Numerical Simulation Of Heat Transfer Research Articles

Numerical simulation of heat transfer during spark plasma sintering of porous SiC

The strong covalent bonding of SiC makes it difficult to be fully sintered using conventional sintering techniques. Therefore, electrical current-assisted sintering techniques such as spark plasma sintering are needed to sinter SiC. The finite numerical simulations have been generally used to predict and guide sintering processes of ceramics (i.e.TiC,AlO3). In this work, the numerical simulations of the temperature distribution, electrical field and thermal field on the porous SiC cylindrical samples by Comsol were investigated in details. The influence of porosity on the temperature distribution and electrical field distribution of the SiC samples were analyzed. Both the maximum current density (1.19 × 107A/m2) and the maximum temperature (2030 °C) of the SPS device occurred at the punch/spacer interface. The temperature values at the centre of the samples were proportional to the porosity, and the temperatures at the center of the samples increased from ∼1960 °C to ∼2010 °C at t = 2000s, with the porosity increasing from 1% to 60%. The uniformity of the temperature distribution deteriorated as the porosity increases, and the temperature gradients between the center and edge of the samples with the porosity of 1% and 60%, were ∼80 °C and ∼130 °C at t = 2000s, respectively.

Flow Reversal of Unsteady Oscillatory Flow in Combined Convection Fully Developed Vertical Channel

Numerical simulations of flow and heat transfer in an unsteady oscillatory fully developed combined convection are conducted. The temperature on the right wall varies with sinusoidal rhythm over time within a locked mean temperature, whereas the temperature on the left wall remains constant. Both walls are also considered to be stationary. A numerical solution for the momentum and energy equations obtained using the Runga- Kutta method is used to analyze the effect of periodic oscillation on the velocity and temperature configurations, as well as the progression of heat generations. The combined convection process of heat transfer and its flow pattern in a vertical channel is important in many applications, including environmental, industrial, and engineering. This study is prompted by a problem with the heat transfer process, which is difficult, expensive, and time-consuming. The purpose of this study is to develop a mathematical model, find a numerical solution, and conduct parametric studies on the double-diffusive fully developed vertical channel with unsteady oscillatory flow, as well as to investigate the effect of various parameters on the velocity and temperature profiles. The effect of different dimensional parameters is tested and the flow reversal phenomenon is discussed. The dimensional equations are transformed into non-dimensional equations using the similarity technique. Then, the built-in program dsolve in Maple is used to numerically solve the boundary value problem (BVP). A validation study is conducted on a previously reported problem to confirm the validity of the present calculation. The flow and temperature numerical findings are represented visually. It is found that a large development of flow is caused by the plate temperature oscillation with high amplitude, therefore, the nature of the flow differs from the non-oscillating case.

Numerical simulation of heat transfer and entropy generation due to the nanofluid natural convection with viscous dissipation in an inclined square cavity

In this work, the effects of viscous dissipation on heat transfer and entropy generation of the nanofluid natural convection in an inclined square cavity are numerically investigated. A fractional-step semiimplicit finite difference algorithm based on the projection method on a staggered grid is proposed to solve the laminar natural convection problem, which has the advantage of larger time steps. The square cavity is filled with a nanofluid composed of (Cu) copper nanoparticles and water. and the viscous dissipative behavior of the mixture flow is not negligible. The studied parameters are Rayleigh number Ra ( 10 4 and 10 5 ), Eckert number Ec ( 0 − 2 ), the volume fraction of solid particles ϕ ( 0 − 0.06 ), and inclination angle of square cavity α ( 0 − π / 2 ). The Prandtl number is fixed to Pr = 6.2 . The results show that at any inclination angle, the increase in viscous dissipation leads to weakened heat transfer on the hot wall, enhanced heat transfer on the cold wall, and weakened flow in the square cavity. For the base solution without nanoparticles, the Eckert number has the greatest impact, with its effects on the average Nusselt number on the hot wall, maximum streamfunction, and average Nusselt number on the cold wall being ∼13, 0.15, 18.69%, and at Ra = 10 4 , and 12, 0.5, 28.87% at Ra = 10 5 , respectively. Research on entropy generation shows that as Eckert number increases, the entropy generation due to heat transfer increases, while due to fluid friction decreases. As the Rayleigh number increases, the effect of viscous dissipation increases. As the inclination angle increases, the effects of volume fraction and Eckert number weaken. Adding solid particles can effectively weaken the effect of viscous dissipation.

