Transient Temperature Analysis Research Articles

The Analysis of Transient Temperature in the Wellbore of a Deep Shale Gas Horizontal Well

The Analysis of Transient Temperature in the Wellbore of a Deep Shale Gas Horizontal Well

Enhancing sp3 formation in DLC on low thermal conductivity substrate: Interval deposition minimizing ion energy sensitivity

Depositing sp3-rich diamond-like carbon (DLC) on low thermal conductivity substrates is difficult due to the high sensitivity of sp3 formation to ion energy. This sensitivity is attributed to the heating effect of ion bombardment during plasma-enhanced chemical vapor deposition (PECVD) processing. This study introduced an interval deposition method aimed at minimizing the ion energy sensitivity, thereby achieving sp3-rich DLC deposition and broadening the process window. The variation in sp3 content of deposited DLC showed that the interval deposition can enhance sp3 formation, which is particularly significant when the single deposition duration is ≤1 s and the ratio of interval duration to deposition duration is ≥3. Deposition experiments with varying bias voltages confirmed that the ion energy sensitivity of sp3 formation in DLC can be effectively reduced by the proposed method. The analysis of transient film temperature during the deposition process revealed that this method took effect by limiting the temperature elevation of the film. Performance comparison showed that the adhesion of films to the substrate was improved by 138 % using the interval deposition method, compared to the traditional continuous deposition. This user-friendly and high-tolerance deposition method can significantly advance the application fields of DLC coatings.

Experimental Analysis of Heat Transfer Post Quenching of Medium Carbon Steel

<div>Transient temperature analysis is involved in the thermal simulation of the heat treatment process, in which the hot metal temperature changes with respect to time from an initial state to the final state. The critical part of the simulation is to determine the heat transfer coefficient (HTC) between the hot part and the quenching medium or quenchant. In liquid quenching, the heat transfer between the hot metal part and water becomes complicated and it is difficult to determine HTC. In the current experimentation a medium carbon steel EN 9 rod with a diameter of 50 mm and length 100 mm was quenched in water and ethylene glycol mixture with different concentrations. A part model was created; meshed and actual boundary conditions were applied to conduct computational fluid dynamics (CFD) analysis. In order to validate CFD analysis the experimental trials were conducted. Experimental results showed a reduced cooling rate for the specimen, and also a reduction in heat-carrying capacity of the mixture, which is attributed to the addition of ethylene glycol.</div>

Thermal shock fracture in a cracked strip: Incorporating convective heat transfer between lateral surfaces and ambient environment

This paper presents a comprehensive analysis of transient temperature and thermal stress around a thermal insulated crack in a finite thermoelastic strip subjected to thermal shock based on the dual-phase-lag (DPL) heat conduction. A detailed investigation of the effect of convective heat exchange between the lateral surfaces of the strip and the ambient environment is conducted. By employing integral transform technique, the thermoelastic crack problem is reduced to a set of singular integral equations, and solutions for the transient temperature distribution and dynamic stress intensity factors (SIFs) at the crack tips are then obtained. Numerical results reveal a considerable temperature gradient near the heating surface when both the high convective heat transfer coefficient and thin strip are involved. Consequently, the SIFs in such scenarios where cracks are located close to the heating surface are significantly larger compared to those calculated by neglecting the convective heat loss. Furthermore, during the initial period following a thermal shock, the SIFs may exhibit higher magnitudes than the steady-state values. These findings emphasize the importance of accounting for the influence of convective heat exchange with the ambient environment in material design and optimization to enhance fracture resistance under transient thermal loading.

