Steady-state Thermal Model Research Articles

Optimization of a moisture separator reheater

The optimization of component size aimed to minimize the weight and volume is an important issue to a nuclear power plant design. The optimization algorithm is applied to determine the optimum structural and operation parameters of components in order to reduce the difficulty of manufacture and transport of large components in those nuclear power plants with high powers. A preliminary optimal design is performed on the moisture separator reheater of Qinshan I nuclear power plant in this paper. A self-adapting multi-complex-shape algorithm has been developed and coupled with the thermal mathematical model of the moisture separator reheater, written in C#. The steady-state thermal mathematical model of moisture separator reheater is used to estimate the weight of moisture separator reheater according to the variation of a given number of structural and operation parameters. Then, the thermal mathematical model coupled with the self-adapting multi-complex-shape algorithm permits a set of best structural and operation parameters of the moisture separator reheater to be determined. The results clearly show that there is plenty of potential to improve the design of moisture separator reheater, while satisfying the structural and performance constraints. The results can also help both designers and operators to make a more convenient selection of the structural and operation parameters of moisture separator reheater.

Study on the Steady State Thermal Circuit Model of 10kV Three-Core Cable Based on the Shape Factor Method

The core of the 10kV three-core cable is in the shape of a trefoil. Not all the radial direction of the actual heat transfer characteristics are the same. The finite element method serve as the three core cable temperature field research method in this text, in order to analyze the internal temperature distribution of three core cable, establish a steady state thermal circuit model in accordance with the characteristics of heat transfer from the cable conductor to the surface in the three-core cable , give the calculation of conductor temperature algorithm, and calculate the various parameters in the model.

Triassic warm subduction in northeastTurkey: Evidence from theAğvanis metamorphic rocks

AbstractWithin theTethyan realm, data for the subduction history of thePermo–TriassicTethys in the form of accretionary complexes are scarce, coming mainly from northwestTurkey andTibet. Herein we present field geological, petrological and geochronological data on aTriassic accretionary complex, the Ağvanis metamorphic rocks, from northeastTurkey. TheAğvanis metamorphic rocks form aSSE–NNWtrending lozenge‐shaped horst, ∼20 km long and ∼6 km across, bounded by the strands of the activeNorthAnatolianFault close to the collision zone between theEasternPontides and theMenderes–TaurusBlock. The rocks consist mainly of greenschist‐ to epidote‐amphibolite‐facies metabasite, phyllite, marble and minor metachert and serpentinite, interpreted as a metamorphic accretionary complex based on the oceanic rock types and ocean island basaltic, mid‐ocean ridge basaltic and island‐arc tholeiitic affinities of the metabasites. This rock assemblage was intruded by stocks and dikes ofEarlyEocene quartz diorite, leucogranodiorite and dacite porphyry. Metamorphic conditions are estimated to be 470–540°Cand ∼0.60–0.90 GPa.Stepwise40Ar/39Ar dating of phengite–muscovite separates sampled outside the contact metamorphic aureoles yielded steadily increasing age spectra with the highest incremental stage corresponding to age values ranging from ∼180 to 209 Ma, suggesting that the metamorphism occurred at ≥ 209 Ma. Thus, theAğvanis metamorphic rocks represent the vestiges of theLateTriassic or slightly older subduction in northeastTurkey. EstimatedP–Tconditions indicate higher temperatures than those predicted by steady state thermal models for average subduction zones, and can best be accounted for by a hot subduction zone, similar to the present‐dayCascadia. Contact metamorphic mineral assemblages around anEarlyEocene quartz diorite stock, on the other hand, suggest that the present‐day erosion level was at depths of ∼14 km during theEarlyEocene, indicative of reburial of the metamorphic rocks. Partial disturbance of white‐micaAr–Ar age spectra was probably caused by the reburial coupled with heat input by igneous activity, which is probably related to thrusting due to the continental collision betweenEasternPontides and theMenderes–TaurusBlock.

