• Energy Research

L'objectif de cette étude est d'évaluer la qualité du sol pour l'environnement en termes de modèles de distribution spatiale de certains éléments sélectionnés tels que le pH, l'azote total (N2), le soufre (S), le potassium (K), le phosphore (P), le fer (Fe) et l'arsenic (As) dans 42 échantillons de sol de surface et de sous-surface. Ces échantillons ont été prélevés à différents endroits autour des stocks de charbon de Tamabil, Sylhet. Cependant, principalement les échantillons de sol prélevés ont été testés en laboratoire. Par conséquent, ces données ont été calculées et justifiées dans le cadre d'approches statistiques multivariées, par exemple la matrice de corrélation, la composante principale et l'analyse factorielle. Les sols examinés ont montré une grande variabilité dans les concentrations d'éléments, en particulier dans le cas du pH et du soufre. Les principales analyses en composantes et en facteurs ont montré que la variance totale du sol de surface est de 79,89 % alors qu'elle est de 80,99 % pour le sol souterrain. Ce résultat suggère que l'interaction sol - charbon avec l'impact anthropique est le facteur dominant pour affecter la qualité du sol. La matrice de corrélation du sol de surface et du sol souterrain, d'où il est clair qu'il n'y a pas de paramètres, n'est ni fortement corrélée positivement ni négativement corrélée l'une avec l'autre. Cela implique que la source hétérogène de différentes composantes du sol et la variabilité ionique possible peuvent provenir de sources anthropiques multiples. À la fin, sur la base de la présente analyse, la qualité du sol de la zone d'étude devient acide. Si des précautions ne sont pas prises immédiatement, les personnes et les autres organismes vivants seront confrontés à des difficultés. Par conséquent, une zone particulière doit être utilisée pour le stockage du charbon, et il doit y avoir une barrière appropriée afin que le charbon ne puisse pas se mélanger avec le sol et l'eau environnants de l'environnement. Par conséquent, il sera utile d'éviter la dégradation de l'environnement. El objetivo de este estudio es evaluar la calidad del suelo para el medio ambiente en términos de los patrones de distribución espacial de algunos elementos seleccionados como el pH, nitrógeno total (N2), azufre (S), potasio (K), fósforo (P), hierro (Fe) y arsénico (As) en 42 muestras de suelo superficiales y subsuperficiales. Estas muestras se recolectaron de diferentes ubicaciones alrededor de las reservas de carbón de Tamabil, Sylhet. Sin embargo, principalmente las muestras de suelo recolectadas se analizaron en el laboratorio. En consecuencia, estos datos se calcularon y justificaron bajo enfoques estadísticos multivariados, por ejemplo, matriz de correlación, componente principal y análisis factorial. Los suelos examinados mostraron una alta variabilidad en las concentraciones de elementos, especialmente en el caso del pH y el azufre. Los principales análisis de componentes y factores reflejaron que la varianza total del suelo superficial es del 79.89%, mientras que es del 80.99% para el suelo subsuperficial. Este resultado sugiere que la interacción suelo-carbón con el impacto antropogénico son los factores dominantes que afectan la calidad del suelo. La matriz de correlación del suelo superficial y subsuperficial, de donde se desprende que no hay parámetros que no estén fuertemente correlacionados positivamente ni negativamente correlacionados entre sí. Implica que la fuente heterogénea de diferentes componentes del suelo y la posible variabilidad iónica pueden ser aportadas por múltiples fuentes antropogénicas. Al final con base en el presente análisis, la calidad del suelo del área de estudio se está volviendo ácida. Si no se toman precauciones de inmediato, las personas y otros organismos vivos enfrentarán dificultades. Por lo tanto, se debe usar un área en particular para el lugar de almacenamiento de carbón, y debe haber una barrera adecuada para que el carbón no pueda mezclarse con el suelo y el agua circundantes del medio ambiente. En consecuencia, será útil prevenir la degradación del medio ambiente. The aim of this study is to evaluate the quality of soil for environment in terms of the spatial distribution patterns of some selected elements such as pH, total nitrogen (N2), sulfur (S), potassium (K), phosphorus (P), iron (Fe), and arsenic (As) in 42 surface and sub-surface soil samples. These samples were collected from different locations around the coal stockpiles of Tamabil, Sylhet. However, primarily the collected soil samples were tested in the laboratory. Consequently, these data were computed and justified under multivariate statistical approaches for example correlation matrix, principal component, and factor analysis. The examined soils showed a high variability in the element concentrations especially in the case of pH and sulfur. The principal component and factor analyses reflected that the total variance of surface soil is 79.89% whereas it is 80.99% for subsurface soil. This result suggests that the soil-coal interaction with anthropogenic impact is the dominant factors for affecting the soil quality. The correlation matrix of surface and subsurface soil, from where it is cleared that there is no parameters are neither strongly positively correlated nor negatively correlated with each other. It implies that the heterogeneous source of different components of soil and possible ionic variability may be contributed from multiple anthropogenic sources. At the end based on the present analysis, the soil quality of the study area is becoming acidic. If precautions are not taken immediately, the people and other living organisms will face difficulties. Therefore, a particular area should be used for coal stocking place, and there should be a proper barrier so that coal can't mixed with the surrounding soil and water of the environment. Consequently, it will be helpful to prevent the degradation of the environment. تهدف هذه الدراسة إلى تقييم جودة التربة للبيئة من حيث أنماط التوزيع المكاني لبعض العناصر المختارة مثل الأس الهيدروجيني والنيتروجين الكلي (N2) والكبريت (S) والبوتاسيوم (K) والفوسفور (P) والحديد (Fe) والزرنيخ (As) في 42 عينة من التربة السطحية وتحت السطحية. تم جمع هذه العينات من مواقع مختلفة حول مخزونات الفحم في تامابيل وسيلهيت. ومع ذلك، تم في المقام الأول اختبار عينات التربة التي تم جمعها في المختبر. وبالتالي، تم حساب هذه البيانات وتبريرها بموجب مناهج إحصائية متعددة المتغيرات على سبيل المثال مصفوفة الارتباط والمكون الرئيسي وتحليل العوامل. أظهرت التربة التي تم فحصها تباينًا كبيرًا في تركيزات العناصر خاصة في حالة الأس الهيدروجيني والكبريت. عكست تحليلات المكونات والعوامل الرئيسية أن التباين الكلي للتربة السطحية هو 79.89 ٪ في حين أنه 80.99 ٪ للتربة تحت السطحية. تشير هذه النتيجة إلى أن تفاعل التربة والفحم مع التأثير البشري هو العوامل السائدة للتأثير على جودة التربة. إن مصفوفة الارتباط للتربة السطحية والجوفية، حيث يتضح أنه لا توجد معلمات، لا ترتبط ارتباطًا إيجابيًا قويًا ولا ترتبط ارتباطًا سلبيًا ببعضها البعض. وهذا يعني أن المصدر غير المتجانس للمكونات المختلفة للتربة والتغير الأيوني المحتمل يمكن أن يساهم فيه العديد من المصادر البشرية. في النهاية بناءً على التحليل الحالي، أصبحت جودة التربة في منطقة الدراسة حمضية. إذا لم يتم اتخاذ الاحتياطات على الفور، سيواجه الناس والكائنات الحية الأخرى صعوبات. لذلك، يجب استخدام منطقة معينة لمكان تخزين الفحم، ويجب أن يكون هناك حاجز مناسب بحيث لا يمكن خلط الفحم مع التربة والمياه المحيطة بالبيئة. وبالتالي، سيكون من المفيد منع تدهور البيئة.

