Convective Heat Transfer Flow Research Articles

Influence of solid cylinders on fluid flow and thermal analysis in a curved channel with constant magnetic field

The current study explores the numerical simulation of constant mixed convection heat transfer and fluid flow within a channel, driven by the inlet velocity. The investigation focuses on a curved irregular channel where the presence of three differently sized circular obstacles introduces an unpredictable element to the heat transfer process. For the two-dimensional physical scenario, mathematical equations are formulated to analyze velocity and temperature. Employing appropriate dimensional variables, the coupled partial differential equations are transformed into dimensionless form. Subsequently, the Finite Element Method (FEM) is employed to simulate the results for non-dimensional physical parameters such as Reynolds number, Richardson number, Hartmann number, nanoparticles' volume fraction, and various states of the circular obstacles on heated lines, flow structure, velocities, and temperatures at mean positions generating isotherms, streamlines, velocity, and temperature profiles for various parameter increments. The analysis reveals significant influences of Reynolds number (Re) and heated circular obstacles on the temperature profile, manifesting as heated lines within the system. The analysis brings to light the substantial impacts of nanoparticles on the temperature profile at both the vertical and horizontal mean positions. An elevated Hartmann number signifies a more robust magnetic field than viscous forces. A heightened magnetic field can hinder fluid movement and modify the patterns of heat transfer. Based on the graphical results, we infer that temperature differences tend to arise between strata as the Richardson number increases, leading to a heightened and more evident stratification.

MHD free convective heat and mass transfer flow passing through semi‐infinite plate for Cu‐water and TiO2‐water nanofluids in presence of radiation embedded in porous medium

MHD free convective heat and mass transfer flow passing through semi‐infinite plate for Cu‐water and TiO₂‐water nanofluids in presence of radiation embedded in porous medium

Enhancing Natural Convection Heat Transfer Through Dome-Shaped Nanofluid Enclosures: Two-Phase Simulation Analysis

This study utilizes numerical analysis to investigate laminar flow and natural convective heat transfer of nanofluids (NFs) within dome-shaped enclosures (DSEs). The horizontal walls of the enclosure are adiabatic, while the vertical walls on the right and left are maintained at isothermal conditions with low and high temperatures, respectively. The study focuses on examining the impact of DSEs on flow patterns and natural convection (N.C.) under varying parameters, including Rayleigh numbers (Ra), Lewis numbers (Le), enclosure inclination angles, dome angles, and buoyancy ratio number (Nr). The Prandtl number (Pr) and nanoparticle volume fraction are consistently maintained at 10 and 0.05, respectively. The governing equations have been resolved by applying the Eulerian–Eulerian two-phase model. The study reveals that the DSE significantly influences flow dynamics, leading to smoother circulation patterns that intensify convection currents. This movement of hot fluid toward cooler regions within the enclosure enhances natural convective heat transfer. Across all enclosure inclination angles, the average Nusselt number (Nu) increases with higher Ra, while the Le remains constant at 4. Significantly, due to its robust convective currents, the average Nu in the DSE with a 45° dome angle surpasses those of corresponding square and rectangular enclosures.

Viscous dissipation effect on steady free convective hydromagnetic heat transfer flow of a reactive viscous fluid in a bounded domain

Viscous dissipation effect on steady free convective hydromagnetic heat transfer flow of a reactive viscous fluid in a bounded domain

Performance analysis and optimization of the Gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

Investigation of the effect of geometric configurations on natural convection heat transfer in external flow

AbstractThe complexities of natural convection heat transfer are investigated through experimentation, focusing on the influence of geometric configurations such as spheres, cylinders, and cubes in external flows. The study aims to understand how different geometries affect heat transfer coefficients, providing insights for architectural and engineering applications. Experimental results revealed significant variations in heat transfer efficiency among geometric models, with cubic configurations exhibiting the lowest heat transfer rates compared with spherical and cylindrical counterparts. This underscores the critical impact of geometric configuration on thermal performance and heat dissipation characteristics. The findings highlight the necessity of considering geometric factors in design processes to optimize thermal management strategies. The study contributes to a deeper understanding of convective heat transfer mechanisms, emphasizing the importance of precise geometric modeling in enhancing energy efficiency and sustainability in built environments

