The present article involves a dual-phase-lag nonlinear bioheat model for living spherical tissue during magnetic hyperthermia. In this study, we considered temperature-dependent blood perfusion to forecast accurate hyperthermia temperature for the treatment of tumor cells. Due to the nonlinearity, this problem is handled by a finite element Runge-Kutta (4,5) technique, which is a combination of Runge-Kutta (4,5) and finite difference approaches. In this technique, we discretize the partial derivatives of space variables by using the central difference scheme. After the discretization, the current problem turns out as a system of second-order ODEs with initial conditions. Again, we convert the system of second-order ODEs into the system of first-order coupled ODEs. Then, we employed the RK (4,5) scheme to resolve the problem completely for time interval. The result obtained by the present numerical scheme is validated through an exact analytical result in a special situation, and it is noticed that both results are very close to each other. After analyzing the results, we found that when tumor cells are treated by magnetic hyperthermia, temperature-dependent blood perfusion significantly affects the hyperthermia temperature. It is seen that the impact of quadratically temperature-dependent blood perfusion is more effective than the linearly temperature-dependent types of blood perfusion. The convection effect due to the quadratically temperature-dependent term in the blood perfusion is greater than the other terms. The magnetic heat source is crucial in regulating the temperature inside the living tissue for determining hyperthermia temperature. By rising the ratio of lagging time due to heat flux (tau q) and temperature gradient (tau t), the temperature profile drops, and these effects are observed initially for a few seconds.
Deterioration in efficiency caused by elevated temperatures of solar photovoltaic (PV) panels limits their utilization in hot environments and in concentrated irradiance applications. This article proposes cooling PV panels without introducing bulky or costly components. The cooling effect is achieved through a basin attached below the panel. The basin is equipped with elliptic enclosures (EE) containing phase change material (PCM). The EEs are set at a distance below the PV allowing for a small gap. The EEs can rotate around their axes inducing motion that boosts PV cooling. This motion is sought to enhance heat transfer from the hot lower surface of the PV to the fluid and from the fluid to the PCM. The EE also acts as a constant temperature heat sink storing heat rejected by the panel during the day and rejecting this stored heat to the ambient (through water and then through the basin's lower surface) during the night. The current article discusses the effect of the number of EEs, their distance below the panel surface and their rotational speed on the PV electrical output. System performance is assessed numerically for ambient conditions of Cairo, Egypt at noon of the summer solstice. The best design is identified based on the highest overall efficiency, considering the enhancement in output power due to cooling and the power consumed in overcoming friction between the EEs and the surrounding water. The results were used to generate an optimum case resulting in 13.5% enhancement over an uncooled PV panel.
This study investigates the unsteady flow and heat transfer characteristics of a nanofluid composed of Fe3O4 (iron oxide) nanoparticles suspended in a base fluid, flowing over an inclined stretching sheet within a porous medium. The effects of magnetic fields, radiation, velocity slip, and convective boundary conditions are analyzed, along with the influence of different nanoparticle shapes (lamina, tetrahedron, and hexahedron) on heat transfer. By applying similarity transformations, the governing partial differential equations are reduced to ordinary differential equations and solved numerically. MATLAB is used to visualize velocity and temperature profiles and to tabulate skin friction coefficients and heat transfer rates. The results show that an increase in the magnetic field strength leads to a reduction in velocity, while higher porosity levels further decelerate the flow by 15%. Furthermore, increasing the Biot number (which measures convective heat transfer at the boundary) from 1.0 to 1.5 enhances heat transfer rates for lamina, tetrahedron, and hexahedron-shaped nanoparticles by 7.2%, 6.32%, and 5.79%, respectively. These results highlight that lamina-shaped nanoparticles significantly boost heat transfer rate compared to other shapes. This research provides valuable insights into nanofluid transport in porous media, with implications for energy efficiency and materials science.
Under the influence of an external magnetic field, the interaction between liquid metal magnetofluid (LMM) and the magnetic field gives rise to induced current, Lorentz force, and Joule heat in LMM, thereby affecting its flow and heat transfer characteristics. In order to investigate LMM boiling heat transfer under a magnetic field, a computational method was developed by integrating the Volume of Fraction (VOF) interface capture method, phase change model, and electromagnetic field model for solving LMM boiling flow. The boiling thermodynamic characteristics of LMM on a horizontal plate and horizontal cylinder were calculated. Under the magnetic field, induced current generates Lorentz force. Because of this force, bubble growth and detachment are delayed significantly. Simultaneously, due to the suppression effect caused by Lorentz force, there is a slight reduction in heat transfer performance as the strength of the applied magnetic field increases. Our understanding of LMM boiling heat transfer under the control of magnetic field is furthermore enhanced.
