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This paper focuses on researching the various factors that influence the material melting rate during the hot air melting process. To achieve this purpose, the paper proposes a melting model for Acrylonitrile-Butadiene-Styrene (ABS) plastic under hot air heating based on Computational Fluid Dynamics (CFD). Orthogonal experiments were conducted based on the parameter range of each factor obtained in the pre-experiment. The results showed that the outlet distance, hot air velocity, hot air temperature, and their interaction items are important factors that affect the melting rate of ABS materials. Based on the simulation results, a multiple nonlinear regression model was constructed to predict the melting rate under different parameters. Comparing the simulation values with the predicted values of the multiple nonlinear regression model, the error between the two was no >10%, indicating the effectiveness of the prediction model. The research results can help guide the hot air welding melting process for different materials and characteristics, and provide a certain reference value for the development of hot air welding technology. • Welding of airbag labels was performed using hot air welding technology; • Realizes real-time monitoring of melt quality during the material melting process • Using CFD modeling to study the effects of outlet distance, hot air velocity, and hot air temperature on the melting rate. [ABSTRACT FROM AUTHOR]

Flow control is essential in high-pressure CO 2 systems. Flow regulators are widely used for flow adjustment in piping systems. In this paper, a novel combinational flow regulator is proposed, which contains four parallel branch channels, and each channel is arranged with a solenoid valve and an orifice plate. In order to analyze the internal flow characteristics of high-pressure CO 2 and flow adjustment performance of the proposed flow regulator, a numerical model of the regulator is established, and the validation of numerical model is verified by experimental results. Then, the pressure and velocity characteristics are studied numerically. Finally, the flow adjustment performance is investigated numerically and experimentally from three aspects: variation of flow rate with differential pressure, variation of the product of flow coefficient and throttling area, and dynamic variations of pressure, temperature and flow rate of the flow regulator. This paper serves as a valuable reference for researchers utilizing flow regulators to adjust the flow rate of CO 2 or other fluids. • Numerical model of a novel flow regulator is established, verified by experiments. • Pressure and velocity characteristics are discussed, CO 2 as working medium. • Variation of flow rate with differential pressure and flow area is analyzed. • Dynamic working situation of the regulator is investigated by experiments. [ABSTRACT FROM AUTHOR]

The energy sectors and chemicals depend heavily on shell & tube heat exchangers, which are also employed extensively in the modern manufacturing industry. Flow-induced noise has an important impact on how heat exchangers function. and should not be overlooked. Computational Fluid Dynamics (CFD) and acoustic-solid coupling are used in this paper to investigate the fluidic and vibration noise of tubes in shell & tube heat exchangers. In order to study the characteristic law of noise caused by flow, the flow and acoustic fields are combined in this research, with the flow field being estimated by accepting a large eddy simulation. A combination methodology of theoretical analysis and numerical simulation is utilized to analyze the influence of pipe type, pipe spacing, flow direction outside the pipe, flow velocity outside the pipe, and pipe length on noise. The results indicate that as the diameter of the pipe increases, the noise level rises, and with increasing pipe spacing, the noise decreases. The noise increases as the incidence angle of the fluid inflow increases. When flow rate accelerates, so does the noise. The study presented in this paper can serve as a theoretical and computational foundation for the design of shell & tube heat exchangers. [ABSTRACT FROM AUTHOR]

Numerical simulation, also known as computer simulation, uses an electronic computer to investigate and solve engineering problems, physical problems, and a wide range of other problems through numerical calculations and image visualization methods. Numerical simulation is often employed to support machine design, parameter selection, and size optimization, enabling the comparison of various schemes and processes. In recent years, numerical simulation has emerged as a powerful and promising tool for studying drum drying processes. Its applications include understanding complex gas–solid fluidization properties, exploring potential mechanisms of gas–solid flow, and optimizing drum drying design and scaling. This paper comprehensively reviews the numerical modeling of gas–solid flow, focusing on the numerical simulation of the flow characteristics in the drum drying process. Moreover, it identifies current challenges and outlines future development trends in the numerical simulation of this drying process, providing valuable insights for the optimization and application of this simulation technique in the broader field of drying technology. [ABSTRACT FROM AUTHOR]

This paper employs a computational fluid dynamics numerical framework integrating the Euler-Euler two-fluid model with the particle dynamics method to analyze the heat and mass transfer characteristics of water-based graphene nanofluid slurries in helical corrugated tubes. The results indicate that, with ice crystal content ranging from 10% to 30% at the inlet, the heat transfer performance is positively correlated with the slurry concentration, and the increase in nanofluid concentration has minimal impact on the pressure drop inside the tube. The helical structure results in the maximum flow velocity occurring in the groove area. Compared to straight tubes, the increase in heat transfer area does not only promote the generation of vortices but also enhances turbulent intensity, reduces the thickness of the thermal boundary layer, and improves heat transfer efficiency. Graphene nanofluid slurries exhibit superior heat transfer capability compared to pure water slurries, with surface heat transfer coefficient increasing with graphene concentration. The maximum HTC of helical corrugated tubes is 1.4 times that of straight tubes, with an average Nusselt number (Nu) 1.44 times higher than that of straight tubes. Lastly, an empirical correlation for Nu is established to predict the thermal performance of water-based graphene nanofluid slurries flowing through helical corrugated tubes. • Pressure drop, ice crystal concentration distribution, flow velocity, temperature distribution, and heat transfer performance are discussed. • Aqueous graphene nanofluid ice slurry demonstrates outstanding flow and heat transfer performance. • Helical structure significantly influences the flow and heat transfer of the ice slurry. • The average Nu of spiral bellows is 1.44 times that of straight pipe. [ABSTRACT FROM AUTHOR]

Liquid metals have excellent thermal properties such as low vapor pressure, high thermal conductivity, low dynamic viscosity, and a wide range of temperatures in which they maintain liquid state. Some scholars have investigated the application of liquid metal heat exchangers. However, there is still potential for further exploration of the applicable temperature range of a liquid metal heat exchanger. In this paper, a liquid lithium-air shell-and-tube heat exchanger with a liquid lithium inlet temperature of 1473 K was designed. The heat transfer performance characteristics were studied via numerical and experimental methods. Furthermore, the numerical results were compared with the theoretical calculation results. The maximum relative differences were determined to be acceptable for the outlet temperatures, the tube and total heat transfer coefficient. The experimental temperatures for different monitoring points were compared with the steady state simulation results of the basic case. The relative errors were in the range of 0.1 % to 7.5 % for most of the temperature monitoring points. The findings of this study could offer crucial insights into the design of thermal management systems for many areas, such as the aerospace, nuclear engineering and shipbuilding industries. [ABSTRACT FROM AUTHOR]

