Energy Balance Concept Research Articles

Study and Analysis thermal performance of Taza gas power plant in Kirkuk –Iraq

In this research, the concept of energy balance was implemented in one of the gas turbine electricity generation units in Iraq (Kirkuk - Taza) K1. The design operating data is taken and compared with the data calculated in the computer model used by Engineering Equation Solutions (EES), and the validity of the model used was confirmed. The results indicate the release of a large amount of thermal energy into the atmosphere due to the open Brayton cycle, as energy losses amounted to 60% of the energy input. The results based on the data of the first unit of the station demonstrated that the theoretical efficiency of the unit is a function of the two variables, which are the temperature of the air entering the compressor and the Turbine inlet temperature: Increasing the compressor inlet temperature leads to a decrease in net power output and first-law efficiency and an increase in the specific fuel consumption rate. Increasing the turbine inlet temperature to 1°C leads to an improvement in both net power output and first-law efficiency by (0.24MW, and 0.04) %), respectively. The results also showed that cooling the air entering the compressor for 1°C leads to improving power output and first law efficiency by (0.72MW, and 0.12%), respectively, and reduces specific fuel consumption by 7.8kg/MWh.

Seismic behavior of CFDST frame with metallic dampers: Damage-controlled design and performance assessment

Current investigations on performance-based seismic design of structures generally employed story drift as performance objectives. However, the story drift could only partially reveal the global damage of a structure and not control the damage of important components. In order to control the damage of various components in a structure, this paper proposed a new damage-controlled seismic design method using the Park & Ang indexes of components. Firstly, the Park & Ang damage index was simplified as an equivalent ductility damage index for various components. The energy balance concept was used to observe the hysteretic energy demand which was subsequently distributed to all stories. Thus, the components of each story could be designed based on their damage indexes under design-based and maximum-considered earthquakes. Four concrete filled double skin tubular (CFDST) moment resisting frames equipped with metallic dampers with various layouts were designed based on the proposed design method. Time history analyses on these four structures were performed after validating the accuracy of nonlinear model by Opensees. Analysis results showed that the components in four structures exhibited expected damage states as illustrated by the design method. It also verified that proposed seismic design method was effective to control the damage of various components, which was beneficial for protecting the important components in a structure by setting low damage indexes for them. The seismic design method and analysis results also provided a reference for the design of moment resisting frame with energy devices.

A novel approach for quantifying dynamic impacts on steel frames induced by instantaneous interior column loss

This research presents an innovative approach to accurately quantify dynamic impacts on the steel frame structure resulting from the instantaneous loss of an interior column. This methodology effectively calculates the dynamic amplification factor (DAF) when the steel frame reaches its collapse limit state and predicts the structure's deformation under such a scenario. Central to this approach is the conversion of the static load-deformation curve, pertinent to a scenario of interior column loss, into a dynamic force load-deformation curve using the concept of energy balance. A comprehensive parametric analysis was conducted to study how different structural parameters, such as beam depth, span, slab thickness, rebar diameter, and slab aspect ratio, affect the enhancement factor (i.e., the ratio of collapse resistance to yield resistance). A pragmatic formula for determining enhancement factor was subsequently suggested. Moreover, this study delved into how these structural parameters influence the dynamic amplification factor at the collapse state, revealing a notable dependency of dynamic amplification factor on the slab aspect ratio that an increasing aspect ratio correlates with a rising dynamic amplification factor trend. The manuscript also presented a detailed methodology for computing the dynamic deformation of frame structures in the event of an instantaneous interior column loss. The results of the case study show that the proposed method closely matches the accuracy of numerical analyses, with differences falling within a 15% range.

