Reduction In Heat Transfer Rate Research Articles

WITHDRAWN: The enhanced heat transfer and flow dynamics of tangent hyperbolic and Newtonian nanofluids under inclined variable magnetic field

This paper aims to analyze the thermal conductivity of tangent hyperbolic non-Newtonian fluids and Newtonian nanofluids over a porous, inclined, stretching sheet with motile microorganisms. It also examines the impact of inclined variable magnetic field, activation energy, thermal radiation, thermophoresis and Brownian motion. The novelty of this research lies in the simultaneous use of inclined geometry and an inclined variable magnetic field. The findings optimize environmental and food processing applications, drug delivery, thermal management, lubrication, and enhanced oil recovery. A far-reaching analysis compares the behaviors of tangent hyperbolic fluid with Newtonian fluid. Appropriate similarity functions are used to convert the governing system of nonlinear PDEs for tangent hyperbolic fluid to dimensionless ODE. MATLAB’s boundary value solver BVP4C is then used to solve these ODEs numerically. This study explores various characteristics, including temperature, velocity, concentration, and microorganism distribution. In the essence of this computational study, the impacts of inclined angle, porosity, mixed convection, Hartmann number and Weissenberg number on the velocity of the fluid are analyzed. The main findings are that higher Prandtl numbers reduce heat transfer rates, while thermophoresis and Brownian motion enhance heat flow. Lewis and Peclet numbers show declining tendencies in motile microorganisms, with magnetic fields influencing their distribution within the fluid; this is useful in biotechnology and environmental applications. Consequently, the effect is greater in the case of non-Newtonian fluids which depend more on the inclination angle, inclined variable magnetic field strength, thermal conductivity and activation energy when compared with the Newtonian fluids.

Effect of Water-based Alumina-Copper MHD Hybrid Nanofluid on a Power-Law Form Stretching/Shrinking Sheet with Joule Heating and Slip condition: Dual Solutions Study

The application of hybrid nanofluid is now being employed to augment the efficiency of heat transfer rates. A numerical study was conducted to investigate the flow characteristics of water-based-alumina copper hybrid nanofluids towards a power-law form stretching/shrinking sheet. This study also considered the influence of magnetic, Joule heating, and thermal slip parameters. This study is significant because it advances our understanding of hybrid nanofluids in the presence of magnetic fields, power-law form stretching/shrinking sheet, and heat transfer mechanisms, providing valuable insights for optimizing and innovating thermal management systems in various industrial applications such as polymers, biological fluids, and manufacturing processes like extrusion, plastic and metal forming, and coating processes. The main objective of this study is to examine the impact of specific attributes, including suction and thermal slip parameters on temperature and velocity profiles. In addition, this exploration examined the reduced skin friction and reduced heat transfer in relation to the solid volume fraction copper and magnetic effects on shrinkage sheet and thermal slip parameter on suction effect. To facilitate the conversion of a nonlinear partial differential equation into a collection of ordinary differential equations, it is necessary to incorporate suitable similarity variables into the transformation procedure. The MATLAB bvp4c solver application is utilized in the conclusion process to solve ordinary differential equations. No solution was found in the sort of when , and . As the intensity of the Eckert number increases, the temperature profile and boundary layer thickness also increase. The reduced heat transfer rate upsurged in both solutions for solid volume fraction copper for shrinking sheet, while the opposite actions can be noticed in both solutions for thermal slip parameter for suction effect. Finally, the study conducted an analysis to identify two distinct solutions for shrinking sheet and suction zone, while considering different parameter values for the copper volume fractions, magnetic and thermal slip condition effect.

