Papers by Keyword: Specific Energy

Abstract: This research investigates the effective moisture diffusivity (D_eff) and energy activation (E_a) as it affects thin layer drying of white yam (Dioscorea rotundata) slices using hybrid drying system under different parameters. These factors helps researchers and food producers to develop optimized drying processes for yam slices in order to minimize drying time, improve energy efficiency, and maintain high product quality. The experimental analysis highlight the interplay between pretreatments (Blanching, B; Sodium metabisulfite, SNa; Neem bark extract, SNBE and Control, C), drying systems (indirect solar drying: ISD and solar-powered hot-air supplemented drying: SPHSD under 0.8 m/s and 1.2 m/s air velocity, and air temperatures of 50 °C, 60 °C, and 70 °C) and slice thickness (5 and 3 mm) on white yam slices during drying. Important data were obtained using Arduino based data logging system for accuracy. Mass transfer during the entire drying of the yam slices took place entirely in the falling drying rate period and was described using Fourier approach based on Fick’s second equation of diffusion. The result demonstrated that D_eff and E_a is significantly affected by petreatment, slice thicknesses, air velocity and drying system. D_eff increased with rising drying temperature and air velocity. However, SPHSD, at 5 mm thickness exhibited a decrease in D_eff compared to 3 mm with values ranging from 1.647 × 10^-10 to 2.790 × 10^-10 m²/s within the investigated parameters. In contrast, ISD and sun-dried yam slices displayed relatively lower and fluctuating D_eff values (not higher than 1.4 × 10^-10), likely due to intermittency in solar radiation. Specific energy consumption varies from 6184.373 J/kg.K to 4620.571 J/kg.K for different thicknesses, temperature and air velocity. Thermal efficiency values which decreases with increased slice thickness ranges from 52.539 % to 39.347 %. Drying efficiency increases with increased temperature and air velocity for SPHSD (87.020 % to 93.169 %) while ISD has the least at 54.196 %.

Abstract: Charge transport is one of the most important phenomena, which directly influences the performance of the energy storage and conversation devices. In this work, the authors provide an overview of various rechargeable energy storage battery chemistries and designs, and discuss the charge transport processes related to power capability of the lithium-ion technology. The load distribution by parallel connection of high power batteries or supercapacitor and high-energy cells is discussed and general conclusions are provided. Thus, the reduced peak power load on the high-energy cells are approved by simulation and experiment in passive parallel circuitry of high power and a high energy lithium-ion cells. The definition and advantages of the earlier deduced electrical loss time are explained. It is shown, that at a constant C-rate, defined as the ratio of the applied current and the rated cell capacity in Ah, the electrical loss time has a direct linear correlation to efficiency, and that the electrical loss time allows a direct power capability comparison of various battery cell chemistries and systems. The power capability, specific energy, and energy density of the industry relevant Li-ion battery cells based on electrical loss time approach are summarized and the following conclusions made. Today prismatic cells reach the maximum specific energy of small cylindrical cells, at the same time showing a little bit better power capability, than the investigated high energy cylindrical cells.

Abstract: The current concept of grinding or abrasive machining involves the formation and removal of segmented strips of material termed chips from the surface of the solid. A novel cutting mechanism is hereby presented in this research study that suggests that the generation of chips from the surface does not occur but only a shearing process that splits material creating added surface features and textures in the silicon surface. This arises from the unique set of factors of abrasive grit size, thrust force, polishing speed, and polishing time that lead to phase transformations in the surface layers of the silicon wafers. Statistical analysis of the factor effects yielded results that show the surface roughness values, Ra and Rz, increasing without any appreciable change in the thickness of the silicon wafers. This can be attributed to the proposed cutting mechanism indicating that only in-plane surface shearing occurred due to the change of the silicon crystal structure from exhibiting brittle behavior to that of ductile mode of deformation. Moreover, experimental quantities of the specific energy for surface machining of silicon was calculated with an overall mean of 50.5 GPa. This is about 33% less than the currently accepted value and can be considered further evidence that polymorphic transitions to a softer material occurred rendering the surface layers more susceptible to longitudinal cutting deformation and fracture. A model based on the inverted spherical cap or spherical bottom geometry for the individual abrasive particle is also proposed, verified by a finite element method analysis simulation, that can mathematically describe this particular micromachining process.

Abstract: This paper presents the crashworthiness performance of carbon reinforced epoxy laminate tubular structure of three different kind tubes made of 0˚ plies Unidirectionally Arrayed Chopped Strand (UACS) introduced into laminate tube. UACS plies with discontinuous angled slit and slit perpendicular to fiber direction, namely bi-angle slits and staggered slits were used as 0˚ ply, respectively, instead of conventional continuous fiber ply to investigate relationship between crashworthiness capacities and progressive collapse behavior under quasi-static crushing tests. Newly designed laminate tube for crashworthy structure made of 0˚ plies UACS bi-angle slits and staggered slit was succesfully enhanced specific energy absorption by about 9.1% and 4.3% respectively compare to conventional continuous fiber laminate tube. The crushed laminate tubes then were sectioned through the impact point and micro-photograph were taken to show the failure behavior, which include effect of distribution slit on delamination, matrix cracking, curvature size, friction, etc. It is shown that UACS laminate beside of showing excellent formability also become newly auto trigger mechanism to achieve much stable and controllable collapse with much extensive fiber fracture occurred.

