Journal of Heat and Mass Transfer Research
Volume:10 Issue: 2, Summer-Autumn 2023

The effect of chemical reaction and external vertical magnetic field on the onset of the double diffusive convection in couple stress fluid between infinite horizontal parallel plates  has been studied.  The effectiveness of vertical magnetic field and chemical reaction were gauged by determining the values of  Chandrashekhar number (Q) and Damk hler number  in terms of other controlling parameters and shown their effect on stability of system through graphs. The entire investigation is performed in two parts: linear and weakly non-linear stability analysis. A comparative study is presented in stationary case of linear stability analysis for four types of bounding surfaces: (a) Realistic bounding surfaces i.e. Rigid-Rigid, Rigid-Free and Free-Rigid (R/R, R/F and F/R) (b) Non Realistic bounding surface i.e. Free-Free (F/F). However, oscillatory case and weakly non-linear stability analysis are restricted for Free-Free (F/F) boundary surfaces. Graphical representations are used to illustrate how different parameters affect stationary, oscillatory, finite-amplitude states and  the amount of heat and mass transfer. By analysing the linear stability analysis, it is observed that the onset of convection is more dominant in oscillatory case than stationary. The stability criteria for Q came out as (in decreasing order) F/F>F/R>R/R>R/F which is different from the criteria came out for rest of the controlling parameters i.e F/R>R/R>F/F>R/F in stationary case. It is also reported that the Q, Couple stress parameter (C) and ratio of heat capacities on heat transfer  is responsible for the delay of the onset of convection while  (impact of chemical reaction) enhances the onset of convection. Non-linear stability analysis using the truncated representation of Fourier series method predicts the occurrence of sub-critical instability in the form of finite amplitude motion. The effect of Q, Lewis number Le, and solute Rayleigh number RaS, increased the amount of heat and mass transfer while C decreased. We also draw streamlines, isotherms, isohalines and magnetic streamlines for different time intervals (unsteady) i.e. for (0.01, 0.03, 0.009, 0.006) and showed the pattern of the onset of convection.

In Senegal, biomass fuels and more specifically pellets from agricultural residues have attracted interest in recent years. These fuels are eco-friendly materials and represent a better alternative to domestic fuels such as charcoal or firewood due to their availability at local scale associated to their relative uniformity (standard size, possible formulation of several residues, higher energetic density with respect to firewood). In the present work, we produced and characterized 6 mm diameter pellets from residues of groundnut shell, corn cob, palm nut shell and typha both in pure form or blended from two different residues. The characterizations of these pellets showed that the pelletizing of biomass residues makes it possible to significantly increase the Lower Heating Value (LHV) of single pellets. The mixture of different agricultural residues makes it possible to have a much higher heating value, with pellets with LHV greater than 19 MJ/kg. We also highlight the importance of the pelletizing process in reducing the ash content for blended pellets; the opposite phenomenon is observed for single pellets. Our work also shows the importance of pelletizing and blending of agricultural residues in reducing the formation of bottom ash and corrosion.

The aim of this work is to numerically and theoretically model thermosolute natural convection in porous, isotropic and saturated media filled with Casson nanofluids (aluminum nanoparticles) under the influence of a magnetic field. Calculations were performed for various parameters relevant to our model, namely Casson fluid parameters (between 0.1 and 1), thermal Rayleigh number (between 10 and 100000), Geometric aspect ratio number (between 1 and 3),Buoyancy ratio number (between 1 and 10), Soret and Dufour numbers (between 0.2 and 1.2), conductivity ratios (between 1 and 3) and Hartmann numbers (between 0 and 100). The horizontal walls of the enclosure maintain uniform temperature and concentration, while the side walls are rigid, watertight, and insulated. Casson nanofluid flow occurs in porous layers and is described by the extended Darcy law of Brinkman-Forchheimer. The finite volume method was used to spatially discretize the obtained system of equations. Therefore, we investigated the effect of different parameters on the heat transfer rate and concentration. we observe that heat and mass transfer increases with increasing Casson fluid parameter; this increase is significant for the case of β between 0.1 and 0.4. And it also increases with the increase in the number of thermal conductivity ratios, the number of thrust ratios and with the increase in the thermal Rayleigh number. The latter remain unchanged when the thermal Rayleigh number is below the threshold     . In the Opposite, we notice an uneven decrease in the thermosolutal transfer with the increase in the Hartmann Soret and Dufour numbers.