Influence of Temperature and Material Deposit on Material Removal Uniformity during Optical Pad Polishing

The effects of temperature and material deposit on workpiece material removal spatial uniformity during optical pad polishing are described. Round and square‐fused silica workpieces (25–265 mm in size) were polished on a polyurethane pad using ceria slurry under various conditions. Using a nonrotated workpiece on a rotating lap, elevated temperatures (as measured by IR imaging), due to frictional heating at the workpiece–lap interface, were observed having a largely radial symmetric profile (relative to the lap center) on both the workpiece and lap with a peak temperature corresponding to the workpiece center. A 3D steady‐state thermal model of the polishing process, which accounts for the frictional heating and effective heat transfer from various surfaces, quantitatively describes the observed thermal profiles. The temperature spatial uniformity, which affects the material removal spatial uniformity, can be significantly improved using a rotated workpiece and a specially designed compensating septum during polishing. Next, using a rotating workpiece and lap, the workpiece surface develops two types of mid‐range structure: (1) fine ripples (sub‐mm scale length) that run circumferentially with respect to the lap, which have been attributed to microscopic islands of slurry on the lap leading to radial material removal nonuniformities; and (2) a center depression (cm scale length) which has been attributed to nonlinear slurry & glass products buildup at a specific radial lap location. A polishing simulator model (called Surface Figure or SurF), which accounts for workpiece wear, pad wear, and now deposition on the pad, correctly simulates the preferential material deposit on the pad and the center depression structure developed on the workpiece. Strategies, such as time averaging through kinematics and diamond conditioning, for preventing both these nonuniformities are demonstrated.

Thermal conditions of the central Sinai Microplate inferred from new surface heat-flow values and continuous borehole temperature logging in central and southern Israel

This paper reports ten new surface heat-flow density (qs) values for central and southern Israel (central Sinai Microplate), whose crystalline crust and lithosphere formed as part of the Neoproterozoic Arabian-Nubian Shield. Heat flow was calculated in Mesozoic sediments using the classical approach of heat-flow determination by implementing in the analysis high-precision continuous temperature logs obtained in air- and/or water-filled boreholes. Thermal conductivity (TC) measured for a large suite of rock samples of lithotypes making up the sequence was assigned to temperature gradients in intervals for which the lithology was known. The heat-flow values obtained for different depth intervals in a borehole as well as the average values for the individual borehole locations cover a narrow range, attesting heat-conduction conditions. A steady-state thermal model along an E–W crustal cross section through the area shows that the observed systematic spatial distribution of the qs values, which range between 50 and 62mWm−2, can primarily be explained by variations in the thickness of the upper crust and in the ratio between sedimentary and crystalline rocks therein. Given the time lapse of thermal heat transfer through the lithosphere, the qs data monitor the crustal thermal conditions prior to rift- and plume-related lithospheric thermal perturbations that have started in the larger area ca. 30Ma ago. Observed and modeled qs display the best fit for a pre-Oligocene lithosphere–asthenosphere boundary (LAB) at ∼150km, which would be at the upper end of LAB depths determined from stable areas of the Arabian Shield (150–120km) not affected by the young, deep-seated thermal processes that have caused a further uprise of the LAB. Our data imply or predict that the surface heat flow of the Sinai Microplate generally tends to increase along N–S and W–E traverses, from ∼45–50mWm−2 to ∼55–60mWm−2. Surface heat flows on the order of 55–60mWm−2 may be common in the northern Arabian Shield, where it exhibits typical lithosphere structure and composition and is unaffected by young heating processes, compared to values of ≤45mWm−2 recently determined in the southern Arabian Plate for the Arabian Platform.

A three-dimensional steady state thermal fluid model of jumbo ingot casting during electron beam re-melting of Ti–6Al–4V

A 3-D coupled thermal-fluid model describing mass, momentum and energy transport within a Ti–6Al–4V rolling ingot cast in an (Electron Beam Cold Hearth Remelting) EBCHR process has been developed to describe steady state casting conditions. The model incorporates a number of the physical phenomena inherent to the industrial process, including a metal inlet in the center of one of the narrow faces, complex boundary conditions based on industrial practice, buoyancy driven flow within the liquid and flow attenuation using a Darcy momentum source term within the mushy zone. The model ignores turbulence in the liquid pool and Marangoni (surface tension) driven surface flows. The model has been validated against liquid pool depth and profile measurements made on an experimental casting seeded with insoluble dense markers and doped with dense alloy additions. Comparisons have also been made to video images taken of the top surface during casting. The results indicate that the model is able to quantitatively predict the steady state sump depth and profile and is able to qualitatively predict aspects of the top surface temperature distribution. The model has also been used to conduct a process heat balance and sensitivity analyses. The process heat balance conducted on the model domain indicates that at steady state the liquid metal inlet contributes 88% of the total power input, while the electron beam provides net 12% after accounting for radiation losses from the top surface; 62% of the heat is lost through the ingots sides and the balance is lost via bulk transport of sensible heat through the bottom of the domain. The results of the sensitivity analysis on pool depth indicate that casting rate has the largest effect followed by metal inlet superheat. The thermal, flow and pressure fields predicted by the steady state model serves as the initial conditions for a transient hot-top model, which is the subject of a forth-coming paper.

