Insulation Parameters Research Articles

Experimental study of the factors influencing the uniformity of an air curtain and numerical simulation of the factors influencing its dust barrier effect

This study analyzes the influence of air curtain diameter and internal duct structure on the uniformity of an air curtain using Fluent numerical simulation combined with an experimental method after actual measurement of relevant parameters at the construction site, and simulates the best dust insulation parameters of a uniform air curtain. As the diameter of the air curtain supply duct increases and the internal air duct structure is reasonably designed, the axial static pressure of the air curtain generator and the air velocity at the curtain outlet are more uniform, which forms a higher strength of the air curtain. The best dust separation parameter of the uniform air curtain is the vertical downward generated air curtain with an outlet air velocity of 12 m/s and an outlet strip slit width of 80 mm, in which the dust separation efficiency could reach about 79.5%.

Application of Experimental Studies of Humidity and Temperature in the Time Domain to Determine the Physical Characteristics of a Perlite Concrete Partition

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals.

Cycle time reduction using intermittent DC internal heating in vapour phase drying of cellulose-based insulation used in transformers

ABSTRACT For the commissioning of a new transformer, a delay in delivery caused owing to the long-drying process at the manufacturer is not acceptable in order to avoid erratic power supplies and extensive down times. To increase productivity, ensure on-time delivery, avoid unplanned power outages, reduce the cost, increase the efficiency of energy utilisation and maintain the quality parameters of the transformer insulation thereby increasing its service life, cycle time of insulation drying at the manufacturer needs to be reduced. As of today, the latest technology for insulation drying of transformers at the manufacturer’s factory is the vapour phase drying (VPD) method. The cycle time in VPD may span for 4–5 days for a power transformer. This establishes the need to reduce the cycle time in VPD of transformer insulation. In this work, experimentation was carried out on 11 kV transformers for developing a system to reduce the cycle time in VPD.

Optimization of seismic insulation parameters of frame buildings using adaptive methods

Objective. The purpose of the work is to calculate frame buildings with flexible connections and with flexible and switch-off connections, to make recommendations for the use of seismic insulation methods depending on the characteristics of seismic events. Method. Development of an algorithm for calculating frame buildings of a frame structural system with seismic protection in buildings with flexible connections and with flexible and switchable connections Result. A method for calculating frame buildings of a frame structural system with seismic insulation in the form of flexible connections and flexible and switchable connections has been developed. A computer calculation program for seismically insulated and nonseismically insulated frame buildings in the Delphi 5.0 programming environment in the Object Pascal language using the Runge-Kutta numerical method of the 4th order for solving differential equations has been compiled Conclusion. It is determined that the construction of frame buildings with the seismic insulation methods considered in this paper, namely with flexible connections and with flexible connections and disconnecting connections, is not impractical for territories where long-period fluctuations are possible, due to the fact that excessively high deformations occur.

Analytical solutions for the advective–diffusive ice column in the presence of strain heating

Abstract. A thorough understanding of ice thermodynamics is essential for an accurate description of glaciers, ice sheets and ice shelves. Yet there exists a significant gap in our theoretical knowledge of the time-dependent behaviour of ice temperatures due to the inevitable compromise between mathematical tractability and the accurate description of physical phenomena. In order to bridge this shortfall, we have analytically solved the 1D time-dependent advective–diffusive heat problem including additional terms due to strain heating and depth-integrated horizontal advection. Newton's law of cooling is applied as a Robin-type top boundary condition to consider potential non-equilibrium temperature states across the ice–air interface. The solution is expressed in terms of confluent hypergeometric functions following a separation of variables approach. Non-dimensionalization reduces the parameter space to four numbers that fully determine the shape of the solution at equilibrium: surface insulation, effective geothermal heat flow, the Péclet number and the Brinkman number. The initial temperature distribution exponentially converges to the stationary solution. Transient decay timescales are only dependent on the Péclet number and the surface insulation, so higher advection rates and lower insulating values imply shorter equilibration timescales, respectively. In contrast, equilibrium temperature profiles are mostly independent of the surface insulation parameter. We have extended our study to a broader range of vertical velocities by using a general power-law dependence on depth, unlike prior studies limited to linear and quadratic velocity profiles. Lastly, we present a suite of benchmark experiments to test numerical solvers. Four experiments of gradually increasing complexity capture the main physical processes for heat propagation. Analytical solutions are then compared to their numerical counterparts upon discretization over unevenly spaced coordinate systems. We find that a symmetric scheme for the advective term and a three-point asymmetric scheme for the basal boundary condition best match our analytical solutions. A further convergence study shows that n≥15 vertical points are sufficient to accurately reproduce the temperature profile. The solutions presented herein are general and fully applicable to any problem with an equivalent set of boundary conditions and any given initial temperature distribution.

