Increment Of Heat Transfer Rate Research Articles

Computational Analysis of MHD Nanofluid Flow Across a Heated Square Cylinder with Heat Transfer and Entropy Generation

Abstract The mixed convection heat transfer of nanofluid flow in a heated square cylinder under the influence of a magnetic field is considered in this paper. ANSYS FLUENT computational fluid dynamics (CFD) software with a finite volume approach is used to solve unsteady two-dimensional Navier-Stokes and energy equations. The numerical solutions for velocity, thermal conductivity, temperature, Nusselt number and the effect of the parameters have been obtained; the intensity of the magnetic field, Richardson number, nanoparticle volume fraction, magnetic field parameter and nanoparticle diameter have also been investigated. The results indicate that as the dimensions of nanoparticles decrease, there is an observed augmentation in heat transfer rates from the square cylinder for a fixed volume concentration. This increment in heat transfer rate becomes approximately 2.5%–5% when nanoparticle size decreases from 100 nm to 30 nm for various particle volume fractions. Moreover, the magnitude of the Nusselt number enhances with the increase in magnetic field intensity and has the opposite impact on the Richardson number. The findings of the present study bear substantial implications for diverse applications, particularly in the realm of thermal management systems, where optimising heat transfer is crucial for enhancing the efficiency of electronic devices, cooling systems and other technological advancements.

Squeezing MHD Flow of Sodium Alginate-Based Casson Hybrid Nanofluid with Soret and Dufour Effects

Ultrahigh-performance cooling is one of the essential requirements in the industrial technology. Hence, the new heat transfer fluid, hybrid nanofluid is introduced to increase the thermal conductivity of fluid and investigated with various physical parameters. The unsteady magnetohydrodynamics (MHD) flow of Casson hybrid nanofluid through two surfaces in a permeable medium with chemical reaction are explored. The hybrid nanoparticles of Alumina and Copper is dispersed in the base fluid of sodium alginate . The discretize equations are solved using similarity transformation and Keller-box methods. The comparison of the current results with the published results for validation is conducted and discovered in proper agreement. The impacts of squeeze, magnetic, porous media, chemical reaction, heat sink/source, and Soret and Dufour on behaviour and physical quantities of flow are discussed. The graphical results show the squeeze of two surfaces accelerates the fluid velocity near the upper plate region. Further, the velocity slowing down when and increases, and it elevates as and rises in the middle of channel. The increment of heat transfer rate and temperature of fluid is shown for increasing Ec, y and Du, and the opposite behaviour is discovered with raise in. The fluid concentration decreases and the mass transfer rate enhances for rising Sr. The concentration enhance and rate of mass transfer reduce with the constructive chemical reaction, whereas contrary effects is shown for destructive chemical reaction.

Magnetohydrodynamic flow of two immiscible hybrid nanofluids between two rotating disks

The two-layer model of the magnetohydrodynamic flow of hybrid nanofluid (HNF) between two disks of the same radii is analyzed in this study. The base fluids of both the hybrid nanofluids are immiscible so that these two fluids form an interfacial layer making the study more unique and innovative. The heat source/sink with viscous dissipation effect on energy equation is discussed. The governing equation is in the form of PDEs that are later reduced to ODEs with the help of the Von Karman transformation. The resulting ODEs are solved using the RK method and the results are interpreted graphically. In addition to temperature and concentration gradient, the radial, tangential and axial velocities for different parameters are studied. The results indicate that the physical ratios such as viscosity and thermal conductivity ratios can improve the fluid motion and temperature even in the presence of magnetic field. Also, the ratio of stretching rate produced by the rotation of disk can effectively control the fluid motion. The two fluid flow between two rotating disk forms an interfacial layer between the fluids results in the increment of heat transfer rate which finds application in the field such as heat ex-changer equipment, Cryogenic systems, electronic appliances, and solar collectors.