It has been explored the unsteady MHD convection flows during loosely packed permeable media into a precipitately starting perpendicular plate by the changeable temperature as well as mass transportation. The temperature of the plate rises linearly over time. The fluid taken is as gray engrossing, or emitted and radiating but the non-scattering media. The governing equations of the current investigation are resolved by the Laplace transformation methodology. The velocity, temperature, as well as concentration, are found systematically and numerically explored for various governing parameters. Also, the skin friction, Nusselt number, and Sherwood numbers by the combinations of distinct flow parameters are demonstrated in graphical profiles, as well as physical features of the problem are explored. It is found that the magnitude of the velocity is increased by enhancement into the quantities of penetrability parameter. The magnitude of the velocity is enhanced as it trims down incessantly by increasing into the radiating parameter. The velocity increases over time. The magnitude of the velocity is decreased by an increase in the Prandtl number. The temperature is reduced by an increase in the radiating parameters and/or Prandtl numbers. The growing quantities of the Schmidt number led to the concentration profile complete liquid area. Nusselt number is growing by increasing into radiating parameter and Prandtl number.

In this review, a quantitative research survey has been carried out on the peristaltic motion of Carreau fluid (CF), one of the most important generalized Newtonian fluids. This work primarily focuses on the fluid's diverse behavior as a result of the application of various methods and the broad overview of peristaltic Carreau fluids in a range of impacts such as Heat and Mass Transfer, Magnetohydrodynamic (MHD), stagnation point, stretching and shrinking sheet, porous medium and boundary layer. The various approaches that have been explored to depict this exquisite physiological transport system, which is frequently seen in nature, are summarized in this paper. The extensive study of biofluid peristaltic pumping pertaining to its importance in various fields, perspectives, and mathematical models is also discussed in depth. This analysis compares the major components and research results over the last 50 years and offers recommendations for future advancement. Researchers can use this analysis as a platform for building peristaltic transport for various applications.

The current article studies the impact of radiation absorption and diffusion thermo effect or the Dufour effect on a convective MHD flow of a rotating fluid past through a moving vertical isothermal plate under thermal radiation, chemical reaction, and heat source. The equations that govern the flow, are transformed into dimensionless ordinary differential equations(ODEs), which are then solved analytically using the perturbation technique. The pertinent results obtained are illustrated graphically for the various relevant thermophysical parameters involved in the problem. Additionally, we have listed the numerical values showing the changes in the viscous drag, rate of heat transfer and mass transfer rate through tables. In the investigation, we observe that the velocity of the fluid accelerates for increasing Dufour number, radiation absorption, and heat source parameter. On the other hand, the velocity retards due to rotation and chemical reaction parameters. The momentum transfer rate upgrades for the Dufour number and radiation absorption parameter.

Channel flow with baffles is a multifaceted phenomenon with wide-ranging applications. It plays a crucial role in enhancing mixing, heat transfer, and other fluid dynamics processes. The baffles' design and placement within the channel are crucial to achieving the desired heat transfer enhancement. Based on the specific application and fluid properties, such as baffle geometry, spacing, and orientation must be considered. This work aims to visualize, evaluate, and understand the effectiveness of baffles on heat transfer rates under various operating conditions and design parameters.  Computational Fluid Dynamic (CFD) investigations were carried out to examine the performance of channels for various geometrical configurations including Broken V-shaped, Circular, and triangular at wide operating conditions, and baffle number densities. Computational fluid dynamic (CFD) simulations were carried out for three different baffle shapes while the Reynolds number (Re) ranged from 1800 to 22000 and the no. of baffle sets(N), varied as N=15,20,30. At low Re conditions channel with 30 sets of Broken-V-shape baffles results in a higher Nusselt number due to effective turbulence enhancement and mixing in the channel. Although the thermal performance of a V-shaped baffles case is relatively good the friction factor is more for this case. Triangular baffles exhibited a lower friction factor. A maximum friction factor of 0.92 is observed for N=30 sets at Re= 1800 while the least of 0.76 is recorded for N=15.

