Pin-fins have been widely used in cooling channels to enhance internal heat transfer. For over thirty years, the literature has been using regular pin-fin shapes or identical pin-fins arrays. However, it was expected that an efficient pin-fin channel should have irregular pin-fin shapes and localized changing shapes along the streamwise direction. These new degrees of freedom for pin-fins were not

The bimodal-pore distributed features of mesoporous silica particles have great effects on their thermal conductivity variations. In this paper, a simplified bimodal-pore distribution model is proposed to depict the variation in thermal conductivity of mesoporous silica particles (such as MCM-41 and SBA-15) at nitrogen pressure. The model is analytically described by a parallel connection of the gas

A numerical model of the solid/liquid phase change problem in porous media and free fluids is presented in this paper for the first time by employing a modified version of the generalized porous medium model, in 2D and 3D, solved by means of the Characteristic-Based-Split (CBS) scheme. The proposed procedure is based on the solution of one set of equations to describe different phenomena: natural convection

A time-averaged Eulerian-Eulerian (E-E) multiphase approach for the simulation of boiling flows is presented. A previously developed bubble dynamics model is implemented in the E-E framework as a sub-model to improve the accuracy of the simulations and reduce the case dependency. This mechanistic model, which is based on the balance of forces applied on a single bubble, considers the evaporation of

Non-axisymmetric endwall contouring of gas turbines has been widely employed as an effective way to improve the aerodynamic performance or heat transfer features. Though efforts have been exerted by previous investigators to generate improved contoured endwall designs, better understandings of the physics behind the phenomenon that non-axisymmetric contoured endwall configurations change the aerodynamic

Effective thermal management is essential for guaranteeing the working efficiency and safety of several industrial devices. Due to its excellent heat absorption characteristic, microencapsulated phase change material (MEPCM) is promising for thermal management system. However, the drawback of MEPCM's low thermal conductivity seriously hinders the heat dissipation rate from heat sink. Based on their

In the natural gas industry, sour gas usually contains some impurities such as CO2. The influence of CO2 fraction on temperature separation within the vortex tube is not fully understood. In the present work, a simulation study has been conducted to investigate the flow and heat transfer behavior of CH4–CO2 binary gas mixtures in a counter flow vortex tube. The model was validated against the experimental

Longitudinal vortices generated by winglet type vortex generators mounted on fin surface improve fluid mixing with disruption of boundary layer growth, which results in convective heat transfer enhancement. The present study reports the three-dimensional numerical investigation of airflow through heated fin-tube heat exchangers in presence of common flow down configured rectangular winglet pairs (RWPs)

The present computational study comprises the geometrical investigation using the Constructal Design of a triangular array of bluff bodies subjected to incompressible, transient, and forced convective flows in a two-dimensional domain. It is considered a Reynolds and Prandtl numbers of ReD = 100 and Pr = 0.71. The body areas and the maximum occupation area of the array are the problem constraints.

The optimization operation has been performed with ANSYS Response Surface Optimization Tool to find optimum channel geometry for converging-diverging channels. Steady state, three dimensional, turbulence, viscous, compressible, single-phase Newtonian flow is assumed through the channel with rectangular cross section. In the study, output parameters have been selected as Colburn factor and Darcy friction

Effect of sidewall on the thermal characteristics of a three dimensional turbulent wall jet with a square nozzle is explored experimentally. The mean and fluctuating quantities are presented through temperature decay, thermal half widths and temperature fluctuation. It is observed that the decay rate of centerline bottom wall temperature of without sidewall is almost half than the corresponding case

The article presents the results of three-dimensional numerical analysis to assess the natural convection heat transfer in pool-type sodium-cooled fast reactors during post-accident heat removal. To improve the coolability of the destroyed core, suitable modifications in core catcher design are suggested. The equations for conservation of mass, momentum and energy are solved in their transient form

Soot particulate matter deposition on the tubes of exhaust gas recirculation (EGR) coolers would form an insulating deposit layer, which deteriorates the thermal efficiency of the cooler and increases the pressure drop substantially. The objective of this research is to examine the influence of using helical tubes instead of straight horizontal tubes on the development of deposit layer. An experimental

The main idea comes from the fact that waste heat generated by the radiating combustion exhaust gas can be recovered by a plate heat exchanger to heat the air flow utilized in different applications. The main contribution of this study is to verify the effect of hot gas radiation and the inclination angle on the performance of plate heat exchangers. For this purpose, two counter-current flows of hot