Finite element analysis of the impact of particles aggregation on the thermal conductivity of nanofluid under chemical reaction

A theoretical investigation is being conducted to determine the impact of nanoparticle aggregation (NPA) and thermal radiation on the radiant heat of nanofluids along with the vertical cylinder. An efficient thermal conductivity model for nanofluids is constructed based on the fractal distributive properties of nanoparticle aggregation. In view of two alternative methods of heat conduction, comprising particle aggregation and convection, the model is represented as a function of the fractal size and concentration. The contemporary models for nanofluid thermal conductivity include a significant role in nanoparticle aggregation. The impact of particle diffusion in the temperature field on aggregation and transport has yet to be investigated. The controlling boundary value problem is transformed into a system of nonlinear ordinary differential conditions, which are then solved numerically by utilizing the finite element technique with similarity transformations. The exceptional features of nanoparticles, such as high thermal conductivity, are highly significant in advancing nanotechnology, heat exchangers, material sciences, and electronics. The temperature field is observed higher in the presence of nanoparticle aggregation. The concentration gradient decreases the viscosity of water-based nanofluids, resulting in an increasing velocity. It is observed that the effect of nanoparticles aggregation on the boundary is descending by the including parameters causing an increment in heat transfer rate. The numerical approach to optimal meshing has reached convergence, and the accuracy of the presented results is supported by the fact that they are close to the results found in the relevant research.

Three-dimensional analysis of the thermal and hydraulic performance of finned and un-finned tubes in a staggered array

• Novel type of leeward cut fin is compared with a conventional circular fin. • Fin spacing was varied to evaluate thermo-hydraulic behaviour. • Leeward cut fin gives lower heat transfer rate and pressure drop than circular fin. • Performance study suggests the potential of leeward cut fins for material saving. A novel type of finned tube obtained by removing the downstream section of the conventionally used complete circular finned tube (CCFT) is studied. The resulting novel type of finned tube obtained is termed leeward cut finned tube (LCFT). The thermal and hydraulic behaviour of these novel finned tubes is compared with CCFT and un-finned tubes. Leeward cut fins are specifically studied to check their capability to give equivalent heat transfer like that of complete circular fins. This study is carried out in the Reynolds number range 4330 ≤ Re ≤ 8790 and fin spacing range 2 ≤ s ≤ 4 mm . The transition SST model is implemented to solve the RANS equations. Heat transfer coefficient at the downstream section of fins is found to be less than the upstream section; hence, it can be advantageous to remove some portion of the downstream section of the fin. The leeward cut finned tubes give a lower value of heat transfer rate and pressure drop when compared with complete circular finned tubes. The heat transfer Colburn factor j for leeward cut fins is higher than CCFT and un-finned tubes. The friction factor is the lowest for CCFT and the highest for un-finned tubes. Analysis of the effect of fin spacing showed an increment in heat transfer rate and a decrease in pressure drop when fin spacing is increased from 2 to 4 mm. The studied geometries are evaluated based on their thermo-hydraulic performance parameters ( PEC and Z/E ). The performance evaluation criterion PEC for LCFT is higher than CCFT by 30–46 % at fin spacing of 2 mm, whereas for spacing of 4 mm, it is 21–23 % higher. The ratio of heat transfer rate per unit temperature difference to power provided to the heat exchanger Z/E is lower for LCFT than CCFT by 5–8 % for fin spacing of 2 mm, whereas for fin spacing of 4 mm, it is lower by 9–12 %. Based on the results, CCFT performs better than LCFT, but they have more fin material requirements (∼50 %). Hence, the LCFT can be seen as a potential novel type of fin to give equivalent heat transfer with the advantage of material savings.