To address radiative heat transfer problems, the determination of view factors is crucial. In this study, the focus is placed on the calculation of the view factor using the Monte Carlo method, specifically for truncated cone radiators. Although reference books offer theoretical relations for computing the view factor, a new approach employing the Monte Carlo method is utilized to ensure the accuracy of the general solution. To measure the accuracy, three types of cases are considered: positive, negative, and zero-angle truncated cones with a fixed disk (ring) at the base of the cone. The results are presented for various ratios between the height of the truncated cone and the radii of the ring and base side of the cone. Additionally, the impact of different angles of the truncated cone on the view factor is investigated. In the zero-angle case, five different L/r1 are examined, in the positive angle case, seven different positive angles in two different L/r1 are studied, and in the negative angle case, three negative angles in three different L/r1 are studied. For positive angles, the maximum difference between the results of Monte Carlo method and theoretical method is 42.81% and occurred in L/r1 equal to 5 and 40 degrees. While for zero-angle the maximum difference is 30.16% and occurred in L/r1 equal to 10. In the negative angle case, the maximum difference is 36.66% and occurred in L/r1 equal to 0.2 and -15 degrees.

In the present paper, natural convection of non-Newtonian hybrid Cu-Al2O3 nanofluid in an inclined partial porous cavity with changing heated wall position was numerically investigated. At first, the governing equations are rewritten non-dimensionally by utilizing dimensionless parameters. Then, the entropy generation equations are expressed in non-dimensional form. The discretization of governing equations is done by CVFVM (Control Volume Finite Volume Method). The coupling between pressure and velocity is handled by SIMPLE method and the obtained algebraic equations are computed by SIP solver. Nu number and irreversibility of flow and heat transfer are examined by main parameters such as Ha number, Da number, porosity, porous media thickness, position of heated wall, power law index and angle of inclination. Nu number increases almost 39%, 50% and 52% with enhancing porous media thickness from 0.1 to 0.6 at inclination angle of -30o, 0o and 30o, respectively. The Nu number increases by setting the hot surface at the lower part of the cavity. Nu decreases almost 10.5%, 7.6% and 5.2% by augmentation of Ha number from 0.0 to 40.0 at viscosity power law index of 0.6, 1.0 and 1.4, respectively. Nu increases almost 36%, 47% and 53% at inclination angle of 30o, 0o and ‒30o by enhancing volume fraction from 0.02 to 0.12, respectively. Convection heat transfer and fluid flow will be more dominant by augmentation of permeability and Da number and this will lead to more entropy generation by fluid flow and less entropy generation and irreversibility by magnetic field and convective heat transfer process. Fluid flow and magnetic field entropy generation decrease and heat transfer irreversibility and Be number rises by porous thickness ratio. Be number and thermal entropy generation increases with porosity. However, irreversibility due to magnetic field and flow friction decreases.