This article presents an investigation into the impact of viscous dissipation on thermogravitational convection within a U-shaped enclosure. The enclosure is filled with a water-based TiO2-CoFe2O4 hybrid-nanofluid, with baffles positioned at two corners of the lower surface. Four geometrical arrangements (Case-I, Case-II, Case-III, and Case-IV) are examined. The aim is to elucidate the intricate interplay between several aspects, including fluid dynamics, heat transfer, and the presence of hybrid nanofluids. The governing equations are examined using a higher-order compact formulation. The formulation is a finite difference compact scheme which is fourth order accurate in space coordinate. This scheme can capture the flow physics in low grids which reduces the computational cost. The reliability of our in-house program is established through rigorous verification procedures, encompassing grid independence tests and comparisons with experimental and theoretical findings from researchers. The novel importance of the work encompasses six key elements: the unique properties of hybrid nanofluids, the geometric arrangement of baffles, the U-shaped enclosure design, the influence of viscous dissipation (0 <= Ec <= 0.03), interactions with magnetic fields, and the utilization of advanced compact computational techniques, across a spectrum of parameters. The findings unveil that viscous dissipation impedes the thermal diffusion, precipitating a decline of thermal performance up to 36.34% in Case-I, 17.83% in Case-II, 15.70% in Case-III, and 5.23% in Case-IV with the upsurge of Eckert value. The mean Nusselt number in variation of magnetic field compared to without magnetic field results discernible increase of 8.53% in Case-II and 9.97% in Case-III. Furthermore, the strategic placement of corner baffles emerges as a pivotal mediator in the interplay of magnetic effect and fluid transportation. Remarkably, across the cases (II, III and IV), a discernible upward trajectory in the Nusselt number ratio is discerned concomitant with the escalation of nanoparticle volume fraction, which augmenting thermal efficacy.
The cryogens generally exhibit different nature of boiling from the conventional liquids. The boiling process in cryogens sometimes don't exhibit the appropriate heat transfer due to transition into film boiling regime. In the present work, film boiling characteristics of liquid nitrogen (a widely used cryogen) were examined at different gravity conditions and under the influence of an electric field. Employing continuum-based numerical simulations and utilizing the coupled level set and volume of fluid (CLSVOF) method for interface tracking, the effects of wall superheat and reduced gravity on bubble dynamics during film boiling near the critical pressure were investigated. The heat flux values obtained from the simulations were compared with the experimental results. It was observed that under lower gravity levels, the number of bubble formation sites decreases, and the apex height of the bubble increases, resulting in slower detachment frequency and reduced average heat transfer rate. An external electric field was found to be effective in controlling the heat transfer rate in such cases. The effect of the electric field was found to be more prominent in lower gravity levels.
Enclosures that contain both fluid and porous regions are utilized in various industries and geophysical processes to enhance heat and mass transfer. These enclosures find applications in fields such as geothermal engineering, drying of porous solids, cooling of electronics, metal solidification, and many others. In line with the motivation behind these applications, the present study explores twofold diffuse phenomena in a porous trapezoidal enclosure with the impact of thermal radiative heat flux. A numerical investigation was carried out using a finite difference methodology integrated into a computational code for numerical simulation. The simulation aimed to investigate the impact of nanoparticle shape factor on the effectiveness of a porous medium, which is exposed to two distinct objectives: enhancing heat transfer and optimizing mass transfer within a fluid-saturated porous medium. This research conducts a meticulous parametric exploration, underscoring the pivotal roles played by Darcy number (Da), nanofluid shape factor (m), Rayleigh number (Ra), thermal radiation (Rd), buoyancy ratio (Nr), and Lewis number (Le) in shaping the dynamics of flow, heat, and concentration transfer. The outcome of this analysis yields an exhaustive dataset encompassing Nusselt and Sherwood numbers can be written as mathematical functions based on the parameters we talked about earlier. The study reveals that nanoparticle shape significantly influences heat and mass transfer in double diffusive convective flow within porous enclosures. Blade-shaped nanoparticles show increased efficiency, while parameters like Darcy, thermal buoyancy, influence flow patterns.