Transient temperature analysis and computation in a 2-layer rectangular absorbing medium with a semitransparent diffuse interface and black surfaces

The 2-layer medium has a semitransparent diffuse interface and four black surfaces. The fully implicit finite difference method is used to discretize the 2-D transient differential heat transfer equation, in which a radiative source term is considered. The radiative source term is expressed by radiative transfer coefficients, which are solved by establishing functions to trace the reflection and transmission of radiative energy. By using the Patankar linearization method, additional source term method, and alternating direction implicit method, temperature distribution within the 2-layer medium is solved. The increase in the refractive indexes of the 2-layer medium makes the temperature distribution of the composite more uniform and the time to reach a steady state to be reduced. Compared with pure radiation, the participation of conduction makes the heat transfer ability of the 2-layer medium to be enhanced and the temperature distribution discontinuity at the interface disappears.

Spatial and temporal evolution of localized deformation in NiTi tubes in a constant stress thermal cycle: Experiments and analysis

A novel experimental setup is presented that allows for precise control of thermal and mechanical loads, and simultaneous monitoring of the temperature and the full-field deformation of small SMA structures that undergo phase transformations. The facility is used to conduct two experiments in which NiTi tubes are taken through a temperature cycle under constant load that leads to phase transformations in the form of helical localization bands that propagate along the specimen. The latent heat of transformation causes a complex interaction with the prescribed load and thermal environment. By changing the rate of the airflow through the environmental chamber it is revealed that the velocities of the transformation fronts depend on the rate at which heat is removed/added by the controlled environment. The experiments are simulated using a new fully coupled thermomechanical extension of the constitutive framework developed by this research group. Key features of the framework include the modeling of the reversible A⇄M transformation through a single surface in the deviatoric stress-temperature space that obeys kinematic hardening; with the transformation strain and entropy as the internal variables governed by an associative flow rule; and the inhomogeneous deformation exhibited in tension being modeled as softening. The tube is analyzed in a finite element coupled static displacement transient temperature analysis, and taken through the cool/heat cycle of the experiment. The temperature-strain response is accurately reproduced with the two transformations initiating at essentially the same temperatures as in the experiment and propagating in similar localized banded manners at similar speeds. Reproduction of the complex behavior observed in the experiments requires the calibration of the constitutive model, its discretization, and the modeling of the structure and its boundary conditions to work together to near perfection. The simulation also demonstrated that the heat exchange between the structure and the environment, in the present analysis governed by only by convection, requires further enhancement.

Transient Thermal Analysis Model of Damaged Bearing Considering Thermo-Solid Coupling Effect.

As one of the important parameters of bearing operation, temperature is a key metric to diagnose the state of service of a bearing. However, there are still some shortcomings in the study of the temperature variation law for damaged bearings. In this paper, according to the structural characteristics of bearings, the influence law of thermal-solid coupling effect on bearing structure is considered, and a novel transient temperature analysis model of damaged bearings is established. First, a quasi-static analysis of the bearing is performed to obtain the variation laws of the key parameters of the bearing under thermal expansion. Then, the load variation law of the bearing under the condition of damage is discussed, and the heat generation and heat transfer of the damaged bearing during operation are studied. Based on the thermal grid method, a transient temperature analysis model of the damaged bearing is developed. Finally, the model is tested experimentally and the influence of the rotate speed and load on the bearing temperature variation is analyzed. The results show that the established model can effectively predict the temperature variation and thermal equilibrium temperature of damaged bearings.

Demonstration of RELAP5-3D for transient analysis of a dual coolant lead lithium fusion blanket concept

