Numerical Simulation Of Heat Transfer Research Articles

Analytical and numerical calculation and simulation of heat transfer in a composite wall made of polyethylene terephthalate bottle

The dynamics of heat transfer in composite walls made of Polyethylene Terephthalate (PET) bottles is studied using the energy conservation model. Ten walls of different structures were studied, including two control walls made of compressed earth brick (CEB) and cementitious material, cement-sand brick (CSB) and eight composite walls made of PET bottles filled with thermal insulation and/or mechanical stabilisation materials. The model equation is solved analytically using the separation of variables method and numerically using the finite difference method, and they are confirmed using CASTEM finite element software. As boundary conditions, a constant temperature (Text) is applied at one end of the wall, and the constant temperature (T0) is applied at any other point at the initial time. The effect of PET bottles filling on the thermal behaviour of the wall was then carried out to determine the optimum design that would give the wall better thermal inertia. The results obtained with CASTEM is fairly in agreement with the results obtained analytically and numerically, with a maximum relative error closed to that of the spatial evolution and 3.310−2 for the temporal one. It is found that heterogeneous filling of PET bottles provides better thermal inertia at the wall.

Addendum: Numerical simulation of heat transfer in particulate flows using a thermal immersed boundary lattice Boltzmann method

Addendum: Numerical simulation of heat transfer in particulate flows using a thermal immersed boundary lattice Boltzmann method

Adaptability analysis of flow and heat transfer multi-scale numerical method for printed circuit heat exchanger

The printed circuit heat exchanger (PCHE) is a high-efficiency and compact mini-channel heat exchanger. Due to the large number of fine channels, it is difficult to conduct the flow and heat transfer numerical simulation of the entire heat exchanger based on the actual channels, which requires a lot of computational resource and time. In this paper, a simplified multi-scale numerical method with a non-equilibrium porous media model (NOPM) is proposed to study the flow and heat transfer performance of PCHE at high temperature and pressure. The pressure field, velocity field and temperature field of NOPM and actual multi-channel model (MC) under different working conditions are compared to study the adaptability of NOPM for the PCHE. The results indicate that the NOPM can accurately predict the flow and heat transfer performance under PCHE configurations with a large number of channels. However, as the channel number decreases, the relative errors in the temperature and pressure prediction significantly increase due to the increased flow maldistribution. Similarly, the NOPM can well predict the overall temperature distribution of the PCHE solid when the channel number is numerous. This work could support accurate thermal design, and provide accurate temperature field for the thermal stress analysis of PCHE.

Numerical simulation of granular heat transfer within lifter rotating drum using smoothed particle hydrodynamics (SPH)

Abstract The rotating drums are typical industrial thermal processing equipment, which is widely used to heat or cool material particles in the circle fluid bed (CFB) systems. The traditional cylindrical rotating drum cannot significantly promote the heat transfer process of granules in operation, largely limiting further application. In this research, using smoothed particle hydrodynamics (SPH), two different types of lifters are employed to investigate the effects of shape, size, and number of lifters on the coefficient of heat transfer within the rotating drums by combining the flow and mixing characteristics of particles, the stress distribution, the transient velocity and temperature distribution, and the trend of the Peclet number.

Evolution Mechanism of Blast Furnace Cooling Plate Slag‐Hanging Behavior with Different Cooling System Structure

Based on the 3D heat transfer numerical simulation model, the evolution mechanism of blast furnace cooling plate slag‐hanging behavior with different cooling system structures is analyzed. Cooling plate reduced by 20 mm will not affect its slag‐hanging behavior. Copper cooling plate is best suited for high heat load areas. The vertical spacing of cooling plate is extended by 200 mm, the uniformity of the slag layer decreases by 5%, and the temperature of cooling plate and refractory material increases by 11 and 50 °C. Cooling plate vertical spacing of 510 mm or less can ensure stable slag hanging in the blast furnace. When using a single refractory material, the average uniformity of the slag layer is 95%, 86%, and 79% for graphite brick, semigraphite brick, and sialon‐SiC brick, respectively. Si3N4‐SiC brick cannot operate properly in high heat load areas. The factory can consider setting 125 mm sialon‐SiC brick in the furnace; graphite brick is used outside the furnace lining. The slag layer is well distributed, and the average value of uniformity is about 90%. Even if the slag layer is fully dislodged, the hot surface temperature of the furnace lining is 785 °C, and it can be quickly reslag hanging.

