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

(2020). Correction. Numerical Heat Transfer, Part A: Applications. Ahead of Print.

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

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), the Prandtl

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 film condensation

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 is to provide

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. When

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 averaged

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 results

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 to optimize

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 governing

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

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 the other

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

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, the temperature

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 influences

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

Non-premixed hydrogen flame is solved to investigate turbulent transport characteristic using direct numerical simulation with768 computing cores. Local and statistical transport behaviors are observed in nonbuoyant and buoyant flames. The absence of buoyancy results in a simplified flow field which can serve as a “cheaner” test to provide an improved understanding of transport process and assess the

Conjugate heat transfer analysis of liquid metal turbulent flow through a horizontal channel has been numerically studied using a large eddy simulation (LES) technique. The effect of wall thickness and heat conduction in the wall on flow and thermal characteristics of low Prandtl number liquid metals has been investigated and reported here. Results are presented for three different liquid metal flows

The ground electrode of spark plugs are assembled to a steel shell through a resistance braze-welding technique. Two types of currents can be used in that aim: AC or DC. Based on the current type, two different kinds of models were built. The first one is a 3-D magnetodynamic-thermal model, specially suited for AC current. The magnetodynamic and thermal FE analyses are weakly coupled to calculate the

Because of the effects of the nanostructure, phase change behaviors on flat and nanostructured surfaces display distinct features. In this work, the molecular dynamics simulation method is employed to investigate the onset temperature of explosive boiling (Ts) with various film thicknesses, pillar heights, and wettability. The simulation results show that Ts decreases with the film thickness on both

Conjugate heat transfer analysis of liquid metal turbulent flow through a horizontal channel has been numerically studied using a large eddy simulation (LES) technique. The effect of wall thickness and heat conduction in the wall on flow and thermal characteristics of low Prandtl number liquid metals has been investigated and reported here. Results are presented for three different liquid metal flows

This study examined the effects of an inclined elliptical cylinder on mixed convection in a square enclosure at three different Reynolds numbers, Re = 100, 500, and 1,000, and a fixed Grashof number of Gr = 105. The effects of the inclined angle of the elliptical cylinder (0° ≤ ϕ ≤ 180°) and aspect ratio on mixed convection were also analyzed by the distribution of the isotherms, streamlines, and the

The cladding layer formed by laser cladding is formed by solidification of the molten pool. The quality of the cladding layer is directly determined by the evolution of the molten pool. The numerical simulation of the evolution of the molten pool is carried out, revealing the relationship between different powers and the evolution of the molten pool. The results show that the volume of the molten pool

In the present article, a new surface treatment is proposed for pool boiling enhancement. For this purpose, a combination of hydrophilic–hydrophobic micropillar arrays with hydrophilic insulation strips between them is used to control and manage the thin film evaporation, surface rewetting, and bubble dynamics. The distance between hydrophobic sections of micropillars acts as permanent active nucleation

Great damages to environment will be caused once high pressure buried pipeline leakage leaks occurs. Distributed temperature sensing (DTS) is a good monitoring method of temperature change. Gas from buried pipe leaks is monitored by changes caused by the Joule-Thomson (J-T) effect. In this work, the temperature variation of buried pipeline leakage is analyzed by finite element method (FEM). The temperature

A numerical study is performed to demonstrate the thermomagnetic convection of air in a side-wall heated enclosure under constant gravity and time-periodic magnetizing force formed by current with sinusoidal waveform. Two cases have been considered: electric coil is located at the right side of the enclosure in case 1, and in case 2 the electric coil is below the enclosure. The spectral element method

The Menter Shear Stress (SST) turbulence model has been added to FEARCE, a Los Alamos National Laboratory Finite Element reactive flow code for solution of fluid-structure interaction, and turbulent reactive flow with multiphases. The SST model is an addition to the Reynolds Averaged Navier-Stokes (RANS) model of Wilcox (k- ω) in FEARCE where the primary focus of the method is the application of unsteady

In view of the heat transfer deterioration of supercritical CO2 under the condition of low mass flow rate and high heat flux, the influence of Body-Centred Cubic (BCC) lattice, Kagome lattice and Pin-fin structure on the heat transfer of supercritical CO2 in rectangular channels were investigated in this article. The results showed that all the three structures can generate arch-shaped vortices near

In this study, thermal resistance of a double-layer micro-channel heat sink (DL-MCHS) with different ratio of upper and bottom channel heights in outlet (α=HU/HB) and the angle of channel inclination (θ), was investigated numerically. The advantage of DL-MCHS in reducing thermal resistance compared with single-layer micro-channel heat sink (SL-MCHS) was quantitatively demonstrated. It was confirmed

Steam is a common medium in thermal engineering. When it flows through a throttling element, the aerodynamic noise may occur due to the disturbance. In this investigation, superheated steam flowing through a Venturi tube, one of the main parts in a temperature and pressure regulation valve, at different thermal conditions is studied to analyze to effects of heat transfer on the acoustic power. With

The present article investigates the melting process of aluminum foam/paraffin composite with low porosity by using experimental and numerical methods. Three composites with porosities 67%, 75%, and 84% are compared in terms of temperature variation, interface evolution, and total melting time. The experimental results indicate that the effect of thermal conduction and thermal convection on the melting

The heat transfer on the trailing edge plays a very important role in cooling the turbine blade of an aircraft engine. The goal of the present study is to examine the heat transfer of four wedge-shaped channels, which are simplified models of the trailing edge, undergoing rotation with different combinations of pin fins, ribs, and Kagome lattices for Re = 15,000. The numerical simulations are compared

The manifold microchannel (MMC) heat sink has become the most popular one among emerging technologies for high heat flux thermal management because of its high surface-to-volume ratio. Even though numerous numerical studies have been performed for the single-phase flow in the MMC heat sink, researches on two-phase flow boiling/condensation in this type of microchannel is seldomly reported because of

Due to the single-side heating on the rectangular channel, the coolant faces a serious thermal stratification problem, and thus the heat transfer performance is reduced. To effectively improve flow and heat transfer characteristics, and weaken nonuniform distribution problem, a new cooling structure with combining fin and spherical convexity is built in this paper. The study results indicate that the

In this article, a multilayer artificial neural network (ANN) identification model is developed to simultaneously identify the thermal conductivity and the effective absorption coefficient of semitransparent materials from flash-type experimental measurements. Firstly, the ANN is trained by means of data generated by a 2-D axisymmetric heat transfer model whose radiative part is treated via the P1

This article presents the development and validation of a semi-analytical (hybrid) model to describe transient heat conduction in a composite material reinforced with long unidirectional cylindrical inclusions. The development of the model relies on the existing analytical solution at the particle-scale, subject to a locally uniform but time-evolving surface temperature; this solution is used to calculate