Mixed Flow Research Articles

Numerical investigation of MHD mixed convection in an octagonal heat exchanger containing hybrid nanofluid

Nowadays, the advancement of heat transmission for the heat exchanger device is an important field of research for many researchers. In this work, a numerical study has been conducted to investigate the thermal performance of a mixed convective flow through the octagonal heat exchanger covered by hybrid nanofluid (Cu-TiO2-H2O). A magnetic field has been introduced inside the cavity to investigate the mixed convective hydrodynamics heat flow characteristics. The nanofluid cores absorb/release energy to manage heat transmission by increasing or decreasing inside the cavity domain as the host fluid and dispersed hybrid nanofluid circulate within the cavity. After transforming the governing equations into a generalized, non-dimensional formulation, the finite element approach is utilized to solve the associated equations. Additionally, response surface methodology is also applied to test the responses of the associated factors. Heat transport was examined in relation to the effects of nanofluids fusion temperature, boundary wall properties, Reynolds number, Hartmann number and nanoparticle volume fractions. The outcomes of this study are analysed by measuring streamline profiles, isotherms, average Nusselt number, velocity profile, and 2D and 3D response surfaces of the computational domain. The underlying flow controlling parameters for instance Reynolds number (10 ≤ Re ≤ 200), Hartmann number (0 ≤ Ha ≤100), and nanoparticle volume fractions (0 ≤ ϕ ≤ 0.1), the influences have been considered. The findings also reveal that the thermal performance is being boosted due to augmentation of Re and ϕ, but reverse behavior is noticed for Ha. Furthermore, the response surfaces obtained from response surfaces methodology express that the Re and ϕ have shown positive influence, and Ha has shown negative influence on Nuav. Utilizing a hybrid nanofluid of Cu-TiO2-H2O increases the heat transfer capacity of water to 25.75 %. Moreover, the findings could guide to design of a mixed convective heat exchanger for industrial purposes.

Modeling and predicting heat transfer performance in bioconvection flow around a circular cylinder using an artificial neural network approach

The current research aims to study the heat transfer rate in mixed convection flow of viscous fluid along a vertical cylinder containing swimming microorganisms and velocity slip effects. The thermal and solutal processes are examined using gyrotactic microorganisms, chemical reaction and slip conditions. The non-linear (PDEs) of the governing flow are transformed into set of highly nonlinear (ODEs) by employing appropriate similarity transformations, which are then resolved computationally by Runge-Kutta-Fehlberg 4th order toward with shooting approach. The predicted solution is derived using the Levenberg-Marquardt scheme combined with a backpropagation neural network (LMS-BPNN). The labelled data sheet is divided into three parts: 80% data is used for training, 10% for validation and 10% for testing. The performance of the proposed AI-based LMS-BPNN is examined in term of MSE for considered scenarios. An optimal solution is achieved at 675, 397, 727, 647, and 711, epochs, while performance in terms of MSE for these epochs is to be 1.06×E−9, 8.47×E−10, 9.20×10−9, 9.94×E−10,and 9.09×10−10. The assigned computational valuations and ANN valuations are in excellent alignment than those existing studies on numerous special cases. The predicted solution with AI-based technique LMS-BPNN is reliable, well-organized, and easy to handle the thermal and solutal transport analysis of flow across a stretchable cylinder. The validity of proposed LMS-BPNN algorithm is examined with absolute error analysis and error is found to be approximately 10−4.

Numerical investigation on flow characteristics and heat transfer of mixed convection in a packed bed

Flow characteristic and heat transfer of mixed convection in the packed bed were investigated numerically comparing with the previous experimental studies. For the fixed packed bed and sphere diameters of 0.06 m and 0.01 m, the ratios of bed height to sphere diameter and Reynolds numbers were varied from 5 to 20, and from 1 to 300, respectively for both buoyance aided and opposed flows. The temperatures difference between fluid and sphere was 78.85 K. The packed bed structure was modeled by generating location coordinates through the random number with an in-house code and computational analyses were performed using ANSYS FLUENT software. Laminar mixed convection behaviors were observed: heat transfer enhancement for buoyancy aided flow and impairment for buoyancy opposed flow. For larger bed heights, even under a laminar flow condition, turbulent behaviors were observed: heat transfer impairment for buoyance aided flow and enhancement for buoyance aided flow. The same trend was observed in the analysis of turbulence intensity. Local flow analysis within the packed bed confirmed that this is due to the vortices and the wakes resulting from the interaction between mixed convection flows and the randomly stacked spheres in the packed bed. This study unveiled mixed convection phenomena accompanied by the geometric effects of the packed bed on vortices and wakes, which exhibit turbulence-like behavior.

