Outer Enclosure Research Articles

Thermal modernization of the housing stock of Ukraine

Coverage of the necessity of thermo-modernization of the housing stock of Ukraine, analysis of the housing and communal fund, general ways of realization of thermo-modernization and terms of its payback in Ukraine. It is revealed that about 30% of the available housing stock in Ukraine needs major or current repairs. 36,000 homes are in the old category. Most of the heat in Ukraine is spent on heating and hot waterThermal modernization of buildings in the context of external enclosure structures should be aimed at: exterior walls, roofs, windows, floors. Multilayer walls should be designed so that the vapor permeability of the layers increases from the inner surface of the wall to the outer one. Arrangement of internal thermal insulation is not effective, because moisture will be collected in the insulation. Particular attention should be paid to cold bridges: corners of buildings, concrete jumpers, joints of structures, unheated plinth or foundation.Thermotechnical indicators of thermal modernization of the walls of existing buildings have been determined, the thermal protective properties of the windows are proposed to use two-layer insulation to obtain the required parameters of roofs. It has been determined that according to DBN "Thermal Insulation of Buildings" the floor heat transfer resistance should be not less than 3,75 м2*К/Вт. This means that the minimum thickness of the insulation in the floor construction must be at least 150 mm. According to the requirements of DBN "Thermal insulation of buildings" the resistance of heat transfer of a roof in a dwelling house should be not less than 5,5 м2*К/Вт, which means that the thickness of the insulation should be not less than 200-250 mm. According to DBN "Thermal insulation of buildings" the heat transfer resistance of the outer enclosure in a dwelling should be not less than 3,3м2*К/Вт, and for windows – 0,75 м2*К/Вт.Integrated home insulation greatly improves the comfort of the premises and reduces the cost of housing. Due to the mass introduction of energy-saving technologies into the reconstruction of old buildings in Ukraine, the annual consumption of fuel and energy resources in buildings can be reduced by more than a third, or more than 300 million. GJ, equivalent to 8 billion. m3 of natural gas.

Effect of Coating of Dielectric in a 3-Phase GIB with Particle Movement

The dielectric coating effect on the motion of the Particle inside a Gas Insulated Bus duct (GIB) of three phase using epoxy resin coating of dielectric inside f GIB outer enclosure of inner surface without image charge is presented in this paper. Simulation is performed by considering various parameters like drag, gravitational and the electrostatic forces acting on the particle and a mathematical model was derived. A 2nd order differential equation for the particle motion is solved and restitution coefficient was considered at each impact of particle with the GIB enclosure. At the particle locations, estimation of electric fields instantaneously was made by CSM. The particle motion in the absence of effect of image charge is considered in a 3-phase GIB with dielectric coating. For voltage levels like 220kV, 400kV, 600kV and 800kV class, the movement of radial in nature is found for particles like aluminum and copper inside GIB. Analysis of all the results were done and presented in this paper.

Mathematical modeling of thermal technical characteristics of external protections with air layers

A screened enclosing structure of the outer wall of the building without the use of thermal insulation materials is proposed. To ensure the required thermal resistance of the outer fence, screens (cement-containing slabs) and closed air gaps between them are used. Using the ANSYS software package, the heat transfer processes were modeled in a shielded building envelope, consisting of the main (carrier) part and screens with air gaps closed between them. The features of the heat transfer process in the thickness of the outer enclosure are revealed.

Comparison of Natural Convection Around a Circular Cylinder With Different Geometries of Cylinders Inside a Square Enclosure Filled With Ag-Nanofluid Superposed Porous-Nanofluid Layers

Numerical simulations are carried out for fluid flow and natural convection heat transfer induced by a temperature difference between a hot inner cylinder with different geometries (i.e., circular; triangular; elliptic; rectangular; and rhombic) and a cold outer square enclosure filled with nanofluid superposed porous-nanofluid layers. The Darcy–Brinkman model is applied for the saturated porous layer with nanofluid. Moreover, the transport equations (mass, momentum, and energy) are solved numerically using the Galerkin weighted residual method by dividing the domain into two sets of equations for every layer with incorporating a nonuniform mesh size. The considered domains in this investigation are closely examined over a wide range of Rayleigh number (103 ≤ Ra ≤ 106), Darcy number (10−5 ≤ Da ≤ 10−1), the thickness of porous layer (0% ≤ Xp ≤ 100%), thermal conductivity ratio (1 ≤ Rk ≤ 20), and nanoparticle volume fraction (0 ≤ φ ≤ 0.1), respectively. The nanofluid is considered to be composed of Ag-nanoparticle and water as a base fluid. The results showed that the obtained total surfaces-averaged Nusselt numbers of the enclosure, in all cases, at the same operating conditions, the rate of heat transfer from the outer enclosure which the triangular cylinder is located inside is better. Also, as the thickness of the porous layer is increased from 20% to 80%, the free convection performance will decrease significantly (to about 50%) due to the hydrodynamic properties of the porous material.

