International Journal of Thermofluids最新文献

This paper presents a statistical and numerical investigation that examines the optimization and sensitivity analysis of the unsteady laminar natural convective heat transfer flow of Fe₃O₄-water nanofluid in a hexagonal cavity considering the impacts of a sloping magnetic field in one-component nanofluid model. The inclined walls of the cavity are maintained at a constantly low temperature, while the bottom wall is uniformly heated. The upper wall, however, is regarded as adiabatic. The nanofluid thermal conductivity model incorporates the impact of Brownian motion. The Galerkin weighted residual finite element method has been employed to solve the governing dimensionless equations. The results are provided regarding the average Nu, streamlines, and isotherms. The study uses response surface methodology to analyze the sensitivity of parameters such as the Ha, Ra, and nanoparticle volume percentage. Using a response surface policy allows for optimizing the process and identifying the most favorable circumstances to achieve the maximum thermal transfer rate. The flow pattern of the nanofluid is significantly affected by the magnetic field and its alignment. The numerical results indicate a significant rise in the average Nu as the nanoparticle volume percentage, magnetic field inclination angle, nanoparticle type factor, and Ra increase. Conversely, the Hartmann number and the nanoparticle's diameter have contrasting effects. When considering Brownian motion, the average Nu grows by 225.89 % for Ra = 10⁶ with ϕ = 0.03 and 25.28 % for the other case. The optimal condition for heat transfer occurs when Ra = 10⁶, Ha = 4, and ϕ =0.03 while keeping the other parameters constant.

This study presents a novel and corrective analysis of Dual-Phase-Lag (DPL) non-fourier heat conduction in functionally graded cylindrical materials with bi-directional property variations. For general purposes, the 2-D DPL model was employed and solved in a polar coordinate system for an FGM cylinder whose material properties vary exponentially in the axial and radial directions. The proposed model's analytical and numerical solutions were obtained through the SOV method and implicit FDM with a non-uniform grid. Moreover, the effect of the inhomogeneity parameter in the Fourier, Cattaneo–Vernotte (C–V), and DPL models has been analyzed. The results indicate that the DPL model achieves temperature stability in less time when contrasted with the C–V model. In addition, the reduced inhomogeneity parameters result in quicker attainment of a steady temperature and the induction of higher temperatures. The thermal wave propagation in the DPL model is consistently greater than that in the C–V model. In addition, an increase in time lag for heat flux enhances thermal wave properties (amplitude, wavelength, propagation speed etc.); conversely, an increase in time lag for temperature gradient counteracts wave properties and augments heat release. Nevertheless, the present outcomes offer a straightforward multivariate analytical and numerical solution for a finite cylinder's non-Fourier heat conduction equation under diverse boundary conditions.

Bacteria are living microorganisms that play an essential role in the biodegradation process. They can break down and detoxify harmful substances, thereby mitigating environmental contamination through natural means. The Gompertz and Logistic models are two growth models commonly utilized to examine population growth in biological systems. In this study, we have modified these models to investigate the growth of Escherichia Coli K2 bacteria. The mathematical parameters have been substituted with biologically meaningful parameters, and five new estimation methods have been introduced to evaluate the model parameters using standard growth data for E. Coli K2. The best method is selected based on a standardized criterion used in this study. The proposed methods demonstrate strong performance, and the estimated parameters are both logically coherent and biologically relevant.

Forced convection in Newtonian and non-Newtonian fluids flowing through pipes maintained at uniform heat flux or uniform wall temperature are important for understanding heat transfer characteristics in design and thermal management of heat exchangers. Convective heat transfer in both Newtonian and non-Newtonian fluids flowing through pipes and parallel plates, subjected to uniform wall heat flux condition, were extensively studied by researchers. But for uniform wall temperature, studies on non-Newtonian fluids in pipes are rarely considered. Forced convective heating and cooling of a third-grade fluid, flowing in a pipe subjected to uniform (constant) wall temperature is considered. Effect of viscous dissipation is included in the energy equation. Separate energy conservation equations for heating and cooling are formulated and their dimensionless forms are obtained. Numerical solutions by shooting technique are obtained for the governing equations. The same equations are also solved by the least square method and semi-analytical solutions are yielded. Least square method is a widely used semi-analytical tool used for solving non-linear differential equations. Results of the numerical solution and semi-analytical solutions are compared and are observed to be in close agreement. This validates the numerical solution. Few important observations are presented. For heating, when the non-Newtonian parameter increases from 0 – 0.1, the peak temperature drops from 1.15 – 0.55 which occurs at the centre. In case of cooling, when non-Newtonian parameter increases from 0 – 0.1, the difference in central line temperature and wall temperature increases to 0.17 from 0.09. For change in the non-Newtonian parameter from 0.2 – 0.3, both for heating and cooling the peak temperature change is not drastic. Heat transfer coefficient, in case of heating, differs by nearly 3.5 when the non-Newtonian parameter increases from 0 – 0.1.