An internal stochastic car-following model: Stochasticity analysis of mixed traffic environment

This paper investigates the impact of adaptive cruise control(ACC) vehicles on the stochasticity of human driving behavior by constructing a stochastic car-following model of human-driven vehicles (HDVs). Utilizing NGSIM dataset, the relationship between acceleration variance and space headway is analyzed, and a novel stochastic car-following model with headway is proposed to capture the internal stochasticity of drivers. Furthermore, the interaction between HDVs and AVs is explored by discussing stochasticity and stability in mixed traffic flow, using the proposed HDV model. The model parameters are calibrated based on NGSIM dataset and the simulation results indicate that the proposed stochastic car-following model can effectively reproduce the generation and propagation of traffic shocks without lane changes. Additionally, the simulations reveal that as the penetration rate of AVs increases in a lower range (0%–50%), the stochasticity of HDVs and stability in mixed traffic flow is substantially reduced. However, at higher penetration rates, increases in the AV penetration rate have a limited effect on the stochasticity of human driving behavior and the stability of mixed traffic flow. Concurrently, under conditions of low penetration rates, a smaller AV platoon size contributes more effectively to enhancing the stability of traffic flow and suppressing the stochastic behavior of HDVs. This research provides new insights for optimizing traffic flow control with automated vehicles.

Modelling connected and autonomous bus on dynamics of mixed traffic in partially connected and automated traffic environment

Since connected and autonomous buses (CABs) have great potential of being operated in partially connected environment and raise great impact on mixed traffic flow, this study develops an analytical model for modeling system dynamics of mixing connected and autonomous vehicles (CAV), human-driven vehicles (HV), and CABs in both cases of dedicated bus lane and non-dedicated bus lane, in which the impact of CABs is specifically quantified under varied levels of connected vehicle penetration. A Vissim-Matlab simulation evaluation is also developed for validating the model’s effectiveness. The results demonstrate that the proposed model performs well with an accuracy of over 85%, and it can be up to 95% in case of non-dedicated bus lane when the inflow rate is higher than 2000veh/h. Besides, the impacts of CABs’ volume, bus dwelling time, and bus stop location on the performance of mixed traffic flow are verified in two CAB operating environments. The obtained results can be used as the basis for planning and operating CABs in partially connected environment.

Mixed convection model for predicting the Nusselt number of oscillating vertical plates

In this study, we developed a mixed convection model for predicting the Nusselt number of periodically oscillating vertical plates. When a hot or cold vertical plate oscillates, a complex mixed convection flow occurs, a combination of natural and forced convection flow caused by temperature difference and oscillation, respectively. Here, to simplify the analysis, the natural convection flow is treated as a forced convection flow with a certain stream velocity. Then, by superimposing this flow on the forced convection, the mixed convection flow is approximated to a single effective forced convection flow. Based on this approximation, two closed-form correlations of the Nusselt number are suggested, each applicable to vertically and horizontally oscillating plates, respectively. To check the validity of the suggested correlations, we constructed an experimental apparatus to measure the heat transfer coefficient of oscillating plates. We validated the correlation applicable to horizontally oscillating plates using experimental data obtained from this apparatus, while the correlation developed for vertically oscillating plates was validated using experimental data obtained by previous researchers. Our model and experimental data are in good agreement within 8 % for horizontally oscillating plates and 13 % for vertically oscillating plates. To understand the influence of the Grashof and Reynolds numbers on the Nusselt number of oscillating plates, contour maps of the Nusselt number were presented with respect to the Grashof and Reynolds numbers, and then analyzed. Moreover, we suggest convection regime maps with respect to the Richardson and Prandtl numbers, which can be used to calculate the convection regime of oscillating plates. With the absence of empirical constants, the current model is applicable to all the Prandtl numbers in the range of Re<6×104 and 104<Gr×Pr<109. For this reason, our developed model can be widely used for heat transfer analysis of oscillating vertical plates under various conditions.

Leidenfrost Effect-Induced Chaotic Vortex Flow for Efficient Mixing of Highly Viscous Droplets.

