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Three-phase current unbalance is a common winding fault of the motor, which will bring local overheating, cause security risks and economic losses, accurate temperature rise calculation and thermal flux characteristics analysis of the motor working in three-phase current unbalance are necessary and challenging. However, little research has been conducted on the thermal characteristics and analysis methods for the permanent magnet synchronous linear motor (PMSLM) working in three-phase current unbalance. To address this problem, a multilayer composite flat wall model contained heat source of the primary is proposed firstly to analysis the heat transfer characteristics of the PMSLM caused by three-phase current unbalance qualitatively. Then, the heat transfer and temperature distribution characteristics of the PMSLM are obtained by calculating the fluid-thermal coupling model of the PMSLM directly. What's more, the effect of current grade on heat transfer is analyzed by comparing the heat transfer characteristics of the PMSLM working in four different three-phase current balance cases. Finally, the qualitative analysis and fluid-thermal analysis results are verified experimentally with a PMSLM adopting four different three-phase current unbalance conditions. Thermal analysis of the PMSLM working in three-phase current unbalance makes it is possible to prevent local heat accumulation and avoid unexpected interruptions for the redundant motor system and the fault tolerant motor system. • A multilayer composite flat wall model contained heat source of the primary is proposed in this paper. Based on this, the heat flux and average temperature of the primary that with three-phase unbalanced current can be analyzed. The temperature distribution characteristics and thermal flux transfer of a PMSLM working in three-phase current unbalanced fault is calculated by establishing the simplified fluid model and coupling fluid-thermal field model, which is useful for analyzing the thermal characteristics of the PMSLM detailedly. Besides, the thermal characteristics of the PMSLM working in 4 different three-phase current balance cases are compared. This work can be used to analysis the thermal characteristics of the PMSLM changing with the excited unbalanced current density. [ABSTRACT FROM AUTHOR]

In this paper, a new approach of the Hot Disc method is presented based on the explicit calculation of the average temperature of a constant heat source on a semi-infinite medium. The Transient Plane Source (TPS) technique developed in the 90 uses a linear regression between the evolution of temperature of the source and a function. This function needs to perform an integral whose calculation can be complex and slow. Therefore, we propose a new approach based on the explicit analytical expression of the average temperature of the heat source to obtain simultaneously by inverse method, the thermal characteristics of the medium, i.e. the conductivity and diffusivity. Besides, we propose to estimate simultaneously the experimental unknown parameters, namely the correction time due to the sensor and the establishment of micro constriction phenomena and the thermal contact resistance between the sensor and the material to be characterized. This approach also makes explicit, for the first time, the sensitivities of the problem and thus to make a complete and accurate sensitivity analysis based on their analytical expressions. Thus, an uncertainty estimation analysis of the parameter estimation using a stochastic approach is carried out to predict confidence intervals on each parameter as a function of the measurement noise. A Monte Carlo method confirms the obtained results. An optimization of the experimental parameters is then conducted based on the minimization of the confidence interval of the estimated parameters. • A new approach of the TPS method is presented. • An explicit analytical calculation is used to perform the identification of the thermal conductivity and diffusivity. • A fully analytical sensitivity analysis is conducted. • A stochastic approach is carried out to predict confidence intervals on each parameter as a function of the measurement noise. [ABSTRACT FROM AUTHOR]

The Korea fourth-generation storage ring (Korea-4GSR) has a low electron beam emittance of 60 p.m.-rad, and provides a photon beam that is 100 times brighter and 100 times more coherent than the third-generation Pohang Light Source (PLS-II). However, the new source imposes a higher heat load on beamline optics. In particular, the first mirror (M1), which receives the broad-bandwidth white beam will be distorted by the thermal load from X-ray beam and the heat bump will degrade the beam quality. For the thermal analysis of M1, a method is developed to solve the thermal deformation with temperature gradient and absorbed power density. To implement the method in the analysis of heat load effect on M1, a benchmark study was performed on beamline 8A at PLS-II. In this paper, we describe the thermal analysis of M1 in Korea-4GSR after verifying our simulation method in a benchmark study. [ABSTRACT FROM AUTHOR]

