Evaluation of bend curvature of superheater tube using CFD analysis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sushovan Chatterjee ◽  
Subhasish Das ◽  
Neelam Kumar Sarma
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Flow Behavior ◽  
Radius Of Curvature ◽  
Pass System ◽  
Maximum Heat ◽  
Curvature Ratio ◽  
Content Type ◽  
Superheater Tube ◽  
The Impact

Purpose The heat transfer within a heat exchanger is highly influenced by geometry of the components especially those with hollow structures like tubes. This paper aims to intend toward the study of efficient and optimized heat transfer in the bends of superheater tubes, with different curvature ratio at constant Reynolds Number. Design/methodology/approach The effect of changing curvature ratio on enthalpy of the fluid passing through the superheater tubes for multi-pass system has been studied with the aid of computational fluid dynamics (CFD) using ANSYS 14.0. Initially a superheater tube with two pass system has been examined with different curvature ratios of 1.425, 1.56, 1.71, 1.85 and 1.99. An industry specified curvature ratio of 1.71 with two pass is investigated, and a comparative assessment has been carried out. This is intended toward obtaining an optimized radius of curvature of the bend for enhancement of heat transfer. Findings The results obtained from software simulation revealed that the curvature ratio of 1.85 provides maximum heat transfer to the fluid flowing through the tube with two pass. This result has been found to be consistent with higher number of passes as well. The effect of secondary flow in bends of curvature has also been illustrated in the present work. Research limitations/implications The study of heat transfer in thermodynamic systems is a never-ending process and has to be continued for the upliftment of power plant performances. This study has been conducted on steady flow behavior of the fluid which may be upgraded by carrying out the same in transient mode. The impact of different curvature ratios on some important parameters such as heat transfer coefficients will certainly upgrade the value of research. Originality/value This computational study provided comprehensive information on fluid flow behavior and its effect on heat transfer in bends of curvature of superheater tubes inside the boiler. It also provides information on optimized bend of curvature for efficient heat transfer process.

A comprehensive survey on utilization of hybrid nanofluid in plate heat exchanger with various number of plates

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faraz Afshari ◽  
Azim Doğuş Tuncer ◽  
Adnan Sözen ◽  
Halil Ibrahim Variyenli ◽  
Ataollah Khanlari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Flow Behavior ◽  
Plate Heat Exchanger ◽  
Single Type ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Plate Heat ◽  
The Impact

Purpose Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat exchangers. Different types of nanofluids are available and used in different applications. The main purpose of this study is to investigate the effects of using hybrid nanofluid and number of plates on the performance of plate heat exchanger. In this study, TiO2/water single nanofluid and TiO2-Al2O3/water hybrid nanofluid with 1% particle weight ratio have been used to prepare hybrid nanofluid to use in plate type heat exchangers with three various number of plates including 8, 12 and 16. Design/methodology/approach The experiments have been conducted with the aim of examining the impact of plates number and used nanofluids on heat transfer enhancement. The performance tests have been done at 40°C, 45°C, 50°C and 55°C set outlet temperatures and in five various Reynolds numbers between 1,600 and 3,800. Also, numerical simulation has been applied to verify the heat and flow behavior inside the heat exchangers. Findings The results indicated that using both nanofluids raised the thermal performance of all tested exchangers which have a various number of plates. While the major outcomes of this study showed that TiO2-Al2O3/water hybrid nanofluid has priority when compared to TiO2/water single type nanofluid. Utilization of TiO2-Al2O3/water nanofluid led to obtaining an average improvement of 7.5%, 9.6% and 12.3% in heat transfer of heat exchangers with 8, 12 and 16 plates, respectively. Originality/value In the present work, experimental and numerical analyzes have been conducted to investigate the influence of using TiO2-Al2O3/water hybrid nanofluid in various plate heat exchangers. The attained findings showed successful utilization of TiO2-Al2O3/water nanofluid. Based on the obtained results increasing the number of plates in the heat exchanger caused to obtain more increment by using both types of nanofluids.

Investigation of the effects of geometrical parameters, eccentricity and perforated fins on natural convection heat transfer in a finned horizontal annulus using three dimensional lattice Boltzmann flux solver

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahyar Ashouri ◽  
Mohammad Mehdi Zarei ◽  
Ali Moosavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Lattice Boltzmann ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Maximum Heat ◽  
Content Type ◽  
Dimensional Lattice ◽  
Fin Spacing

