Energy-efficient Structures Research Articles

Simulation gas combustion process in modern heat generators of small and medium power

The paper presents the problems of numerical modelling of burners and fireboxes the heat generators. The designs household generators placed directly on the premises, in the last decades, for the goal of commercial appeal, tend become to more and more compact, which leads to a reduction of the firebox to a burn zone’s volume ratio. The numerical study of combustion processes using computational fluid dynamics (CFD) was carried out on the Unimat UT-L18 “Bosch” boiler, the gas heating convector “FEG” Beata 2, and the Vitodens 100-W “Viessmann” boiler. Computations were based on a one-stage combustion process of methane, both mixes with air and oxygen. Geometric models of fireboxes were developed by corresponding to their constructive features, the necessary boundary and initial conditions of furnace processes were determined, temperature, aerodynamic and concentration characteristics of gas fuel combustion processes were also presented. The models provided an opportunity for the quantitative analysis of furnace and burner devices of this heat generators degree of perfections. Also, the completeness of the oxidation of combustible components of the fuel-air mixture in fireboxes, differing in the degree close walls to burn zone, was compared. The obtained results allow to perform the improvement of the furnace and burner devices of domestic heat generators for using at design energy-efficient structures of decentralized heat systems, including individual heat supply in the residential and industrial building.

Innovative building materials in creation an architectural environment

Progressive building materials and technologies can ensure not only the durability of buildings and structures that are operated in difficult conditions and the consumption of a minimum amount of energy with little impact on the environment, but also will contribute to the creation of an effective and harmonious architectural environment in accordance with the requirements of sustainable development. An important role in solving these problems is assigned to recycled (reusable materials); traditional natural and local building materials that due to technical progress have gained new prospects for use in modern environmental and energy-efficient structures and buildings (“old-new” natural materials); nanomaterials and nanotechnologies, the use of which will not only improve the quality and properties of materials, and, accordingly, the environment, but also create completely new materials and architectural solutions with a set of properties. The purpose of this study is generalization, systematization and examination of these innovative materials and products.

Modeling of rational parameters of resistance of heat transfer of building constructions

Today, the issue of improving the level of energy efficiency of existing and construction of new energy efficient buildings is an urgent issue in Ukraine. Improving the energy efficiency of existing buildings is possible due to their thermal modernization, which requires the creation of ways to determine the rational and optimal parameters of the thermal insulation shell of buildings in order to increase the level of energy efficiency of buildings in accordance with modern requirements.Analysis of the studies showed that the thermal balance of translucent and opaque structures of the building depends on the parameters of the spatial orientation (azimuth, slope), the heat transfer resistance and the area of structures. Given the geometric shape and azimuthal orientation of the building, the variable parameters are the heat transfer resistance of opaque and translucent structures. as well as their area.The complex of graphical models for determination of rational (close to optimal) geometric parameters of thermal insulation shell of buildings with consideration of heat losses and heat inflow from solar radiation through fencing structures is developed for use in thermo-modernization of existing buildings and construction of new energy-efficient structures on the level of construction current regulatory requirements.The drawings of the building are used to determine the rational heat transfer resistance and the location of windows on the faces of a faceted building along with the resulting graphic models Rвpi = f (Аσ). In this case, the building plan is combined with the models, and the designer in a dialog mode with the computer determines the rational level of resistance to heat transfer of translucent and opaque enclosing structures.Model analysis confirmed that in all natural and climatic regions of Ukraine, the thermal balance of translucent structures is significantly influenced by heat transfer resistance, the g-factor of glazing, and the orientation of translucent structures.

Numerical study of the effect of the turning angle on heat transfer in multilayered elements of external enclosure structures