A novel double-wall-hole honeycomb seal (D-WHHCS) is proposed in this paper. D-WHHCS is designed based on a traditional honeycomb seal (HCS) by drilling double holes in the honeycomb sidewalls. The leakage characteristics of D-WHHCS are investigated via the computational fluid dynamics (CFD) method. The sealing performance of D-WHHCS under different seal clearances, wall hole positions, operating pressures and rotating speeds is studied. The sealing mechanism of D-WHHCS is revealed. The results show that D-WHHCS has better sealing performance than HCS under all the considered operating conditions, with a maximum leakage reduction of 3.95%. A fluid concentration effect when the axial cavity number (N) = 14 is observed in D-WHHCS, which causes a 9.16% improvement in the maximum turbulent kinetic energy compared with HCS at the outlet extension. A large vortex in the cavities of D-WHHCS with N = 14 is guided by the jets at the centerlines of the drilling hoes. The average turbulent dissipation in the cavities of D-WHHCS is a maximum increase of 95.30%, even though the vortexes in the cavities with N = 13 are weakened by the counteractive effect of two jets. The leakage reduction performance of D-WHHCS decreases with increasing clearance. An abnormal low-pressure region is produced in the first cavity because the intensive jet covers the first two cavities and suppresses the throttling effect of the first-stage honeycomb cavity. The leakage of D-WHHCS further decreases along with holes closing to rotor surface. • The leakage of double-wall-hole honeycomb seal (D-WHHCS) decreases 3.95%. • A fluid concentration effect is observed in the sealing gap of D-WHHCS. • A huge turbulent dissipation in unit cavities is observed in the D-WHHCS. • The sealing performance of D-WHHCS is weakened with seal gap increasing. • The smaller the distance between holes and rotor is, the larger the vortexes is. [ABSTRACT FROM AUTHOR]

In this paper, we present a comprehensive study on the heat transfer in the spiral coiled tubes, employing both numerical simulations and experimental analysis. The investigation includes an exploration of water flow at different mass flow rates, ranging from 0.025 to 0.11 kg / s , to capture a wide range of operating conditions. The numerical simulations were conducted using advanced computational fluid dynamics (CFD) techniques, providing detailed insights into the heat transfer behavior within the spiral tube. Concurrently, experimental tests were performed to validate the numerical results and compare them with existing findings from previous studies. The primary aim of our study is to establish correlations for calculating the Nusselt number and friction coefficient in the spiral coiled tubes. These correlations serve as essential tools for engineers and researchers in predicting heat transfer characteristics and pressure drop, thus facilitating the design and optimization of heat exchangers and heat recovery systems that incorporate spiral coiled tubes. Overall, the results obtained from this investigation enhance our understanding of heat transfer in spiral tubes and contribute to the development of reliable predictive models. The proposed correlations offer practical and efficient means of assessing heat transfer performance, making significant strides towards achieving more energy-efficient and sustainable industrial processes. • Fluid flow and heat transfer in a spiral coiled tube were studied. • Effects of mass flow rate of water on heat transfer in a spiral coiled tube were investigated. • Correlations for calculation of Nusselt number and friction coefficient for water flow in a spiral coiled tube were developed. [ABSTRACT FROM AUTHOR]

In this study, two radiators on which louvres had been made up on either outer surface or inner surface, were experimentally contrasted within an experimental setup which heats water between an average temperature difference range of ΔT = 30 K to 60 K. Constructive details and dimensions of experimental test section's orientations having 6 different positions were given in detail in the paper. Positions include the situation of the panel radiator without louvre, louvres on front surface-single slice, louvres on back surface-single slice, louvres on back surface-single slice, and louvers on back surface-single slice with a chimney, louvres on back surface- 3 slices in a row. Detailed uncertainty analyses were given in order to calculate the uncertainties of water inlet and outlet temperatures, and heat output values. CFD analyses have been carried out to have air velocity and temperature distribution around the sample panel radiators after the validation with experiments. CFD results were found to be in good agreement with experiments having tolerable deviation varied from 10.73% to 24%. Almost all experimental findings including measured data points were declared in a Table for other researchers' usage for their validation issues. 8 number of empirical correlations have been proposed in order to determine the heat outputs regarding with the different configurations of the test section. Finally, effect of louver space on the heat outputs was also shown in the paper. [ABSTRACT FROM AUTHOR]

This paper reports a study on the effect of orifice thickness-to-diameter ratio (τ / d) on the turbulent flow through an orifice plate. Details of the flow characteristics downstream of the orifice are investigated both experimentally and numerically for a Reynolds number of 25,000. For this purpose, seven orifice plates are manufactured with τ / d ranging between 0.27 and 1.37. Particle Image Velocimetry (PIV) is used to experimentally study the flow patterns downstream of the orifices, with particular focus on instantaneous and time-averaged velocity distributions, streamline patterns, turbulent kinetic energy, Reynolds shear stress, and out-of-plane vorticity. Results show that, with increasing τ / d , the location of the vena contracta moves closer to the orifice plate, and eventually inside for τ / d > 0.55. Increasing τ / d also results in decreasing turbulent kinetic energy and Reynolds shear stress. For the selected τ / d range, experimental and numerical results are in good agreement with the thick and thin orifice classification available in the literature. • Effect of orifice thickness-to-diameter ratio, τ/ d on flow structures is studied. • Quantitative visualization of details of the orifice flow characteristics of hydrodynamics is reported. • As orifice thickness-to-diameter ratioincreases, decreasing velocity gradients and turbulence intensity are observed. • The minimum pressure downstream of the orifice is increased with increasing τ/ d , reached a peak value at τ/ d = 0.55 [ABSTRACT FROM AUTHOR]