The crucial features of aggregation in TiO2-water nanofluid aligned of chemically comprising microorganisms: A FEM approach

The main objective of this investigation is to reveal the effects of nanoparticle aggregation aligned to thermal radiation with the prescribed heat flux. The Cattaneo–Christov heat flux (non-Fourier) and mass flux (non-Fick's) approaches in the optimized Buongiorno's model have been used to analyze the nanofluid magneto-transport mechanisms over the surface impacted by the gyrotactic behavior of microbe dispersion. The partial differentials are transformed into the set of nonlinear differential equations through boundary layer estimations and similarity substitutions, then computed by applying a variational finite element strategy. Researchers are looking into tiny nanoparticles because they have amazing properties, such as excellent thermal conduction, which are needed in advanced nanotechnology, heat exchangers, materials engineering, and technologies. The significance of this extensive study is to enhance the heat transition. Various aspects of the aggregation parameters on nanofluid velocity and temperature patterns are investigated and visually illustrated concerning the involved physical parameters. The effect of nanoparticle aggregation on the boundary is descending by the including parameters causes an increment in heat transfer rate. A significant correlation has been observed between the sets of results, which represents the accuracy of the finite element method used herein. The computations have been done by reducing the size of the mesh so that the numerical analysis can be used to ascertain convergence in the results.

W-cut twisted tape's effect on the thermal performance of a double pipe heat exchanger: A numerical study

A numerical investigation has been performed for double pipe heat exchanger to enhance heat transfer rate and thermal performance factor using W- cut twisted tape. W-cut twisted tape with depth to width ratio (viz. depth of W-cut to width of the twisted tape) of 0.2–0.6 has been taken for study. Realizable k-ε turbulence model has been used to determine heat transfer rate in the turbulent zone. Swirl flow analysis shows that flow is divided into two regions; one is near the wall and the other away from the wall. A linear increment in heat transfer rate has been observed relative to Reynolds number. Maximum enhancement in heat transfer rate has been observed at Reynolds number of 15300. The friction factor decreases with increasing Reynolds number but drastically increases with the employing of W-cut twisted tape. An increment in the thermal performance factor has been observed by increasing the depth of cut. The maximum thermal performance factor was observed at a lower Reynolds number. Comparison of thermal performance factor with previous studies has been done and it was observed that present studies have better thermal performance factor relative to other inserts.

Performance analysis of melting phenomena in an ice-freezing type direct-contact heat exchanger

The present study endeavours to represent a latest concept of utilizing similar heat transfer fluid (HTF) and phase change material (PCM) in a direct contact type PCM heat exchanger (DCHEX). This technique has been found more effective during melting process. In the following investigation, a segment of the heat exchanger is numerically modelled to analyse the temporal behaviour of the latent heat energy storage system during the cycle of discharging. The transient numerical computation incorporates an iterative, finite volume method based on enthalpy-porosity technique for numerically model the phase change phenomena. For the analysis, water is used as working fluid. To show the performance enhancement of this technique during melting process, a series of simulations are performed to examine the impact of varying HTF inlet condition and flow rates. The changes in the configuration of the heat exchanger are studied. Heat exchanger parameters such as difference between inlet and outlet temperature (ΔT), heat release rate (Q), temperature effectiveness (θ) and volumetric heat transfer coefficient (Uv) are evaluated for all such cases. A uniform exit temperature of the HTF is observed for most of the time with significant increase in the heat transfer in the direct contact type heat exchanger. Three distinct stages namely initial, intermediate and final phases are observed during the melting process. During the initial phase the parameters exhibits uniform behaviour. In the intermediate phase there is significant drop and rise in the parameters while during the final phase the value of parameters diminishes except for Uv. Increasing HTF flow rate promotes increment in heat transfer rate while increasing the inlet temperature of HTF is more desirable to increase the overall heat transfer coefficient.

