Three-dimensional Temperature Distribution Research Articles

Modeling of three-dimensional exciplex pumped fluid Cs vapor laser with transverse and longitudinal gas flow

Abstract Considering the thermodynamical fluid mechanics in the gain medium and laser kinetic processes, a three-dimensional theoretical model of an exciplex-pumped Cs vapor laser with longitudinal and transverse gas flow is established. The slope efficiency of laser calculated by the model shows good agreement with the experimental data. The comprehensive three-dimensional distribution of temperature and particle density of Cs is depicted. The influence of pump intensity, wall temperature, and fluid velocity on the laser output performance is also simulated and analyzed in detail, suggesting that a higher wall temperature can guarantee a higher output laser power while causing a more significant heat accumulation in the cell. Compared with longitudinal gas flow, the transverse flow can improve the output laser power by effectively removing the generated heat accumulation and alleviating the temperature gradient in the cell.

A comprehensive numerical model for kerf width prediction in hot wire cutting of expanded polystyrene

Improving accuracy in cutting of expanded polystyrene (EPS) foam using hot wire depends on understanding and controlling the kerf width, which in turn depends on temperature distribution in the foam during cutting. We present here a comprehensive temperature-validated numerical thermal model that incorporates important factors such as convective heat transfer between the wire and molten/ablated foam and the surroundings, thermal coupling between the wire and EPS, temperature dependent EPS foam and wire properties and the latent heat of melting and ablation of EPS, to predict the three-dimensional temperature distributions in the EPS foam in the region immediately around the hot wire and across the entire width of the EPS foam being cut. Based on isothermal temperature contour at the melting point of the foam, kerf width is predicted and compared with experimental measurements. Average kerf width and kerf width variation across the width of the work are seen to be predicted reasonably by the model. The barrelling of the cut profile due to the variation of wire temperature along its length is also quantified and compared with experiments. Selectively switching off various model parameters such as temperature dependent EPS and wire properties and the thermal coupling between wire and EPS shows significant contributions of these factors towards the error in kerf width predictions. Convective heat losses are found to be important when the width of EPS being cut is less such as in thin sheets. As confirmed by experimental data, kerf width is higher near the work edges and stays constant within the bulk region of the work. The model developed comprehensively captures the thermal effects and thus can be used to improve precision while cutting EPS shapes.

Thermal characteristics and thermal stress analysis of a superheated water/steam solar cavity receiver under non-uniform concentrated solar irradiation

Solar cavity receiver is a vital component in a solar power tower (SPT) system, where concentrated solar irradiation is absorbed, converted into heat and carried away by a kind of heat transfer fluid. The cavity receiver usually suffers from the high-flux and non-uniform concentrated solar irradiation, which would cause local overheating, large temperature gradient and even thermal stress fracture of the receiver and bring challenges for the safety of its daily operation. Therefore, it is necessary to investigate the thermal and mechanical performance of the solar cavity receiver. In the present study, a superheated water/steam solar cavity receiver with three boiling panels and a superheater was chosen as the physical model. An integrated simulation method, which couples the Monte-Carlo ray tracing (MCRT) method, the appropriate heat transfer correlations, the finite volume method (FVM) and the finite element method (FEM), was employed to simulate the complicated heat transfer process inside the receiver and conduct the thermal stress analysis for the absorber panels. With this method, the three-dimensional wall temperature and thermal stress distributions were gained both on the boiling panels and the superheater, and the causes of thermal stress induced by different temperature gradients were analyzed in detail. The following results were obtained: 1) The heat flux, wall temperature and equivalent thermal stress distributions all appear highly non-uniform on the absorber panels; 2) The hot spots can be found on the membrane wall between the elbows of the boiling panels, which can easily generate the high thermal stress due to the large temperature gradient with their surroundings; 3) The bi-axial stress at the outer and inner radius of the boiling tubes can be created by the large radial temperature gradient, and the thermal stress varies as a cosine distribution across the circumference of the superheated tubes, which is induced by the large temperature gradient in the circumferential direction. Besides, the spot-like areas with high thermal stress can also be found on the superheated tubes due to the considerable nonlinear axial temperature gradient. Moreover, the thermal stress on the membrane wall connected with both the boiling and the superheated tubes has the definite directionality, which shows parallel to the tubes or perpendicular to the tubes; 4) The thermal stress concentration always occurs at the high-temperature and structural discontinuity locations. Here, the thermal stress of the superheater is 360 MPa higher than that of the boiling panels. In general, the superheater has both the higher wall temperature and thermal stress, which is more crucial for the safe operation of the superheated water/steam solar cavity receiver.

