Maximum Temperature Gradient Research Articles

Numerical Simulation of Heat Removal from a Window Slab Partition of a Radiative Coil Coating Oven

In this work, fluid flow and heat transfer performance of a radiative coil coating oven is numerically investigated. In the coil coating oven concept under consideration, porous radiant burners provide the required energy to evaporate the volatile species (solvents) from the applied coating and to promote curing reactions. To avoid the mixing between burners flue gas (with a non-negligible oxygen content) and evaporated (combustible) solvents in the oven (which could lead to a catastrophic oven failure), a semi-transparent window in between both atmospheres is applied. To ensure the window thermal stability during the oven operation, window cooling by wall jets is considered. Different turbulence models were compared against available wall jet heat transfer correlations to select the most suitable for three-dimensional (3D) numerical simulations. Convective heat transfer correlations purposefully developed were embedded in a one-dimensional (1D) window energy model for fast performance characterization, analysing the most influencing parameters—window radiative properties, thickness, inlet temperature and velocity of wall jets, and cooling strategy. The 1D window thermal performance is compared with literature and 3D results considering the full coil coating oven, providing satisfactory confidence on the developed strategy. The 1D model is used for an optimisation study to find the minimum energy consumption while ensuring the safety requirements (maximum window temperature and thermal gradient) are met.

Analysing thermal regime and transient by using numerical modelling for solid oxide electrolyser aided by solar radiation

The present paper focuses on analysing the thermal transient and regime for a Solid Oxide Electrolyser (SOE) system by means of the development of a numerical algorithm at high accuracy, built up ad hoc and run in a proper calculation environment. In particular, the algorithm also considers that the supply of thermal power takes place through a concentrated solar source, so it is designed also to receive the data library relating to solar radiation. The calculations are centred on the evaluation of the concentration factor to proceed with the dimensioning of the heat source and its management in order to guarantee the thermal power supply. The thermal transient model receives the SOE thermo-electrochemical model as input to integrate it into the larger thermal process of the overall structure, accounting for the effective thermal dispersion occurring to the external environment.The algorithm consents the calculation of the temperature profile, besides assessing the contributions of thermal power such as that required, disposed and possibly recovered by the system, and that can possibly be integrated to sustain the system itself. A specific query is dedicated to the switch-on and switch-off phase for which the device must comply with certain warnings, referring to the temperature limits and temperature gradient constraints.The thermal analyses are set as a function of the electro-thermal and feeding parameters of the SOE as voltage, electric current administered and cathodic mixture of H2O/H2.An application on a real case study was effected at the SOE test-station of “Fuel Cell and Hydrogen” Lab at the Department of Mechanical, Energy and Management Engineering of the University of Calabria, in Cosenza, Italy.The three possible exercises of functioning of SOE working regime, SOE start-up, SOE shut-down are analysed.The assessment about the start-up and shut-down phases reveals that these delicate phases have to be managed smartly time by time to observe the limitation on maximum temperature and temperature gradient.

Preparation of Pt/Ce–Zr–Y mixed oxide/anodized aluminium oxide catalysts for hydrogen passive autocatalytic recombination