Effect of Non-Identical Magnetic Fields on Thermomagnetic Convective Flow of a Nanoliquid Using Buongiorno’s Model

Energy transport intensification is a major challenge in various technical applications including heat exchangers, solar collectors, electronics, and others. Simultaneously, the control of energy transport and liquid motion allows one to predict the development of the thermal process. The present work deals with the computational investigation of nanoliquid thermogravitational energy transport in a square region with hot cylinders along walls under non-uniform magnetic influences. Two current-carrying wires as non-identical magnetic sources are set in the centers of two heated half-cylinders mounted on the bottom and left borders, while the upper wall is kept at a constant low temperature. Buongiorno’s model was employed with the impact of Brownian diffusion and thermophoresis. Governing equations considering magnetohydrodynamic and ferrohydrodynamic theories were solved by the finite element technique. The effects of the magnetic sources strengths ratio, Lewis number, Hartmann number, magnetic number, buoyancy ratio, Brownian motion characteristic, and thermophoresis feature on circulation structures and heat transport performance were examined. For growth of magnetism number between 0 and 103 one can find an increment of heat transfer rate for the half-cylinder mounted on the bottom wall and a reduction of heat transfer rate for the half-cylinder mounted on the left wall, while for an increase in magnetism number between 103 and 104, the opposite effects occur. Moreover, a rise in the Lewis number characterizes the energy transport degradation. Additionally, an intensification of energy transport could be achieved by a reduction of the thermophoresis parameter, while the Brownian diffusion factor and buoyancy ratio have a negligible influence on energy transport. Furthermore, the heat transfer rate through the half-cylinder mounted on the bottom wall declines with an increase in the magnetic sources strengths ratio.

Unsteady MHD hybrid nanofluid flow towards a horizontal cylinder

Transport phenomena near the stagnation region are common in the manufacturing industry, especially in polymer and extrusion processes, which need continuous improvement to enhance the process's quality standard. Hence, the present numerical investigation aims to test the performance of unsteady stagnation-point flow past a stretching/shrinking horizontal cylinder in a hybrid nanofluid. The impact of a magnetic field on the boundary layer flow is also considered. The mathematical model that had been simplified is solved numerically via the MATLAB bvp4c procedure. Several decisions have arisen from the numerical findings of this study. The results reveal that as the concentration of nanoparticle volume fraction increases, which infers the transition of nanofluid to hybrid nanofluids, a 2% increment in heat transfer rate is observed. The unsteadiness parameter clearly improves thermal performance by a 50:50 mixing ratio containing 2% of copper and alumina nanoparticles. Furthermore, increasing the curvature parameter evidently increases thermal efficiency by approximately 22.8%. On the other hand, increasing the magnetic parameter deteriorates thermal properties, leading to a drastic reduction in the heat transfer rate up to 32.6%. Finally, the initial solution's stability is confirmed by the stability analysis.

Influence of fluid flow characteristics and heat transfer in a tube heat exchanger using H-shape inserts with circular ring

The heat transfer and fluid flow characteristics in a tube heat exchanger using H-shape inserts with circular ring (CRWHS) has been done by computationally and experimentally. In this investigation parameters like ratio of the diameters and pitches are considered. The value of diameter and pitch ratios are (DR=0.8, 0.9), (PR=3, 4) respectively. The main section in which investigation was done is 1.5m long and the hydraulic diameter of the tube is 68.1mm. 1000 W/m2 heat flux was provided in the main section. Heat flux was constant throughout the investigation. Air is used as a working medium in which 6000 to 21000 Reynolds number was used for the investigation. The observation revealed that the increment in heat transfer rate is 4.56 times as compare to smooth tube for the circular ring with H-shape inserts. In case of DR=0.8 and PR=3, maximum thermal performance factor was obtain which is 3.24. In GIT the deviation in Nusselt number & friction factor is limited to ±0.4% & ±0.1% respectively. CFD analysis result comparisons with experimental one are presented in which the maximum deviations for thermal performance factor are limited to ±3.6%.