Efficiently mixing highly viscous liquids in microfluidic systems is appealing for green chemistry such as chemical synthesis and catalysis, but it is a long-standing challenge owing to the unfavorable diffusion kinetics. In this work, a new strategy is explored for mixing viscous droplets by harnessing a peculiar Leidenfrost state, where the substrate temperature is above the boiling point of the liquid without apparent liquid evaporation. Compared to the control experiment where the droplet stays at a similar temperature but in the contact boiling regime, the mixing time can be reduced significantly. Moreover, it is demonstrated that the liquid mixing originates from the chaotic convection flow in the Leidenfrost droplet, characterized by the internal vortex motion evidenced by the microscale visualization. A correlation between mixing time and droplet volume is also proposed, showing a good agreement with experimental results. It is further shown that Leidenfrost droplets can be used to synthesize nanoparticles of the desired morphology, and it is anticipated that this simple and scalable fabrication approach will find applications in the biological, pharmaceutical, and chemical industries.

Mixed convective nanofluid flow and heat transfer induced by a stretchable rotating disk in porous medium

AbstractEnhancement of “heat transfer” using “nanofluid” has diverse potential applications in heat exchangers, thermal management of electric devices, cooling of tractors, solar thermal systems, manufacturing of paper, and many others. Hence, the aim of the current investigation is to explore the impacts of “mixed convection” on “nanofluid flow” over a permeable rotating disk, which is stretched radially in a porous medium. Variable wall “temperature” and “convective boundary conditions” are also considered here. This makes the present investigation different from others. The suitable “similarity transformations” are imposed to alter the governing partial differential equations into a set of coupled ordinary differential equations (ODEs). Then, these ODEs are solved numerically by the “4th order Runge‐Kutta method” using the “shooting technique” with the help of the bvp4c package in MATLAB software. The effects of fluid controlling “parameters” on “flow and thermal fields” as well as “skin friction coefficient” and “Nusselt number” are presented graphically and explained physically. Due to enhanced rotation of the disk, the radial and azimuthal velocity of the fluid increase and the temperature of the fluid decreases. Most importantly, it is observed that when the disk rotates faster than the stretching rate, the temperature of the nanofluid decreases rapidly, which has wider applications for cooling purposes. It is also noted that when the suction parameter increases its value from −1 to 1, for Ag–water nanofluid, the “skin friction coefficient” decreases by 73.56%, and the Nusselt number also decreases by 24.11%, and for Fe3O4–water nanofluids, the “skin friction coefficient” decreases by 71.25% and the Nusselt number decreases by 24.47%.

Heat transfer enhancement and pressure drop performance of Al2O3 nanofluid in a laminar flow tube with deep dimples under constant heat flux: An experimental approach

This study examines the heat transfer enhancement and pressure drop of Al2O3 nanofluid in deep dimpled tubes in both longitudinal and circumferential directions. It explores mechanisms that improve the thermal performance of this novel tube geometry. Experiments were conducted using plain and deep dimpled tubes under laminar flow with Reynolds numbers from 500 to 2250, a constant heat flux of 10,000 W/m2, and nanofluid concentrations from 0.1 wt% to 1 wt%. The findings indicate that local velocity enhancement, vortex generation, and flow rotation and mixing are the three main mechanisms that improve the thermal performance of deep dimpled tubes. The results demonstrate that a deep dimpled tube with 1 wt% nanofluid can increase the convective heat transfer coefficient by up to 3.42 times compared to a smooth tube at Re = 2250. At this Reynolds number, the Nusselt number reaches a maximum of 41.80, and the friction factor ratio increases by only 1.82. Additionally, circumferential analysis reveals how dimple-induced vortices enhance heat transfer. The results also indicate that the tube geometry modification changes the flow regime zones, allowing turbulent flow at lower Reynolds numbers near Re = 2000, as identified by Nusselt number and friction factor plots. The deep dimpled tube has a low improvement penalty, with the highest friction factor of 0.38 at Re = 500 and high thermal enhancement, resulting in a performance evaluation criterion (PEC) of up to 2.80 in the studied region. However, the deep dimpled tube is unsuitable for Reynolds numbers below 1000. For higher velocities, replacing simple tubes with deep dimpled tubes in traditional heat exchangers is highly recommended.