Effects of structure parameters on performances of laser powder bed fusion processed AlSi10Mg body-centered cubic lattices

The study aims to explore the impact of structural parameters on the formability, mechanical properties, and heat conductivity of body centered cubic (BCC) lattice structures produced through laser powder bed fusion (LPBF). The BCC lattice structures with varied cell diameters and cell sizes were fabricated using LPBF. Surface morphologies, compression properties, and numerical simulation of heat transfer were carried out. Results indicated that the relative density of the BCC structure was influenced by the diameter and size of the cell. An increase in the diameter or a decrease in the size of the cell led to an increase in the relative density of the BCC lattice structure. However, the surface forming quality decreased. On the other hand, the compressive strength of the structure increased, and the heat transfer property was also enhanced. The BCC lattice structure achieved its highest relative density and obtained a peak compressive strength of 320.66 MPa when the cell rod diameter was 1.5 mm and the cell size was 3 mm.

Influence of the Shrinkage of the Inner Layer of Steel Tubes on Permissible Thermal Load

This paper presents the results of numerical simulations of heat transfer in a tube with a protective chromium layer on the inner surface made of steel, with different shrinkage temperatures. Shrinkage in the steel is an unfavorable phenomenon because it causes cracks in the chrome coating. The cracks contribute to the peeling of the protective material on the inner surface of the tube. Wear and damage to the chrome layer significantly shortens the tube’s service life. The influence of the type of steel with medium carbon content on heat transfer for a sequence of ten, thirty, and sixty heat impulses was examined. Simulations were carried out for two selected steels with clearly different shrinkage temperatures, i.e., 30HN2MFA and X37CrMoV5-1 (1.2343). In 30HN2MFA steel, the shrinkage effect occurred at a temperature of approx. 750 °C, while in X37CrMoV5-1 steel it occurred at a temperature of approx. 870 °C. In the computational model, 30 cross-sections of the three-meter-long tube were analyzed. A time-dependent heat transfer coefficient was calculated in each zone. Heat transfer simulations were carried out using COMSOL version 6.1 software. This paper shows that for X37CrMoV5-1 steel, the shrinkage temperature on the inner surface of the tube was reached after approx. 60 heat impulses, while for 30HN2MFA steel, it was reached after approx. 30. The greatest differences in the number of impulses occurred for a pipe with a 200 µm thick chrome layer.

A comprehensive fluid–solid coupling dynamic simulation for spatiotemporal distribution of regression rate in hybrid rocket motors

The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor (HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination (R2) of 0.9765 and 0.9298, respectively. This research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.

Numerical simulation of hybrid nanofluid flow and heat transfer across parallel surfaces with suction/injection and magnetic effect

The heat and mass transfer through the hybrid nanofluid (Hnf) flow with the significance of magnetic field across two spinning parallel plates has been described. The Hnf is prepared by the dispersion of SiO2 (Silicon dioxide) and MoS2 (Molybdenum Disulfide) nanoparticles (NPs) in the ethylene glycol (EG). The MoS2 is anti-friction compound used in automobiles and other types of heavy machineries in industry. It reduces the engine noise, reduces fuel consumption and enhances engine life. Similarly, SiO2 is used in structural materials, food processing, pharmaceutical industries and as an electrical insulator in microelectronic apparatus. Based on the remarkable applications of the hybrid nanofluid (MoS2-SiO2/EG), the flow has been modeled in form of PDEs, which are numerically handled through the parametric method (PCM). The results are compared for velocity, energy and concentration profiles with another numerical technique bvp4c (Matlab code). It has been detected that the results derived from the PCM are reliable and accurate. Furthermore, the velocity field declines with the upshot of Reynold number and suction/injection factor. The heat dissemination rate enhances from 2.85% to 9.89%, whereas the mass diffusion rate enriches form 2.32% to 9.56% as the values of nanoparticles varies from 0.01 to 0.03.

Numerical simulation of heat transfer during meat ball cooking and microbial food safety enhancement.

