Increase In Heat Transfer Rate Research Articles

A review of heat transfer enhancement techniques in power systems

The optimization of modern power systems demands that they enhance heat transfer. Analysis has demonstrated the passive use of nanofluids and surface roughness to greatly enhance thermal conductivity as well as increase heat transfer rates, but without requiring the input of additional energy. Meanwhile, active methods, from pulsating flows to electromagnetic fields, have been shown to decrease thermal resistance and improve system performance. Further significant improvements in efficiency are achieved when hybrid approaches combine both passive and active strategies that overcome the limitations of each method individually. This review critically analyses these heat transfer enhancement methods on the grounds of their principles, mathematical models, and experimental results. The paper presents a detailed understanding of how these techniques are applied in a variety of domains, including power generation, renewable energy systems, and high-performance electronics, based on the incorporation of evidence from 20 validated sources. These findings present the transformative potential of these advancements to address fundamental challenges including energy efficiency, component miniaturization, and environmental sustainability.

Mixed convection in a partially and differentially heated cavity − a finite volume complete flux analysis

Purpose The purpose of this study is to derive a physics based complete-flux approximation scheme by solving suitable nonlinear boundary value problems (BVP) for finite volume method for mixed convection problems, to study the mixed convection phenomenon inside partially and differentially heated cavity for various sets of flow parameters. And, to study the impact of source terms on the cell-face fluxes for various sets of flow parameters for mixed convection problems. Design/methodology/approach The governing equations have been discretized by finite volume method on a staggered grid, and the cell-face fluxes have been approximated by local nonlinear BVP. The cell-face flux is represented as a sum of homogeneous and an inhomogeneous flux term. The proposed flux approximation is fully physics based as it considers the pressure gradient term, thermal buoyancy term and the other source terms in the cell-face flux calculation. The scheme comes out to be second order accurate in space tested with known solution. Also, the scheme has been implemented to study the mixed convection problems in a partially and differentially heated cavity. Findings The numerical order of convergence study shows that the proposed scheme is of second order in space. The scheme is first validated with existing benchmark literature for the mixed convection problem. As the proposed cell-face flux approximation scheme is a homogeneous part and an inhomogeneous part, this study quantifies the influence of the several source terms on the cell-face flux with the help of the inhomogeneous flux term. Then, the mixed convection problems in a partially and differentially heated cavity has been studied. Also, the effect of heat transfer rate at the hot wall is studied for different height of the heat source with different directions of wall movement. The numerical findings show that the local Nusselt number at the left wall is higher when the top and bottom walls move in opposite directions compared to when they move in the same direction, regardless of the Richardson number. In addition, the heat transfer rate at the hot portion of the left wall increases uniformly as the Richardson number decreases when the walls move in opposite directions. However, when the top and bottom walls move in the same direction, the increase in heat transfer rate is not uniform due to the formation of secondary re-circulation of the fluid near the bottom wall. Originality/value In this work, the flux approximation is conducted through local nonlinear BVPs, an approach that, to the authors’ knowledge, has not been previously applied to mixed convection problems. One of the strong advantages of the proposed scheme is that it can quantify the influence of source terms, namely, pressure gradient, cross-flux and the thermal buoyancy force, on the cell face fluxes required in the finite volume methods. Furthermore, the study explores mixed convection in a partially and differentially heated cavity, which is also novel within the current literature. These factors contribute to the originality and scientific value of the research.

Thermal Performance of Selected Nanofluids in Combination with Heat Transfer Inserts

Two methods of heat transfer enhancement that have received considerable interest in recent years are nanofluids and heat transfer inserts. Comparatively few studies have evaluated the performance of systems with heat transfer inserts and nanofluids used in combination. In this study, heat transfer enhancement effects of alumina/water (Al2O3/H2O), copper oxide/cetyltrimethyl ammonium bromide/water (CuO/H2O/CTAB), and activated carbon/arabinogalactan/water (C/H2O/ARB) nanofluids both with and without hiTRAN® inserts were investigated using double-pipe heat exchangers in a customized experimental rig. The increase in heat transfer rates due to the nanoparticles (1% by mass of the nanofluids) was comparable in magnitude to the increase observed for the inserts without nanoparticles (i.e. water only), however, the friction factors of the inserts in water were considerably higher than for the nanofluids. The effects of the two heat transfer enhancement methods appeared to be additive when inserts were used in conjunction with nanoparticles. Of the three nanofluids the C/H2O/CTAB nanofluid had the best thermal enhancement assessed using the most commonly applied enhancement index, both with and without inserts. Due to agglomeration of nanoparticles, particularly for the Al2O3/H2O nanofluid that did not have a surfactant, the nanofluids were much less practical to deal with than the inserts.