Numerical Analysis on Temperature Field of Electric Connectors

The steady-state thermal analysis models are established based on the thermal analysis of the Electric connectors. With the consideration to the internal heat conduction and the convection cooling, the three-dimensional solid model is imposed by the reasonable loads and boundary conditions and analyzed by ANSYS thermal analysis module. The numerical analysis is made on the temperature field of a certain type of Electric connectors at different environmental temperature and different working current. The simulation results are compared with the monitoring test data.

A Steady State Thermal and Material Balance Model for an Iron Making Blast Furnace and Its Validation with Operational Data

In view of scarcity and depletion in the quality of raw materials as well as stringent environmental regulations, judicious use of resource and adoption of optimal operating practices have become the prime concern in iron and steel industries. Real time forecasting and supervision of the process behavior is an important step in addressing these issues. As a part of the tool termed “Real Time Process Simulator (RTPS)”, containing several reduced order models for real time monitoring and prediction of the internal dynamics of iron making blast furnace, a mathematical model for material and thermal analysis has been developed, mainly to predict the top gas composition, raw material consumption and overall heat balance. The model predictions have been tested against actual plant data. The raceway adiabatic flame temperature has been calculated using data similar to that of an operating plant. The calculated heat distribution of the process has been presented in the form of a SHANKEY diagram. The RTPS, containing the present model has been implemented in an Indian integrated steel plant. Prior to implementation, the model has been tested and validated in the plant operational range with the help of a virtual platform.

Multi-Criteria Optimization in Friction Stir Welding Using a Thermal Model with Prescribed Material Flow

Friction stir welding (FSW) is an innovative solid-state joining process providing products with superior mechanical properties. It utilizes a rotating tool being submerged into the joint line and traversed while stirring the two pieces of metal together to form the weld. The temperature distribution in the weld zone, as a function of the heat generation, highly affects the evolution of the microstructure and the residual stresses, and also the performance of the weld. Therefore, thermal models play a crucial role in detailed analysis and improvement of this process. In this study, a three-dimensional steady state thermal model of FS welding of AA2024-T3 plates has been simulated. The effect of the tool rotation on the temperature distribution has been also taken into account. This thermal model has been integrated with the non-dominated sorting genetic algorithm (NSGA-II) to solve a common manufacturing problem having conflicting objectives, i.e., maximization of production rate and tool lifetime. The resulting multiple trade-off solutions are then investigated to unveil any design rules which have a strong potential in industrial use.

Impact of Reservoir Permeability on Flowing Sandface Temperatures: Dimensionless Analysis

Summary Layer flow contributions are increasingly being quantified through the analysis of measured sandface flowing temperatures. It is commonly known that the maximum temperature change is affected by the magnitude of the drawdown and the Joule-Thomson expansion coefficient of the fluid. Another parameter that strongly impacts layer sandface flowing temperatures is the layer permeability. Aside from determining the drawdown, the layer permeability also affects the ratio of heat transfer by convection to conduction within a reservoir. The impact of permeability can be represented by the Péclet number, which is a dimensionless quantity representing the ratio of heat transfer by convection to conduction. The Péclet number is directly proportional to reservoir permeability. Through dimensionless analysis, it will be shown that for a given drawdown (based on a dimensionless Joule-Thomson expansion coefficient JTD) the temperature change diminishes at low Péclet numbers and increases at high Péclet numbers. This implies that for low-permeability reservoirs such as shale gas or tight oil, the temperature changes will be minimal (less than 0.1ºF) despite the large drawdowns in many instances. Dimensionless analysis is performed for both steady-state and transient thermal models. Results from multilayer transient simulations illustrate the ability to identify contrasting permeability layers on the basis of the Péclet number effect.

Crustal manifestations of a hot transient pulse at 60°N beneath the Mid-Atlantic Ridge