A numerical study is conducted on a natural convection flow in a differentially heated cavity of aspect ratio 4, submitted to a small-extend thermal disturbance localized on the hot wall. The disturbance is a sinusoidally-varying thermal oscillation applied to the hot wall temperature on an area representing 10% of the whole hot wall. The influence of the disturbance location and frequency is investigated

The present work is focused on a novel cooling device consisting of a microchannel and nanofluid synthetic jet generated through the activation of membrane oscillation at frequencies (f) of 280, 420 and 560 Hz and five different amplitudes (A) ranging from 20 to 40 μm Al2O3 nanoparticles in the fluid domain are set at particle volume fractions (φ) of 2, 3 and 5% with diameter sizes of 50, 75 and 100 nm

The heat transfer rate of thermal energy storage (TES) applying phase change material (PCM) will be reduced in the last stage since the heat is transferred to the top of the enclosure by natural convection. One of the effective method to enhance the heat transfer is to heat the PCM at the bottom directly. Consequently, the optimal arrangement of the TES with eight heat transfer channels in melting

Vortex generators (VGs) have been widely applied in the microchannel heat sinks to improve the thermal-hydraulic performance in multicore processors. However, most studies focus on global heat transfer enhancement of microchannel, while the hotspot temperature is often neglected. In this paper, a numerical study of hotspot-targeted thermal management using VGs is performed in a rectangular microchannel

Directional solidification occurs in industrial and natural processes, such as freeze-casting, metal processing, biological cryopreservation and freezing of soils. Translational temperature gradient stage allows to control the process of directional solidification and to visualize it with optical microscope. In this stage freezing velocity and temperature gradient are decoupled and are independently

In this paper, we have investigated the momentum and heat transfer in an unsteady separated stagnation-point flow of a viscous fluid over a plane surface advancing towards or receding from the normal stagnation flow which impinges on the surface with a variable strain rate s(t), causing the unsteadiness in this flow problem. The flow and heat transfer characteristics are therefore governed by the flow

Discontinuous changes in thermodynamic properties across a very thin-phase interface and irregular deformations in the interfacial shape are accompanied by phase changes. Therefore, to simulate the phase-change phenomenon with a finite-sized mesh system is very challenging. Various numerical phase-change models have been developed, and several of them have been embedded in commercial computational

This paper examines the linear stability of the interface formed by a viscoelastic liquid and a viscous gas. The model obeys the Kelvin-Helmholtz instability. The significant influence of heat and mass transfer at the interface has been included. The analysis was performed for the viscoelastic liquid satisfying Oldroyd-B model using potential flow theory. Through linear stability analysis, a dispersion

Gas turbine airfoils have been consistently exposed to very high temperature gases to extract maximum power. Therefore, there is a growing need to protect the airfoil surfaces from the potentially surface damaging high temperature gases. Film cooling holes and trenches are one possible solution to the aforementioned problem. This thermal protection scheme which has been in practice for some considerable

Scanning electron microscope (SEM) is frequently-used in analysis for micro/nanoscale structural information. During SEM analysis, besides the widely-known charging effect, the temperature rise because of electron beam bombardment has become an issue due to it also can modify SEM results with the downsizing of specimen. In this work, a sophisticated Monte Carlo (MC) model which considered the cascade

In the struggle for a more sustainable economy, thermal energy storage is a relevant solution either for solving the intermittency that is intrinsic to many renewable power plants, or for promoting energy efficiency and the reuse of waste heat. Among the available storage technologies, some rely on latent heat with solid-liquid phase transitions, where natural convection often plays a significant role

We study the consequences of a nonlinear generalization of the Maxwell–Cattaneo equation on the speed of propagation of nonlinear thermal waves. It turns out that such speed depends on the amplitude of the waves and it is smaller than the speed of linear (small-amplitude) waves. This is analogous to the optical Kerr effect of nonlinear optics. In analogy with the electro-optical Kerr effect, an imposed

Inverse estimation of temperature-dependent refractive index and absorption coefficient of semitransparent media is studied in this work. The forward transient coupled radiation-conduction heat transfer in semitransparent media is simulated by the finite volume method. The time-varying radiative response signals at the boundary (not the laser irradiation boundary) is adopted as measurement information