This study addresses the numerical investigation of the steady and two-dimensional flow of magnetohydrodynamic nanofluid containing motile microorganisms over three distinct configurations: a wedge, a plate, and the stagnation point of a flat plate. The impacts of activation energy, melting phenomena, thermophoresis, and Brownian motion are taken into account. The dimensionless form of the governing coupled nonlinear partial differential equations is obtained by using similarity transformations. The system of ordinary differential equations is numerically solved using the “bvp4c” solver in MATLAB, and obtained results are also validated with an analytical approach Optimal Auxiliary Function Method (OAFM). Skin friction, heat, mass and motile microorganisms transfer rates are discussed through graphs and tables. Findings indicate that profile for Nusselt number enhances for higher inputs of melting parameter while Sherwood number lowers with increasing inputs of activation energy parameter. An improving pattern of velocity profiles is magnificent for stagnation point flow [f(η = 1) = 0.943711] compared to wedge [f(η = 1) = 0.915698]and horizontal plate [f(η = 1) = 0.868617]with respect to wedge angle parameter keeping velocity ratio parameter A < 1. For the wedge surface, the temperature profiles decrease [θ(η = 1.5) = 0.933075,  0.895245,  0.858931] for increasing inputs of radiation parameter (2.5 ≤ Nr ≤ 4.5) while motile microorganism profiles enhance [χ(η = 1.3) = 0.532505,  0.621569,  0.690635] with bioconvection Schmidtt number (0.3 ≤ S_b ≤ 0.7) respectively. Furthermore, it was found that, as velocity slip parameter increases then velocity of fluid also improves over a plate, wedge, and stagnation point of a flat plate considering velocity ratio parameter A < 1 .

Liquid cooling using a mini-channel heat sink (MHS) has been highly efficient in cooling rectangular and cylindrical lithium batteries. This work proposed a new hexagonal MHS (HMHS) to cool a cylindrical heat source instead of the traditional cylindrical with smooth MHS (CSMHS). In addition to the smooth channels, four obstructed channels were proposed to further enhance the thermal performance of this HMHS. The obstructions used include: semicircular ribs–cavities, semicircular ribs–secondary flow, semicircular pin fins and semicircular pin fins–cavities. This study was numerically conducted using the finite volume method under water Reynolds number ranging from 100 to 800. CSMHS and HMHS with semicircular pin fins were manufactured and tested to verify the validity of the numerical results. Results showed that the HMHS exhibited superior hydro-thermal performance compared with the CSMHS. In addition, the HMHS with obstructed channels contributes to a significant improvement in thermal performance. The percentages of Nusselt number improvement with all channels were approximately: 12.3%, 60.5%, 71.5%, 104% and 112% for smooth, semicircular ribs–cavities, semicircular rib–secondary flow, semicircular pin fins and semicircular pin fins–cavities, respectively. Amongst all the channels, the channels with semicircular pin fins achieved the best performance with a hydro-thermal performance factor of 1.67.

Natural fiber-reinforced composites are increasingly recognized as sustainable alternatives in construction materials due to their environmentally friendly properties and ability to increase thermal insulation. This study conducts an in-depth comparative study between palm fiber (DPF) composites and other natural fiber-reinforced composites, including hemp and jute, with a focus on their application as insulation that provides insight into their thermal properties, performance, and mechanical properties to inform sustainable construction practices. The research methodology involves constructing and producing composite samples using date palm, hemp, and jute fibers, each combined into a common base material. Composites are mold-made, ensuring consistent and reproducible samples for testing. Through a systematic investigation, we explore these composites' thermal, and mechanical properties. Testing covers a specific range of fiber loadings, from 10 wt % – 30 wt %. Specific characterization techniques, including compression test, bending test, impact, FT-IR, and DSC, were used to evaluate the behavior of the composites under various conditions. Our results show that the thermal conductivity of the composites ranges from 0.0514 – 0.084 W/m. K for different fiber loading is affected by the fiber content.

Furthermore, at maximum fiber concentration (30 by weight), the highest heat capacity of the hemp composite was 1674 J/Kg.K. The 30 wt % of jute and date palm composites achieved a maximum compressive strength of (70 MPa) and (64 MPa) respectively.

In summary, this comprehensive study demonstrates the potential of natural fiber-reinforced composites as sustainable and fully bio-based alternatives for construction-related applications. Superior thermal properties and improved mechanical strength highlight their viability in thermal insulation applications.