An enclosure with a moving lid is commonly used in heat and mass transmission. Also, many investigations have been done so far on a mixed convective flow in a cavity, but no research has been done to observe the low Reynolds number effect in the presence of MHD and radiation in a cavity with a semi-circular heater incorporated kerosine oil-based CNT nanofluid. In addition, oil-based nanofluid makes the working fluid more stable at a higher temperature. This study numerically investigates the time-dependent effect of low Reynolds number on Kerosene oil-based CNT nanofluid with magnetic field and radiation. The governing equations were employed with the finite element method based Galerkin residual technique. Brownian motion of nanoparticles was considered to determine the thermal conductivity and dynamic viscosity. Lower values of Reynolds number are taken, such as 50 to 200 with fixed values of radiation parameter, the particle concentration, the Hartmann number, and the Richardson number. The results were illustrated as heat transfer and fluid flow for three dimensionless time conditions. Results indicate that increasing the fluid velocity improves the Nusselt number and drag force. The vorticity rises to 54% while increasing the fluid velocity, however, the pressure gradient and average temperature become lower. It is also found that the average fluid velocity is 2.2 times higher in the Re = 50 than in the Re = 100. For the time dependency of this study, the thermo-hydrodynamics behavior changes with dimensionless time. Finally, this study would be a guide for designing thermal devices related to heat transfer, especially using the Kerosene oil-based CNT nanofluid under different conditions.

Abstract A computational numerical work has been done to see the effects of magnetic field on natural convection for a trapezoidal enclosure. Both inclined walls and bottom wall have constant temperature where the bottom wall temperature is higher than the inclined walls. Top wall of the cavity is adiabatic. To investigate the effects, finite element method is used to solve the governing equations for different parameters such as Rayleigh number, Hartmann number and inclination angle of inclined wall of the enclosure. It is found that heat transfer decreased by 20.70% and 16.15% as φ increases from 0 to 60 at Ra = 105 and 106 respectively. On the other hand, heat transfer decreased by 20.28% and 13.42% as Ha increases from 0 to 50 for Ra = 105 and 106 respectively.

