovoltaic is applied in an attempt to analyze the thermal performance and the impact of nanoparticles. The work will be realized by using a two dimensional model which take into account the phase change phenomena based on the principle of enthalpy method. Numerical simulations have been performed to investigate heat and flow characteristics by using governing equations, to ascertain the impacts of the nanoparticle loading. The Rayleigh number, sub-cooling as well as the unsteady evolution of the melting front and the velocity and temperature fields were also observed. The predicted results exhibited a good agreement, showing thermal enhancement due to present of nanoparticle which leads to decreasing the melting time.

Keywords: thermal energy storage, phase-change material, nanoparticle, concentrated photovoltaic

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Authors: C. C. Kruger, P. Van Tonder

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Concrete deteriorates over time and the deterioration can be escalated due to multiple factors. When deteriorations are beneath the concrete’s surface, they could be unknown, even more so when they are located at high elevations. Establishing the severity of such defects could prove difficult and therefore the need to find efficient, safe and economical methods to find these defects becomes ever more important. Current methods using thermography to find defects require equipment such as scaffolding to reach these higher elevations. This could become time- consuming and costly. The risks involved with personnel scaffold or abseil to such heights are high. Accordingly, by combining the technologies of a thermal camera and a Remotely Piloted Aerial System it could be used to find better diagnostic methods. The data could then be constructed into a 3D thermal model to easy representation of the results

Keywords: concrete, infrared thermography, 3D thermal models, diagnostic

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Authors: Hernandez Pardo Diego F., Guiza Arguello Viviana R., Coy Echeverria Ana, Viejo Abrante Fernando

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The biological hydroxyapatite obtained from bovine bone arouses great interest in its application as a material for bone regeneration due to its better bioactive behavior in comparison with synthetic hydroxyapatite. For this reason, the objective of the present investigation was to determine the effect of chemical and thermal treatments in obtaining biological bovine hydroxyapatite of high purity and crystallinity. Two different chemical reagents were evaluated (NaOH and HCl) with the aim to remove the organic matrix of the bovine cortical bone. On the other hand, for analyzing the effect of thermal treatment temperature was ranged between 500 and 1000°C for a holding time of 4 hours. To accomplish the above, the materials before and after the chemical and thermal treatments were characterized by elemental compositional analysis (CHN), infrared spectroscopy by Fourier transform (FTIR), RAMAN spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and energy dispersion X-ray spectroscopy (EDS). The results allowed to establish that NaOH is more effective in the removal of the organic matrix of the bone when compared to HCl, whereas a thermal treatment at 700ºC for 4 hours was enough to obtain biological hydroxyapatite of high purity and crystallinity.

Keywords: bovine bone, hydroxyapatite, biomaterials, thermal treatment

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Authors: Tianfang Zhang, Luxi He, Zhengbin He, Songlin Yi

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Moso bamboo is a common non-wood forest resource in Asia that is widely used in construction, furniture, and other fields. Influenced by the heterogeneous structure and various hygroscopic groups of bamboo, the deformation occurs as moisture absorption and desorption when the environment temperature and humidity conditions change. Thermal modification is a well-established commercial technology for improving the dimensional stability of bamboo. However, the higher energy consumption and carbon emissions limit its further development. Previous studies have indicated that inorganic salt-assisted thermal modification could lead to significant reductions in moisture absorption and energy consumption. Represented by metal chlorides, it could show Lewis acid properties when dissolved in water, generating metal ion ligand complexes. In addition, ultrasonic treatment, as an efficient and environmentally friendly physical treatment method, improved the accessibility of pretreatment chemical impregnation agents and intensified mass and heat transfer during reactions. To save energy and reduce deformation, this study elucidates the influence of zinc chloride-ultrasonic treatment on the physicochemical properties of heat-treated bamboo, and the details of the bamboo deformation mechanism with Lewis acid are explained. Three sets of parameters (inorganic salt concentration, ultrasonic frequency and heat treatment temperature) were designed, and an optimized process was proposed to clarify this scientific question, that is: 5% (w/w) zinc chloride solution, 40 kHz ultrasonic waves and heat treatment at 160 °C. The samples were characterized by different means to analyze changes in their macroscopic features, pore structure, chemical structure and chemical composition. The results suggested that the maximum weight loss rate was reduced by at least 19.75%. The maximum thermal degradation peak of hemicellulose was significantly shifted forward. The hygroscopicity was reduced by 10.15%, the relative crystallinity was increased by 4.4%, the surface contact angle was increased by 25.2%, and the color change was increased by 23.60 in the optimal condition. From the electron microscope observation, the treated surface became rougher, and cracks appeared in some weaker areas, accelerating starch loss and removing granular attachments around the pits. By ion diffusion, zinc ions diffused into hemicellulose and a partial amorphous region of cellulose. Parts of the cell wall structure were subjected to swelling and degradation, leading to the broken state of parenchyma cells. From the Raman spectrum, compared to conventional thermal modifications, hemicellulose thermal degradation and lignin migration is promoted by Lewis acid under dilute acid-thermal condition. As shown in this work, the combined Lewis acid and ultrasonic pretreatment as an environmentally friendly, safe, and efficient physic-chemical combined pretreatment method improved the dimensional stability of Moso bamboo and lowered the thermal degradation conditions. This method has great potential for development in the field of bamboo heat treatment, and it might provide some guidance for making dark bamboo flooring.

