Variation Of Temperature Field Research Articles

Simulations of micropolar nanofluid-equipped natural convective-driven flow in a cavity

PurposeThis paper aims to focus on the natural convective flow analysis of micropolar nanofluid fluid in a rectangular vertical container. A heated source is placed in the lower wall to generate the internal flow. In further assumptions, the left/right wall are kept cool, while the upper and lower remaining portions are insulated. Free convection prevails in the regime because of thermal difference in-between the lower warmer and upper colder region.Design/methodology/approachThe physical setup owns mathematical framework in-terms of non-linear partial differential equations. For the solution purpose of the differential system, finite volume method is adopted. The interesting features of the flow along with thermal transportation involve both translational and rotational movement of fluid particles.FindingsPerforming the simulations towards flow controlling variables the outputs are put together in contour maps and line graphs. It is indicated that the variations in flow profile mass concentration and temperature field augments at higher Rayleigh parameter because of stronger buoyancy effects. Higher viscosity coefficient implies decrease in flow and thermal transportation. Further, the average heat transfer rate also grows by increasing both the Rayleigh parameter and heated source length.Originality/valueTo the best of the authors’ knowledge, no such study has been addressed yet. Further, the results are validated by comparing with previously published work.

Longitudinal wave analysis of infinite length piezoelectric circular rod based on temperature effect

Piezoelectric elements have been commonly used because of their wide applications in sensors, transducers, and some micro intelligent structures. However, in the fields of aviation, aerospace, and automation, some relevant equipment works in a harsh environment and is susceptible to the temperature change, thereby leading its performances to be greatly affected. Therefore, the problem of nonlinear wave relating to piezoelectric circular rods in different temperature fields is studied by modeling and numerical analysis. Firstly, based on the theory of finite deformation, we take infinite piezoelectric circular rod as a research object and consider the effects of transverse inertia and equivalent Poisson's ratio under the thermoelectric coupling action. Using the Hamilton principle and introducing the Euler equation, the longitudinal wave equation of piezoelectric circular rod is obtained. Secondly, Jacobi elliptic cosine function and Jacobi elliptic sine function expansion method are used to solve the wave equation of the piezoelectric circular rod, and the solitary wave solution and the exact periodic solution of the wave equation are obtained. It is found that the periodic solution can be reduced into a solitary wave solution under certain conditions, and it is proved theoretically that there may be solitary wave stably propagating in a piezoelectric circular rod. Finally, the dispersion curves of different wave velocity ratios and the curves about influences of temperature field on the waveform, amplitude and wave number of the piezoelectric rod are obtained by Matlab. The numerical results show that the wave velocity decreases with the increase of temperature when the wave velocity ratio is constant. Given the temperature is constant, it can be found that with the increase of the ratio, the amplitude of solitary wave gradually increases while the wavelength gradually decreases. In addition, the images obtained show that although temperature change can cause the characteristics of solitary waves to change, the solitary waves are always symmetrical bell shaped waves in the propagation process, reflecting the stability characteristics under the combined action of nonlinear and dispersion effects. Therefore, the variation of temperature field can influence and control some propagation characteristics of solitary waves. Moreover, the wave theory has been widely used in the nondestructive testing of structures and the improving of information transmission quality due to its special stability.

玉龙雪山地区地表三维温度场时空变化分析

玉龙雪山地区地表三维温度场时空变化分析

Influence of Polarization-Maintaining Fibers on Azimuth Transmission Under Variable Temperature and Electric Field

Influence of Polarization-Maintaining Fibers on Azimuth Transmission Under Variable Temperature and Electric Field

Temperature Field Variation Law of Low Exothermic Polymer Grouting Material in Repairing Void Damage of Frozen Soil Subgrade

In this study, the self‐developed grouting mold was used to study the heat release characteristics of different density polymer grouting material under different temperature conditions. The spatial distribution characteristics of the frozen soil subgrade temperature field under the effect of polymer grouting repair were analyzed. Further, the rules governing the temperature change of a frozen soil subgrade monitoring point under the effect of polymer grouting repair were studied. The heat transfer mechanism of polymer grouting material in frozen soil subgrade was revealed. The results showed that in the void region of the frozen soil subgrade, a discontinuity zone appeared in the temperature field distribution isotherm due to the effect of voids; this zone exhibited a layered radioactive distribution along the two sides of the void area. Furthermore, during the exothermic stage of the curing reaction, the temperature distribution isotherms changed from a layered radioactive distribution to a ring distribution that decreased from the inside to outside. During the natural cooling process, the peripheral temperature of the ring isotherm first decreased and a negative temperature ring‐shaped isotherm gradually formed. Finally, the upper boundary of the influence of the heat energy released by the curing reaction on the frozen soil subgrade temperature field was determined to be 30 cm, and the lower boundary was 20 cm.