Several challenges exist in the analysis of the sodium-cooled fast reactor (SFR) core using computational fluid dynamics (CFD)codes. These include the intricate task of geometric modeling and mesh partitioning and the substantial computational resources required by CFD calculations. These challenges have been shown to create significant impediments to the practical analysis of the SFR core. This paper proposes a CFD scheme called the Parameterized Modeling and Automated Distributed Computing Approach (PM-ADC) to address the challenges. This approach includes a fuel assembly model tailored for the fast reactor core and incorporates parameterized geometric modeling coupled with a system to automate the distribution of parallel computing. The PM-ADC scheme is divided into two critical components: rapid preprocessing design and the generation of geometric models and meshes for core assemblies, enabled by Parameterized Modeling (PM). In contrast, the Automatic Distributed Computing (ADC) component is responsible for the enhancement of computing efficiency and resource utilization. This is achieved by the automatic allocation and distribution of CFD computing resources within a partitioned domain, resulting in the completion of CFD analyses for all fuel assemblies at full height in a significantly reduced timeframe. The performance of the PM-ADC scheme is analyzed on CFD calculations on representative areas of 81 fuel assemblies within the core of the Chinese Experimental Fast Reactor (CEFR). The results show that the PM-ADC scheme can accurately and efficiently simulate the flow and heat transfer characteristics of the CEFR fuel assembly, demonstrating its potential for high-fidelity analysis of large engineering systems. The study's findings also provide new insights and tools for the ongoing development and analysis of SFRs, contributing to the evolution of nuclear reactor design and safety. [ABSTRACT FROM AUTHOR]

Nowadays, a bio-inspired heat exchanger incorporating a triply periodic minimal surface (TPMS) structure has demonstrated great potential in the fields of new energy research and aerospace, which necessitates achieving a balance between low volume and high heat transfer efficiency while maintaining low pressure drop. In this paper, the adjustable heat efficiency of the heat exchanger with TPMS in gradient thicknesses is specially designed. A steady-state conjugate heat transfer (CHT) model is coupled with computational fluid dynamics (CFD) analysis. In addition, the temperature profile and velocity streamline are also checked to analyze the fluid flow behavior of the radiator. The results show that the convective heat transfer coefficient of the Gyroid with gradient level set values is 26.02–60.10% higher than that of the uniform Gyroid model, and the pressure drop is decreased by 9.66–18.05%. Both high heat transfer efficiency and low pressure drop can be achieved when the thickness is 0.2–0.3 mm and Re is 100–125. The heat exchangers with a TPMS thickness gradient in the ratio of 2:4:6 demonstrate a remarkable enhancement in overall heat transfer efficiency, achieving a 30.22% improvement compared to those with a TPMS thickness gradient in 6:4:2. [ABSTRACT FROM AUTHOR]

In this paper, the convective heat transfer and flow characteristics of nanofluids consisting of distilled water and 0.25, 0.5 wt% and 1 wt% Al 2 O 3 nanoparticles were studied experimentally and compared to predicted results using computational fluid dynamics (CFD) that using laminar model was performed to examine the heat transfer characteristics. The Al 2 O 3 nanoparicles with a nominal diameter of 40 nm are dispersed in distilled water to form stable suspensions containing various kind of volume concentrations of nanoparticles. For the even dispersion of the nanoparticles in the base liquid, ultrasound was applied for 3 h. The nanoparticle dispersion on alumina concentration was measured using UV spectroscopy. Thermal conductivities of nanofluid solutions are measured by the transient hot wire method. Heat transfer characteristics were investigated by changing pressure pulsation at each concentration. Finally, calculated heat transfer characteristics results using CFD are compared to experimental results and discussed successfully. Results indicate that the heat transfer coefficient and Nusselt number increase with increasing the Reynolds number and it is also seen that the Prandtl number is getting down when the concentration of nanofluids enlarge and showed the equation by the linear method of the result value. [ABSTRACT FROM AUTHOR]

2-D numerical models have been used to analyze flow distribution performance in consecutive bifurcating fluid flow distributors according to constructal theory. The quantitative analysis of flow distribution uniformity performance for Y shape distributors with different bifurcation angles as well as inlet velocities are evaluated with water as working fluid, a hypothesis on the mechanism for the maldistribution is also presented. It is found that the flow distribution uniformity deteriorates with the increase of bifurcation angles from 15° to 90°, and the worst performance occurs when bifurcation angle is 90°, where the largest pressure drop also appears. Furthermore, the flow distribution performance also decreases with increasing inlet velocity for the same distributor. Finally, an improvement to obtain more uniform flow uniformity for the T shape distributor is proposed by ‘shrinking’ the vertical channel width of each bifurcation. The conclusions obtained in this paper are potentially helpful for the design of fluid distributors for multi channel devices. [ABSTRACT FROM AUTHOR]

The SIMPLE algorithm for the pressure-velocity coupling has been adopted by many commercial and non-commercial CFD codes. The SIMPLE algorithm requires all normal velocities at the boundaries before solving the pressure correction equation. These velocities must imply an overall mass balance. In this paper, a new procedure to recalculate the outflow velocity for the Neumann type outflow boundary for forced convection with variable density is proposed. As an example of the utilization of this procedure, the outflow normal velocity of a circular duct was computed and the results were compared with the results using the new modified procedure. [ABSTRACT FROM AUTHOR]

