Numerical Simulation of Temperature and Fluid Fields in Solidification Process of Ferritic Stainless Steel under Vibration Conditions

The street canyon phenomenon has a negative impact on air quality. Flow, temperature, and the concentration fields of pollutants affect street canyon. Many studies have focused on the concentration and flow fields; model experiments on the temperature field have been less examined. This experiment investigates the effect of model height and placement of flow and temperature fields. Temperature and flow fields are visualized using a smoke-wire method, one of the methods used to visualize a flow field. Visualization images were investigated in comparison to several other images. In turbulent flow conditions, temperature change of the street is verified when the turbulence parameter has changed. As a result of the experiment, data showing a high cooling effect was obtained. Furthermore, a trend was verified for cooling effects under turbulent flow conditions.

The present work centers around a numerical three-dimensional transient investigation of the effects of axial convection on flow and temperature fields inside an open-ended annulus. The transient behavior of the flow field through the formation of a three-dimensional flow field and its subsequent effect on the temperature distribution at different axial locations within the annulus were analyzed by both finite difference and finite element methods. The results show that the axial convection has a distinctly different influence on the temperature and velocity fields. It is found that in the midportion of the annulus a two-dimensional assumption with respect to the temperature distribution can lead to satisfactory results for Ra<10,000. However, such an assumption is improper with respect to the flow field. Furthermore, it is shown that generally the errors for a two-dimensional assumption in the midportion of the annulus are less at earlier times (t<50Δt) during the transient development of the flow and temperature fields.

During crystallization processes the control and effective distribution of heat transfer from the heat exchanger to the solution plays an important role. The turbulent flow field and the temperature variations in the solution determine the local supersaturation profiles and the spatial particle distribution. Thus they have a strong impact on the final product quality, production capacity and efficiency of the process. In this sense, a sensor able to determine in situ the local process variables to get better insight in the process behavior, would be required. The recently proposed Smart moving Process Environment Actuators and Sensors (Smart PEAS) is a promising initiative to achieve a more efficient process control. In this PEAS system a network of floating sensors is integrated using Ultra Wide Band (UWB) wireless technology to form a monitoring and control system. As a first phase in the development of the Smart PEAS, the research is focused on the accurate measurements of the flow field and local temperature distribution in a reactor. The hydrodynamics of the Smart PEAS are very important to achieve the necessary accurate process information. In order to determine the hydrodynamic characteristics of the Smart PEAS and to validate and compare the obtained results, laternative non intrusive techniques are used to investigate them in this work. Microencapsulated liquid crystals are used as a measurement technique to study the local temperature and flow field in a heat exchanger crystallizer geometry. To measure the 3D flow and temperature fields the microencapsulated liquid crystals are recorded in a sheet of light plane inside the crystallizer by two digital color cameras in a stereoscopic position. The images of the liquid crystals are correlated to obtain the three velocity components (3C), while from the colors of the microencapsulated liquid crystals the local temperature can be deduced after appropriate calibration. Parallel experiments are done to investigate the three dimensional trajectories of different sensor geometries in the equipment by direct visualization of the sensors. Computational fluid dynamics simulations are performed to calculate the flow field, temperature distribution and sensor trajectories. The results are compared with the experimental results for validation. The validation of the computational simulation results with the experiments gave the necessary confidence to predict flow fields in new crystallizer designs. On the basis of the analysis the Smart PEAS sensor design and the reliability of the measurements obtained can be compared and implemented.

A pair of air-coupled ultrasonic capacitance transducers with polished metal backplates have been used to image temperature and flow fields in gases using ultrasonic tomography. Using a filtered back-projection algorithm and a difference technique, cross-sectional images of spatially variant changes in ultrasonic attenuation and slowness caused by the presence of temperature and flow fields were reconstructed. Temperature fields were produced in air by a commercial soldering iron, and the subsequent images of slowness variations used to reconstruct the air temperature at various heights above the iron. When compared to measurements made with a thermocouple, the tomographically reconstructed temperatures were found to be accurate to within 5%. The technique was also able to resolve multiple heat sources within the scan area. Attenuation and velocity images were likewise produced for flow fields created by an air-jet from a 1-mm-diam nozzle, at both 90 and 45 degrees to the scanning plane. The fact that temperature and flow fields can be measured in a gas without the need to insert any measuring devices into the image region is an advantage that may have many useful applications.

Analysis of adaptive-network-based fuzzy inference system (ANFIS) to estimate buoyancy-induced flow field in partially heated triangular enclosures

An experimental facility of advanced packaging electroplating cell is developed to study the uniformity of the temperature and flow field in the high precision electroplating cell. Based on heat transfer and computational fluid dynamics, a 2D numerical model is founded to analyze the temperature field and flow field of the experimental electroplating cell enclosure. Combing with test and simulated results, the effects of the heat source intensity, ventilated mode and heat transfer coefficient on the thermal field of the cell are discussed. Under the condition of natural convection with temperature gradient driving, although heat/cold source intensity and ventilated mode both have effects on the temperature field and flow field of the electroplating enclosure, the heat/cold source is the more marked factor influencing the uniformity of temperature field and flow field. The experimental and simulated results can give a way to enhance the uniformity of the temperature field and flow field and to improve the quantity of the WL-CSP electroplating.

