International Journal of Thermofluids最新文献

A novel discharge dispersion model is developed to simulate the complex three-dimensional flow behaviour of thermal-induced buoyant water jets under current-wave coexisting conditions. The model solved the governing fluid flow and energy equations for two immiscible and incompressible phases (water and air) which were weakly coupled by applying the Boberbeck-Boussinesq approximation. Different turbulence models, such as k−ε multiphase, k-ω SST, k-ω SST-multiphase, k-ω SST-stable, and realizable k−ε were applied. Extensive verification of the model's performance is conducted by comparing the developed model results against a diverse range of analytical and experimental data. First, a series of simulations are carried out to evaluate the performance of the model in reproducing the results of the wave hydrodynamic and interactions with the submerged trapezoid bar. This is followed by numerically replicating the experimental results of a vertical non-buoyant submerged jet under current-only and current-wave environments. Finally, the potency of the coupled hydro-thermal algorithm is assessed by validating against different thermal-induced buoyant submerged jet experimental tests. For this purpose, numerical prediction of the developed model is tested against physical experiments for a series of tests for thermal-induced buoyant submerged horizontal jets in stationary water and inclined thermal-induced buoyant water jet under the influence of current-wave environments. Results showed that the k-ω SST-multiphase provides the best agreement with the laboratory measured data in terms of flow, temperature distribution field, plume trajectory and dilution. The findings confirmed that the developed model can be used as a reliable tool in precisely modelling characteristic of thermal-induced buoyant water jet in shallow coastal waters.

In the analysis, design, and optimization of a wide range of engineering applications involving stretching surfaces and fluid flow, the skin friction coefficient (SFC) at a stretching surface with heat transfer is an important parameter that reflects the fluid dynamics, heat transfer characteristics, and surface interactions. Owing such importance, the purpose of present article is offer artificial neural networking remedy for evaluation of SFC for Williamson flow field with thermal slip and heat source effects. The Williamson fluid flow is realized by considering surface stretching with an externally supplied magnetic field. The energy equation is used to address the heat transmission. The constructed differential system for flow field is solved by conjecturing artificial neural networking with Lie symmetry and shooting methods. Artificial Neural Networking (ANN) model is developed to predict the surface quantity namely SFC at thermally magnetized surface. The major findings includes the variation in SFC for pertinent flow parameters and we found that in the presence of heat transfer aspects, the SFC admits declining nature towards Weissenberg number while opposite is the case for magnetic field parameter.

Nowadays, electric vehicles (EVs) significantly affect transportation as they provide a more environmentally friendly alternative to traditional fossil-fueled automobiles. Electric vehicles, which depend on energy stored in batteries, significantly contribute to environmental preservation and comply with worldwide efforts to tackle climate change. However, the growing demand for electric vehicles causes traditional power grids under pressure emphasizing the necessity of establishing a suitable infrastructure for charging electric vehicles. Charging stations are becoming increasingly critical since they allow for the recharging of electric vehicles and play a significant role in stabilizing the power system. In order to optimize charging station infrastructure with multiple servers, the current research incorporates a Markovian queueing modeling approach. The primary objective of the study is to address queue management concerns and boost overall productivity. Considering the real-world challenges, a queue-based stochastic model for multi-server EV systems and individual feedback strategies is developed. Subsequently, a transition state diagram is provided by balancing the input-output rates between the adjacent states. Next, the system of Chapman-Kolmogorov differential-difference equations is formulated to help understand mathematical modeling better. The matrix method is employed to demonstrate the state probability distribution in equilibrium. The infographics are utilized and incorporated for better visualization of the research findings. For a better understanding from an individual's point of view, numerous managerial insights are provided. Lastly, several concluding remarks and future perspectives are provided that can help decision-makers and practitioners to construct and analyze economic strategies based on EV management systems.