Assessing the Efficacy of Hybrid Nanofluid within a Non-Newtonian Reiner-Philippoff Model, Incorporating MHD and Thermal Radiation Past a Stretching/Shrinking Sheet

Hybrid nanofluids are making waves in industry because of their superior thermal efficiency and innovative designs. Their usefulness extends to many other sectors and domains of study. The volume fraction of Cu–Al2O3 and Ag–TiO2 hybrid nanoparticles in nanofluids will be studied to determine their impact on heat transmission and flow. The study also considers the presence of heat radiation, a magnetic field, and other relevant factors. The non-Newtonian Reiner-Philippoff model was employed to investigate the flow's shear thickening and thinning properties. The combined effects of suction and a contracting surface form a boundary for the surface. The reduced partial differential equation (PDE) is solved using the MATLAB tool bvp4c following the similarity transformation method. The shrinking sheet shows that the dual solution converges to critical points, and the stability study verified that the first one is stable and physically trustworthy. The mathematical modelling developed for nanofluid hybrids has exhibited a significant impact on the overall heat flow, which can be attributed to the variation in the parameters that influence it. Enhancement in magnetic parameter (+2.26%), suction (+2.99%), and nanoparticle fractional volume of metal oxide (+0.4%) were identified as factors that accelerated heat transfer to the pioneering Cu–Al2O3 nanofluid hybrid, according to the study. Besides, the second hybrid of Ag–TiO2 nanofluids had a reduced heat transfer rate due to changes in thermal radiation (-2.14%) and Reiner parameter-Philippoff fluid (-0.14%).

Characterization of aloe vera gel incorporated unsaturated polyester resin jute-cotton fabric composites for enhanced biodegradability, flexibility, and insulation properties

In this research, Aloe Vera Gel (AVG) was incorporated into Unsaturated Polyester Resin (UPR) with jute-cotton union fabric to fabricate partially biodegradable composites. These composites were fabricated using a hand lay-up technique and characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry Analysis (TGA), thermal conductivity measurements, water absorption tests, degradation assessments, cracking tests, and Universal Testing Machine (UTM) analysis. The study found that increasing the percentage of AVG in the composites led to a decrease in thermal conductivity, indicating improved insulation properties. Samples reinforced with AVG showed enhanced resistance to damage from iron nails, with reduced scratching and fiber displacement observed. However, the addition of AVG resulted in decreased thermal, mechanical, and water resistance properties compared to composites without AVG. FTIR analysis demonstrated interactions between AVG and the matrix materials. In degradation tests, composites subjected to an alkali environment (PH = 11.96) showed the highest weight reduction (2.22 %) compared to those without AVG. Similarly, composites buried in soil exhibited greater weight loss (2.38 %) than their counterparts lacking AVG. Overall, the developed composite's reduced heat transfer rate suggests its potential application as an insulating material in environments such as rural poultry housing and the automotive industry.

Intelligent computing for the electro-osmotically modulated peristaltic pumping of blood-based nanofluid

The study delves into a novel application of artificial neural networks within the biomedical realm, specifically focusing on the peristaltic pumping of ionized blood-infused nanofluid using the Casson model. The investigation takes into account the impacts of electrokinetic forces, chemical reaction, thermal radiation and variable thermal conductivity. The endorsed nanofluid model encompasses both thermophoretic and Brownian diffusions. The Nernst-Planck and Poisson equations are used to characterize electroosmotic process. The mathematical model is then numerically solved using NDSolve in Mathematica. The variation in relevant hemodynamic characteristics concerning key flow parameters is explored through numerous graphical representations. Two distinct artificial neural networks have been developed to estimate values for rates of mass and heat transfer. The Levenberg-Marquardt algorithm is used as the training algorithm in network models with multi-layer perceptron architecture. Graphical inspection of the results demonstrates a decrease in blood flow with an elevated Helmholtz-Smoluchowski velocity. A lower pressure gradient is recorded with a higher electroosmotic parameter. Furthermore, an augmentation in the thermal conductivity parameter leads to a reduction in heat transfer rate at the wall. The concentration profile demonstrates an increase with a rise in the chemical reaction parameter. The results obtained from the neural network models exhibit an ideal harmony with the target values. The developed neural network models demonstrated the ability to predict rates of heat and mass transfer values with average deviations of −0.01% and 0.004%, respectively.

Optimizing of a metal foam-assisted solar air heater performance: a thermo-hydraulic analysis of porous insert placement.

A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( ), pore densities ( ), and Reynolds numbers ( ) at a fixed value of layer thickness ( ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for at . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel's potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with , for , and .