Magnetohydrodynamics mixed convection and sensitivity analysis of non-Newtonian power-law fluid in a ventilated cavity with a rotating heated cylinder

Magnetohydrodynamics (MHD) mixed convection of non-Newtonian power-law fluid for laminar flow inside a ventilated square cavity with an inner rotating heated cylinder is studied numerically using the Galerkin weighted residual finite element method (GFEM). The left vertical wall has an inlet port at its top, while the right vertical wall has an outlet port at its bottom. Several significant parameters, including Hartman number ( 0 ≤ Ha ≤ 80 ), Prandtl number ( 20 ≤ Pr ≤ 100 ), Reynolds number ( 100 ≤ Re ≤ 400 ), power-law index ( 0.6 ≤ n ≤ 1.4 ), angular rotational velocity ( ω = − 20 , 0 , 20 ), and magnetic field inclination angle ( 0 ∘ ≤ γ ≤ 120 ∘ ) on the flow is numerically investigated. Streamlines, isotherms, local Nusselt numbers (Nu), average Nusselt numbers ( Nu ¯ ) , sensitivity analysis, and other numerical representations of the results are provided. The research showed that when the magnetic field is aligned parallel to the gravitational field ( γ = 90 ∘ ), the heat transfer rate increases, and the buoyancy force leads the heat transfer process. In the clockwise rotational condition of the cylinder ( ω = 20 ) , the local Nusselt number increases by 69.84% while Re rises from 100 to 400. The relation between Nu ¯ and the power-law index is inversely proportional in all three rotational conditions of the cylinder. In the cylinder's clockwise and anticlockwise rotational directions, Nu ¯ rises as the Hartmann number rises from 0 to 80. When the Reynolds number increases, Nu ¯ also increases in all three rotational conditions of the cylinder. A sensitivity analysis using variance analysis (ANOVA) has been performed in this study.

Numerical Analysis of Dual Slot Pulsating Nanofluid Impinging Jets

Jet impingement is a widely utilized technique in engineering, particularly for cooling high-temperature systems like aircraft engines and electronic devices. This study employs numerical analysis to examine the flow dynamics of dual impinging pulsating nanofluid jets, utilizing the ANSYS software platform. This research examines the combined impact of key parameters, including jet geometry, pulsation frequency and amplitude, nanoparticle volume concentration, and Reynolds numbers, on the efficiency of heat transfer. The impact of aluminum oxide (Al₂O₃) nanofluids with varying concentrations (1%, 2%, 4%, and 5%) on thermal performance is assessed. The findings of the study demonstrate that the pulsating jets generate bidirectional swirling flows and reverse vortices upon impact with the surface, resulting in notable enhancements in local heat transfer rates. These vortices expand and form wall jets, which contribute to an increase in the heat transfer coefficients and Nusselt numbers. The simulations demonstrate that higher pulsation frequencies (30 Hz) result in a 10% increase in heat transfer efficiency compared to lower frequencies (10 Hz). This is attributed to enhanced flow dynamics and improved heat distribution. Moreover, the incorporation of nanoparticles markedly enhances heat transfer efficiency. The Nusselt numbers were observed to increase by 18% when the concentration of nanoparticles reached 5%, in comparison to plain water. Additionally, the study underscores the significance of jet spacing, wherein an optimal separation distance of 100 mm between the dual jets was identified as a means of maximizing heat transfer by fostering effective vortex interactions. Higher Reynolds numbers contribute to the formation of thinner thermal boundary layers, thereby facilitating increased heat transfer rates, particularly at the stagnation points where the flow impinges directly on the surface. Overall, the study demonstrates that substantial enhancements in heat transfer can be achieved by optimizing key parameters such as pulsating frequency, amplitude, nanoparticle volume concentration, and jet distances.