In this investigation, we analyzed heat transmission of a magnetic fluid flow subject to the impact of a magnetic field in a minichannel having one inlet and two outlets and which is bent at a certain position. Effect of Reynolds number, magnetic field intensity and position of magnets on heat transmission and flow dynamics was explored. The volume fraction of the magnetic nanofluid Fe3O4 has the value 0.6%. Magnetic fluid used aims to cool the minichannel studied. Strength of the magnetic field takes values 800, 1200, 1400 respectively while the Reynolds number varies in an interval from 150 to 210 and for this study, three different positions of the magnets corresponding to a single source of the magnetic field followed by a fourth corresponding to a doublet of sources are examined. Results obtained show a maximum improvement in heat transmission rate of 13.95% for a source situated at 7.5 mm, an improvement in heat transmission of 14.15% for a source positioned at 15 mm, an intensification of heat transfer for a source placed at 27.5 mm of 25.51% and a rise in heat transmission of 16.23% for a doublet of sources placed at 7.5 mm and 15 mm respectively. For magnetic field used, it is noticed a diminution in pressure loss which results from fluid becoming unadhered to the surface located at the bottom of the channel. According to results found, a better heat transmission is obtained once magnets are positioned toward channel outlet. These results contribute to the improvement of the thermal efficiency of several energy systems and in particular the case of small compact exchangers with low Reynolds number flow. It can also represent a flow of fluid in a main artery having a narrowing and a bifurcation at the exit.
The nonlinear mixed convection of thermal and solutal distributions through porous microchannels is a critical area of investigation due to its significant applications in the cooling of microchips, drug delivery systems, and solar thermal collectors. A non-Newtonian magneto-Ellis fluid is employed in the channel flow, highlighting the sophisticated dynamics and advanced control mechanisms within the system. This entropy-optimized reactive flow study examines the effects of nonlinear radiative heat flux, applied magnetic fields, and temperature-dependent heat sources on energy distribution. The concentration equation incorporates thermo-diffusion and reaction parameters. Our study reveals that as permeability K grows, the Bejan number (Be) suggests a predominance of heat conduction over convection near the right wall. Furthermore, the contour lines indicate that the heat transfer rate is more responsive to the variations of the conduction-radiation parameter compared to the frictional heating effect. However, the conduction-radiation parameter shows a negative correlation with the mass transfer rate.
The cooling of thermal-end components is a critical research focus within the field of aero-engine technology. This research performs a numerical analysis of the film-cooling structure of the central cone under real operating conditions of aircraft engines. Three critical structural parameters influencing the wall temperature profile are selected. A genetic algorithm is introduced to solve the proposed adiabatic film-cooling efficiency correlation, and the convective heat transfer coefficients on both sides of the conical surface are investigated, taking into account the segmented and gradually tapered features of the central cone. A rapid one-dimensional wall temperature calculation method based on numerical computation, film-cooling theory, and genetic algorithm is proposed. The analysis reveals that when the blowing ratio is 0.8, the total average relative error between the one-dimensional wall temperature calculation method and the traditional CFD calculation for the overall film-cooling efficiency along the path is 6.75%. As the blowing ratio increases, the accuracy of the one-dimensional wall temperature calculation method improves, with an overall average relative error of only 4.27% at a blowing ratio of 2.0. Within the study range, the overall average error of the one-dimensional wall temperature calculation method remains below 5.4%. Additionally, the stochastic models are introduced to validate the one-dimensional wall temperature calculation method, confirming its applicability and accuracy. This method can achieve rapid calculations of the one-dimensional wall temperature for the central cone film-cooling structure under different structural parameters a range of and blowing ratios. It provides an approach and framework for quickly calculating wall temperatures in complex models, which is valuable for engineering applications.
This study presents a computational simulation of unsteady Casson-Williamson nanofluid flow in a magnetic non-isothermal upward vertical cone with uniform mass diffusion. The significance of thermal radiation, Joule heating, and chemical reactions are analysed. The nonlinear dimensional partial differential equations for the given flow model are transmuted into dimensionless form by using non-dimensional parameters, and are solved with the Crank-Nicolson tridiagonal implicit approach. The graphical representations for each flow-defining parameters are displayed. A parametric study shows the effects of skin friction, Nusselt, and Sherwood numbers. Thermal and mass transfer performance of Casson and Williamson nanofluids are compared to characterize their behavior. Williamson nanofluid enhances the velocity profile under magnetic and radiative impacts more effectively than the Casson nanofluid. Casson nanofluid achieves greater improvement than Williamson across temperature and concentration curves.