Study on temporal and spatial variation of temperature field in horizontal freezing and thawing settlement

Artificial freezing method is commonly used in underground engineering excavation, such as mine, foundation pit and subway. The problem of post-construction thaw settlement has attracted more and more attention, but it is difficult to calculate the development law of thaw temperature field of complex frozen curtain by analytical method. Therefore, this paper adopts numerical method to study this problem. In this paper, taking the horizontal freezing construction of a subway connecting passage as an example, the development law of temperature field in the melting process is analyzed, and the results are basically consistent with the measured data. As a general means, numerical simulation is feasible to simulate the development law of temperature field in horizontal melting of complex curtain. The results of this paper can be used to guide the design and construction of artificial freezing.

The role of heat-flux–temperature covariance in the evolution of weather systems

Abstract. Local diabatic heating and temperature anomaly fields need to be positively correlated for the diabatic heating to maintain a circulation against dissipation. Here we quantify the thermodynamic contribution of local air–sea heat exchange on the evolution of weather systems using an index of the spatial covariance between heat flux at the air–sea interface and air temperature at 850 hPa upstream of the North Atlantic storm track, corresponding with the Gulf Stream extension region. The index is found to be almost exclusively negative, indicating that the air–sea heat fluxes act locally as a sink on potential energy. It features bursts of high activity alternating with longer periods of lower activity. The characteristics of these high-index bursts are elucidated through composite analysis and the mechanisms are investigated in a phase space spanned by two different index components. It is found that the negative peaks in the index correspond with thermodynamic activity triggered by the passage of a weather system over a spatially variable sea-surface temperature field; our results indicate that most of this thermodynamically active heat exchange is realised within the cold sector of the weather systems.

Distributed optical fiber monitoring test and numerical simulation analysis of water-heat coupling process

The distribution of shallow ground temperature field is controlled by the complex water-heat coupling effects of surface temperature, shallow groundwater temperature, and groundwater flow. An indoor medium-scale model box was established to explore the variation law of the shallow ground temperature field in the process of water-heat coupling between subsurface water and groundwater by using various temperature sensors. Based on this test, a two-dimensional numerical simulation was carried out with FEFLOW. The analysis combining the test and simulation results showed that distributed optical fiber monitoring can effectively monitor the temperature field. Additionally, the temperature data can be calibrated by FBG and PT100 sensors that are available to recognize the distribution of ground temperature field accurately. The groundwater flow plays an important role in the variation of temperature field; the evolutionary tendency of temperature field has roughly the same performance in soil layers as long as they share the same permeability and thermal properties. Thus, different characteristic layers will affect the distribution of seepage field, further controlling the temperature field. Finally, this work can be potentially used to quantitatively evaluate the storage potential of shallow geothermal energy at the city scale.

Transient temperature field analysis of variable viscosity RTHSB with a special structural cavity

A radial thrust hydrodynamic sliding bearing (RTHSB) with special shaped cavity had been designed. Taking the instantaneous temperature rise characteristics of RTHSB as an analysis object, considering the influence of inlet lubricating oil velocity and transmission shaft speed, a dynamic simulation method of variable viscosity temperature field is proposed, and the mathematical model of instantaneous temperature rise of time-varying oil film is constructed. The correlation equation between instantaneous temperature rise and oil film variable viscosity is analyzed, the lubricating performance of a special-shaped cavity with variable thickness of the oil film considering real-time full operating conditions is revealed, and the alternating transient laws of oil film thickness with variable viscosity and its instantaneous temperature rise for no-load, heavy-load, and different rotating speeds are studied. It is obtained that the higher temperature area of profiled shaped cavity on reverse flow side extends to oil seal side with increase of rotating speed. The dynamic simulation of variable viscosity of RTHSB with different film thickness is simulated by using FLUENT software and the trend of transient film temperature field distribution of in special-shaped cavity is evaluated. The rationality of the mechanism analysis and numerical simulation results in this paper has been verified.

