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Aiming at the transient process generated by the operation of the disconnector, the fast transient overvoltage (VFTO) transmitted to the casing from the GIS system causes the induced casing voltage between the casing and the ground, posing safety hazards to the secondary equipment and operation personnel of the GIS system. This paper combines the internal VFTO and external TEV transient circuits of GIS, considers the mutual coupling of the three-phase GIS enclosures, establishes a 252 kV GIS system transient model, and studies the characteristics of the three-phase GIS enclosure TEV under multiple breakdown discharge conditions of the disconnector, providing a theoretical basis for the external measurement of the transient induced casing voltage. In the process of multiple breakdown conditions, the maximum TEV value of the operating phase is the highest, with the maximum TEV amplitude reaching 0.03 p.u. in Phase A. TEV amplitude of the operating phase is significantly higher than that of the other two phases.

Equipment with type of protection “d” provides explosion protection by its enclosure that withstands the pressure of an internal explosion and prevents the transmission of explosion to the explosive atmosphere that surrounds the enclosure. In this case the explosion protection is maintained even in case of an internal explosion. The maximum surface temperature of a flameproof equipment considers the temperature of external surfaces (for the inclusion of equipment in a temperature class). There is also an increase of temperature during the internal explosion. The purpose of this paper is to monitor the temperature increase in case of an internal explosion considering an equipped flameproof enclosure (using an internal equivalent model instead of internal apparatus). The tests are performed with different gases, including hydrogen, considering the gas concentrations used to perform the tests in explosive mixtures for flameproof equipment.

The article presents a practical 3D heat and vapour model to estimate the risk for interstitial condensation in building enclosures. The model is in fact a three-dimensional implementation of the Glaser method. In the first part of this article the modelling assumptions and solution technique are outlined. Next, the model is validated against an example from the literature. The third part of the article zooms in on the applicability of the proposed model in comparison to more complex hygrothermal models. Both the weaknesses and the strengths of the methodology are discussed. This section reviews the circumstances in which the model can be used safely and when a more detailed analysis is preferable. Finally, the article presents an actual case whereby the applicability of the model is demonstrated by making design decisions for the energetic retrofit of a curtain wall system.

Thick ellipsoids were recently introduced by the authors to represent uncertainty in state variables of dynamic systems, not only in terms of guaranteed outer bounds but also in terms of an inner enclosure that belongs to the true solution set with certainty. Because previous work has focused on the definition and computationally efficient implementation of arithmetic operations and extensions of nonlinear standard functions, where all arguments are replaced by thick ellipsoids, this paper introduces novel operators for specifically evaluating quasi-linear system models with bounded parameters as well as for the union and intersection of thick ellipsoids. These techniques are combined in such a way that a discrete-time state observer can be designed in a predictor-corrector framework. Estimation results are presented for a combined observer-based estimation of state variables as well as disturbance forces and torques in the sense of an unknown input estimator for a hovercraft.

Purpose Natural convection heat transfer analysis can be completed using entropy generation analysis. This study aims to accomplish both the natural convection heat transfer and entropy generation analyses for a hexagonal cavity loaded with Cu-H2O nanoliquid subjected to an oriented magnetic field. Design/methodology/approach Control volume-based finite element method is applied to solve the non-dimensional forms of governing equations and then, the entropy generation number is computed. Findings The results portray that both the average Nusselt and entropy generation numbers boost with increasing aspect ratio for each value of the undulation number, while both of them decrease with increasing the undulation number for each amplitude parameter. There is a maximum value for the entropy generation number at a specified value of Hartmann number. Also, there is a minimum value for the entropy generation number at a specified value of angle of the magnetic field. When the volume fraction of nanoparticles grows, the average Nusselt number increases and the entropy generation number declines. The entropy generation number attains to a maximum value at Ha = 14 for each value of aspect ratio. The average Nusselt number ascends 2.9 per cent and entropy generation number decreases 1.3 per cent for Ha = 0 when ϕ increases from 0 to 4 per cent. Originality/value A hexagonal enclosure (complex geometry), which has many industrial applications, is chosen in this study. Not only the characteristics of heat transfer are investigated but also entropy generation analysis is performed in this study. The ecological coefficient of performance for enclosures is calculated, too.