The use of a Pt-based catalyst was evaluated for autocatalytic hydrogen recombination. The Pt was supported on a mixture of Ce-, Zr- and Y-oxides (CZY) to yield nanosized Pt particles. The Pt/CZY/AAO catalyst was then prepared by the spray-deposition of the Pt/CZY intermediate onto an anodized aluminium oxide (AAO) layer on a metallic aluminum core. The Pt/CZY/AAO catalyst (3 × 1 cm) was evaluated for hydrogen combustion (1–8 vol% hydrogen in the air) in a recombiner section testing station. The thermal distribution throughout the catalyst surface was investigated using an infrared camera. The maximum temperature gradient (ΔT) for the examined hydrogen concentrations did not exceed 36 °C. The Pt/CZY/AAO catalyst was also evaluated for prolonged hydrogen combustion duration to assess its durability. An average combustion temperature of 239.0 ± 10.0 °C was maintained for 53 days of catalytic hydrogen combustion, suggesting that there was limited, or no, catalyst deactivation. Finally, a Pt/CZY/AAO catalytic plate (14.0 × 4.5 cm) was prepared to investigate the thermal distribution. An average surface temperature of 212.5 °C and a maximum ΔT of 5.4 °C was obtained throughout the catalyst surface at a 3 vol% hydrogen concentration. • Reactive Pt/CZY/AAO catalysts were prepared for catalytic hydrogen combustion. • Catalysts contained an aluminum core to rapidly dissipate reaction heat. • Thermal conductivity ensured temperature gradients of <36 °C at 1–8 vol% hydrogen. • No decrease in catalytic activity after 53 days of hydrogen combustion at 239 °C. • Catalysts suitable for safe PAR applications.

Microscopic liberation mechanisms of oolitic iron ore under microwave irradiation and optimization of irradiation parameters

Microwave liberation is a promising method for beneficiation of oolitic hematite but has not been used in industrial production. This is because the specific microwave energy requirements for iron ore applications is prohibitively high and there is a lack of quantitative references for microwave irradiation parameters. The cracking process of oolitic hematite under microwave irradiation is simulated using the discrete element method. Temperature field, force chain and cracking development during microwave irradiation are analysed, accordingly, the microscopic mechanisms are discussed. The results indicate that: the hematite ring is under compression and the quartz ring is under tension along the radius under microwave irradiation; radial cracking initiate on the edge prior to circular cracking along mineral boundary; location of circular cracks corresponds well to the position where the maximum temperature gradient occur; there is an optimal power density under given energy consumption and an optimal irradiation time under given power density for microwave liberation.

Coordinated control approach for load following operation of SOFC-GT hybrid system

In order to achieve the fast load following and safe transient operation of Solid Oxide Fuel Cell-Gas Turbine hybrid system, a novel control approach by combining the multi control loops with the coordinated protection loops is proposed in this work. The coordinated protection loops can adjust the transient behavior of operation parameters on-line to avoid the undesired operation faults, such as compressor surge, reformer carbon deposition, fuel cell thermal crack and turbine blade overheat. Meanwhile, the fuzzy logic theory is introduced to self-tuning the control parameters to meet the control requirements of the nonlinear time varying system. The analysis in system transient behavior during load step changes operation indicates that the present work can realize parameters decoupling and eliminate the instability of SOFC-GT. The proposed control strategy can reduce the SOFC current overshoot by 10.8% during the load step-down operation, meanwhile, this reduces the transient maximum temperature changing rate by almost 47.7%. In addition, by changing the transient behavior of air and fuel flow, the proposed control strategy can reduce the temperature overshoot by 1.16% in load step-up operation. This leads to the transient maximum temperature gradient is decreased by 0.18K/cm.

Investigation on thermal performance of water-cooled Li-ion cell and module with tree-shaped channel cold plate

The performance of lithium-ion batteries shows high susceptibility to temperature. A well-designed thermal management system can improve the service life and safety of the battery pack. In this study, we developed a novel cooling plate with the inherent advantages of low flow resistance. To highlight the performance advantages of the cooling plate, it was compared with a previous tree-shaped cooling plate as well as the U-turn cooling plate used by Chevrolet. Furthermore, combining Kriging interpolation with Latin hypercube sampling test, three prediction models of pressure drop, maximum temperature, and standard deviation of the surface temperature of the novel cooling plate were established to investigate the influence of structural parameters and boundary conditions on the performance of the novel cooling plate. To verify the accuracy of the prediction models, 10 sets of test combinations were constructed through the uniform test design. Finally, a prismatic battery module was created using the battery design studio (BDS) and STAR-CCM+. The effect of cooling water temperature and battery discharge rate on the thermal performance of the battery module was investigated. The results indicated that the novel cooling plate exhibited slightly better heat dissipation with only a 1/3 pressure drop than the other two cooling plates. The Kriging models were in good agreement with the simulation results, which demonstrated the excellent prediction abilities of the Kriging models. The lower temperature but larger temperature difference was achieved in the battery module by reducing the cooling water temperature. The novel cooling plate could maintain the maximum temperature of the battery module, maximum cell-to-cell temperature difference, and maximum temperature gradient within the cell below 40 °C, 1 °C, and 5 °C, respectively.