This study was conducted to apply the finite volume method (FVM) to solve the partial differential equation (PDE) governing the heat transfer process during meat cooking with convective surface conditions. For a one-dimensional, round-shaped food, such as meat balls, the domain may be divided into shells of equal thickness, with energy balance established for each adjacent shell using in the finite difference scheme (FDS) to construct a set of finite difference equations, which were then solved simultaneously using the FORTRAN language and the IVPAG subroutine of the International Mathematics and Statistics Library. The FDS is flexible for temperature-dependent physical properties of foods, such as thermal conductivity (k), specific heat (Cp ), thermal diffusivity (α), and boundary conditions, for example, surface heat transfer coefficient (h), to predict the dynamic temperature profiles in beef and chicken meat balls cooked in an oven. Once the FVM model was established and validated, it was used to simulate the dynamic temperature profiles during cooking, which were then used in combination with the general method to evaluate the thermal lethality of Shiga toxin-producing Escherichia coli and Salmonella spp. using D and z values in ground meats during cooking. The method can be applied to design cooking processes that effectively inactivate foodborne pathogens while maintaining the quality of cooked meats and evaluate the adequacy of a cooking process. PRACTICAL APPLICATION: The temperature dependences of thermal conductivity (k) and thermal diffusivity (α) of raw ground beef and ground chicken meats were measured. These thermal properties were then used in numerical simulation to predict the dynamic heating temperature profile and thermal lethality of ground beef and chicken meat balls. The numerical simulation method may be used to optimize and evaluate thermal processes and ensure the inactivation of pathogens in meat products during cooking.

Physically Realistic Inlet-Velocity Profiles in Duct Flows

A uniform inlet velocity profile is widely used in the numerical simulations of fluid flow and heat transfer in ducts for both incompressible and compressible flows. In incompressible flows, the calculated fluid pressure at the inlet edge is extremely high and affects the calculation of the average pressure. In compressible flows, the fluctuation of pressure in the flow direction results in the fluctuation in the velocity. This has motivated this study to numerically investigate a physically realistic velocity profile at the inlet of a pipe rather than using a uniform velocity profile. The numerical simulations were based on the control volume-based power law scheme and the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The continuity and momentum equations for a flow in a pipe with the rounded inlet corner were solved to obtain a physically realistic inlet velocity profile. The obtained inlet velocity profile was expressed by a simple expression in the range of Reynolds number from 100 to 2000. Using this velocity profile, both the incompressible and compressible flows in a pipe were numerically investigated. The results resolved the previously observed inconsistencies in the pressure that were previously observed in the numerical simulations with uniform inlet velocity profiles.

Supercritical CO2 flow and heat transfer through tapered horizontal mini-tubes: Parametric analysis and optimization study

One effective method for enhancing heat transfer in tubular heat exchangers involves gradually altering the cross-section of their tubes. While extensive research has been carried out in typical operating conditions, a significant shortage of studies exists that specifically investigate how changes in tube cross-section affect the heat transfer of fluids under critical and pseudocritical conditions. Additionally, the absence of a comprehensive parametric study considering the effect of all operating conditions and geometric parameters, and providing an optimal model in this field, is keenly felt. This paper offers a finite volume-based numerical simulation of steady-state turbulent flow and heat transfer for supercritical CO2 inside circular horizontal mini-tubes with tapered lateral profiles. It is found that the impact of buoyancy on thermal and hydraulic characteristics is more noticeable in the diverging mini-tube than in the converging mini-tube. The results of the parametric study reveal that under the same geometric parameters, the heat transfer coefficient in the diverging mini-tube is higher than that in the converging mini-tube by 5.2–28.6 %, with a simultaneous reduction in pressure drop ranging from 52.1 % to 68.5 %. However, in the case of a high diameter or diameter ratio, the heat transfer coefficient of the converging mini-tube exceeds that of the diverging mini-tube. Subsequently, an optimization study is conducted using BBD-RSM. To achieve the maximum heat transfer coefficient and the minimum pressure drop, an additional 54 cases are investigated, covering diverse ranges of operating conditions and geometric parameters. The results indicate that the mass flow rate and tube diameter are the most influential parameters on thermal and hydraulic characteristics. Additionally, the impact of the diameter ratio on the pressure drop is more pronounced than on the heat transfer coefficient. This research can serve as a foundation for enhancing the design of heat exchange devices within innovative supercritical CO2 power generation cycles.

Numerical heat transfer to LBE flow in a wire-wrapped 19-rod bundle using an OpenFOAM-based solver: fourParameterFoam

The LBE-cooled fast reactor (LFR) has received significant attention due to its diverse applications. However, numerical heat transfer simulations encounter challenges with lead-bismuth eutectic (LBE) due to its low Prandtl number and high molecular thermal diffusion, often resulting in an overestimation of heat transfer using the simple gradient diffusion hypothesis (SGDH). This study aims to improve the prediction accuracy of heat transfer to LBE in numerical models by developing a solver, named fourParameterFoam, based on the turbulent model SST k-ω and algebraic heat flux model (AHFM) kθ-ɛθ within the OpenFOAM framework. The performance of SGDH models and AHFMs is compared based on heat transfer experiments in vertical tube flow with LBE. The behavior of the turbulent Prandtl number (Prt) under various flow conditions is concluded based on the SST k-ω-kθ-ɛθ model. Additionally, the applicability of the SST k-ω-kθ-ɛθ model in complex flow is validated through heat transfer experiments in a wire-wrapped 19-rod bundle with LBE flow. Local temperature variations on the heated rod surface and sub-channels are analyzed to elucidate the thermal development process in the bundle. The impact of wire spacers on flow behavior is summarized using visualization techniques, and the suitability of corresponding empirical Nusselt number correlations in LBE flow is evaluated.