When building low-rise buildings with a variety of structural elements, it is important to have an idea of their thermal state in extreme heat exchange conditions. Therefore, the study of heat transfer processes in heat-stressed elements of external fences is relevant and of considerable practical interest. The purpose of this work is to conduct parametric studies in typical angular fragments of inhomogeneous enclosing structures with u-turn angles from 60 to 150°. At the same time, the analysis of the thermal state is carried out for both external and internal angles. The mathematical modeling of spatial heat transfer in the fragments under consideration is based on the solution of a nonlinear system of differential equations of thermal conductivity with corresponding boundary conditions by the finite element method using the Thermal module included in the ANSYS software package. The analysis of numerical results given for three types of enclosing structures made using various technologies allowed us to clarify the influence of their geometric and thermophysical characteristics on the distribution of temperature and heat flow over the thickness of the fragments under consideration, as well as to determine the change in these parameters on both the internal and external surfaces of the structure. To establish that for all types of walling with increasing rotation angle, the temperature in the inner corner of the structure decreases, and in the outer increases, and the density of the heat flow behaves vice versa; the distance from the corner to the area stabilization with increasing angle of rotation reduces, smiling for all types of structures for temperature and heat flow; an increase in the thermal resistance leads to a temperature increase and decrease of the heat flux in the corner tend to be developed fragments; issue recommendations for creating energy-efficient structures that meet modern requirements.

BuildSense

Buildings can achieve energy-efficiency by using solar passive design, energy-efficient structures and materials, or by optimizing their operational energy use. In each of these areas, efficiency can be improved if the physical properties of the building along with its dynamic behavior can be captured using low-cost embedded sensor devices. This opens up a new challenge of installing and maintaining the sensor devices for different types of buildings. In this article, we propose BuildSense, a sensing framework for fine-grained, long-term monitoring of buildings using a mix of physical and virtual sensors. It not only reduces the deployment and management cost of sensors but can also guarantee accurate and fault-tolerant data coverage for long-term use. We evaluate BuildSense using sensor measurements from two rammed-earth houses that were custom-designed for a challenging hot-arid climate so almost no artificial heating or cooling is required. We demonstrate that BuildSense can significantly reduce the cost of permanent physical sensors while still achieving fit-for-purpose accuracy, fault-tolerance, and stability. Overall, we were able to reduce the cost of a building sensor network by 60% to 80% by replacing physical sensors with virtual ones while still maintaining accuracy of ≤1.0°C and fault-tolerance of two or more predictors per virtual sensor.

Methods of synthesis of energy-efficient structures for regulating semiconductor frequency converters

A mathematical model of the power part of the semiconductor converter was developed in this article. The analysis of processes in systems with synchronous electric drives. Experimental and analytical studies have shown that in electric drives with traditional synchronous motors with electromagnetic excitation it is necessary to take into account the influence of winding stray fluxes when setting up a control system. In electric drives with powers exceeding 1000 kW, the effect of leakage fluxes will increase significantly. Experimental methods have established that in multiphase electric drives, when the number of phases is greater than three, the influence of inductive scattering resistance can be neglected, and the mathematical model of the power section of a semiconductor converter is simplified. At the stages of adjustment, it is allowed to approximate the mathematical model of the system by sequential connection of aperiodic links of the first order, the time constants of which are specified during the study of frequency characteristics. The parameters of corrective relationships should also be refined by frequency response methods. Considered recommendations were successfully used in adjusting frequency converters for high-speed objects for LLC “RiK-Energo”.

Network from the circles of the same radius for sustainable energy-efficient roof structures

In this research paper, we investigated one of the methods of formation of geometric networks of arches of the same radius using regular spherical polyhedra. The variants of cutting sustainable energy-efficient coatings of buildings in the form of spherical domes are proposed. The task conditions of placing the specified network on the sphere are set. The criterion for evaluating the effectiveness of solving the problem is the minimum number of standard sizes of segments of the dome arches, the possibility of using pre-assembly technologies. The solution of one variant of the problem as placing the network on a spherical icosahedron and, accordingly, on a sphere is given. The placement of arches of one radius on the sphere, different from the location in the form of meridians, has an effective solution in the form of a network with minimal dimensions of arch segments and with nodes of paired arches comprised on the basis of circles of the same radii formed on the ground of regular spherical polyhedra. The problem is solved by constructing and combining in a system of regular spherical polyhedral with independent frameworks of arches of the same radius on the basis of paired circles of equal radius.

Rapid energy-efficient manufacturing of polymers and composites via frontal polymerization.