Reconstrucción virtual del exterior del complejo funerario de Sarenput I (QH36)

El complejo funerario de Sarenput I (QH36) destaca por ser el único de los construidos en la necrópolis de Qubbet el-Hawa, que fue completamente terminado. Además, destaca por ser uno de los escasos ejemplos de la arquitectura funeraria privada del Reino Medio, junto con las monumentales tumbas de Qaw el-Kebir y de Assiut que, de manera simplificada, sigue la estructura de los complejos funerarios reales con escalera ascendente, patio exterior, capilla funeraria y cámaras de enterramiento. En este artículo se aporta la reconstrucción gráfica “ideal” de los espacios exteriores de QH36, conservados parcialmente, basándonos en dos niveles de conocimiento: los elementos arquitectónicos y otras evidencias arqueológicas existentes en el recinto exterior que nos permiten su reconstrucción garantizando su autenticidad y la falta de algunos de éstos que nos obliga a tomar decisiones interpretativas que, basadas en el estudio de ejemplos de la arquitectura egipcia contemporánea, garanticen un modelo con rigurosidad y veracidad histórica.

Impact of seasonal thermal stress on physiological and blood biochemical parameters in pigs under different dietary energy levels.

The present study was formulated to find out the status of important season related thermal stress biomarkers of pure-bred (Hampshire) and crossbred (50% Hampshire × 50% local) pigs under the agro-climatic condition of Assam State, India. The experiment was also aimed to study the role of different level of energy ration (110, 100, and 90% energy of NRC feeding standard for pig) in variation of physiological and biochemical parameters in two genetic groups of pigs in different seasons. The metabolizable energy value were 3260, 2936.5, and 3585.8kcal/kg in grower ration and 3260.2, 2936.6, and 3587kcal/kg in finisher ration for normal energy (NE), low energy (LE) and high energy (HE), respectively. Both the genetic group of animals were housed separately under intensive system of management. Each pen was measuring 10' × 12' along with an outer enclosure. Six weaned piglets (almost similar body weight of average 10.55kg) of each group were kept in a separate pen. However, after attainment of 35kg body weight, the animals of a group were divided in two pens of three animals each. The present experiment indicated that average ambient temperature during summer months (27.33-29.51°C) was above the comfort zone for pigs (22°C). The significantly (P < 0.01) higher relative humidity (RH) (%) was recorded in outdoor environment (87.26-91.10%) and in the morning time (86.60-91.10%). The temperature humidity index (THI) during the study period was found to be indicative of thermal stress to the experimental animals during summer (79.55-82.56). Physiological parameters viz., respiration rate (RR) and rectal temperature (RT) were significantly (P < 0.01) higher in summer season (43.75-72.12 breaths/min. and 102.29-103.23°F) and non-significantly higher values were recorded in Hampshire pigs. It was also found that the significantly (P < 0.01) lower RR as well as RT was recorded in the pigs fed with high energy (HE) ration during summer season. Serum triiodothyronine (T3) and thyroxine (T4) concentrations were significantly (P < 0.01) lower during summer, while both the genetic groups showed significantly (P < 0.01) higher concentration of serum cortisol during summer season. It was also observed that thyroid hormone and cortisol concentrations were maintained in groups of pig fed vegetable oil incorporated HE diet during summer. From the present study, it is found that the increasing the energy level of the ration might be helpful to minimize the effects of thermal stress during summer.

Experiment and Study on Mechanical Property of Sandstone Post-peak Under the Cyclic Loading and Unloading