Since its inception at 62Ma, mantle convective upwelling beneath Iceland has had a significant influence on Cenozoic vertical motions, magmatism and paleoceanography in the North Atlantic Ocean. Crucially, intersection of the Reykjanes Ridge with the Icelandic Plume provides us with a useful window into the transient activity of this plume. Here, the spreading ridge acts as a linear sampler of plume activity, which is recorded as a series of time-transgressive V-shaped ridges and troughs. We present the results of a detailed study of the spreading ridge close to 60°N, where the youngest V-shaped ridge of thickened oceanic crust is forming today. A combination of multibeam bathymetry and seismic reflection profiles, acquired along and across the ridge axis, is used to map the detailed pattern of volcanism and normal faulting. Along the ridge axis, the density of volcanic seamounts varies markedly, increasing by a factor of two between 59°N and 62°N. Within this zone, seismic imaging shows that there is enhanced acoustic scattering at the seabed. These observations are accompanied by a decrease in mean fault length from ∼12km to ∼6km. A 1960–2009 catalog of relocated teleseismic earthquake hypocenters indicates that there is a pronounced gap in seismicity between 59°N and 62°N where the cumulative moment release is two orders of magnitude smaller than that along adjacent ridge segments. A steady-state thermal model is used to show that a combination of increased melt generation and decreased hydrothermal circulation accounts for this suite of observations. The predicted decrease in the thickness of the brittle seismogenic layer is consistent with geochemical modeling of dredged basaltic samples, which require hotter asthenospheric material beneath the spreading axis. Thus, along-axis variation in melt supply caused by passage of a pulse of hot material modulates crustal accretion processes and rheological properties.

Heat transfer through cable insulation of Nb–Ti superconducting magnets operating in He II

The operation of Nb–Ti superconducting magnets in He II relies on superfluidity to overcome the severe thermal barrier represented by the cable electrical insulation. In wrapped cable insulations, like those used for the main magnets of the Large Hadron Collider (LHC) particle accelerator, the micro-channels network created by the insulation wrappings allows to efficiently transfer the heat deposited or generated in the cable to the He bath.In this paper, available experimental data of heat transfer through polyimide electrical insulation schemes are analyzed. A steady-state thermal model is developed to describe the insulation of the LHC main dipole magnets and the Enhanced Insulation proposed for the High Luminosity LHC upgrade (HL-LHC), according to the relevant geometric parameters. The model is based on the coupled mechanisms of heat transfer through the bulk of the dielectric insulation and through micro-channels between the insulation tapes.A good agreement is found between calculations and tests performed at different applied pressures and heating configurations. The model allows identifying the heat fluxes in the cable cross-section as well as the dimensions of the micro-channels. These dimensions are confirmed by microscope images of the two insulations schemes.

Geological 3-D model of the larger Altensalzwedel area, Germany, for temperature prognosis and reservoir simulation

In the framework of the German R&D programme CLEAN (CO2 Large-Scale Enhanced Gas Recovery in the Altmark Natural Gas Field), the geological structure of an area encompassing the Altensalzwedel sub-field and its surrounding was analysed in detail. A 3-D model was developed that contains the major geological formations and their general lithology including the natural gas reservoir (in the Permian Rotliegend), the immediate cap rock (Permian Zechstein) of the reservoir and its overburden. Based on this geological model, a 3-D steady-state thermal model was generated as part of a shared earth model. The parameterisation of the geological model layers with thermal rock properties is based on laboratory and well-log data. The model shows temperature changes in dependence of geological structure and of different rock thermal conductivity. The calculated surface heat flow is high (>80 mW m−2) for most of the area, which is in accordance to measured surface heat flow. Temperature on top of the Rotliegend reservoir is variable ranging from 110 to 150 °C. The quantification of temperature changes versus depth as well as laterally in the reservoir are valuable input data for modelling the dynamic processes of CO2 injection within CLEAN.

Comparison of PV Cell Temperature Estimation by Different Thermal Power Exchange Calculation Methods

A steady-state thermal model for calculate the temperature of a photovoltaic (PV) module has been developed for outdoor installation such as ground-mounted systems. The PV temperature is influenced by environmental variables such as: irradiance ambient temperature, intensity and direction of the wind, module design, orientation and mounting structure. As well as it is influenced by electrical parameters. In literature some single layer thermal balance consider only an overall heat transfer coefficient as a function of wind speed, neglecting the radiative thermal flux. In this paper, five thermal balance are compared and it is shown that the radiative term cannot be neglected, otherwise the PV temperature could be overestimated for low solar radiation intensity and it could be underestimated for high solar radiation intensity. For this reason, the percentage contribution of the heat exchanges, normalized as function of normal incoming solar radiation, are evaluated for wind speed within 1 m/s (natural convection).