Modeling and control-oriented thermal safety analysis for mode switching process of reversible solid oxide cell system

A reversible solid oxide cell (rSOC) system can balance the surplus and shortage of electricity generated from renewable energy grid by working either in energy conversion or in storage mode. A dynamic model of the rSOC system was developed and validated against experimental data. It can be used to determine the dynamic thermal characteristics during mode switching. This work focuses on the influence of different operating parameters on the temperature distribution in the rSOC stack along the gas flow direction in the system environment. The extremum of local temperature gradient in the dynamic process is proposed for the first time, and it hardly changes when adjusting air excess ratio (AR) and fuel utilization (FU). In addition, the results show that the maximum PEN temperature (MaxT_PEN) increases with the decrease of AR in the transients, but FU has little effect on the local MaxT_PEN. AR and FU affect the MaxT_PEN (Compared with FU, AR is more significant) and the maximum temperature gradient (MaxT_grad) in steady-state, but the control current does not. The proposed control currents significantly decrease the MaxT_PEN and MaxT_grad in the transient process, and the ramp current works better than the multi-step current. Overall, this work identified the effects of operating parameters on the thermal characteristics of the rSOC stack in switching from electrolysis to fuel cell mode under the system environment. It guides the development of the thermal management strategy of the rSOC system.

Computational study for the optimization of Ranque-Hilsch vortex tube with the variation of number of inlet chamber and distance between the chambers

The purpose of the present study is to analyse the improvement in the performance of vortex tubes numerically. The air is taken as the working fluid in the compressible, axisymmetric 3-D, turbulent flow, and steady-state vortex tube. The standard k-ɛ turbulent model has been used for flow simulation in ANSYS FLUENT software with different pressure at the inlet and validated with experimental outcomes. It is found that there is an increment of 9.09 % in the cold temperature gradient with three inlet chambers as compared to single chamber. When inlet chamber numbers change from three to four, a decrease in the cold temperature gradient is recorded. When the distance between the inlet chamber increases from 8 mm to 32 mm, there is a decrease in the vortex tube’s cold temperature gradient. Therefore, it indicates that the optimum number of inlet chambers to obtain maximum cold temperature gradient, i.e., minimum cold exit temperature for the given specification of the vortex tube essential to have three inlet chambers, and the optimum distance between the inlet chambers 8 mm, is recommended.

Temperatures and gradients in concrete Bridges: Experimental, finite element analysis and design

Aiming to introduce a simplified flexible design model for thermal actions in concrete bridge superstructures, experimental and finite element works were carried out in this study. From an experimental concrete box-girder segment, concrete temperature, solar radiation, air temperature and wind speed records for a complete one-year cycle were recorded and utilized. In addition, a thermal finite element model was conducted and verified, which was then used to conduct required parametric studies. Finally, the verified finite element model was used together with long-term climate history (from 1960 to 2013) of 10 cities in Turkey to propose the thermal actions' design models and procedure. Both positive and negative vertical temperature gradient models were introduced in terms of the top surface maximum temperature gradient, which is related to the solar radiation history of the region. In addition, simplified correlations and design procedure were suggested to evaluate the maximum and minimum mean temperatures of concrete bridges using the long-term maximum and minimum air temperatures.