Engineering research has shown that the surrounding rock of deep roadways experienced many times of post-peak cyclic loading and unloading. So studying on rock mechanical characteristics of post-peak loading and unloading is helpful to control the deep surrounding rocks. The test using RMT-150B rock mechanics testing system, to experiment on the mechanical properties of sandstone of post-peak cyclic loading and unloading. The results show that: the stress–strain curves of post-peak cyclic loading and unloading have significant plastic hysteretic loops. The area of plastic hysteretic loops gloss back. The enveloping outer enclosure of cycle loading curve is the similar as the stress–strain curves of strain softening stage when the samples failure, which shows that post-peak failure of rocks have significant memory. With the increase of cycles, the cumulative deterioration parameters are gradually increased, and the ultimate bearing capacity, elastic of loading section of samples and cumulative deterioration parameters conform with the exponential attenuation function with constant term. With the increase of surrounding pressure, the total energy, dissipated energy and elastic energy of samples are gradually increased. With the increase of cycles, the total energy, dissipated energy and elastic energy of samples all are gradually decreasing, the rate of reduction decreases gradually. The samples exist in vertical splitting and transverse shear combination failure under the post-peak uniaxial cycles, or exist in shear failure under the post-peak triaxial cycles. The shear plane exists slip traces.

Periodic behavior flow of three-dimensional natural convection in a titled obstructed cubical enclosure

PurposeThe purpose of this paper is to examine numerically the three natural convection of air induced by temperature difference between a cold outer cubic enclosure and a hot inner cylinder. Simulations have been carried out for Rayleigh numbers ranging from 103 to 107 and titled angle of the enclosure from 0° to 90°. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy, and is solved by finite volume method. The effects of cylinder inclination and Rayleigh number on fluid flow and heat transfer are presented. The distribution of isocontours of temperature and isosurfaces of velocity eventually reaches a steady state in the range of Rayleigh numbers between 103 and 107 for titled inclination of 90°; however, for the remaining inclinations, Rayleigh number must be in the range 103-106 to avoid unsteady state, which is manifested by the division of the area containing the maximum local heat transfer rate into three parts for a Rayleigh number equal to 107 and an inclination of 90°. We mention that instability study is not included in the present paper, which is solely devoted to three-dimensional calculations. Results also indicate that optimal average heat transfer rate is obtained for both high Rayleigh number of 106 and high inclination of 90° for the two cases of the inner cylinder and cubical enclosure.Design/methodology/approachThe manuscript deals with prediction of the three-dimensional natural convection phenomena in a cubical cavity induced by an isothermal cylinder at the center with different inclinations by simulating the flow using highly numerical methods such as finite volume method.FindingsIt is found that the local Nusselt number through active walls for titled inclination set at 90°, the symmetry of the flow is conserved and the area containing the maximum heat transfer is divided into three smaller areas situated near the upper portion of the wall, taking the maximum value. That may be due to the preparation of local occurrence of instabilities and bifurcation phenomena that appear for Ra > 107, which is not included in the present paper to save journal space. It was found also that an optimal heat transfer appears when the cylinder orientation becomes vertical (a = 90°). For this inclination, buoyancy forces act upward, corresponding to an aiding situation. In addition, heat transfer rate is increasing with Rayleigh numbers, so correlations of average Nusselt through the cubical cavity and the cylinder are established as function of two parameters (Ra, a). Comparisons of the numerical results with those obtained from all correlations show good agreements.Originality/valueTo the author’s knowledge, studies have thus far adressed three-dimensional cuboids enclosures induced by an inner shape which the location is changed. However, no study has examined three-dimensional natural convection between the inner isothermal cylinder and outer cooled cubical enclosure when the outer enclosure is tilted.

The Çevre Kale fortress and the outer enclosure on the Karacadağ at Yaraşlı

In 1992 an aerial survey of the Iron Age fortress of Cevre Kale was made using a tethered helium-filled blimp. This fortress is located on the slopes of the Karacadag above the large village of Yarasli, close to the northeast corner of Tuz Golu, the Salt Lake (Fig. 1). That brief survey was focussed on the highly visible fortress together with the obvious traces of extra mural settlement that lay immediately to the southwest. At that time the southwestern stretch of the huge, 11 km long, wall...

2-D numerical investigation of melting of an impure PCM in the arbitrary-shaped annuli

A transient numerical study is carried out using a boundary-fitted coordinate (BFC) technique to model the melting characteristics of an impure phase-change material (PCM) in the annular gap formed by an inverse outer equilateral triangular-shaped enclosure and various shaped inner tubes. A control-volume based finite difference method is used to solve the non-dimensional transformed curvilinear conservation equations for mass, momentum, and energy in terms of the physical variables. An enthalpy-porosity scheme is used to model the mushy region melting problem. The developed code is verified with the available experimental data. The effects on the melting characteristics of the PCM of the inner tube wall temperature (Rayleigh number), the initial condition of the PCM, the cross-sectional shape as well as the vertical position of the inner tube inside the annulus are ascertained. The velocity and temperature fields, the total and complete melt fractions, and the latent and total stored energies as a function of the melting time are reported. From the predicted results it is found that the heat exchanger with a vertically placed eccentric inner circular tube provides the maximum energy storage capacity. The wall temperature of the inner tube, as well as the initial temperature of the solid PCM, both has a significant influence on the melting rate of the impure PCM.

