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Deals with the flow reversal in a buoyancy‐opposed rotating duct that causes heat transfer deterioration. An active technique of trailing‐wall transpiration is adopted to check whether it can avoid the flow separation and subsequently improves the heat transfer deterioration. Finite‐difference method is employed to solve the three‐dimensional Navier‐Stokes equations and the energy equation. Periodic conditions are used between the entrance and exit of a typical two‐pass duct for the closure of the elliptic problem. The predicted results reveal that fluid withdrawal through the trailing wall can avoid the flow separation from the leading wall of the radial‐outward duct (ROD) and thus eliminate local hot spots. In addition, the trailing‐wall suction not only increases the peripherally averaged heat transfer but also reduces the friction loss in the ROD. In the radial‐inward duct (RID), both the peripherally averaged heat transfer and peripherally averaged friction factor are augmented by trailing‐wall injection and are degraded by the trailing‐wall suction.

The purpose of this paper is to numerically study the influence of wall conduction on the heat transfer of supercritical n-decane in the active regenerative cooling channels.

A horizontally placed rectangular pipe with a solid zone and another one without a solid zone were used. A drastic variation of thermo-physical properties was emphatically addressed. After the verification of mesh and turbulence models comparing with the experimental results, a mesh number of 4.5 M and the low Reynolds number SST k-ω turbulence model were chosen. The solution of the governing equations and the acquisition of the numerical results were executed by the commercial software FLUENT 2020 R1.

The numerical results indicate that there is a heat transfer deterioration (HTD) potential for the upper wall, lower wall and sidewall with the decrease of mass flux. Due to wall conduction, the distribution of the fluid temperature at spanwise-normal planes becomes uniform and this feature also takes advantage of the relatively uniform transverse velocity. For the streamwise-normal planes, the low fluid temperature appears close to the upper wall at the region near the sidewall and vice versa for the region near the centre. Undoubtedly, the secondary flow at the cross-section plays a crucial role in this process and the relatively cool mainstream is affected by the vortices.

This study warns that the wall conduction must be considered in the practical design and thermal optimization due to the sensibility of thermo-physical properties to the heat flux. The secondary flow caused by the buoyancy force (gravity) plays a significant role in the supercritical heat transfer and mixed convection heat transfer should be further studied.

A theoretical study is performed to investigate transport phenomena in channel flows under uniform heating from either both side walls or a single side. The anisotropic t^2¯− ε_t heat‐transfer model is employed to determine thermal eddy diffusivity. The governing boundary‐layer equations are discretized by means of a control volume finite‐difference technique and numerically solved using a marching procedure. It is found that under strong heating from both walls, laminarization occurs as in the circular tube flow case; during the laminarization process, both the velocity and temperature gradients in the vicinity of the heated walls decrease along the flow, resulting in a substantial attenuation in both the turbulent kinetic energy and the temperature variance over the entire channel cross section; both decrease causes a deterioration in heat transfer performance; and in contrast, laminarization is suppressed in the presence of one‐side‐heating, because turbulent kinetic energy is produced in the vicinity of the other insulated wall.

Steady-state mixed convection boundary layer flow, heat and mass transfer characteristics of Buongiorno's model nanofluid over an inclined porous vertical plate with thermal radiation and chemical reaction are presented in this analysis.

The governing nonlinear partial differential equations represent the flow model that can be converted into system of nonlinear ordinary differential equations using the similarity variables and are solved numerically using finite element method.

The rates of nondimensional temperature and concentration are both decelerate with the higher values of thermophoresis parameter (N_t).

The work carried out in this paper is original.

Turbulent fluid flow and heat transfer characteristics are analyzed numerically for fluids flowing through a rotating periodical two‐pass square channel. The smooth walls of this two‐pass channel are subject to a constant heat flux. A two‐equation k‐ε turbulence model with modified terms for Coriolis and rotational buoyancy is employed to resolve this elliptic problem. The duct through‐flow rate and rotating speed are fixed constantly; while the wall heat flux into the fluid is varied to examine the rotating buoyancy effect on the heat transfer and fluid flow characteristics. It is disclosed that the changes in local heat transfer due to the rotational buoyancy in the radially outward flow are more significant than those in the radially inward flow. However, the channel averaged heat transfer is altered slightly due to the rotational buoyancy in the both ducts. Whenever the buoyancy effects are sufficiently strong, the flow reversal appears over the leading face of the radially outward‐flow channel, and the radial distance for initiation of flow separation decreases with increasing the buoyancy parameter. A comparison of the present numerical results with the available experimental data by taking buoyancy into consideration is also presented.