Model modification and influence of edge effect on effective area of giant electro-rheological polishing using plate electrodes

Abstract Giant electro-rheological polishing (GPRP) is recognized as an innovative ultra-precision machining technology with significant potential. However, the pronounced edge effect within the GPRP's polishing gap can introduce errors in calculating the effective area and designing the electrode structure. This, in turn, may lead to under-polishing and an increased risk of insulation breakdown. In this study, COMSOL was employed to investigate the electric field distribution characteristics within the polishing gap. This exploration aimed to refine the calculation model of the effective area, optimize the plate electrodes' structure and size, and diminish the likelihood of insulation breakdown. Through systematic finite element simulations, the impact of polishing voltage, inter-electrode gap, and plate length on the edge effect was thoroughly analyzed to ascertain its influence range. The simulation findings revealed that, while maintaining a constant inter-electrode gap for the tool electrode, variations in the polishing gap, polishing voltage, and plate length within specific ranges resulted in an edge effect influence range of approximately 1 mm. Moreover, when the machining gap, polishing voltage, and plate length remained unchanged, the edge effect influence range increased proportionally with the electrode gap within a specific range, approximately equivalent to the size of the electrode gap. Experimental validation of the giant electro-rheological effect confirmed the existence and influence range of the edge effect, aligning with the finite element simulation results. Ultimately, modifications to the calculation model of the effective area were proposed, along with a solution to optimize the electrode size and structure, with the objective of reducing the probability of insulation breakdown. In practical applications, this work can provide a valuable reference for electrode structure design, insulation breakdown improvement and parameter selection.

Performance analysis and optimization of insulation layers on a novel building-integrated photovoltaic system

Conventional photovoltaic-thermoelectric generator (PV-TEG) systems are hindered by significant heat transfer losses, which impair power generation throughout the year. Addressing this challenge, a novel PV-MCHP-TEG system is proposed, integrating photovoltaic (PV) cell, microchannel heat pipe (MCHP) array, and thermoelectric generator (TEG) module components with strategically placed insulation layers to facilitate year-round, day-and-night power generation. This study primarily investigates the impact of insulation layers on heat transfer processes, employing a comprehensive analysis and optimization approach. Utilizing Simulink software, the multifaceted influence of insulation layer variables, including locations, thicknesses, and materials, on TEG efficiency across various conditions was examined. Further, a comparative analysis was undertaken to evaluate the dynamic payback period across different modes. The optimization of these insulation parameters revealed that incorporating Polyisocyanurate Foam (PIR) as the insulation material in the optimized PV-MCHP-TEG system achieved an efficiency of 19.32 %, marking a 2.41 % improvement over conventional PV-TEG systems without insulation. Furthermore, the dynamic payback period was reduced to 11.34 years, representing a decrease of 1.05 years compared to conventional PV-TEG systems. These findings underscore the potential of our proposed system to outperform existing solutions by optimizing thermal management through insulation, thereby offering a promising avenue for enhancing photovoltaic-thermoelectric energy conversion.

Analysis of the features of the shielding system of polymer insulation structures of high voltage electrical equipment

In the article, the authors analysed the existing shielding systems of insulating structures of high-voltage devices together with electrodes under high potential. At the same time, the possibilities of using toroidal screens of various designs and the conditions of their installation in gas-filled equipment structures (gas-filled current and voltage measuring transformers, arresters, etc.) using polymer insulating materials are considered. Based on the analysis of literary sources, the most effective method of estimating the electric load parameters for determining the electric field strength distribution along the continuous insulating structure of gas-filled high-voltage devices with axial symmetry is proposed. This design is a support-insulating shell filled with SF6 as an internal insulating medium. Methodical materials are recommended that allow you to estimate the electrical load parameters (voltage and field strength) depending on the design features of the device and the shielding system used to level the electric field. Based on them, it is possible to evaluate the effectiveness of the calculation coefficients of the shielding system of gas-filled high-voltage equipment in the design process and during the improvement of individual design solutions. The results of the analytical evaluation by such methods are in good agreement with the data of experimental studies and statistical information obtained as a result of monitoring the work of insulating structures, taking into account real operating conditions and the influence of external factors. The introduction of the obtained materials allows you to take into account the influence of external factors and operational characteristics inherent in measuring transformers and overvoltage limiters. To explain the results of the analysis of methodical materials carried out in the article, as an example, the results of calculations of the support-insulation shell of the gas-filled current transformer of the TOG series, which was the most affected during operation, are given. in adverse conditions, given under such conditions as external pollution, humidity and their combination, as well as under conditions of overvoltage of various origins, etc. On the basis of the presented materials, it is possible to more accurately determine the effectiveness of various screenings. system, as well as how to predict the field strength distribution parameters under the influence of the shielding system, taking into account its design features. In addition, on the basis of the conclusions formed in the work, it is possible to plan and conduct an additional series of calculations and experimental tests taking into account the features of specific structures. Thus, the obtained results can be used to evaluate the external insulation parameters of both gas-filled measuring transformers and similar high-voltage equipment of distribution devices and transformer substations.