Thermal Stress Analysis of Jet Impingement Cooling of a Solid Block

The conjugate heat transfer and the generated thermal stresses of jet impingement cooling of a solid block are considered for numerical investigation. A rectangular block is heated from the bottom surface and is cooled by impinging air on its top surface. The selected materials of the block are: Polyethylene, Titanium alloy, Aluminum alloy, and Carbon steel. The governing parameters in the present study are Reynolds number, temperature of the bottom surface of the block, material, and thickness of the block. It is found that the average Biot number for the Aluminum alloy block is the minimum. The average values of Bi are increased with the increase of the Reynolds number of the jet, the thickness of the block or the heated surface temperature. The maximum equivalent stress is generated at the maximum temperature gradient under the stagnation point of the jet flow. The generated equivalent stress increased by increasing either the heated surface temperature or the thickness of the block. The maximum total deformation is found in the Polyethylene block and the minimum occurred for the Titanium Alloy block. The results show negligible effects of Reynolds number on the equivalent stresses and total deformation of the block.

Study on extremely high temperature gradient at entrance of solid oxide fuel cell by preheating model

&lt;sec&gt;The degradation or failure caused by thermal stress is a serious problem for solid oxide fuel cell (SOFC), especially in preheating process. The common working temperature for SOFC is more than 700 ℃, so it should be preheated to startup temperature (e.g. 600 ℃). The thermal stress induced by temperature gradient in SOFC is a crucial factor that results in the degradation or failure of SOFC, therefore there are many studies on the optimization of preheating process.&lt;/sec&gt;&lt;sec&gt;Numerical model is an important tool in the study of SOFC preheating process, however there exists a serious discrepancy between the model results and experimental results. The numerical model always gives a very high temperature gradient in the SOFC which can result in SOFC crack according to the material permissible stress, and this result disagrees with the practical experimental result. In this paper, a hot gas preheating model of SOFC is developed and the model is verified by comparing with model results from the literature. Then, the location of maximum temperature gradient and distribution of temperature gradient in the SOFC are studied by this model, and the extremely high temperature gradient at entrance is analyzed. Some conclusions are given below.&lt;/sec&gt;&lt;sec&gt;1) The maximum temperature gradient is always located at the edge of SOFC nearby the gas entrance. The variation of temperature rise rate and velocity of hot gas show negligible effect on the position of maximum temperature gradient in the gas flow direction. For single channel preheating method, the maximum temperature gradient is at the gas entrance. For the dual channel preheating method, the maximum temperature gradient is always at the cathode gas entrance whatever gas feeding way is co-flow or counter-flow, because the thermal conductivity of cathode is lowest.&lt;/sec&gt;&lt;sec&gt;2) There is an extremely high temperature gradient at the gas entrance, and the temperature gradient sharply decreases along the gas flowing direction at the small entrance section. The extremely high temperature gradient may result from the uniform inlet temperature and velocity set in the model, and the entrance effect can greatly enhance the heat transfer between gas and SOFC component due to the large difference in velocity and temperature at the entrance section.&lt;/sec&gt;&lt;sec&gt;3) The entrance extension of gas channel can give rise to a fully developed velocity distribution and reduce the temperature gradient at SOFC entrance, however, there is always a high temperature gradient at the entrance section of SOFC due to the uniform inlet gas temperature. Therefore, the maximum temperature gradient given by numerical model as a criterion of SOFC safety can overestimate the thermal stress, and the distribution of temperature gradient in SOFC should be analyzed together to optimize the preheating process.&lt;/sec&gt;