Advancements in water electrolysis technologies are crucial for green hydrogen production. Proton exchange membrane water electrolysis (PEMWE) is characterized by its efficiency and environmental benefits. The prediction and optimization of hydrogen production rates (HPRs) in PEMWE systems is difficult and still challenging because of the complexity of the system as well as the operational parameters. The integration of artificial intelligence (AI) and machine learning (ML) appears to be effective in optimization within the energy sector. Hence, this work employs the artificial neural network (ANN) to develop a model that accurately predicts HPR in PEMWE setups. A novel approach is introduced by employing the Levenberg–Marquardt backpropagation (LMBP) algorithm for training the ANN. This model is designed to predict HPR based on critical operational parameters, including anode and cathode areas (mm²), cell voltage (V) and current (A), water flow rate (mL/min), power (W), and temperature (K). The optimized ANN configuration features an architecture with 7 input nodes, two hidden layers of 64 neurons each, and a single output node. The performance of the ANN model was evaluated against conventional regression models using key metrics: mean squared error (MSE), coefficient of determination (R²), and mean absolute error (MAE). The findings of this study reveal that the developed ANN model significantly outperforms traditional models, achieving an R² value of 0.9989 and an MAE of 0.012. In comparison, random forest (R² = 0.9795), linear regression (R² = 0.9697), and support vector machines (R² = − 0.4812) show lower predictive accuracy, underscoring the ANN model's superior performance. This work demonstrates the efficiency of the LMBP in enhancing hydrogen production forecasts and sets a foundation for future improvements in PEMWE efficiency. By enabling precise control and optimization of operational parameters, this study contributes to the broader goal of advancing green hydrogen production as a viable and scalable alternative to fossil fuels, offering both immediate and long-term benefits to sustainable energy initiatives.

Mixed convection convection is a vital subject and it is beneficial in many engineering applications. The current paper addresses this subject with a novel geometry and very vital variables including magnetohydrodynamic influences on the forced/free convection as well as the reproduction of irreversibilities in an enclosure filled with water/carbon nanotubes (CNT) and a nonadiabatic cylinder. The top wall is split from the middle and moves in different directions to drive the isotherms which are generated from the bottom wall and cold from the vertical surfaces. The numerical analysis was carried out using finite element method; the variables are Reynolds number (40–200), Richardson number (0.01–10), Hartmann number (0–62), inclined magnetohydrodynamic angle (0–60), volume concentration (0–0.08) while Prandtl number has kept constant at 6.2. The results show that the transformation of heat, as well as the fluid flow, are largely influenced by the change of variables, where increasing Reynolds number, Richardson number enhances heat and increases the flow circulation. Furthermore, heat transfer enhances by 57 % when increasing Ri from 0.1 to 10 at Re=41 and this enhancement increases to 62.5 % at Re = 200. Furthermore, increasing the concentration of the carbon nanotube can cause heat transfer but decrease the circulation of the fluid. In contrast, the transfer of heat as well as the flow streams are remarkably decreased with the increase of the Hartmann at zero inclination angle; however, the value of the Nusselt average increases with the increase of the inclination angle. Moreover, the value of Nusselt average decreses by 34.7 % when increasing Ha from 0 to 62 at Re = 200. Furthermore, the total entropy generation increases as Richardson number, Reynolds number, and volume concentration increase; in contrast, detraction with the rise of the MHD.

Numerous methods are conceived to pick up the heat from hot plats, where, amidst all, film cooling methods possess several benefits and have always been considered. However, increasing the cooling effectiveness of this method while reducing the coolant mass flow rate has always been considered one of the concerns, and much literature has yet to be presented to surmount this problem. In this study, three different novel jet configurations including simple, semi-mushroom, and semi-oval jet types are proposed to boost the effectiveness of the film cooling method while the mass rate is drastically lower compared to the traditional jet types. Instead of using the traditional film jet that usually blows the coolant flow at a 30-90-degree angle, it can be changed so that the coolant is wholly blown in the mainstream path, simultaneously reducing the mixing ratio and increasing the diffusion of coolant film. Meantime, the arc-shaped jet design can increase the surface coverage by the coolant fluid, especially in the transverse direction. This innovative concept is also reckoned for in this study by presenting computational simulation using the k − ω − SST turbulence model, which has some superiority for turbulent near wall flows. The results showed that at BR=0.5 and x/d=5, the proposed novel jet (simple type) achieved a 17.9% improvement in averaged cooling effectiveness compared to regular jets, while utilizing a coolant mass flow rate ten times lower. Also, it found that contrary to the results related to regular jets, the averaged cooling effectiveness increases with the increment of blowing ratio in innovative proposed jet types.