Research on Three-Dimensional Ocean Temperature Field Variation Model Based on Assimilation and Reconstruction of Regression Equation

Qin, F.; Zeng, W.; Zou, C., and Yang, J., 2020. Research on three-dimensional ocean temperature field variation model based on assimilation and reconstruction of regression equation. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 37–41. Coconut Creek (Florida), ISSN 0749-0208.For a long time, natural marine ecosystems have been subject to strong human intervention and global environmental changes. Therefore, it is a meaningful challenge to objectively evaluate the constituent elements of marine material transport, energy flow, and system functions. Besides, the calculation method of three-dimensional (3D) ocean temperature fields is improved in the paper by establishing regression model assimilation and reconstruction of 3D ocean temperature fields. Moreover, according to Guinethut's method, the model is reconstructed with the help of 3D monthly average temperatures and the salinity field of the Copernicus Marine Environment Monitoring Service. Then, monthly average sea surface data sea level anomaly and sea surface temperature from the satellite observations of the next year are used to derive 3D monthly average temperatures of the next year field. Additionally, the data sets of adjacent or similar years are applied to obtain linear regression relationships between sea surface and underwater features, which can improve the accuracy of reconstruction. The most optimal interpolation method is used to assimilate the measured data of Argo to increase accuracy. Finally, after data analysis and comparison, it is proved that compared with other methods, the observation value of the data model established in research content of the paper is further improved, which provides important reference for marine ecological protection work.

A new modeling method for thermal errors of motorized spindle based on the variation characteristics of spindle temperature field

Motorized spindle is a component with complex thermal properties. Its thermal boundary conditions change with operating conditions, and thus, the variations of spindle temperature field under different conditions are not exactly the same. Models with fixed structures and fixed coefficients have difficulty in predicting the spindle thermal error with high accuracy and stability. To solve this problem, study of the variation rules of the spindle temperature field is conducted in this paper. The variation process is divided into two stages: the non-uniform variation stage and the uniform variation stage. The variation characteristics are concluded into two parts: the overall variation tendency and the variation of temperature distribution from the inside to outside of the spindle. These conclusions provide a new perspective for temperature variable selection and coefficients adjustment. Based on the variation characteristics of the spindle temperature field, a new modeling method for spindle thermal errors is proposed. The basic temperature, the difference between temperature near the internal heat source and the basic temperature, and the ambient temperature are applied as input variables. The coefficient of the second input variable is set to adjust adaptively according to the spindle status. This method puts more emphasis on the variation rules of the spindle temperature field and can significantly increase the accuracy and the robustness of the prediction model. The model coefficients are optimized by PSO (particle swarm optimization). According to the experimental verification, the variation ranges of residual errors are reduced by at least 62% when predicting the thermal error in X-direction with the proposed model.

Theoretical and numerical investigation of entropy for the variable thermophysical characteristics of couple stress material: Applications to optimization

Transportation of heat and mass along with irreversibility analysis for the flow of Couple stress fluid past over a nonlinear stretched surface is reported in this exploration. The novel features and purpose of this report is to notice the involvement of variable thermophysical characteristics i.e. (variable magnetic field, thermal conductivity, diffusion coefficient) for the couple stress model. Flow is produced over a non-linear stretched surface under constant pressure. Variable wall temperature, wall concentration and variable magnetic field are observed. Thermal transport is influenced by thermal radiation. Conducting mass in the light of Fick's second law is derived by adding a chemical reaction. Flow presenting partial differential equations describing the conservation laws are modelled under boundary layer approximation in Cartesian coordinate system. Similarity transformation is used to convert these coupled nonlinear fluid flow equations into ordinary differential equations. The converted nonlinear coupled system of differential equations is solved analytically using optimal homotopy procedure. Mathematical software Mathematica 11.0 is used to handle the computational complexity. Solution for velocity, temperature, concentration and entropy generation is displayed and it is discussed for the flow against numerous influential parameters. Numerical values for the dimensionless stresses, rate of heat and mass transfer is computed and tabulated. Moreover, limiting case of present exploration is compared to that of existing literature and an excellent agreement in results is noted. Also, it has been drafted that magnetic parameter retards the flow, whereas, the increment in ratio parameter and fluid parameter upsurges the velocity field.