Efficiency and fuel consumption of mixed traffic flow with lane management of CAVs

The mixed traffic flow of connected and automated vehicles (CAVs) and human-driven vehicles (HDVs) will exist on highways for a long time, as the deployment of CAVs is gradual. To reduce the negative impact of HDVs on CAVs, the deployment of dedicated lanes has been considered an effective solution. Along with the dedicated lanes, three different lane management strategies will be formed, which are (C, H) strategy (CAVs dedicated lanes and HDVs dedicated lanes), (C, G) strategy (CAVs dedicated lanes and general lanes), and (G, H) strategy (general lanes and HDVs dedicated lanes). To evaluate the influence of dedicated lane settings on mixed traffic flow comprehensively, this paper proposes a framework for evaluating road segment efficiency and fuel consumption by considering lane management strategies. First, the possible traffic flow equilibrium states under three lane management strategies are discussed, and the characteristics of five car-following modes in mixed traffic flow are analyzed. Then, a mixed traffic flow capacity model considering platoon size is introduced to the traditional BPR function to establish a speed estimation model for mixed traffic flow and a fuel consumption estimation model for mixed traffic flow. Next, the traffic flow distribution model at the lane level in a steady state is derived for different lane management strategies. Based on the traffic flow distribution model, the speed estimation model and the fuel consumption estimation model for mixed traffic flow, which consider lane management strategies, are proposed. Finally, a numerical simulation is conducted to analyze the effects of different lane management strategies and configuration schemes on road segment efficiency and fuel consumption. The results of numerical experiments show that (1) at the same traffic demand, the operational speeds of vehicles under the (C, H) strategy and (G, H) strategy tend to increase and then decrease with the increase in the penetration rate of CAVs. While the speed of the vehicle under the (C, G) strategy increases with the increase in the penetration rate of CAVs. (2) Compared with the baseline strategy, all three management strategies can improve the operating efficiency of vehicles under certain traffic conditions. (3) At the same traffic demand, the average fuel consumption under the three strategies tends to decrease first and then increase slightly as the penetration rate increases. Increasing the number of dedicated lanes under specific traffic conditions can significantly increase the fuel consumption reduction rate under each strategy. At the same penetration rate, this advantage diminishes with the increase in traffic demand. (4) The increase in platoon size favors the efficiency of vehicle operations under different strategies. However, as platoon size increases, the marginal benefit of increasing platoon size becomes smaller and smaller. In addition, the average fuel consumption of vehicles has a low sensitivity to platoon size, and increasing platoon size may not always reduce fuel consumption.

Experimental testing and geometric optimization of a domestic cooker burning 80%Natural-Gas+20%Hydrogen

In urban pipelines, blending hydrogen into natural gas has been considered as an effective way of hydrogen usage to reduce carbon emission on household appliances. However, few studies, especially experimental ones are dedicated to address the characteristics of a typical domestic cooker due to the transition from natural gas to 20%hydrogen-enriched natural gas. This study experimentally investigated the changes in terms of the gas flow rate, flame temperature, heat transfer and emission characteristics of a domestic cooker as a result of such transition.Using a self-developed gas blending system, the flow rates of the both the mixed fuel and its components are obtained. The data shows that after blending hydrogen, the mixed gas flow rate becomes higher. Compared to the original cooker burning natural gas, hydrogen blending results in a decreased natural gas flow rate, leading to lower carbon emission. In addition, the thermal input to the cooker is lowered and hydrogen blending leads both the inner and outer combustion zones of the flame to shorten while the flame temperature to increase.As an attempt to optimize the performance of the cooker, the effects of wok stand height on heat transfer efficiency and NO/NOx/CO emissions are examined. It is found that the cooker fueled by 20%hydrogen-enriched natural gas exhibits lower heat transfer efficiency, higher NO/NOx emissions and lower CO emission. According to the fact that the heat transfer efficiency increases at lower wok stand height, the wok stand height is lowered from its original 7 cm–6 cm and 5 cm. The finding indicates that when the wok stand height is moderately decreased to 6 cm, NO/NOx emissions decrease and CO emission is only marginally increased. This study proposes that when natural gas is replaced by 20%hydrogen-enriched natural gas on a swirl flame cooker, the wok stand height can be slightly lowered to exploit the advantages of blended hydrogen combustion.