Micro segment analysis and machine learning prediction for thermal-hydraulic parameters of propane condensation flow in a PCHE straight channel

In the LNG regasification process, the printed circuit heat exchangers(PCHE) is an ideal choice for vaporizer, with propane as the intermediate working medium in the hot side of PCHE. In this work, numerical simulations of propane condensation flow and heat transfer at different operating parameters was carried out in a semi-circular straight channel of PCHE. The micro-segment analysis method was used to present the local heat transfer coefficient and pressure drop in the channel. The results indicate that the propane condensation process can be divided into three stages: the “constant temperature condensation stage” in the droplet condensation state, the “varying temperature condensation stage” in the film condensation state, and the “subcooled stage” in the liquid phase state. Different operating parameters can affect the start and end position of each stage, as well as the parameter values in the same state. An artificial neural network method was used to predict the local heat transfer coefficient and pressure drop, with the predicting error of less than 5 % and 10 % respectively. This study provides a machine learning method to accurately predict the flow and heat transfer parameters for propane condensation flow in PCHE channel and valuable for future design of LNG vaporizer.

Integrated neural network based simulation of thermo solutal radiative double-diffusive convection of ternary hybrid nanofluid flow in an inclined annulus with thermophoretic particle deposition

Numerical simulation of magnetohydrodynamic radiative double-diffusive convective heat and mass transfer of a ternary hybrid nanofluid with thermophoretic particle deposition in an inclined annulus is studied. Both sides of cylinders are preserved at uniform temperatures, while the remaining sides are thermally insulated. The coupled nonlinear partial differential equations are solved using a finite difference approach. The detailed computational results of heat and mass transfer rate, temperature, concentration and flow fields are presented and discussed for a distinct range of significant physical parameters. The results demonstrated that increasing the angle of the inclination factor increases fluid flow. In light of buoyancy, when the annular cavity is set downward, the enhanced shear velocity is transported upwards, where it reaches its optimal temperature. The higher temperature difference leads to augmented dynamic fluid motion, particularly in the radial direction, as the system seeks to balance the thermal energy through convective transfer. The Brownian motion parameter has abrupt mobility of nanoparticles in liquid, which promotes particle collisions with liquid molecules, yielding kinetic energy. Increased values of thermophoretic parameters augment the thermophoresis force. Thermophoretic particle deposition increases the concentration of nanoparticles in an annulus due to the migration of particles from hot to cold regions under the influence of temperature gradient. The heat and mass transfer characteristics of ternary hybrid nanofluid are forecasted through an artificial neural network-based Levenberg–Marquardt backpropagated algorithm. The built model shows the heat and mass transfer rate root mean squared values through the Levenberg–Marquardt algorithm as one and mean squared error values as 1e-07 and 1e-08 respectively.

Numerical simulation and multi-objective optimization design of conjugate heat transfer in novel double shell-passes multi-layer helically coiled tubes heat exchangers

A novel double shell-passes multi-layer helically coiled tubes heat exchanger (DSMHCTHE) is proposed to improve the flow and heat transfer performance of the shell side. It was studied by using conjugate heat transfer numerical model. By changing coil diameter and pitch, the influence of coil torsion on the performance of the heat exchangers was investigated in the range of 0.0637–0.3183, and compared with the conventional multi-layer helically coiled tubes heat exchangers (MHCTHE). Two kinds of heat exchangers were optimized by using multi-objective optimization differential evolution algorithm. The results indicate that the coil pitch has a greater effect on the overall heat transfer coefficient, and the effects of coil pitch variations in the inner and outer helically coiled tubes follow different patterns. Compared with MHCTHE, the heat transfer rate of DSMHCTHE are increased by 13.9 %–19.1 %, the comprehensive performance is increased by 13.0 %–18.0 %, and the heat transfer entropy generation number and friction entropy generation number are lower. It shows that DSMHCTHE have better application potential as heat exchangers.