Development of seawater temperature announcement system for improving efficiency of fishery industry

ABSTRACT Obtaining accurate information about the seawater temperature and visualizing it in real time is of great importance for aquaculture fishers, as water temperature fluctuations due to tide inflows greatly affect the development of fish and shellfish. Fishery researchers install a lot of multiple depth water temperature continuous observation equipment in the sea, and then, they collect and accumulate the data on the seawater temperature to realize its visualization. In this research, we develop a novel system to visualize the current conditions of seawater and its variations over time based on the collected water temperature data. Our system allows representing the most recent seawater temperature information and its variation over time in the forms of a table, graph and a three-dimensional temperature distribution chart through a web browser. In addition, in this system, it is possible to download the seawater temperature information measured during a period in the past. Our system can be used to improve the efficiency of feeding, thereby reducing the costs associated with aquaculture maintenance; moreover, it can serve to avoid damages caused by red tide and to prevent fish diseases.

Measuring Three-Dimensional Temperature Distributions in Steel-Concrete Composite Slabs Subjected to Fire Using Distributed Fiber Optic Sensors.

Detailed information about temperature distribution can be important to understand structural behavior in fire. This study develops a method to image three-dimensional temperature distributions in steel–concrete composite slabs using distributed fiber optic sensors. The feasibility of the method is explored using six 1.2 m × 0.9 m steel–concrete composite slabs instrumented with distributed sensors and thermocouples subjected to fire for over 3 h. Dense point clouds of temperature in the slabs were measured using the distributed sensors. The results show that the distributed sensors operated at material temperatures up to 960 °C with acceptable accuracy for many structural fire applications. The measured non-uniform temperature distributions indicate a spatially distributed thermal response in steel–concrete composite slabs, which can only be adequately captured using approaches that provide a high density of through-depth data points.

Lucid characterization of unsteady heat conduction in large, square crossbars and cubes subject to uniform surface heat flux by way of “quasi–steady” Helmholtz equations

The technical paper addresses unsteady heat conduction in large, square crossbars and cubes heated continually with uniformly surface heat flux. The uniform surface heat flux is customarily provided by electrical, radiative and pool fire heating in engineering applications. This type of heating fall under the category of non-homogeneous Neumann boundary conditions. The existing traditional method for solving the unsteady, heat conduction equation in two and three dimensions with constant thermo-physical properties and subject to non-homogeneous uniform heat flux boundary conditions is the principle of superposition of partial solutions of simpler unsteady, heat conduction equations. For the latter, the exact, analytical temperature distributions are customarily expressed by infinite series regardless of the solution method. For the numerical evaluation of spatio-temporal temperatures, the main inconvenience of the infinite series lies in the poor convergence when the time is small. To prevent the impeding obstacle, the Transversal Method Of Lines (TMOL) is implemented in this work to transform the unsteady, two- and three-dimensional heat conduction equations into degraded “quasi steady”, two- and three-dimensional heat conduction equations, namely the homogeneous Helmhotz equations. Thereby, the exact, analytical solutions of the converted partial differential equations of elliptic type and homogeneous were determined by the standard method of separation of variables. The resulting approximate, semi-analytical two- and three-dimensional temperature distributions for large, square crossbars and cubes do not contain elaborate infinite series. Instead, the temperature disdtributions contain hyperbolic functions elucidating worthy compactness and superb quality, regardless of the time, either “small time”, “moderate time” or “large time”.