This paper reports the effect of changing the aspect ratio on the heat transfer and flow quantities over in-line tube banks. Two types of in-line arrangements were employed; square and non-square configurations. The models that were examined are a standard k-ε model, SST k-ω model, v2-f model, EB k-ε model and EB-RSM model. The closer results to the experimental data and LES were obtained by the EB k-ε and v2-f models. For the square pitch ratios, the solution has faced a gradual change from a strong asymmetric to asymmetric and then to a perfect symmetry. The strong asymmetric solution was found by the very narrow aspect ratio of 1.2. However, the behaviour of cases of 1.5 and 1.6 became less strong than that predicted in the case of 1.2. In the larger aspect ratio of 1.75, the flow behaviour is seen to be absolutely symmetric for all variables under consideration except Nusselt number. For the very large pitch ratio of 5, the flow has recorded maximum distributions for all parameters on the windward side of the central tube with a perfect symmetric solution around the angle of 180° while the vortex shedding frequency has recorded minimum value and the Strouhal number; therefore, has given the smallest value. However, for the non-square pitch ratio of constant transverse distance, the solution is still asymmetric for all parameters with merely one stagnation at the angle of 52° at the case of the 1.5 × 1.75 while by increasing the longitudinal distance to 2 and 5, the solution provided a comprehensive symmetry for all variables with two vortices are fully developed mirrored in shape on the leeward side of the central tube. On the contrary, for the non-square pitch ratio of constant longitudinal distance, the flow of the case of 1.75 × 1.5 provided two stagnation locations at around 52° and 308° with a very similar solution to the case square ratio of 1.75 for all variables whereas by increasing the transverse distance to 2 and 5, the solution recorded was not perfectly symmetric resulting in two different vortices and one stagnation position located at the leading edge of the cylinder provided by the case of 5 × 1.5. In terms of vortex shedding effect, the reduction in the Strouhal number at a constant transverse pitch is less steep than those at a constant longitudinal pitch. [ABSTRACT FROM AUTHOR]

This paper proposes a method based on computational fluid dynamics to determine pressure drop and air distribution characteristics in recuperative exchangers. The numerical calculations were performed for a representative counter-flow heat exchanger with a relatively complex structure, providing a large heat exchange surface. To verify a proposed method, the empirical calculations based on known analytical solutions for straight channels with various shapes of cross-sections were also performed. Numerical and empirical calculations were compared with certified data obtained according to standards EN 308: 1997 standards. The verification showed that the numerical methods properly predict the pressure drop in operating parameters of the exchanger, within the uncertainty of experimental data. The empirical methods calculation accuracy strongly depends on the assumptions made before. • The precise air distribution analysis in counter-flow exchanger. • Numerical calculation of pressure drop. • Proposing a pressure drop calculation method compared to the empirical methods. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effect of ambient pressure on the thermal hydraulic behavior of stable steam jet during the process of direct contact condensation (DCC). Three-dimensional steady CFD simulation was conducted. A thermal equilibrium phase change model was inserted as a user defined function (UDF) to simulate the process of steam jet condensed into subcooled water. The shape of steam plume and axial temperature distribution were compared between experimental and numerical results, and good agreements were obtained. The steam plume shapes under different ambient pressures were obtained. The transformation of flow pattern from annular flow to bubble flow along axial direction was observed from the cross-sectional slices at different axial locations. Then the axial parameters such as velocity, temperature and static pressure under different ambient pressures were investigated. The existence of expansion and compression wave was verified due to the existence of the fluctuation of axial temperature. Besides, the average heat transfer coefficient ranges from 0.97 to 1.08 MW/m 2 K when ambient pressure ranges from 80 to 200 kPa. [ABSTRACT FROM AUTHOR]

The accuracy of centrifugal compressors performance and flow field prediction by Computational Fluid Dynamics (CFD) is a serious problem facing in the design and analysis process due to its complex flow feature inside. Different turbulence models choosing in the Reynolds-Averaged Navier-Stokes Equations (RANS) leads to different simulation results. In this paper, a high-pressure-ratio centrifugal compressor was used as the simulation object to discuss the effect of common turbulence models, including a one-equation model (Spalart-Allmaras model), a two-equation linear model (Shear Stress Transport model) and a two-equation nonlinear model (Explicit Algebraic RSM model), on performance prediction under design speed. By introducing the calculation method of local entropy generation rate, an improved method of dividing different types of loss in centrifugal compressors was proposed. After comparing with the experiment results, the effect of turbulence models on loss prediction inside the compressor was quantitative investigated. Further, the flow mechanism underlying was discussed. The results show that the secondary flow loss have the largest impact on the components' prediction performance, also, the reasons for different magnitudes of secondary flow loss inside the impeller and the diffuser are different. These comparisons hope to help designers choose an appropriate turbulence model in further compressor design process and may benefit future turbulence modelling development. • The predicted performance of SA, SST and EARSM models and the experimental results were compared. • An improved losses dividing method in centrifugal compressors was introduced. • Combining with the local entropy generation rate computation method, difference in predicted value of various types of loss under different turbulence models were quantitative analyzed. • The decisive role of secondary flow losses in performance prediction was revealed. • The different reasons for the different prediction of secondary flow loss in the impeller and diffuser were discussed linking to the flow mechanism respectively. [ABSTRACT FROM AUTHOR]

Plate heat exchangers (PHE s) have been acquired a considerable attention and have been popularly used for both single-phase and two-phase flows in the air-conditioning systems. During the study of the flow distribution of the PHE s , the two-phase flow distribution is analysed experimentally. However, since the observation of the internal flow field of the PHE is very difficult, Computational Fluid Dynamics (CFD) can be used to better predict the fluids flow field inside the plate heat exchanger. In this study, ANSYS FLUENT is used to model the flow field composed of the K050 chevron PHE to observe the two-phase flow and uneven flow distribution. Moreover, the effect of the distributor on the gas-liquid distribution in the multi-channels flow field is also evaluated. The major effort of this paper is to investigate the effect of the two-phase flow distribution in multi-channels PHE with and without an inflow distributor. For the multi-channels PHE without distributor, the simulation results show that the flow must operate at high Reynolds numbers to obtain better enhancement in the flow distribution. If the PHE operates under Reynolds number less than 1500, the vapor-liquid distribution is non-uniform. Furthermore, it is observed that when the inflow distributor is added, the two-phase flow distribution of the vapor phase improves significantly. However, the flow distribution of the liquid phase is better under low Reynolds numbers condition. In addition, it has been shown that as Reynolds number increases, the liquid flow distribution is not affected by the inflow distributor. [ABSTRACT FROM AUTHOR]

This paper aims to present detailed numerical solutions of natural convection flow of contaminated air and water along the vertical wavy frustum of a cone. This investigation is particularly conducted to characterize the flow behavior of spherical particles suspended in radiating Newtonian liquids. The governing equations are converted into dimensionless equations by using a set of suitable continuous transformations and solved through the implicit finite difference method. Comprehensive flow formations of the gas and particle phases are given with the aim to predict the enhancement of heat transport across the heated wavy frustum cone. It is recorded that the air–metal mixture can promote the rate of heat transfer drastically whereas water–metal mixture contributes a little in this regard. [ABSTRACT FROM AUTHOR]