Development of a vibration-damping, sound-insulating, and heat-insulating porous sphere foam system and its application in green buildings

With the development of green buildings, people pay more attention to the quality of the indoor sound environment. The air sound insulation performance of floors and exterior walls plays a key role in today's green buildings. The thermal performance of the enclosure structure's floor and exterior wall heat transfer resistance is an important factor in reducing building carbon emissions in green buildings. The aim of this paper is to study the efficiency of the acoustic and thermal insulation of a foaming system with porous carbon balls and the combination of different structural ways of construction boards and external walls. The acoustic and thermal parameters of different sound insulation and thermal insulation systems designed with porous carbon sphere foam and inserted into the floors and exterior walls are compared to highlight the optimal structure. The theoretical and experimental tests showed that to improve the sound insulation performance of the floor, a sound insulation system needs to be placed on the surface of the floor in contact with the impact object and inlaid in the vertical gap in contact with the floor and the wall. Furthermore, it has been determined that the surface of the foam particle acoustic ball with micropores has good sound absorption performance. Finally, the high-quality building thermal insulation material with low thermal conductivity in any combination with the floor slabs and the external wall structure improves the thermal insulation performance.

New Short-Circuited Coaxial Method Implementation for Complex Permittivity Measurement of Power Transformer Oils

The investigation into the dielectric properties of transformer oils has been a focal point in both historical and contemporary electric insulation technology as high-voltage applications have greatly benefited from the continuous research efforts in this field. The dielectric permittivity is one of the factors to be negotiated when discussing the electric insulation of any material. This work aims to showcase a new short-circuited coaxial cable method to evaluate the complex dielectric permittivity of palm, sunflower and rapeseed oil and review other previously used measurement techniques. Mainly, the test was performed using a sample holder that represents a short-ended coaxial cable filled with the test material which is connected to one port of a vector network analyser. The measurements of the input impedance for various oil samples were conducted at frequencies ranging from 1 MHz to 10 MHz. The technique uses the value of the input impedance which depends on the reflected signals from the test sample to the network analyser, consequently, the value of the dielectric permittivity and dielectric loss have been calculated using the short circuit impedance formula which involves numerical methods to get the results which shows that this method can be used as an alternative to investigate the oils insulation parameters as it provides smooth results for permittivity without any divergence, ensuring more reliable and consistent measurements as well as providing high accuracy in determining the permittivity of materials.

Assessment of the Influence of Equipment on the Experimental Result When Determining the Sound Insulation Parameters of a Panel Structure

Assessment of the Influence of Equipment on the Experimental Result When Determining the Sound Insulation Parameters of a Panel Structure

Multi-parameter-based fuzzy logic diagnostic system for health assessment of power transformer

ABSTRACT Power transformers are the most valuable assets in the power system. An appropriate asset management is therefore essential for ensuring a reliable power supply to the utility managers. This is accomplished through continuous transformer condition monitoring. The transformers’ asset management involves a severe investigation into its insulation health index. It is determined by utilising several diagnostic parameters of transformer insulation. In this context, a novel fuzzy logic-based health index model has been proposed in the present paper to find the overall health condition of transformers. This model utilises the results extracted from several important diagnostic tests of transformer insulation, such as furan analysis and dissolved gas analysis. The validity of the proposed fuzzy logic model has been tested using real data from 200 transformer samples. These samples are collected from different-rated transformers of the Himachal Pradesh State Electricity Board (HPSEB), India. Further, the efficacy of the proposed fuzzy logic model has been validated against the expert model presented in literature. It is revealed from the comparison that the accuracy of the present proposed model is 92%. Also, it is observed that the proposed fuzzy logic model is very effective in interpreting dissolved gases and the other diagnostic test results of the transformer.