Impact of variable electrical conductivity, viscosity on convective heat and mass transfer flow of CuO- and Al2O3-water nanofluids in cylindrical annulus

In the food industry, electrical conductivity is essential for heating processes. The dependence on temperature conductivity of electricity on the outermost layers flow of the nanofluid is the main topic of this paper. Variable electrical conductivity, viscosity, thermo diffusion, thermal radiation and radiation absorption on convective heat and mass transfer flow Cuo and Al2O3-water nano-fluids confined in cylindrical annulus. The non-linear governing equations have been solved by finite element technique with quadratic approximation functions. For various parametric adjustments, the temperature, speed, and nanoconcentration have all been examined. Similar to the cylindrical wall, quantitative evaluations have been made of the surface resistance, temperature rate and mass transport. It is discovered that for both types of nanofluids, a higher thermo-diffusion effect leads to a lower concentration and Sherwood digits on the cylinders. An augment in Q1 enriches the rapidity in CuO-water nanofluidic system as well as decreases in Al2O3-water nanofluidic. Increased Q1 lowers the real temperature and nanoconcentration in both types of nanofluids.

The Lattice Boltzmann Simulation of Free Convection Heat Transfer of a Carbon-Nanotube Nanofluid in a Triangular Cavity with a Solar Heater

In this paper, the flow and free convection heat transfer of a multi-walled carbon nanotube/water nanofluid in a triangular cavity with a solar heater is studied using the lattice Boltzmann method. The side walls of the cavity are cold and the bottom wall is partially heated by a solar heater, which have a non-uniform temperature distribution. It is assumed that the heating energy is provided by an absorber that is directly exposed to sunlight. Because of the limited variations of density, the Boussinesq approximation is used, which causes the coupling of hydrodynamic and thermal fields. For velocity and temperature distribution functions, a lattice Boltzmann model with two dimensions and nine directions is adopted. The effect of parameters, such as the Rayleigh number, the volume fraction of nanoparticles, and the position of solar heater, on the flow and heat fields is studied. The results show that, for all Rayleigh numbers studied, the Nusselt number increases as nanoparticles volume fraction increases. The addition of 4% nanoparticles causes the average Nusselt number to increase about 11% at low (Ra = 103) and moderate (Ra = 104) Rayleigh numbers and 217% at the high Rayleigh number (Ra = 105). Furthermore, it is shown that for a fixed Rayleigh number, heat transfer can be optimized by adjusting solar heater’s position. This study can provide a useful insight for utilizing solar heaters with non-uniform temperature distribution in triangular cavities.

Investigation of Thermo-Hydraulics in a Lid-Driven Square Cavity with a Heated Hemispherical Obstacle at the Bottom.

Lid-driven cavity (LDC) flow is a significant area of study in fluid mechanics due to its common occurrence in engineering challenges. However, using numerical simulations (ANSYS Fluent) to accurately predict fluid flow and mixed convective heat transfer features, incorporating both a moving top wall and a heated hemispherical obstruction at the bottom, has not yet been attempted. This study aims to numerically demonstrate forced convection in a lid-driven square cavity (LDSC) with a moving top wall and a heated hemispherical obstacle at the bottom. The cavity is filled with a Newtonian fluid and subjected to a specific set of velocities (5, 10, 15, and 20 m/s) at the moving wall. The finite volume method is used to solve the governing equations using the Boussinesq approximation and the parallel flow assumption. The impact of various cavity geometries, as well as the influence of the moving top wall on fluid flow and heat transfer within the cavity, are evaluated. The results of this study indicate that the movement of the wall significantly disrupts the flow field inside the cavity, promoting excellent mixing between the flow field below the moving wall and within the cavity. The static pressure exhibits fluctuations, with the highest value observed at the top of the cavity of 1 m width (adjacent to the moving wall) and the lowest at 0.6 m. Furthermore, dynamic pressure experiences a linear increase until reaching its peak at 0.7 m, followed by a steady decrease toward the moving wall. The velocity of the internal surface fluctuates unpredictably along its length while other parameters remain relatively stable.