Machine learning analysis for heat transfer enhancement in nano-encapsulated phase change materials within L-shaped enclosure with heated blocks

Machine learning analysis for heat transfer enhancement in nano-encapsulated phase change materials within L-shaped enclosure with heated blocks

Improving heat transfer in an air-cooled engine by redesigning the fins

Heat transfer modelling and simulation were carried out in a single-cylinder, four-stroke, air-cooled engine to evaluate the heat transfer rate of the engine block. The modelling studies of cylinders with different numbers of fins and different geometry were performed using the SolidWorks computer platform. The tested components were made of 6063-T6 aluminium alloy castings. The simulation concerned different numbers of fins as well as changing the geometry of fins with circular and rectangular perforations. The results of the studies showed the possibility of improving the power to mass ratio for cylinder efficiency and heat transfer rate. It was shown that a large number of fins leads to an increased heat transfer rate, but it affects the overall engine efficiency due to the increase in the total engine mass. Circular perforation is a better design solution than rectangular perforated fins with the same cross-section. Circular perforation provides a lower engine cylinder mass and gives more than 4 % better heat transfer rate. The perforation size was tested using circular perforations with a diameter of 7.14 mm, 8.5 mm and 10 mm. With a 7.14 mm diameter perforation the heat transfer rate increases slightly compared to the other tested ones, while a 10 mm diameter perforation provides the best mass reduction.

A Multi-Sized Unit Cell Method for the Design of LPBF Lattice Support Structures Concerning Complex Geometries

Abstract Composed of individual unit cells strategically arranged to achieve a desired function, lattices are a promising solution for laser powder bed fusion support structure design in additive manufacturing. Despite their many advantages (e.g., multifunctionality and reduced material cost), prior work in lattice support structure design primarily focuses on horizontal support domains that are not translatable to support domains for complex geometries, thereby limiting their application. This work introduces a multi-sized unit cell design optimization (MSO) method to create lattice support structures (LSS) for parts with complex geometries. The proposed method utilizes voxelization to generate LSS using box-like unit cells of different sizes. It also allows for efficient, high-dimensional design optimization for the types and locations of user-specified unit cells through a modified simulated annealing-based optimization algorithm. The effectiveness and efficiency of the MSO method are demonstrated through the case study of an adapter pipe for a high-temperature heat exchanger. For this demonstration, LSS using multi-sized unit cells is designed to increase heat transfer rate while satisfying structural integrity and material cost constraints. The case study results indicate that the design of the LSS derived from the MSO method fulfills all constraints, including the design constraint of 50% material cost reduction, compared to the solid support structure. In contrast, the lattice support structure designs derived from equal-sized unit cell methods either cannot satisfy all design constraints or have a lower heat transfer rate than the design of the MSO method.

Heat transfer analysis of CuO-ZnO/water hybrid nanofluid in a Shell and tube heat exchanger with various tube shapes

Heat transfer analysis of CuO-ZnO/water hybrid nanofluid in a Shell and tube heat exchanger with various tube shapes

Numerical performance analysis of modified vertical U-tube ground heat exchangers by adjusting the impact of leg spacing

Numerical performance analysis of modified vertical U-tube ground heat exchangers by adjusting the impact of leg spacing

Analysis of heat transfer coefficient in radiator cooling system using TiO2/CuO hybrid fluid

The automotive industry is growing, encouraging more efficient car cooling systems, especially radiators. Innovations are constantly being made to improve the performance of radiators. Choosing the correct fluid is one of the ways to increase heat transfer. This study aimed to compare the performance of coolant OBC and TiO2/CuO hybrid fluid mixed with coolant OBC to investigate the increase in heat transfer in the car's radiator. The first step is to make TiO2/CuO hybrid fluid with a two-step method, with volume fraction variations of 1.0, 2.0, 3.0, 4.0, and 5.0%, and observe stability for 30 days. Viscosity and thermal conductivity tests are used to assess the thermophysical properties of the sample. Hybrid fluid samples of TiO2 / CuO with a volume fraction of 5.0% showed the best stability and thermal conductivity, then were added to the coolant brand OBC (1:4). The results showed an increase in heat transfer rate of 23% and a heat transfer coefficient of 20% in the TiO2/CuO hybrid fluid added to the coolant OBC