Analysis on variations of ground temperature field and thermal radius caused by ground heat exchanger crossing an aquifer layer

Due to the groundwater migration in the underground aquifer, the heat transfer between ground heat exchangers and surrounding ground changes from heat conduction to the conjugated conduction–convection mode. To investigate the aquifer effects on the ground temperature distribution surrounding the ground heat exchanger, a realistic model was established and numerically solved, including a ground heat exchanger and alternatively stacked aquifer and aquifuge layers. The results show that a variation in groundwater velocity would result in a significant fluctuation in the aquifer temperature field close to the ground heat exchanger, but has less effect on the aquifer temperature field away from the ground heat exchanger. The difference between the initial temperature and local stable ground temperature, and the time for the aquifer to reach the stable temperature are both negatively correlated with the groundwater velocity, and positively correlated with the distance to ground heat exchanger on the downstream. The thermal influence radii are ranging from 7.4 m to 143.0 m in the aquifer layer under tested groundwater velocities ranged from 3.15 m/a to 315 m/a respectively, while the radii of aquifuge layer are about 8.3–8.4 m. There exists a critical velocity that makes the radius of thermal influence in the aquifer layer the same as that in the aquifuge layer. When the groundwater velocity is greater than the critical velocity, the thermal influence radius shows an increasing trend with the increase of aquifer layer thickness, while it shows a reversed trend for the velocity lower than the critical velocity.

Time period of transverse vibration of skew plate with parabolic temperature variation

Time period of natural transverse vibration of a nonhomogeneous skew (parallelogram) plate with variable thickness and temperature field has been investigated on clamped CCCC and combination of clamped and simply supported CSCS edge conditions. The thickness variation on the plate is assumed to be linear in two dimensions, and the temperature variation on the plate is considered to be parabolic in two dimensions. For nonhomogeneity, authors considered circular variation in density. The Rayleigh–Ritz technique is applied to solve the differential equation of motion. A comparative analysis of frequency modes of the present study with the available published result is also given to support the present findings. The convergence study of obtained results is also presented with the help of figures.

Numerical simulation and analysis of enhanced heat transfer in corrugated tube heat exchanger

At present, in many fields such as petrochemical industry, in order to make better use of heat energy and reduce energy consumption in the process of equipment operation, heat transfer enhancement of heat exchange equipment has attracted more and more attention. Corrugated tube has many advantages compared with other smooth tubes, which are enhancing heat transfer, strong anti-fouling ability and easy to clean. In this paper, a heat exchanger with corrugated tube is studied. The geometry is meshed with the software GAMBIT. It is used with Fluent software and the initial and boundary conditions are set. Heat transfer performance between smooth tube and corrugated tube at the same inner wall temperature and velocity. Then, the influence from inlet velocity on heat transfer performance is investigated. The variation of temperature field, pressure field and velocity field in corrugated tube heat exchanger with different inlet velocity is discussed. The results show that the enhanced heat transfer effect of corrugated tube is much better than that of smooth tubes. At three different inlet velocities (0.5m/s, 1m/s, 3m/s), the enhanced heat transfer effects of the corrugated tube heat exchanger are different. With the increase of inlet velocity, the heat transfer effects of corrugated tube heat exchanger are enhanced, but the extent of enhancement decreases. In the range of this paper, the optimal inlet velocity is 0.5m/s in order to obtain the more heat transfer quantity and lower operation cost.

Modeling the influence of variable temperature fields on the stressed state of offshore facilities

The article considers the influence of temperature fields on the stress state of offshore facilities using the example of fixed offshore platforms for oil and gas production. It is noted that there is no theory for offshore oil and gas facilities that would allow a numerical description of the nature and mechanism of action of both conventionally stationary and variable temperature fields. An analysis of various literature sources showed that currently there are solutions for the dynamics of propagation and stress state for an axisymmetric temperature field, for a non-axisymmetric case, characteristic of the operating conditions of the support blocks of offshore platforms, there is no such solution. The author notes that a change in the thermal state of the elements of offshore facilities as a result of various factors leads to a change in their stress state. In some cases, in the presence of significant defects, these defects act as stress concentrators, thereby increasing the nominal strain. A numerical-analytical modeling of the effects of both variable and conditionally stationary fields was carried out, which made it possible to identify a number of patterns.

Effects of aquifer on heat exchange process in geothermal applications

Geothermal energy has been widely used in the field of the building heating through the ground heat exchanger (GHE). The groundwater flow in the aquifer is one of the significant factors affecting the heat exchange process between the GHE and ground by promoting the pure conduction to the conjugated convection and conduction heat transfer. In this paper, the variations of the ground temperature field and the thermal influence radii subject to the existence of aquifers were investigated numerically. The geometrical models consisting of a coaxial heat exchanger, multiple aquifer and aquifuge layers were established to study the effect of groundwater velocities and the number of aquifer layers on the GHE system. The results reveal that the heat exchange capacity of the GHE is enhanced when the groundwater velocity increases. The increased number of aquifer layers can also enhance the heat exchange capacity with the tested groundwater velocity at 315 m/a or 31.5 m/a, but would weaken it with the velocity of 3.15 m/a. In addition, it is found that the aquifuge temperature field is affected by the aquifer layer, and the thermal influence radius of GHE is dominated by the groudwater velocity of aquifers when the velocity is larger than the critical velocity. Conversely, the thermal influence radius is governed by the thermal diffusivities of aquifuges for the groundwater velocity samller than the critical velocity.

