Abstract The emission characteristics of non-premixed impinging flames are investigated using PIV experiments and numerical simulations. Different coflow conditions are conducted to focus on the pollutant emissions with the flame-wall interaction. Results show that flame dynamics obtained from experiments are in good agreement with that calculated from numerical simulations, and flame instability is

Abstract A two-dimensional model is proposed for energy efficiency assessment through the simulation of heat transfer in building envelopes, considering the influence of the surrounding environment. The model is based on the Du Fort–Frankel approach that provides an explicit scheme with a relaxed stability condition. The model is first validated using an analytical solution and then compared to three

Abstract To reasonably select the process parameters of the double cone specimen (DCS) during hot compression, the temperature field evolution in the resistant furnace during the heating stage of hot compression was analyzed by numerical and experimental methods. The results show that there is a significant temperature gradient between surface and center of the specimen during the heating stage, the

Abstract Biomimetics is the imitation of the systems, models, and nature elements for the motive of elucidating complex biological problems. In the current century, the use of nanoparticles in the treatment of biological systems (such as cancer and atherosclerosis treatment) is common in worldwide due to many properties of nanoparticles. In general, the size of nanoparticles are very small so that

Abstract The relevance of thermal ablation in cancer treatment is growing through the years, because it involves fewer complications, a shorter hospital stays, and less costs. In this article, the effects of different antennas configurations in thermal ablation are investigated. Single, double, and triple antennas configurations are modeled in order to simulate the hepatic cancer treatment, which often

Abstract In this work, a fast and efficiently design method has been introduced. This design process consists of the overall design and the detailed design. For the overall design, one-dimensional pipe-network computations are employed to obtain several design cases quickly at the beginning. Meanwhile the solid domain geometry and mesh with cooling structures, i.e., film holes, impingement holes, and

Abstract An attempt is made to improve the overall performances of channel heat exchangers. The techniques of baffles and nanofluids are combined to enhance the dynamic and thermal behaviors within the channel exchanger. Baffles under various attack angles are used as vortex generators. In addition, oil/multiwalled carbon nanotubes (MWCNT) is used as a working fluid. Both inclinations in the upstream

Abstract This numerical study performed the three-dimensional simulations to explore the turbulent thermal flow characteristics over the heated blocks inside a square channel by a slotted ribbed plate through the RNG κ − ε turbulence model and SIMPLE-C algorithm. The influence of slotted ribbed plate on the enhancement of turbulent heat transfer from these heated block surfaces would be evaluated through

Abstract Dropwise condensation on rough surfaces enhanced with pillars in the presence of non-condensable gas (NCG) including the initial nucleation process is simulated using the multispecies multiphase lattice Boltzmann method, and the effect of mass fraction of NCG, the surface wettability, the bottom wall temperature and the geometrical parameter (the pillar height H) on condensation process are

Abstract A comprehensive numerical study is performed on a vertical hollow cylinder of finite thickness for natural convection with surface radiation effect. The prime aim is to find out the heat transfer rate due to both natural convection and radiation from both the inner and outer walls of the tube. Also, an attempt is made to estimate the cooling time, the time required to bring down the cylinder

Abstract Thermal analysis of heat-generating battery pack cooled by several coolants is analyzed numerically. The coolant used are gases, oils, thermal oils, nanofluids, and liquid metals to find the best coolant for temperature distribution. The conductivity ratio between the battery and coolant, flow Reynolds number, and heat generation inside the pack is varied for each coolant. The axial temperature

Abstract In this study, numerical simulations of the interaction between supersonic crossflow and a side liquid jet were performed. The processes of the liquid jet breakup, flow separation and shock waves resulting from the interaction of the gas flows and liquid droplets were predicted. In the numerical simulation, a two-way coupling Eulerian-Lagrangian method was used. The two-dimensional unsteady

Abstract In this study, turbulent flows and the associated mixing characteristics are numerically investigated for noncircular jets. The selected nozzle shapes are round, square, and equilateral triangular, and a passive scalar is adopted to quantify the flow mixing. To achieve a constant mass flow rate, the same cross-sectional area is maintained, and the Reynolds stress model (RSM) is applied to

Abstract The present study investigates the performance of selected turbulence models to predict the temperature distribution and eddy viscosity ratio in a horizontal direct-chill casting. The turbulence models include the velocity variance–elliptic relaxation ( v 2 ¯ − f ), the kinetic energy-specific dissipation rate shear stress transport (k-ω SST), standard kinetic energy dissipation rate (k-ε)

Abstract Water management is crucial to the performance of proton exchange membrane fuel cells (PEMFC). In this work, a pore-scale model is developed based on lattice Boltzmann (LB) method for the simulation of multicomponent multiphase reactive transport in an operating PEMFC, with the aim to capture the water vapor generation, condensation, and subsequent transport in the entire porous cathode, including