Thermal radiation is a significant mode of energy transmission besides conduction and convection in most combustion systems. Accurate treatment of thermal radiation is a crucial element for predicting the flame structure and pollutant formation. However, thermal radiation to fuel droplet evaporation is often neglected in the numerical simulations of two-phase spray combustion systems. In this paper, computational analysis on the thermal radiation to evaporation and combustion of fuel droplets in two-phase spray combustion is conducted. The influence of flame radiation on droplet evaporation and combustion is studied by adding radiation source term to the energy equation describing droplet evaporation process. Radiation transfer equation is solved, in which the radiation of CO 2 , H 2 O and soot is imposed to consider radiation effect of the flame. The partially premixed combustion model is employed, in which radiation heat transfer between droplet and ambient gases is taken into account. A reduced chemical reaction mechanism for n-heptane consisting of 76 species and 349 reactions is used. Four different numerical setups have been used and compared, and the simulation results coincide with the experiment data in terms of spray statistics and flame shapes. The peak flame temperature increases by 28 K when the radiative heat source term in the evaporation process is considered. The droplet evaporation is significantly enhanced by thermal radiation, leading to a promotion of 34.8% in C 7 H 16 concentration in the center region of combustor. The concentration of combustion products, such as H 2 O and CO 2 , increases by 13.2% in the reaction region. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of separation distance on the flame appearance and radiation heat flux of medium-scale pool fires dominated by radiation. A series of experiments were conducted on two adjacent heptane pool fires with diameters of 20 cm, 40 cm and 60 cm at separation distances ranging from 0 to 60 cm. According to experimental results, flame height and flame inclination angle increase monotonously with the increase of pool diameter. As separation distance increases, flame height increases first and decreases gradually for 3 different sized pool fires. However, the variation law of flame inclination angle with separation distance varies with pool diameter. The normalized flame height (H f / D) is found to increase exponentially with the dimensionless heat release rate (Q *) with an exponent of 0.71. The radiative heat flux at the center of the pool surface peaks at the critical separation distance of flame merging, which results from increased flame emissivity and view factor. Based on thermal analysis, a model to predict the radiative heat flux on the fuel surface is developed. The predicted radiative heat fluxes quantitatively match the experimental results but with 20% overvalued, due to the neglection of radiation blockage effect of cool fuel vapors zone and soot. The blockage effect is more pronounced for the merging pool fires with a diameter of 60 cm. • Experiments of medium-scale double heptane pool fires were conducted. • Flame morphological characteristics of pool fire were quantified. • A unified model was established to predict the radiative heat flux delivered to the pool surface at different conditions. • Radiation blockage due to fuel vapors and soot was quantitively analyzed. [ABSTRACT FROM AUTHOR]

The thermal analysis of power cables to improve their lifetime and reliability is essential. Also, the current harmonics intensify the excessive heat condition of power cables. Although several research works have been introduced for harmonic-based thermal analysis of power cables, there is a research gap about developing a thermal analysis of power cable focusing on the even current harmonics. This paper tries to such a research gap by proposing a new harmonic-based thermal analysis of electric arc furnace (EAF) power cables, which considers even harmonics. The impacts of ambient conditions and the performance of air-forced ventilation of cable tunnels are studied in this article. The proposed method is applied to an actual steel company located in Iran. The simulation test results based on the finite element method (FEM) in COMSOL Multiphysics are compared with actual measured values to validate the proposed method. Test results illustrate the advantages of the proposed method. Moreover, different paradigms for the cyclic operation of EAFs on the thermal behavior of power cables have been analyzed. Simulation results infer that 4.8% inaccuracy (about 3 ̊C) occurs in the thermal analysis due to neglecting the current harmonics. In addition, approximately 41% improvement is achievable by appropriate forced convection. Test results also imply that the maximum temperature of power cables could be effectively controlled by changes in the operation and scheduling of EAFs. Around 10% decrement in the cable system temperature could be obtained by 10 min increment time interval between two operating cycles of the EAF. Simulation results illustrate the advantages of the proposed study. • Harmonic-based thermal analysis of EAF cables considering even harmonics. • Sensitivity analysis of cables' thermal behaviors under various harmonic scenarios. • Analyses of the impacts of ambient conditions and performance of air-forced ventilation. • Validation of the FEM-based simulation results by actual experimental measurements. • Analyzing different schedulings of EAFs on the thermal behavior of power cables. [ABSTRACT FROM AUTHOR]