Дослідження термічної підготовки ковшів

The purpose of the work is to develop a computer model of ladle heating with an open torch on a drying and high-temperature heating installation to control the thermal preparation process. The task of managing ladle drying and high-temperature heating installations (USVR) is to implement their operating modes, which ensure obtaining the specified temperature profile of the lining layers of steel castings with minimal fuel consumption. The task of controlling by drying and high-temperature heating unit (SHHS) is to implement their operating modes that provide a given temperature profile of steel pouring ladle lining layers with minimal fuel consumption. Since modern technical means of control do not allow obtaining relevant information about the temperature field of the lining of the walls and bottom of the ladle, it is necessary to create a predictive model of its heating by an open torch at the SHHS. A 68-ton rammed steel-pouring ladle KС-68 was chosen as the object of study. According to the research data, the shape and dimensions of the open torch were evaluated at OCC PrJSC “Evraz- Dnipro Metallurgical Plant”. A digital camera recorded the torch at the burner outlet at a natural gas flow rate of 50 m3/h, which corresponds to the standard mode of drying and warming up the ladle. For modeling purposes, the resulting torch shape was approximated by two truncated cones. Determination of the parameters of convective-radiant heat transfer in the “torch – cover – wall – ladle bottom” system was carried out taking into account the temperature of the torch, the thermophysical properties of the lining materials, as well as the irradiance coefficients and the emissivity of the surfaces. The calculation of the temperature field in the lining of the wall and bottom of the ladle was carried out by the finite element method implemented in the ANSYS package. Based on the simulation, a change in the temperature field of the ladle lining was obtained during its heating at the SHHS with an open torch for 6 hours, which corresponds to the current technology. An analysis of the dynamics of the temperature field of the ladle lining obtained as a result of modeling indicates that when it is heated by an open torch at a drying and high-temperature heating unit, thermal stresses do not occur, which are dangerous from the point of view of cracking in the layers of refractory materials. The maximum temperature gradient in the wall is 10 °С/mm, and at the bottom – 6 °С/mm. It has been established that the working surface of the lining warms up sufficiently to avoid thermal shock when steel is poured into the ladle. The results of the research can be useful for optimizing the process of thermal preparing steel pouring ladles.

Temperature Field of Concrete‐Filled Steel Tubular Arch Bridges and Its Application

This study aimed to reveal the evolution rule and influence mechanism of temperature field and its effect of long‐span concrete‐filled steel tubular arch bridges in a plateau area. The temperature field and its effect of large‐diameter concrete‐filled steel tubular arch bridges under strong radiation, hydration heat, and large temperature difference were studied using the ANSYS transient thermal analysis method. The optimization method on transverse perfusion sequence and perfusion‐time interval considering temperature effect was proposed based on stress influence line, equivalent age theory, and energy method. Results showed that the temperature field along the radial direction distributes as a symmetrical three‐segment polyline with an influence depth of D/4 under ambient temperature and hydration heat, and it distributes as an asymmetric three‐segment polyline with an influence depth of D/8 under solar radiation, ambient temperature, and hydration heat, and this is smaller than the specified value of D/4. The maximum temperature on the sunny side is about 20°C higher than that on the shaded side. The influence of solar radiation absorption coefficient and ambient temperature on the maximum temperature gradient and maximum stress is greater than that of wind speed. The optimization method on transverse perfusion sequence and perfusion‐time interval considering temperature effect proposed in this paper is reasonable and convenient for engineering applications.

Thermal and Computational Fluid Dynamics (CFD) Analysis of a Modified Two Stroke Spark Ignition Engine Block

An engine block is the main supporting structure for other components of the engine. Poor heat dissipation of the engine block causes excessive thermal expansion and frictional wearing of the engine components and makes engine oil to lose its lubricating power. Therefore, there is a need to modify the design of the engine block in order to improve its effectiveness. In this analysis, a two stroke spark ignition engine block was initially used as a reference model for the development of the modified model. Solidworks (2013) simulation software was used to model and conduct a thermal and computational fluid dynamics (CFD) analysis on the two models. The thermal analysis results shows that, the maximum temperature gradient and heat flux obtained during the steady state and transient thermal analysis were, 2.237×107 K/m, 3.6817×104 K/m, and 1.066×107 W/m2, 1.661×106 W/m2 for the reference model, while 1.771×106 K/m, 4.913×104 K/m, and 7.970×107 W/m2, 2.211×106 W/m2 for the modified model respectively. The results shows that the modified model has an improved heat dissipation rate than the reference model. The CFD analysis shows that, the reference model is subjected to high pressure and air resistance than the modified model. This increases the drag force acting on the reference model. While the modified model has high air flow velocity round the engine block, than the reference model. This is due to fins modification of the modified model. This makes the engine block model to have low air restriction. It is hereby recommended that further validation should be carried out to ascertain the effectiveness of the modified model. The performance of the modified model can also be improved by converting its fins into triangular fins geometry.

