Under dynamic loading, the geomechanical properties of porous clastic rocks differ from those in quasistatic loading. A small experimental rig was built to directly assess the influence of vibrations on the uniaxial compressive strength (UCS), Young modulus, and Poisson’s ratio. A piezoelectric actuator powered by a signal from an oscillator was used in the rig as a generator of vibrations. A laser sensor and eddy current probe measured the longitudinal and transverse deformation. Tinius Hounsfield and Instron Series 4483 installations were used to determine the geomechanical properties of new red sandstone in a quasistatic regime. The boundaries of elastic deformations determined in the quasistatic loading were implemented in the dynamic loading. To perform the experiments in the elastic zone (on the graph of stress (σ)−strain (ε)), small samples with diameters ranging between 7.5 and 24.7 mm were manufactured. The investigation demonstrated that the Young’s modulus of the sandstone i... [more]

This study provides the engineering science underpinnings for improved characterization and quantification of the interplay of gases with kerogen and minerals in shale. Natural nanoporous media such as shale (i.e., mudstone) often present with low permeability and dual porosity, making them difficult to characterize given the complex structural and chemical features across multiple scales. These structures give nanoporous solids a large surface area for gas to sorb. In oil and gas applications, full understanding of these media and their sorption characteristics are critical for evaluating gas reserves, flow, and storage for enhanced recovery and CO2 sequestration potential. Other applications include CO2 capture from industrial plants, hydrogen storage on sorbent surfaces, and heterogeneous catalysis in ammonia synthesis. Therefore, high-resolution experimental procedures are demanded to better understand the gas−solid behavior. In this study, CT imaging was applied on the sub-millime... [more]

Thermal comfort (heating, ventilation and air conditioning, HVAC) and the energy consumption involved with it can put a strain on the driving range of fully electric vehicles (FEV), especially in certain times of the year as midsummer or winter. In order to reduce the energy consumption of HVAC, improved thermal management and adapted means of energy storage are needed. One part of the solution can be the use of phase change materials (PCM) for storing waste heat. For the specific application, however, a high loading/unloading power rate is required, which is challenging as the PCMs exhibit low heat conductivities. In the presented work, a storage demonstrator system was investigated which is part of an HVAC system of a specific fully electric vehicle. The profile of requirements of the system (power, stored capacity and allowed volume) make a new design of the storage necessary. Two demonstrator units, in which the PCM was combined with aluminum foam, were manufactured and their power... [more]

Briquetting is one of the recommended biomass agglomeration processes. The material subjected to briquetting gains valuable functional features related to higher energy density, appropriate moisture content, and increased bulk density. However, the briquettes need high mechanical durability to maintain high quality during transportation, loading, and other logistic steps before they will be delivered to the final consumer and utilized for energy purposes. The mechanical durability depends on many factors, including the particles comminution of the compacted biomass. Therefore, the aim of this study was to analyze the impact of particle comminution on the mechanical durability of wheat straw briquettes. The research was carried out in accordance with the international standard for solid biofuels PN-EN ISO 17831-1:2016-02. The briquettes were produced from three different fractions: 0−2 mm, 2−15 mm, and 15−45 mm. To obtain more data related to the mechanical durability of briquettes, the... [more]

The fire load of buildings is significantly increased by means of electric cables, usually creating a long combustible base for fire to spread and in this way decreasing the fire safety of buildings. The aim of the study was to evaluate a relationship between the construction of the cables and their fire properties, especially the mass loss influence on other fire properties of cables. Six cables of different core numbers were tested by means of the standard test method EN 50399. Additionally, thermogravimetric analysis and Attenuated Total Reflection—Fourier Transform Infrared analysis were performed on the separate outer sheath, bedding, and core insulations in order to determine the similarity of the materials’ chemical structures. It was found that: (1) the construction of the cable strongly influences the fire behavior due to the creation of a barrier for flame penetration and emission of combustion effluents though inside the closed agglomeration of non-combustible metallic cores... [more]

