Liquid carbon dioxide (L-CO2) phase-transition blasting technology (LCPTB) has caused wide concern in many fields, but there is a lack of research on the initiation of the carbon dioxide fracturing pipe. Studies regarding the carbon dioxide fracturing pipe initiation are critical for controlling and optimizing the LCPTB. Therefore, in this article, a series of exploratory experiments of carbon dioxide blasting were carried out to investigate the qualitative and quantitative relationships between the carbon dioxide fracturing pipe initiation and the three key variables (the filling mass of liquid carbon dioxide (L-CO2) (X1), the amount of chemical heating material (X2) and the thickness of the constant-stress shear plate (X3)). The failure mechanisms of three variables on the phase-transition blasting process of a carbon dioxide fracturing pipe was analyzed qualitatively based on experiment temperature, strain curve and failure form of constant-stress shear plate. An empirical model bet... [more]

Macrosurfactants consisting of water-soluble poly(vinylcaprolactam) (PVCap) or poly(vinylpyrrolidone) (PVP) segments with comparatively shorter hydrophobic poly(styrene) (PS) or poly(2,3,4,5,6-pentafluorostyrene) (PPFS) segments were used as kinetic hydrate inhibitors (KHIs). These were synthesized with 2-cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)dithiocarbamate switchable reversible addition−fragmentation chain transfer (RAFT) agent at 60 °C or 90 °C for 1-P(S/PFS) or 1-PVCap, respectively, followed by chain extension at 90 °C or 70 °C with PVCap or PVP, respectively. The addition of PVCap to the pure methane-water system resulted in a 53% reduction of methane consumption (comparable to PVP with 51% inhibition) during the initial growth phase. A PS-PVCap block copolymer comprised of 10 mol% PS and 90 mol% PVCap improved inhibition to 56% compared to the pure methane-water system with no KHIs. Substituting PS with a more hydrophobic PPFS segment further improved inhibition to 73%. By i... [more]

Switchable ethoxylated amine surfactants are readily soluble in CO2 and high-saline brines. The objective of the current work is to maximize the foamability and stability of CO2 foam at 150 °F (65 °C) through adjustments in the surfactant concentration, pH, and brine salinity. From the results, the authors recommend potential applications of Ethomeen C12 (EC12) for CO2 foam in the oil/gas industry. Foam stability tests helped determine the optimum parameters for CO2 foam stability at 77 °F (25 °C) and 150 °F (65 °C). The surface tension of EC12 as a function of concentration was evaluated using a drop-shape analyzer. Maximum foam stability was observed for a solution comprising of 1.5 wt% EC12, 25 wt% NaCl, and pH 6.5 at 150 °F (65 °C). The interactions with the salts allowed closer packing of the surfactant molecules at the lamellae and strengthening the foam. At a pH of 2.5, the absence of salt led to poor foam stability. However, at the same pH and in the presence of sodium chloride... [more]

Latent heat storage (LHS) represents a valuable technology for the integration of intermittent renewable energy sources in existing and future energy systems. Improvements in LHS can be sought by enhancing heat transfer efficiency, compactness and diminishing the environmental impact of storage systems. In this paper, direct contact latent heat storage (DC-LHS) using esters as phase change material (PCM) is proposed as a promising compact storage technology to achieve high performance both in terms of heat transfer and sustainability. The technology allows for the heat transfer fluid (HTF) to flow directly through the PCM, forming a large amount of small droplets and thus providing a large heat exchange surface area between the two materials. At the same time, using biobased esters as PCM, gives the technology clear ecological advantages when compared to alternative types of compact energy storage. Furthermore, no complex heat transfer enhancing structures are necessary in a DC-LHS, fu... [more]