Natural convection over circular cylinders in a porous enclosure filled with a nanofluid under thermo-diffusion effects

Abstract In this study, we solved numerically the double-diffusive natural convection over circular cylinders in a non-Darcy porous enclosure filled with nanofluids using a simple algorithm in a finite volume method. Here, the inner circular cylinders are maintained at a hot temperature Th, and concentration Ch. The enclosure vertical side walls are maintained at a cool temperature Tc, and concentration Cc, and the horizontal walls are assumed to be adiabatic. The nanofluids on the outer enclosure walls and inner cylinders are passively controlled. We investigated the effects of the circular cylinders locations and sizes on the heat and mass transfer and fluid flow. The effects of Rayleigh number, Darcy parameter, Soret number with modified Dufour number and nanoparticles parameters in heat and mass transfer and fluid flow have been studied with graphical illustrations. It is found that, the size and formation of cells inside the enclosure strongly depend on the Rayleigh number with Darcy parameter, and sizes and locations of the inner circular cylinders. The current numerical results are well validated with a reasonable agreement.

Numerical simulation of three-dimensional natural convection in a cubic enclosure induced by an isothermally-heated circular cylinder at different inclinations

This study numerically examines three-dimensional natural convection of air induced by temperature difference between a cold outer cubic enclosure and a hot inner cylinder. Simulations have been carried out for Rayleigh numbers ranging from 103 to 107 and a titled angle of the enclosure varying from 0° to 90°. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy and is solved by finite volume method. The effects of cylinder inclination and Rayleigh number on fluid flow and heat transfer are presented. The distribution of isocontours of temperature, components of velocity and streamtraces eventually reaches a steady state for Rayleigh numbers ranging from 103 to 107 for titled inclination of 90°. However, for the remaining inclinations, Rayleigh numbers must be in the range 103–106 to avoid unsteady state which is manifested by the subdivision of the area, containing the maximum local heat transfer rate, into three parts for a Rayleigh number equal to 107 and an inclination of 90°. We mention that instability study is not included in the present paper which is solely devoted to three dimensional calculations. Results indicate also that optimal average heat transfer rate is obtained for Rayleigh number set to 106 and an inclination of 90° for both cases of the inner cylinder and lateral walls of cubical enclosure.

A numerical study of natural convection in an inclined square enclosure with an elliptic cylinder using variational multiscale element free Galerkin method

In this paper, a numerical study for steady-state natural convection in a cold outer square enclosure containing a hot inner elliptic cylinder is investigated using the variational multiscale element free Galerkin method (VMEFG). The VMEFG method is a meshless method which coupled element free Galerkin method and variational multiscale method, it allows equal order basis for the velocity and the pressure field. The numerical calculations are performed for various Rayleigh numbers ranging from 103 to 106, the inclination angle of the outer square enclosure from 0° to 45° and major axis of the inner cylinder from 0.2L to 0.4L. The results show that the Rayleigh number, the size of the inner cylinder and the inclination angle of the outer square enclosure have remarkable effects on the streamlines and temperature contours in the enclosure, but the inclination angle of the enclosure has a small effect on average Nusselt number on the inner elliptic cylinder.

Thermo-dynamic irreversibility induced by natural convection in square enclosure with inner cylinder. Part-I: Effect of tilted angle of enclosure

Two-dimensional numerical simulations were conducted to investigate the natural convection heat transfer induced by the temperature difference between cold walls of the tilted square enclosure and a hot inner circular cylinder for different Prandtl numbers (10−2⩽Pr⩽102) and Rayleigh numbers (103⩽Ra⩽106). The numerical solutions are obtained using an accurate and efficient immersed boundary method. The outer square enclosure is tilted from γ=0° to γ=45° by each 5°. Detailed analysis results including the distribution of streamlines, isotherms and Nusselt numbers are presented. The entropy generation and corresponding Bejan number in the enclosure are analyzed to estimate the thermo-dynamic irreversibility accompanied by the natural convection in the system.