On the thermal evolution of the mantle wedge at subduction zones

We use a 2-dimensional numerical geodynamic model to investigate the evolution of the mantle wedge at subduction zones over a period of 300Myr following the onset of subduction. A variety of parameterizations of the overriding plate, as well as plate subduction rates and mantle potential temperatures, are considered systematically. The average temperature in the mantle wedge within 120km of the trench is found to decrease substantially (up to ∼100°C) over this period, with the most rapid cooling occurring during the first 100Myr. The observed cooling is not spatially uniform, but rather is concentrated in the uppermost 50km of the mantle wedge, immediately beneath the overriding plate. Temperatures in the mantle wedge in the vicinity of arc volcanism decrease by as much as >200°C over the 300Myr period. This decrease in temperature results in a decrease in the portion of mantle wedge beneath the arc in which hydrous melting can occur, impacting both the distribution of melting within the wedge and likely the composition of erupted melts. The observed variations in temperatures in the subarc portion of the mantle wedge with time are significantly larger than the changes in temperature resulting from inclusion of radiogenic heat production in the overriding plate or a zone of partial coupling between the slab and mantle. The results suggest that the mantle wedge is warmer than predicted by steady state thermal models, which may account in part for the differences between the petrologically determined pressure and temperature of equilibration for arc magmas and predictions of the thermal structure of the mantle wedge obtained from steady state thermal models.

Thermal effect on the electroluminescence of InGaN/GaN multiquantum-well light-emitting devices

A steady-state thermal model is presented to investigate the temperature and injection-current dependence of the electroluminescence (EL) in InGaN/GaN multiquantum-well light-emitting devices. The important mechanisms for the carrier dynamics, including thermal emission, recapturing, radiative and nonradiative recombination, are taken into account in this model. From the measured EL spectra, it is found that the S-shaped temperature dependence of the peak energy disappears at a high injection-current level. The temperature-dependent emission energies of the EL spectra are calculated with this model. The band-filling effect and the heating effect are considered in our investigation of this phenomenon, and the simulation results are in fair agreement with the experimental data. It is observed that both the band-filling and heating effects influence the temperature dependence of the EL emission spectra of InGaN/GaN multiquantum-wells. Quantitative discussion reveals that the heating effect becomes more apparent when the device is working at high injection-currents.

Thermal modelling of a photovoltaic module under variable free convection conditions

A thermal model regarding a photovoltaic module has been developed and validated using experimental data. The aim of this study was to obtain the temperature field of a BP 585 F module mounted at different distances from a roof wall, as well as the temperature and velocity profiles of the air at the exit section between the panel and the wall. The influence of the mounting distance on the temperature and velocity values was also studied. The simulation is done by applying the Galerkin finite element method to the flow and energy equations, incorporating an implicit convective boundary condition. The results show a good accuracy of the model. ► A two-dimensional steady-state thermal model of a photovoltaic module is studied. ► The air flow in the channel formed by the module and the mounting wall is examined. ► Due to the radiation and convection two boundary layers are formed. ► Velocity and temperature profiles depend on the boundary layer interaction. ► Increasing channel width leads to unexpected shape of velocity and temperature.

Optoelectronic and thermal characteristics of GaN-based monolithic light emitting diode arrays

We investigated the optoelectronic and thermal characteristics of InGaN/GaN monolithic light emitting diode (LED) arrays operating at λ∼ 470 nm. The optical output power (Pout) and forward voltage (VF) were almost linearly increased with the number of LEDs for series arrays. In the case of parallel LED arrays, the maximum operating current was increased by increasing the number of devices, but the VF was kept almost constant. Around 235 mA, the maximum Pout of 55.6 mW was obtained for the 1 × 3 series LED array fabricated with a separation distance of 1000 µm, while the Pout was 20.4 mW for the 1 × 3 parallel LED array. From the measured light–current–voltage data, the maximum internal temperature (Tmax), i.e. a maximum value of internal temperature rise within the devices under operation, was theoretically determined using a three-dimensional steady-state thermal heat dissipation model based on the finite element method. Also, the temperature profiles were obtained for various separation distances and array sizes. At injection current of 220 mA, the Tmax was theoretically calculated as 325.6 K and 306.6 K for 1 × 3 series and parallel LED arrays with a 1000 µm separation distance, respectively. The Tmax was increased and decreased on decreasing the separation distance and substrate thickness, respectively, and its dependence on Tmax became more significant at higher injection current.

A steady state thermal duct model derived by fin-theory approach and applied on an unglazed solar collector

This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (1D) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler 1D analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no ‘or negligible’ temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the 1D isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); 1D heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition.

Thermal model and thermodynamic performance of molten salt cavity receiver

The design of a global steady-state thermal model of a 100 kWt molten salt cavity receiver was developed as part of the key project of the Ministry of Science and Technology of People's Republic of China (MOST). In the design process, the following factors were analyzed: receiver area, heat loss (convective, emissive, reflective and conductive), number of tubes in the receiver panel, tube diameter and receiver surface temperature. The model was also used to calculate the receiver performance of the Sandia National Laboratories' molten salt electric experiment (MSEE). In addition, the thermal performance of the designed molten salt cavity receiver is presented for a fixed outlet flow rate and a fixed output temperature.