Mixed Convection Heat Research Articles

Temperature, Velocity and Pressure Gradient Distribution of Oil Production in South West Cameroon using a Mixed Convection Heat Transfer in a Horizontal Tube

Temperature, Velocity and Pressure Gradient Distribution of Oil Production in South West Cameroon using a Mixed Convection Heat Transfer in a Horizontal Tube

MHD mixed convection flow for Maxwell Hybrid nanofluid with Soret, Dufour and Morphology effects

We have investigated the two-dimensional mixed convective Maxwell hybrid nanofluid boundary layer mass and heat flows over a linearly stretching porous surface with the applied external magnetic flux. Thermal radiations along with the Dufour and Soret effects are also incorporated. The governing model of partial differential equations (PDE) is altered into ordinary differential equations (ODE) with an appropriate similarity transformation. The finite difference-based numerical method BVP4c is applied to solve the system of nonlinear ODEs. The flow features and the heat transfer characteristics have been illustrated with graphical representations and a numerical table. For varied values of the flow-related variables, organized and graphical data for the Nusselt number and skin friction coefficient are indicated. In most cases, spherical-shaped nanoparticles have a better influence on stream function, velocity and temperature distributions. This behavior is the opposite of the mass concentration profile. It has been observed that stream function decreases as increase the value of the magnetic field but opposite for mass concentration distribution and temperature profile. The temperature gradient is enhanced as a result of stronger convective flow when Soret number Sr values increase, which causes the boundary layer thickness to grow. A comparative study of hybrid nanofluid and nanofluid showed that the hybrid nanofluid has superior shear stress/skin friction and Sherwood number/surface mass flux than nanofluid flow.

Combined effect of annular space and rotation on heat transfer from concentric cylinders

Numerical simulations are carried out to understand the thermofluidic behaviour around the annular gap between a pair of vertical co-axial revolving cylinders suspended in quiescent air within the laminar regime. A detailed mixed convection heat transfer analysis is elucidated by varying various relevant pertinent parameters, such as, Rayleigh number 103≤Ra≤106, Reynolds number 0≤Re≤600, and annular gap 0.05≤Rg/L≤1. The cooling rate from individual walls is predicted thoroughly. The increasing gradient of heat transfer is comparatively sharp on the outer wall of outer cylinder compared to other walls. Enhancement of heat transfer rates from wall of inner cylinder and inner surface of outer cylinder is relatively lower at lower value of Rg/L in spite of the presence of rotation of cylinders. Lastly, velocity vectors are employed to describe the fluidic behaviour around the annular gap for both cases of Re≠0 and Re=0.

Numerical investigation with sensitivity study of MHD mixed convective hexagonal heat exchanger using TiO2–H2O nanofluid

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.

Significance of mixed convective heat transfer model in an equilateral triangular enclosure subjected to cylindrical heated objects inside

This analysis articulately presents the impact of heat transfer along with associated characteristics inside an equilateral triangular enclosure. Aiming to focus on the significance of heat transfer, four heaters (w1,w2,w3,w4) and three cold walls (C1,C2,C3) are brought into notice in equilateral enclosure. The bottom wall of the enclosure moves with uniform velocity (U0̄) in its own axis while the inclined and corner cold walls of the enclosure are fixed. The position of heaters is considered in four quadrants of cylindrical wall while the segments are placed at the corners of enclosure. Mathematical expressions are developed for heaters and cold walls. The computational model is considered in two-dimensional triangular domain. Water liquid is treated as a working fluid (Pr=6.9). Buoyancy effect is incorporated into Navier–Stokes equations using Boussinesq estimation. The governing equations are explored numerically by using Finite Volume Method based ANSYS-Fluent implicit solver software. Comparison has been made for the current results with published work in limiting case. Excellent matched has been seen. The findings show that the heat transfer rate is noted maximum in third quadrant of cylindrical wall (w4) when compared with other walls against Reynolds number. The temperature is noted maximum at the top corner near the segment C3 when Reynolds number increases. The results have it possible applications in thermal insulation of buildings, heating and cooling processes in machineries, furnaces and controlling of fire in buildings etc.