Carbon solute drag effect on the growth of carbon supersaturated bainitic ferrite: Modeling and experimental validations

The carbon partitioning and lengthening rate of bainitic ferrite (αb) are excellent experimental parameters to estimate our level of understanding of the mechanism of bainitic transformation from a continuum perspective and our ability to capture it in analytical expressions. For Fe-C alloys and relatively simple steels the classical Zener-Hillert theory captures the bainitic transformation rather well but mispredicts the level of carbon in solution in the bainite and overestimates the lengthening rates for transformations at lower temperatures. To address this issue, this paper presents a new thermo-kinetic model based on the Zener-Hillert theory and the Gibbs energy balance concept to simulate the lengthening behavior of αb in the Fe-C and low alloyed steels. The model incorporates the effect of the temperature dependent carbon diffusion within the migrating interface via a temperature dependent ferrite/austenite interfacial energy and a temperature dependent diffusion coefficient but does not impose local equilibrium across the interface. The good agreement between the model predictions and nine sets of published experiments indicates that both the carbon supersaturation in αb and the slower lengthening rate are caused by carbon diffusion within the migrating interface. It is found that the degree of carbon supersaturation in αb increases significantly with decreasing temperature. Consequently, the enhanced carbon solute drag effect, resulting from carbon diffusion within the interface, strongly retards the lengthening rates of αb at lower temperatures. Transformation strain is shown to have a modest effect on the lengthening rates but to lower the degree of carbon supersaturation.

Displacement Control of Existing Steel Moment-Resisting Frame Structures Using Buckling-Restrained Braces

ABSTRACT Large displacements are expected to occur in existing code-compliant steel moment-resisting frames during a severe earthquake, affecting the functionality of buildings. This study investigated the use of buckling-restrained braces for controlling the displacement response and ensuring an occupiable performance level of the structures. A design procedure for the braces based on the energy balance concept is proposed, where the hysteretic energy demand of the frame before and after attaching the braces is equated. Time-history analysis results show structures designed using the proposed procedure satisfied the targeted performance level, and no significant change in peak floor acceleration response was observed.

Longitudinal seismic displacement analysis of Quasi Seismic Isolation Bridge based on Energy-based Multimodal Pushover Method with and without collision

This paper aims to evaluate the longitudinal seismic displacement of the Quasi Seismic Isolation Bridge (QSIB) based on the Energy-based Multimodal Pushover Method (EMPM), including the pier-beam relative displacement and the collision effect. As a simplified seismic analysis method, the EMPM invokes the concept of energy balance into the modal pushover analysis to assess the nonlinear seismic behavior of Laminated Rubber Bearing (LRB) on bridges. In this method, the energy-based capability curve is obtained by the modal pushover analysis, while the energy-based demand curve is estimated under the ground motion record. The target performance criterion can be derived by intersecting the capability curve with the demand curve. The effect of several key factors in EMPM, such as the mode classification and selection, collision effect, energy coefficient and ductility factor, are studied by a case study of a prototype QSIB under ChiChi and El Centro earthquakes. The results of EMPM are compared with those from Nonlinear Time History Analysis (NTHA), to illustrate the effectiveness and accuracy of this method for evaluating the maximum seismic displacement, and the pier-beam relative displacement with and without collision. Results show that the EMPM is found to be able to estimate the longitudinal seismic displacement of the QSIB with and without collision, and can be used as an effective alternative for rapid assess the seismic performance of bridges. The results also indicate that LRB stiffness for modal analysis should be taken as the stiffness pre- or post-sliding when without or with the gap element. Collision effect enlarges the peak displacement and the maximum bias of EMPM.

Energy assessment of a district by integrating solar thermal in district heating network: a dynamic analysis approach

This work focuses on the energy upgrade of a neighbourhood located in Yverdon-les-Bains, Switzerland. Starting from a potential low-temperature district heating network, the possible integration of new buildings equipped with solar thermal collectors capable of interacting with the network is explored. The methodology proposed in this work focuses on the study of the energy balance of the district at reduced time intervals. Bringing the level of detail to every single hour of the year, the concept of energy balance is superseded by the hourly averaged power balance as a specific tool for a detailed exploration of the energy flows exchanged within the district. Self-sufficiency has also been identified as key performance indicators to better understand the ability of the entire district to satisfy its heating and domestic hot water needs, modelled in CitySim’s urban energy environment. The outcomes have shown that an annual energy balance is ineffective and unrealistic for describing performances of the district. On the other hand, the hourly averaged power balance proves to be a powerful tool for understanding the dynamics of the neighbourhood. The district’s energy flexibility, which relies on energy sharing, is a characteristic that cannot be assessed annually. Using the new proposed methodology to evaluate the district’s thermal energy sharing, it was discovered that the district functions as a Zero Energy District for 28.9% of the year. With the outcomes presented in this study, it is now possible to comprehend how a dynamic performance assessment positively impacts a district’s redevelopment strategies.

