scholarly journals A Method for Determining the Impact of Ambient Temperature on an Electrical Cable during a Fire

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7260
Author(s):  
Bogdan Perka ◽  
Karol Piwowarski
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Cross Sections ◽  
Environmental Parameters ◽  
Thermal Conditions ◽  
Experimental Tests ◽  
Thermal Capacity ◽  
Heating Time ◽  
Electrical Systems ◽  
The Impact

Evaluating environmental conditions that trigger fire-fighting equipment is one of the primary design tasks that have to be taken into account when engineering electrical systems supplying such devices. All of the solutions are aimed at, among others, preserving environmental parameters in a building being on fire for an assumed time and at a level enabling safe evacuation. These parameters include temperature, thermal radiation, visibility range, oxygen concentration, and environmental toxicity. This article presents a new mathematical model for heat exchange between the environment and an electric cable under thermal conditions exceeding permissible values for commonly used non-flammable installation cables. The method of analogy between thermal and electrical systems was adopted for modelling heat flow. Determining how the thermal conductivity of the cable and the thermal capacity of a conductor-insulation system can be applied to calculate the wire temperature depending on the heating time t and distance x from the heat source is discussed. Thermal conductivity and capacity were determined based on experimental tests for halogen-free flame-retardant (HFFR) cables with wire cross-sections of 2.5, 4.0, and 6.0 mm2. The conducted experimental tests enable verifying the results calculated by the mathematical model.

scholarly journals On parameterization of heat conduction in coupled soil water and heat flow modelling

2012 ◽  
Vol 7 (No. 4) ◽  
pp. 125-137 ◽  
Author(s):  
J. Votrubová ◽  
M. Dohnal ◽  
T. Vogel ◽  
M. Tesař
Keyword(s):  
Thermal Conductivity ◽  
Soil Water ◽  
Heat Transport ◽  
Preferential Flow ◽  
Thermal Conditions ◽  
Industrial Applications ◽  
Soil Thermal Conductivity ◽  
Vegetation Season ◽  
Simulation Results ◽  
The Impact

Soil water and heat transport plays an important role in various hydrologic, agricultural, and industrial applications. Accordingly, an increasing attention is paid to relevant simulation models. In the present study, soil thermal conditions at a mountain meadow during the vegetation season were simulated. A dual-continuum model of coupled water and heat transport was employed to account for preferential flow effects. Data collected at an experimental site in the Šumava Mountains, southern Bohemia, during the vegetation season 2009 were employed. Soil hydraulic properties (retention curve and hydraulic conductivity) determined by independent soil tests were used. Unavailable hydraulic parameters were adjusted to obtain satisfactory hydraulic model performance. Soil thermal properties were estimated based on values found in literature without further optimization. Three different approaches were used to approximate the soil thermal conductivity function, λ(θ): (i) relationships provided by Chung and Horton (ii) linear estimates as described by Loukili, Woodbury and Snelgrove, (iii) methodology proposed by Côté and Konrad. The simulated thermal conditions were compared to those observed. The impact of different soil thermal conductivity approximations on the heat transport simulation results was analysed. The differences between the simulation results in terms of the soil temperature were small. Regarding the surface soil heat flux, these differences became substantial. More realistic simulations were obtained using λ(θ) estimates based on the soil texture and composition. The differences between these two, related to neglecting vs. considering λ(θ) non-linearity, were found negligible.

scholarly journals Improved Mathematical Model of Polluted Insulators nonlinear behaviour Under AC Voltage Based on Experimental Tests

2018 ◽  
Author(s):  
MousalrezaFaramarzi Palangar ◽  
Mohammad Mirzaie
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mathematical Models ◽  
Experimental Tests ◽  
The Other ◽  
Critical Voltage ◽  
Nonlinear Behaviour ◽  
New Model ◽  
The Relationship ◽  
Good Agreement