Nanomaterial flow has fascinated the concern of scientists across the globe due to its innovative applications in various manufacturing, industrial, and engineering domains. Bearing aforementioned uses in mind, the focal point of this study is to examine the Carreau nanofluid flow configured by the Riga surface with Arrhenius catalysts. Microorganisms are also suspended in nanofluid to strengthen the density of the regular fluid. Time-dependent coupled partial differential equations that represent the flow dynamics are modified into dimensionless patterns via appropriate non-dimensional variables, and handled through an explicit finite difference approach with stability appraisal. The performances of multiple flow variables are examined graphically and numerically. Representation of 3D surface and contour plots for heat transportation and entropy generation are also epitomized. The findings express that the modified Hartmann number strengthens the motion of nanomaterial. Reverse outcomes for heat transport rate and entropy are seen for the radiation variable. Concentration diminishes for chemical reaction variable. Activation energy enhances the concentration of nanomaterial, whereas reduction happens in the movement of microbes for bio-Lewis number. Greater Brinkman variable heightens the entropy.

Recently scientists used nanoparticles in refrigeration systems because of theirs remarkable improvement in thermo-physical, and heat transfer capabilities to enhance the efficiency and reliability of refrigeration and air conditioning system. In this paper thermal–physical properties of nanoparticles suspended in refrigerant and lubricating oil of refrigerating systems were reviewed. Heat transfer performance of different nanorefrigerants with varying concentrations was reviewed and review results are presented as well. Pressure drop and pumping power of a refrigeration system with nanorefrigerants were obtained from different sources and reported in this review. Along with these, pool boiling heat transfer performance of CNT refrigerant was reported. Moreover, challenges and future direction of nanofluids/nanorefrigerants have been reviewed and presented in this paper. Based on results available in the literatures, it has been found that nanorefrigerants have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional refrigerant. This can be considered as one of the key parameters for enhanced performance for refrigeration and air conditioning systems. Because of its superior thermal performances, latest upto date literatures on this property has been summarized and presented in this paper as well. The results indicate that HFC134a and mineral oil with TiO2 nanoparticles works normally and safely in the refrigerator with better performance. The energy consumption of the HFC134a refrigerant using mineral oil and nanoparticles mixture as lubricant saved 26.1% energy with 0.1% mass fraction TiO2 nanoparticles compared to the HFC134a and POE oil system. It was identified that fundamental properties (i.e. density, specific heat capacity, and surface tension) of nanorefrigerants were not experimentally determined yet. It may be noted as well that few barriers and challenges those have been identified in this review must be addressed carefully before it can be fully implemented in refrigeration and air conditioning systems.

Abstract The effect of thermal conductivity of the absorber plate of a solar collector on the performance of a thermo-siphon solar water heater is found by using the alternative simulation system. The system is assumed to be supplied of hot water at 50 °C and 80 °C whereas both are used in domestic and industrial purposes, respectively. According to the Rand distribution profile 50, 125 and 250 l of hot water are consumed daily. The condition shows that the annual solar fraction of the planning functions and the collector's configuration factors are strongly dependent on the thermal conductivity for its lower values. The less dependence is observed beyond a thermal conductivity of 50 W/m °C for the solar improper fraction and above 100 W/m °C for the configuration factors. In addition, the number of air ducts and total mass flow rate are taken to show that higher collector efficiency is obtained under the suitable designing and operating parameters. Different heat transfer mechanisms, adding natural convection, vapor boiling, cell nucleus boiling and film wise condensation is observed in the thermo-siphon solar water heater with various solar radiations. From this study, it is found that the solar water heater with a siphon system achieves system characteristic efficiency of 18% higher than that of the conventional system by reducing heat loss for the thermo-siphon solar water heater.

Unsteady natural convection heat transfer in an isosceles triangu- lar enclosure filled with Al2O3 nanoparticle is studied by using finite element method. The bottom of the isosceles triangular cav- ity is heated non-uniformly and temperature of the inclined wall is lower than that of the bottom wall. The governing parameters are Rayleigh number, solid volume fraction, aspect ratio (H/L )o f the enclosure and dimensionless-time. It is found that addition of the nanoparticle into base fluid (water) affects both heat transfer and fluid flow. Heat transfer increases with addition of nanoparticle and increasing of Rayleigh number. Conduction mode of heat transfer becomes dominant for the lower values of aspect ratio.

This ongoing study is carried out to analyze the thermal performance with sensitivity study of a mixed convective hexagonal heat exchanger containing TiO2–H2O nanofluid. Magnetic force is regarded to be horizontal while all surrounding walls are adiabatic. The finite element method is used to simulate the regulatory equations. For the first time, response surface methodology is used to analyze the sensitivity of independent factors on a hexagonal heat exchanger. The findings are depicted for four parameters, Reynolds number (10 ≤ Re ≤ 200), Richardson number (0.01 ≤ Ri ≤ 10), Hartmann number (0 ≤ Ha ≤ 100), and nanoparticle volume fraction (0 ≤ φ ≤ 0.1) against velocity distribution, average Nusselt number (Nuav), streamlines, isotherm lines, and heatlines. The results indicate that the growing value of Re and φ strengthen the thermal performance of nanofluid whereas increasing Ha causes it to decrease. Moreover, φ and Re have positive sensitivity to the Nuav while Ha has negative sensitivity. When Ha is maintained at 0, the optimal value of Nuav reaches when Re = 200 and φ = 0.1. The use of TiO2–H2O nanofluid improves the water's heat transmission ability to 17.69%. Finally, the results of this study may offer advice for creating an effective mixed convective heat exchanger.