Thermoset polymers and composite materials are integral to today's aerospace, automotive, marine and energy industries and will be vital to the next generation of lightweight, energy-efficient structures in these enterprises, owing to their excellent specific stiffness and strength, thermal stability and chemical resistance1-5. The manufacture of high-performance thermoset components requires the monomer to be cured at high temperatures (around 180 °C) for several hours, under a combined external pressure and internal vacuum 6 . Curing is generally accomplished using large autoclaves or ovens that scale in size with the component. Hence this traditional curing approach is slow, requires a large amount of energy and involves substantial capital investment6,7. Frontal polymerization is a promising alternative curing strategy, in which a self-propagating exothermic reaction wave transforms liquid monomers to fully cured polymers. We report here the frontal polymerization of a high-performance thermoset polymer that allows the rapid fabrication of parts with microscale features, three-dimensional printed structures and carbon-fibre-reinforced polymer composites. Precise control of the polymerization kinetics at both ambient and elevated temperatures allows stable monomer solutions to transform into fully cured polymers within seconds, reducing energy requirements and cure times by several orders of magnitude compared with conventional oven or autoclave curing approaches. The resulting polymer and composite parts possess similar mechanical properties to those cured conventionally. This curing strategy greatly improves the efficiency of manufacturing of high-performance polymers and composites, and is widely applicable to many industries.

Sustainability and Conserved Energy Value of Heritage Buildings

Conservation and sustainability have long shared fundamental goals. Heritage buildings are basically sustainable and will continue to be if their sound construction and superior materials are conserved properly. Despite this fact, heritage buildings have gained a reputation for being inefficient and therefore unsustainable in the face of modern, energy-efficient structures. As a result, models which are measured embodied arose to advocate the retention of heritage structures over new constructions. The initial need to measure capital in buildings started due to rising needs to save and address global sustainability goals. Both responses measure overall efficiency of heritage buildings by attempting to account for the energy capital. The life cycle assessment/avoided-impacts model is another model that acts as a response to the evolving metrics and currency of sustainability. The Conservation Green Lab has further developed the capabilities of the life cycle assessment/ avoided impacts model in 2012 in its innovative report: “ The Greenest Building: Quantifying the Environmental Value of Building Reuse”. With this aim, the study applies software models supported by guidelines laid out by LEED, and are consistent with judicious conservation practice on a case study heritage building in Alexandria. The outcome revealed proves that heritage buildings can be both sustainable and efficient while maintaining their historic integrity, when dealt with properly.

USE Efficiency: an innovative educational programme for energy efficiency in buildings

ABSTRACTPower engineers are expected to play a pivotal role in transforming buildings into smart and energy-efficient structures, which is necessary since buildings are responsible for a considerable amount of the total energy consumption. To fulfil this role, a holistic approach in education is required, tackling subjects traditionally related to other engineering disciplines. In this context, USE Efficiency is an inter-institutional and interdisciplinary educational programme implemented in nine European Universities targeting energy efficiency in buildings. The educational programme effectively links professors, students, engineers and industry experts, creating a unique learning environment. The scope of the paper is to present the methodology and the general framework followed in the USE Efficiency programme. The proposed methodology can be adopted for the design and implementation of educational programmes on energy efficiency and sustainable development in higher education. End-of-course survey results showed positive feedback from the participating students, indicating the success of the programme.

Modern Approach to Use of Air Gas Coolers at Compressor Stations

This article provides examples of application of the principle of aggregation of air coolers (AC) for gas cooling and formulates the requirements of an AC. Use of the core component helps find the optimal technical solutions by varying the AC parameters in a wide range. The principle of aggregation helps reduce the installation time maximally and create light energy-efficient structures.

MATHEMATICAL MODEL DEVELOPMENT OF HEAT AND MASS EXCHANGE PROCESSES IN THE OUTDOOR SWIMMING POOL

Purpose. Currently exploitation of outdoor swimming pools is often not cost-effective and, despite of their relevance, such pools are closed in large quantities. At this time there is no the whole mathematical model which would allow assessing qualitatively the effect of energy-saving measures. The aim of this work is to develop a mathematical model of heat and mass exchange processes for calculating basic heat and mass losses that occur during its exploitation. Methodology. The method for determination of heat and mass loses based on the theory of similarity criteria equations is used. Findings. The main types of heat and mass losses of outdoor pool were analyzed. The most significant types were allocated and mathematically described. Namely: by evaporation of water from the surface of the pool, by natural and forced convection, by radiation to the environment, heat consumption for water heating. Originality. The mathematical model of heat and mass exchange process of the outdoor swimming pool was developed, which allows calculating the basic heat and mass loses that occur during its exploitation. Practical value. The method of determining heat and mass loses of outdoor swimming pool as a software system was developed and implemented. It is based on the mathematical model proposed by the authors. This method can be used for the conceptual design of energy-efficient structures of outdoor pools, to assess their use of energy-intensive and selecting the optimum energy-saving measures. A further step in research in this area is the experimental validation of the method of calculation of heat losses in outdoor swimming pools with its use as an example the pool of Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan. The outdoor pool, with water heating-up from the boiler room of the university, is operated year-round.