Online Detection and Classification of Interturn and Groundwall Insulation Aging Based on Broadband Common-Mode Impedance Spectrum

Online condition monitoring for stator insulation is important for reliable operation of electrical machines. Recent studies show that the method based on common-mode (CM) impedance spectrum is effective in online monitoring of the overall insulation ageing condition. However, it is difficult to detect the inter-turn ageing condition since the groundwall insulation ageing has the similar impact on the monitoring results. In this paper, the relationship between the change in the common-mode impedance spectrum and the stator winding insulation ageing is studied based on the per-turn-unit broadband CM stator winding model. The dataset of impedance spectrum for different insulation ageing conditions is built using this model. Multiple points in the impedance spectrum are used to detect the change in the inter-turn and groundwall insulation parameters separately. The online experiment results prove the validity of the proposed method. The proposed method can detect the insulation ageing condition with the error about 6%. There is no other method which can quantify the ageing degree of inter-turn insulation in the presence of groundwall insulation ageing. Compared with the black-box data-driven methods, the proposed method is based on a model with clear physical meaning, which makes the results more reliable.

CFD Simulation of Heat Transfer Through a Window Frame

The use of various coatings with a low level of radiation on the glass elements of window structures, filling the interglacial space in double-glazed windows with inert gases instead of air, increasing the number of cameras in double-glazed windows, other constructive measures aimed at improving the thermal insulation properties of double-glazed windows, led to a significant increase in the thermal resistance of the fenestration system. However, little has changed in the design and construction of window frames and edge areas adjacent to building facades, leaving these elements responsible for heat transfer through modern windows. In this article, with the help of three-dimensional CFD modeling, the thermal insulation properties of window frames are investigated in the most complete setting, taking into account the effect on heat transfer through the profile of the window frame of the adjacent walls of the building facade on one side and the double-glazed unit on the other. Finding out the thermal insulation parameters of the window frame will help to make appropriate changes in its design.

Numerical thermal assessment and theoretical analysis of horizontal-hole interlock composite insulation blocks

In this paper, the thermal performance of 54 horizontal-hole interlocking composite insulation blocks was numerically analyzed based on the steady-state heat transfer model, the regulations were found, and prediction models for the thermal parameters of the blocks were established based on the parallel network thermal resistance model. The influence of block types and block materials on the thermal performance was studied, and it was found that the thermal performance of H-shaped interlocking insulation blocks was better than that of crossed-shaped ones, and the lower the thermal conductivity of block materials, the better the thermal performance of blocks, among which the reduction of thermal conductivity of concrete materials improved the thermal performance of blocks the most. The simulated values of thermal conductivity of H-shaped interlocking insulation blocks and thermal conductivity under the parallel network thermal resistance model were highly linearly correlated with correlation coefficients as high as 0.998 and 0.999. This finding enables the prediction models of thermal parameters of H-shaped interlocking insulation blocks to be established with high accuracy and provides an effective guide for the energy-saving design of interlocking insulation blocks wall.

Ensuring the Energy Efficiency of Buildings through the Simulation of Structural, Organizational, and Technological Solutions for Facade Insulation

The article presents ways of selecting effective designs and technological and organizational solutions for the bonded thermal insulation systems of complex-shaped facades based on thermal field and flow modeling using the SolidWorks Simulation Xpress 2021 software and experimental–statistical modeling using the Compex program. Determining optimal insulation parameters at the design stage will help eliminate the negative effects of thermal bridges at balcony junctions and reduce the cost of implementing bonded thermal insulation systems for facades with complex shapes. It has been established that the most effective approach is to insulate not the entire perimeter of the balcony slab, as required by normative documentation, but rather to insulate a sufficient portion of the exterior wall, which is equal to 750 mm, with a 30 mm insulation thickness on top of the slab and 50 mm beneath it. This insulation technology is economically feasible for modern multistory buildings with nonstandard volumetric and architectural solutions, constructed using frame–brick, frame–monolithic, or monolithic schemes without thermal breaks between the balcony slab and the monolithic floor slab, with open-type balconies, bays, or uncovered loggias.