Development and application of 3D pool-type sodium cooled fast reactor system analysis program

Sodium cooled fast reactor (SFR) is the most comprehensively studied and the most extensively operated reactor-type in the 4th generation of nuclear power plants. One of the key points of the transient analysis in pool-type SFR is refined analysis of the transient thermal-hydraulic characteristics of the 3D sodium pool. In this paper, according to the characteristics of pool-type SFR, a three-dimensional (3D) system analysis model is developed. The difficulties involved: establishment of the basic 3D mathematical model, method for processing 3D momentum convection terms, accurate simulation of the position 1D pipe and 3D space. On this basis, the 3D transient analysis program NUSOL-LMR-3D for pool-type SFR is independently developed. Then, the 3D system model is fully verified with the MONJU thermal stratification experiment and the EBR-II transient experiment. Subsequently, NUSOL-LMR-3D program was applied to the 3D transient safety analysis of the TBO accident of (CEFR). The results show that NUSOL-LMR-3D program can accurately simulate the accident process, and it is pointed out that there is obvious thermal stratification in the hot sodium pool around 50s after the accident. The temperature gradient on the thermal interface is relatively large, which may result in a large thermal stress on the internal structure of the pool. Besides, the location with maximum temperature gradient of the inner barrel wall and central measuring column were suggested through analyzing the temperature field of the inner hot pool. The most attention should be paid to the area of the inner barrel wall axial position of 0.45 m–0.65 m and the central measuring column axial position of 0.65 m–0.95 m. This study provides an in-depth analysis of the three-dimensional transient thermal-hydraulic characteristics of the pool-type SFR, which solves the problem of rapid and refined analysis of the 3D sodium pool and provides a reference basis for the design of fast reactor systems.

Conjugate heat transfer in the mode of thermal gravitational-capillary convection in the model of a fuel tank, after a sudden heating of the sidewall

The evolution of unsteady gravitational-capillary convection in a layer of ethyl alcohol with a free surface after sudden electric heating of one of the vertical walls of a rectangular cavity was investigated numerically. The effect of the incoming flow of hot liquid on the time evolution of the temperature field on the opposite thin metal wall of the cavity was investigated. The calculations were carried out by the finite element method in the conjugate two-dimensional formulation with the Prandtl number Pr = 16, and the range of Grashof numbers determined by the heat flux density, 33·103 ≤ Gr ≤ 28·106. It is shown that the maximum local temperature gradients occur on the wall near the liquid-gas interface.

Исследование тепловложения при сварке труб различными методами и способами

The article presents the results of the experimental investigations on studying the effect of heat input on the metal-physical properties of the welded joints of pipes with the diameters of 114–406 mm and the wall thicknesses of 9–21 mm from steels X42–X46 according to API 5L standard with various welding technologies. The analysis is given concerning the thermal welding cycles using technologies of manual arc welding with electrodes with a basic and cellulose type of coating, as well as automatic welding technology under a flux layer. The parameters of thermal welding cycles were measured using 12-channel recorder, which received a signal from chromel-alumel thermocouples stamped near the weld. The data obtained was processed in accordance with the program, which included an assessment of the maximum temperatures and temperature gradients, a study of the kinetics of the accumulation of thermal effects in the near-seam zone, and the zone of thermal influence, as well as an assessment of the residence time of the welded joint metal at a temperature above 600 °C. The analysis of thermal cycles using various welding techniques and methods showed that the parameters of thermal welding cycles largely determine the metal-physical properties of the weld metal and the zones of thermal influence, the possibility of trouble-free and long-lasting operation of the structure at various ambient temperatures. It is shown that the choice of the optimal thermal welding cycle allows to obtain high mechanical properties of metal in all the areas of the welded joint, and, also, ensures the production of weld metal with high metallurgical quality, which increases the working condition of the pipeline and the safety of maintenance personnel during its operation. The presented results of the study can serve as a basis for the development of additional requirements for welding technology of steels of various strengths considering the maintenance of the working condition of the structure as a whole.