Renewable energy resources like solar energy, wind energy, hydro energy, photovoltaic etc. are gaining much importance due to the day by day depletion of conventional resources. Owing to the lower efficiencies of renewable energy resources, much attention has been paid to improving them. The concept of utilizing phase change materials (PCMs) has attracted wide attention in recent years. This is due to their ability to extract thermal energy when used in collaboration with photovoltaic (PV), thus improving the photoelectric conversion efficiency. In this paper, the objective is to design and fabricate a novel thermal energy storage system using phase change material. An investigation on the characteristics of Potash Alum as a phase change material due to its low cost, easy availability and its usage as an energy storage for the indoor purposes are taken into account. The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy... [more]

Drilling fluids are designed to be shear-thinning for limiting pressure losses when subjected to high bulk velocities and yet be sufficiently viscous to transport solid material under low bulk velocity conditions. They also form a gel when left at rest, to keep weighting materials and drill-cuttings in suspension. Because of this design, they also have a thixotropic behavior. As the shear history influences the shear properties of thixotropic fluids, the pressure losses experienced in a tube, after a change in diameter, are influenced over a much longer distance than just what would be expected from solely entrance effects. In this paper, we consider several rheological behaviors that are relevant for characterizing drilling fluids: Collins−Graves, Herschel−Bulkley, Robertson−Stiff, Heinz−Casson, Carreau and Quemada. We develop a generic solution for modelling the viscous pressure gradient in a circular pipe under the influence of thixotropic effects and we apply this model to configur... [more]

Pore structure has been widely observed to affect the seismic wave velocity of rocks. Although taking lab measurements on 1.0-inch core plugs is popular, it is not representative of the fractured-vuggy carbonates because many fractures and vugs are on a scale up to several hundred microns (and greater) and are spatially heterogeneous. To overcome this shortage, we carried out the lab measurements on full-diameter cores (about 6.5−7.5 cm in diameter). The micro-CT (micro computed tomography) scanning technique is used to characterize the pore space of the carbonates and image processing methods are applied to filter the noise and enhance the responses of the fractures so that the constructed pore spaces are reliable. The wave velocities of P- and S-waves are determined then and the effects of the pore structure on the velocity are analyzed. The results show that the proposed image processing method is effective in constructing and quantitatively characterizing the pore space of the full... [more]

In this study, amorphous manganese oxide (MnO2) nanostructured thin films were synthesized by a simple hydrothermal method. It is well known that the nanostructure plays a crucial role in energy storage applications. Herein, MnO2 nanostructures ranging from plates to flakes were synthesized without the use of any hard or soft templates. The 4+ oxidation state of Mn was confirmed by X-ray photoelectron spectroscopy. The MnO2 nanoflake structure has a specific surface area of 46 m2g−1, which provides it with an excellent rate capability and an exactly rectangular cyclic voltammogram (CV) curve. The MnO2 nanoflake electrode has a high specific capacitance of about 433 Fg−1, an energy density of 60 Whkg−1 at 0.5 mAcm−2, and an excellent cyclic stability of 95% over 1000 CV cycles in 1 M aq. Na2SO4. Kinetics analysis of the charge storage in the nanoflake MnO2 sample shows a 55.6% diffusion-controlled contribution and 44.4% capacitive-controlled contribution to the total current calculated... [more]

This research qualitatively and quantitatively characterises the minor chemical elements in diesel particulate matter (DPM). DPM was extracted from in-use diesel engine passenger vehicles of diverse types and models from major brand car producers in Europe. We analysed particulate matter extracted from the exhaust manifold part from passenger vehicles that are used in daily life environment. To qualitatively and quantitatively characterise the DPM, we employed the high-resolution Laser-Induced Breakdown Spectroscopy analytical technique (LIBS). Qualitative spectrochemical LIBS analyses confirmed the presence of minor chemical elements—silicon, nickel, titan, potassium, strontium, and molybdenum in DPM. For quantification of the LIBS signal, the calibration functions were constructed from internal calibration standards. Different concentrations of detected minor elements Si, Ni, Ti, K, Sr, and Mo were measured with respect to the type of complex particulate matter.