Performance-based plastic design of high-strength steel framed-tube structures fused with replaceable shear links

This study proposes high-strength steel framed-tube structures fused with replaceable shear links (HSS-FTSLs) to improve the seismic performance and post-earthquake reparability of traditional steel framed-tube structures. The conventional seismic design commonly uses the capacity design method, which primarily focuses on the ductility of the structures, resulting in localized damage concentrated on individual floors. An improved performance-based plastic design (I-PBPD) method is proposed for HSS-FTSLs based on the energy balance concept, target drifts, and preselected failure mechanisms. The proposed I-PBPD method considers the influence of post-yield stiffness of the structures. The seismic performance objectives for HSS-FTSLs are categorized into four levels, accompanied by the interstory drifts and residual interstory drifts corresponding to these objectives. The capacity curve for HSS-FTSLs is assumed as a tri-linear form to correspond with the failure modes. Three HSS-FTSL prototype structures with various heights are designed through the I-PBPD method. Nonlinear pushover and dynamic analyses were carried out to investigate their seismic performance. The results indicate that the HSS-FTSL structures designed using the I-PBPD method can achieve the expected failure modes and performance objectives under earthquakes of varying intensities, exhibiting exceptional seismic performance.

An efficient energy-based methodology for seismic collapse assessment of steel moment frame buildings

PurposeNonlinear dynamic analyses are employed for seismic collapse risk evaluation of existing steel moment frame buildings. The standards, such as ASCE 41-17, often define collapse thresholds based on plastic deformations; however, the collapse process involves several factors, and plastic deformation is only one of them. An energy-based approach employs deformation and resistance responses simultaneously, so it can consider various factors such as excessive deformation, stiffness and resistance degradation, and low-cycle fatigue as cumulative damage for seismic assessment. In this paper, an efficient energy-based methodology is proposed to estimate the collapse threshold responses of steel moment frame buildings.Design/methodology/approachThis methodology uses a new criterion based on the energy balance concept and computes the structural responses for different seismic hazard levels. Meanwhile, a pre-processing phase is introduced to find the records that lead to the collapse of buildings. Furthermore, the proposed methodology can detect failure-prone hinges with a straightforward probability-based definition.FindingsThe findings show that the proposed methodology can estimate reasonably accurate responses against the results of the past experiment on the collapse threshold. Based on past studies, ASCE 41-17 results differ from experimental results and are even overly conservative in some cases. The authors believe that the proposed methodology can improve it. In addition, the failure-prone hinges detected by the proposed methodology are similar to the predicted collapse mechanism of three mid-rise steel moment frame buildings.Originality/valueIn the proposed methodology, new definitions based on energy and probability are employed to find out the structural collapse threshold and failure-prone hinges. Also, comparing the proposed methodology results against the experimental outcomes shows that this methodology efficiently predicts the collapse threshold responses.

Synchronizing Teaching Resources of Energy Conservation Principle in Mechanical Engineering Courses- Year 2 Updates