Abstract A numerical investigation was conducted to determine the effects of fin shape on heat transfer coefficients during in-tube condensation of R410A. Four micro-fin tubes of different geometries were selected for this study, including a straight-finned one and three helical tubes, and two different helical angles of 18° and 31° were included to explore the influence of helical angles. The numerical

Abstract The present study numerically examines the impact of zigzag fin surface pattern structures in a micro-channel heat exchanger on heat transfer efficiency using a commercial computational fluid dynamics program. The three newly designed louvered fin structures that comprise four triangular zigzag patterns, alternately spaced structures on both fin sides, a flat or zigzag fin structure on either

Abstract The phenomena of buoyant Marangoni natural convection in a right-angled trapezoidal enclosure filled with water-based nanofluids have been studied numerically. The left vertical wall of the trapezoidal cavity is heated uniformly, the right inclined wall is cooled, and the top and bottom walls are insulated (adiabatic). The finite element method (FEM) is implemented to solve the non-dimensional

(2020). Correction. Numerical Heat Transfer, Part A: Applications: Vol. 78, No. 11, pp. I-I.

Abstract The structural optimization of a specific laminated cooling structure is conducted under gas turbine combustor representative aero-thermal conditions, with the aim at improving its overall cooling effectiveness. The optimization procedure is realized by using conjugate heat transfer CFD analysis and radial basis function neural network (RBFNN) surrogated model. For this specific laminated

Abstract Endwall film cooling upstream of the leading edge (LE) of a vane presents a relatively complex flow phenomenon due to the horseshoe vortices (HVs) generated at the LE region. Upstream of the LE region, the coolant flow has difficulties to eject out. This research work focuses on controlling the jet holes coolant coverage upstream of the LE region. Compound angle holes in staggered arrangement

Abstract An experimental investigation was conducted to evaluate heat transfer performance of several enhanced surface tubes during in-tube evaporation and condensation of R410A; results were then compared to the results of a smooth tube. Tubes considered in this evaluation included: smooth; herringbone and helix micro-grooves; herringbone-dimple and hydrophobic; all the tubes evaluated have the same

Abstract Conjugate natural convection heat transfer inside a differentially heated square cavity having a heat conducting and sinusoidal corrugated solid partition has been investigated numerically in the present study. The fluid flow and the heat transfer within the cavity are governed by two-dimensional Navier–Stokes and energy equations, and those are solved using the finite element method. Numerical

Abstract Development of computationally efficient modeling techniques for thermally driven buoyant flows remains an ongoing challenge for the computational fluid dynamics (CFD) community due to the complex interactions of buoyancy, heat transfer, and turbulence. Although several “best practice” guides are available for certain scenarios, comprehensive validation studies against benchmark-quality data

Abstract Provided are numerically predicted distributions of film cooling effectiveness for single cylinder film holes and for single 15° forward diffused film cooling holes, with compound angles ranging from 0° to 180°. Hole inclination angle, with respect to the test surface, is 35° for all arrangements considered, and blowing ratios of 0.60 and 1.25 are used. Also presented are local flow secondary

Abstract In this article, the effects of convex dimple streamwise arrangements on the flow and heat transfer characteristics of protrusion-grooved channels are determined, and five streamwise positions of convex dimples are considered. In addition, research on the transverse-circular-protrusion-grooved channel is also performed to serve as a contrast. The results indicate that replacing the transv

Abstract Heat and fluid flow trajectories are visualized during natural convection subjected to linear heating of the inclined walls involving two representative inclination angles ( φ = 45 ° and φ = 60 ° ) for different configurations (configurations 1 − 3) of the porous isosceles triangles. Heat transport to the core and cold section of inclined walls due to linear heating is studied using heatlines

Abstract We present a numerical model for the simulation of continuous impingement freezing of processed food products. This model is capable of fully describing the fluid dynamics of the non-isothermal flow field, including turbulence with conjugate heat transfer (CHT). The motion of the solid region is captured by advecting the solid rathe than employing a moving mesh algorithm, resulting in a model

The influence of surface radiation on the transition to the unsteady state in natural convection is studied numerically. The configuration of the differentially heated square cavity with adiabatic horizontal walls is chosen to generate an internal natural convection flow. It is known that radiative transfers reduce the temperature difference between the adiabatic walls, which consequently reduces the

In this study, we present a novel fixed-grid interface-tracking method using finite volume method to simulate multidimensional rapid solidification (RS) of under-cooled pure metal. The discretized advection equation for solid fraction function is solved using the THINC/WLIC method, which is a VOF method. The governing equations for fluid flow are solved numerically using pressure-velocity coupling