In this paper, the hydrodynamics and wall-to-bed heat transfer of gas–solid flow in a conical fluidized bed were simulated using the Eulerian–Eulerian model. Sand with a diameter of 560 μm was used as bed material where its properties were calculated by applying the kinetic theory of granular flow (KTGF). Different amounts of slip between particle and wall were given by varying the specularity coefficient. The effect of different values of specularity coefficient (0, 0.2, 0.5, and 1.0) on hydrodynamic and wall-to-bed heat transfer at superficial gas velocity of 0.65 m/s was investigated. It was found that the wall-to-bed heat transfer coefficient decreases with increasing specularity coefficient. The specularity coefficient had no clear effect on the bed pressure drop. Different values of specularity coefficient resulted in almost the same hydrodynamic behavior near the wall and the center of bed. [ABSTRACT FROM AUTHOR]

In this paper, response surface methodology (RSM) based on central composite design (CCD) is applied to obtain an optimization design for the asymmetric blades geometry of a vertical axis wind turbine (VAWT). Turbine's airfoils are simulated by using computational fluid dynamics (CFD). The SST K-ω model is used to simulate turbulent flow around the asymmetric blade. The free-stream velocity is constant and the rotation speed of turbine rotor is considered 350 to 600 rpm. Results show that the maximum torque coefficient is obtained at rotation of 450 rpm. [ABSTRACT FROM AUTHOR]

With the rapid development of the Computational Fluid Dynamics (CFD), it is in a high demand and still remains unresolved to compute hypersonic heating accurately. In the past years, many researchers tried to solve this problem by studying the upwind scheme's choice. However, most of them just focused on the following two aspects: the scheme's level of robustness against the shock anomaly and the scheme's resolution in capturing discontinuity. Few people relate this problem to the scheme's level of accuracy at low speeds. In this paper, we conduct a systematic study on this issue. Results in our test cases show that a high level of accuracy at low speeds is beneficial to the hypersonic heating computations. Also, the AUSMPWM scheme performs well in hypersonic heating computations. [ABSTRACT FROM AUTHOR]

The lattice Boltzmann (LB) method, as a mesoscopic approach based on the kinetic theory, has been significantly developed and applied in a variety of fields in the recent decades. Among all the LB community members, the pseudopotential LB plays an increasingly important role in multiphase flow and phase change problems simulation. The thermal immiscible multiphase flow simulation using pseudopotential LB method is studied in this work. The results show that it is difficult to achieve multi-bubble/droplet coexistence due to the unphysical mass transfer phenomenon of “the big eat the small” – the small bubbles/droplets disappear and the big ones getting bigger before a physical coalescence when using an internal energy based temperature equation for single-component multiphase (SCMP) pseudopotential models. In addition, this unphysical effect can be effectively impeded by coupling an entropy-based temperature field, and the influence on density fields with different energy equations are discussed. The findings are identified and reported in this paper for the first time. This work gives a significant inspiration for solving the unphysical mass transfer problem, which determines whether the SCMP LB model can be used for multi-bubble/droplet systems. [ABSTRACT FROM AUTHOR]

This paper investigates the heat transfer rate of the combined cooling-and-heating heat exchanger by using computational fluid dynamics (CFD) method. Several factors, such as additional baffles and heat transfer areas, are also discussed in order to improve the efficiency of heat exchanger in the vacuum freeze-drying system. The simulated result indicated that, for addition electrical heating tube, the heat transfer rate of the heat exchanger increased with the increasing length of the electrical heating tube. The increasing rates of secondary and primary drying stages were 2.774 and 2.986 W/mm, respectively. For additional vertical baffle, the variation of the heat transfer rate with respect to vertical baffle length was in the U-shape format. The minimum heat transfer rates of secondary drying, primary drying and freezing stages were 716.79 W and − 195.17 W and − 670.71 W, respectively. For additional W-shape vertical baffles, the heat transfer rate of this heat exchanger was maximum among these four designs. For the three stages of heat exchangers with these four designs, the shell side Nusselt number had the inverse linear relationship with the Reynolds number. [ABSTRACT FROM AUTHOR]

This paper aims to numerically simulate transient thermal flow due to sudden starting drainage of liquid iron from the blast furnace hearth with a sitting dead-man (coke packed structure) by solving the three-dimensional Reynolds averaged Navier–Stokes equation coupled with the transport equation of energy. With the effect of conjugate heat transfer, a computational fluid dynamic (CFD) was performed to generate the dynamic flow field and temperature distribution as function of time, evaluating shear stress on the wall in the hearth and heat flux in the refractories, respectively, during unsteady tapping process from a free convection as the initial stage (t = 0) to the turbulent mixed thermal flow as the final stage (t → ∞). It was found that the shear stress on the wall near the tape-hole is significantly raised with increasing tapping time, which corresponds to decrease temperature of the refractory around the tap-hole with tapping time shapely, when the liquid iron begins to flow out from the blast hearth. The obtained results can be used to optimize operating condition for a long campaigning life of blast furnace. [ABSTRACT FROM AUTHOR]

In this paper, response surface methodology (RSM) based on central composite design (CCD) is applied to obtain an optimization design of finned type heat exchangers (HEX) to recover waste heat from the exhaust of a diesel engine. The design is performed for a single point operation (1600 rpm and 60 N m) of an OM314 diesel engine obtained from experimental measurements. Based on the CCD principle, fifteen HEX cases with different fins height, thickness and number are modeled numerically and the optimization is done to have the maximum heat recovery amount and minimum of pressure drop along the heat exchanger. [ABSTRACT FROM AUTHOR]