The conservation of energy, mass, and momentum are three governing laws of physics that are regularly uttered in teaching engineering courses. Mechanical energies in the form of kinetic and potential forms are the most common forms of energy in dynamics. Fluid flow energies relating to pressure, velocity, elevation, fluid friction, pump, and turbine are covered in fluid dynamics. In thermodynamics course, the first law deals with heat energy and work that can alter internal energy in a system. In all these courses, the conservation of energy states that the amount of energy remains constant, that means that energy is neither created nor destroyed but transferable from one form to another, keeping the total energy same within a fixed domain. Students are initially exposed to energy balance equation in their first Thermodynamics course. In this course, emphasis is placed upon those parameters of specific interest related to energy to this subject. We attempted to tie the concepts of the energy balance equation through 1st Law in thermodynamics to those emphasized in Fluid Mechanics. This was accomplished by taking the students from the starting point of the thermodynamics’ first law for Energy Balance equation to the finished Fluid Mechanics’ Bernoulli’s equation. In the following semester, students were again taken through the process of converting the 1st Law of thermodynamics to Bernoulli’s equation of fluid mechanics. Direct and indirect assessments were then conducted to measure students’ understanding on the energy and its conservation. Through a series of questionnaire and their feedback, Students were found to be more knowledgeable in the conservation of energy through the synchronization of energy balance concepts in these two courses. This presentation is a part of work-in-progress project that we first presented at 2022 WVAS meeting.

Developing machine learning models for wheat yield prediction using ground-based data, satellite-based actual evapotranspiration and vegetation indices

Timely and accurate crop yield estimation is important for adjusting agronomic management and enseuring agricultural sustainability. Machine learning (ML) algorithms provide new opportunities to integrate agronomic information with ground-based and satellite data and develop flexible yield predictive models. In particular, satellite-based vegetation indices and evapotranspiration provide robust proxies for crop yield estimations in the absence of measurements; nevertheless, most prior model development efforts have focused on using only vegetation indices due to the simplicity of the process. Additionally, the contribution of input categories (i.e., field, meteorological, and satellite data) and the use of appropriate proxies, aligned with the crop growth stages, in developing yield predictive models have not been adequately investigated. To address these challenges, we employed two ML techniques, Random Forest (RF) and extreme gradient boosting algorithm (XGB), to estimate wheat yield using meteorological variables, satellite-driven actual evapotranspiration (ETa), and vegetation indices (VIs). ETa was separately computed using the surface energy balance concept and the METRIC model. The models were first trained and tested in the study area using three input combinations: i) meteorological variables, ii) satellite data, and iii) an ensemble of meteorological and satellite data. Then, the best-performing model was further evaluated using two independent datasets. We found ETa to be particularly important in improving the accuracy of the model predictions. Among the vegetation indices, EVI, EVI2, and NDVI during May, and among the meteorological data, growing degree days during the grain filling stage plus minimum temperature in the stem elongation stage had the highest contributions to yield predictions. Both ML algorithms generated relatively accurate results, where XGB was marginally more accurate than RF, considering an average mean absolute error of 0.39 t ha-1 for XGB and 0.50 t ha-1 for RF. Normalized root-mean-square errors of the ensemble, satellite-derived and meteorological-derived models in XGB were 0.05, 0.07, and 0.10, respectively. Nevertheless, both algorithms’ performances deteriorated in predicting the yield values beyond the range of the training set, though XGB could handle the extrapolation process more efficiently than RF.

Experimental and analytical modeling for channel profile using CO2 laser considering gaussian beam distribution

This research aims to examine the impact of laser power and scanning speed on channel depth and profile using a high-power 100 W CO2 laser machine in continuous mode. The work is carried out in two stages. The first stage maintains a 50 W fixed power while varying the speed from 25 to 200 mm/s. and channel profiles are created. In the second stage, 50 mm/s laser scanning speed is kept constant while power is varied from 30 W to 60 W, and channel profile is created. An analytical model is developed considering the three-dimensional coordinate effect and concept of energy balance along with the energy of conduction. The proposed model is validated through experimental work. Finally developed analytical model is compared with the models available in the literature. The highest prediction error was found to be 1.68%, while, for constant 50 W power and 25–200 mm/s of speed, the average prediction error was determined to be 1.18%. As a result, the proposed model closely matches the experimental findings, and the proposed model can be used to estimate channel profile.