Abstract—In this paper, an improved mathematical model for flashover behavior of polluted insulators is proposed based on experimental tests. In order to determine the flashover model of polluted insulators, the relationship between conductivity and salinity of solution pollution layer of the insulator is measured. Then, the leakage of current amplitude of four common insulators versus axial, thermal conductivity and arc constants temperature was determined. The experimental tests show that top leakage distance (TLd) to bottom leakage distance (BLd) ratio of insulators has a significant effect on critical voltage and current. Therefore, critical voltage and current were modeled by TLd to BLd ratio Index (M). Also, salinity of solution pollution layer of the insulators has been applied to this model by resistance pollution parameter. On the other hand, arc constants of each insulator in new model have been identified based on experimental results. Finally, a mathematical model is intended for critical voltage against salinity of solution pollution layer of different insulators. This model depends on insulator profile. There is a good agreement between the experimental tests of pollution insulators obtained in the laboratory and values calculated from the mathematical models developed in the present study.

scholarly journals Improved Mathematical Model of Polluted Insulators nonlinear behaviour Under AC Voltage Based on Experimental Tests

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
MousalrezaFaramarzi Palangar ◽  
Mohammad Mirzaie
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mathematical Models ◽  
Experimental Tests ◽  
The Other ◽  
Critical Voltage ◽  
Nonlinear Behaviour ◽  
New Model ◽  
The Relationship ◽  
Good Agreement

In this paper, an improved mathematical model for flashover behavior of polluted insulators is proposed based on experimental tests. In order to determine the flashover model of polluted insulators, the relationship between conductivity and salinity of solution pollution layer of the insulator is measured. Then, the leakage of current amplitude of four common insulators versus axial, thermal conductivity and arc constants temperature was determined. The experimental tests show that top leakage distance (TLd) to bottom leakage distance (BLd) ratio of insulators has a significant effect on critical voltage and current. Therefore, critical voltage and current were modeled by TLd to BLd ratio Index (M). Also, salinity of solution pollution layer of the insulators has been applied to this model by resistance pollution parameter. On the other hand, arc constants of each insulator in new model have been identified based on experimental results. Finally, a mathematical model is intended for critical voltage against salinity of solution pollution layer of different insulators. This model depends on insulator profile. There is a good agreement between the experimental tests of pollution insulators obtained in the laboratory and values calculated from the mathematical models developed in the present study.

scholarly journals A Study on the Drift of Spray Droplets Dipped in Airflows with Different Directions

2020 ◽  
Vol 12 (11) ◽  
pp. 4644 ◽  
Author(s):  
Simone Pascuzzi ◽  
Volodymyr Bulgakov ◽  
Francesco Santoro ◽  
Alexandros Sotirios Anifantis ◽  
Semjons Ivanovs ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Numerical Solution ◽  
Urban Areas ◽  
Sustainable Use ◽  
Experimental Tests ◽  
Buffer Zones ◽  
Spray Droplets ◽  
Air Flows ◽  
Different Diameters ◽  
The Impact

The European Directive concerning pesticide sustainable use establishes regulations to reduce the environmental drift throughout treatments to agricultural crops, particularly in nearby sensitive areas, such as water bodies, natural reserves and urban areas. The drift represents the fraction of mixture delivered by the sprayer that is not caught by the crop, and is the clearest cause of environmental pollution. Anti-drift nozzles are usually employed, and buffer zones are also maintained along the edges of the sprayed field to reduce drift production. The aim of this work was the theoretical study of the motion of the spray droplets delivered by a nozzle, dipped in downwards and/or lateral forced air flows. A mathematical model has been developed, consisting of a system of 2nd order differential equations, to simulate the motion of water droplets of different diameters within simultaneous different directions of air flow. The graphs, obtained by means of the numerical solution of the model, allow us to analyze the level of the droplets’ drift, according to their diameter and to the speed of the lateral and the downward air flows, respectively. A lateral airflow at a speed of 5 m · s − 1 produced a drift in its direction until 1.70 m for droplets from 100 to 500 μm in diameter. For larger drops, the impact of the downward airflow is not very significant. The results obtained by the numerical solution of the mathematical model have been compared with the results of experimental tests carried out to evaluate the drift of spray produced by different nozzles.