Computational Fluid Dynamics Heat Transfer Analysis of Double Pipe Heat Exchanger and Flow Characteristics Using Nanofluid TiO2 with Water

A device called a heat exchanger is used to exchange heat transfer between two fluids with different temperatures. Because of its durability and ability to handle high-pressure application, the concentric double pipe heat exchangers are widely utilized for numerous industrial applications. To conserve pumping power energy, many researchers were involved in study of the nanoparticles to be embedded in the fluid, which will enrich the fluid thermal conductivity and surface area. This article demonstrates the flow characteristics and convective heat transfer of nanofluids containing 0.2, 0.4 and 0.6 of vol% TiO2 nanoparticles dispersed in water under turbulent conditions, which mainly can be used for cooling nuclear reactors applications. Reynolds numbers varying from 4000 to 18,000 are examined numerically. The convective heat transfer coefficient results of the nanofluid agree well against experimental data, which are slightly more than that of base water at 1.94%. The results of the numerical model showed that the convective heat transfer coefficient of nanofluids will increase when the Reynolds and volume fraction increases. By increasing the temperature of the annular hot water, the heat transfer rate will increase, showing no major impact to the convective heat transfer coefficient of nanofluids. A generalised solution predicting the convective heat transfer coefficient for extensive nanoparticle materials is proposed. The conclusion of the empirical equation is tested among published data and the results are highly congruent, confirming the strength of the gamma equation.

Analysis of heat transfer in a parallelogram-shaped cavity with porous medium under non-uniform temperature

This study investigates fluid flow and natural convection heat transfer in a parallelogram-shaped cavity with a porous medium under non-uniform temperature condition. The bottom wall is heated with a non-uniform temperature, the side walls are cooled, and the upper wall is adiabatic. The governing equations, along with corresponding boundary conditions, are formulated in dimensionless stream function and vorticity using the extended Darcy model for the porous medium. The equations are solved by employing the finite difference method. The study presents outcomes for isotherms, streamlines, and Nusselt numbers across range of parameters, including the Rayleigh number (104≤Ra≤108), Darcy number (10−1≤Da≤10−6), Prandtl numbers (Pr=0.71,1,7.1), fluid porosity (ϵ=0.8), and inclination angles (30∘≤ϕ≤90∘), about flow and heat transfer characteristics. The results indicate that an increase in Ra, Pr, and ϕ, along with a decrease in Da, leads to an enhancement in the strength of vortexes. It is observed that for constant Ra⁎=RaDa, Rate of heat transfer increases with an increase in Ra and a decrease in Da. The maximum value observed is 10.15. Also rate of Heat transfer increases with the increase in angle and maximum rate of heat transfer is observed at ϕ=90∘.

Optimization and sensitivity analysis of hydromagnetic convective heat transfer in a square cavity filled with a porous medium saturated by Ag-MgO/water hybrid nanofluid using response surface methodology