Frosting characteristics of microchannel heat exchangers: Parametric studies and correlation development

Recently, microchannel heat exchangers (MCHX) have been widely used in heat pump systems due to their high surface-to-volume ratio and high efficiency of heat transfer. However, when the MCHX operates in frosting conditions, its performance is adversely affected. To study the frost formation and distribution characteristics of MCHX, a comprehensive parametric study was performed for the MCHX with a larger fin pitch. The effects of fin geometries and environmental parameters on the frosting characteristics of MCHX were studied. Fin height (Fh) can effectively inhibit frost formation, which is due to the increase of surface temperature with the increase of Fh. When Fh increased from 6.0 mm to 11.8 mm, the frost time increased by 30.5 %. However, the increase in Fh also brings the penalty of reduced heat transfer rate. The effect of fin depth (Fd) on frost formation performance is small because the frost is mainly deposited in the front part, resulting in the rear fin cannot work efficiently. Fin pitch (Fp) is the most significant structural parameter affecting frosting performance. When Fp increases from 1.6 mm to 4 mm, the frosting time increases by 4 times and frost mass increased by 2.2 times. This is because with the increase of Fp, the frost blocking in the front part can be effectively delayed, and the distribution uniformity of the frost layer is improved. Lower surface temperature and higher humidity ratio significantly promote frost formation and reduce the uniformity of frost distribution. When the inlet temperature is reduced from −5 °C to −8 °C, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 55.7 %. When the relative humidity increases from 76 % to 92 %, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 42.5 %. The air velocity has a minor impact on the growth rate of frost in the front part. However, as the air velocity increases, the uniformity of frost distribution is significantly improved. When the air velocity increased from 1.1 m s−1 to 2.2 m s−1, the mass of accumulated frost increased by 29.5 %. Furthermore, frost thickness and air-side heat transfer coefficient correlations were developed by testing 12 samples. The developed heat transfer coefficient correlation can accurately capture the changing trend of the j-factor. This study provides a fundamental understanding of the frosting characteristics of MCHX and can effectively guide the louvered fin optimization.

Influence of porosity properties on natural convection heat transfer in porous square cavity

A numerical investigation was conducted to examine free convection heat transfer within a square cavity containing a fluid-saturated porous layer at the bottom under laminar flow conditions. The enclosure's left and right walls experienced heating and cooling, while the top and bottom walls remained adiabatic. The study explored the influence of the Darcy number, porosity number, and dimensionless thickness of the porous layer on heat transmission. This investigation utilized a FORTRAN computation program alongside the finite volume method, effectively solving the equations governing flow and heat exchange within porous materials through natural convection. The flow pattern is determined by the Navier–Stokes equations in the fluid region and the Darcy–Brinkman–Forchheimer formula in the porous region. The energy equation was employed to compute the thermal field. The increase in the Darcy number results in both an increase in heat transfer rate due to enhanced fluid flow through pores and an intensification of fluid flow patterns. Higher porosity leads to higher heat transfer rates due to greater fluid penetration and an increased surface area for heat exchange. The thicker porous layer reduces heat transfer rate due to increased resistance to fluid flow and decreased contact area.

FEM study of blood gold electrically conducting micropolar nanofluid flow within a permeable channel

In this work, Hermite interpolation polynomials are utilized to develop a numerical model to analyze the influence of transport phenomena on blood gold electrically conducting micropolar nanofluid within a permeable channel with chemical reaction and thermal radiation. By considering blood as a micropolar fluid and applying Berman’s similarity transformation the resulting governing equations are transmuted to fourth-order nonlinear ODE which are solved utilizing FEM. The validity of the FEM code is established by comparing the present computations with existing work. Further, the influence of driving parameters are studied and graphically depicted. When utilizing a blood-gold micropolar nanofluid with a 1% volume fraction, it is observed that varying the Hartmann number from 0 to 15 leads to a decline in temperature profiles, resulting in a 2.51% reduction in heat transfer rate. Similarly, an increase in the chemical reaction parameter up to 10 causes species concentration profiles to decrease, leading to an 18.25% reduction in mass transfer rate compared to base fluid. Moreover, an increase in the volume fraction up to 5% results in an increase in coefficient of skin friction under the influence of the Hartmann number. These findings signify the critical role of Hartmann number in controlling blood velocity and chemical reaction parameter assists in lowering the species concentration levels. The results of the present investigation may help analyze flow models related to drug-delivery systems as gold nanoparticles are proficient drug-delivery and drug-carrying medium.