Purpose The purpose of this paper is to investigate the effects of geometrical parameters, eccentricity and perforated fins on natural convection heat transfer in a finned horizontal annulus using three-dimensional lattice Boltzmann flux solver. Design/methodology/approach Three-dimensional lattice Boltzmann flux solver is used in the present study for simulating conjugate heat transfer within an annulus. D3Q15 and D3Q7 models are used to solve the fluid flow and temperature field, respectively. The finite volume method is used to discretize mass, momentum and energy equations. The Chapman–Enskog expansion analysis is used to establish the connection between the lattice Boltzmann equation local solution and macroscopic fluxes. To improve the accuracy of the lattice Boltzmann method for curved boundaries, lattice Boltzmann equation local solution at each cell interface is considered to be independent of each other. Findings It is found that the maximum heat transfer rate occurs at low fin spacing especially by increasing the fin height and decreasing the internal-cylindrical distance. The effect of inner cylinder eccentricity is not much considerable (up to 5.2% enhancement) while the impact of fin eccentricity is more remarkable. Negative fin eccentricity further enhances the heat transfer rate compared to a positive fin eccentricity and the maximum heat transfer enhancement of 91.7% is obtained. The influence of using perforated fins is more considerable at low fin spacing although some heat transfer enhancements are observed at higher fin spacing. Originality/value The originality of this paper is to study three-dimensional natural convection in a finned-horizontal annulus using three-dimensional lattice Boltzmann flux solver, as well as to apply symmetry and periodic boundary conditions and to analyze the effect of eccentric annular fins (for the first time for air) and perforated annular fins (for the first time so far) on the heat transfer rate.

Natural Convection Heat Transfer in a Partially Open Square Cavity With a Thin Fin Attached to the Hot Wall

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Abdullatif Ben-Nakhi ◽  
M. M. Eftekhari ◽  
D. I. Loveday
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Inclination Angle ◽  
Computational Study ◽  
Vertical Wall ◽  
Temperature Fields ◽  
Arbitrary Length ◽  
Flow Modification ◽  
The Impact

A computational study of steady, laminar, natural convective fluid flow in a partially open square enclosure with a highly conductive thin fin of arbitrary length attached to the hot wall at various levels is considered. The horizontal walls and the partially open vertical wall are adiabatic while the vertical wall facing the partial opening is isothermally hot. The current work investigates the flow modification due to the (a) attachment of a highly conductive thin fin of length equal to 20%, 35%, or 50% of the enclosure width, attached to the hot wall at different heights, and (b) variation of the size and height of the aperture located on the vertical wall facing the hot wall. Furthermore, the study examines the impact of Rayleigh number (104⩽Ra⩽107) and inclination of the enclosure. The problem is put into dimensionless formulation and solved numerically by means of the finite-volume method. The results show that the presence of the fin has counteracting effects on flow and temperature fields. These effects are dependent, in a complex way, on the fin level and length, aperture altitude and size, cavity inclination angle, and Rayleigh number. In general, Nusselt number is directly related to aperture altitude and size. However, after reaching a peak Nusselt number, Nusselt number may decrease slightly if the aperture’s size increases further. The impact of aperture altitude diminishes for large aperture sizes because the geometrical differences decrease. Furthermore, a longer fin causes higher rate of heat transfer to the fluid, although the equivalent finless cavity may have higher heat transfer rate. In general, the volumetric flow rate and the rate of heat loss from the hot surfaces are interrelated and are increasing functions of Rayleigh number. The relationship between Nusselt number and the inclination angle is nonlinear.

Large-Eddy Simulations of Heat Transfer Within a Multi-Perforation Synthetic Jets Configuration

2019 ◽  
Author(s):  
Soizic Esnault ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Synthetic Jets ◽  
Large Eddy Simulations ◽  
Heated Plate ◽  
Piston Displacement ◽  
Large Eddy ◽  
Grazing Flow ◽  
The Impact ◽  
Ejection Phase

Abstract Synthetic jets are produced by devices that enable a suction phase followed by an ejection phase. The resulting mean mass budget is hence null and no addition of mass in the system is required. These particular jets have especially been considered for some years for flow control applications. They also display features that can become of interest to enhance heat exchanges, for example for wall cooling issues. Synthetic jets can be generated through different mechanisms, such as acoustics by making use of a Helmholtz resonator or through the motion of a piston as in an experience mounted at Institut Pprime in France. The objective of this specific experiment is to understand how synthetic jets can enhance heat transfer in a multi-perforated configuration. As a complement to this experimental set up, Large-Eddy Simulations are produced and analysed in the present document to investigate the flow behavior as well as the impact of the synthetic jets on wall heat transfer. The experimental system considered here consists in a perforated heated plate, each perforation being above a cavity where a piston is used to control the synthetic jets. Placed in a wind tunnel test section, the device can be studied with a grazing flow and multiple operating points are available. The one considered here implies a grazing flow velocity of 12.8 m.s−1, corresponding to a Mach number around 0.04, and a piston displacement of 22 mm peak-to-peak at a frequency of 12.8 Hz. These two latter parameters lead to a jet Reynolds number of about 830. A good agreement is found between numerical results and experimental data. The simulations are then used to provide a detailed understanding of the flow. Two main behaviours are found, depending on the considered mid-period. During the ejection phase, the flow transitions to turbulence and the formation of characteristic structures is observed; the plate is efficiently cooled. During the suction phase the main flow is stabilised; the heat enhancement is particularly efficient in the hole wakes but not between them, leading to a heterogeneous temperature field.