Our research aims to build a multiphysics framework for transient analysis of the Dual-Coolant Lead-Lithium (DCLL) blanket design of the proposed Fusion Nuclear Science Facility (FNSF) for all Anticipated Operational Occurrences (AOOs) using Reduced Order Models (ROMs). This paper presents an assessment of using RELAP5-3D for transient thermal-hydraulic blanket analysis of the DCLL design. Preliminary validation studies for the RELAP5-3D properties were conducted using a representative vertical flow loop model and a comparison study using experimental data from thermal convection corrosion loops at ORNL. These studies inspected the thermal hydraulic response of Lead-Lithium Eutectic (PbLi) systems within the RELAP5-3D code; mainly pressure drop and heat transfer, as compared to analytical calculations and experimental data. The Magnetohydrodynamic (MHD) pressure drop effect for liquid metal under the effects of a uniform magnetic field was implemented into our models using an equivalent forms loss coefficient based on the phasic momentum equations. We verified our implementation of MHD pressure drop within RELAP5-3D using a systematic approach consisting of two studies. Models were developed to perform comparison studies using experimental data from the Argonne Liquid metal EXperiment (ALEX) facility and the Magnetohydrodynamic PbLi Experiment (MaPLE) facility. Using the developed validation basis, we built a simplified DCLL channel model within RELAP5-3D, inspected MHD pressure drop and performed transient temperature analysis. The DCLL channel model used radial heating data from the International Thermonuclear Experimental Reactor (ITER) which was normalized to the FNSF design. A representative startup transient was performed using a relative power curve based on current PWR power ramp limits. This study demonstrated that RELAP5-3D ROMs are capable of accurate transient analysis of the DCLL blanket. We have since utilized MCNP to develop heating profiles based on the FNSF design and are working toward implementing them into our DCLL model.

Transient Pressure and Temperature Analysis of a Deepwater Gas Well during a Blowout Test

On one hand, a blowout test can clean the bottom of the well, and on the other, it can learn the productivity of the well, which is important work before putting the well into production and also the main basis for production allocation of the well. The accurate prediction of the blowout test process provides a theoretical basis for the design of a reasonable blowout test system and the determination of well cleaning time. During deepwater blowout tests, gas and liquid flows are unsteady in pipes, and flow parameters change over time. At present, accurately predicting changes in fluid temperature, pressure, liquid holdup, and other parameters in a wellbore during an actual blowout process using the commonly used steady-state prediction methods is difficult, and determining whether a test scheme is reasonable is impossible. Therefore, based on the conservation of mass, momentum, and energy during the blowout test process, in this study, formation, wellbore, and nozzle flows were coupled for the first time, and a time and space of unsteady pressure drop and a heat transfer differential equation system was established; furthermore, using the Newton–Raphson method, the equations were solved. Finally, the simulation of the transient flow of the blowout test was completed. Considering a measured deepwater gas well A as an example, the blowout test process was simulated, and the variations in the wellbore flow parameters were analyzed. Comparing the simulation result with the test data, we concluded the following. (1) During the blowout process, the wellbore temperature gradually increased; pressure at the bottom of the wellbore decreased; and pressure at the wellhead increased; and (2) the established model agreed well with the actual production data, and the average error of the wellhead pressure and temperature was less than 5%. Considering the high production capacity of deepwater gas wells, the use of large-sized tubing and nozzles to spray is recommended, which can improve the speed of clearing wells and prevent the formation of hydrate.

Bi-Fo time scaling method in the numerical simulation of transient conjugate heat transfer

Reliable transient thermal analysis plays a very important role in the engine safety analysis. Transient conjugate heat transfer simulation is an important way of temperature analysis. But there exists a great disparity in the time scales between solid conduction and fluid convection. The calculation cost of transient conjugate heat transfer analysis is very huge because of the tiny time step of computational fluid dynamics. The Bi-Fo time scaling method is proposed to improve the computational efficiency of transient conjugate heat transfer. On the one hand, this method carries out a similar transformation on solid heat conduction, scaling the calculation time with the product of density and specific heat capacity to maintain the consistency of Fourier number. On the other hand, it takes very short time for the fluid domain to recover stability after a boundary disturbance. Based on the above characteristic, the flow time is directly compressed to the same as that of the solid domain. It is verified by Mark Ⅱ vane that increasing the solid thermal diffusivity can reduce the time scale of heat conduction. In the situation of rapidly stable flow field, scaling flow time does not affect the solid thermal boundary under corresponding dimensionless time. Within the application scope, the Bi-Fo time scaling method can greatly reduce the time cost of transient conjugate heat transfer simulation while maintaining the accuracy of transient temperature analysis.