An EXPERIMENTAL STUDY ON DIELECTRIC PARAMETERS OF XLPE INSULATED HIGH VOLTAGE CABLES UNDER DIFFERENT OPERATING CONDITIONS

High voltage underground cables used in distribution systems provide benefits including aesthetics, reliability, low maintenance costs, and resistance to environmental factors. However, their initial installation expenses are considerably higher than overhead lines, and fault detection is quite challenging. Thus, a deep analysis of dielectric parameters is crucial. Typically, electrical specifications of high voltage underground cables provided by the manufacturer are used for nominal operating conditions. However, it is essential to acknowledge that variations in operational conditions have a discernible impact on the dielectric characteristics of cable insulation. This phenomenon results in an accelerated aging process of the insulation material and contributes to unexpected failures. Hence, it is imperative to determine dielectric parameters of cable insulation under varying operational conditions and elucidate the impact of these operational states on insulation properties. This study involved experimental determination of the dielectric parameters, including capacitance, relative dielectric constant, dielectric loss, and tanδ, for a XLPE insulated high voltage underground cable, designed for a nominal voltage of 12/20 kV. These assessments were performed under varying operating conditions, specifically for distinct voltage, temperature, and frequency. Based on the acquired findings, it is evident that the dielectric characteristics of the cable insulation exhibit substantial variations in response to alterations in voltage, temperature, and frequency, even when operating within the defined nominal limits.

Study of leakage current in underground mine power network: a case study in mining in Vietnam

Purpose. To determine DC leakage current in mine power network with long DC power transmission. Methodology. Nowadays, the increase in capacity and working depth leads to the use of DC power transmission, which has many benefits both economically and technically in mining. However, the appearance of DC power transmission changes the structure of the network. In the underground mine power network, there will be electrical networks with industrial frequency 50 Hz, DC power networks, and power networks after variable frequency inverters. The correlation of these network parameters complicates leakage protection in the mine power network. For DC power transmission in mining, the DC network parts have a large length, so during the working process, electricity leakage in these parts of the network often occurs. Leakage current in a DC network depends not only on DC network parameters but also on AC network parameters. The article uses analytical methods and simulation methods on Matlab/Simulink software to determine leakage currents in underground mine power networks with DC transmission when there is a change in power network parameters. Findings. The research results show that the leakage current value of the DC network is greatly affected when the insulation parameters of the electrical network change, not only in the DC power network but also in the AC network before and after the inverter. This causes the unreliable operation of the leakage protection device in this DC transmission network. Originality. Calculation model and simulation of DC leakage current in underground mine power networks with long DC transmission in mining in Vietnam Practical value. The research results are the basis for calculating and selecting leakage protection equipment for the purpose of improving safety in underground mining in Vietnam.

Life cycle assessment (LCA) and energy assessment of the production and use of windows in residential buildings

There is an observable scarcity of comprehensive research results comparing the environmental damage associated with both the production of windows and their subsequent operation. The environmental impact of the operation of windows depends on their thermal insulation parameters, and thus the amount of heat that must be generated to heat the building. The type of heating system and, above all, the type of fuel used to generate heat are also not without significance. Unfortunately, in Poland, a significant proportion of single-family houses operate on the fossil fuel heating system, including on coal and fuel oil. It is therefore important to present an environmental balance sheet of both the production and operation of windows for different variants of building heating. The purpose of the study was to determine: to what extent the manufacturing of windows of different construction and different insulation parameters affects the environment, to what extent does the negative environmental impact of the process of manufacturing with greater insulation compensate by the lower environmental impact related to savings on fuel (gas, coal, fuel oil) used to generate heat during the operation of windows. Three types of windows were selected for a detailed analysis: a triple-glazed aluminum construction, a double-glazed PVC construction and a triple-glazed PVC. The research results show that in the case of all impact categories, the greater environmental losses related to the improvement of the thermal insulation parameters of the windows at the production stage are fully compensated at the stage of their useful life, regardless of the type of fuel used to heat the buildings. Double-glazed PVC windows should be phased out of production due to significant environmental footprint associated with their operation.

Influence of compaction direction on selected thermal and moisture properties of a lightweight composite based on magnesium binder and organic filler

An alternative binder in thermal insulation composites based on hemp shives is magnesium cement. It provides higher mechanical strength of the composite in comparison to the lime binder. Thanks to this, it is possible to reduce the amount of binder in relation to the shives, and as a result, obtain a lower density and better thermal insulation parameters. The process of compacting the composite mixture determines many of its properties. The longitudinal shape of the shives causes that during compaction they are arranged mainly perpendicular to the direction of compaction. The unidirectional course of the fibers in the shives determines the anisotropic nature of both the shives and the composite. The article presents the results of tests of thermal conductivity and capillary rise of the compacted composite in the direction perpendicular and parallel to the heat flux and moisture transport. A composite with a low binder content, characterized by a density of about 250 kg/m3, was tested. The direction of the mix compaction had an impact on the differences in the obtained results. This phenomenon can be used, for example, in the production of blocks or other prefabricated elements, using the appropriate direction of compaction depending on the expected properties and applications of the composite.