Control of dusty nanofluid due to the interaction on dust particles in a conducting medium: Numerical investigation

With ultra-high thermal significances, the nano-materials present some fundamental applications in many thermal engineering eras, mechanical and chemical engineering and modern technology. For sustainable development of industrial growth of a country, the enhancement in energy production and resources become one of the most fundamental challenges for scientists. This analysis presents the thermal aspects of dust nanoparticles in a dusty nano-material for the interaction of transverse magnetic field come across an expanding surface. The conjunction of Maxwell model thermal conductivity influences the characteristic of thermal properties that is helpful to enrich the heat transport phenomena. A mathematical model is prepared by considering metal nano-material (copper and silver) in association with the conventional fluid water. The numerical treatment is deployed for the solution of the complex nonlinear problem characterized by dust phase material and fluid transformed governing equations. The transport of heat energy is affected by the transient behavior of the volume fraction, dust particle number density in conjunction with magnetic field. However, the key features of the outcomes for the characterizing parameters are lubricated through graphs and simulated numerical values for the rate coefficients are presented in table that leads to the validation work with the earlier investigation. An increment in heat transfer rate is noted with suspension of copper nanoparticles in the dusty fluid while heat transfer reduces in case of silver nanoparticles. The nanoparticles temperature enhanced with interaction parameter and specific heat ratio. The current analysis has a greater impact in bio-medical since i.e. the blood flow within the artery as well as several industrial and engineering applications. All these aspects depend upon the nanoparticles particle size therefore the dust and nanoparticles proposed here are spherical.

Hybrid Nanofluid Flow over a Permeable Shrinking Sheet Embedded in a Porous Medium with Radiation and Slip Impacts

The study of hybrid nanofluid and its thermophysical properties is emerging since the early of 2000s and the purpose of this paper is to investigate the flow of hybrid nanofluid over a permeable Darcy porous medium with slip, radiation and shrinking sheet. Here, the hybrid nanofluid consists of Cu/water as the base nanofluid and Al2O3–Cu/water works as the two distinct fluids. The governing ordinary differential equations (ODEs) obtained in this study are converted from a series of partial differential equations (PDEs) by the appropriate use of similarity transformation. Two methods of shooting and bvp4c function are applied to solve the involving physical parameters over the hybrid nanofluid flow. From this study, we conclude that the non-uniqueness of solutions exists through a range of the shrinking parameter, which produces the problem of finding a bigger solution than any other between the upper and lower branches. From the analysis, one can observe the increment of heat transfer rate in hybrid nanofluid versus the traditional nanofluid. The results obtained by the stability of solutions prove that the upper solution (first branch) is stable and the lower solution (second branch) is not stable.

Performance Enhancement and Analysis of Shell and Tube Type Heat Exchanger

Nano-fluids are playing a very important role in thermal stream due to its physical and thermal properties. Now a day it was observed that there are lots of papers which have explained the deep study on nanofluids. There are so many areas in which nanofluids are used to increase the thermal efficiency and coefficient of heat transfer. In this review comprehension, many research works which are related to nanofluids used as a working fluid in shell and tube heat exchanger will be summarized in efficient way. And theoretical as well as experimental study is to be performed for shell and tube heat exchanger to determine what the effects on various parameters of graphene nanofluid, silver nanofluid, Al2O3 nanofluid and copper nanofluid. Graphite is the cheapest form of producing flanks of graphene and these samples of produced graphene were optimized with help of different type of methods. To increase the performance of heat transfer of shell & tube heat exchanger, the graphene nanofluid is used as a working fluid rather than any different type of ordinary fluid. The thermal efficiency and the coefficient of heat transfer depend upon the inlet temperature, flow rate, concentration of working fluid. The general outcomes show that by increasing in concentration of nanoparticle and flow rate of working fluids, there will be the increment in heat transfer rate, thermal conductivity and efficiency of heat exchanger.