Numerical Study of Air Flow and Distribution of Temperature in A Room with Dislocation Ventilation and A Chilled Ceiling

In the present study, numerical analysis has been employed to investigate the distribution of velocity and temperature of the air in space conditioned with corrugated ceiling radiant cooling panels (RCP). The model of the study is a three-dimensional room with dimensions of (5.0*4.0*3.2) m. The initial and boundary conditions of the models are set to start the simulation in which the mean cooling panel temperature (Tmp) is (15 °C), where Tmp must not be lesser than that variety to avoid the danger of water vapor condensation on the surface of panels and tubes. The air inlet temperatures Tin is taken as (15, 20, and 25) °C and inlet velocities Vin are (1 and 0.5) m/s with an outdoor air temperature of (40 °C). Ansys Fluent software is considered in this study to simulate the flow field under the influence of several factors including outdoor air temperature, mean panel temperature, air inlet velocity, and temperature. The outcomes show an improvement in the overall cooling capacity and the mixed convection heat transfer. Many of the calculated outcomes were displayed as velocity vectors and temperature contour diagrams. Numerical studies assist in using the chilled ceiling technique for cooling aims in Iraqi weather for its simplicity, easiness, and better comfort presentation.

Mixed convection Casson polymeric flow from a nonlinear stretching surface with radiative flux and non‐Fourier thermal relaxation effects: Computation with CSNIS

AbstractThermal non‐Newtonian polymer coating flows is growing as a major area in materials processing. Inspired by new developments in this field which require more sophisticated mathematical models, the current investigation examines the laminar viscoplastic boundary layer flow and mixed convective heat transfer over a power‐law nonlinear stretching surface. To simulate thermal relaxation effects the hyperbolic Cattaneo‐Christov heat flux model is deployed. The non‐Newtonian polymer characteristics are described by employing the Casson flow model. High temperature conditions invoke thermal radiation flux which is analyzed with an algebraic flux model. Via robust similarity transformations, the primitive partial differential conservation equations for momentum and energy equations are rendered into a system of coupled non‐linear ordinary differential equations with associated wall and free stream boundary conditions. The emerging boundary value problem is solved numerically with an efficient Chebyshev Spectral Newton Iterative scheme (CSNIS), in the MATLAB platform. The resulting solutions are discussed for different emerging parameters using graphs and tables. Validation is included with special cases from the literature. With increasing power law stretching index increases, the flow is decelerated, and temperatures are reduced. Increment in mixed convection parameter boosts the velocity but suppresses temperature and thermal boundary layer thickness. Increasing non‐Fourier Deborah number, temperatures are depleted whereas with increasing radiative flux parameter they are increased. With elevation in Casson non‐Newtonian parameter, velocity is decreased whereas temperature is enhanced and Nusselt number is suppressed.

Mixed and natural convection heat transfer in a two-dimensional

Mixed and natural convection heat transfer in a two-dimensional

Impact of porosity on two-dimensional unsteady MHD boundary layer heat and mass transfer stagnation point flow with radiation and viscous dissipation

The purpose of the present research is to examine the effect of porosity in the presence of radiation and viscous dissipation on two-dimensional unsteady MHD mixed convection heat and mass transport at the stagnation point. The governing time-dependent nonlinear PDEs are converted into nonlinear ODEs by utilizing similarity transformations. The mathematical formulation is produced as ordinary differential equations. The achieved coupled system has been analyzed using the Keller–Box technique. Newton’s system dictates that the coefficients must be accurate and refined. To assess the influence of flow-controlling factors on relevant profiles, quantitative, and qualitative analysis are conducted. With the use of graphs and tables, beneficial talks were conducted. Under the restricting conditions, prior findings were compared and determined to be satisfactory. The conclusions of this study are widely accepted by the scientific community.