A computational exploration is presented to emphasis on optimization and sensitivity inspection of the unsteady free convective heat transfer flow of hybrid nanofluid in a square cavity under multidirectional periodic magnetic field with aluminum foam porous medium. The vertical walls of the cavity are maintained at constant low temperature whereas the constant as well as the variable thermal conditions on the bottom wall is considered and the top wall is considered as adiabatic. The finite element technique has been applied to solve the governing equations after changing them into dimensionless form. In the numerical simulations, the Ag-MgO/water hybrid nanofluid has been engaged to gain insight into the flow and thermal arenas. The obtained outcomes are exhibited in terms of streamlines, isotherms and average Nusselt number as well as plotting the response surface and contours. The average Nu is displayed in line graphs, response surface and contours graphs as well as tabular form for different flow parameters. Response surface methodology is applied to achieve an optimization procedure to search for the best situation in which the highest heat transfer rate occurs when the distinct model parameters namely Darcy number, porosity and hybrid nanoparticles volume fraction are treated as the sensitivity of the parameters. A correlation equation between the output response and input variables has been derived with the help of response surface methodology. The magnetic field and its path regime the flow decoration of hybrid nanofluid suggestively. The Ag and Ag-MgO nanomaterial with water flow arenas are compared. While considering Ag-H2O nanofluid, the average Nu increases 23.97 % at Ra = 107 with ϕhnp = 0.02 whereas the corresponding increases is 25.68 % if the Ag-MgO/H2O hybrid nanofluid is taken into account. The average Nu upsurges suggestively, as hybrid nanoparticles volume fraction, period number, magnetic field leaning angle, Darcy number and Rayleigh number rises but porosity and Hartmann number have inverse effect. The outcomes showed that the average Nu is more sensitive to the hybrid nanoparticles volume fraction rather than the porosity or Darcy number. Also, it is discovered that the optimum condition arises at Da = 0.001, ε = 0.2 and ϕhnp = 0.02 with the final Nuave = 2358.21.

Numerical investigation of three-dimensional natural convection heat transfer on corrugated plates of variable height

PurposeThe purpose of this study is to numerically investigate the geometric influence of different corrugation profiles (rectangular, trapezoidal and triangular) of varying heights on the flow and the natural convection heat transfer process over isothermal plates.Design/methodology/approachThis work is an extension and finalization of previous studies of the leading author. The numerical methodology was proposed and experimentally validated in previous studies. Using OpenFOAM® and other free and open-source numerical-computational tools, three-dimensional numerical models were built to simulate the flow and the natural convection heat transfer process over isothermal corrugation plates with variable and constant heights.FindingsThe influence of different geometric arrangements of corrugated plates on the flow and natural convection heat transfer over isothermal plates is investigated. The influence of the height ratio parameter, as well as the resulting concave and convex profiles, on the parameters average Nusselt number, corrected average Nusselt number and convective thermal efficiency gain, is analyzed. It is shown that the total convective heat transfer and the convective thermal efficiency gain increase with the increase of the height ratio. The numerical results confirm previous findings about the predominant effects on the predominant impact of increasing the heat transfer area on the thermal efficiency gain in corrugated surfaces, in contrast to the adverse effects caused on the flow. In corrugations with heights resulting in concave profiles, the geometry with triangular corrugations presented the highest total convection heat transfer, followed by trapezoidal and rectangular. For arrangements with the same area, it was demonstrated that corrugations of constant and variable height are approximately equivalent in terms of natural convection heat transfer.Practical implicationsThe results allowed a better understanding of the flow characteristics and the natural convection heat transfer process over isothermal plates with corrugations of variable height. The advantages of the surfaces studied in terms of increasing convective thermal efficiency were demonstrated, with the potential to be used in cooling systems exclusively by natural convection (or with reduced dependence on forced convection cooling systems), including in technological applications of microelectronics, robotics, internet of things (IoT), artificial intelligence, information technology, industry 4.0, etc.Originality/valueTo the best of the authors’ knowledge, the results presented are new in the scientific literature. Unlike previous studies conducted by the leading author, this analysis specifically analyzed the natural convection phenomenon over plates with variable-height corrugations. The obtained results will contribute to projects to improve and optimize natural convection cooling systems.