Steady Heat Transfer Analysis of the Refrigerator Seal Considering Rigid and Flexible Contact

The rigid and flexible contact of the refrigerator seal has a significant impact on its heat transfer characteristics, but existing research has ignored this important factor. In this paper, the assembly physical model at the seal region is established by static structural analysis. Then a three-dimensional heat transfer numerical simulation is carried out. The assembly distance affects the contact state of the seal by changing the contact position between the seal and the door or the cabinet. The calculation results show that the calculated temperature at the seal region considering the actual assembly deformation is closer to the measured temperatures. In the case study, the heat leakage load decreases by 18.57% and 19.99% at the compressed state, while it increases by 4.45% under the stretching state. The proportion of heat transfer load in the path of rubber strip-cold air and rubber strip-outer shell of the cabinet is the largest, reaching over 30.0%. The heat transfer load of the cold bridge also accounts for over 20.0%. When optimizing the seal structure, reducing the contact interface length of rubber strip-cold air, reducing thermal conductivity, and increasing the contact thermal resistance of cold bridge should be focused on.

Physical and numerical simulation of heat and mass transfer in the furnace of a thermogravimetric analyzer

A numerical study of the processes of heat and mass transfer in the furnace of a thermogravimetric analyzer was carried out, aimed at improving the accuracy of determining the kinetic characteristics of samples during their thermal transformations in different media. Validation of the model and prognostic estimates were carried out in relation to specially conducted thermogravimetric studies of the conversion of fossil and renewable carbon-containing raw materials in successive processes of decarbonization (combustion) and carbonation (mineralization of ash residue). The application of the study results allows to calculate the actual concentrations of the reagent over the sample uncontrolled by the device during pulsed switching of media and the actual temperatures of the sample during its thermochemical transformations.

Experimental and numerical investigation on the effect of ease allowance of clothing on thermal comfort

The heat transfer within the microclimate of clothing directly affects the thermal sensation of the human body, holding significant implications for both heat dissipation and cold protection. To investigate the variations in the heat transfer performance of the microclimate under the clothing influenced by distinct air gap thicknesses and diverse body postures, twelve female subjects participated in experiments wearing T-shirts with various ease allowances, conducting tasks in both sitting and standing positions within a climate chamber set at 20 °C and 50 % RH. Physiological parameters and subjective evaluations of comfort were recorded. Additionally, we constructed a three-dimensional model of the air gap featuring realistic morphology for numerical simulations of microclimatic heat transfer in a standing posture. The experimental results indicate that air gap thickness significantly impacts core temperature, mean skin temperature, local skin temperature, and thermal sensation. While postural differences did not show statistical significance, temperatures and thermal sensations were generally higher in the sitting position. Based on the results of numerical simulation, under this environmental condition, approximately 27 % of heat transfer was through radiation, with both the percentage of radiative heat transfer and the overall heat flux increasing with greater ease allowance. Furthermore, airflow under the clothing became more disorganized at thicker air layers, primarily concentrating in folds, hems, and sides of the body. This study provides a theoretical support for the workwear design and similar clothing and helps to reduce energy consumption in office environments.

Optimization design and interface characteristics research of high damping NiTi - Nickel-Aluminum Bronze functional gradient composite coating additively manufactured by high-speed laser-directed energy deposition

The near-equatomic NiTi shape memory alloy demonstrates exceptional damping performance due to its distinctive low-temperature self-cooperative martensitic internal friction. This study successfully fabricated NiTi-NAB (Nickel-Aluminium bronze shape memory alloy) functionally graded composite coatings with excellent metallurgical bonding between layers on Q235 steel substrates by designing an appropriate interlayer structure and employing the high-speed laser-directed energy deposition (LDED). Through comprehensive evaluation of the composite coating's performance and the numerical simulations of heat transfer within the molten pool, we elucidated the impact of process parameter levels on the microstructure and phase transformation characteristics of the NiTi alloy coating (NTC). The phase composition and phase interface characteristics of the NTC surface and bonding interface were analyzed using an electron probe microanalyzer and transmission electron microscopy, while dynamic thermomechanical analysis was employed to evaluate the damping performance of the NTC. The results indicate that an optimal parameter combination area still exists within the NTC-LDED process parameter window, even with equal laser energy density. Insufficient parameter levels can lead to an increase of micro-defects within the NTC, consequently causing a deterioration in both the cohesion and deformation resistance of the coating. Excessively high parameter levels can lead to significant element loss and residual stress, which in turn contributes to an increase in microcracks within the coating. A considerable quantity of reaction product mixture phases was formed at the interface between NTC and NAB, tending to align coherently with the NAB phase interface. The NTC, prepared with optimal process parameters, exhibits exceptional damping performance with a damping ratio of 0.498 at internal friction equilibrium, rendering it highly promising for applications in surface erosion protection for fluid machinery.