Keywords: Moso bamboo, Lewis acid, ultrasound, heat treatment

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Authors: Yichao Liang, Biye Chen, Xiang Li, Steven R. Dimler

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This study investigated the effects of adding calcium and magnesium chloride on heat and storage stability of milk protein concentrate-soy protein isolate (8:2 respectively) mixtures containing 10% w/w total protein subjected to the in-container sterilization (115 °C x 15 min). The particle size does not change when emulsions are heated at pH between 6.7 and 7.3 irrespective of the mixed protein ratio. Increasing concentration of divalent cation salts resulted in an increase in protein particle size, dry sediment formation and sediment height and a decrease in pH, heat stability and hydration in milk protein concentrate-soy protein isolate mixtures solutions on sterilization at 115°C. Fortification of divalent cation salts in milk protein concentrate-soy protein isolate mixture solutions resulted in an accelerated protein sedimentation and two unique sediment regions during accelerated storage stability testing. Moreover, the heat stability decreased upon sterilization at 115°C, with addition of MgCl₂ causing a greater increase in sedimentation velocity and compressibility than CaCl₂. Increasing pH value of protein milk concentrate-soy protein isolate mixtures solutions from 6.7 to 7.2 resulted in an increase in viscosity following the heat treatment. The study demonstrated that the type and concentration of divalent cation salts used strongly impact heat and storage stability of milk protein concentrate-soy protein isolate mixture nutritional beverages.

Keywords: divalent cation salts, heat stability, milk protein concentrate, soy protein isolate, storage stability

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Authors: Yacine Babou, Nitesh Ranjan, Branimir Radisavljevic , Martin Seeger, Daniel Over, Torsten Votteler, Bernardo Galletti, Paulo Cristini

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In the frame of replacement of Sulfur hexafluoride (SF6) gas as insulating and switching medium, diverse alternative gases, offering acceptable Global Warming Potential and fulfilling requirements in terms of heat dissipation, insulation and arc quenching performances are currently investigated for High Voltage Circuit Breaker applications. Among the potential gases, CO₂ seems a promising candidate for replacing SF6, because on one hand it is environmentally friendly, harmless, non-toxic, non-corrosive, non-flammable and on the other hand previous studies have demonstrated its fair interruption capabilities. The present study aims at investigating the performance of CO₂ for the thermal interruption in high voltage self-blast circuit breakers. In particular, the correlation between thermal interruption performance and arc voltage is considered and the effect of the arc-network interaction on the performance is rigorously analyzed. For the considered designs, the thermal interruption was evaluated by varying the slope at current zero (i.e., di/dt) for which the breaker could interrupt. Besides, the characteristics of the post-arc current are examined in detail for various rated voltages and currents. The outcome of these experimental investigations will be reported and analyzed.