Turbulent flows around bluff bodies are present in a large number of aeronautical, civil, mechanical, naval and oceanic engineering problems and still need comprehension. This paper provides a detailed investigation of turbulent boundary layer flows past a bluff body. The flows are disturbed by superficial roughness effect, one of the most influencing parameters present in engineering applications. A roughness model, recently developed by the authors, is here employed in order to capture the main features of these complex flows. Starting from subcritical Reynolds number simulations (Re = 1.0 × 105), typical phenomena found on critical and supercritical flow regimes are successfully captured, like non-zero lift force and its direction change, drag crisis followed by a gradual increase on this force, and separation and stagnation points displacement. The main contribution of this paper is to present a wide discussion related with the temporal history of aerodynamic loads of a single roug... [more]

In this study, a full-scale three-dimensional trapezoidal thermoelectric cooler model is constructed to study its cooling performance and mechanical reliability using finite element simulation. Temperature dependent material properties are considered in this work. The boundary conditions similar to those in a real experimental environment are applied. The effects of the input electrical current and geometry of the thermoelectric leg on the cooling performance and reliability of a trapezoidal thermoelectric cooler are analyzed, and a comparison is made with a rectangular thermoelectric cooler. The results indicate that increasing the leg height and the variable cross-sectional design of the leg can improve the cooling performance of the trapezoidal thermoelectric cooler. Compared to the original rectangular thermoelectric cooler, the minimum chip temperature was reduced by 0.87% under the trapezoidal thermoelectric cooler with optimized geometry. Furthermore, increasing the leg height e... [more]

The western region of China is rich in mineral resources. The vigorous development of mineral resources has exacerbated the environmental and safety problems in the region. One of the important links to solve this problem is to control the development laws and distribution characteristics of the overburdened cracks in the mining of this area. In this paper, the Xiashijie coal mine 3-2 coal seam and 4-2 coal seam are examples of repeated mining, and are examined as the background, through theoretical analysis to optimize the size of the coal pillars in the lower section, using the 3DEC numerical simulation experiment method and the rise of the cracks in the short-distance coal seam. Repeated mining monitoring and analysis of the development law are used to ascertain distribution characteristics of overburdened cracks caused by the repeated mining process of the working face. The results show that: (1) By establishing a mechanical model of the overlying strata structure under short-dista... [more]

The sample size or particle size of shale plays a significant role in the characterization of pores by various techniques. To systematically investigate the influence of particle size on pore characteristics and the optimum sample size for different methods, we conducted complementary tests on two overmature marine shale samples with different sample sizes. The tests included small-angle neutron scattering (SANS), gas (N2, CO2, and H2O) adsorption, mercury injection capillary pressure (MICP), and field emission-scanning electron microscopy (FE-SEM) imaging. The results indicate that artificial pores and fractures may occur on the surface or interior of the particles during the pulverization process, and some isolated pores may be exposed to the particle surface or connected by new fractures, thus improving the pore connectivity of the shale. By comparing the results of different approaches, we established a hypothetical model to analyze how the crushing process affects the pore structu... [more]

Biodegradable containers support zero-waste initiatives when alternative end-of-life scenarios are available (e.g., composting, bio digestion). Thermoplastic starch (TPS) has emerged as a readily biodegradable and inexpensive biomaterial that can replace traditional plastics in applications such as food service ware and packaging. This study has two aims. First, demonstrate the thermoformability of starch/polycaprolactone (PCL) as a thermoplastic material with varying starch loadings. Second, incorporate biochar as a sustainable filler that can potentially lower the cost and enhance compostability. Biochar is a stable form of carbon produced by thermochemical conversion of organic biomass, such as food waste, and its incorporation into consumer products could promote a circular economy. Thermoformed samples were successfully made with starch contents from 40 to 60 wt.% without biochar. Increasing the amount of starch increased the viscosity of the material, which in turn affected the c... [more]