Effects of Heat Transfer on the Spreading and Freezing of Molten Droplets Impinging Onto Textured Surfaces: A Computational Study

2012 ◽  
Author(s):  
Mehdi Raessi ◽  
Rajkamal Sendha
Keyword(s):  
Heat Transfer ◽  
Impact Velocity ◽  
Computational Study ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Textured Surfaces ◽  
Molten Droplets ◽  
Energy Equations ◽  
The Impact ◽  
Obstacle Height

We present our recent study on spreading and solidification of micro-droplets of alumina impacting onto patterned surfaces textured by micron-size obstacles. We employed an in-house, three-dimensional computational tool that solves the flow and energy equations and takes into account the solidification. We investigated the spreading dynamics, heat transfer, and solidification of the droplets as a function of the height and spacing of the obstacles as well as the impact velocity. The results show that, independent of the obstacle height, the droplet assumes a disk-shape geometry when the obstacles are either packed tightly or are very distanced. The results at intermediate obstacle spacings exhibit the most significant deformations, where the droplet develops long fingers. A quantitative relationship shows the collapse of the final spread diameter of the droplet normalized by the obstacle spacing when plotted against the spacing for different impact velocity as well as the obstacle height.

Dufour and Soret effects on Darcy-Forchheimer flow of second-grade fluid with the variable magnetic field and thermal conductivity

2020 ◽  
Vol 30 (9) ◽  
pp. 4331-4347 ◽  
Author(s):  
Ambreen A. Khan ◽  
S. Naeem ◽  
R. Ellahi ◽  
Sadiq M. Sait ◽  
K. Vafai
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Variable Magnetic Field ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Content Type ◽  
Grade Fluid ◽  
The Impact ◽  
Forchheimer Flow

Purpose This study aims to investigate the effect of two-dimensional Darcy-Forchheimer flow over second-grade fluid with linear stretching. Heat transfer through convective boundary conditions is taken into account. Design/methodology/approach Nonlinear coupled governing equations are tackled with a homotopy algorithm, while for numerical computation the computer software package BVPh 2.0 is used. The convergence analysis is also presented for the validation of analytical and numerical results. Findings Valuation for the impact of key parameters such as variable thermal conductivity, Dufour and Soret effects and variable magnetic field in an electrically conducted fluid on the velocity, concentration and temperature profiles are graphically illustrated. It is observed from the results that temperature distribution rises by Dufour number whereas concentration distribution rises by Soret number. The Forchheimer number and porosity parameter raise the skin friction coefficient. The permeable medium has a vital impact and can help in reining the rate of heat transfer. Practical implications The permeable medium has a vital impact and can help in reining the rate of heat transfer. Originality/value To the best of the authors’ knowledge, this study is reported for the first time.

scholarly journals Impact of convection on thermographic analysis of silver based thermal joints

2020 ◽  
Vol 32 (4) ◽  
pp. 241-246
Author(s):  
Krzysztof Jakub Stojek ◽  
Jan Felba ◽  
Johann Nicolics ◽  
Dominik Wołczyński
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Energy Loss ◽  
Thermal Resistance ◽  
Analysis Method ◽  
Content Type ◽  
Heat Transfer Efficiency ◽  
Lowered Pressure ◽  
Thermographic Analysis ◽  
The Impact

Purpose This paper aims to develop thermal analysis method of thermal joints characterization. The impact on convection on thermal resistance analysis with use thermography for silver-based thermal joints were investigated for non-metallized and metalized semiconductor surfaces. Heat transfer efficiency depends on thermal conductivity; radiation was used to perform thermographic analysis; the convection is energy loss, so its removing might improve measurements accuracy. Design/methodology/approach Investigation of thermal joints analysis method was focused on determination of convection impact on thermal resistance thermographic analysis method. Measuring samples placed in vacuum chamber with lowered pressure requires transparent window for infrared radiation that is used for thermographic analysis. Impact of infrared window and convection on temperature measurements and thermal resistance were referred. Findings The results showed that the silicon window allowed to perform thermal analysis through, and the convection was heat transfer mode which create 15% energy loss. Originality/value It is possible to measure thermal resistance for silver-based thermal joints with convection eliminated to improve measurements accuracy.

scholarly journals Slip Effects on Unsteady Oblique Stagnation Point Flow of Nanofluid in a View of Inclined Magnetic Field