Increasing environmental demands influence the requirements for devices and materials used in the power industry. One example is a power transformer and an electro-insulating liquid used in it. In order to meet these requirements, electro-insulating liquids should be characterized by, inter alia, high biodegradability and good fire properties. One of such liquids is natural ester. However, its oxidation stability is low in comparison to mineral oil and demands improvement, which can be achieved by the addition of an antioxidant. The authors of this work used fullerene nanoparticles for that purpose. Pure natural ester samples were prepared, and samples with two concentrations of fullerene, 250 mg/L and 500 mg/L in natural ester. All these samples were aged in a thermal oxidation process. Thereafter, the aging properties of all the samples were compared to assess the oxidation stability of modified liquids. Moreover, the electrical properties of prepared insulating liquids were investig... [more]

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations (between (Re1, Re2) = (250, 250) to (1000, 1000)), horizontal distance of the jet inlet from the thermoelectric device (between (r1, r2) = (−0.25, −0.25) to (1.5, 1.5)), impinging jet inlet to target surfaces (between w2 and 4w2) and solid nanoparticle volume fraction (between 0 and 2%) on the interface temperature variations, thermoelectric output power generation and conversion efficiencies are numerically assessed. Higher powers and efficiencies are achieved when the jet stream Reynolds numbers and nanoparticle volume fractions are increased. Generated power and efficiency enhancements 81.5% and 23.8% when lowest and highest Reynolds number combinations are compared. However, the power enhancement... [more]

This study evaluated Al-ZSM-5 nanocrystals grown from silicalite-1 seed crystals as catalysts for the methane dehydroaromatization (MDA) reaction. Silicalite-1 seed crystals sized between 30 and 40 nm were used to grow Al-ZSM-5 under various synthesis conditions. The size of Al-ZSM-5 was significantly affected by the Si/Al ratio (SAR), synthesis time, and silica nutrients/seed crystal ratio (NSR). Larger crystals were obtained with an increased SAR in the synthesis sols. Gradual growth of Al-ZSM-5 occurred with synthesis time, although the growth in crystal size ceased at 5 h of synthesis at 120 °C, indicating the rapid growth of Al-ZSM-5 aided by the silicalite-1 seeds. Precise tuning of Al-ZSM-5 size was possible by changing the nutrient/silicalite-1 seed ratio; a higher NSR led to larger crystals. Two representative Al-ZSM-5 crystals with SARs of 35 and 140 were prepared for catalyst testing, and the crystal sizes were tailored to <100 nm by controlling NSR. The MDA reaction was... [more]

High-strength bolted shear connectors (HSBSCs), which can be demounted easily and efficiently during deconstruction, are recommended to replace the conventional steel studs in steel−concrete composite beams (SCCBs) to meet the requirements of sustainable development. The existing investigations on the behavior of HSBSCs mainly focus on the positive moment area of composite beams, in which the concrete slab is in compress condition. In this paper, a three-dimensional finite element model (FEM) was developed to investigate the performance of HSBSCs subjected to inverse push-off loading. Material nonlinearities and the interactions among all components were included in the FEM. The accuracy and reliability of the proposed FEM were initially validated against the available push-off test results. Load-carrying capacity and load−slip response of the HSBSCs under inverse push-off loading were further studied by the verified FEM. A parametric study was carried out to determine the influence of... [more]

In this study, a new formulation of low-cost, biodegradable, and non-toxic biosurfactant by Candida sphaerica UCP 0995 was investigated. The study was conducted in a bioreactor on an industrial waste-based medium, and a central composite rotatable design was used for optimization. The best results, namely a 25.22 mN/m reduction in surface tension, a biosurfactant yield of 10.0 g/L, and a critical micelle concentration of 0.2 g/L, were achieved in 132 h at an agitation speed of 175 rpm and an aeration rate of 1.5 vvm. Compositional and spectroscopic analyses of the purified biosurfactant by chemical methods, Fourier transform infrared spectroscopy, and nuclear magnetic resonance suggested that it is a glycolipid-type biosurfactant, and it showed no cytotoxicity in the MTT assay. The biosurfactant, submitted to different formulation methods as a commercial additive, remained stable for 120 days at room temperature. Tensioactive properties and stability were evaluated at different pH valu... [more]