The development of modern life requires new energy sources, and one of this energy is renewable solar energy uses in solar chimney for natural ventilation, but at the present time it is not greatly invested, taking into account the weather conditions of the region and the physical characteristics of solar radiation and air in the area in which the study will be conducted. The current study was carried out in Basrah city- Iraq, at longitude 47.749° and latitude 30.568°, where the solar chimney was facing south. The investigation was conducted using both theoretical and experimental studied. In the theoretical study, the solar chimney with the room in the presence and absence of PCM was simulated numerically using the finite volume method using the soft package ANSYS-Fluent/2021/R2. The effect of different tilt angles (α = 30°, 45°, and 60°), solar chimney air gap (gab = 10 cm, 15 cm, and 20 cm), and PCM basin thickness (t_PCM = 3 cm, 4 cm, and 5 cm) were investigated. The results were presented in the form of contours of the distribution of streamlines, velocity, temperature, and liquid fraction of the solar chimney with the room, rate of temperature of the absorber plate with time and the rate of temperature of the PCM (T_PCM) with time, rate of air change per hour (ACH). As for the experimental side, the device was built, and the intensity of solar radiation was studied for several days on 30 Sep. and 15 Oct. 2023, the temperature distribution rate of the absorbent plate over time, the PCM temperature rate, and the air change per hour (ACH). The theoretical results were compared with the experimental results, where there was good agreement, and the theoretical comparison was also made with several researchers. Significant results showed that the optimal ratio of the air gap width of the solar chimney is 15 cm, the inclination angle of the solar chimney α = 30°, and the thickness of the PCM basin (t_PCM = 4 cm) to obtain the maximum ventilation rate. The thickness of the PCM basin = 4 cm gives the largest liquid fraction along time and maximum average temperature of the absorber plate. On the experimental, it was found that PCM convert into the liquid phase after its melting point, which is 340 K, after 12 noon, and the highest value of ACH reached 37 on September 30/2023 at midday.

This study extensively analyzes various regular and irregular vanes in pipe porous cavities on natural convection, thermal entropy generation, stream function, and temperature distribution in fluid and solid phases. The finite element method (FEM) is employed to study stream function, temperature distribution in the fluid phase and solid phase, and various γ for Nu_f, ave and Nu_s, ave in SR, TR, SIR, and TIR. In the present study, a significant contribution of this research is the investigation into the effects of regular versus irregular vanes in the context of enclosures formed by pipe porous cavities that the SIR specimen has the most influence on stream function and thermal effect in the fluid phase and solid phase that aims to enhance system performance and optimize energy efficiency. In addition, the significant influence of geometrical parameters constitutes many heated obstacles in the middle of SIR, various heated vanes in the left of SIR, and employed Ra and ε in the analysis of Nu_f, ave and Nu_s, ave in SIR are carried out to investigate the percentage discrepancies obtained, notably 89.35 % and 89.72 %, respectively. In validation, the calculation in results was adapted accurately to the finite element method's stream function, the temperature distribution in the fluid phase and solid phase, and various γ for Nu_f, ave and Nu_s, ave which means that the percentage differences in obtaining results reached under 1 %. Numerical results revealed that the Hartman number has a significant influence in S_htf, ave,  S_hts, ave,  Ty_ave, Nu_f, ave and Nu_s, ave in TR, SR, TIR, and SIR.

Fin and tube heat exchangers (FTHE) find widespread application in a variety of industries including refrigeration, air conditioning, automotive, electronics, and power generation. Current research on FTHE is focused on developing heat exchangers that are compact, cost-effective, and energy efficient. This review paper is focused on the quantitative assessment and comparison of the thermal-hydraulic performance of different type of FTHE. Analysis of variance is used to determine the most important performance factors and their interactions for the considered type of FTHE. A comparative analysis of the thermal-hydraulic performance of different FTHE types is conducted based on Nusselt number, friction factor, and normalized performance evaluation index (NPEI). Finally, a parametric study is carried out to investigate the impact of significant performance parameters on the thermal-hydraulic characteristics of the respective FTHE type. Louvered FTHE and modified FTHE with vortex generators outperform the plain and wavy FTHE in terms of NPEI. This comprehensive review offers significant insights for enhancing the thermal-hydraulic performance of different type of FTHE and selecting the appropriate type tailored to specific application requirements.