Investigation of ultrasonic welding of carbon fiber reinforced thermoplastic to an aluminum alloy using a interfacial coating

ABSTRACT An investigation on joining of carbon fiber-reinforced thermoplastics to an aluminum alloy 6061 has been demonstrated using ultrasonic plastic welding process. A separate energy director, as required for focusing heat generation at interface during ultrasonic plastic welding, is replaced by high-performance thermoplastic coating on aluminum via a fluidized bed to make the process convenient for industrialization. Besides this, the functional coating acts as an insulator that resists galvanic corrosion and avoids fretting damage on metallic substrates. Critical welding parameters were experimentally realized (weld time: 900 ms, hold time: 1200 ms, and horn pressure: 0.5 MPa) for a maximum shear failure load in a lap-type joint configuration that showed uniform melting with higher fusion between thermoplastics. The fracture surface and cross-section morphology were examined for different joint nomenclatures. Delamination and first-layer ply failures associated with interlaminar shear of composites were predominant with an effective interfacial adhesion (mechanical anchoring) on aluminum asperities yielding a structurally rigid joints. A significant strength improvement of 40% was attained in mechanically treated aluminum substrates. An appreciable joint strength in comparison with adhesive bonding was obtained within a cycle time of 2.1 s. The real-time transient temperature analysis during welding provided a strong correlation with the weld formation.

Transient analysis of layered beams subjected to steady heat supply and mechanical load

In this study, an analytical model is developed for the analysis of transient temperature, displacements, and stresses in simply supported layered beams. The beam is suddenly heated from the top and bottom surfaces by external steady heat sources and is subjected to a mechanical load. The temperature in each layer is variable along the thickness and follows the one-dimensional (1-D) transient heat transfer equation. The Laplace transform approach is used to obtain the transient temperature field in the beam. The thermoelastic constants of the beam are temperature-dependent. Dividing every layer into a series of thin slices, the temperature and the thermoelastic constants for each slice can be considered uniform. The two-dimensional (2-D) thermoelasticity theory is adopted to derive the governing equations of displacements and stresses in each slice. The transfer matrix method is applied to obtain the displacement and stress solutions for the beam. As an example, the distributions of transient temperature, displacements, and stresses in a three-layer beam are studied. The effects of the temperature dependent thermoelastic constants on the mechanical behavior of the beam are discussed in detail.

Study on the Thermal Performance and Temperature Distribution of Ball Bearings in the Traction Motor of a High-Speed EMU

The transient thermal performance of rolling bearings affects the mechanical performance and system safety of traction motors. Most of the traditional empirical formulas used in temperature analysis have been simplified and cannot be completely applied to the calculation of heat generation and convection heat transfer coefficients. Based on the comparative analysis of finite element transient temperature and experimental data, this paper proposes a correction method of mathematical model and derives an accurate calculation formula for the heat generation and lubricant convection heat transfer coefficient of ball bearings applicable for the non-driving end in the traction motor of a high-speed EMU (Electric Multiple Unit). The accuracy of the results has been verified by durability experiment data. In addition, with changes in speed, radial load and other factors taken into account, we have analyzed the influence of these time-varying factors on ball bearing temperature, as well as the temperature distribution law of each component in a grease-lubricated bearing, in a bid to lay a foundation for follow-up research on the heat transfer laws of traction motors and rolling bearings.