Calculating fire danger of cured grasslands in temperate climates – the elements of the Grassland Fire Index (GLFI)

Background Increasing extreme weather events due to climate change require updated environmental monitoring and prediction systems in Germany. Aim The Grassland Fire Index (GLFI), developed by the German Meteorological Service ~15 years ago for temperate climates, was revised to improve fire-danger predictions during the fire season. Our paper gives insight into the new model version. Methods The former fire-behaviour core, i.e. Fosberg’s Fire Weather Index (FWI), is replaced by the standardised fire-reaction intensity, a different fuel-moisture of extinction term, and a replica of the fire-spread rate of the Canadian FFBP-System. A standardised ease-of-ignition index is added as a measure of ignition success. The fire module is supplied with diurnal dead-grass fuel-moisture calculations based on the water-budget and energy-balance concept. Key results The GLFI output is compared with diurnal fuel-moisture measurements and results of Wotton’s Grass-Fuel-Moisture model, Fosberg’s FWI, and Cheney’s rate of spread equation. The GLFI computes periods with a high fuel moisture more realistically, whereas it exceeds Cheney’s rate-of-fire spread systematically at lower wind speeds, which leads to higher danger ratings during calm-air conditions (as requested by users). Conclusions and Implications The GLFI estimates dead-fuel moisture and fire danger on open, horizontal topography according to the current scientific level. Model extensions are necessary to run the model on complex topography under varying greenness and occasional frost conditions.

A Modular Co-assembly Strategy for Ordered Mesoporous Perovskite Oxides with Abundant Surface Active Sites.

The ordered mesoporous perovskite oxides with well-defined mesostrcture and versatile metal sites are attractive, but their successful synthesis faces challenges of complicated assembly dynamics and pore collapse in crystalline calcination. Here, we propose an energy balance concept to reveal interplay relationship in assembly process and realize regulation of porous structure for mesoporous perovskite oxides. A series of ordered mesoporous perovskite oxides with unique porous structure were prepared by a modular co-assembly method. Mesoporous La2 Zr2 O7 shows 94 % conversion and 99 % selectivity for hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan. Experiments reveal that rich Lewis acid sites, active Zr species, and favorable porous structure promote interaction between mesoporous La2 Zr2 O7 and HMF and reduce catalytic energy barrier. This work provides the insight into molecule co-assembly and developing multiple component ordered mesoporous materials.

A Modular Co‐assembly Strategy for Ordered Mesoporous Perovskite Oxides with Abundant Surface Active Sites

AbstractThe ordered mesoporous perovskite oxides with well‐defined mesostrcture and versatile metal sites are attractive, but their successful synthesis faces challenges of complicated assembly dynamics and pore collapse in crystalline calcination. Here, we propose an energy balance concept to reveal interplay relationship in assembly process and realize regulation of porous structure for mesoporous perovskite oxides. A series of ordered mesoporous perovskite oxides with unique porous structure were prepared by a modular co‐assembly method. Mesoporous La2Zr2O7 shows 94 % conversion and 99 % selectivity for hydrogenation of 5‐hydroxymethylfurfural (HMF) to 2,5‐bis(hydroxymethyl)furan. Experiments reveal that rich Lewis acid sites, active Zr species, and favorable porous structure promote interaction between mesoporous La2Zr2O7 and HMF and reduce catalytic energy barrier. This work provides the insight into molecule co‐assembly and developing multiple component ordered mesoporous materials.

Evapotranspiration Acquired with Remote Sensing Thermal-Based Algorithms: A State-of-the-Art Review

Almost fifty years have passed since the idea to retrieve a value for Evapotranspiration (ET) using remote sensing techniques was first considered. Numerous ET models have been proposed, validated and improved along these five decades, as the satellites and sensors onboard were enhanced. This study reviews most of the efforts in the progress towards providing a trustworthy value of ET by means of thermal remote sensing data. It starts with an in-depth reflection of the surface energy balance concept and of each of its terms, followed by the description of the approaches taken by remote sensing models to estimate ET from it in the last thirty years. This work also includes a chronological review of the modifications suggested by several researchers, as well as representative validations studies of such ET models. Present limitations of ET estimated with remote sensors onboard orbiting satellites, as well as at surface level, are raised. Current trends to face such limitations and a future perspective of the discipline are also exposed, for the reader’s inspiration.