Exploring the Dynamics of Viscous Dissipative Fluid past a Super-hydrophobic Microchannel in the Coexistence of Mixed Convection and Porous Medium

This article investigates the theoretical treatment of mixed convection heat enhancement flow for an electrically-conducting and viscous dissipative fluid traveling vertically through a thermodynamic system where the parallel plates are constantly heated in a slit micro-channel due to mixed convection with porous material. One surface had super-hydrophobic slip and a temperature jump, whereas the other did not. The perturbation technique (semi-analytical method) was employed to solve the nonlinear and coupled leading equations. The results were carefully scrutinized, and the effects of the relevant controlling parameters are shown using different plots. It is concluded from this analysis that the fluid temperature and velocity was found to increase as the viscous dissipation term is increased. Similarly, the function of Darcy porous number is to significantly strengthen the fluid velocity, and these effects are stronger at the heated super-hydrophobic surface, whereas mounting level of magnetic field is seen to drastically weaken the fluid motion in the microchannel. Setting Br and A to zero respectively, Gr/Re=1, and Da to 1000, so that the term 1/Da becomes insignificant, Jha and Gwandu (2017)'s work is retrieved, verifying the accuracy of the current analysis. Further, the outcomes of this research can have possible applications in the lubrication industry and biomedical sciences and has proved very useful to designers in increasing the performance of mechanical systems when viscous dissipation is involved, as well as heat transfer in micro-channels, as it is in combustion.

Simulation of conductive fins effect on mixed convection heat transfer in a two-dimensional inclined channel using the lattice Boltzmann method

The simulation of the laminar mixed convection heat transfer inside a 2-D inclined channel was investigated here by employing the lattice Boltzmann method (LBM). The channel was equipped with conductive fins. The effects of inclination angle (φ), geometrical parameters (e and A), and a wide range of the Richardson numbers (Ri = 0.1-10) at fixed Reynolds number (Re = 100) on the heat transfer and flow structure were studied. The numerical model was validated by the published benchmark problems. Results were analyzed in terms of isotherms, streamlines, average Nusselt number, and average temperature. It found that the Nu increases with a decrease in the number, height, and width of fins. Results showed that when the channel equipped with 16 fins the reduction in Nu value reaches 62% compared to the empty channel. In addition, at Ri = 1 and N = 8, the Nusselt number decreased by about 52-77% for different fin widths compared to the channel without fins. However, the Richardson number and inclination angle enhanced the heat transfer rate in terms of the average Nusselt number. It revealed that a higher heat transfer rate belongs to the Ri = 10 and φ = 60°. The finding of this work showed the capability of LBM in simulating the mixed convection heat transfer in an inclined channel equipped with fins. A numerical analysis of the results produced a comprehensive set of results that could be utilized to reduce heat transfer. This paper can provide a novel framework for the design of air solar collectors and heat exchange systems.

Integrated intelligent neuro computing technique for mixed convective flow and heat transfer in heterogeneous permeability media

This article examines the flow and heat transfer characteristics of variable permeability such as linear, exponential and quadratic permeability functions with Brinkmann–Forchheimer extended Darcy model by utilizing the intelligent computing paradigm via artificial Levenberg–Marquardt back propagated neural networks (ALM – BPNNs). The vertical porous channel walls are considered as electrically conducting and non-conducting. The variable permeability and induced magnetic field effects are significant on flow and heat transfer. To solve the obtained governing equations, finite element method is adopted. It is observed that for the three cases of permeability functions, increase in Hartmann number drops the velocity profile and is accompanied with an increase in the fluid thermal state level. The significance of the Brinkmann number on the fluid temperature in all the cases of permeability indicates a rise in temperature due to increased heat generation. But, the reverse effect is observed when the mixed convection parameter rises, and the boundary layer thickness reduces due to which temperature drops for distinct cases of permeability under consideration. The heat transfer characteristics are analyzed through an artificial neural network and multiple linear regression models. The present work finds its applications in studying packed bed heat exchangers and fixed-bed catalytic reactors.