Effect of operating regimes on the heat transfer and buoyancy characteristics of supercritical CO2 natural circulation loop - A numerical study

At present, 82% of global energy is generated by fossil fuels which produce substantial emissions and have a significant impact on the environment. Heat transfer devices play a vital role in enhancing the efficiency of power generation systems and mitigating environmental impact. Among various heat transfer devices, natural circulation loops (NCLs) assume significance due to their simplicity and safety. In the present study, numerical investigations were conducted on three-dimensional rectangular circular cross-section supercritical CO2-based NCL across three distinct operating regimes. These regions include the average temperature of NCL maintained near the widom line (near pseudo-critical region), away from the widom line (higher buoyancy region) and very far away from the widom line (deeply supercritical region). The results indicate that in all regions, there is an increase in both the mass flow rate and heat transfer rate as pressure increases. At a pressure of 14 MPa, the maximum heat transfer rate across all regions is observed. Although the higher buoyancy region exhibits a superior heat transfer rate, the near pseudo-critical region demonstrates efficient heat transfer capabilities. For example, at 11 MPa, the temperature difference in the higher buoyancy region exceeds that in the near pseudo-critical region by 73%. However, the reduction in heat transfer rate in the near pseudo-critical region is only 37% compared to the higher buoyancy regions. For low-temperature applications, the near pseudo-critical region effectively transfers heat. However, in high-temperature applications, the sink temperature should be kept in the liquid-like region to maximize system buoyancy.

Natural Convection Around Three Horizontal Cylinders in Vertical Array: A Numerical Approach

The present numerical study explores the flow physics and heat transfer characteristics around three unconfined inline horizontally placed cylinders arranged in a vertical array subjected to ambient air. It investigates the effect of Rayleigh number (i.e., 102 ≤ Ra ≤ 106) and the center-to-center spacing (1≤ S/D ≤ 9). The study shows that the augmentation or reduction of heat transfer rate from an individual cylinder in the array to that of a single unconfined cylinder under identical conditions strongly depends on the separation distance and Rayleigh number. Moreover, the average Nu from the bottom cylinder deteriorates only at very close spacing, whereas after S/D ≥ 3, it attains an asymptotic value to that of a single cylinder. The heat transfer rates from the middle and top cylinders relative to a single cylinder also deteriorate drastically at close spacing. In contrast, a slight enhancement is observed at relatively large spacing and higher Ra.

Entropy generation for thermo-magnetic fractional order convective flow in complex porous enclosures: a numerical study

PurposeThis study aims to analyze the impact of fractional derivatives on heat transfer and entropy generation during transient free convection inside various complex porous enclosures, such as triangle, L-shape and square-containing wavy surfaces. These porous enclosures are saturated with Cu-water nanofluid and subjected to the influence of a uniform magnetic field.Design/methodology/approachIn the present study, Darcy’s model is used for the momentum transport equation in the porous matrix. Additionally, the Caputo time fractional derivative is introduced in the energy equation to assess the heat transfer phenomenon. Furthermore, the total entropy generation has been computed by combining the entropy generation due to fluid friction (Sff), heat transfer (Sht) and magnetic field (Smf). The complete mathematical model is further simulated using the penalty finite element method, and the Caputo time derivative term is approximated using the L1 scheme. The study is conducted for various ranges of the Rayleigh number (102≤Ra≤104), Hartmann number (0≤Ha≤20) and fractional order parameter (0<α<1) with respect to time.FindingsIt has been observed that the fractional order parameter α governs the characteristics of entropy generation and heat transfer within the selected range of parameters. The Bejan number associated with heat transfer (Beht), fluid friction (Beff) and magnetic field (Bemf) further demonstrate the dominance of flow irreversibilities. It becomes evident that the initial evolution state of streamlines, isotherms and local entropy varies according to the choice of α. Additionally, increasing Ra values from 102 to 104 shows that the heat transfer rate increases by 123.8% for a square wavy enclosure, 7.4% for a triangle enclosure and 69.6% for an L-shape enclosure. Moreover, an increase in the value of Ha leads to a reduction in heat transfer rates and entropy generation. In this case, Bemf→1 shows the dominance of the magnetic field irreversibility in the total entropy generation.Practical implicationsRecently, fractional-order models have been widely used to express numerous physical phenomena, such as anomalous diffusion and dispersion in complex viscoelastic porous media. These models offer a more accurate representation of physical reality that classical models fail to capture; this is why they find a broad range of applications in science and engineering.Originality/valueThe fractional derivative model is used to illustrate the flow pattern, heat transfer and entropy-generating characteristics under the influence of a magnetic field. Furthermore, to the best of the author’s knowledge, a fractional-derivative-based mathematical model for the entropy generation phenomenon in complex porous enclosures has not been previously developed or studied.