Unsteady axisymmetric flow and heat transfer of a hybrid nanofluid over a permeable stretching/shrinking disc

PurposeThis study aims to analyze the unsteady flow of hybrid Cu-Al2O3/water nanofluid over a permeable stretching/shrinking disc. The analysis of flow stability is also purposed because of the non-uniqueness of solutions.Design/methodology/approachThe reduced differential equations (similarity) are solved numerically using the aid of bvp4c solver (Matlab). Two types of thermophysical correlations for hybrid nanofluid (Type 1 and 2) are adopted for the comparison results. Using correlation Type 1, the heat transfer and flow analysis including the profiles (velocity and temperature) are presented in the figures and tables with different values control parameters. Three sets of hybrid nanofluid are analyzed: Set 1 (1% Al2O3 + 1% Cu), Set 2 (0.5% Al2O3 + 1% Cu) and Set 3 (1% Al2O3 + 0.5% Cu).FindingsThe comparison of numerical values between present (Types 1 and 2 correlations) and previous (Type 2 correlations) results are in a good compliance with approximate percent relative error. The appearance of two solutions is noticed when the suction parameter is considered and the unsteady parameter is less than 0 (decelerating flow) for both stretching and shrinking disc while only one solution is possible for steady flow. The hybrid nanofluid in Set 1 can delay the separation of boundary layer but the hybrid nanofluid in Set 3 has the greatest heat transfer rate. Moreover, the inclusion of wall mass suction for stretching case can generate a significant increment of heat transfer rate approximately 90% for all fluids (water, single and hybrid nanofluids).Originality/valueThe present findings are novel and can be a reference point to other researchers to further analyze the heat transfer performance and stability of the working fluids.

Effect of suction on the stagnation point flow of hybrid nanofluid toward a permeable and vertical Riga plate

AbstractThe application of appropriate wall mass suction (transpiration) has been reported as the key factor to generate steady solutions in the opposing flow (shrinking or opposing buoyancy). This study features the impact of the suction and mixed convection parameters in the stagnation point flow toward a permeable Riga plate. Due to the capability of hybrid nanofluids in enhancing the heat transfer performance, the combination of copper (Cu) and alumina (Al2O3) nanoparticles are used, including water as the base fluid. It appears that the dual solutions are potential in this problem with the negligence of the suction parameter. However, this transpiration effect is efficient in delaying the separation process of the hybrid nanofluid flow and enhancing the heat transfer rate. The heat transfer rate augments with the addition of and . The increment of heat transfer rate is reported between 34% and 39% when 30% of the suction parameter is applied. Besides, the addition of the mixed convection parameter from the opposing to assisting flow enlarges the velocity profile while reduces the temperature profile. The reduction of temperature distribution with an upsurge of suction, mixed convection, and EMHD parameters implies the operating heat transfer process.

On Aqua-Based Silica (SiO2–Water) Nanocoolant: Convective Thermal Potential and Experimental Precision Evaluation in Aluminum Tube Radiator

Although the research on potential use of nanofluids in automotive vehicles is in its embryonic stage, a number of studies have suggested the strong prospect of nanofluids for the efficient thermal management of automotive vehicles. Nevertheless, the pinnacle of nanofluid-based systems awaits stable nanoparticle suspension. The present work studies the heat transfer performance of an aluminum tube automotive radiator with 31 flattened tubes and louvered fins using water and different concentrations (0.04, 0.08, and 0.12 vol.%)-based SiO2/water nanofluids as the engine coolant. Inlet temperature and flowrate of the fluid were varied from 60 to 70 °C and 12 to 18 LPM, respectively. The topmost increment in heat transfer rate of 36.92% and Nusselt number of 45.53% were observed in the upper range of tested operational parameters, however, the relative heat transfer increment percentage dropped from 5% (between 0.04 and 0.08 vol.%) to 3.5% (between 0.08 and 0.12 vol.%) due to agglomeration and cluster formation caused by the presence of a greater number of nanoparticles. Precise evaluation of the experimental results was also carried out by reperforming the tests after three days of initial experimentations. A mere deviation of less than 1% was observed between the initial and repeated tests, however, the decline was caused due to the synergistic effects of clustering and fouling.