The impingement cooling is used to protect turbine components under high thermal load. This paper conducts a numerical study of heat transfer characteristics of turbine leading edge with lamilloy cooling structure. Target surface curvature and jet-to-surface spacing under various crossflow Reynolds number conditions are considered. Meanwhile, the target surface is dimpled to enhance heat transfer capability. Besides, staggered film holes are considered in the computational domain. The results show that the crossflow induces a counter rotating vortex pair that greatly increase the near wall turbulence and local heat transfer. The vortex pair forms the bound for a U-shaped high heat transfer region caused by the jet impingement. The target surface curvature tends to enlarge the relative area of the U-shaped region. The increased crossflow strength weakens the jet cooling effect, the total heat transfer performance is therefore decreased. Large jet-to-surface spacing enhances the impingement cooling when crossflow is weak but the total heat transfer will not recover as crossflow Reynolds number get higher compared with small and medium spacing cases. • Computational fluid dynamics (CFD) models used to simulate turbine leading edge internal heat transfer. • Impingement cooling configured with dimpled surface and film holes. • Compound influence of jet-to-surface spacing, surface curvature under crossflow. [ABSTRACT FROM AUTHOR]

The thermal-hydraulic performance of counter-current spiral plate heat exchanger (SPHE) under laminar flow regime is numerically investigated by adopting computational fluid dynamics (CFD) and field synergy principle in this paper. The effects of number of turns of spiral and Reynolds number on the average Nusselt number, heat transfer effectiveness, and Euler number are evaluated. The evidence shows that stronger convective heat transfer takes place at inner turns and areas around inner walls of channel. The heat transfer effectiveness increases with reducing increment and Euler number increases with increasing increment as the number of turns increases. When Reynolds number increases, both of heat transfer effectiveness and Euler number decrease due to large increments in mass flow rate. Consequently, an increase in number of turns of spiral at higher Reynolds numbers results in a greater benefit and a lower increment in cost. The numerical results in current research are also compared with the published article. It is found that the effect of thermal resistance of walls plays a vital role in evaluating the relation of heat transfer effectiveness and number of transfer units (NTU) at higher Biot numbers. • The thermal-hydraulic performance of SPHE for laminar flow is numerically studied. • Convective heat transfer occurs vigorously at locations with larger curvature. • An increase in number of turns of spiral at higher Reynolds numbers is suggested. • The ε-NTU relation is evaluated and compared with the published article. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the three-dimensional finite-volume-based simulation of the effects of pin through-hole (PTH) offset position in a wave soldering process. The PTH model was built and meshed by using GAMBIT software and tetrahedral/hybrid elements. In the wave soldering process, the advancement of molten solder was tracked by using Volume of Fluid technique. FLUENT software was employed to analyze the filling of molten solder (63Sn37Pb) and the capillary action between printed circuit board (PCB) and PTH connector. The effects of five offset positions (i.e., cases I to V) for a single PTH connector through PCB were investigated in the simulation study. The PTH offset position revealed significant influences on the filling time and profile. The increase of offset position resulted in a decrease of filling time and encouraged an uneven solder profile. Predicted solder profiles were substantiated by the experimental results, demonstrating the excellent capability of the current simulation model to handle the PTH filling problem. [Copyright &y& Elsevier]

Abstract: The separation and the reattachment of water flow through a sudden expansion in an annular passage have been considered in this paper. In the present work, numerical simulation is performed using the computational fluid dynamics package (FLUENT) to study the effect of step flow in an annular passage. In the study, the flowing fluid was considered heated uniformly from the beginning of the expansion, and the constant heat flux approach was also considered for the heat transfer investigation. The annular pipe flow system having step ratio of D/d =1.8 was considered, where d and D are representing the diameter of the pipe before and after expansion. The increase of flow reduces the surface temperature along the pipe to a minimum point, then gradually increases up to the maximum and hold for the rest of the pipe. The minimum surface temperature is obtained at flow reattachment point. The position of the minimum temperature point is dependent on the flow velocity over sudden expansion. In general, the local Nusselt number (Nu) increases with the increase of Reynolds number. [Copyright &y& Elsevier]

Abstract: In this paper, heat transfer of a multi-lobe particle (tri-lobe, tetra-lobe and penta-lobe) affected by wall in cross and axial-flow was investigated numerically and experimentally. In numerical analysis, finite element method (FEM) was used for solving partial equations using FEMLAB version 2.3. The experimental work was performed for checking the accuracy of numerical results and computing the mass transfer coefficient. The heat and mass transfer analogy was applied for gaining the Nusselt number for each particle in axial and cross flow. The results showed that the cross flow heat transfer rate is more than axial flow. In addition, the size of particle for tri-lobe and tetra-lobe particles in axial flow and the effect of rotation-angle of tri-lobe particle on heat transfer in cross flow were investigated. The results showed that increasing the rotation angle can cause the Nusselt number to decrease. The influence of cylinder to particle diameter ratio (N) on heat transfer of particles in cross flow and axial flow was studied; the results depicted that when N is greater than 5 wall effects can be ignored. Moreover, Mirhashemi et al. correlation has been modified according to gaining CFD results for horizontal multi-lobe particles. [Copyright &y& Elsevier]

Abstract: Shell and tube heat exchanger with single twisted tube bundle in five different twist angles, are studied using computational fluid dynamics (CFD) and compared to the conventional shell and tube heat exchanger with single segmental baffles. Effect of shell-side nozzles configurations on heat exchanger performance is studied as well. Heat transfer rate and pressure drop are the main issues investigated in the paper. The results show that, for the same shell-side flow rate, the heat transfer coefficient of heat exchanger with twisted tube bundle is lower than that of the heat exchanger with segmental baffles while shell-side pressure drop of the former is even much lower than that of the latter. The comparison of heat transfer rate per unit pressure drop versus shell-side mass flow rate shows that heat exchanger with twisted tube bundle in both cases of perpendicular and tangential shell-side nozzles, has significant performance advantages over the segmental baffled heat exchanger. Optimum bundle twist angles for such exchangers are found to be 65 and 55° for all shell side flow rates. [Copyright &y& Elsevier]

Abstract: In this paper, convective heat transfer effect on the non-Newtonian nanofluid flow in the horizontal tube with constant heat flux was investigated using computational fluid dynamics (CFD). For this purpose, non-Newtonian nanofluid containing Al2O3 and Xanthan aqueous solution as a liquid single phase with two average particle sizes of 45 and 150nm and four particle concentrations of 1, 2, 4 and 6wt.% and two concentrations of Xanthan aqueous solutions (0.6,1.0wt.%) were used. Effect of particle size and concentration of Xanthan solution on convective heat transfer coefficient was investigated in different Reynolds numbers (500< Re <2500) for various axial locations of tube. The results showed that heat transfer coefficient and Nu number of non-Newtonian nanofluid increased with increasing concentration of Xanthan solution. By applying the modeling results, an equation was obtained for Nusselt number prediction using the dimensionless numbers. The results showed that the correlated data were in very good agreement with predicted data. The maximum error was around 5%. [Copyright &y& Elsevier]