Numerical investigation on forced, natural, and mixed convective heat transfer of n-decane in laminar flow at supercritical pressures

The present study numerically investigates the forced, natural, and mixed convective heat transfer characteristics of supercritical n-decane in a tube in laminar flow, focusing on the law of mutual coupling of forced and natural convection in mixed convection. Effects of heat flux (100 W/m2–8000 W/m2) and flow direction on heat transfer are investigated. For forced convection, deterioration occurs when the wall temperature reaches the pseudo-critical temperature and the local Nusselt number decreases by up to 17.4% compared to the theoretical value at the heat flux of 2400 W/m2. For natural convection, heat transfer is continuously enhanced with the increase of heat flux. For mixed convection in upward flow, heat transfer is enhanced by the buoyancy of increasing the fluid velocity gradient near the wall. As for the downward flow, buoyancy illustrates the opposite effects. Based on numerical simulation results, the Nusselt number correlations are proposed for forced and natural convection respectively and the correlation for mixed convection is modeled employing a function of the forced and natural convection.

Time-dependent mixed stagnation point hybrid nanofluid flow with radiative heat flux and viscous dissipation effects over a movable EMHD Riga plate

This research communication scrutinizes the time-dependent radiated stagnation point flow by a movable Riga surface in the presence of porous medium, mixed convection, viscous dissipation and radiative heat flux. Both electro-magneto effects are accounted for. The considered flow problem comprises Copper (Cu) as a nanoparticle in a continuous phase fluid water (H2O). The mathematical modeling depends on two main expressions, i.e., momentum equation of Navier-Stokes equation under certain conditions and temperature expression. The coupled system is further simplified via similarity transformations. Computational outcomes are computed by implementing bvp4c technique with the shooting concept. The obtained results are displayed graphically. It is noticed from the computations that both Nusselt number (NN) and skin friction coefficient (SFC) declined subject to increasing estimations of the unsteady variable. The final outcomes and main key points are listed in the conclusion section.

Experimental analysis of electrical field combining nanofluids to enhance the mixed convective heat transfer in the rectangular channel

Owing to the disadvantages of low thermal conductivity and large viscosity, the mixed convective heat transfer efficiency of transformer oil can not meet the cooling demand of transformer. Furthermore, the electrical field force could manipulate the motion of nanoparticles, so as to further strengthen the heat transfer of nanofluids. Therefore, the electrical field and nanofluid are combined in the present study to enhance the thermal performance for cooling transformer. Meanwhile, the effects of electrical field strength, the nanofluid concentration and heat flux on heat transfer as well as mechanism are discussed. Then, a semi empirical correlation is proposed by considering the effects of electrical field and nanoparticles. The result shows that the heat transfer is greatly strengthened up to 65% with the increment of the electrical fields, and there exists an optimal concentration of nanofluid for the best enhanced effect. According to the mechanism analysis, the electrical field force pulls nanoparticles to high potential area and the fluid molecules move with nanoparticles, which impacts the boundary layer. Then, disturbances of nanofluids increase and the boundary layer thickness is decreased. Thus, the boundary layer thickness is reduced and fluid disturbance is strengthened, which significantly enhances heat transfer. Moreover, the predicted values calculated by the semi empirical equations fit the experimental data well.

Insight into the significance of nanoparticle aggregation and non-uniform heat source/sink on titania–ethylene glycol nanofluid flow over a wedge

The properties of nanoparticles in the working fluid are affected by many external factors and it further influences the effective properties of the resulting nanofluid. To study the heat transference mechanism in nanofluids, the inclusion of such factors is quite important as it provides the exact illustration of the mechanism. One such factor is the nanoparticle aggregation effect. Authors have studied the titania–ethylene glycol nanofluid (TiO2/EG NF) flow over a wedge with nanoparticle aggregation effect. Through this communication, authors have attempted to make a development on the Falkner-Skan problem. The flow is developed in the presence of the suction/injection effects, mixed convection, thermal radiation, porous medium, and non-uniform heat source/sink. To account for the influence of nanoparticle aggregation, revised forms of the Maxwell and Bruggeman models and the Krieger-Dougherty model are employed to estimate the effective thermal conductivity and viscosity of TiO2/EG NF, respectively. The aforementioned modified models developed for TiO2/EG NF gave a soundly close agreement with the experimental data. The governing equations are numerically solved employing the “bvp4c function in MATLAB”. The effect of the primary relevant parameters on the velocity, temperature, and heat transmission rate is depicted graphically. The heat transmission rate at the surface is higher with aggregated nanoparticles in comparison to its absence. The higher NPs volume fraction and the aggregation effect enhance the effective viscosity, the fluid becomes denser, and as a result, the velocity decreases. The outcomes of this study will be useful in many fields that utilize applications of flow over wedge such as in raw oil extraction, storage of nuclear waste, insulating heat exchangers, etc.