Large eddy simulations (LES) of jet in crossflow (JICF) by modifying the upstream obstacles for enhancing the film cooling performance are performed in this study. Three types of upstream obstacles are considered, i.e. no obstacle, step and ramp placed upstream of the film cooling orifice. The numerical methods and mesh resolution are carefully validated with the experimental data. The predicted results

To study the occurrence of biofouling phenomenon on heat exchanger surfaces, a new biofouling thermal resistance model for heat exchanger surface was developed. Considering the effect of microbial activity on fouling resistance, a growth term of surface biofilm was introduced into the Kern–Seaton model. The microbial growth dynamics was described by using a modified Gompertz model. The occurrence of

Opaque and fully dense solids respond to a laser pulse by absorbing its energy, causing non-uniform heating and thus creating a thermal gradient. Thermalisation by thermal conduction acts to minimise that gradient; monitoring this process as a function of time enables to infer the material properties such as thermal diffusivity. For samples with transparency in the near-infrared region (semi-transparent

In achieving a regularized solution of inverse heat conduction problems (IHCPs), Tikhonov Regularization works based on adding either a zeroth-, a first-, or a second-order term to the sum of squared errors function. In other words, considering combinations of these terms are not often considered. This work investigates employing standard optimization techniques in order to obtain optimal regularization

Slip ratio can be readily measured in an adiabatic two-phase flow experiment. However, in the flow boiling experiments, as the phase velocities keep varying, the estimation of slip ratio becomes difficult. In the absence of reliable methodology, the slip ratio for boiling flows is either taken simply as unity or deduced from void fraction experiments. It is noticed in literature that the experimental

Theoretical modeling of thermal conduction in a multilayer cylinder has been studied in multiple past papers due to its significance in engineering applications such as nuclear engineering, energy storage and sensing. Most past papers have assumed a constant convective heat transfer coefficient on the outer surface of the cylinder. However, a circumferentially varying heat transfer coefficient may

This study numerically presents the characteristics of natural convection induced by a bank of orthogonal heated plates instilled inside porous cavity using the assumption of local thermal non-equilibrium (LTNE) and non-Darcian conditions. In-line and staggered arrangements of heated sections have been investigated for the purpose of comparison. Attention has been given on how the arrangement of heated

The thermal performance of several engineering devices, such as heat exchangers, volumetric solar receivers and thermal energy storage systems, is improved by open-cell metal or ceramic foams. Among them functionally-graded foams, through which morphological characteristics are variable, look promising. Heat transfer and pressure drop in a functionally-graded foam, with a uniform heat flux entering

In this study, a new mathematical model describing the cryosurgical treatment of skin cancer in multilayer tissue has been developed. The cryoprobe whose temperature decreases linearly by time is placed at the skin tumor tissue. The outer surface of the skin i.e. dermis layer has been imposed by different boundary conditions. The mathematical model of this bio-heat transfer problem is a moving boundary

This article presents a measurement method of the apparent thermal conductivities of anisotropic insulating materials at high temperature by the parallel hot-wire method. In the proposed variant, the temperature is measured simultaneously at two points located on the main axes of anisotropy of the material to be characterized. A comprehensive model taking into account the anisotropy, the thermal capacity

The plate-fin heat exchangers with pressure-resistant offset strip fins are widely used in the C3MR and other liquid natural gas (LNG) systems, and the two-phase pressure drop characteristics of flow boiling in pressure-resistant offset strip fin channels is a crucial factor for designing and optimizing the compact heat exchangers. A cryogenic experimental rig was established to obtain two-phase pressure

Two conceptional cathode flow field designs are proposed for preventing serious electrolyte dehydration and overcoming unstable performance issues in polymer electrolyte fuel cells (PEFCs) that are air-cooled and of the passive type. In one design, porous metal foam is selectively inserted into the parallel channels in contact with the cathode gas diffusion layer to suppress water transport from the

Thermal management of high power density insulated gate bipolar transistors (IGBTs) using a low pumping power is crucial for the development of high-performance electric vehicles (EVs) and hybrid electric vehicles (HEVs). In the present work, the liquid cooling module inspired by a human respiratory system was developed to provide enhanced thermohydraulic performance. The suggested cooling module consists