Cool roofs use reflective materials or coatings to reflect a portion of the incident solar radiation. This results in a lowering the surface temperature of the cool roof compared to black roofs, and thus helps reduce the cooling energy loads during the summer season. The research reported in this paper was conducted to assess experimentally and numerically the performance of cool and black roofs that were subjected to the hot, humid and dusty climate of Jubail Industrial City (JIC). This paper focused on characterizing one of the important properties of reflective coating material (RCM), which is its solar reflectivity. In this study, the effect of dust/dirt accumulation on the solar reflectivity of the RCM was investigated at different exposure times to the natural weathering conditions of JIC. The test results showed that dust and dirt can significantly contribute in reducing the solar reflectivity of the RCM. As such, a number of cleaning processes were conducted on the surface of t... [more]

The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on the temperature, must be assessed in order to effectively implement this solution. In this study, experimental temperature data were obtained over two years for four structures built with different photovoltaic technologies (mono-crystalline silicon, amorphous silicon, cadmium telluride, and an organic polymeric technology) and fitted to a thermal model in order to provide a comprehensive analysis of their potential utilization as a cover material in greenhouses. Additionally, the thermal effect of color in structures composed of several common construction materials (brick, wood, plasterboard and glass) was quantified and modelled, supplementing the thermal analysis of passive solutions for this application. In all cases, inner and ambient temperatur... [more]

Perovskite solar cells (PSCs) have already achieved comparable performance to industrially established silicon technologies. However, high performance and stability must be also be achieved at large area and low cost to be truly commercially viable. The fully printable triple-mesoscopic carbon perovskite solar cell (mCPSC) has demonstrated unprecedented stability and can be produced at low capital cost with inexpensive materials. These devices are inherently scalable, and large-area modules have already been fabricated using low-cost screen printing. As a uniquely stable, scalable and low-cost architecture, mCPSC research has advanced significantly in recent years. This review provides a detailed overview of advancements in the materials and processing of each individual stack layer as well as in-depth coverage of work on perovskite formulations, with the view of highlighting potential areas for future research. Long term stability studies will also be discussed, to emphasise the impre... [more]

A mono-dimensional code for the simulation of the effects of High Frequency Ignition systems (HFI) on the production of chemical radicals was developed and here presented. The simulations were carried out by considering the typical environmental thermodynamic conditions of a nowadays engine at full load. An electron transport model is linked with a Boltzmann solver coupled with a chemistry solver, affecting the Electron Energy Distribution Function (EEDF) in order to obtain the physical conditions leading to the production of radical components for a given fuel mixture. The transport equations for the electrons, the positive and the negative ions, and the Gauss’ law in a steady-state plasma region. Then the Boltzmann equation for the electrons, in a spatially homogeneous steady-state case, is solved in order to obtain the EEDF. Finally the chemical kinetics model is employed assuming a fuel-air mixture neglecting the fuel carbon atoms due to the assumption that electron-impact dissocia... [more]

In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, exergy is used as a measure of the resource consumption during the life cycle of polymers. Nine commercially diffused polymers are chosen, and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) is calculated as the sum of the contribution of each step of the chain, including the production process and the Exergy Replacement Cost (ERC) of the fossil fuel. Then, recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the crude polymeric material and the oil derivatives or structural molecules. The main results show that some commonly used polymers ha... [more]

To help mitigate the effects of global warming and fossil fuel depletion caused by human use of fossil fuels, solid fuel pellets were developed from a mixture of spent coffee grounds (SCG) and pine sawdust (PS). The feasibility of SCG-PS pellets as biofuel was also verified by evaluating its fuel quality. An increase in the proportion of SCG in the pellet led to an increase in its calorific value, owing to the high C, H, and oil contents, and increases in the ash and S contents, owing to the high S content in SCG. Analysis of the feedstock particle size distribution revealed that SCG particles are smaller than PS particles; thus, the durability of the pellet decreases as the proportion of SCG increases. Accordingly, the samples with higher SCG proportions (70 and 90 wt.%) did not meet the moisture content standards for biomass solid refuse fuel (bio-SRF) set by the Korea Ministry of Environment, whereas the samples with lower SCG proportions did. In particular, CP10 (10 wt.% SCG + 90 w... [more]