The application of simulation-based software is the current trend in technology to predict the behaviour of complex phenomena. The combustion process and emissions exertion process of internal combustion engines are critical and complex processes. An attempt has been made to conduct a comparative analysis of combustion, performance, and emissions parameters by the application of "Diesel R K software in the current work. A single-cylinder, diesel engine is used here which is powered by different blends of diesel-biodiesel. In this study Soybean, Karanja, and roselle feedstocks are used as biodiesel. A comparative study was conducted on parameters like rise in cylinder pressure, rate of heat release, exhaust gas temperature, BSFC, ITE, and emission parameters like BSN, carbon dioxide, nitrogen oxides, particulate matter, and smoke opacity. As the blend percentage increased, the highest cylinder pressure moved close to the top dead center (TDC). EGT, BSFC increases and ITE slightly decreases as the amount of SME, KB, and LA in blended increase. All of the SME, KB, and LA blends are discovered to emit more NOx than diesel. SME20, SME100, KB20, KB100, LA20, and LA100 all produced less smoke than diesel fuel by 43.51%, 60.60%, 48.32%, 59.54%, 44.66%, and 62.56%. 852.25 g/kWh respectively. KB100 omits the highest CO2 emission of all the fuels. LA20 emitted the lowest specific particulate matter emission at 0.058 g.KW/hr. The optimal ratio that offers the finest results in terms of performance and emissions with biodiesel is LA20.

This article explains the MHD Casson nanofluid flow in the presence of chemical reaction coefficient past a linear stretching surface along with the slip condition. Mainly, the analysis of heat and mass transfer in the presence of Brownian motion and the thermophoretic diffusion effect is performed. Mathematical modeling for the law of conservation of mass, momentum, hear and concentration of nanoparticles is executed. Governing nonlinear partial differential equations are transformed into the dimensionless nonlinear ordinary differential equations by using appropriate transformations. To achieve numerical solution for the considered model, shooting technique and Adams-Moulton method of fourth order are used to obtain the numerical results via the computational program language FORTRAN. Comparison between the obtained results and previous works are well in agreement was observed. For the velocity, temperature, and concentration profiles, numerical computations are conducted. The effects slip parameter, velocity ratio parameter, Casson parameter, Casson parameter taken the problem. Numerical values of the local skin-friction, Nusselt number and nanoparticle Sherwood number are computed and analyzed. It is noted that the skin-friction coefficient decreases for the larger values of velocity ratio parameter, slip parameter, and increases with an increasing value of Casson parameter. It is also found that enhancing the chemical reaction parameter leads to decrease in concentration profile. In addition, physical quantities of absorption like skin friction, local Nusselt and Sherwood numbers are also shown graphically.

An analysis has been performed to study the problem of the thermal performance of a continuously moving convective-radiative rod with variable thermal conductivity. Highly accurate semi-analytical methods called the least Square method (LSM) and the Galerkin method (GM) are introduced and then used to obtain a nonlinear temperature distribution equation in a fin that allows for more accurate measurements that could make the investigation stand out. This research investigated the influence of various parameters on heat transfer in a continuously moving convective-radiative rod. The parameters examined include the convective-conductive factor (Ncc), dimensionless thermal conductivity coefficients (a), radiative-conductive parameter (Nrc), Peclet number (Pe), dimensionless convective (θc), and radiative sink temperatures (θr). An increase in the dimensionless thermal conductivity coefficient (a) led to higher dimensionless temperatures within the rod, indicating an amplification of conductive heat transfer. The convective-conductive parameter (Ncc) demonstrated a direct relationship with heat loss. In contrast, the radiative-conductive parameter (Nrc) exhibited an inverse relationship between radiative heat transfer and local temperature within the fin. A rise in the Peclet number was associated with higher dimensionless temperatures, indicating a faster-moving rod. Additionally, variations in dimensionless convective and radiative sink temperatures affected temperature profiles, with higher sink temperatures resulting in increased dimensionless temperatures. Notably, the dimensionless radiative sink temperature was found to have a more significant impact on overall dimensionless temperature than the convective sink temperature. These findings underscore the intricate interplay of factors governing heat transfer and temperature distribution in the moving rod system. The importance of this work lies in its comprehensive analysis of the intricate interplay of parameters affecting heat transfer and temperature distribution in continuously moving convective-radiative rods, providing valuable insights for optimizing industrial processes and engineering applications.