Abstract: In this paper an analytical model was developed to minimize the thermal resistance of an air cooled porous matrix made up of solid spheres with internal heat generation. This was done under the assumption of local thermal equilibrium. The analytical solution of the optimum sphere diameter was found to be independent of the heat generation rate of the solid spheres, but was dependent on the applied pressure drop and fluid properties. The analytical model compared very well to a numerical model found in a computational fluid dynamics code when air and liquid water properties were used for the fluid phase and wood and silica/sand properties were used for the solid phase. [Copyright &y& Elsevier]

Abstract: This paper reports experimental and Computational Fluid Dynamics (CFD) studies on combustion and radiation heat transfer from a real radiant tube heater. The temperature along the radiant tube as well as at different positions in a test room has been measured. A good agreement between the experimental and predicted results has been found. Based on this validation, the effect of excess air, presented by Air Factor (AF) on efficiency of heater has been studied, theoretically. Moreover, the effect of inlet air preheating on heater efficiency has been examined. The results show that the higher values of excess air can reduce the heater efficiency. The air preheating temperature caused positive effect on heater efficiency. In addition, the results show at higher preheating temperature the effect of AF value on heater efficiency is negligible. [Copyright &y& Elsevier]

Abstract: A computational work is performed in this paper to analyze the heat transfer, temperature distribution and flow field in a channel with a cavity heated from different sides. Flow inlets to the channel are uniform. Constant magnetic field is applied to the channel as Ha=10, Prandtl number is chosen as Pr=0.7 and Reynolds number is fixed at Re=100. Finite element method is used to solve governing equations. Three different cases were considered based on heater position in the cavity at the left vertical side (Case 1), bottom side (Case 2) and right vertical side (Case 3). It is found that the highest heat transfer is obtained when the isothermal heater is located at the right vertical wall. [Copyright &y& Elsevier]

Abstract: In this paper, heat transfer of single cylindrical particle affected by wall has been investigated numerically and experimentally for Reynolds number range 2000 to 6000. The heat transfer in two different orientations, axial and cross flow over the particle has been considered in simulation with MultiPhysics Software FEMLAB version 2.3. The heat and mass transfer analogy technique has been applied for validation of the simulation results. The coated particle with naphthalene was sublimated to obtain the corresponding Sherwood numbers. The results show that the CFD model can predict the particle-to-fluid heat transfer for two situations due to trivial error (an average error of 6%) compared to experimental values. Influence of wall on heat transfer of particle in seven different bed-to-cylinder diameter ratio (N=1.66, 2.65, 2.75, 5, 6.66, 12, and 18) have been discussed in different velocities. According to obtaining results, with increasing the bed-to-cylinder diameter ratio over the 12 wall have no significant consequence on Nusselt number. Due to this fact, a CFD based correlation has been proposed to consider the wall effects on particle-to-fluid Nusselt number with an average error of 2.19%. [Copyright &y& Elsevier]

Abstract: This paper presents the Direct Numerical Simulation of interphase mass transfer in gas liquid multiphase system. The volume-of-fluid (VOF) method in conjunction with mass transfer model has been used. In order to study the process of interphase mass transfer two numerical simulation methods are presented. Two common mass transfer mechanisms, Diffusion through Stagnant Film (DTSF) and Equi-Molal Counter Diffusion (EMCD), are investigated. Two benchmarks, the Stefan diffusion problem and the diffusion in water and methanol Gas–Liquid system, have been used to validate the numerical methods. Afterwards two proposed numerical solution for different mass transfer mechanisms have been investigated in stratified gas liquid flows between two parallel plates. The results show by different approaches in numerical solution, the accuracy of mass transfer simulation is different. [Copyright &y& Elsevier]

Abstract: This paper reports the experimental and Computational Fluid Dynamics (CFD) modeling studies on heat transfer, friction factor and thermal performance of an air cooled heat exchanger equipped with three types of tube insert including butterfly, classic and jagged twisted tape. In the studied range of Reynolds number the maximum thermal performance factor was obtained by the butterfly insert with an inclined angle of 90°. The results have also revealed that the difference between the heat transfer rates obtained from employing the classic and jagged inserts reduces by decreasing the twist ratio. The CFD predicted results were used to explain the observed results in terms of turbulence intensity. In addition, good agreements between the predicted and measured Nu number as well as friction factor values were obtained. [Copyright &y& Elsevier]

Abstract: This paper presents a thermal analysis and experimental validation of natural convective air cooling of a high brightness 3×3 LED array package on a printed circuit board (PCB) during operation from 0 to 180° inclinations. Temperature distribution and heat flow of the LED package are assessed by thermal profile measurement using an IR camera and thermocouples. In addition, a design study on the thermal performance of the packaging structure is also performed. The analysis results reveal that the effect of position and inclination plays an important role in the heat dissipation of the LED package. The heat transfer process of the LED PCB package in natural convection is also modelled and simulated using computational fluid dynamics (CFD) method. The proposed thermal analytical study provides a detailed understanding of the thermal response of an open or enclosed LED array PCB unit under various operating conditions. The results provide criteria for setting up a LED array system and for adopting design features that would be beneficial to effective thermal management. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a CFD simulation of gasoline evaporation during the splash loading of gasoline tank. The volume of fluid based (VOF) interface tracking method in conjunction with a mass transfer model was used. Evaporation rate was determined by a source term at the interface. The effect of different parameters such as loading velocity, temperature and initial vapor mass fraction on gasoline lost was determined. The results show that by increasing the loading velocity, the total evaporated mass decreases. Based on CFD simulations a correlation has been proposed to evaluate the amount of gasoline losses during the fuel tank splash loading. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the finite volume method (FVM) based numerical simulation is used for the flow visualization of capillary driven underfill process for different solder bump arrangements of flip chip packages is presented. Three different 3D flip chip package models are developed and simulated using computational fluid dynamic (CFD) code, FLUENT 6.3. Capillary action and cross viscosity model are taken into account in the simulation. One-line dispensing method is applied in the analysis and the volume of fluid (VOF) technique is used to track the flow front. The effect of solder balls arrangement on flow behavior and filling time is studied and the solder balls arrangement is found to affect the flow behavior and filling time. The flow patterns of simulation are observed for three flip chip packages and compared. The ability of the proposed model and FLUENT in handling flip chip underfill problems is proved to be excellent. [Copyright &y& Elsevier]