Numerical Study of Heat Transfer Enhancement of Turbulent Flow Using Twisted Tape Insert Fitted with Hemispherical Extruded Surface

Heat transfer enhancement of heat exchangers is an important matter of concern to achieve more effective thermal energy conversion systems. The use of modified twisted tape (TT) inserts as passive technique of heat transfer augmentation are effective way to improve heat transfer. In this study, a numerical analysis is performed to investigate the heat transfer performance enhancement and flow behavior in a circular pipe using TT insert fitted with a hemispherical extruded surface (HES). The study is carried out for the turbulent flow regime (4000�Re�10000) at a twist ratio of 4.0 using ANSYS FLUENT. A flow domain is designed and mathematically modeled applying boundary conditions and using governing equations for turbulent model. The plain tube data is validated with established correlations. The achieved numerical results reveal that for TT fitted with HES leads to increment in heat transfer rate up to 69.4 compared to plain tube due to effective swirl flow and better mixing caused by the insert. Corresponding increase in friction factor is found relative to plain tube. The impact on the thermal performance factor has obtained a maximum of 1.24 at constant pumping power for Reynold number 4000. © 2020 International Information and Engineering Technology Association. All rights reserved.

Assessment of thermo-hydraulic performance of inward dimpled tubes with variation in angular orientations

This paper presents a numerical investigation and assessment of thermal and hydraulic performance of dimpled tubes of varying topologies at constant heat flux of 10kW/m2 and Reynolds numbers ranging from 2300 to 15,000. The performance of the tubes consisting of conical, spherical and ellipsoidal dimples with equivalent flow volumes were compared using steady state Reynolds Averaged Navier Stokes simulations. The ellipsoidal dimples, in comparison to other dimple shapes, demonstrated large increment in heat transfer rate. The variation in the orientation of the ellipsoidal dimples was examined to further improve thermal and hydraulic performances of the tube. A 45° inclination angle of ellipsoidal dimple, from its major axis, increased the thermo-hydraulic performance by 58.1% and 20.2% in comparison to smooth tube and 0° ellipsoidal dimpled tube, respectively. Furthermore, Large Eddy Simulations (LES) were carried out to investigate the role geometrical assistance to fluid flow and heat transfer enhancement for the 45° and 90° ellipsoidal dimpled tubes. LES results revealed a flow channel of connected zones of wakes which maximized fluid-surface contact and therefore enhanced the thermal performance of the tube. In addition, correlations for Nusselt number and friction factor for all angular topologies of ellipsoidal dimpled tube have been proposed.

Thermal and hydraulic characteristics of a minichannel heat exchanger operated with a non-Newtonian hybrid nanofluid

Abstract In this study, thermal and hydraulic characteristics of a non-Newtonian hybrid nanofluid are investigated in a double-tube minichannel heat exchanger. The nanofluid contains two different nanoparticles, namely Tetra Methyl Ammonium Hydroxide (TMAH) coated Fe3O4 nanoparticles and Gum Arabic (GA) coated Carbon Nanotubes (CNTs). The nanofluid and water flow in the tube side and annulus side of the heat exchanger, respectively. Variable thermal conductivity and viscosity are applied in the simulations. Numerical solutions are performed based on both Reynolds number and mass flow rate, and the heat transfer rate in the heat exchanger, overall heat transfer coefficient, effectiveness, pressure drop, pumping power, and performance index are evaluated under different conditions. The results show that adding the nanoparticles causes a further increment in heat transfer rate at lower Reynolds numbers, such that the increase in heat transfer rate of the nanofluid compared with water at Reynolds numbers 500 and 2000 is 53.8% and 28.6%, respectively. The findings obtained show a promising view for use of this hybrid ferrofluid in mini heat exchangers.