Impact of rupture disk morphology on self-ignition during pressurized hydrogen release: A numerical simulation study

In the study of self-ignition during pressurized hydrogen release, the morphology of the rupture disk alters the flow and mixing processes of the gas jet, as well as the development of shock waves, thereby affecting the occurrence of self-ignition. This study employs the LES method based on the RNG-SGS model, EDC model, and NUIMech1.1 H2 combustion mechanism to investigate the flow mixing, shock wave development, and self-ignition phenomena under three different the rupture disk morphologies. The research findings indicate that as the growth trend of the rupture disk rupture ratio increases, the propagation speed of shock waves within the tube and the compression speed of the air and hydrogen-air mixing region accelerate, resulting in an earlier occurrence of self-ignition. A more complex rupture morphology leads to higher mixing rates between hydrogen and air and increased complexity of shock waves. Self-ignition initially occurs in the fuel-lean region of the boundary layer, followed by ignition at the center of the tube. The characteristic number of rupture disk is proposed to describe its impact on the self-ignition time. The competitive relationship between the two elementary reaction pathways of oxygen influences the development of the flame.

Analysis of refrigerant/lubricant distribution and operating characteristics of a rotary booster for data center free cooling

A booster-driven loop free cooling system plays a crucial role in enhancing data center energy efficiency and reducing emissions due to the special booster with low pressure ratio as a vital driving component. And the impact of lubricant and its fraction on the booster operation are the key points under low pressure ratio, as well as lubricant distribution. In this paper, the refrigerant/lubricant two-phase mixing flow in the working chamber of a booster was investigated under low pressure ratio for data center free cooling. The volume of fluid (VOF) multiphase flow model combining the working chamber of the rotary booster and discharge valve was built up to analyze the dynamic characteristics of the booster under free cooling conditions. The effect of lubricant fraction and its working frequency on the operating indexes (exhaust temperature/pressure, mass flow rate, volumetric efficiency, indicated specific work, energy efficiency ratio) were studied. The lubricant distribution and its changes for different angles and frequencies were presented. The results indicate that it can improve the thermal performance of the booster effectively with appropriate volume fraction of lubricant. The lubricant in the two-phase flow reduces the inner temperature and pressure in the booster working chamber, which changes the exhaust pressure and volumetric efficiency as well as the cooling capacity. The exhaust pressure and the mass flow rate increase notably for the refrigerant/oil mixture with the increasing lubricant volume fraction, while other performance indexes decrease. The exhaust pressure and the mass flow rate increase by 0.51 % and 47.14 %, separately, when the lubricant volume fraction raises from 0 to 5 % at operating frequency of 50 Hz. Whereas, the exhaust temperature, refrigerant mass flow rate, volumetric efficiency, indicated specific power, cooling capacity and EER decrease by 18.11 %, 4.81 %, 47.14 %, 38.94 %, 4.81 % and 26.36 %, respectively. The investigations can support the lubrication and sealing of the booster with low pressure ratio for free cooling to reach efficient and reliable operation.

Dynamic heat transfer characteristics of printed circuit precooler in supercritical CO2 Brayton cycle

The dynamic characteristics of heat exchangers are critical in supercritical CO2 Brayton cycle, especially in the precooler where significant thermophysical property variations occur. However, few studies have comprehensively analyzed the dynamic heat transfer characteristics in precooler, particularly with respect to the detailed flow and thermal field evolution. A three-dimensional numerical model was developed to study the dynamic performance of a printed circuit precooler, with an emphasis on the impact of thermophysical properties. The study examines responses to abrupt changes in CO2 and water inlet temperature, as well as mass flux variations. Results show that the precooler exhibits rapid response characteristics with mild fluctuations in heat transfer parameters and flow structure. Notably, the large specific heat near the critical point results in minimal variation in CO2 outlet temperature despite abrupt increases in CO2 inlet temperature, thereby enhancing system stability. Conversely, a decrease in CO2 mass flux causes a transition from forced convection to mixed flow, with strengthened buoyancy effects and decreased entropy production. These variations lead to significant changes in CO2 outlet temperature, posing potential challenges to system stability under CO2 mass flux step change conditions. The heat transfer shows a relatively lower response rate to parameter changes of water compared to CO2. Although variations in water parameters have a negligible effect on CO2 heat transfer, they influence the overall heat transfer coefficient. The dynamic heat transfer characteristics of the precooler presented in this paper address research gaps left by 1D numerical and experimental studies, which have provided limited information on flow and thermal fields during dynamic processes. These insights are essential for understanding the dynamic behavior of the entire system.