The rapid reconstruction of the internal flow field within pressure vessel equipment based on features from limited detection points was of significant value for online monitoring and the construction of a digital twin. This paper proposed a surrogate model that combined Proper Orthogonal Decomposition (POD) with deep learning to capture the dynamic mapping relationship between sensor monitoring point information and the global flow field state during equipment operation, enabling rapid reconstruction of the temperature field and velocity field. Using POD, the order of the tested temperature field was reduced by 99.75%, and the order of the velocity field was reduced by 99.13%, effectively decreasing the dimensionality of the flow field. Our analysis revealed that the first modal coefficient of the temperature field snapshot data, after modal decomposition, had a higher energy proportion compared to that of the velocity field snapshot data, along with a more pronounced marginal effect. This indicates that more modes need to be retained for the velocity field to achieve a higher total energy proportion. By constructing a CSSA-BP model to represent the mapping relationship between the modal coefficients of the temperature and velocity fields and the data collected from the detection points, a comparison was made with the BP method in reconstructing the temperature field of a shell-and-tube heat exchanger. The CSSA-BP method yielded a maximum mean squared error (MSE) of 9.84 for the reconstructed temperature field, with a maximum mean absolute error (MAE) of 1.85. For the velocity field, the maximum MSE was 0.0135 and the maximum MAE was 0.0728. The global maximum errors for the reconstructed temperature field were 4.85%, 3.65%, and 4.29%, respectively. The global maximum errors for the reconstructed velocity field were 17.72%, 11.30%, and 16.79%, indicating that the model established in this study has high accuracy. Conventional CFD simulation methods require several hours, whereas the reconstruction model proposed here can rapidly reconstruct the flow field within 1 min after training is completed, significantly reducing reconstruction time. This work provides a new method for quickly obtaining the internal flow field state of pressure vessel equipment under limited detection points, offering a reference for online monitoring and the development of digital twins for pressure vessel equipment.

Based on finite element method(FEM), with general simulation software ANSYS FLOTRAN-CFD module as the platform, using three-dimensional SOLA-VOF method, set the velocity, pressure and temperature boundary conditions and initial conditions reasonably, simulate temperature field, flow field and free surface of Mold Filling process. To simulate the flow of molten metal more factually, mesh dividing method that suited the Liquid simulation was studied, and important thermophysical properties of viscosity and density used the form of function change with temperature. The least square method was used to fit viscosity and density function and these functions were given to boundary conditions. Analyzed the relationship between temperature field and flow field according to simulation result, and get the conclusion that the node temperature depends on filled state of elements attached. At the same time, Get the temperature field at the end of mold filling process, which provides accurate initial temperature field for temperature field and thermal stress field simulation of solidification process. Also provide valuable reference for numerical simulation of Mold Filling process and solidification process of similar part.

The present work relates to the simultaneous determination of concentration and temperature fields from a refractive index field, and is motivated by applications in evaporation. Several optical measurement techniques such as schlieren and interferometry can measure the refractive index field, which can then be converted to a density and temperature field for a single component system. The refractive index, however, is dependent on both temperature and concentration for a multi-component system involving combined heat and mass transfer. Hence, either the temperature or concentration field must be known to obtain the other. To circumvent this issue, several methods are evaluated in this study to extract concentration and temperature fields from a refractive index field. The evaluation is performed based on data from a coupled numerical solution of Navier–Stokes, energy and species conservation equations. The refractive index field can be obtained from this computed temperature and concentration field. This refractive index field is then separately used to obtain the combined temperature-concentration field using the method proposed in this work. This method is based on the premise that there is a relationship between temperature and concentration fields which can help to independently calculate both when the refractive index field is known. The temperature and concentration fields obtained using this approach are then compared with the originally computed field and the errors in them are estimated for a wide range of Lewis numbers. From the study, it is concluded that the proposed methods can be used to accurately determine the temperature and concentration fields from a given refractive index field.

3D grinding temperature field can be simulated by the finite difference method. When the finite difference method is used to calculate the temperature field, the boundary conditions need to be considered. Unfortunately, the difference equations for internal nodes and boundary nodes are not the same. For cuboid computing domains, there are twenty-six types of boundary nodes. This reduces the calculation efficiency to a certain extent. An improved finite difference method for the 3D grinding temperature field was proposed to solve this problem in this paper. By adding auxiliary nodes, the boundary nodes are converted into internal nodes, and the difference equations of the boundary nodes and internal nodes are unified. In this paper, the improved algorithm was used to simulate the 3D grinding temperature field. The temperature distribution characteristics of the grinding temperature field were analyzed. Then, the effects of heat source type, space step size, and convective heat transfer coefficient on the temperature field were studied. The results show that the improved algorithm can well simulate the 3D grinding temperature field. Finally, compared with the original algorithm, the calculation results were completely consistent, and the efficiency is improved by about 20%.