The design of ignition systems and a study of the development of the high temperature zone in well-type underground coal gasification

To investigate temperature field expansion behavior during the ignition stage, the variation of temperature fields of 12 sites versus time were studied using thermocouples during the ignition process. The results showed that the temperatures measured, and combustion processes, were not uniform. At the position where the igniter had started successfully, igniter 10 showed the smoothest flow in its exhaust holes, followed by igniters 4 and 1, successively. At the position of igniter 10, the ignition materials burned well and the temperature curve was smooth, but the highest combustion temperature of oil-containing split wood layer and coke layer was only 393 °C, the highest combustion temperature of block coal layer and solid coal wall was only 591 °C and 936 °C respectively. At the position of igniter 1, the ignition materials burned inadequately and the temperature curve was rough, but the highest combustion temperatures of oil-containing split wood layer, coke layer, block coal layer and solid coal wall were as high as 960 °C, 983 °C, 899 °C and 1280 °C respectively. The presence of the ignition source ensured, but did not determine, the occurrence of ignition. The temperature field in the gasified area could expand transversely by spreading combustion of the burning front and transverse movement of high-temperature gases to ignite the ignition materials away from fire sources. In locations with high exhaust resistance, the temperature field expanded primarily through the spreading of the burning front, while in the area with low exhaust resistance, the temperature field mainly through expanded the transverse movement of high-temperature gases.

An integrated experimental system for gas hydrate drilling and production and a preliminary experiment of the depressurization method

The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device, and the resulted boundary effect is so obvious due to the small size of samples in the reaction kettle that the experimental results will be difficult to apply in the field. In this paper, an integrated experimental system for drilling and exploitation of gas hydrate is developed innovatively based on the idea of depressurization method and the technological process. This experimental system consists of high-pressure vesselmodule, drilling & extraction module, liquid supply module, gas supply module, confining pressure loading module, back-pressure control module, three-phase separation module, temperature control module, data acquisition module and an operational platform. The hydrate-bearing samples similar to marine hydrate formations were prepared inthe experimental system with the actual geological surroundings simulated. The electrical resistance tomography was used to real-time monitor the dynamic distribution of gas hydrate in sediments inside the high-pressure vessel (521 L). This experimental system can also simulate the process of wellbore drilling in hydrate reservoirs and depressurization extraction, and realize the real-time monitoring of parameters in the whole production process such as gas production, water production, sand production, temperature, pressure, etc. We carried out a preliminary experiment on the CO2 hydrate extraction via depressurization by using this experimental system. Fundamental procedures for data acquisition and analysis were established and verified. The variations of temperature and pressure fields and gas/water output behaviors in the reservoirs were both achieved. The results show that (1) the gas and water production rate fluctuate greatly even at a constant backpressure; (2) the reservoir temperature distribution is uneven during hydrate decomposition, and the maximum temperature is decreased by 5 °C, suggesting that the hydrate decomposition is heterogeneous and stochastic. The abundant and credible experimental results based on this system are expected to provide important data support for marine gas hydrate production tests.

Strain-Based Performance Warning Method for Bridge Main Girders under Variable Operating Conditions

This paper proposes a strain-based performance warning method for bridge main girder monitoring using the long-term data obtained for varying load conditions, i.e., the variations in temperature, wind, and traffic load. Because the temperature field variation of the main girder is easy to measure, a correlation model between temperature and strain of the main girder was first established through a novel representative temperature, namely, the canonically correlated temperature. Based on this model, temperature effects on the main girder strain can be accurately estimated and eliminated. However, the influence of wind and traffic load on the main girder strain was difficult to quantify. Thus, principal component analysis was then employed to model the main girder strain after eliminating temperature effects, and the first two principal components were extracted to represent the effects of wind and traffic load, which could subsequently be eliminated. The remaining principal components were then used to reconstruct the model errors, which were minimally influenced by the varying operating conditions. After this analysis, two warning indexes (i.e., the Euclidean distance and the Mahalanobis distance) were defined for the model errors and the remaining principal components to detect potential performance degradations. In addition, a location index was deduced based on contribution analysis to indicate where the performance degradation occurs. Finally, an engineering application to a cable-stayed bridge was carried out to verify the capability and validity of the proposed method.