Effect of the Non-Linear Radiative Unsteady Mixed Convective Flow over a Curved Stretching Surface with Soret and Dufour Effects: A Numerical Study

The subject of unsteady convective flow with non-linear thermal radiation has become an important issue of research, due to its implications in advanced energy conversion systems operating at high temperature, solar energy technology and chemical process at high operation temperature. Due to the importance of this issue, a time dependent incompressible viscous fluid flow, heat and mass transfer over a curved stretching surface has been numerically analysed by taking into account the heat flux due to concentration gradient and mass flux due to temperature gradient. Together with this the Rosseland approximation is being employed for the nonlinear thermal radiation impact in presence of thermal slip. With the aid of non-dimensional variables and the corresponding physical boundary conditions, the leading nonlinear momentum, energy, and species equations are converted into a set of coupled ordinary differential equations. These equations are then resolved using the MATLAB bvp4c solver. The stability of the numerical technique has been verified and compared with available literatures. The resultant parameters of engineering interest and the boundary layer flow field parameters and have been presented using tables and graphically plots. The study concludes that for lesser curvature parameter (0.5≤K≤0.7) the surface drag force, heat and mass transfer rates can improve by about 9.59%, 2.87% and 1.67% each respectively. The presence of the temperature ratio parameter and the non-linear thermal radiation are found to greatly influence the temperature profile and the heat transfer rate of the system. Results show that the heat transfer rate improves by about 24.39% and 16.66% for varying non-linear thermal radiation (1≤Rd≤1.5) and temperature ratio parameter (1.2≤θw≤1.4) respectively. Results obtained also show that improving the thermal slip parameter (0.4≤L≤0.6) can reduce heat transfer rate by about 13.62% and reduce the surface temperature profile.

Three-dimensional transient CFD modeling of multiple finned aluminum foam heat sinks in a horizontal channel

Finned metal foam heat sinks are well-known because of their excellent performance in cooling of powered electronics. In this study, three-dimensional transient numerical simulations of finned aluminum foam heat sinks in a forced convection of air were carried out using commercial COMSOL. The geometry under consideration consists of an array of finned aluminum foam heat sinks mounted on heater blocks and placed on a plate in a horizontal channel. Heat sink aluminum foam regions were considered as porous media with a local non-equilibrium thermal model to evaluate thermal characteristics, while the Forchheimer-Brinkman extended Darcy model is considered for the flow analysis. Our main concern in the present study is to evaluate the transient thermal–hydraulic behavior and the cooling performance under constant flux heat sources while varying the Reynolds number and variable morphological parameters of the aluminum foam, i.e., porosity (ε) varied from 0.85 to 0.95. The thermal performance ratio and the average Nusselt number of the finned aluminum foam heat sinks are 23.14% and 30%, respectively, larger than the finned aluminum heat sinks. As the Reynolds number increases, the thermal characteristics are enhanced, and the pressure drop is increased. An increase in porosity causes a reduction in heat transfer rate and an elevation of pressure drop.