JAMAAN AT THE PASS OF BI’REIN AN IRON AGE IIB-C AMMONITE STRONGHOLD IN CENTRAL JORDAN

In years 2015-2016 the Zarqa Directorate of the Department of Antiquities of the Hashemite Kingdom of Jordan carried out a rescue excavation at the site of Jamaan, an Iron Age IIB-C Ammonite stronghold 16 Km north of ‘Amman. The site survey and limited soundings allow to plot a plan of the structure, comprising an outer enclosure with a casemate wall, two cisterns, and a square podium tower, and to collect ceramic material dating from Iron Age IIB-C (c. 840-580 BC), as well as the head of a soft limestone statue, possibly depicting a local chief or an official. The latter adds to the relatively conspicuous number of statues from the Kingdom of Ammon, possibly illustrating the production of a non-royal commission.

The buried ‘towers’ of Angkor Wat

Abstract

Natural convection in polygonal enclosures with inner circular cylinder

This study investigates the natural convection induced by a temperature difference between cold outer polygonal enclosure and hot inner circular cylinder. The governing equations are solved numerically using built-in finite element method of COMSOL. The governing parameters considered are the number of polygonal sides, aspect ratio, radiation parameter, and Rayleigh number. We found that the number of contra-rotative cells depended on polygonal shapes. The convection heat transfer becomes constant at [Formula: see text] and the polygonal shapes are no longer sensitive to the Nusselt number profile.

NATURAL CONVECTION FROM A CYLINDER IN SQUARE POROUS ENCLOSURE FILLED WITH NANOFLUIDS

The problem of natural convection induced by a temperature difference between an outer porous enclosure and an inner circular cylinder is studied in this paper. The fluid in the porous enclosure is a water-based nanofluids containing Ag, Cu, Al2O3, or TiO2 nanoparticles. The coupled momentum and energy equations have been solved numerically over a wide range of values of the solid volume fraction, the Rayleigh number, the cylinder radius, and various temperature conditions of the bottom wall. It is found that there exists an optimum cylinder radius, below which the increasing cylinder radius increases the strength of flow circulation and above which the cylinder radius decreases the strength of flow circulation. The heat transfer rate increases linearly by increasing the nanoparticles concentration for all cylinder radius and Rayleigh number.

Natural convection in a square enclosure with four circular cylinders positioned at different rectangular locations

A numerical study was carried out to investigate natural convection heat transfer induced by a temperature difference between a cold outer square enclosure and four hot inner circular cylinders placed in a rectangular array. A two-dimensional solution for natural convection in an enclosure with four cylinders was obtained using an accurate and efficient immersed boundary method. The immersed boundary method based on the finite volume method was used to handle four inner cylinders placed equal distance away from each other within an enclosure moving along the diagonal centerlines for different Rayleigh numbers in the range 103⩽Ra⩽106. This study investigated the effects of the location of the cylinders in the enclosure on the heat transfer and fluid flow, when they moved along the diagonal centerlines of the enclosure. For all the cases considered in the present study, the flow and thermal fields eventually reached steady state in the range of 103⩽Ra⩽104. However, for 105⩽Ra⩽106, the flow and thermal fields became unsteady depending on the cylinders position. Also, the symmetry about the vertical centerline was affected by the cylinders position as well. The distribution of the instantaneous, time-averaged local and surface-averaged Nusselt number as a function of the Rayleigh number and the distance between inner cylinders was also presented.

A study of natural convection heat transfer in a nanofluid filled enclosure with elliptic inner cylinder

Purpose – The purpose of this paper is to study the effects of natural convection heat transfer in a cold outer circular enclosure containing a hot inner elliptic circular cylinder. The fluid in the enclosure is Cu-water nanofluid. The main emphasis is to find the numerical treatment for the said mathematical model. The effects of Rayleigh number, inclined angle of elliptic inner cylinder, effective of thermal conductivity and viscosity of nanofluid, volume fraction of nanoparticles on the flow and heat transfer characteristics have been examined. Design/methodology/approach – A very effective and higher order numerical scheme Control Volume-based Finite Element Method (CVFEM) is used to solve the resulting coupled equations. The numerical investigation is carried out for different governing parameters namely; the Rayleigh number, nanoparticle volume fraction and inclined angle of elliptic inner cylinder. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell-Garnetts (MG) and Brinkman models, respectively. Findings – The results reveal that Nusselt number increases with an increase of nanoparticle volume fraction, Rayleigh numbers and inclination angle. Also it can be found that increasing Rayleigh number leads to a decrease in heat transfer enhancement. For high Rayleigh number the minimum heat transfer enhancement ratio occurs at. Originality/value – To the best of the authors’ knowledge, no such analysis is available in the literature which can describe the natural convection heat transfer in a nanofluid filled enclosure with elliptic inner cylinder by means of CVFEM.