As DC transmission voltage increases, the DC wall bushing becomes longer, and a supporting insulator is introduced to keep the conductor straight. Under extremely high electric fields coupled with a thermal gradient, the surface charge of the supporting insulator may distort the field distribution and increase the risk of flashover. In this paper, surface potentials of three model epoxy resin composites were systematically investigated under varied voltage amplitudes, different voltage polarities and electric field distributions. The bulk and surface resistivity of the epoxy resin composites over a broad temperature range were measured to reveal the correlations between surface charge and such basic electrical parameters. The results indicate that the normal-dominated electric field plays the major role in charge accumulation. The processes of surface charge accumulation and dissipation are more closely related to the surface resistivity. As a result, the surface charge properties can... [more]

With the depletion of traditional energy resources, the share of heavy-oil production has been increasing recently. According to some estimates, their reserves account for 80% of the world’s oil resources. Costs for extraction of heavy oil and natural bitumen are 3−4 times higher than the costs of extracting light oil, which is due not only to higher density and viscosity indicators but also to insufficient development of equipment and technologies for the extraction, transportation, and processing of such oils. Currently, a single pipeline system is used to pump both light and heavy oil. Therefore, it is necessary to take into account the features of the heavy-oil pumping mode. This paper presents mathematical models of heavy-oil flow in oil-field pipelines. The rheological properties of several heavy-oil samples were determined by experiments. The dependencies obtained were used as input data for a simulation model using computational fluid dynamics (CFD) methods. The modeling condit... [more]

The poor loading performance of shearer drums restricts the development and production efficiency of coal in thin coal seams. Changing operation and structural parameters can improve the drum’s loading performance to some extent, but the effect is not obvious. A two-segment differential rotational speed drum (TDRSD) was proposed after analyzing the drum’s influence mechanism on coal particles. To further reveal the drum’s coal loading principle, the velocity, particles distribution, and loading rate were analyzed. The effect of the matching relationship of the rotational speed and helix angle between the front and rear drum are also discussed. The results show that a lower front drum rotational speed had a positive impact on improving the loading performance, and the loading rate first increases and then decreases with the increase in rear drum rotational speed. The optimal loading performance was obtained in the range 60−67.5 rpm. The front drum’s helix angle had no evident effect on... [more]

Nowadays, Organic Rankine Cycle (ORC) is one of the most promising technologies analyzed for electrical power generation from low-temperature heat such as renewable energy sources (RES), especially solar energy. Because of the solar source variation throughout the day, additional Thermal Energy Storage (TES) systems can be employed to store the energy surplus saved during the daytime, in order to use it at nighttime or when meteorological conditions are adverse. In this context, latent heat stored in phase-change transition by Phase Change Materials (PCM) allows them to stock larger amounts of energy because of the larger latent energy values as compared to the specific heat capacity. In this study, a thermal analysis of a square PCM for a solar ORC is carried out, considering four different boundary conditions that refer to different situations. Furthermore, differences in including or not natural convection effects in the model are shown. Governing equations for the PCM are written w... [more]

The construction industry is responsible for a large amount of both embodied carbon and emissions. Especially with concrete, there is still a lot of potential for designing recipes in a more ecological way. Approaches to reduce the environmental impact of concrete include the use of industrial and agricultural by-products. This study combines the approaches of replacing cement with granulated blast furnace slag and the use of NaOH-treated rice straw fibers. The research objective comprises the design of an ecologically optimized concrete as well as the question of whether a pretreatment of rice straw fibers with NaOH improves the performance of the designed concrete. The method includes mechanical and physical testing of the of the designed concrete as well as an optical analysis with a scanning electron microscope. The results indicated that treating rice straw with 1% NaOH indicates a better bond between fibers and the surrounding matrix. The tests in which the rice straw was treated... [more]