Keywords: current zero measurement, high voltage circuit breaker, thermal arc discharge, thermal interruption

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Authors: Akeel Noori Almulla Hwaish

Abstract:

Architectural design is influenced by the actual thermal behaviour of building components, and this in turn depends not only on their steady and periodic thermal characteristics, but also on exposure effects, orientation, surface colour, and climatic fluctuations at the given location. Design data and environmental parameters should be produced in an accurate way for specified locations, so that architects and engineers can confidently apply them in their design calculations that enable precise evaluation of the influence of various parameters relating to each component of the envelope, which indicates overall thermal performance of building. The present paper will be carried out with an objective of thermal behaviour assessment and characteristics of the opaque and transparent parts of one of the very unique components used as a symbolic distinguished element of building envelope, its thermal behaviour under the impact of solar temperatures, and its role in heat exchange related to a specific U-value of specified construction materials alternatives. The research method will consider the specified Hot-Dry weather and new mosque in Baghdad, Iraq as a case study. Also, data will be presented in light of the criteria of indoor thermal comfort in terms of design parameters and thermal assessment for a“model dome”. Design alternatives and considerations of energy conservation, will be discussed as well using comparative computer simulations. Findings will be incorporated to outline the conclusions clarifying the important role of the dome in heat exchange of the whole building envelope for approaching an indoor thermal comfort level and further research in the future.

Keywords: building envelope, sustainable design, dome impact, hot-climates, heat exchange

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Authors: Virgo Sulakatko

Abstract:

The reduction of energy consumption of the built environment has been one of the topics tackled by European Commission during the last decade. Increased energy efficiency requirements have increased the renovation rate of apartment buildings covered with External Thermal Insulation Composite System (ETICS). Due to fast and optimized application process, a large extent of quality assurance is depending on the specific activities of artisans and are often not controlled. The on-site degradation factors (DF) have the technical influence to the façade and cause future costs to the owner. Besides the thermal conductivity, the building envelope needs to ensure the mechanical resistance and stability, fire-, noise-, corrosion and weather protection, and long-term durability. As the shortcomings of the construction phase become problematic after some years, the common value of the renovation is reduced. Previous work on the subject has identified and rated the relevance of DF to the technical requirements and developed a method to reveal the economic value of repair works. The future costs can be traded off to increased the quality assurance during the construction process. The proposed framework is describing the joint simulation of the technical importance and economic value of the on-site DFs of ETICS. The model is providing new knowledge to improve the resource allocation during the construction process by enabling to identify and diminish the most relevant degradation factors and increase economic value to the owner.

Keywords: ETICS, construction technology, construction management, life cycle costing

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Authors: Mahdi Aghaei, Saeid Jamshidi, Mastaneh Hajipour

Abstract:

Effective factors on the mechanical wellbore stability are divided in to two categories: 1) Controllable factors, 2) Uncontrollable factors. The purpose of geo-mechanical modeling of wells is to determine the limit of controlled parameters change based on the stress regime at each point and by solving the governing equations the pore-elastic environment around the well. In this research, the mechanical analysis of wellbore stability was carried out for Soroush oilfield. For this purpose, the geo-mechanical model of the field is made using available data. This model provides the necessary parameters for obtaining the distribution of stress around the wellbore. Initially, a basic model was designed to perform various analysis, based on obtained data, using Abaqus software. All of the subsequent sensitivity analysis such as sensitivity analysis on porosity, permeability, etc. was done on the same basic model. The results obtained from these analysis gives various result such as: with the constant geomechanical parameters, and sensitivity analysis on porosity permeability is ineffective. After the most important parameters affecting the wellbore stability and instability are geo-mechanical parameters.

Keywords: wellbore stability, movement, stress, instability

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Authors: David Glew, Felix Thomas, Matthew Brooke-Peat

Abstract:

Improving the thermal performance of homes is seen as an essential step in achieving climate change, fuel security, fuel poverty targets. One of the most effective thermal retrofits is to insulate solid walls. However, it has been observed that applying insulation to the internal face of solid walls reduces the surface temperature of the inner wall leaf, which may introduce condensation risk and may interrupt seasonal moisture accumulation and dissipation. This research quantifies the extent to which the risk of condensation and moisture accumulation in the wall increases (which can increase the risk of timber rot) following the installation of six different types of internal wall insulation. In so doing, it compares how risk is affected by both the thermal resistance, thickness, and breathability of the insulation. Thermal bridging, surface temperatures, condensation risk, and moisture accumulation are evaluated using hygrothermal simulation software before and after the thermal upgrades. The research finds that installing internal wall insulation will always introduce some risk of condensation and moisture. However, it identifies that risks were present prior to insulation and that breathable materials and insulation with lower resistance have lower risks than alternative insulation options. The implications of this may be that building standards that encourage the enhanced thermal performance of solid walls may be introducing moisture risks into homes.

Keywords: condensation risk, hygrothermal simulation, internal wall insulation, thermal bridging

Procedia PDF Downloads 144