Abstract: Energy and power capability of a supercapacitor is important because of its function to provide backup power or pulse current in electronic/electric products or systems. The choice of its electrode materials, typically such as carbon, metal oxide or conducting polymer determines the mechanism of its energy storage process. This short review focuses on the supercapacitors using porous carbon electrode prepared, respectively, from fibers of oil palm empty fruit bunches. The specific energy and specific power of these supercapacitors were analyzed to observe their trend of change with respect to the electrode preparation parameters affecting the porosity, structure, surface chemistry and electrical conductivity of electrodes, and thence influence the energy and power capability of a supercapacitor. This review found that the trend of change in specific energy and specific power was not in favor of the expectation that both the specific energy and specific power should be in increasing trend with a significant progress.

Abstract: An investigation was undertaken to explore the grinding characteristics in grinding of yttrium vanadata (YVO4) crystal by using a resin diamond wheel. The grinding forces and surface roughness were measured and the morphological features of ground workpiece surfaces were examined. The results indicate that the depth of cut is the leading factor in affecting grinding forces whereas the surface roughness is mainly governed by the grinding speed. The material removal mechanism was found to be dominated by brittle fracture mode at conventional grinding speeds, and gradually transfer to ductile flow mode under higher grinding speeds, which is greatly related to the maximum undeformed chip thickness.

Abstract: In present paper, a semi-empirical grinding force model is developed combined with the achievements of previous researchers by composing effects of normal and tangential grinding forces in two main parts respectively: cutting force and sliding force. Final equations for the total normal and tangential force components is established. This model is used to predict the total normal and tangential force in the surface grinding. These force components were expressed in terms of the grinding process parameters. There are four unknown coefficients in each equation which can be determined by experiment results at specific conditions with the variations of grinding process parameters. An equation for sliding force is established with the effect of specific sliding energy in terms of the experimental parameters. The average contact pressure and friction coefficient are taken into account. Four different water-based grinding fluids were tested for different specific grinding conditions. Low viscosity grinding fluid can have better performance than the high viscosity one due to the higher useful flow in the grinding contact area. The calculated normal and tangential grinding results are compared with the experimental ones. The verifications show that deviations can be affected by the performance of the fluid at heavy grinding conditions due to the sliding friction inside of rolling friction. To have a better agreement with experiment data. Shallow grinding condition is chosen to obtain the modified model.

Abstract: Impregnated diamond core bits are often used in core drilling for geological surveys. A tri-state theory is proposed to describe the three states in drilling processes for a diamond particle or a bit. These states are contacting state, cutting state, and ploughing state. Furthermore, the relations among thrust and other mechanical parameters are also summarized. The optimal value of the specific energy is in the cutting state. Several experiment results verified the proposed model. This mechanism is useful for selecting operation parameters in core drilling using impregnated diamond core bits.

Abstract: The breadmaking process can be defined by the succession of operations with operating conditions as input variables and dough properties as output ones, any output variable at step i being an input at step i+1. In this paper, we strive to show how the main properties of bread, density, porosity and alveolar structure (crumb), can be predicted from basic knowledge models (BKMs). So we have defined the variables of breadmaking, proposed BKMs for the two first operations, mixing and proofing, and underlined the needs to define them for shaping and baking, after a short review of existing models. The specific energy delivered during mixing is determined by a simple balance equation in order to predict gluten structuration and dough viscosity, the main output of mixing operation. Then an analysis of dough proofing at different structural scales, by rheology and imaging, allows to assess its alveolar structure, and to fit the kinetics of porosity and stability by phenomenological models. Finally we show how these BKMs could be integrated in order to help the design of baked products with target properties.

Abstract: Grinding is one of the most difficult processes in machining operations. Normally, the flood coolant method was used as a cooling agent in the grinding process. The most common defects using flood coolant are higher grinding friction, higher heat generation, and thermal damage. Therefore, the minimum quality lubricant (MQL) was introduced to minimize the defects. The main objective of this project is to compare the performance of MQL and flood coolant techniques in terms of grinding temperature, grinding force and specific energy. Three levels of cutting speeds, three levels of feed rate and depth of cut are adopted in the evaluation. The experiments were conducted on a thin plate of mild steel AISI 1020. The result shows that the MQL technique was effectively supplied to the grinding contact zone. This research revealed that the MQL technique exhibited an advantages on the surface temperature compared to the flood coolant.