A slightly and two severely biodegraded crude oils with the same origin were analysed using negative-ion electrospray ionization Orbitrap mass spectrometry (ESI Orbitrap MS), gas chromatography-nitrogen chemiluminescence detector (GC-NCD), and GC-sulfur chemiluminescence detector (GC-SCD) to investigate the composition of heteroatomic compounds and their fate during severe biodegradation and to provide insights into biodegradation pathway of hopanes, nitrogen- and sulfur-containing compounds. Twelve heteroatomic compound classes, including O1−O5, N1, N2, N1O1−N1O3, N1S1 and O3S1, were detected and assigned unambiguous molecular formulae. The O1 species are likely phenols with additional naphthenic and/or aromatic rings. Carboxylic acids (O2 species) are originated from oxidation of hydrocarbons, and the tricyclic naphthenic acids are the most resistant, followed by bicyclics. Hopanes could be biodegraded by demethylation or by unstable hopanoic acids as intermediates to yield 25-norhop... [more]

For hydrothermal liquefaction of dry biomass to produce liquid fuels, water needs to be added or the aqueous phase products can be recycled. This paper focuses on understanding the relationship between hydrothermal degradation of the dry biomass and oil formation under the condition of accumulative recycling of the aqueous phase. Completely dried corn stalk and deionized water were used for the hydrothermal liquefaction (HTL) experiment. The aqueous products for subsequent recycling were not diluted. It was demonstrated that the recycling of the aqueous can promote the enrichment of organic acids and the conversion of ketones and phenols in the aqueous, improving the yield and quality of Bio-crude oil. After recycling, the yield of Bio-crude oil increased from 20.42% to 24.31% continuously, and the oxygen content decreased from 13.34% to 9.90%. Although the process was accompanied by solid deposition and had a negative impact on the hydrothermal degradation efficiency, the formation of... [more]

This paper presents an algorithm to remove the DC drift from the B-H curve of an additively manufactured soft ferromagnetic material. The removal of DC drift from the magnetization curve is crucial for the accurate estimation of iron losses. The algorithm is based on the sliding mean value subtraction from each cycle of calculated magnetic flux density (B) signal. The sliding mean values (SMVs) are calculated using the convolution theorem, where a DC kernel with a length equal to the size of one cycle is convolved with B to recover the drifting signal. The results are based on the toroid measurements made by selective laser melting (SLM)-based 3D printing mechanism. The measurements taken at different flux density values show the effectiveness of the method.

Additive manufacturing has many advantages over traditional manufacturing methods and has been increasingly used in medical, aerospace, and automotive applications. The flexibility of additive manufacturing technologies to fabricate complex geometries from copper, polymer, and ferrous materials presents unique opportunities for new design concepts and improved machine power density without significantly increasing production and prototyping cost. Topology optimization investigates the optimal distribution of single or multiple materials within a defined design space, and can lead to unique geometries not realizable with conventional optimization techniques. As an enabling technology, additive manufacturing provides an opportunity for machine designers to overcome the current manufacturing limitation that inhibit adoption of topology optimization. Successful integration of additive manufacturing and topology optimization for fabricating magnetic components for electrical machines can en... [more]

Lignite (ulminite reflectance Rr = 0.27%) from the Szczerców deposit (Central Poland) is dominated by huminite group macerals, containing a high proportion of attrinite and densinite. Densinite and ulminite are more abundant in small aromatic units than attrinite, which may result from their stronger gelification. The differences in Raman spectral characteristics between attrinite and ulminite are more pronounced than between attrinite and densinite. Fusinite, in comparison with the huminite group macerals, is composed of larger, more varied aromatic systems. The D4 (1190−1200 cm−1) and D5 bands (1280−1290 cm−1), most likely, correspond to different chemical structures, and their origin should be further investigated.