A Numerical Simulation on Ballistic Penetration Damage of 3D Orthogonal Woven Fabric at Microstructure Level

2011 ◽  
Vol 21 (2) ◽  
pp. 237-266 ◽  
Author(s):  
Xiwen Jia ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Impact Damage ◽  
Experimental Tests ◽  
Woven Fabric ◽  
Stress Wave Propagation ◽  
Rigid Projectile ◽  
Microstructure Model ◽  
3D Orthogonal Woven ◽  
The Impact

The ballistic impact damages of 3D orthogonal woven fabric (3DOWF) penetrated under a conically cylindrical rigid projectile were investigated from experimental tests and finite element simulations. A microstructure model of the 3DOWF was established and imported into finite element geometrical preprocessor. In the microstructure model, the architecture of the 3DOWF has the same spatial configurations with that of the real 3DOWF, including the spatial distributions and cross-sections of warp, weft yarns, and Z-yarns. Mechanical parameters of the yarns were obtained from high-strain rate tests which near to the impact loading condition in ballistic tests. The impact damage evolutions of the 3DOWF were simulated with the commercial finite element code ABAQUS/Explicit. From the comparisons of damage morphologies and residual velocities of the projectile after perforation between experimental and finite element simulation, it was found that the simulation can reflect the impact damage precisely. Furthermore, the stress wave propagation and damage mechanisms can be revealed from the microstructure model. Insights gained from this study will prove extremely useful in further material and architectural studies that will ultimately lead to optimization of the 3DOWF structure.

scholarly journals Model for the analysis of thermal conductivity of composite material of natural origin

2019 ◽  
Vol 23 (6 Part A) ◽  
pp. 3513-3523
Author(s):  
Ilija Milicic ◽  
Radomir Folic ◽  
Aleksandar Prokic ◽  
Arpad Ceh
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Composite Material ◽  
Measurement Data ◽  
Experimental Tests ◽  
Wall Structure ◽  
Passive House ◽  
Average Value ◽  
Passive Houses ◽  
The Continuum

Thermal properties of the wall structure elements made from gel and straw (?Ethno-eco-passive houses?) have been investigated. The gel was made from a mixture of clay, lime, and water. A 1-D mathematical model based on the continuum mechanics, for predicting the thermal conductivity, is proposed. The results obtained by applying the proposed mathematical model were compared with the measurement data of experimental tests, using the Isomet 2114 instrument. The program envisages the measurement of thermal conductivity of three specimens, 5-year-old, comprising three series within 365 days. In the theoretical analysis, the same parameters of thermal stability were treated as in the experiment. The average value of the material thermal conductivity is 0.0990 W/mK, so it can be concluded that, the composite material intended for the envelope of the proposed constructive system ?Ethno-eco-passive house? is verified as thermally suitable.

Investigation of Potential Benefits of Using Bricks of High Thermal Capacity and Conductivity in a Rotating Calcining Kiln

2008 ◽  
Author(s):  
Lei Zhao ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Potential Energy ◽  
Thermal Energy ◽  
Energy Savings ◽  
Thermal Capacity ◽  
K Value ◽  
Hot Gas ◽  
The Impact

Petroleum coke is processed into calcined coke in a rotary kiln, where the temperature profiles of flue gas and coke bed are highly nonuniform due to different flow and combustion mechanisms. Motivated by saving energy costs, the effect of refractory brick’s thermal properties on potential energy savings is investigated. This study focuses on investigating potential energy savings by replacing inner one third of existing bricks with higher thermal capacity (Cp) and/or higher thermal conductivity (k) bricks. This investigation is motivated by postulating that the bricks with higher thermal capacity can store more thermal energy during the period of contacting with the hot gas and release more heat to the cock bed when the bricks rotate to below and in contact with the coke bed. A rotational, transient marching conduction numerical simulation is conducted using the commercial software FLUENT. The impact of brick heat capacity and thermal conductivity on transporting thermal energy to the coke bed is analyzed. The results show: (a) Increasing the heat capacity of brick layer reduces brick temperature which helps increase the heat transfer between the hot gas and brick, in other words it does help brick store more heat from the hot gas, but, heat transfer between brick and coke is reduced, which is opposite to the original postulation. (b) Higher brick thermal conductivity decreases brick temperature thus increases heat transfer between hot gas and the brick layer. The heat transfer from brick to coke bed is also increased, but not significantly. (c) Usually a brick with a higher Cp value also has a higher k-value. Simulation of a brick layer with both four times higher Cp and k values actually show appreciable heat is transported from the brick to the coke bed for one rotation for both lower and higher Cp and k bricks. The difference is not significant.