Elastothermodynamic damping modeling of three-layer Kirchhoff–Love microplate considering three-dimensional heat conduction

Elastothermodynamic damping is one of the most important energy loss mechanisms in micro/nano mechanical resonators, which is related to the high sensitivity and high resonance frequency characteristics of resonators. With the wide application of resonators, multilayer microplate resonators have been applied. In this paper, the elastothermodynamic damping models of three-layer of Kirchhoff–Love microplate under three typical boundary support conditions of Clamped-Clamped-Clamped-Clamped (C-C-C-C), Clamped-Free-Clamped-Free (C-F-C-F) and Clamped-Free-Free-Free (C-F-F-F) are established. Firstly, the thermoelastic mechanical equations of the microplate are given, and then the three-dimensional temperature distribution functions of the microplate are obtained based on the generalized orthogonal function method. Finally, the elastothermodynamic damping models are established based on the composite multilayer plate theory. The model in this paper is compared with the previous model and the finite element results.

Thermal performance and thermal stress analysis of a 600 MWth solar cylinder external receiver

The thermal stress plays an important role to assess the security of the solar receiver and is mainly affected by the temperature gradient. To study the thermal stress of the receiver, a MATLAB program was developed to study the distribution of temperature and thermal stress numerically, and the program was verified on the lab-scale receiver and it was found that the error between the calculated result and the experimental result did not exceed 10%. Then the in-house code was applied to a 600 MWth receiver to study its thermal performance and thermal stress numerically. The three-dimensional temperature and thermal stress distribution of the 600 MWth receiver were present in this work, and the maximum temperature of the tube and the maximum stress appeared in the last and first panel respectively. It was also found that the outlet temperature of the receiver obtained by the code was 574 °C, very close to the designed temperature 565 °C. The component stresses in tangential, radial and axial direction were analyzed, and the thermal stress in the tangential direction and the axial direction both had a transition from compressive stress to tensile stress along the radial direction, and thermal stress in the radial direction can be almost negligible. Besides, the thermal stress of the receiver in one day was studied, and the average thermal stress and the thermal stress ratio R were respectively 145 MPa and 1.843, and the maximum thermal stress of the receiver decreased 45.74% from 12:00 to 18:00 on the vernal equinox.

Volumetric imaging of flame refractive index, density, and temperature using background-oriented Schlieren tomography

Volumetric imaging represents one of the major development trends of flow diagnostics due to both the advancement in hardware and the requirement for more information to further understand complicated turbulent and/or reactive flows. Background-oriented Schlieren tomography (BOST) has become increasingly popular due to its experimental simplicity. It has been demonstrated to be capable of simultaneously recovering the distributions of refractive index, density, and temperature of flows. However, its capability in thermometry has only been demonstrated under the axisymmetric assumption, which greatly limits its applicability. In this work, we dedicated to developing a cost-effective BOST system for the simultaneous retrieval of refractive index, density, and temperature distributions for the asymmetric flame. A few representative tomographic inversion algorithms were assessed as well. Both numerical and experimental demonstrations were conducted and the results show that our implemented BOST can successfully reconstruct the three-dimensional temperature distribution with a satisfactory accuracy.

An experimentally verified three-dimensional non-stationary fluid model of unloaded atmospheric pressure inductively coupled plasmas

A three-dimensional non-stationary numerical model of spectrochemical and technological inductively coupled plasma (ICP) systems is presented in the paper. The model considers the ICP as a gaseous media (with temperature-dependent electric conductivity) interacting with electromagnetic field generated by inductive coil. The model is based on simultaneous solution of the Maxwell’s and gas flow equations together with the energy equation coupled-together by corresponding source terms and material properties to take into account inductive current forming within the carrier gas and subsequent Joule heating, the Lorentz force and how does it affect the gas flow pattern. It allows calculation of temporal evolution of three-dimensional distributions of electromagnetic fields, pressure, gas velocity and temperature within a plasma torch and a condensation chamber used for powder processing. The model is applicable for simulation of atmospheric pressure electrodeless plasmas under local thermodynamic equilibrium that consist of pure gases and their mixtures. Such operating conditions are typical for ICPs that are used for elemental analysis and technological powder processing. Special attention is paid to experimental verification of the model. The simulation results are cross-verified for both types of ICPs (spectrochemical and technological one) using high-speed optical and schlieren visualization of gas flows. The discrepancy between calculations and experimental data does not exceed 10%.