Experimental investigation of forced convective heat transfer and fluid flow in a mini heat pipe with rectangular micro grooves

In the present study, the convective heat transfer coefficient of water in a laminar flow regime under constant inlet temperature conditions inside a flat mini heat pipe was investigated ex-perimentally. Heat flux ranged from 20-50W and various horizontal heat sink temperatures (operating temperature) ranged from 15-35°C with liquid flow rate (3.563E-8 m3/sec) used during the experiments. The rectangular microchannels performance is evaluated in terms of the temperature profile, heat transfer coefficient, Nusselt number and thermal resistance. The results emphasized that the mini heat pipe temperature gradients are less than the tempera-ture of the copper plate and the heat resistance gradually decreases to its lowest value when the heat flux value reaches its highest value if it does not exceed the capillary limits. The data also demonstrated that the coefficient of heat transfer in the condensation zone is lower than in the evaporation zone at different heat sink temperatures. The augmentation rate for the flat mini heat pipe thermal conductivity reached about 240% at a heat load 30W for the positions of thermosyphon and horizontal, while the rate of increase in the case of the anti-gravity situ-ation at a heat load 30W reaches 210%, then the improvement percentage begins to decrease to 200%. A generalized regression equation is developed for the estimation of the Nusselt number valid for water in a flat mini heat pipe.

A new detection method of co-existence of well kick and loss circulation based on thermal behavior of wellbore-formation coupled system

Accurately obtaining wellbore-formation temperature distribution during drilling in fractured carbonate formations is the basis for effectively solving the problem of the well kick and loss circulation coexisting (WK-LC). Therefore, based on the energy conservation law and considering the convective heat transfer and variable mass flow caused by well kick and loss circulation, this paper developed a full transient heat transfer model of wellbore-formation coupled system under the WK-LC. The reliability of model was verified by field measured temperature data. Based on field well, the thermal behavior of wellbore-formation coupled system under normal condition, well kick, loss circulation and WK-LC were compared and studied.The results showed that the bottom-hole temperature of well kick and Case1-2 is higher than that of normal condition, while the bottom-hole temperature of loss circulation and Case3-4 is lower than that of normal condition. The temperature difference between annulus and drill string (TD-AD) shows a “wavy line” trend of increasing-decreasing-increasing-decreasing along the well depth. The TD-AD of wellhead is about 6 °C in normal and WK-LC conditions. The traditional wellhead temperature monitoring method can only distinguish well kick and leakage, and it is difficult to judge whether WK-LC occur.In addition, the influence of the distance and well kick/leakage rate difference between the well kick region and the leakage region on thermal behavior of wellbore-formation coupled system was discussed. Finally, a new auxiliary method is proposed to identify the well kick, the loss circulation and the WK-LC. Which will have a significant implication for well killing and leaking stoppage operations.

Analyzing The Influence of Diameter and Winding on Heat Transfer Efficiency in Spiral Tube Heat Exchangers: A CAD-Integrated CFD Study Using Solidworks Flow Simulation

Spiral tube heat exchangers (STHE) are coiled metal devices with two fluid channels around a central core, enabling counterflow or parallel flow of gases, liquids, or both. Compared to traditional straight-tube heat exchangers, STHEs offer a larger heat transfer surface area. This study used Computational Fluid Dynamics (CFD) simulation integrated with Computer Aided Design (CAD) to investigate STHE’s heat transfer performance. The STHE dimensions, a 12-mm copper tube, and a 10-inch PVC shell were adopted from a previous study. Cold and hot water at 20°C and 70°C flowed in parallel at specific flow rates. The objective was to explore the impact of STHE dimensions on heat transfer efficiency and performance. The parameters varied were the internal diameter of the copper tube and the number of spiral coil windings. Results revealed that changing the spiral heat exchanger’s diameter affected the heat transfer rate and coefficient. Larger diameters reduced efficiency due to lower flow velocities and convective heat transfer coefficients. The number of windings significantly affected heat transfer performance, with winding 5 demonstrating the highest rate and winding 7 showing the highest coefficient. CFD analysis reliability was validated by convergence with analytical solutions for heat transfer simulations with varying diameters and windings.

