Numerical Investigation Of Heat And Mass Transfer In Porous Medium Fixed With Various Geometries

Usaha untuk memahami aliran haba dan jisim dalam bahanantara berliang telah meningkat berlipat ganda penydidikam dalam bahanantara berliang telah mengenalpasti beberapa aspek behantara berliang yang menghasilkan banyak penulisan jurnal. Walau bagaimanapun, terdapat banyak ruang yang tidak dapat dijawab berkaitan aliran haba dan jisim dalam bahanantara berliang. Kajian ini telah dejalankan untuk menyiasat pemindahan haba dan jisim dalam bahantara berliang dan meninjau ruang yang masih tidak dapat dijawab. Pelbagai fenomena seperiti pemindahan haba, pemindahan haba dan jisim, kesan disipasi likat, ketidakseimbangan keadaan terma antara fasa cecair dan pepejal bahantara berliang dikaji dengan mangambil kira tiga geometri iaitu bahantara berliang di sepanjang plat menegak, bahantara berliang di dalam ruang dan bahantara berliang dalam silinder menegak. Selian itu, kesan perolakan semulajadi dan sinaran juga diambil kira. The effort to understand the heat and fluid flow behavior inside the porous medium has increased to many folds in the recent few decades. The intensified research in porous medium has generally addressed many aspects of porous medium resulting into enormous number of publications. In spite of the endeavoring effort, there are many gaps left unanswered related to the heat and fluid flow behavior inside the porous medium. The present study is undertaken to investigate the heat and mass transfer in a porous medium and thus explore some of those unanswered areas. The different phenomenon such as, heat transfer, heat and mass transfer, viscous dissipation effect, the thermal non-equilibrium condition between fluid and solid phases of the porous medium are investigated with respect to three basic geometries i.e. porous medium adjacent to a vertical plate, porous medium enclosed in a cavity and porous medium filled in vertical ann~lar cylinder. The combined effect of natural convection and the radiation is investigated in all above mentioned phenomenon

Conjugate heat and mass transfer in square porous cavity

The present article deals with the issue of heat and mass transfer in a square porous cavity having a small solid wall or block inserted at various places at bottom surface. The main objective is to investigate the effect of size of solid wall and its location inside the porous cavity on double diffusive convention. The heat and mass transfer behavior are governed by momentum, energy and concentration equations which are converted into a set of finite element equation with the help of Galerkin method. The left surface of cavity is maintained at higher temperature and concentration, Th and Ch as compared to that of right surface at Tc and Cc. The results are presented in terms of thermal, concentration and fluid flow profiles across the porous cavity

The influence of geometrical shapes of stenosis on the blood flow in stenosed artery

The present work was carried out to investigate the blood flow behavior and the severity of blockage caused in the arterial passage due to the different geometries such as elliptical, trapezium and triangular shapes of stenosis. The study was conducted with respect to various sizes of stenosis in terms of 70%, 80% and 90% area blockage of the arterial blood flow. The study was carried out numerically with the help of advance computational fluid dynamic software. It was found that the shape of the stenosis plays an important role in overall pressure drop across the blockage region of artery. The highest level of pressure drop was observed for trapezoidal shape of stenosis followed by elliptical and then by triangular shaped stenosis. The wall shear stress across the stenosis is great for trapezoidal shape followed by triangular and elliptical stenosis for same blockage area in the artery

Two-phase frictional pressure drop with pure refrigerants in vertical mini/micro-channels

Environmental concerns have urged a search for eco-friendly refrigerants in the refrigeration industry to overcome ozone depletion and global warming problems. Therefore, current research emphasizes frictional pressure drop during flow boiling of environment-friendly refrigerants (GWP\u3c150), isobutane, HFC-152a, HFO-1234yf were tested against commonly reported HFC-134a. The data presented here was collected under heat flux-controlled conditions; the test piece was a round tube (1.60 mm diameter). The data collection was performed at 27 and 32 °C with mass velocities in 50-500 kg/m2s range. Effects of critical controlling parameters, like heat flux, mass velocity, exit vapor quality, operating pressure and medium, were studied in detail. It was observed that pressure drop increases along with mass velocity increment in the test piece and increases with exit vapor quality increment. The same was noticed to decrease with saturation temperature increment. Parametric effects and prediction of assessment methods are reported