Analysis on light power and three-dimentional temperature distribution characteristics of gain guided and index alternate-guided fiber lasers

Gain guided and index alternate-guided (GGIA-G) fiber was suggested by our group recently. In this work, the improved rate equations of the GGIA-G fiber laser were established and solved. The pump and signal light power distribution along the fiber longitudinal axis were simulated under the conditions of forward, backward and bidirectional pump. Furthermore, a theoretical three-dimensional temperature distribution model of the GGIA-G fiber laser was established, and the temperature distribution characteristics along both the fiber longitudinal axis and radius were simulated and compared when the fiber was pumped with different methods. The research results show that different pump method has obvious influence on both signal light power distribution and the fiber temperature. When the fiber is forward pumped, the signal light power in the fiber is the highest, and when the fiber is bidirectionally pumped, the temperature of the fiber is the lowest. The research conclusions are helpful in the application of the GGIA-G fiber.

Effective solution of three-dimensional inverse radiation problem in participating medium based on RDFIEM

A novel integral equation method based on radiation distribution factor (RDFIEM) is developed for solving radiation transfer equation (RTE) to obtain radiation intensity signal in a small solid angle on a small point, which is effectively applied to reconstruct the three-dimensional (3D) temperature distribution in an absorbing, emitting and scattering medium. The spatial distribution of radiation intensity inside the medium can be derived by the reverse Monte Carlo method based on the radiation distribution factor (RDF), and source term distribution can be obtained by integration of RDFs. Consequently, according to the idea of integral equation method (IEM), the boundary exit radiation intensity with respect to the RDF and temperature can be deduced. It is worth noting that the RDF is only related to the geometry and radiation properties of the medium, which can be calculated only once to make RDFIEM be more efficient. Meanwhile, the error caused by the random number of RMC can be reduced by integrating the RDFs. As a consequence, the RDFIEM is particularly suitable for temperature field reconstruction. The directional radiation intensity signals obtained by charge-coupled device (CCD) camera are used as the known information to reconstruct the temperature distribution, the effects of CCD combinations, detection directions, optical thickness, boundary conditions, scattering type and scattering albedo, measurement and coefficient errors on the implementation of RDFIEM have been examined. The least square QR decomposition (LSQR) algorithm is introduced to solve the 3D temperature reconstruction problem. The results show that the temperature field can be reconstructed accurately and efficiently.

Effects of image positions on temperature reconstruction using light field camera

The light field camera has emerged as an optical flame temperature detection device owing to the refocusing feature. Combining this feature with the deconvolution algorithm, a three-dimensional flame temperature distribution can be reconstructed. However, the accuracy of reconstructing the flame temperature is limited by the actual image position. Based on the established flame and light field camera model, the proposed Lucy-Richardson and Nearest Neighbor Filtering joint deconvolution algorithm is applied to sectioned temperature reconstruction. Thus, the effects of image position using light field camera on temperature reconstruction are verified. The relative error of flame temperature reconstruction is less than 10%, if the flame is imaged in the middle of the light field image. However, if the flame is imaged at the image edge, the edge distortion and defocused state of the camera increase the relative error to less than 11% and 14%, respectively. The effects of image positions are not too significant for temperature reconstruction using light field camera.

Numerical modeling of peat burning processes in a vortex furnace with countercurrent swirl flows

The paper presents the process of peat burning in a swirl furnace with counter-current swirl flows and the results of a numerical study. The cyclone-vortex technology of solid fuel combustion allows the furnace volume of a boiler unit, its dimensions and weight to be reduced. The aim of the work is a numerical study of the combustion of pulverized peat in a cylindrical vortex furnace with counter-current swirl flows. The results of computer simulation of the combustion of pulverized peat with a moisture content of 40%, an ash content of 6%, and a higher heat of combustion QpH = 12.3 MJ/kg are presented. The results of the influence of the design parameters of the furnace and heat load (from 100-15%) are given as well. When the heat load is reduced to 15%, the entrainment of unburnt particles increases. The cooled and adiabatic furnace is studied. A significant entrainment of unburned particles is observed in a cooled furnace. The fields of temperature distribution, gas velocity, and particle trajectory in the volume and at the outlet of the furnace are determined. The 3-D temperature distribution in the furnace volume indicates the combustion of peat particles at temperatures (1300-1450?C). Values of the tangential velocity of a swirl flow near the furnace outlet reach 150-370 m/s, which ensures the efficiency of separation of fuel particles and a reduction in heat loss due to mechanical underburning (up to 0.06%). The results of a numerical study show that the diameter of peat particles affects the combustion process, namely coke of particles with an initial diameter from 25-250 ?m burns out by 96%, and particles with a diameter of about 1000 ?m are carried away from the furnace and do not burn. The furnace provides a complete combustion of dust particles of peat by 99.8% and volatiles by 100%.