Advanced heat transfer analysis using RSM-BBD for MHD hybrid nanofluid flow over a nonuniform stretching sheet with viscous dissipation

The recent studies focus on optimizing conditions to maximize the heat transfer rate while minimizing energy consumption, a key goal for various industries in both production processes and Automotive industry efficiency. Hybrid nanofluids play a crucial role in improving heat transfer phenomena. This study examines the enhanced heat transfer properties of a water-based hybrid nanofluid containing Al2O3 and SiO2 nanoparticles as it flows through a nonlinear stretching sheet in a porous medium. The convective flow is further influenced by a magnetic field and thermal radiation, adding complexity to the flow dynamics. To simplify the analysis, dimensional physical quantities are converted to non-dimensional parameters using appropriate similarity rules. These transformed equations are then numerically solved using the bvp4c function in MATLAB. To achieve optimal heat transfer rates, a robust statistical method known as response surface methodology (RSM) is employed, and validation is performed through an analysis of variance. Graphical representation is used to examine parametric behaviour, and a brief physical description is provided. Key findings include: the hybrid nanofluid shows a 10.61% increase in heat transfer rate compared to the base fluid at R = 0.2; the drag force coefficient for the Al2O3/H2O nanofluid is reduced by 13.98% compared to other hybrid nanofluids; and an increase in the nonlinear stretching sheet parameter improves velocity distribution while reducing temperature distribution. This study can be used in automotive transmission systems to enhance heat dissipation and lubrication, improving the efficiency and durability of the transmission.

Graphene Coating and its Effect on Performance of Box Type Solar Cooker: An Experimental Investigation

Background: Solar cookers have been the subject of several theoretical and empirical investigations, with numerous modifications attempted to increase efficiency and security. Solar cookers need much sophisticated research and enhancement work to function better. A thorough grasp of the application of graphene in box-type solar cooking systems is crucial for both solar energy and graphene. Objective: To improve the performance of box-type solar cookers, this patent research aims to offer an experimental investigation and insightful information on of applying graphene coating to the absorber plate and its derivative. Materials and Methods: To ensure equal dispersion of graphene into the black paint, three samples containing (1, 3, and 5wt%) of graphene embedded with the paint were produced with 1mm, 3mm, and 5mm thickness of the coating and stirred at 400 rpm for two hours using a magnetic stirrer. Xray diffraction and scanning electron microscopy have been studied to comprehend the influence of graphene nanoparticles on the surface morphology of the coated absorber panel. Performance evaluations of the box-type solar cookers were conducted with and without a graphene coating on the absorber plate, and data has been recorded for each case. Results: The results of patent research show that the absorber plate with (1, 3, and 5wt.%) of graphene embedded with black paint 1mm, 3mm, and 5mm thickness coating has a maximum thermal efficiency of 41.48% with 97.08 W cooking power, 46% with 109.35 W cooking power, and 49% with 114.77 W cooking power for the average solar irradiation is 978 W/m2. Discussion: It was determined that the cooking power (P), the first figure of merit (F1), and the second figure of merit (F2) were all satisfactorily achieved. Embedding black paint into graphene coating has been shown to significantly influence the heat transmission and thermal performance enhancement of box-type solar cookers, as demonstrated by the findings of X-ray diffraction and Scanning Electron Microscopy analysis. Conclusion: The current research makes it abundantly evident that the incorporation of graphene into the absorber plate of a box-type solar cooker, together with the application of a black paint coating, leads to increased heat transfer rates, which in turn provides an increase in cooking power. Because of this, graphene is an attractive nanomaterial that has the potential to improve the performance of box-type solar cookers, which is the novelty of this research work.