Statistical modeling and performance optimization of a two-chamber microbial fuel cell by response surface methodology

Microbial fuel cell, as a promising technology for simultaneous power production and waste treatment, has received a great deal of attention in recent years; however, generation of a relatively low power density is the main limitation towards its commercial application. This study contributes toward the optimization, in terms of maximization, of the power density of a microbial fuel cell by employing response surface methodology, coupled with central composite design. For this optimization study, the interactive effect of three independent parameters, namely (i) acetate concentration in the influent of anodic chamber; (ii) fuel feed flow rate in anodic chamber; and (iii) oxygen concentration in the influent of cathodic chamber, have been analyzed for a two-chamber microbial fuel cell, and the optimum conditions have been identified. The optimum value of power density was observed at an acetate concentration, a fuel feed flow rate, and an oxygen concentration value of 2.60 mol m-3, 0.0 m3, and 1.00 mol m-3, respectively. The results show the achievement of a power density of 3.425 W m-2, which is significant considering the available literature. Additionally, a statistical model has also been developed that correlates the three independent factors to the power density. For this model, R2, adjusted R2, and predicted R2 were 0.839, 0.807, and 0.703, respectively. The fact that there is only a 3.8% error in the actual and adjusted R2 demonstrates that the proposed model is statistically significant

Numerical Analysis of Thermal Non-Equilibrium in Porous Medium Subjected to Internal Heating

Thermal non-equilibrium in porous medium is a prevailing condition when discrepancy of temperature exists between the two phases. The solution of a thermal non-equilibrium model requires that the two heat transport equations corresponding to fluid and solid phases, can be solved separately, which, in turn, provides the information of temperature variations of fluid as well as solid phases of the porous domain. A new method is proposed in the current article to solve the energy equations of the thermal non-equilibrium condition in a porous square cavity. The proposed method is able to predict the thermal equilibrium as well as thermal non-equilibrium accurately. The proposed method is used to investigate the heat transfer through the porous cavity subjected to two different boundary conditions with a heating strip being placed inside the porous cavity. It was found that the new method predicted the heat and fluid flow behavior accurately for the previously mentioned case studies. It is noted that the heat transfer is higher when the heating strip is placed toward the cold surface. The Nusselt number at the bottom of the strip toward the right side is almost 10 times higher than that of the left side of the strip

Feasibility Study of Wind-Diesel Stand-Alone System for a Small Village in India

The finite resources of energy like coal, oil, natural gas etc are depleting day by day. On the other hand man is exploring new ways of utilizing energy and thus total energy requirement of the world is increasing continuously. With the present rate of utilization, the underground deposits of coal, oil and natural gas are expected to last for approximately, 100 years, 50 years and 50 years respectively. To cope up with this problem, concerted efforts to generate renewable energy as an alternate source is increasing rapidly with the passage of time. Among the available renewable resources, solar energy and wind energy are the prime candidates getting attention around the world for power generation. Wind energy is a very good option for power generation but suffers due to variation in wind speed and thus the power contained in the wind, when considered on yearly basis. There are various methods to suppress this drawback of wind energy. One such option is the wind-diesel system. This paper highlights, an analysis of the wind-diesel stand-alone system to meet the complete energy requirement such as house lighting, water pumping, laboratory operations for processing the salt, sealing machine operation etc., of a remotely located community in India.&nbsp

Valorization of spent coffee grounds for biogas production: A circular bioeconomy approach for a biorefinery