A COMSOL-Based Numerical Simulation of Heat Transfer in a Hybrid Nanofluid Flow at the Stagnant Point across a Stretching/Shrinking Sheet: Implementation for Understanding and Improving Solar Systems

A COMSOL-Based Numerical Simulation of Heat Transfer in a Hybrid Nanofluid Flow at the Stagnant Point across a Stretching/Shrinking Sheet: Implementation for Understanding and Improving Solar Systems

Evaluation of the impact of combustion chamber geometries for biomass plancha-type cookstoves

Improved cookstoves are used to reduce carbon emissions into the atmosphere and the impact of deforestation, thus improving the quality of life of their users. The main objective of this work is to evaluate three combustion chamber geometries for biomass plancha-type cookstoves, in the range of 9.5–12.5 kW, which corresponds to real operating conditions. The first geometry corresponds to a traditional rocket elbow section that is widely used in this kind of device. The other two geometries are new modified designs. They make use of three and four chamfers above the rocket elbow. Additionally, for all the geometries, the effect of a baffle close to the exit of the chimney is evaluated. Numerical simulations for fluid flow, heat transfer, and gas-phase chemical reactions for the three-dimensional internal volume of the geometries are conducted using ANSYS Fluent 2019 R3. Results for the average temperature on the comal and total mass flow rate at the exit of the chimney are validated with experimental measurements and a theoretical model, respectively. The main findings are that the use of a baffle in all geometries increases the flow recirculation below the comal; as a result, the average temperature of the comal and hence the thermal efficiency reach higher values. Based upon numerical predictions, the cookstove with three chamfers and a baffle provided a more temperature homogeneous distribution on the comal.

Influence of solid cylinders on fluid flow and thermal analysis in a curved channel with constant magnetic field

The current study explores the numerical simulation of constant mixed convection heat transfer and fluid flow within a channel, driven by the inlet velocity. The investigation focuses on a curved irregular channel where the presence of three differently sized circular obstacles introduces an unpredictable element to the heat transfer process. For the two-dimensional physical scenario, mathematical equations are formulated to analyze velocity and temperature. Employing appropriate dimensional variables, the coupled partial differential equations are transformed into dimensionless form. Subsequently, the Finite Element Method (FEM) is employed to simulate the results for non-dimensional physical parameters such as Reynolds number, Richardson number, Hartmann number, nanoparticles' volume fraction, and various states of the circular obstacles on heated lines, flow structure, velocities, and temperatures at mean positions generating isotherms, streamlines, velocity, and temperature profiles for various parameter increments. The analysis reveals significant influences of Reynolds number (Re) and heated circular obstacles on the temperature profile, manifesting as heated lines within the system. The analysis brings to light the substantial impacts of nanoparticles on the temperature profile at both the vertical and horizontal mean positions. An elevated Hartmann number signifies a more robust magnetic field than viscous forces. A heightened magnetic field can hinder fluid movement and modify the patterns of heat transfer. Based on the graphical results, we infer that temperature differences tend to arise between strata as the Richardson number increases, leading to a heightened and more evident stratification.

Effect of porosity and pore heterogeneity on heat transfer performance of polyimide aerogels

The effects of porosity and pore distribution on the heat transfer performance of polyimide (PI) aerogel under natural convection were investigated through a combination of experimental and numerical simulations. The governing equations of heat transfer were analyzed in detail. A novel heterogeneity factor (η) was introduced to quantify internal pore distribution. PI aerogels exhibiting a range of porosities and heterogeneity factors were synthesized and characterized. The natural convection heat transfer coefficient of PI aerogels was measured experimentally, providing empirical data. A porous model was developed by integrating Voronoi technique with a two-scale generation method, allowing for comprehensive numerical simulations of heat transfer. The numerical results demonstrated strong concordance with the experimental data, validating the model’s accuracy. The results revealed that the heat transfer performance of the aerogels diminished markedly with increasing porosity when heterogeneity was held constant. Conversely, with fixed porosity, the heat transfer performance improved significantly with greater heterogeneity. Numerical simulations further enabled the visualization of internal temperature and flow fields, elucidating that the effect of porosity and heterogeneity on natural convection heat transfer performance is predominantly driven by variations in internal permeability.