A characteristic feature of lightweight constructions is their low thermal mass which causes high internal temperature fluctuations that require high heating and cooling demand throughout the year. Phase change materials (PCMs) are effective in providing thermal inertia to low-thermal-mass buildings. This paper aims to analyse the thermal behaviour of two proposed lightweight buildings designed for homeless people and to investigate the potential benefit achievable through the use of different types of PCM in the temperate climatic conditions of Christchurch, New Zealand. For this purpose, over 300 numerical simulations were conducted using DesignBuilder® simulation software. The bulk of the simulations were carried out under the assumption that the whole opaque building envelope is equipped with PCM. The results showed significant energy saving and comfort enhancement through the application of PCMs. The integration of PCM in single-structure components led to substantial energy savin... [more]

Measuring the probability of flood risk is a key issue in the economics of natural disasters. This discipline studies actual and potential effects of natural disasters on the functioning of economic systems. In traditional economic understanding, it is assumed that both the decision making processes and market processes operate within a certain level of access to information. It is also assumed that the effects of certain phenomena are predictable. However, a natural disaster is difficult to predict. It is hard to predict the time of its occurrence, its impact, direct exposure to its effects and finally, its social and economic results. Exposure to a random hazard, combined with the amount of damage resulting from its potential materialization, is called risk. In this study, the authors focus on presenting a method for quantification of the random element of flood risk. We are using measurement data for cross-border areas between Poland and Germany who witnessed a flood of the century... [more]

This work introduces the concept of a new Portable Device for Indoor Temperature Stabilization (PoDIT), to be considered as a low-cost, quick and easy to implement remediation strategy when, for social, economic, or technical reasons, the improvement of the building envelope and/or the adoption of air conditioning are not possible. The main goal is to attenuate the maximum indoor temperature during summer and/or heat waves. The system, which is modular, consists of a certain mass of encaged phase change material (PCM) that stays indoors during the daytime and is transported to the outdoors (e.g., a balcony) during the night to discharge the heat accumulated during the daytime. Both natural convection and forced convection variants were considered. The results showed that, in the configurations and for the reference room and weather considered, the adopting 4 modules of the device can lead to reductions in the maximum room air temperature close to 3 °C, with natural convection. Adopting... [more]

Sintering and carbon deposition are the two main ways to deactivate Ni-based catalysts during methane reforming. Herein, a stable Ni-CeO2/SiO2(CSC) catalyst was prepared by a one-step colloidal solution combustion method (CSC) and used for dry reforming of methane. In the catalyst, the small Ni particles were confined by CeO2 particles and highly dispersed on the surface of SiO2, forming a spatial confinement structure with a rich Ni-CeO2 interface in the catalyst. The Ni-CeO2/SiO2(CSC) catalyst prepared by the one-step CSC method exhibited superior activity at 700 °C during dry reforming of methane, and the performance of the catalyst was stable after 20 h of reaction with only a small amount of carbon deposition present (1.8%). Due to the spatial confinement effect, Ni was stable and less than 5 nm during reaction. The small Ni particle size and rich Ni-CeO2 interface reduced the rate of carbon deposition. This colloidal combustion method could be applied to prepare stable metal-base... [more]

The breakdown of the drill bit or rapid decrease of the rate of penetration during the drilling process results in a delay in the progress of drilling. Scientists and engineers are increasingly focusing on research to extend the bit life and improve the drilling rate. In our work, “in situ” drilling parameters were monitored during the drilling process with the roller cone drill bit IADC 136, diameter 155.57 mm (6 1/8"). After drilling, the bit was thoroughly examined to determine the damage and wear that occurred during drilling. The following modern and standardized investigative methods were used: an analysis of rock materials and an analysis of micro and macrostructure materials of the roller cone bit. Analyses were carried out using optical and electron microscopy, a simultaneous thermal analysis of materials of drill bit, analysis of the chemical composition of materials of drill bit, and a determination of the geomechanical parameters of rock materials. The resulting wear, local... [more]