Experimental and numerical analysis of air temperature uniformity in occupied zone under stratum ventilation for heating mode

In warm air heating systems, a good indoor air temperature distribution can provide a comfortable indoor environment and reduce energy consumption. Few studies were conducted for the uniformity of air temperature distributions under stratum ventilation (SV) for heating. In this study, the horizontal and vertical air temperature uniformities in an occupied zone were evaluated under SV heating mode. Different indoor thermal environments were created using both experiments and computational fluid dynamics (CFD) simulations. Results showed that the horizontal air temperature uniformity is generally inferior to the vertical direction. Based on the experimental and simulation cases, the maximum horizontal and vertical air temperature gradient is 3.46 °C/m and 2.44 °C/m, respectively. The uniformity of the air temperature distribution can be significantly affected by supply air parameters. The maximum extremum air temperature difference is 6.26 °C at the height of 0.6 m. However, it can be reduced to less than 0.62 °C by varying the supply air velocity, temperature and angle. Appropriate supply air parameters can provide an energy utilization coefficient (EUC) higher than one, showing the potentials of energy saving. A grey relational analysis revealed that the relational degree of the supply air velocity and temperature on the air temperature uniformity is relatively high, followed by the outdoor temperature and then supply vane angle. The results derived from this study can contribute to better understand the characteristics of indoor air temperature distribution under SV heating mode.

Model development and transient analysis of thermal stratification phenomenon in pool-type sodium-cooled fast reactors

Thermal stratification of pool-type SFR under transient accident conditions has a very significant impact on the performance of key components of the primary loop and the establishment of natural circulation of the residual heat removal system. In this paper, combined with the mechanism of thermal stratification, a three-dimensional (3-D) system analysis model is developed, which takes into account the energy source model, the 3-D convection model and the large space inlet-effect model. Based on the model development, the accuracy of 3-D thermal–hydraulic analysis model and the capability of thermal stratification analysis for SFR were fully verified. The validation results show that the method established in this paper takes into account accuracy and calculation efficiency. It can greatly reduce the amount of numerical grid, take up very little computing resources and greatly improves analyzing efficiency. And it can accurately simulate the thermal stratification phenomenon in the sodium pool. At the same time, the location with maximum temperature gradient of the inner barrel wall can be suggested in the process of thermal stratification. Furthermore, this study provides an important analytical method for the transient safety analysis of SFR, and has a great academic value and engineering significance.

Temperature Gradient Control of the Solid Oxide Fuel Cell under Variable Load.

Nowadays, the temperature gradient is considered as one of the most important parameters which impact the performance of the solid oxide fuel cell (SOFC). In this paper, a control strategy based on an input–output feedback linearization technology is derived for controlling the maximum temperature gradient within the anode fuel flow channel at the desired value. For the controller design, the temperature dynamic model is proposed and simplified to a control-oriented multi-input and multioutput nonlinear dynamic model. Then, this paper presents an input–output feedback linearization controller to realize the control objective by adjusting the cathode input air flow. Finally, the simulation results are given to demonstrate the accuracy of the proposed model in reflecting the temperature dynamic characteristics. Moreover, the compound controller is added for simulation as a comparison, which shows that the proposed controller is equipped with better effectiveness and efficiency in the presence of external disturbances.