International Communications in Heat and Mass Transfer最新文献

Natural convection heat transfer phenomena in nanofluid-filled square cavities with various temperature boundary conditions are studied computationally. From electronic cooling to building ventilation systems, such phenomena have numerous practical applications, and accurate simulations are crucial for developing new designs. Towards that end, the Navier–Stokes equations of incompressible flows are considered with thermal coupling. The base fluid is pure water, the nanoparticles are copper (Cu), cupric oxide (CuO), or aluminum oxide (Al₂O₃), and the nanofluids are assumed to be homogeneous. It is well known that, in the standard finite element method framework, inappropriate selection of interpolation functions, e.g., (bi-)linear equal-order-interpolation velocity-pressure (e.g., $P_1{P}_1$ and $Q_1{Q}_1$) elements, yields nonphysical oscillations in the flow field for simulating incompressible flows, particularly for high Rayleigh numbers. In this study, in order to overcome such numerical instability issues, the streamline-upwind/Petrov–Galerkin (SUPG) and pressure-stabilizing/Petrov–Galerkin (PSPG) finite element formulations are utilized. The SUPG/PSPG-stabilized (SUPS) formulation is also enhanced with the least-squares on incompressibility constraint (LSIC). A comprehensive set of numerical test computations is considered for the values of the Rayleigh numbers ranging from ${10}^3$ to ${10}^6$ and a broad range of volume fractions of nanoparticles from $\varphi =0.025$ to $\varphi =0.2$. Incompressible flow solvers are developed in-house and executed in parallel. Numerical simulations and comparisons with reported studies reveal that the proposed formulation performs quite well even at high Rayleigh numbers, and it does not exhibit any significant local or globally spread numerical instabilities. It is also noted that this is achieved without employing any adaptive mesh strategies and using only linear and equal-order interpolation functions, which in turn saves computational time.

The major purpose of this publication is to examine a theory explaining an incompressible steady two-dimensional flow of Sisko fluid models in a vertical peristaltic tube with shear thickening. Boundary conditions are also considered, which characterize the impacts of heat transport. Thermal dissipation, concentration, double diffusivity and momentum equations are also included. The capacity of heat transfer fluids to convey heat more effectively is supposed to be enhanced by nanofluids. The dimensionless equations related to our work cannot be solved manually, so the MATLAB BVP4C technique is utilized to observe the graphical behavior of various parameters for long wavelength and low Reynold's number. The novelty of the manuscript is to explore characteristics of the Sisko fluid model under MHD and electro-osmosis, which are very significant for future research work in the fields of industry and medicine. Our analysis illustrates that thermal and Solutal Grashof numbers show opposite behavior to that of nanoparticle Grashof numbers for velocity profile. According to the results, raising the Brownian and thermophoresis diffusion parameters raises the fluid's temperature, then slows down by further extending both parameters. Moreover, the effect of a magnetic field is delineated that the presence of a magnetic field parameter dwindles the fluid's velocity. The Dufour parameter causes the double-diffusive convection to be enlarged. Additionally, it is accomplished that double diffusivity diminishes when the Prandtl number is surged up while accelerating as the radiation parameter $R$ boosts.

Transient interfacial heat and mass transfer is investigated for film-wise condensation underneath the inclined wall of a solar desalination system developing a fully coupled arbitrary Lagrangian-Eulerian interface tracking (ALE-IT) algorithm. Evolution of solitary and capillary waves shows significant effects on the condensation rate of a condensate falling film. The influence of wall length, wall inclination angle, wall-vapor temperature difference, and vapor temperature oscillation are determined on the interfacial instabilities to investigate the condensation characteristics of a solar desalination system. It is shown that the length of the wall does not affect the onset of interfacial instability. However, increasing the length of the wall can effectively enhance the total condensation rate as a result of film waviness. Among the studied parameters, the wall-vapor temperature difference has the highest effect on the average mass flux. Each ${10}^{°}C$ increment in the vapor temperature can increase mass flow rate from 17% to 27%. At wall-vapor diference of 50°C, the increment in frequency of interfacial temperature oscillation increases the condensation rate up to 11%. Furthermore, each $5^{°}$ decrease in inclination angle from the horizon can enhance the condensation rate between 3% to 8%.

Interactions between tetra-hybrid nanoparticles and non-Newtonian blood mediums lead to unique transport dynamics, influenced by magnetohydrodynamic forces and laser irradiation. Tetra-hybrid nanoparticles are an advanced class of nanomaterials that incorporate four distinct components gold (Au), silver (Ag), alumina (Al₂O₃), and titania (TiO₂). Each of these materials contributes unique properties, resulting in a multifunctional composite with enhanced optical, electrical, and thermal characteristics. Tapping into these synergistic nanoscale effects has the potential to inform various biomedical applications, including targeted drug delivery, hyperthermia cancer treatment, lab-on-a-chip devices, biosensing, and miniaturized diagnostics. Investigate streaming flow phenomena induced by interactions between tetra-hybrid nanocomposites and a non-Newtonian Jeffery fluid. Elucidate the complex transport dynamics altered by imposed magnetohydrodynamic forces and localized laser irradiation. Provide computational predictions regarding velocity, temperature, and particle concentration profiles. Capture intricate cellular trapping patterns arising from non-Newtonian rheology. Demonstrate the feasibility of precision fluid control through the use of biocompatible multimodal nano-assemblies. Capture multidimensional flow regimes under the influence of electromagnetic actuation and thermos-plasmonic effects. Resolve ordinary differential transport equations for momentum, energy, and mass species. Visualize two- and three-dimensional velocity streamlines, isotherms, and nanoparticle distribution contours. The graphical exploration of quantities relevant to engineering, such as heat transfer rate, mass transfer rate, skin friction coefficient, Nusselt number, Sherwood number, and optimization of entropy generation, is also depicted.