This paper presents laboratory studies based on which a stimulation technology for an oil field located in the Zechstein Main Dolomite was investigated. A large number of oil wells in the Main Dolomite produce significant amounts of reservoir water. Matrix acidizing using conventional acid solutions in such wells has caused a significant increase in water cut, because of their affinity for water. The purpose of this cooperation between the Oil and Gas Institute−NRI and the Brenntag Polska was to develop an acid treatment technology that would not increase the water cut after acidizing treatment in wells where oil production is accompanied by the production of reservoir water. Therefore, a series of tests were performed, including the selection of a suitable viscoelastic surfactant that was sensitive to crude oil. The contact of the gel of the viscoelastic surfactant fluid with crude oil resulted in the reduction of its viscosity The tests described herein include dissolution/dispersion... [more]

In this study, inorganic stannite quaternary Cu2M(M = Ni, Co)SnS4 (CMTS) is explored as a low-cost, earth abundant, environmentally friendly and chemically stable hole transport material (HTM). CMTS nanoparticles were synthesized via a facile and mild solvothermal method and processed into aggregated nanoparticle inks, which were applied in n-i-p perovskite solar cells (PSCs). The results show that Cu2NiSnS4 (CNiTS) is more promising as an HTM than Cu2CoSnS4 (CCoTS), showing efficient charge injection as evidenced by considerable photoluminescence quenching and lower series resistance from Nyquist plots, as well as higher power conversion efficiency (PCE). Moreover, the perovskite layer coated by the CMTS HTM showed superior environmental stability after 200 h light soaking in 50% relative humidity, while organic HTMs suffer from a severe drop in perovskite absorption. Although the obtained PCEs are modest, this study shows that the cost effective and stable inorganic CMTSs are promisi... [more]

Thermochemical processes are considered promising pathways to utilize solar energy for fuel production. Several physico-chemical, kinetic and thermodynamic properties of candidate oxides have been studied, yet their morphological stability during redox cycling under radiative heating is not widely reported. Typically when it is reported, it is for large-scale directly irradiated reactors (~1−10 kWth) aimed at demonstrating high efficiency, or in indirectly irradiated receivers where the sample surface is not exposed directly to extreme radiative fluxes. In this work, we aimed to emulate heat flux conditions expected in larger scale solar simulators, but at a smaller scale where experimentation can be performed relatively rapidly and with ease compared to larger prototype reactors. To do so, we utilized a unique infrared (IR) laser-based heating system with a peak heat flux of 2300 kW/m2 to drive redox cycles of two candidate materials, namely nonstoichiometric CeO2-δ and La0.6Sr0.4MnO3... [more]

The global occurrences of natural gas hydrates lead to the conclusion that tremendous amounts of hydrocarbons are bonded in these hydrate-bearing sediments, serving as a potential energy resource. For the release of the hydrate-bonded CH4 from these reservoirs, different production methods have been developed during the last decades. Among them, the chemical stimulation via injection of CO2 is considered as carbon neutral on the basis of the assumption that the hydrate-bonded CH4 is replaced by CO2. For the investigation of the replacement process of hydrate-bonded CH4 with CO2 on a µm-scale, we performed time-resolved in situ Raman spectroscopic measurements combined with microscopic observations, exposing the CH4 hydrates to a CO2 gas phase at 3.2 MPa and 274 K. Single-point Raman measurements, line scans and Raman maps were taken from the hydrate phase. Measurements were performed continuously at defined depths from the surface into the core of several hydrate crystals. Additionally... [more]

The power conversion efficiency of lead halide perovskite solar cells has been elevated to 25.2%. However, the toxicity of lead and the complex fabrication process of those cells considerably hinder the commercial application of such solar cells. Therefore, lead-free solar cells with comparable power conversion efficiency with a much lower environmental impact have recently attracted enormous attention in both academia and industry. This paper presents a theoretical study to assess the energy conversion capacity of lead-free perovskite solar cells with MASnI3 perovskite as its absorber layer using solar cell capacitance simulator (SCAPS). In particular, the effects of materials of the perovskite solar cells’ electron transport layers (ETLs) and hole transport layers (HTLs) on their energy conversion performance are elaborated. Our results show that Cd0.5Zn0.5S and MASnBr3 are the most suitable materials for ETL and HTL, respectively. It is also found from that the solar cell performanc... [more]