Numerical simulation of heat transfer and pressure drop characteristics in twisted oval tubes

The numerical research aims to investigate the heat transfer performance difference between the twisted tube and the smooth tube at the same hydraulic diameter. The effect of the major/minor axis ratios on the fluid-flow inside the twisted oval tube is studied in the Reynolds number range of 3000-11000, and the integral thermal-hydraulic effectiveness of twisted oval tubes is evaluated. The results show that the twisted wall induces secondary flow perpendicular to the mainstream direction. The vortices are rapidly generated in the pipe-line when the fluid enters the twisted tube section from the upstream section. As the fluid develops further, the vortices converge to form a spiral flow. Numerical simulations indicate that the average Nusselt number of twisted oval tube with a major/minor axes ratio of 1.70 increases by 18.7-35.5%, while the pressure drop increases by

Numerical simulation of flow and heat transfer of n-decane in composite tube under supercritical pressure

As scramjet propulsion systems face big challenges in thermal protection performance, regenerative cooling techniques have been proposed to improve heat transfer behavior. This study introduced a novel design of composite cooling channel with bends and conducted computational fluid dynamics (CFD) simulations to analyze the flow characteristics, heat transfer behavior, and pyrolysis of hydrocarbon fuel within the tube. Results show that the presence of bends significantly enhances heat transfer, leading to an increased temperature and conversion. The composite tube with 15 bends demonstrated a 19.9% increase in conversion rate compared to the straight tube. Hence, proper structure design can improve the regenerative cooling performance which may promote the development of scramjet propulsion systems.

Numerical simulation on the influence of metal radiation shield on the thermal insulation performance of the semi-transparent materials

Foams, flexible felt and thermal barrier coatings are widely used in the thermal insulation fields. This type of material has lower density and thermal conductivity, as well as higher specific surface area and porosity, and is generally referred to as the semi-transparent materials. The radiation heat transfer inside the semi-transparent materials belongs to medium radiation, so the radiation thermal conductivity is larger at high temperature. However, the metal radiation shields (MRSs) play an important role in weakening radiation heat transfer. In order to study the effect of MRSs on the thermal insulation performance of the semi-transparent materials, the numerical simulation of coupling heat transfer of heat conduction and heat radiation is carried out. The effective thermal conductivity (ETC) of the semi-transparent materials with different extinction coefficient is calculated when the different layers of MRSs are evenly inserted into the semi-transparent materials at the specific temperature, so that the influence of MRSs on the thermal insulation performance of the semi-transparent materials can be obtained. The simulation results show that whether it is an optical thin medium or an optical thick medium, when 7 layers of MRSs are inserted into the semi-transparent materials, the thermal insulation performance is greatly improved. After that, the ETC changes little with the increase of the layer of MRSs.

Numerical simulation of convective heat transfer in the discharging process of external ice-melting ice storage systems

The external ice-melting ice storage system was widely used because of its advantages of reducing peak power consumption, reducing energy consumption and emissions, and fast ice melting speed. However, designing the external ice-melting ice storage system proved to be a challenge, and the structure and flow of the water distribution system needed to be fully considered. In particular, the problem of unstable outlet water temperature limited the practical application of the external melting ice storage system. Aiming at the problem of unstable outlet water temperature, a three-dimensional CFD phase change model was constructed in this paper. By comparing with the experimental data, the impact of varying water flow rates on the thermal and cooling properties of the was investigated. The results indicated that when the water flow rate was 226 ml/min for the system with an ice thickness of 74 mm, the outlet temperature of the ice storage tank was consistently below 5°C, the Nusselt number of ice and water remained constant, and the convective heat transfer effect was improved. The numerical simulation results provided guidance for the design and practical application of the water distribution system of the external melting ice storage system.