Estimating the initial-formation temperature and flowing-temperature gradient with transient-temperature analysis: Applications in gas reservoirs

The formation temperature constitutes one of the essential factors that affect the wellbore fluid temperature behavior in production mode. The amount and direction of the radial heat transfer between the surrounding formation and the wellbore depend on the temperature differential and thermal properties of the media.Traditional studies probing geothermal gradients depended principally on extrapolating the transient bottomhole temperature to infinite shut-in time for obtaining the undisturbed formation temperature. After that, a straight line from the surface to the bottomhole condition constituted the geothermal gradient. Of course, the implicit assumption in this approach is that a linear geothermal gradient exists in light of unavailability of depth-wise temperature measurements.This study presents a new transient-temperature analysis approach to determine the undisturbed formation temperature. Specifically, we show the application of the line-source solution that has roots in the temperature-diffusivity equation. Secondly, using the distributed temperature measurements associated with transient-pressure testing, we proved that the bottomhole or static temperature is time-dependent, leading to alteration of the geothermal gradient in a well's proximity. Finally, the lowering of the temperature-derivative plateau with increasing depth during well shut-in periods indicated an increase in thermal conductivity, resulting in a nonlinear geothermal gradient.

Thermo-mechanical coupling analysis of transient temperature and rolling resistance for solid rubber tire: Numerical simulation and experimental verification

The achievement of low rolling resistance and long-term durability of tires on various vehicles is of great challenge. Tire performances heavily depend on rubber properties; however, the thermo-mechanical coupling characteristics of rubber composites are complicated rendering the design of high-performance tires time-consuming and costly. In our research, the transient temperature and rolling resistance of a solid rubber tire were performed based on the thermo-mechanical coupling approach and nonlinear viscoelastic theory by using finite element method. Particular attention was paid to the strain cycles as the tire rolling on the road presents non-sinusoidal deformation. First, a static three dimensional tire-road contact analysis was conducted to obtain the principal strain cycles. Second, the 100th-order Fourier sine series was used to approximate the strain amplitude. Third, the heat generation rate proportional to the product of the loss modulus and the square of strain amplitude was calculated. The loss modulus was updated as a function of strain amplitude, temperature and frequency. Loss modulus softening effect was also considered. A practical method was proposed to compute the rolling resistance and transient temperature distributions by establishing a 2-D axisymmetric model. A rubber rolling tester was used to verify the numerical results. The comparison between numerical data and test data reveals that the proposed analytical method is a reliable approach to predict rolling resistance and transient temperature distribution for rubber tires. At last, the dependence of rolling resistance and heat build-up on thermal conductivity and loss factor were investigated by the parametric numerical experiments.

Three-dimensional transient temperature analysis of cooling roller for preparing amorphous ribbon

Planar flow casting (PFC) is a major method for industrial preparing amorphous ribbon. The key factors that affect ribbon formation in PFC are temperature and thermal stable time of cooling roller. This study proposes a new approach to investigate the transient three-dimensional temperature of the cooling roller using variable heat flux as the boundary condition. Firstly, the heat flux acted on the roller outer wall is calculated by two-dimensional heat transfer model. Employing the heat flux as the boundary condition, the three-dimensional transient temperature of the cooling roller is then analyzed. This study also examines the effects of the roller thickness and diameter on the temperature and stable time. Results show that the heat conduction in the roller not only in the radial direction but also in the width direction. The temperature is unevenly distributed, reaching the peak value in the middle width position, and the roller achieves thermal equilibrium after about 120s of casting. In addition, the roller thickness mainly affects the stable time and the temperature of the inner wall; the diameter affects the stable time as well as the temperatures of both the inner and outer walls. Finally, the reliability of the simulation approach and results are verified by measuring the roller transient evolution temperature on the spot with the infrared thermal imager. This study provides the reference for the selection of roller parameters and the prediction of roller stable time during the PFC process.