Numerical exploration of radiative heat transfers in a magneto bioconvection Maxwell fluid passing through a spinning disk

When applied to a rotating disk, Maxwell nanofluids have a wide range of applications in various fields. They provide increased heat transfer efficiency in cooling systems, which is essential for preserving the ideal operating temperatures of spinning gears like disk brakes and turbines. Furthermore, Maxwell nanofluids in microfluidic devices provide improved fluid manipulation and control, improving performance in applications such as microscale pumps and lab-on-a-chip systems. This article has numerically examined the magneto-bio-convection flow of Maxwell, which includes nanofluid, past a disk surface based on these applications. We present the model equations in PDE format, then shift them to ODEs using the appropriate variables. We utilize the bvp4c approach to obtain numerical solutions to the modeled equations. We also take into account the effects of thermal radiation, heat sources, Brownian motion, thermophoresis, chemical reactivity, and activation energy. We find that a higher stretching/shrinking variable has enhanced the radial velocity profile, while simultaneously diminishing the axial and angular velocity field. While the velocity profiles in the axial direction and redial direction have reduced with larger magnitude of Maxwell fluid variable. The thermal distributions have risen due to higher magnetic, Brownian motion, thermophoresis, heat sources, and thermal radiation components. Thermophoresis, magnetic and thermal radiation, heat sources, and Brownian motion all contribute to an increase in heat transfer rates.

Non-similar approach for enhanced heat and mass transfer in nanofluid using Keller box algorithm

The nanofluids provide various benefits over pure fluids in heat and mass transport applications; hence, their research is crucial. For instance, they can increase heat transfer rate by enhancing the fluid’s thermal conductivity and may enhance mass transfer rate by changing the surface characteristics. Furthermore, nanofluids are being demonstrated to effectively diminish pressure drops in exchangers for heat, which can lower energy consumption and operating expenses. In the existing literature, the majority of the theoretical studies considered self-similar flows. However, there are certain actual flow situations that do not allow for a self-similar solution. The current study considers such of those situations where the non-similarity of the transport phenomena is unavoidable. The non-similarity of the present problem is caused by the consideration of thermophoretic diffusion or the contribution of viscous dissipation when the wall temperature follows a power-law form. For a pure fluid, the same problem admits a self-similar solution in the absence of viscous dissipation effects. In this problem, the non-similarity is caused by the nature of the thermal transport process and not because of the momentum transport. Therefore, the consideration of viscous dissipation in the boundary layer of nanofluid is an interesting aspect to explore the behavior of thermal and mass transport phenomena. Moreover, the current analysis intends to investigate the transport enhancement in a non-similar flow of a nanofluid by utilizing the Buongiorno model. In the current nonsimilar modeling, possibilities for the existence of a self-similar solution are also highlighted. An implicit finite-difference numerical scheme, the Keller-Box method, is utilized. The problem involves several physical parameters of interest, such as the Eckert number, Lewis number, Brownian motion parameter, and thermophoresis parameter, whose potential impact on the non-similar nature of the problem and on thermal enhancement is analyzed and quantified.

Optimizing heat transfer within a rectangular channel through intermittent metal foam block configurations: A numerical study

AbstractA thorough numerical investigation was carried out to examine the heat transfer characteristics within a rectangular channel integrated with metal foam blocks for solar air heating applications. The study employed numerical simulations using the extended Darcy–Forchheimer model with the assumption that there exist local thermal nonequilibrium conditions within the porous foam region. Four configurations, denoted as P–A, P–P, A–P, and A–A, were explored based on the presence or absence of foam blocks relative to the heated section. The study meticulously analyzed the influence of key parameters, such as the number of foam blocks (N = 1–5), permeability (quantified by pore density, ), and Reynolds number (), on the thermohydraulic performance. The results were promising, indicating a significant increase in the average Nusselt number () with the inclusion of foam blocks, albeit accompanied by an undesirable increase in the friction factor. Among the various configurations, the P–A arrangement, where porous blocks are situated at the entrance of the heating channel, exhibited superior thermal performance. Furthermore, the optimal heat transmission rate was attained with a single porous block (N = 1) in the P–A configuration, at a Reynolds number of 16,000 and high permeability (). Conversely, the maximum friction factor was observed with five porous blocks (N = 5) in the A–P configuration, at a Reynolds number of 4000 and low permeability (). The exhaustive analysis of thermohydraulic performance was evaluated using the performance evaluation criterion (PEC), which optimizes the trade‐off between increased heat transfer rate and consequent pressure loss. The P–A arrangement, particularly with higher permeability and a minimal number of porous blocks, demonstrated the highest PEC value of 2.71, representing a significant 171% improvement compared with an empty channel. This study underscores the effectiveness of strategically placing and optimizing metal foam blocks to improve the thermal performance of heat exchanger systems.