Resistance heating for variable cross-section cylinders before quenching results in the coarsening of austenite grains in the thin-wall segment, and inevitably leads to nonhomogeneous hardness and inferior properties after quenching. In this study, a half open anti-profiling coil is designed for induction heating of the workpiece before hardening. A numerical model is established, coupling the electromagnetic-thermal field and the rotary motion of the variable cross section cylinder to investigate the system heating efficiency and heating quality. The calculated data reveal the high efficiency of induction heating system, although the heating efficiency decreases significantly as the magnetic permeability rapidly drops at high temperature periods. Additionally, the temperature distribution along the axial, circumferential, and radial directions fluctuate in different parts at the end of heating time. Narrower air gap improves the heating efficiency and axial direction heating quality, albeit at the expense of reduced radial direction heating quality. An induction heating experiment validated the simulation results with an error range of 1.61% to 7.59%. These results suggest that to improve heating quality while ensuring high heating efficiency, it is crucial to design a suitable air gap that accommodates various wall thickness segments of the workpiece. Moreover, incorporating insulation measures is essential to reduce temperature distribution difference caused by surface heat dissipation. This study presents a promising technical solution for upgrading the current heat treatment process.

In this paper, the characteristics of oscillatory flow have been numerically investigated in the isothermal closed cavity of self-excited oscillating twin jets for several nozzle spacing-to-width ratios, $0\le S/e\le 12,$ and volumetric flowrates of $Q=0.04,0.08,\text{and}0.12m^3/s$. The results showed that in $0\le S/e\le 6.5$ two jets merge at a short distance after the nozzles and oscillate with a frequency equal to that of the single oscillating jet. At $6.5<S/e<9$, the oscillatory behavior of the twin jet enters a transient and unstable oscillatory mode. By increasing the nozzle spacing to $9\le S/e\le 12$, the oscillating behavior of the jet becomes stable, and jet flows oscillate with a much higher frequency than the self-excited oscillating single and twin jets with $0\le S/e\le 6.5$. In this research, the critical nozzle spacing (minimum nozzle spacing in which merging does not occur) was calculated for different flow rates. Also, an analytical method was presented based on the concept of half velocity edges to predict the critical nozzle spacing. The results showed that the analytical model is accurate compared to the numerical results. It was also revealed that the capability of self-excited twin jets to intensify the oscillating features in the flow field will be evident at nozzle spacings greater than the critical value.

This paper presents an experimental study on the joint effects of concurrent airflow and sample width on the steady flame spread behaviors. Flame spread parameters, including flame height, preheating length, heat flux distribution, flame spread rate (FSR) and pyrolysis length, were measured and analyzed comprehensively. Results show that the FSR and pyrolysis length increase with sample width and concurrent airflow velocity. For wider samples, FSR and pyrolysis length are more sensitive to the changes in airflow velocity. The flame height and preheating length increase with sample width, due to the enhanced fuel burning rate and limited air entrainment. The average heat flux in preheating zone is independent to the airflow velocity and sample width. In pyrolysis zone, the convective heat flux is the dominant heat transfer term under concurrent airflow. Theoretical analysis indicates that in steady spread stage, FSR and the pyrolysis length are proportional to the concurrent airflow velocity. Additionally, FSR increase with the 1/3rd power of sample width, whereas the pyrolysis length increases with the 2/3rd power of sample width. Pyrolysis length can be well predicted based on the energy balance at the pyrolysis front.

During a severe power plant accident, steam condensation mitigates containment pressurization in a postulated nuclear accident. Understanding the condensation process of the steam jet is essential to prevent structural damage and accidents. This study investigated the effect of temperature at the nozzle exit under superheated conditions on the steam jet velocity and temperature distribution, and the condensation characteristics of the steam jet released from the orifice nozzle. The steam jet discharged from the orifice nozzle exhibited the vena-contracta effect, resulting in an increase in velocity along the centerline and a decrease from the exit to the near field. In experiments, the temperature of the exit nozzle was adjusted to 100.4 °C, 106.3 °C, and 112 °C, sequentially. It was found that as the steam jet moves downstream, it undergoes condensation as it mixes with the surrounding air. As the temperature at the exit becomes lower, the condensation becomes more significant, resulting in smaller temperature and velocity spread rates, and larger Liquid Water Content (LWC) and Total Number Concentration (TNC) values, due to the condensation process.

Carbon capture, utilization, and storage (CCUS) has been recognized as a crucial path to mitigating the effects of greenhouse gas emissions on climate change. Mineral Carbonation (MC) processes are among the safest and most promising alternatives for CCUS due to on-site product stability. However, technical challenges need to be overcome to scale up the technology, such as energy penalties and sufficiently fast kinetics. The constructal design method provides a path to achieve those goals altogether. This paper first addresses the constructal design of a mineral carbonation porous bed reactor for post-combustion carbon capture. Analytical models allowed to obtain optimized parameters for the aspect ratio of the elemental volume, which is then packed in hierarchical flow structures to minimize pressure losses (energy penalties). Numerical full-scale models show the validity of the proposed relations. The trade-off between pressure losses and rate of reaction is then explored by the ratio with which the first construct is filled with reacting material. Results for the multi-scale design show that it is possible to associate geometric configurations with pressure drops for the carbon capture devices and to seek configurations that lead to lower energy expenditure. The findings can be applied for other types of fixed bed reactors.