Numerical simulation of gas-solid heat transfer and moisture evaporation process in preheating shaft kiln for ferromagnesium pellets

The arc furnace is an important equipment in the production of manganese ferroalloys. In the smelting process, it produces high temperature flue gas above 700 K, which has high utilization value. During the pelleting process, moisture exists on the surface and inside of the pellets, which, if directly fed into the arc furnace, will lower the temperature of the furnace, affecting the production, and will also cause the pellets to burst, resulting in pressure fluctuations in the furnace and other hazards. The preheating shaft kiln reduces the moisture content of the pellet while preheating the pellet by utilizing high temperature flue gas. In this paper, through the establishment of porous media and shrinking core coupling mathematical model, to achieve the prediction of the heating and drying process of the pellets of various particle sizes, which is in good agreement with the production monitoring data. The results show that 9~11 mm pellets have the best preheating effect in terms of tail gas temperature, pellet temperature and preheating time.

Numerical simulations of fluid flows and heat transfer in melt pools of Directed Energy Deposition of SS316L

This paper presents the numerical model developed to simulate fluid flow and heat transfer in melt pools formed in Directed Energy Deposition of stainless steel SS316L. The model incorporated important heat and momentum source terms. The energy source terms included laser energy, latent heat of phase change, convective heat loss, radiative heat loss, evaporative heat loss, and energy addition due to molten particle deposition into the melt pool. The momentum source terms were due to surface tension effect, thermocapillary (Marangoni) effect, thermal buoyancy, momentum damping due to phase change, molten particle momentum, and recoil effect due to evaporation. The simulations suggested that the predicted flow and heat transfer in the melt pool affected the resulting shape and size. With the process parameters currently employed, the melt pool was elongated, wide and shallow, with depressed free surface and outward convective flow. The outward flow was caused by the dominant region of high temperature in the centre of the melt pool, such that the temperature gradient of surface tension is negative.

Numerical Simulation of Heat Transfer through Uniform Multilayer Walls using ANSYS

The paper presents a study on modelling the main heat transfer parameters through opaque building elements. The need for models to assess the thermal behavior of a building has increased greatly in recent years, primarily to allow a more accurate determination of the energy consumption of buildings to evaluate the performance of heating systems. In recent times, mathematical models and software have been implemented to obtain simulations that are very close to the real functioning of the main components of buildings. The present article consists in modeling a multi-layer homogeneous wall, which separates the interior space of an enclosure (rooms) from the outside environment. The article aims to carry out a series of simulations on the structure of a non-homogeneous multilayer wall using the ANSYS program. The simulations have been performed highlight how the values vary (both numerically and graphically) for a series of characteristic parameters such as heat fluxes, temperatures, convection coefficients. The values of the parameters obtained with the ANSYS program were also compared with those obtained by classical numerical calculations.

Numerical simulation of natural convection heat transfer in a cavity with finned surface under linear temperature profile

This paper is dedicated to a numerical study of natural convection through a cavity with finned surface where its base temperature is variable with linear profile. An approach based on modelling of internal fluid flow around a finned surface in laminar and at steady state conditions is used. Thermal and hydrodynamic aspects of the fluid flow were analyzed through the numerical resolution of equations of fluid dynamics. For this purpose, we have developed a computer code (in Fortran 90) based on the finite volume method. The studied model consists of a rectangular cavity where vertical walls are thermally insulated, the horizontal ones are maintained at different temperatures: cold and constant temperature on the upper wall and hot temperature with linear profile on the lower wall. The Rayleigh number used is in the range of 103 to 106 and the Prandtl number is fixed at 0.71. The plotted results are related to temperature distribution, streamlines, velocity fields as well as the mean Nusselt number.

Thermal resistance capacity model for the cold release characteristics of cemented paste backfill with phase change materials

A new method based on thermal resistance and capacity (RC) network model for fast predicting cold release characteristics of the cemented paste backfill with phase change materials is developed. The simplified heat transfer calculation model was established, and temperature variation was calculated by MATLAB. The RC model and program were validated by experimental results and numerical heat transfer simulations. Based on the verified RC model, the influence law of the initial ice-water ratio and slurry concentration were analyzed. With the increase of initial ice-water ratio and the decrease of slurry concentration, the cooling ability was enhanced and the cold release process was extended. Furthermore, the cemented paste backfill with ice and paraffin were compared. The cooling release effect of slurry containing ice grains was better than that of slurry containing paraffin throughout the melting process. Compared with the numerical heat transfer simulation method, RC model can effectively improve the calculation efficiency under the premise of satisfying the accuracy. This study is of great significance in providing a timely forecast of the cold release characteristics of the cemented paste backfill with phase change materials in engineering design and practice.