This study aims to investigate a three-dimensional computational modelling of free convection of Al₂O₃ water-based nanofluid in a cylindrical cavity under heterogeneous heat fluxes that can be used as a thermal storage tank.

Effects of different heat flux boundary conditions on heat transfer and entropy generation were examined and the optimal configuration was identified. The simulation results for nanoparticle (NP) volume fractions up to 4 per cent, and Rayleigh numbers of 10⁴, 10⁵ and 10⁶ were presented.

The results showed that for low Ra (10⁴) the heat transfer and entropy generation patterns were symmetric, whereas with increasing the Rayleigh number these patterns became asymmetric and more complex. Therefore, despite the symmetric boundary conditions imposed on the periphery of the enclosure (uniform in Ɵ), it was necessary to simulate the problem as three-dimensional instead of two-dimensional. The simulation results showed that by selecting the optimal values of heat flux distribution and NP volume fraction for these systems the energy consumption can be reduced, and consequently, the energy efficiency can be ameliorated.

The results of the present study can be used for the design of energy devices such as thermal storage tanks, as both first and second laws of thermodynamics have been considered. Using the optimal design will reduce energy consumption.

A three‐dimensional numerical study was conducted to assess the heat transfer performance of extended fins in a two‐row finned tube heat exchanger. Fins under investigation were plane and slit types. A finite volume discretization method and a SIMPLE‐based solution algorithm were, respectively, applied to working differential equations and their discrete counterparts to compute the gas velocities and pressure. The temperatures of solid and gas phases were computed from the same energy equation with different diffusivities and prescribed convective fluxes. The main objective of this study was to compare the transfer capabilities of the two investigated fin shapes. Their capabilities as a whole are presented in terms of the computed Nusselt number and the pressure drop across the flow passage.

The objective of the present work is to simulate the nuclear coupled thermal–hydraulic fast transient case studies for a vertically up-flowing supercritical pressure water channel of circular cross section. The emphasis is on analyzing the phenomenon of the deterioration in heat transfer (DHT) inside the channel subjected to sharp pressure variations.

The thermal–hydraulic model, THRUST, is integrated with the neutron point kinetic (NPK) solver to account for the non-linear interactions between the thermal–hydraulic and neutronic temperature and density reactivity feedback effects. The model implemented and studied accounts for the time-dependent reactor power and is used to analyze various steady-state and flow-induced transient case studies (time-dependent and step change in exit pressure).

There is good agreement in the predicted behavior of the supercritical water pressure system with that of the available experimental data for the steady-state case. The event of DHT in the second transient case (step decrease in exit pressure) is found to be more severe than that of exponential pressure decrease.

This study evaluated a novel implementation of the thermal–hydraulic model, THRUST, integrated with NPKs applied to supercritical pressure water systems for predicting DHT.

The purpose of this paper is to study about the natural convection of water-based nanofluid in a partially open trapezoidal cavity under the influence of Brownian diffusion and thermophoresis.

Governing equations formulated in dimensionless stream function – vorticity variables – have been solved by finite difference method with a homemade code C++. Effects of Rayleigh number (Ra = 50-1,000), Lewis number (Le = 10-1,000), buoyancy-ratio parameter (Nr = 0.1-5.0), Brownian motion parameter (Nb = 0.1, 1.0) and thermophoresis parameter (Nt = 0.1, 1.0) on nanofluid flow and heat transfer have been studied.

It is found that high values of Rayleigh and Lewis numbers lead to the homogenization of nanoparticles distributions. For high values of Nt and Nb, heating is more essential and the cavity average temperature rises.

The originality of this work is to analyze natural convection in an open-sided trapezoidal cavity with Brownian diffusion and thermophoresis.

This study aims to show the importance of natural convection of supercritical fluid in an inclined cavity. The heat transfer performance of natural convection can be improved.

A model of an inclined cavity was set up to simulate the natural convection of supercritical fluid. The influence of inclined angles (30 to approximately 90°) and pressures (8 to approximately 12 MPa) are analyzed. To ascertain flow and heat transfer of supercritical fluid natural convection, this paper conducts a numerical investigation using the lattice Boltzmann method (LBM), which is proven to be precise and convenient.

The results show that the higher heat transfer performance can be obtained with an inclined angle of 30°. It is also presented that the heat transfer performance under pressure of 10 MPa is the best. In addition, common criterion number correlations of average Nusselt number are also fitted.

These study results can provide a theoretical reference for the study of heat transfer of supercritical fluid natural convection in engineering.