In this study, the wetting states and wetting transition of droplets on the microstructured surfaces are investigated using the multiphase lattice Boltzmann method. The Cassie-Baxter (Cassie) and Wenzel wetting states on the rough surfaces are captured through the simulations, and the stability of Cassie state and the wetting transition are then studied and discussed by simulating the evaporation of

Combined with infrared thermography experiments, large-eddy simulation was used for studying trench film cooling on C3X vane model at the mainstream Reynolds number of 2.5 × 105 based on the chord length, and nominal blowing ratios of 0.5 and 1.5. The instantaneous and time-averaged characteristics for trench film cooling were analzyed in detail. Inside the trench, a pair of recirculation vortices

Abstract The nanofluid forced convection heat exchange in a porous channel within three heated blocks was numerically investigated using the Nonorthogonal multiple-relaxation time lattice Boltzmann method (MRT-LBM). The effects of various parameters such as nanoparticle volume fraction (ϕ), Darcy number (Da) on heat exchange performance and flow phenomena were analyzed when the Pecklel number (Pe)

Abstract We describe a methodology able to extract the regimes of operation from condensing heat exchanger data. The methodology applies a Gaussian mixtures clustering algorithm to determine the number of groups directly from the data, and a maximum likelihood decision rule to classify such data into these clusters. Published measurements visually classified as dry-surface, dropwise condensation, and

Abstract This study investigates the internal cooling processes affected by the tip bleed holes in gas turbine blades. Double bleed holes are fixed at the center of the blade tip near the pressure side and suction side, respectively. Five different arrangements of the holes along the center line of the tip are studied. The purely double holes are set as the Baseline. The purpose of the present study

Abstract The main objective of this paper is to numerically investigate the transient forward and backward thermocapillary motion of a water droplet in a microchannel occupied by the hexadecane oil. The top and bottom walls of the microchannel are kept at the ambient temperature. Two heat sources activated periodically are put on the front side and rear one of the droplet in a microchannel, respectively

Abstract Provided are numerically predicted flow structural data for a flow passage with an impingement jet array, as well as numerically predicted surface Nusselt number data for the target surface of the passage, which are obtained using a SST k−ω turbulence closure model. The closure model and numerical prediction approach are validated by oil film flow visualization experimental results. Spatially

Abstract Microrib is a promising structural optimization method proposed in heat transfer research project of scramjet regenerative cooling channels. In this article, a new type of boot-shaped microribs was designed to enhance the heat transfer performance in mini cooling channels for transcritical n-Decane. Response Surface Methodology (RSM) and Multi-objective Genetic Algorithm (MOGA) were utilized

This article developed a novel numerical model for accurately predicting the thermal performance of fin-and-tube condenser, which coupled heat transfer between the air and refrigerant side. The heat exchange calculation between the air and refrigerant side was alternatively performed by coupling the tube wall temperatures. Meanwhile, the air side flow and heat transfer characteristics among the fin

The understanding of the convective heat transfer process for fluid flows through nanochannels becomes imperative due to the wide application of the micro/nanochannel cooling technology. In this work, thermal and flow characteristics in nanochannels with tunable surface wettability are investigated systematically using the molecular dynamics method. First, different temperature and velocity distributions

In the present work, numerical study on the buoyancy induced flow and heat transfer around a hollow horizontal cylinder with finite wall thickness either suspended in air or placed on ground has been performed. The effects of the Rayleigh Number (103 ≤ Ra ≤ 107), length to outer diameter ratio (0.1≤L/D ≤ 20) and the thickness ratio (0.4≤d/D ≤ 0.9) of the cylinder have been studied. The effect of the

The effect of pulsating flow on the heat transfer inside a dimpled surface is numerically investigated. It has been found that, at Reynolds number of 300, the flow unsteadiness can largely alter the vortex dynamics inside the dimple. Typically, the vortex core is initiated close to the leading edge of the dimple. As the vortex bubble grows, a dual-core vortical flow structure appears due to the strong

This article proposes two new turbulence models for steady-state and transient-state solutions. For the steady-state solution, by introducing the streamline curvature factor and response threshold value into the low Reynolds number (LRN) k-ε model, a modified LRN k-ε model is obtained, which is applied to simulate an automobile flow-field by Fluent solver. The comparisons among the results obtained

To study the heat transfer of pipe cooling process in concrete, an effective model combined with a radial basis function collocation method (RBFCM) is proposed. In this model, a replicable fictitious structure is imported that allows a set of fixed points to supersede the complicated adaptive remeshing or redistributing points, which significantly saves a lot of time and effort in the pre-processing

Abstract To study the heat transfer of pipe cooling process in concrete, an effective model combined with a radial basis function collocation method (RBFCM) is proposed. In this model, a replicable fictitious structure is imported that allows a set of fixed points to supersede the complicated adaptive remeshing or redistributing points, which significantly saves a lot of time and effort in the pre-processing