Continuous drive for miniaturization of electronic systems requires an efficient thermal management system to handle the increase in power density. Wavy channels are used extensively in heatsinks, and they have better heat removal capabilities than straight channels, but at the expense of a higher pressure drop. The present study focuses on improving the performance of wavy-minichannel heatsinks using novel secondary channels by minimizing the pressure losses. At the trough locations of the wavy-minichannel (Case I), secondary channels (Sec) are introduced (Case II-Sec-0.4 mm, Case III- Sec-0.2 mm, Case IV-Diverge-sec, and Case V-Converge-sec). Experimental studies (Case I and Case II only) and numerical simulations (for all cases) are carried out at different Reynolds numbers ranging from Re = 190 to 1130, and the results are compared with the baseline channel. The results indicate that a significant impact is observed for cases having secondary channels in terms of pressure drop, and at lower Reynolds numbers, they outperform baseline wavy channels in terms of both heat transfer and pressure drop. At a Reynolds number of Re = 190, maximum increase in average Nusselt number is achieved by Case V, which is 13.5% higher than Case I. As the Reynolds number increases, there is a slight reduction in heat transfer performance for heatsinks with secondary channels, which is compensated by a significant reduction in pressure drop, which is favorable. The heat transfer performance of Case III is better than other cases having secondary channels at higher Reynolds numbers. A maximum reduction of 52.2% in pressure drop is observed for Case IV in comparison to the baseline channel. Performance Evaluation Criteria indicates superior heat transfer performance for all the cases except Case II. The introduction of secondary channels to the baseline channel helps to achieve similar heat transfer performance with a significant reduction in pressure drop.
Theoretical analysis has been conducted on the performance of buoyancy motivated heat and fluid movement within a rectangular cavity occupied with air, water, and engine oil, separately. This analysis is supported by applying a spatio-temporal variation of the temperature profile from the bottom, which is particularly necessary for the design of thermally efficient chemical reactors. The crucial purpose of this revision is to create a thermally active region inside the cavity that facilitates the dissipation of heat from high energy-density systems. For investigating the flow behavior inside the cavity, various relevant parameters such as stream function, isotherm, Nusselt number (Nu) along the bottom wall, local and total irreversibility formation have been determined while varying Rayleigh number (from 103 to 106) and period of heating (from 4 to 0.5). The significant findings of this study include the axial displacement of the circulations due to the influence of the time-varying temperature dispersal applied along the bottom wall, and the formation of universal circulations instead of small circulations caused by the interplay between the buoyancy and the inertia forces of fluid movement.
With the development of convenience stores based on their convenience, considering energy-saving designs for convenience stores is crucial for national energy-saving policies. In this article, in addition to energy-saving, the customer experience in convenience stores is also discussed. PHOENICS is used for numerical simulations in the current research report. This article uses the basic k-epsilon turbulent model in CFD to simulate temperature and energy variations in convenience stores (commercial buildings). Considering the phenomenon of flow mixing within the air curtain zone, it is essential to include a buffer around the boundary, which is subsequently proposed in the CFD simulation. The temperature setting is based on Taiwan climate temperature. Through temperature and velocity analysis, the study discusses considerations for customer experience. The results from CFD show that a well-designed air curtain at the entrance of a convenience store can reduce energy loss, making it an effective energy-saving tool. In addition, setting the air curtain temperature to 25 degrees C has been found to significantly contribute to energy savings. The simulation results provide better settings for convenience store air conditioning operations. By analyzing the problem and identifying possible optimal solutions, the use of CFD can effectively improve convenience store energy costs.
The industrial and commercial applications of solar energy are expanding rapidly, making entropy optimization in solar energy-powered mechanical systems critical for improving the efficiency of energy-harnessing devices. This study investigates heat transfer and the unsteady flow of a magnetized CNT nanofluid with variable thermal conductivity over a rotating sphere under the influence of solar radiation. The similarity solutions of the leading system of non-linear PDEs are obtained numerically via bvp4c scheme after reverting into nonlinear ODEs. A comparative analysis is conducted between MWCNT and SWCNT nanofluids, with graphical representation of flow characteristics. The results reveal that reducing the flow acceleration parameter optimizes fluid friction irreversibility, while increasing the magnetic field parameter reduces total entropy production of the system. Moreover, a 10% hike in MWCNT and SWCNT concentration enhance the wall shear stress by 15.86% and 17.68% respectively in the perpendicular direction to the flow. Meanwhile, with the same hike in MWCNT and SWCNT concentration, the rate of heat transportation gets boosted by 7.59% and 9.98% respectively. Other upshots reveal that the thermal boundary layer growth escalates with the solar radiation parameter and the variable thermal conductivity parameter, also the rate of growth is quite faster for SWCNT nanofluid in comparison to SWCNT nanofluid. The comparisons with existing literature are also made, which showcase an excellent harmony between the results.