Exploring Natural Convection and Entropy Generation in a Closed Water Tank Utilizing Nanofluid: a Computational Study

Theoretical framework: This study presents a comprehensive investigation into three-dimensional natural convection within a confined cavity filled with an alumina-water nanofluid. Objective: Utilizing numerical simulations, we explore the influence of nanoparticles' volume fraction and Rayleigh number () on entropy generation, heat transfer efficiency, and fluid behavior within the water tank. Method: The study delves into the conservation equations governing mass, momentum, and energy within the context of three-dimensional laminar natural convection. It focuses on steady, incompressible flow, employing the Boussinesq approximation to account for variations in fluid density due to temperature gradients. Results and conclusion: Our findings indicate that increasing Rayleigh numbers lead to heightened entropy generation, with values ranging from to, primarily driven by intensified buoyant flow. However, the presence of nanoparticles significantly mitigates entropy generation, enhancing the overall thermal performance of the system. Moreover, nanofluids demonstrate superior heat transfer capabilities compared to pure fluids, with higher nanoparticle concentrations resulting in increased heat transfer rates, ranging from to alumina. Research implications: As a result of such thorough research, qualitative examinations of velocity fields and entropy generation patterns further highlight the role of nanofluids in improving heat transfer efficiency while reducing irreversible processes within the cavity.

Electro-magnetohydrodynamic (EMHD) Darcy–Forchheimer flow of Sutterby nanofluid with variable thermal conductivity over a stretching sheet: Finite difference approach

This paper examines the enactment of a two-dimensional, steady, non-Newtonian nanofluid flow over a stretching sheet. The utilization of magnetic influences acting in the direction normal to the Darcy–Forchheimer boundary layer flow of the Sutterby nanofluid with variable thermal conductivity is taken into consideration. This study takes into account the effects of thermophoresis and Brownian motion. The study found that a 15% increase in magnetic field strength resulted in a 10% increase in heat transfer rate. Similarly, a 20% increase in nanoparticle volume percentage causes a 12% increase in the convective heat transfer coefficient. The problem’s model is formulated in the form of partial differential equations (PDEs), transformed via similarity transformation into nonlinear ordinary differential equations (ODEs). Applying the finite difference method yields the solution to reduced equations. EMHD Darcy–Forchheimer flow and nanofluid dynamics are combined in cutting-edge technology. This is important for many industrial and technical applications. Moreover, providing a strong computational framework provides a precise simulation of the flow behavior. By providing insights into the intricate interactions between electromagnetic forces, porous medium effects, and variable thermal conductivity in nanofluids flow across a stretched sheet, this study makes an essential contribution to the science of fluid dynamics. This research is very significant and enlightening for researchers and professionals who are interested in the design and optimization of heat transfer systems. The fluid flow is examined thoroughly and graphically, and the relationship between the profiles of velocity, temperature, and concentration and other important physical limitations is investigated. The effect of various physical parameters on concentration, velocity, temperature, skin friction, Nusselt number and heat flow coefficient is verified and examined using graphs and tables.

Experimental analysis of W/EG based Al2O3-MWCNT non-Newtonian hybrid nanofluid by employing helical tape inserts inside a corrugated tube

Experimental analysis of W/EG based Al2O3-MWCNT non-Newtonian hybrid nanofluid by employing helical tape inserts inside a corrugated tube

Flow and heat transfer of non-miscible micropolar and Newtonian fluid in porous channel sandwiched between parallel plates

Flow and heat transfer of non-miscible micropolar and Newtonian fluid in porous channel sandwiched between parallel plates