Abstract This article proposes two new turbulence models for steady-state and transient-state solutions. For the steady-state solution, by introducing the streamline curvature factor and response threshold value into the low Reynolds number (LRN) k-ε model, a modified LRN k-ε model is obtained, which is applied to simulate an automobile flow-field by Fluent solver. The comparisons among the results

Abstract We develop a two-phase flow model for solving the nonlinear level set (LS) equation and Navier-Stokes equations in two dimension. In the proposed one-step LS method, the sharp interface is captured by implicitly representing the zero LS contour. The nonlinear LS equation is solved by upwinding Combined Compact Difference (CCD) scheme for the convection terms and center difference scheme for

An experimental investigation was conducted to evaluate heat transfer performance of several enhanced surface tubes during in-tube evaporation and condensation of R410A; results were then compared to the results of a smooth tube. Tubes considered in this evaluation included: smooth; herringbone and helix micro-grooves; herringbone-dimple and hydrophobic; all the tubes evaluated have the same external

Abstract Corneal opacity is a leading cause of blindness, accounting for about 4% of global blindness. With corneal opacity, light is unable to pass through the cornea to form a clear image on the retina, resulting in blindness. To address this condition, an intraocular projection device has been designed. This device, while in use, would produce heat. According to international standard regulations

Abstract Three different types of axially nonuniform heat fluxes are imposed on the outer surface of a vertical circular tube with turbulent supercritical carbon dioxide (S-CO2) flowing upward. The aim is to explore the potential in adjusting the axial heat flux distribution to optimize heat transfer. Numerical simulations are conducted to investigate how varying the heat flux in the axial direction

Abstract In this article, the effects of convex dimple streamwise arrangements on the flow and heat transfer characteristics of protrusion-grooved channels are determined, and five streamwise positions of convex dimples are considered. In addition, research on the transverse-circular-protrusion-grooved channel is also performed to serve as a contrast. The results indicate that replacing the transv

This article aims to explore the effects of buoyancy force and thermal boundary condition on the mixed convection heat transfer performance of air in a horizontal microchannel. Three different heat flux models, including bottom wall heated, top wall heated (single wall heating – a novel heating approach compared to recent studies) and both walls heated, are analyzed at four different values of the

Magnesium/polytetrafluoroethylene/Viton (MTV) fuel-rich pyrolants use the atmospheric oxygen as a complementary oxidizer to sustain and alter the performance of the combustion reaction. The flame diffusion characteristics of MTV fuel-rich pyrolants in the atmospheric environment are studied by a high-speed camera (HSC). The flame temperature and combustion components are measured by using remote sensing

The strong variation of thermophysical properties of working fluids operating in the vicinity of the critical point makes this thermodynamic domain attractive to several energy applications. Therefore, herein a two-dimensional numerical method is used to investigate the effect of local thermophysical property variations on the local and overall thermal performance of internal convective heat transfer

Abstract In the present work, a test facility has been set up to observe direct water–air interaction with and without a cellulose cooling pad. Volumetric heat and mass transfer coefficients have been introduced to understand air–water interaction so that contact volume between air and water with and without pad can be used as an effective parameter in the analysis. Experimental values of these parameters

Abstract Non-isothermal melting phenomenon widely exists in phase change process where mixtures are utilized as phase change materials. It is in the mushy zone that phase transition actually occurs during the melting process. Thus, an in-depth understanding of flow and heat transfer in the mushy zone can provide beneficial ways to improve melting technologies. This article focuses on the evolution

Abstract Heat and flow characteristics of V-shaped protrusion/concavity combination with 45 ° miniature V-rib has been investigated numerically at flow Reynolds number of 50,000. With suitable baseline studies, a total of six different configurations viz. (a) V-rib only, (b) ‘V-rib and V-protrusion’, (c) ‘V-rib and V-concavity’, (d) V-protrusion only, (e) V-concavity only, (f) Sparse V-rib, were studied

Abstract A novel domain propulsion and adaptive modified inversion method based on the least square error method and the precise integration finite element method is firstly proposed to identify the geometries of two-dimensional and three-dimensional models made of functional gradient materials. After introducing concept of virtual boundary, the inverse geometry problems can be solved only by the two

Abstract This article presents a model for investigating the thermo- and fluid-dynamical behaviors of liquid carbon dioxide (LCO2) in pulverized coal, which is coupling of phase transition, multiphase flow, heat and mass transfer. In the model, the intensive non-isothermal effect caused by phase transition during the injection process is considered as a negative heat source associated with transient

The bubble dynamics and their effects on flow boiling heat transfer in a horizontal channel are investigated under constant wall temperature and constant wall heat flux conditions. It is found that both the bubble departure time and departure diameter decrease with increasing the inertial force for all the considered heating modes. Moreover, the bubble departs from the heater with a residual for the