The battery thermal management system (BTMS) of lithium-ion batteries is crucial for ensuring the safety, longevity, and energy efficiency of the batteries. This research designs a dual-layer counterflow BTMS and proposes a universally applicable optimization process. The study compares various configurations of liquid-cooled plate layers and coolant flow directions, focusing on the influence of liquid-cooled plate structure and coolant mass flow rate on cooling effectiveness. The results show that the dual-layer counterflow design significantly reduces the overall temperature of the battery pack and improves temperature uniformity. To further enhance BTMS performance, mathematical models were established using surrogate models, and optimization of the liquid-cooled plate structure and coolant parameters was conducted using the NSGA-II and MOPSO algorithms. The optimization results for NSGA-II show that the maximum battery pack temperature was reduced from 37.8503 degrees C to 34.9450 degrees C, the temperature difference between batteries decreased from 2.7912 degrees C to 1.2905 degrees C, and the maximum pressure drop was reduced from 135.0663 Pa to 87.2927 Pa. The MOPSO algorithm yielded similar improvements, with the maximum temperature reduced to 34.9611 degrees C, the temperature difference decreased to 1.3095 degrees C, and the pressure drop reduced to 86.8021 Pa. These improvements enhance temperature uniformity and effectively reduce the energy consumption of the cooling system, thereby lowering the overall energy consumption of electric vehicles.
The Eddy Dissipation Concept (EDC) model in FLACS software is used to analyze the influence of three different cross-sectional shapes on explosion process parameters in a semi-closed pipeline laying space. The following nine aspects are analyzed: promotion of overpressure wave, promotion of expansion flame front, flame promotion of distance, promotion of expansion flame front, flame promotion of speed, maximum overpressure of pipe, maximum temperature of flame, maximum combustion rate of gas, and maximum velocity of flame. The results indicate that under the methane concentrations and laying space sizes studied in this article, the explosion consequences caused by methane/air mixture in circular cross-sectional laying space are the most severe, followed by circular-rectangular cross-sectional laying space. The impact of laying space on rectangular cross-sections is the minimum. From the perspective of explosion consequences, the rectangle can be prioritized for the laying space shape of pipelines used for maintenance and repair. During the process of explosion accidents, it can effectively reduce the degree of injury to operators in the pipeline laying space.
The effects of viscous dissipation and uniform internal heat source on the onset of double diffusive convection in a horizontal porous layer is investigated. In this problem, the boundaries are assumed to be permeable. The stability analysis is performed in two approaches: One is the linear stability theory and other one is the nonlinear stability theory. The energy method is implemented to perform the nonlinear stability analysis. The literature on the effect of viscous dissipation on the onset of double diffusive convection using nonlinear stability analysis is very limited. The current article aims to address this gap. The eigenvalue problem arising from the linear instability analysis is solved numerically by using Chebyshev-Tau spectral method; whereas the eigenvalue problem arising from the nonlinear stability analysis is solved numerically by using shooting and Runge-Kutta methods. The thresholds for both the linear and nonlinear stability analyses are compared. It is shown that the effect of internal heat source causes the instability to the system. The effect of viscous dissipation on the onset of convection becomes significant when the basic state velocity is non-zero. Specifically when Q not equal 0, in the case of downward throughflow, the effect of viscous dissipation stabilizes the system; whereas in the case of upward throughflow, viscous dissipation destabilizes the system. Moreover, Lewis number Le has a insignificant stabilizing effect on the system.
Engineering case studies have demonstrated the efficiency of multi-well enhanced geothermal systems (EGS) for large-scale geothermal energy utilization. However, comprehensive research on optimal well arrangement methods for these systems is still lacking, especially concerning the design and optimization of small well groups in limited areas. To address this gap, a mathematical model for seepage heat transfer in EGS has been developed by coupling the groundwater flow equation with the porous medium heat transfer equation. This model has been validated through micro seepage heat transfer experiments. The study also uncovers fundamental principles governing seepage heat transfer in EGS. Numerical simulations based on this model are conducted, exploring various well numbers and arrangement methods under the same thermal storage conditions. A method for designing and optimizing well arrangements in multi-well EGS is proposed, with evaluations based on annual average production efficiency. It is found that placing the production well at the center of the plane significantly improves annual average heat production efficiency compared to positioning it near the injection well. Therefore, the "five injection and one production" arrangement is recommended, with the production well as close to the center as possible between two adjacent injection wells. This study provides an optimization analysis method for small well groups and multi-well EGS, focusing on production capacity, and offers valuable guidance for designing and optimizing EGS in large-scale geothermal fields.