scholarly journals A Cavitation Erosion Model for Ductile Materials

2002 ◽  
Vol 124 (3) ◽  
pp. 601-606 ◽  
Author(s):  
N. Berchiche ◽  
J. P. Franc ◽  
J. M. Michel
Keyword(s):  
Cross Sections ◽  
Cavitation Erosion ◽  
Experimental Tests ◽  
Material Surface ◽  
Impact Loads ◽  
Physical Analysis ◽  
Ductile Materials ◽  
Hardening Process ◽  
Strain Relationship ◽  
The Impact

An analytical model is proposed for the prediction of cavitation erosion of ductile materials. It is based upon a physical analysis of the work-hardening process due to the successive bubble collapses. The material is characterized by its classical stress-strain relationship and its metallurgical behavior is analyzed from microhardness measurements on cross sections of eroded samples. The flow aggressiveness is determined from pitting tests, using the material properties to go back to the impact loads. The histogram of impact loads is applied numerically a large number of times on the material surface and the evolution of the mass loss with the exposure time is computed. The approach is supported by experimental tests.

scholarly journals Improved Mathematical Model of Polluted Insulators nonlinear behaviour Under AC Voltage Based on Experimental Tests

2018 ◽  
Vol 1 (3) ◽  
Author(s):  
MousalrezaFaramarzi Palangar ◽  
Mohammad Mirzaie
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mathematical Models ◽  
Experimental Tests ◽  
The Other ◽  
Critical Voltage ◽  
Nonlinear Behaviour ◽  
New Model ◽  
The Relationship ◽  
Good Agreement

In this paper, an improved mathematical model for flashover behavior of polluted insulators is proposed based on experimental tests. In order to determine the flashover model of polluted insulators, the relationship between conductivity and salinity of solution pollution layer of the insulator is measured. Then, the leakage of current amplitude of four common insulators versus axial, thermal conductivity and arc constants temperature was determined. The experimental tests show that top leakage distance (TLd) to bottom leakage distance (BLd) ratio of insulators has a significant effect on critical voltage and current. Therefore, critical voltage and current were modeled by TLd to BLd ratio Index (M). Also, salinity of solution pollution layer of the insulators has been applied to this model by resistance pollution parameter. On the other hand, arc constants of each insulator in new model have been identified based on experimental results. Finally, a mathematical model is intended for critical voltage against salinity of solution pollution layer of different insulators. This model depends on insulator profile. There is a good agreement between the experimental tests of pollution insulators obtained in the laboratory and values calculated from the mathematical models developed in the present study.

Investigation of Potential Benefits of Using Bricks of High Thermal Capacity and Conductivity in a Rotating Calcining Kiln

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Lei Zhao ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Potential Energy ◽  
Thermal Energy ◽  
Energy Savings ◽  
Thermal Capacity ◽  
K Value ◽  
Hot Gas ◽  
The Impact

Petroleum coke is processed into calcined coke in a rotary kiln, where the temperature profiles of flue gas and coke bed are highly nonuniform due to different flow and combustion mechanisms. Motivated by saving energy costs, the effect of refractory brick’s thermal properties on potential energy savings is investigated. This study focuses on investigating potential energy savings by replacing inner one-third of existing bricks with higher thermal capacity (Cp) and/or higher thermal-conductivity (k) bricks. This paper investigates the postulation: the bricks with higher thermal capacity could store more thermal energy during the period in contact with the hot gas and would release more heat to the cock bed when the bricks rotate to the position in contact with the coke bed. A rotational transient marching conduction numerical simulation is conducted using the commercial software FLUENT. The impact of brick heat capacity and thermal conductivity on transporting thermal energy to the coke bed is analyzed. The results show the following: (a) Increasing the heat capacity of brick layer reduces brick temperature, which helps increase the heat transfer between the hot gas and brick. In other words, it does help brick to store more heat from the hot gas, but heat transfer between brick and coke is reduced, which is opposite to the original postulation. (b) Higher brick thermal conductivity decreases brick temperature, thus increases heat transfer between hot gas and the brick layer. The heat transfer from brick to coke bed is also increased but not significantly. (c) Since usually a brick with a higher Cp value also has a higher k-value, simulation of a brick layer with both four times higher Cp and k-values actually shows a reduction in the brick temperature, and hence a degradation of the heat transfer between the brick and coke bed. Therefore, replacing the existing brick layer with a high Cp- and/or high k-value brick is not recommended.

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