Special Issue on Sustainable Building Structures

Special Issue on Sustainable Building Structures

Resonance Structure with Magnetic Coupling Windows for Low and Intermediate Energy Linear Ion Accelerators

The results of a comparative investigation of different types of resonance structures for the initial part of low- and intermediate-energy ion accelerators (to 10‐15 MeV) are presented. Numerical modeling of the electromagnetic oscillations is performed. The advantages and disadvantages of the structures studied are noted. A structure with magnetic coupling windows is examined in detail. The mechanism of electromagnetic oscillations in such structures is investigated by means of equivalent circuits. One of the main problems of proton and ion accelerator design remains the development of a compact and energyefficient initial part, which must afford the formation, bunching and acceleration of a beam obtained from an ion source to energy of several MeV/nucleon. The present article examines the possibility of using a unified resonance structure for all sections of the initial part of a linear ion accelerator. Structures based on H-type resonators are energy-efficient structures for the initial part of a linear ion accelerator. They can be divided conventionally into structures operating on quadrupole (four-chamber) and dipole (two-chamber) types of oscillations and structures with electrodes on vertical planar supports. Characteristically, for a conventional four-chamber resonator the quadrupole working and dipole oscillations are not adequately separated. This is especially strongly manifested in long resonators. This is what led to the development of structures with magnetic coupling windows. Resonance Structure with Magnetic Coupling Windows. Windows are cut into the interchamber partitions of

Green buildings need good ergonomics

A retrospective post-occupancy evaluation survey of 44 occupants in two Leadership in Energy and Environmental Design (LEED) Platinum buildings on a US college campus is reported. The Internet survey covered a range of indoor environment and ergonomics issues. Results show that working in these buildings were a generally positive experience for their health, performance and satisfaction. However, in one building there were persistent issues of variability in air temperature, air freshness, air quality and noise that affected the perceived health and performance of the occupants. Although the buildings were energy-efficient and sustainable structures, ergonomics design issues were identified. Implications for the role of ergonomics in green buildings and in the US LEED rating system are discussed. Practitioner Summary: This survey identified a number of ergonomics design issues present in the LEED Platinum energy-efficient and sustainable buildings that were studied. These results highlight the importance of integrating ergonomics design into green buildings as a component in the US LEED rating system.

Energy Efficient Low-Noise Neural Recording Amplifier With Enhanced Noise Efficiency Factor

This paper presents a neural recording amplifier array suitable for large-scale integration with multielectrode arrays in very low-power microelectronic cortical implants. The proposed amplifier is one of the most energy-efficient structures reported to date, which theoretically achieves an effective noise efficiency factor (NEF) smaller than the limit that can be achieved by any existing amplifier topology, which utilizes a differential pair input stage. The proposed architecture, which is referred to as a partial operational transconductance amplifier sharing architecture, results in a significant reduction of power dissipation as well as silicon area, in addition to the very low NEF. The effect of mismatch on crosstalk between channels and the tradeoff between noise and crosstalk are theoretically analyzed. Moreover, a mathematical model of the nonlinearity of the amplifier is derived, and its accuracy is confirmed by simulations and measurements. For an array of four neural amplifiers, measurement results show a midband gain of 39.4 dB and a -3-dB bandwidth ranging from 10 Hz to 7.2 kHz. The input-referred noise integrated from 10 Hz to 100 kHz is measured at 3.5 μVrms and the power consumption is 7.92 μW from a 1.8-V supply, which corresponds to NEF = 3.35. The worst-case crosstalk and common-mode rejection ratio within the desired bandwidth are - 43.5 dB and 70.1 dB, respectively, and the active silicon area of each amplifier is 256 μm × 256 μm in 0.18-μm complementary metal-oxide semiconductor technology.