© 2022 Elsevier LtdAs a by-product of coffee consumption, millions of tons of spent coffee grounds (SCG) are produced annually. SCG can be recycled in a biorefinery-based process to produce biofuels and value-added products, avoiding the environmental issues, hazardous emissions and costs associated with its disposal. The recycling potential of SCG into biogas by the anaerobic digestion (AD) and co-digestion was reviewed in this work. Such types of review papers are novel and not much work was done on this aspect. The AD of SCG produces 0.500–0.598 m3/kg dry organic matter of biogas with a methane (CH4) concentration of 55–61 %. Nevertheless, the long-term mono-digestion of SCG has been linked with instability and volatile fatty acid (VFA) accumulation. Co-digestion with other waste streams, such as waste activated sludge, food waste and spent tea waste, resulted in the same or larger amounts of CH4 emission. Additionally, the defatted spent coffee grounds (DSCG) have been reported to have advantage over the SCG as the average CH4 yield was 336 ± 7 CH4 mL/g vS compared to 310 ± 2 CH4 mL/g vS from SCG. Additionally, the positive impact of the pretreatment process in increasing the CH4 yield during the AD of the SCG has been observed. Based on the presented work, it is clear that recycling SCG and DSCG is a worthwhile option that can help taxpayers save money on landfill operations and maintenance besides protecting the environment from numerous hazardous emissions. Valorization of biogas products and approaches to enhance the economics of the SCG/DSCG-based biorefinery are indicated in this review as areas where future work in biogas generation from SCG and DSCG can be done. In conclusion, this paper suggests further investigation of the techno-economic analyses and life cycle assessment (LCA) of a biorefinery based on the AD of the SCG and DSCG with other organic waste streams

Operational characteristics optimization of human-computer system

Computer operational parameters are having vital influence on the operators efficiency from readability viewpoint. Four parameters namely font, text/background color, viewing angle and viewing distance are analyzed. The text reading task, in the form of English text, was presented on the computer screen to the participating subjects and their performance, measured in terms of number of words read per minute (NWRPM), was recorded. For the purpose of optimization, the Taguchi method is used to find the optimal parameters to maximize operators’ efficiency for performing readability task. Two levels of each parameter have been considered in this study. An orthogonal array, the signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) were employed to investigate the operators’ performance/efficiency. Results showed that Times Roman font, black text on white background, 40 degree viewing angle and 60 cm viewing distance, the subjects were quite comfortable, efficient and read maximum number of words per minute. Text/background color was dominant parameter with a percentage contribution of 76.18% towards the laid down objective followed by font type at 18.17%, viewing distance 7.04% and viewing angle 0.58%. Experimental results are provided to confirm the effectiveness of this approach

Super Stability of Ag Nanoparticle in Crystalline Lamellar (Lc) Liquid Crystal Matrix at Different pH Environment

The symmetry concept in this paper is related to the natural self-assembly of noble metal nanoparticles in the long range periodic structure of liquid crystal (LC). The current study deliberates the effect of pH on the stability of nanoparticles (NPs) in the lamellar phase of a lyotropic LC environment. The LC was prepared by the mass ratio 0.33:0.22:0.45 for (HDTABr):1-pentanol:water. The LC containing silver nanoparticles (AgNPs) was prepared by replacing the water with Ag solution. The AgNPs were produced by the in situ preparation method in LC. The solution of AgNPs-LC was varied at different pH. The absorption intensities were determined by using ultra-violet spectroscopy (UV-vis). The surface potential and hydrodynamic particle size were determined by using Zeta-potential (measurements). The surface enhanced Raman spectroscopy (SERS) was carried out to enhance the Raman signals of 4-aminobenzenethiol (4-ABT) deposited onto AgNPs as substrate. It is found that all characterizations exhibited super stability for AgNPs dispersed in LC at pH = 3 to 12 with the optimum stability at pH = 5-6. The remarkable stability of NPs is an important indicator of the various applications in nanotechnology and nanoscience fields. © 2019 by the authors