Comment on the paper “Influence of nanoparticles on the electromagnetic hydrodynamic mixed convection flow and heat transfer of a polymeric FENE-P fluid past a Riga plate in the presence of Arrhenius chemical reaction, Razi Khan, Adeel Ahmad, Journal of Magnetism and Magnetic Materials, 567, (2023), 170352”

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Stability Analysis of Unsteady Mixed Convection Flow Near the Stagnation Point with Buoyancy Effect

This numerical study investigates the behaviour of the unsteady mixed convection flow and heat transfer near the stagnation region past a vertical plate in Al2O3-Cu/H2O hybrid nanofluids. By choosing an appropriate similarity transformation, an ordinary differential equations system is obtained, hence scrutinized via the bvp4c package embedded in the MATLAB program. The results show that as the nanoparticle volume fraction and unsteadiness parameter increase, the fluid's skin friction coefficient also increases. Also, an increase in the nanoparticle volume fraction and unsteadiness parameter has broadened the range of solutions hence, delayed the progress of boundary layer separation. In addition, the presence of the unsteadiness parameter provides a significant result in the thermal system. The first solution is declared stable by the stability analysis.

Mixed Convection in a Horizontal Channel–Cavity Arrangement with Different Heat Source Locations

Several researchers are very interested in mixed convection heat transfer because of how widely it is used, particularly for solar thermal collectors, cooling electronic equipment, and chemical process instruments. Using COMSOL-Multiphysics, this article establishes laminar coupled mixed convection heat transfer characteristics across a horizontal channel–cavity architecture. Investigations are conducted into the effect of heat source location on isotherms, velocity distribution, pressure, temperature, average and local Nusselt numbers, and air density. The intake airflow Reynolds number is assumed constant on 2.8814. The enclosure with an isothermally heated right wall in the shape of a “<” as a heat source in three configurations (heat source in the base (1st case), in the upper step (2nd case), and the below step (3rd case). The obtained numerical results present that the higher heat transfer is performed in case two because the heat source is near the contact surface between the channel and the cavity. With the hot sources’ locations being altered, the velocity distribution seems to be unchanged. The increase in the positive y axis has no impact on the pressure distribution throughout the channel. Changing the position of the heated source does not seem to have any impact on the pressure distribution. Air density profiles start to diverge across cases around y = 0.035 m; the third example has a larger value than the second case, and the latter case has a larger value in the density distribution than the former. The contact between the enclosure and the channel (y = 0), where the greatest Nusselt number also occurs, exhibits the highest heat transfer. The maximal Nusselt number falls as y’s absolute value rises.

Stacked Heterogeneous Ensemble Learning Model in Mixed Convection Heat Transfer from a Vertically Oscillating Flat Plate

In this study, the effects of mixed convection heat transfer from a moving vertical flat plate with an experimental and stacked heterogeneous ensemble learning approach are analyzed. In the experimental work, the effects on both natural and forced convection of dimensionless oscillation amplitude (Ao), dimensionless oscillation frequency (Wo) and Rayleigh number (Ra) are investigated. In the experiments, the vertical movement of the plate is provided by a flywheel-motor assembly. The average Nusselt numbers (Nu) on the fixed plate and the moving plate surface were obtained. Additionally, this study is focused on the prediction of heat transfer of a moving flat plate using single-based algorithms (Gradient Boosting, AdaBoost, Multilayer Per-ceptron) and a stacked heterogeneous ensemble learning model. The statistical per-formance of the single-based algorithms and the stacked ensemble model is meas-ured in the prediction of mixed convection heat transfer. The results show that the stacked-based ensemble learning model yielded the MSE = 2.01, RMSE = 1.42, MAE = 1.1 and R2 = 0.99 values. Overall, this study reveals that the proposed stacked en-semble machine learning model can be used successfully for modeling convection heat transfer of a moving plate.