Heat transfer analysis of buoyancy opposing radiated flow of alumina nanoparticles scattered in water-based fluid past a vertical cylinder

Cooling and heating are two critical processes in the transportation and manufacturing industries. Fluid solutions containing metal nanoparticles have higher thermal conductivity than conventional fluids, allowing for more effective cooling. Thus, the current paper is a comparative exploration of the time-independent buoyancy opposing and heat transfer flow of alumina nanoparticles scattered in water as a regular fluid induced via a vertical cylinder with mutual effect of stagnation-point and radiation. Based on some reasonable assumptions, the model of nonlinear equations is developed and then tackled numerically employing the built-in bvp4c MATLAB solver. The impacts of assorted control parameters on gradients are investigated. The outcomes divulge that the aspect of friction factor and heat transport upsurge by incorporating alumina nanoparticles. The involvement of the radiation parameter shows an increasing tendency in the heat transfer rate, resulting in an enhancement in thermal flow efficacy. In addition, the temperature distribution uplifts due to radiation and curvature parameters. It is discerned that the branch of dual outcomes exists in the opposing flow case. Moreover, for higher values of the nanoparticle volume fraction, the reduced shear stress and the reduced heat transfer rate increased respectively by almost 1.30% and 0.0031% for the solution of the first branch, while nearly 1.24%, and 3.13% for the lower branch solution.

Numerical investigation of thermo-hydraulic ability of STHX with continuous helical baffles on the shell side

The larger quantities of heat transfer rates are possible with the modification of few parameters like baffle cut and shape. Which significantly improves the performance of shell and tube heat exchanger while reducing the pressure drop. From the reported literature review it was proposed to carry the numerical analysis for various helix angles. The present study is to simulate heat transfer rate and liquid movement in a shell-and-tube heat exchanger along with continuous helical-baffles on the shell side. The numerical investigation of seven helix angles, namely 10°, 19°, 21°, 25°, 30°, 38°, and 50°, is done for varying mass flow rates and the inlet temperature of shell side and tube side are 25 °C and 55 °C respectively, modelled a whole length unceasing helical-baffled shell-and-tube heat exchanger. Larger helix angles (30°, 38°, and 50°) result in reduced heat transfer rate and pressure drop too low, while minor helix angles (10°, 19°, 21°, and 25°) result in increased heat transfer rate and pressure drop too high.

Multiscale Superhydrophobic Zeolitic Imidazolate Framework Coating for Static and Dynamic Anti‐Icing Purposes

AbstractIce formation is a major challenge for engineering systems. Superhydrophobic surfaces constitute an effective approach to address this challenge. However, in addition to complex preparation methods, surface texture‐ and chemistry‐related shortcomings reduce their effectiveness. In this study, a functionalized metal–organic framework (ZIF‐8) based micro‐nano‐subnano scale coating (SuperHydrophobic Multiscale Coating – SHMC) with CA (contact angle) &gt; 172°, rolling angle &lt; 5°, and CAH (contact angle hysteresis) &lt; 3° is developed and applied to metallic surfaces by spray coating. A fractal theory‐based model of contact angle is adapted to reveal its non‐wetting mechanism. SHMC extends the icing time by at least 300% and maintains its superhydrophobicity for &gt; 30 icing/deicing cycles. The generated capillary pressure ranges within the multiscale coating are studied. The three‐phase contact line characteristics including contact times, contact diameters, and interfacial heat transfer during droplet impact are assessed. A numerical model is developed using dynamic contact angle physics for transient heat transfer during the impact. Compared to the plain surface, which leads to instant icing at 60 ms after impact, no icing is observed on the developed coating. At least an order of magnitude reduction in heat transfer rate during the droplet contact time is obtained with SHMC.

MHD Mixed Convection Flow of Hybrid Ferrofluid through Stagnation-Point over the Nonlinearly Moving Surface with Convective Boundary Condition, Viscous Dissipation, and Joule Heating Effects