Abstract: This paper reports the effect of jet position on the acid dispersion in a neutralization process. Experiments were carried out in a continuous stirred reactor and the effect of jet nozzle position on non-reactive dye dispersion at seven layouts was studied. Consequently, the neutralization reaction mixing was carried out at the best and worst positions. The results reveal that the ways that flow pushes the acid inside the tank are quite different and the neutralization performance can significantly be affected by the jet position. The Computational Fluid Dynamics (CFD) modeling was carried out in order to analyze the experimental observations. [Copyright &y& Elsevier]

Abstract: In this study computational fluid dynamics (CFD) model has been developed to predict gas dynamic behavior in a High Velocity Oxygen-Fuel (HVOF) thermal spray gun in which premixed oxygen and propane are burnt in a combustion chamber linked to a parallel-sided nozzle. The CFD analysis is applied to investigate axisymmetric, steady-state, turbulent, compressible, chemically reacting, subsonic and supersonic flow inside and outside the gun. The gas velocity, temperature, pressure and Mach number distributions are presented for various locations inside and outside the gun. The calculated results show that the most sensitive parameters affecting the process are fuel-to-oxygen gas ratio and total gas flow rate. Gas dynamic behavior along the centerline of the gun depends on both total gas flow rate and fuel-to-oxygen gas ratio. The numerical simulations show that the axial gas velocity and Mach number distribution depend on both flow rate and ratio; the highest velocity is achieved at the higher flow rate and most fuel-rich ratio. In addition, the results reported in this paper illustrate that the numerical simulation can be one of the most powerful and beneficial tools for the HVOF system design, optimization and performance analysis. [Copyright &y& Elsevier]

Abstract: This paper investigates numerically the effect of embedding a porous medium on the deposition rate in a two-dimensional (2-D) axi-symmetric vertical rotating metalorganic chemical vapor deposition (MOCVD) reactor. The 2-D Navier–Stokes, thermal-energy, and mass transfer equations as well as the wall surface reaction for growth rate in this model are solved by using commercial computational fluid dynamics (CFD) package, FLUENT (version 6.2), with a segregated method. As shown in the results, the recirculation cell caused by a buoyancy effect above the susceptor may be eliminated due to a large pressure drop during CVD process. Under a condition of the appropriate porosity and the appropriate distance between a porous medium and the susceptor, the film uniformity may be increased about 53.3% owing to a thin boundary layer near the susceptor. In addition, the case of a porous medium embedded in a modified MOCVD reactor is considered in this study to increase the film uniformity further. The numerical results show that the uniformity of the film may be enhanced about 77.9%. [Copyright &y& Elsevier]

Abstract: This paper numerically predicts the decrease in temperature of the eroded hearth of the blast furnace with floating deadman (coke zone) case for Port Kembla no. 5 blast furnace (PKBF5) by solving the Navier–Stokes equation, the thermal-energy-balance equation with conjugated heat transfer, and the mass transfer equation with the effect of chemical reaction during tapping process at steady state. The chemical reaction is generated by titanium dioxide (TiO2) reacting with saturated carbon in hot metal. The following calculations are done by using a commercial computational fluid dynamics (CFD) package, FLUENT (version 6.2), with a segregated model. As shown in the results, on the basis of the flow pattern of liquid iron, the inlet selection of adding TiO2 may be far away from the taphole. The calculated temperature variation in the damaged hearth by reaction is significant, but that on the other side of the hearth without adding TiO2 isn''t influenced. Additionally, the numerical temperature data of different locations may be examined by the blast furnace operators to judge the effect of lowering temperature. [Copyright &y& Elsevier]

Metal-Organic Chemical Vapor Deposition (MOCVD) is an important method of epitaxial growth used to obtain high-quality film and mass production. Computational Fluid Dynamics (CFD) method is widely used to simulate and study the growth process of MOCVD, but the complex process parameters and high computational cost have limited the real-time application. A hybrid Response Surface Methodology–K-Nearest Neighbor (RSM-KNN) model is developed to reach the goal of the high speed of flow field prediction and process parameters optimization. In this paper, a 3-dimensional ZnO-MOCVD model is built and then validated using the experimental and simulation results. The Design of Experiment (DOE) method is used to improve data collection performance. Results of deposition rate and uniformity are combined with the RSM model to analyze the influence of process parameters and to explore the relationship between deposition rate, uniformity and flow state. The results of the flow field are combined with the machine learning method KNN to study and predict the flow field and flow states in the reactor. The hybrid model is also presented and optimized to realize the growth of high deposition rate, and the uniformity is increased by 30% at a steady flow state of plug flow. [ABSTRACT FROM AUTHOR]

Flexible membranes are involved in various biological and engineering systems, and the mass transfer across semipermeable membranes often plays important roles in such systems. To simulate the mass transfer process across flexible semipermeable membranes, considerable technical difficulties exist due to the particular relationship between the trans-membrane mass flux and concentration jump across membrane. In this paper, we propose an immersed membrane method to address these challenges. Following the key conception and treatment in the classical immersed boundary method for flow-structure interaction, we replace the sharp membrane interface with an immersed layer of fluid along the membrane. The immersed membrane layer has no influence on the membrane deformation and fluid flow; however, it adds extra mass transfer resistance according to the original membrane permeability. With this replacement, the mass transfer process can be solved with a uniform numerical scheme over the same Eulerian mesh, and the complicated interface treatment for the interface condition across membrane can be avoided. The method is then validated by comparing numerical results to theoretical solutions for steady and unsteady systems with flat and curved membranes and excellent agreement is observed. Several demonstration simulations are also performed to illustrate that the membrane effect on mass transfer has been correctly represented in our method and that our method could be useful for simulating mass transfer with deformable membranes. [ABSTRACT FROM AUTHOR]