The paper aims to complement thermography with numerical analysis in order to use patients’ personalized data such as precise breast geometry and temperature patterns to detect tumors inside the breast. Previous studies in the literature use idealized semi-spherical breast models without experimental validation and personalized data. To improve the accuracy and reliability of computer-aided diagnosis

An analytical model is presented to predict the equivalent thermal conductivity of the pyramidal lattice core sandwich structure. The equivalent thermal conductivity of the pyramidal lattice core sandwich structure is attributed to both conduction and radiation. The equivalent thermal conductivity caused by heat conduction is evaluated based on Fourier's law. The configuration factor is calculated

The single tank molten salt thermal energy storage (TES) system has been extensively studied due to its low cost and high efficiency performance. The binary nitrates (KNO3+Ca(NO3)2) is selected as heat storage medium in this study, which the melting point is 116.9 °C. This research aims to achieve stable and constant heat discharging performance of the single tank molten salt TES system. Three different

This study deals the influence of fins and inclined magnetic field with nanofluid in single lid-driven and double lid-driven cavities. The effect of fins length and distance between them is also given attention. A two dimensional system of partial differential equations has been discretized by employing Galerkin finite element method. A finite element method involving the cubic polynomials (P3) has

In this paper, the thermal-hydraulic performance in the downstream of the spacer grid in a 7 × 7 rod bundle is numerically studied. The guide tubes effects are revealed by the comparisons of the flow and heat transfer behavior in two types of rod bundles, one without guide tubes and the other with guide tubes. It is found that the cross flow diagonals are fully developed at Z = 2 Dh and unable to sustain

This paper aims to provide a novel enhanced heat transfer method for the internal tip surface of a U bend channel of relevance for a gas turbine rotor blade. The DWVGs (delta-winglet vortex generators) pair is arranged at multiple locations on the tip surface. Two types of vortex generators are studied, including common-flow-up and common-flow-down configurations. The inlet channel Reynolds number

The complex shaped fillers are extensive manufactured to replace the conventional spherical filler for their excellent strengthen heat transfer performance. In this study, the effects on the effective thermal conductivity of filled composites are investigated in regard to filler content, complex shape, directional angle and interface thermal resistance. The results indicate that the effect of interface

Computational numerical simulation is a valuable tool for studying processes that involve living tissues, since it is not invasive, safer, and cheaper than in vivo experiments. The study of heat transfer within human eyes raises special interest given the numerous existing treatments that involve exposing the eye to external heat sources. Furthermore, there is not much blood flow in most tissues of

In the present study, bubble growth on the boiling surfaces and pool boiling heat transfer characteristics of semi-modified pillar arrays are experimentally investigated at atmospheric pressure, while the bubble behaviors inside pillar gaps are numerically revealed in different contact angles by lattice Boltzmann method based on the pseudopotential LB model. The hybrid and hierarchical pillars are

Drawn on the experience of the heat-flow-meter method, an experimental system is designed, established and validated to investigate the thermal insulation performance of SiC opacifier doped silica aerogel at large temperature difference. The test section of the experimental system is a symmetrical sandwich-structure, while the temperature of the cold surface keeps constant by circulating the water

Up to now, the application of fibrous porous medium (FPM) has gained considerable attention within the field of adiabatic materials, especially in the field of vacuum insulation panels (VIP). In the present study, a holistic numerical approach that combined with a modified 3D fibrous porous structure generation method and a D3Q19-BGK Lattice-Boltzmann method (LBM) is developed to investigate the dependence

Thermal stratification occurs frequently in liquefied gas storage tank due to inevitable heat leak or unexpected thermal attack, and has vital influence on equipment safety. For predicting the thermal stratification of liquefied gas, a comprehensive dynamic model of the thermodynamic process in liquefied gas storage tank is proposed in this paper. In the model, the transient free convection in the

In this work, an experiment-based rheological model that accounts for the influence of polymer concentration, shear-thinning behavior, and temperature variation on the in-situ viscosity of gelled acid is developed. On the basis of the rheological model, we present a thermal–hydrologic–chemical coupled model that describes the dissolution process of carbonate acidization with gelled acid. A sensitivity

The aim of the present work is to propose a methodology for the use of thermoelectric modules (TEM) as an alternative to conventional heat flux sensors, for estimating convective and radiative heat flux. In this experimental study, the performance of TEMs as heat flux sensors is compared to that of the heat flux sensor (HFS), a type of conventional heat flux sensor, based on the premise that the HFS