Study on nonuniform tip clearance in mixed flow compressor

In compressed air energy storage system, the inevitable axial vibration during the frequent start-stop of compressor leads to circumferential nonuniform tip clearance formation, which significantly impacts compressor performance. This paper utilizes numerical simulation to study the overall performance and internal unsteady flow field of a mixed flow compressor with 4 different eccentricities and compares them with the original model. The results indicate that the eccentricity of blade tip clearance has little effect on pressure ratio and isentropic efficiency of the mixed flow compressor, but has an important impact on its stall margin. Specifically, when the eccentricity is 70 % of the blade tip clearance, the compressor stall margin is reduced by 5.96 %. The circumferential distribution of tip relative leakage aligns with the circumferential variation of tip clearance height. The average tip relative leakage increases gradually with the increase of eccentricity, and its growth rate also increases gradually with the increase of eccentricity. There are two peaks and valleys in the radial force distribution of a single blade, while the axial force of a single blade is consistent with the change in circumferential tip clearance height. These findings can provide valuable guidance for subsequent compressor design and operation.

An inquiry into transport phenomena and artificial intelligence-based optimization of a novel bio-inspired flow field for proton exchange membrane fuel cells

Achieving an effective flow field configuration is requisite to ensure the optimal performance of a proton exchange membrane fuel cell (PEMFC). Herein, an unprecedented bio-inspired flow field is offered to improve species transport and enhance the power density of PEMFCs in order to provide a pathway for effective utilization of them. The flow field consists of two twin parts, resembling the lung structure, and a repeating converging-diverging pattern, so-called “converging-diverging lung-inspired serpentine (CDLIS).” Utilizing multiphase computational fluid dynamics, this study delves into the transport phenomena and evaluates the comprehensive efficacy of a three-dimensional PEMFC. The CDLIS flow field considerably enhances both crosswise and lengthwise mass transfer by inducing several favorable flow mixing phenomena and improving reactant's velocity distribution. The output power of CDLIS exhibits a substantial increase of 10.87%, 43.63%, 12.22%, 12.83%, 12.52%, and 13.8% compared with the simple serpentine, parallel, two-path serpentine, four-path serpentine, lung-inspired serpentine, and combined parallel-serpentine flow fields, respectively. Due to its highly efficient mass transfer capabilities, enhanced convective mass flow, and outstanding current density, CDLIS possesses the most effective water management and the lowermost flooding risk. To further improve the performance of the PEMFC, artificial intelligence codes based on the non-sorting genetic algorithm II (NSGA II) and a surrogate analytical model are developed to optimize the operating conditions of CDLIS at the limiting current density situation where concentration losses impede the mass transfer of reactants. The target parameters for optimization are current density, water saturation (WS), and oxygen transport resistance (OTR). Under optimum conditions, a remarkable current density of 6.35 A cm−2, a low WS of 0.043, and a reduced OTR of 5.06 s m−1 are obtained.

Entropy generation in newtonian vs non-newtonian nanofluid flow under vibration

Numerical investigation into the effects of vibration on heat transfer and entropy generation in Newtonian and Non-Newtonian nanofluid flows through pipes reveals enhanced heat transfer via intensified fluid agitation and improved particle dispersion. Thermal entropy generation analysis shows reduced irreversibility in vibrated flow, indicating improved flow mixing. Vibration enhances heat transfer by intensifying fluid agitation and promoting particle dispersion near the wall, resulting in a significantly more uniform temperature distribution along the pipe, approximately 100 times more than steady-state flow. This study underscores vibration’s potential to optimize heat transfer and reduce entropy generation in nanofluid systems, emphasizing velocity and rheological impacts. Comparison of vibrated flow to steady-state flow for Newtonian and non-Newtonian fluids reveals significant improvements under vibration, particularly at lower Reynolds numbers where non-Newtonian fluids exhibit pronounced effects. Future research directions include exploring thermal radiation’s impact on entropy generation, analyzing different nanofluid compositions, and investigating varied boundary conditions and geometries to advance understanding in this field. This study provides valuable insights into the complex interplay among vibration, fluid dynamics, and heat transfer in nanofluid flows. Its findings have practical implications for optimizing thermal management systems in diverse engineering applications.

Development of a Portable Residual Chlorine Detection Device with a Combination of Microfluidic Chips and LS-BP Algorithm to Achieve Accurate Detection of Residual Chlorine in Water.