The research described in the article concerns sound-insulating enclosures used for sound sources imitating a noisy machine or device. It is a continuation of experimental tests and modelling studies conducted previously on a prototype test stand, in which the enclosure walls measured 0.7 m × 0.7 m. The main aim of the research was to estimate the acoustic efficiency of the enclosures through experimental testing on a new stand with walls measuring 0.55 m × 0.55 m, conducted under conditions similar to those found in an industrial facility. Tests conducted for five wall types of varying thicknesses, made of materials such as steel, aluminium, and plexiglass, enabled the development of a calculation model for insertion loss, which could be used on the basis of the material data for the enclosure walls. The model was validated during further experimental tests covering four additional material variants and a high correlation of the results was obtained. The influence of the calculation model used for the enclosure wall’s transmission loss on the insertion loss result was also investigated. The results of the experimental tests and modelling studies were also compared to those obtained for a larger enclosure made of the same wall materials. The research described in the article may have practical applications in the selection of walls of cube-shaped enclosures and in estimating their effectiveness in a cost-free manner, assuming that the appropriate material data is used in the calculations.

The hull is an important component of the submarine structure, and it is also one of the factors that affect the concealment of the submarine. By using the finite element method, a submarine model was established to analyze the hydrodynamic noise at the contact points between the front and rear of the hull and the hull under different diving angles. The results show that when the diving angle is about 10°, the hydrodynamic noise at the front and rear positions of the enclosure is relatively small. The research results provide a reference for ensuring the stealth operation conditions of submarines and have practical significance for improving the stealth of submarines.

Fractional-order differential equations are powerful tools for the representation of dynamic systems that exhibit long-term memory effects. The verified simulation of such system models with the help of interval tools allows for the computation of guaranteed enclosures of the domains of reachable pseudo states over a certain finite time horizon. In the previous work of the author, an iteration scheme—derived on the basis of the Picard iteration—was published that makes use of Mittag-Leffler functions to determine guaranteed pseudo-state enclosures. In this paper, the corresponding iteration is generalized toward the use of exponential functions during the evaluation of the iteration scheme. Such exponential functions are well-known from a verified solution of integer-order sets of differential equations. The aim of this work is to demonstrate that the use of exponential functions instead of pure box-type interval enclosures for Mittag-Leffler functions does not only improve the tightness of the computed pseudo-state enclosures but also reduces the required computational effort. These statements are demonstrated with the help of a close-to-life simulation model for the charging/discharging dynamics of Lithium-ion batteries.

Buoyant fires with gaseous fuel are discussed in the context of a closed, mechanically ventilated enclosure. Focus is on the ventilation flow rates (admission and extraction) and on the effect of leakages. The impact of the combustion is discussed. Multiple definitions of the global equivalence ratio (GER) are considered and the consequences therefore on the combustion regime is quantified. In the experimental campaign, these regimes varied from steady well-ventilated combustion to rapid extinction. These new results shed light on the fire scenario in a closed, mechanically ventilated enclosure and identify the most complex and critical configurations in terms of risk assessment.

A wide variety of approaches for set-valued simulation, parameter identification, state estimation as well as reachability, observability and stability analysis for nonlinear discrete-time systems involve the propagation of ellipsoids via nonlinear functions. It is well known that the corresponding image sets usually possess a complex shape and may even be nonconvex despite the convexity of the input data. For that reason, domain splitting procedures are often employed which help to reduce the phenomenon of overestimation that can be traced back to the well-known dependency and wrapping effects of interval analysis. In this paper, we propose a simple, yet efficient scheme for simultaneously determining outer and inner ellipsoidal range enclosures of the solution for the evaluation of multi-dimensional functions if the input domains are themselves described by ellipsoids. The Hausdorff distance between the computed enclosure and the exact solution set reduces at least linearly when decreasing the size of the input domains. In addition to algebraic function evaluations, the proposed technique is—for the first time, to our knowledge—employed for quantifying worst-case errors when extended Kalman filter-like, linearization-based techniques are used for forecasting confidence ellipsoids in a stochastic setting.