Experimental characterization on pore parameter and the irradiation absorption efficiency of a series SiC foam specimens

This paper experimentally analyzes the thermal performance of a volumetric solar receiver with a series pore structures of silicon carbide foam. Twelve silicon carbide foam specimens with various porosities and pore diameters were systematically tested on a lab-scale test platform. Three-dimensional temperature distribution, including irradiated surface temperature distribution and internal solid temperature, were obtained. Non-uniform temperature distribution on the irradiated surface and internal field, as well as the corresponding thermal efficiency under different working conditions, was analyzed. The results demonstrate that pore diameter has a more significant effect on thermal performance than porosity, as the characteristics of the specific surface area among the examined samples were mainly determined by pore diameter. For the detected solid temperatures, the highest exceeded 1000 °C without any damage to the porous structure, and the maximum mean outlet air temperature exceeded 544 °C. The thermal efficiencies of the samples with smaller pore diameter were markedly higher in most cases. The best thermal efficiency was 85.4%, which was obtained from the specimen with pore diameter of 2.27 mm and porosity of 0.663. Optimal geometric properties of SiC foam absorbers may be characterized by small pore diameter and high porosity, which can beneficial by both the advantage of uniform irradiation absorption and effective interphase convection. The experimental data presented in this paper can provide a clear reference for the theoretical model and engineering design.

Damage technology of carbon fiber composites by high-power laser

Based on the layer characteristics of the carbon fiber and resin composites, the damage mechanism of high power laser beam on the carbon fiber target are investigated. Analyzing the laser ablation target, the layer ablation mechanism is introduced, which is composed of an ablation layer, a pyrolysis layer and an original layer. The finite element model of the laser ablation the carbon fiber composites was established, in which a Gaussian laser beam irradiated perpendicularly on the target. Because of the advantages of finite element gridding in spatial domain and finite difference gridding in time domain, the “birth and death element” method was used to accurately simulate the temperature distribution field of the laser damage target, and those elements were sequentially stripped, i.e. “killed”, exceeding the vaporization temperature “point” of the carbon fiber composites during the laser heating until the laser is shut off. Moreover, the laser damage experiment on the carbon fiber composites was carried out, the temperature distribution field of the laser irradiated target was measured, and the burn-through time of the carbon fiber target was recorded. It is found show that the birth and death element method with the sequent stripping way can be used accurately to simulate the three-dimensional temperature distribution field of the target and evaluate the laser damage efficiency to the targets.

Experimental Study of the Temperature Distribution in CRTS-II Ballastless Tracks on a High-Speed Railway Bridge

To study the temperature distribution in the China Railway Track System Type II ballastless slab track on a high-speed railway (HSR) bridge, a 1:4 scaled specimen of a simply-supported concrete box girder bridge with a ballastless track was constructed in laboratory. Through a rapid, extreme high temperature test in winter and a conventional high temperature test in summer, the temperature distribution laws in the track on the HSR bridge were studied, and the vertical and transverse temperature distribution trend was suggested for the track. Firstly, the extreme high temperature test results showed that the vertical temperature and the vertical temperature difference distribution in the track on HSR bridge were all nonlinear with three stages. Secondly, the extreme high temperature test showed that the transverse temperature distribution in the track was of quadratic parabolic nonlinear form, and the transverse temperature gradient in the bottom base was significantly higher than that of the other layers of the track. Thirdly, the three-dimensional temperature distribution in the track on HSR bridge was a nonlinear, three-stage surface. Furthermore, similar regularities were also obtained in the conventional high temperature test, in which the temperature span ranges were different from those of the extreme high temperature test. In addition, the conventional high temperature test also showed that under the natural environment conditions, the internal temperature gradient in the track layers changed periodically (over a period of 24 h).