This paper discusses a numerical study performed in analysing the performance regarding the magnetic effect on the mixed convection stagnation-point flow of hybrid ferrofluid, examining the influence of viscous dissipation, convective boundary condition as well as Joule heating across a nonlinearly moving surface. Additionally, the hybrid ferrofluid exhibits an asymmetric flow pattern due to the buoyancy force affecting the flow. Water H2O is employed as the base fluid collectively with the mixtures of nanoparticles containing magnetite Fe3O4 and cobalt ferrite CoFe2O4, forming a hybrid ferrofluid. The partial differential equation’s complexity is reduced by similarity transformation into a system of ordinary differential equations, which are then numerically solved by applying the MATLAB function bvp4c for a specific range of values regarding the governing parameters. Dual solutions were identified under both opposing and assisting flow conditions, and the stability analysis identified that the first solution was stable. Furthermore, it was also revealed that the addition of 1% CoFe2O4 in hybrid ferrofluid led to a higher skin friction coefficient between 3.35% and 7.18% for both assisting and opposing flow regions. Additionally, the growth of magnetic fields results in a reduced heat transfer rate between 8.75% to 10.65%, whilst the presence of the suction parameter expands the range of solutions, which then delays the boundary layer separation. With the Eckert number included, the heat transfer rate continuously declined between 7.27% to 10.24%. However, it increased by about 280.64% until 280.98% as the Biot number increased.

Investigation of thermal behavior and performance of different microchannels: A case study for traditional and Manifold Microchannels

In this study, numerical investigation of forced convection of non-Newtonian nanofluid into Traditional Microchannel (TMC) and Manifold Microchannel (MMC) containing porous media is investigated. The bottom of the microchannel wall is kept at a constant temperature and the other walls are heat insulated. The inside of the microchannel is filled with porous media. This study addresses a new sample of microchannels (MMC and TMC) filled with porous material in a three-dimensional flow. The results show that increasing the Reynolds number and volume fraction of nanoparticles (φ) and decreasing the porosity, lead to heat transfer improvement. At low Reynolds numbers, there is no relative advantage over TMC or MMC. Finally, it is concluded that to achieve the acceptable performance evaluation criterion PEC (PEC> 1) at porosity ε= 0.9, thermal conductivity ratio (γ) must be γ <0.9. When thermal conductivity of porous foam is considered low, PEC variations and heat transfer rates in the traditional microchannel are uniform. For TMC and MMC in the maximum Reynolds number, the percentage of increase in heat transfer at ε= 0.9 compared to the absence of porous material is 13.5% and 26.26%, respectively. For MMC and TMC in minimum permeability and maximum Reynolds number, the percentage of reduction of heat transfer rate from n = 0.5 to n = 1.5 is equal to 0.86% and 0.37%, respectively.

Mixed convection MHD boundary layer flow, heat, and mass transfer past an exponential stretching sheet in porous medium with temperature-dependent fluid properties

The mixed convection MHD boundary layer flow, heat and mass transfer of a Newtonian fluid mixture across an exponentially stretched permeable sheet in porous medium with Soret and Dufour effects subject to temperature-dependent fluid properties have been investigated numerically. The distribution of temperature and concentration at the surface is supposed to grow exponentially. Temperature is considered to affect fluid viscosity and thermal conductivity. The guiding partial differential equations with appropriate boundary conditions are converted into coupled, nonlinear ordinary differential equations with variable coefficients via a similarity transformation. Matlab's built in solver bvp4c is used to find numerical solutions. Using a graphical approach, the effects of several emerging physical parameters on velocity, temperature and concentration distributions on a flow field of a chemically nonreacting fluid mixture are examined and discussed. Results are compared to earlier literature available and found to be in good agreement. Furthermore, this research demonstrates that flow, heat and mass transmission are greatly influenced by mixed convection parameters, magnetic field, Prandtl number, viscosity, conductivity, permeability, and Schmidt number. Skin friction grows for mixed convection parameter, magnetic, viscosity. Highest growths of wall temperature and wall concentration gradients are observed for Prandtl number and Schmidt number, respectively. HIGHLIGHTS Heat and mass transfer rates increase with higher values of mixed convection parameters and Darcy parameter. To reduce heat transfer rate magnetic field may be used. Fluid with lower thermal conductivity and with higher Prandtl number may be employed to boost the cooling rate in conducting flows. Higher Schmidt enhances mass transfer rates. Suction stabilizes boundary layer growth. Soret effect can be used to separate light and medium molecular weight components from a fluid mixture and hence can be used for control of air pollution.