Buoyantly induced flows possess diversified utilizations in numerous engineering processes for instance, reactor cooling through passive strategy, LED lights, pipes manufacturing, ship funnel and many more. Galvanized sheets sticked to form a hollow cylinder is used for fast cooling in naval ship and chimney of steam power plant. In view of such mesmerizing significance of flow and thermal attributes of fluid over vertical cylinder, current effort is articulated. For this purpose, Williamson fluid model is accounted and nanoparticles are also induced to envision advanced thermal features in the flow over vertically oriented cylinder. Physical effectiveness of magnetic field implications and chemical reactive species are entertained to notice change in hydrothermal and mass fields. Slip boundary constraint along with stagnant flow at the surface of cylinder is considered to inspect behavior in free stream region. The fundamental governing equations of problem are attained in the sense of PDEs by utilizing the concept of boundary layer approximation and converted into coupled nonlinear ODEs by substituting specific similar variables. Numerically the resulting ODEs are resolved by making the use of bvp4c built in MATLAB routine, the outcomes are attained and arranged in graphical and tabular manner. The influence of pertinent flow parameters such as (0.1 ≤ We ≤ 1.0), (1.0 ≤ M ≤ 3.0), (1.0 ≤ Pr ≤ 11), thermophoresis parameter (0.5 ≤ T_p ≤ 4.5), (1.0 ≤ B_p ≤ 5.0), (0.05 ≤ N_r ≤ 0.7), and (0.5 ≤ K_c ≤ 5.0) are examined on the momentum, thermal and concentration distributions. It is manifested that the velocity distribution depreciates by uplifting magnetic field strength. Increment in magnitude of wall drag and convective heat transfer is perceived by enhancing Prandtl number. It is inferred that friction coefficient in absolute sense and heat flux coefficient tends to exceed against elevation in (We). From comprehensive analysis, declination in velocity and thermal field is depicted versus Reynold number whereas, contrary aspects are visualized in concentration. Enhancement in the value of surface drag and thermal flux is revealed versus (Re).

Phase change materials (PCMs) are very suitable for the storage of thermal energy. Heat transfer plays a crucial role in many important industrial processes in today's industrial environment. Thus, it is crucial to examine and comprehend this occurrence properly. This work uses molecular dynamic simulation to examine the effect of initial pressure (IP) and temperature (Temp) on the thermal efficiency of phase change materials inside a three-dimensional cavity. The hollow contains paraffin/Cu nanoparticles and has a bottom wall with a wavy shape and an upper wall that can be adjusted. The results of the equilibration stage indicated that the kinetic and potential energies converge to 2100 eV and -95472.50 eV after 10 ns. Next, the results show that increasing IP resulted in the reduction of maximum velocity and Temp, which decreased from 0.0099 Å/ps and 898 K to 0.0090 Å/ps and 888 K. Furthermore, the results show that by increasing IP, the heat flux and thermal conductivity decrease from 9.95 W/m² and 1.45 W/m.K to 8.89 W/m² and 1.26 W/m.K. Conversely, as the initial Temp rose from 300 to 350 K, so did the velocity (0.0125 Å/ps) and Temp (990 K). Furthermore, the thermal conductivity and heat flux increased to 1.69 W/mK and 11.25 W/m², respectively. This study reveals how molecular dynamics simulations provide insights into the effects of initial pressure and temperature on the flow and thermal behavior of a paraffin/copper nanostructure. The findings improve understanding of nanofluid and phase change material behavior, aiding the design of more efficient PCM-based systems for thermal energy storage and heat transfer applications. In general, the results of this research illuminate the complex relationship among IP, Temp, and thermal properties of phase change materials. This knowledge is of great significance as it can guide the formulation of novel approaches to enhance the thermal efficiency of these materials in practical applications.