Simulations of the Influence of the Heat Flux at the Shaft Surface of the Conical Slide Bearing on Its Hydrodynamic Lubrication and Operating Parameters

Abstract The aim of this work is to investigate, how in the adopted model of hydrodynamic lubrication of a conical slide bearing, the change of the heat flux value at the bearing shaft, affects bearing operating parameters. In this research, the authors use, the known from the literature, Reynolds type equation, describing the stationary hydrodynamic lubrication process of a conical slide bearing. The analytical, solutions, that determine the components of the lubricating oil velocity vector and the equation (analytical solution of energy equation) determining the three-dimensional temperature distribution in the lubrication gap, was also adopted from previous works. In order to obtain numerical solutions, the Newton’s method was used, and the derivatives in the Reynolds type equation were approximated by the finite differences. An application of the method of subsequent approximations allowed considering the influence of temperature, pressure and shearing rate on the viscosity of lubricating oil. The considerations were performed by adopting the Reynolds condition of the hydrodynamic oil film. It was tested, how the assumed value of the heat flux on the bearing shaft surface affects the values of the obtained operating parameters, i.e. the transverse and longitudinal component of the load carrying capacity, friction force and coefficient of friction.

Semi-analytical solution of three-dimensional thermoviscoelastic behaviors for a fiber metal laminated plate subjected to laser shock processing

The three-dimensional transient temperature distribution for a fiber metal laminated (FML) rectangular plate during laser shock processing has been obtained previously based on the separate variable method (SVM). Then the three-dimensional thermoviscoelastic governing equations are formulated based on Hamilton variational principle subsequently. The obtained thermoviscoelastic nonlinear integral-partial differential equations are solved by applying the Galerkin method and Newmark method in space and time domain, respectively, which differs with other publications. Meanwhile, Newton-Cotes trapezoidal formula is adopted to conduct the convolution operator for the transforming algebraic equations. The research aims at giving the semi-analytical solution of three-dimensional thermoviscoelastic behaviors for the FML structure subjected to laser shock processing, besides understanding the influences of temperature, boundary condition, laser moving velocity as well as number of fiber species and FML layers on the dynamic characteristic (such as deflection, vibration frequency and stress components) of the FML structure. Comparing with the deflection, the in-plane displacement is more sensitive to the temperature parameter, and normal stress caused by temperature is far greater than that caused by deformation. Young's modulus E2 for S2-glass fiber epoxy is less than that of glass polymer about 61.7%; shear stress σxy is only associated with shear modulus Gxyl(t); Shear stress σxz is only associated with rotation angle ϕ and deflection, while normal stress is associated with in-plane displacement and temperature increment.

Study of the Influence of Ventilation Pipeline Setting on Cooling Effects in High-Temperature Mines

The high-temperature environment is a major factor that affects deep mining. Cooling has become a major expense, accounting for up to 25% of the total energy consumption of such mines. To address methods of cooling and the cooling cost, this paper studies the influence of the ventilation duct layout on the cooling effect. Six models were created in ICEM-CFD (3D modeling software), and the influence of cold airflow diffusion on the temperature of the mine environment was numerically simulated using ANSYS Fluent. Under the condition of the same ventilation volume, two models utilizing single pipe and double pipe scenarios were established, and six points were selected as the pipeline suspension position, forming six ventilation duct models. The cooling effect of each model was evaluated by analyzing the average temperature of the roadway section, the three-dimensional distribution of the roadway temperature and the velocity streamline of the whole roadway. The results show that the double-tube model has greater advantages than the single-tube model does, due to its superior local temperature, average temperature of the cross-section, range below 303 K, temperature uniformity and local wind speed. Among the models, model 4 (diameter of 0.5 m, 1.9 m away from the bottom of the roadway and 2.4 m away from the center of the circle) is the best pipeline layout scheme for comprehensive temperature values, roadway temperature uniformity and other factors. The average temperature is 299.3 K within 8 m from the mining face, which is 1.66 K lower than that of the single tube model. This configuration will increase the comfort of the mining environment and reduce cooling costs. These results can provide a reference for ventilation duct layouts of roadways in high temperature mines.