Free convection heat transfer and buoyancy-assisted flow over a heated plate inserted horizontally in a vertical channel with time-varying conditions

Free convection heat transfer and buoyancy-assisted flow over a heated plate inserted horizontally in a vertical channel with time-varying conditions

Numerical Study of Nonlinear Convective Heat Transfer Flow of Metal Oxide Nanoparticle TiO<sub>2</sub>-Enhanced Fluid between Two Concentric Cylinders with Aggregation of Nanoparticles

The utilization of nanofluid is one of the most used techniques for improving heat transfer in applications like heat exchangers, heat storage systems, mining and nuclear power plants. Because of high thermal conditions, the density relation of the working fluids may not be linear, therefore, an analysis is conducted on the quadratic convection of nanofluid flow in a porous annulus region considering an inclination. The phenomenon of temperature-dependent viscosity on the flow, kinematics of nanoparticle aggregation, and heat transport phenomenon with Exponential Space-Related Heat Source (ESHS) and a Temperature-Related Heat Source (THS) are considered. The governing equations are solved numerically. The influence of key parameters is analyzed using 2D and 3D graphs.

COMBINED FORCED AND NATURAL CONVECTION FROM A SINGLE TRIANGULAR CYLINDER

Unsteady laminar confined and unconfined fluid flow and mixed (forced and free) convection heat transfer around equilateral triangular cylinders are investigated numerically. The computation model is a two-dimensional domain with blockage ratios of BR=0.5, 0.25, 0.2, 0.1, 0.05, and 0.0333, with the Reynolds numbers ranging from 100 to 200. The working fluid is water (Pr = 7). The effects of aiding and opposing thermal buoyancy are incorporated into the Navier-Stokes equations using the Boussinesq approximation. The Richardson number, which is a relative measure of free convection, is varied in the range -2 ≤ Ri ≤ 2. The governing equations are solved by using the Finite Volume Method with a second-order upwind scheme used for differencing of the convection terms, and the SIMPLE algorithm is used for the velocity-pressure coupling. A discussion of the effect of the blockage ratio on the mean drag, mean rms lift coefficients, the Strouhal number, and the mean Nusselt number is also presented. The iso-vorticity contours and dimensionless temperature field are generated to interpret and understand the underlying physical mechanisms. The results reveal that, in addition to the Richardson and Reynolds numbers, the blockage rate is effective in the vortex distribution in the channel. It has been determined that the vortices formed behind the cylinder spread to the channel with a decreasing blockage rate. Especially at high Reynolds numbers, both the drag coefficient and the mean Nusselt number are significantly affected by the blockage ratio. For Ri=0, the drag coefficients for BR=0.25 in comparison to the BR=0.05 case are about 9% and 29% larger for Re= 100 and 200, respectively. For BR

MHD Free Convection Heat Transfer in Nano-Fluid Flow in Square Porous Cavity of TiO2 Nanoparticles with Base Fluid Engine Oil

In this article, the MHD-free convection heat transfer behaviour of oil-based nanofluids is explored numerically inside a square cavity enclosure filled with a porous material. The governing equations are derived using Brinkman and Buongiorno’s two-phase nanofluid models. We developed the mathematical model for the over-research problem for heat transfer enhancement applications; the finite volume approach was used to solve dimensionless governing equations. The SIMPLE algorithm is used to calculate the values of pressure and velocity. The investigation of nanofluid with engine oil in the presence of magnetic field in square cavity for the thermal application is not studies. The following parameters are investigated to find out the heat transfer analysis: Ra = 0, porosity = 10, initial volume concentrations = 0–0.05, constant angle of magnetic field = 0, Hartmann Number Ha = 0,100, Prandtl Number Pr = 0.8. The results are also compared with existing literature. It is also indicated that the effect of Nusselt number is very interesting at different values of Ra, i.e., heat transfer rate increases when volume fraction increases at the contact hot wall of the cavity, but reverse phenomena are observed at the cold wall.