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Rizwana Rizwana ◽  
Azad Hussain ◽  
S. Nadeem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Stagnation Point ◽  
Flow Behavior ◽  
Casson Fluid ◽  
Stagnation Point Flow ◽  
Working Fluid ◽  
Petroleum Reservoir ◽  
Metallic Nanoparticle ◽  
The Impact

This study may be applicable in heavy power engine and cooling of a nuclear reactor, insulation for buildings, petroleum reservoir operations, and magnetic material processing solar energy collectors. In this manuscript, the slip results are evaluated for the non-Newtonian fluid on the oblique stagnation point flow of induced magnetic field over the oscillating surface. The valuation of heat flux is examined through the Fourier law of heat transfer. The metallic nanoparticle Copper Cu is within the base fluid, and water is utilized in the analysis. Nanofluids have benefits such as steadiness of the working fluid, decreasing blockage, clogs, decreasing prices, decreasing the friction coefficient, and decreasing the size of the heat transfer system. Similarity variables are utilized to convert the developed flow into higher nonlinear coupled ordinary differential equations (ODE) which are tackled numerically using a mathematical technique such as the bvp4c method in Maple and Matlab software. According to the present geometry, the flow behavior of the operating nanofluid has analyzed by stream lines. Disparities in velocity and temperature profile are demonstrated by graphs to describe the effects of controlling parameters. The Casson fluid parameter enhances the velocity of the fluid. The system heats up by the impact of Joule heating and dissipation.

Effect of fin and tube configuration on heat transfer of an internally finned tube

2015 ◽  
Vol 25 (8) ◽  
pp. 1978-1999 ◽  
Author(s):  
Kailash Mohapatra ◽  
Dipti Prasad Mishra
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Transfer Rate ◽  
Flow Characteristics ◽  
Finned Tube ◽  
Maximum Heat ◽  
Content Type ◽  
Maximum Heat Transfer ◽  
Internally Finned Tube ◽  
Fluid Flow Characteristics

Purpose – The purpose of this paper is to determine the heat transfer and fluid flow characteristics of an internally finned tube for different flow conditions. Design/methodology/approach – Numerical investigation have been performed by solving the conservation equations of mass, momentum, energy with two equation-based k-eps model to determine the wall temperature, outlet temperature and Nusselt number of an internally finned tube. Findings – It has been found from the numerically investigation that there exists an optimum fin height and fin number for maximum heat transfer. It was also found that the heat transfer in T-shaped fin was highest compared to other shape. The saw type fins had a higher heat transfer rate compared to the plane rectangular fins having same surface area and the heat transfer rate was increasing with teeth number. Keeping the surface area constant, the shape of the duct was changed from cylindrical to other shape and it was found that the heat transfer was highest for frustum shape compared to other shape. Practical implications – The present computations could be used to predict the heat transfer and fluid flow characteristics of an internal finned tube specifically used in chemical and power plants. Originality/value – The original contribution of the paper was in the use of the two equation-based k-eps turbulent model to predict the maximum heat transfer through optimum design of fins and duct.

Nonhomogeneous model for conjugate mixed convection of nanofluid and entropy generation in an enclosure in presence of inclined magnetic field with Joule heating

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Subhasree Dutta ◽  
Somnath Bhattacharyya ◽  
Ioan Pop
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Joule Heating ◽  
Conjugate Heat Transfer ◽  
Inclined Magnetic Field ◽  
Content Type ◽  
The Impact ◽  
The Magnetic Field

Purpose This study aims to numerically analyse the impact of an inclined magnetic field and Joule heating on the conjugate heat transfer because of the mixed convection of an Al2O3–water nanofluid in a thick wall enclosure. Design/methodology/approach A horizontal temperature gradient together with the shear-driven Flow creates the mixed convection inside the enclosure. The nonhomogeneous model, in which the nanoparticles have a slip velocity because of thermophoresis and Brownian diffusion, is adopted in the present study. The thermal performance is evaluated by determining the entropy generation, which includes the contribution because of magnetic field. A control volume method over a staggered grid arrangement is adopted to compute the governing equations. Findings The Lorentz force created by the applied magnetic field has an adverse effect on the flow and thermal field, and consequently, the heat transfer and entropy generation attenuate because of the presence of magnetic force. The Joule heating enhances the fluid temperature but attenuates the heat transfer. The impact of the magnetic field diminishes as the angle of inclination of the magnetic field is increased, and it manifests as the volume fraction of nanoparticles is increased. Addition of nanoparticles enhances both the heat transfer and entropy generation compared to the clear fluid with enhancement in entropy generation higher than the rate by which the heat transfer augments. The average Bejan number and mixing-cup temperature are evaluated to analyse the thermodynamic characteristics of the nanofluid. Originality/value This literature survey suggests that the impact of an inclined magnetic field and Joule heating on conjugate heat transfer based on a two-phase model has not been addressed before. The impact of the relative slip velocity of nanoparticles diminishes as the magnetic field becomes stronger.

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