Chlorine is widely used for sterilization and disinfection of water, but the presence of excess residual chlorine in water poses a substantial threat to human health. At present, there is no portable device which can achieve accurate, rapid, low-cost, and convenient detection of residual chlorine in water. Therefore, it is necessary to develop a device that can perform accurate, rapid, low-cost, and convenient detection of residual chlorine in water. In this study, a portable residual chlorine detection device was developed. A microfluidic chip was studied to achieve efficient mixing of two-phase flow. This microfluidic chip was used for rapid mixing of reagents in the portable residual chlorine detection device, reducing the consumption of reagents, detection time, and device volume. A deep learning algorithm was proposed for predicting residual chlorine concentration in water, achieving precise detection. Firstly, the microfluidic chip structure for detecting mixed reagents was optimized, and the microfluidic chip was fabricated by a 3D-printing method. Secondly, a deep learning (LS-BP) algorithm was constructed and proposed for predicting residual chlorine concentration in water, which can realize dual-channel signal reading. Thirdly, the corresponding portable residual chlorine detection device was developed, and the detection device was compared with residual chlorine detection devices and methods in other studies. The comparison results indicate that the portable residual chlorine detection device has high detection accuracy, fast detection speed, low cost, and good convenience. The excellent performance of the portable residual chlorine detection device makes it suitable for detecting residual chlorine in drinking water, swimming pool water, aquaculture and other fields.

Thermophoresis &amp; Soret-DuFour on MHD Mixed Convection of a Nano Fluid with a Porous Medium over a Stretching Sheet with a Non-Uniform Heat Source/Sink

This work aimed to examine the effects of thermal diffusion (Soret) and diffusion-thermo (DuFour) on MHD mixed convective flow of a viscous nanofluid across a stretching sheet under a magnetic field embedded in a porous medium in the presence of non-uniform heat source/sink and chemical reaction. The governing equations are transformed into a set of ordinary differential equations using the similarity transformation approach. They are subsequently resolved computationally by use of the efficient Keller box method. The effects of different physical factors on concentration, temperature, and velocity profiles are graphically shown. Increasing Du values decreases temperature, although concentration profiles indicate the reverse. As temperature rises, the chemical reaction parameter Kr values increase, while the concentration profile decreases. The temperature was found to rise when the space-dependent (A1) and temperature-dependent (B1) parameters for heat source/sink increased. Additionally, a tabular presentation of the skin friction coefficient, Nusselt number, and Sherwood number behaviour is provided. Mixed convection heat and mass transfer flows are very important in manufacturing for designing reliable equipment, nuclear power plants, gas turbines, and various propulsion devices for aircraft, rockets, satellites, and spacecraft. The effects of non-uniform heat sources/sinks, thermophoresis, and chemical reactions on mixed convection flow play an important role in space technology and high-temperature processes.

Impacts of finned rotating cylinder on hydrothermal flow of hybrid nanofluids in a vented cavity based on dynamic mesh approach

This study aims to explore and enhance the understanding of how finned rotating cylinders impact mixed convection of the hydrothermal flow and heat transfer of hybrid nanofluids in a vented cavity. The significance of this study contributes to the advancement of increasingly efficient and productive thermal control mechanisms in diverse industrial sectors employing rotating cylinders. Simulations employ a dynamic mesh approach to model the flow domain and boundary motion of the rotating bladed cylinder based on the finite volume technique. The presented results underwent a rigorous comparison with existing related works in the open literature. The chosen working fluid is a Newtonian hybrid nanofluid composed of SiO2-Al2O3 suspended in water. Various configurations of cylinder locations and sizes are examined, alongside a broad spectrum of associated variables with certain ranges. These parameters with defined ranges are; Reynolds numbers (2 × 102 ≤ Re ≤ 1 × 103), cylinder radius (0.1 ≤ R≤0.3), cylinder locations (0.25 ≤ δ ≤ 0.75), spinning speeds (− 3 ≤ Ω ≤ 3), and nanoparticle concentrations (0 ≤ φ1 ≤ 0.03 and 0 ≤ φ2 ≤ 0.03). The results indicate significant impacts of Reynolds numbers (Re), Grashof numbers (Gr), cylinder radius (R), location (δ), spinning speed (Ω), and the number of blades on the hydrothermal characteristics. The major finding states that the cylinder radius of 0.3 for Case 5 with five fins provides the greatest enhancement of mixed flow and relatively maximum heat transfer rate. Furthermore, increasing concentrations of nanoparticles (φ) of hybrid nanofluids further improves the thermal performance.