Numerical simulation of heat and mass transfer through hybrid nanofluid flow consists of polymer/CNT matrix nanocomposites across parallel sheets

The hybrid nanofluid (Hnf) flow with heat and mass transmission under the magnetic field and activation energy consequences across parallel double-rotating surfaces has been studied. In order to synthesize the Hnf, polymer/CNT matrix nanocomposites (MNCs) are dissolved in water. Polymer/CNT MNCs are highly efficient and have exceptional properties. These MNCs are helpful in various applications, from engineering to biomedical research, because of their incredible thermophysical properties. Keeping in view the significant uses of the polymer/CNT MNC hybrid nanofluid flow, we have formulated the fluid flow in the form of the system of PDEs (partial differential equations), which are reformed into the non-dimensional form of ODEs (ordinary differential equations) and then solved numerically through the Matlab package (bvp4c). The numerical outputs for velocity, heat and mass profiles are compared with another numerical approach ND-solve. It has been determined that the outputs are precisely correct and reliable. Furthermore, the fluid velocity drops with the influence of suction/injection, Reynold number, and polymer/CNT MNC. The increasing quantity of polymer/CNT MNC in water reduces the energy and mass profiles. The energy field enhances with the upshot of the heat source term, whereas the concentration field falloffs with the effect of Schmidt number.

Numerical simulation of natural convection in a differentially heated cubical cavity with solid fins

PurposeThe performance of solid fins inside a differentially heated cubical cavity is numerically studied in this paper. The main purpose of the study is to make an optimization to reach the maximum heat transfer in the enclosure having the solid fins with studied parameters.Design/methodology/approachThe considered domain of interest is a differentially heated cube having heat-conducting solid fins placed on the heated wall while an opposite wall is a cooled one. Other walls are adiabatic. Governing equations describing natural convection in the fluid filled cube and heat conduction in solid fins have been written using non-dimensional variables such velocity and vorticity taking into account the Boussinesq approximation for the buoyancy force and ideal solid/fluid interfaces between solid fins and fluid. The formulated equations with appropriate initial and boundary conditions have been solved by the finite difference method of the second of accuracy. The developed in-house computational code has been validated using the mesh sensitivity analysis and numerical data of other authors. Analysis has been performed in a wide range of key parameters such as Rayleigh number (Ra = 104–106), non-dimensional fins length (l = 0.2–0.8), non-dimensional location of fins (d = 0.2–0.6) and number of fins (n = 1–3).FindingsFrom numerical methods point of view the used non-primitive variables allows to perform numerical simulation of convective heat transfer in three-dimensional (3D) regions with two advantages, namely, excluding difficulties that can be found using vector potential functions and reducing the computational time compared to primitive variables and SIMPLE-like algorithms. From a physical point of view, it has been shown that using solid fins can intensify the heat transfer performance compared to cavities without any fins. Fins located close to the bottom wall of the cavity have a better heat transfer rate than those placed close to the upper cavity surface. At high Rayleigh numbers, increasing the fins length beyond 0.6 leads to a reduction of the average Nusselt number, and one solid fin can be used to intensify the heat transfer.Originality/valueThe present numerical study is based on hybrid approach for numerical analysis of convective heat transfer using velocity and vorticity that has some mentioned advantages. Obtained results allow intensifying the heat transfer using solid fins in 3D chambers with appropriate location and length.

Numerical simulation of melt flow and heat transfer in casting filling process based on SPH

There is a great influence of the melt filling process on the quality of castings. Smoothed particle hydrodynamics (SPH) that materials are approximated by free particles rather than by fixed grids is applied to accurately predict fluid flows involving complex free surfaces. In this paper we present a mathematical model of melt flow and heat transfer by using SPH method. A novel approach is used in the governing equations to ensure stable numerical schemes and homogeneous particle distributions. The SPH heat equation takes into account the thermal release during phase transition and is more suitable for alloy solidification. The solid wall boundary conditions are slightly modified to satisfy the filling simulations. Several case studies are carried out to predict significant details about the filling order and flow structures in the mold cavity. The velocity and temperature distributions during different stages of melt filling are also given. The results show that this proposed model allows us to understand the predisposition of defects such as gas porosity and weld lines in the castings. These predictions can be used as inputs for improving process parameters, venting and cooling systems design.

Full-Process Numerical Simulation of Flow, Heat Transfer and Solidification for Hot Stamping Steel Manufactured via Thin Slab Continuous Casting Process

Full-Process Numerical Simulation of Flow, Heat Transfer and Solidification for Hot Stamping Steel Manufactured via Thin Slab Continuous Casting Process