Thermal analysis of injection beam dump of high-intensity rapid-cycling synchrotron in J-PARC

The beam dump at the beam injection area in the J-PARC 3-GeV rapid cycling synchrotron (RCS) accepts beams that pass through the charge exchange foil without ideal electron stripping during the multi-turn beam injection. The injection beam dump consists of the beam pipe, beam stopper, radiation shield, and cooling mechanism. The ideal beam power into the injection beam dump is 400 W in the case of design RCS extraction beam power of 1 MW with a healthy foil, which has 99.7 % charge stripping efficiency. On the other hand, as a radiation generator, the RCS is permitted to be operated with maximum average beam power of 4 kW into the injection beam dump based on the radiation shielding calculation, in consideration of lower charge stripping efficiency due to the foil deterioration. In this research, to evaluate the health of the RCS injection beam dump system from the perspective of the heat generation, a thermal analysis was performed based on the actual configuration with sufficiently large region, including the surrounding concrete and soil. The calculated temperature and heat flux density distribution showed the validity of the mesh spacing and model range. The calculation result showed that the dumped 4 kW beam causes the temperature to increase up to 330, 400, and 140 °C at the beam pipe, beam stopper, and radiation shield, respectively. Although these high temperatures induce stress in the constituent materials, the calculated stress values were lower than the ultimate tensile strength of each material. Transient temperature analysis of the beam stopper, which simulated the sudden break of the charge stripper foil, demonstrated that one bunched beam pulse with the maximum beam power does not lead to a serious rise in the temperature of the beam stopper. Furthermore, from the measured outgassing rate of stainless steel at high temperature, the rise in beam line pressure due to additive outgassing from the heated beam pipe was estimated to have a negligible effect on beam line pressure. The flow and results of the evaluation in this analysis would provide a good indication for both the verification of the existing beam dumps, and the design of beam dumps in new accelerators with higher intensity beam.

Analysis and Calculation of Rail Transient Temperature During Electromagnetic Launch

The thermal characteristics of the interface between armatures and rails of electromagnetic railguns (EMRGs) have an impact on the state of armature-rail contact and the launching performance of its system. In the launching process of EMRGs, the temperature rise of rails is mainly caused by the Joule heat generated by the rail resistance and armature-rail contact resistance and the friction heat generated by high-velocity movement of armatures. According to the theories of electromagnetic field, conservation of energy, Joule’s law, and generation of heat by friction, this paper analyzes the property of the contact resistance of the interface between armatures and rails of railguns and the friction factor of the interface, and develops a formula to calculate the transient temperature of rails resulting from the Joule heat and friction heat. Through a launch experiment, such dynamic data as muzzle voltage, rail current, armature displacement, and velocity during the actual launching process are obtained to calculate relevant parameters such as contact resistance, rail resistance under velocity skin effect, and armature-rail contact pressure. Such parameters are substituted into the temperature calculation formula for calculation of the Joule heat generated by the rail resistance and armature-rail contact resistance and the friction heat generated by high-velocity movement of armatures. The calculation produces a curve of change of rail maximum temperature over time under the joint effect of the three factors, thus allowing for the calculation of the transient temperature of rails during the launching process.

The Inner Flow and Heat Transfer Analysis of Round Tube with Different Rotating Speed

Aiming at the inner flowing characteristics of round tube, the different transient cases of tube with rotating wall boundary are analyzed by CFD, and the six cases are determined according to the different rotating speed respectively. The fluid is water, with the same dimension of tubes, the negative pressure region moves forward in the tube as the increase of rotating speed, and the outflow velocity is high to 31.42 mm/s, being 348.22% more than that of steady case. When the rotating speed is 1 rev./s, there is a lowest temperature band between the wall and center high temperature flow. In the transient temperature analysis, the high temperature cloud changes to cone-like shape, and there is a swirl with lower temperature at the inlet part with a large depth into the tube center. The case with 2 rev./s has the much more uniform temperature distribution than others.

Analytical solution and analysis of transient temperature of silicon irradiated by repetitive laser pulse

In this paper, the physical model of the temperature of silicon irradiated by repetitive laser pulse is established based on classical Fourier heat conduction theory, and the analytical solution of temperature are obtained by using Laplace transformation method. The temperature for different duty cycle, different pulse number and different location inside the material are simulated and analyzed. Effects of duty cycle, pulse number and location inside the material on the temperature are investigated. The results of this paper can provide some guidance for experiments and mechanism study of the interaction between repetitive laser pulse and solid material.