Differential sensitivity analysis and multi-variant simulation of formation pressure and temperature in heterogeneous media

Heat transfer and internal fluidity a droplet located in between parallel hydrophobic surfaces with varying spacing

Temperature and velocity fields in high-temperature lead coolant flows in a circular clearance for controlled oxygen impurity content in a flow were experimentally studied at the Nizhny Novgorod State Technical University by R.E. Alekseev (NNSTU). Temperature and velocity fields were simultaneously studied in “cold” and “hot” parts of the circuit in the following operating conditions: the lead temperature is t = 400–550 °C, the thermodynamic activity of oxygen is a = 10−5–100; the Peclet number is Pe = 500–7000, the coolant flow velocity is w = 0.1–1.5 m/s, and the average heat flux is q = 50–160 kW/m2. It has been found that the oxygen impurity content and characteristics of protective oxide coatings affect temperature and velocity fields in round and circular channels. This is due to the fact that oxygen in a coolant and oxide coatings on the surfaces limiting a liquid metal flow influence characteristics of the wall boundary region. The heat transfer process that occurs when HLMC transversely flows around heat exchange pipes is investigated now at the NNSTU. The experimental facility is a combination of two high-temperature liquid-metal stands, i.e., FT-2 with the lead coolant and FT-1 with the lead-bismuth coolant combined with an experimental section. The temperature of a heat-exchange surface is measured by thermocouples of diameter 1 mm mounted in walls of heat-exchange pipes. Velocity and temperature fields in a high-temperature HLMC flow are measured by special sensors placed in the flow cross section between rows of heat-exchange pipes. Heat transfer characteristics and temperature and velocity fields in a high-temperature lead coolant flow are studied in the following operating conditions: the lead temperature is t = 450–500 °C, the thermodynamic activity of oxygen is a = 10−5–100, and the coolant flow rate through the experimental setup is Q = 3–6 m3/h, which corresponds to coolant flow velocities of V = 0.4–0.8 m/s. Integrated experimental studies of characteristics of the heat transfer that occurs when the lead coolant transversely or obliquely flows around pipes have been carried out for the first time and the dependences Nu = f(Pe) for controlled content of thermodynamically active oxygen impurity and sediments of impurities have been obtained. It is assumed that the obtained experimental data on distribution of velocity and temperature fields in a HLMC flow will permit to study heat transfer processes and to use them for developing program codes for engineering calculations of heat exchange surfaces (steam generators) with a HLMC flow around them.

Purpose – The purpose of this paper is to explore the relationship of fluid flow and heat transfer inside the generator, a large hydro-generator is taken for an example and the temperature field in the generator is calculated according to computation of fluid field by using of corresponding mathematics methods based on fluid mechanical theory and heat transfer theory. Design/methodology/approach – To calculate the temperature field of the generator more accurately, a large-scale hydro-generator is taken as an example and the mathematical model and physical model of 3D stator temperature field and fluid field are established. And the calculation results of the fluid field are applied into the physics field of generator, coupled relationship between fluid field and temperature field was calculated by using of finite volume method and finite element method, respectively. The temperature fields based on fluid fields and the effect of different fluid flow state on generator temperature were analyzed and compared. Findings – The calculated results shows show good agreement with the measured results, meanwhile the effect of different fluid field state on the temperature field is analyzed and the relationship between temperature fields and fluid fields is achieved, which will provide a theoretical basis for ventilation structure design and calculation of synthesis physical fields. Originality/value – The relationship between temperature fields and fluid fields is obtained, providing a theoretical basis for ventilation structure design and calculation of synthesis physical fields.

Large-eddy simulation (LES) is applied to the problem of plume dispersion in the spatially-developing convective boundary layer (CBL) capped by a temperature inversion. In order to generate inflow turbulence with buoyant forcing, we first, simulate the neutral boundary layer flow (NBL) in the driver region using Lund’s method. At the same time, the temperature profile possessing the inversion part is imposed at the entrance of the driver region and the temperature field is calculated as a passive scalar. Next, the buoyancy effect is introduced into the flow field in the main region. We evaluate the applicability of the LES model for atmospheric dispersion in the CBL flow and compare the characteristics of plume dispersion in the CBL flow with those in the neutral boundary layer. The Richardson number based on the temperature increment across the inversion obtained by the present LES model is 22.4 and the capping effect of the temperature inversion can be captured qualitatively in the upper portion of the CBL. Characteristics of flow and temperature fields in the main portion of CBL flow are similar to those of previous experiments [1],[2] and observations [3] . Concerning dispersion behavior, we also find that mean concentrations decrease immediately above the inversion height and the peak values of r.m.s concentrations are located near the inversion height at larger distances from the point source.