New precast self-centering rocking shear wall with multiple hinged joints: Description and design approach for seismic protection of buildings

This paper proposes a novel precast self-centering shear wall with multiple hinged joints (PSCSWMHJ) as an alternative seismic resilient system, which is composed of pinned precast walls, pre-compressed disc spring devices (PDSD) and self-centering energy dissipation braces (SCEDB). It is featured by a dual self-centering system with the PDSD-wall component and the SCEDB resisting lateral loads. Seismic energies are expected to be mainly dissipated by S-shaped steel plate dampers installed in the SCEDB, while the precast walls are protected from damages. The damper is characterized by flexure-tension strengthening behavior that is beneficial to control structural displacement under strong earthquakes, and its seismic performance has been experimentally and numerically studied. The main objective of this study is to investigate rocking mechanism and seismic resilient design method for the PSCSWMHJ. In present study, mechanic models for the PDSD and the SCEDB are presented, and the SCEDB's hysteretic behavior is analyzed through numerical parametric studies. Rocking mechanism for the PDSDS-wall component and the PSCSWMHJ are theoretically revealed and numerically validated. Meanwhile, the influence of design parameters on their hysteretic behavior is discussed. The results show that the PSCSWMHJ has flag-shaped hysteretic curve and most of the energy is dissipated by dampers in the SCEDB. Subsequently, the step-by-step design procedure is proposed on the basis of energy balance concept for realizing seismic resilience of the PSCSWMHJ. Nonlinear dynamic analyses indicate that the design procedure is capable of achieving the expected performance objectives and the pre-selected yielding mechanism; the proposed PSCSWMHJ exhibits excellent self-centering capacity and good functional recoverability.

Modern trends in the development of nuclear power: from environmental friendliness to safe utilitarianism

The article discusses the issues of sustainable development of the energy sector of the world economy in accordance with the Sustainable Development Goals: from the active dissemination of clean and environmentally friendly, so-called "green" technologies and technological processes to a significant increase in the share of energy produced from renewable energy sources (RES) by 2030 in the global energy balance and green economy concepts determines the choice of safe types of energy, which, along with renewable energy sources, include nuclear power in accordance with the principle of no significant harm. The Russian Federation ranks fourth in terms of the amount of electricity produced in the world and second, after France, among European countries in terms of nuclear generation capacity. The main trends in the development of the Russian nuclear power industry are presented. It was revealed that the nuclear power industry of the Russian Federation, producing up to 20% of the total energy, ensures compliance with the environmental safety of territories and the safe utilitarianism of radiation technologies in the civilian sector of nuclear energy (nuclear medicine, decontamination of pollution, wastewater treatment, non-destructive testing, radiation materials science, food processing products by ionizing radiation in specialized radiation centers, etc.).

Performance based design of a new hybrid passive energy dissipation device for vibration control of reinforced concrete frames subjected to broad-ranging earthquake ground excitations

This paper evaluates a new hybrid passive device that comprises two different passive energy dissipation categories, namely, viscoelastic damper and friction damper. The device operates as a synergic unit using a novel locking mechanism. The hybrid passive device offsets the drawbacks of individual devices and facilitates improving the performance of structures for multiple excitation vibration levels due to wind and seismic events. Both devices are connected in a parallel combination using locking mechanisms and exhibit distinct hysteretic characteristics under small and significant deformation. The viscoelastic damper alone will be activated for extreme winds and minor to moderate earthquakes, and both devices will work simultaneously for strong earthquakes. Considering the advantages of such a new device, this article presents a new seismic design method structures equipped with a hybrid passive dampers device using the energy-balance concept. The method accounts for the structural member's inelastic behaviour, phase transformation of the stiffness and the energy dissipation capacity of the energy devices to achieve the intended performance level under the design earthquake hazard. The proposed method has been applied on a six- and a twelve-storied reinforced concrete building. The seismic performance is verified through nonlinear time history analysis using a set of near and far-field ground motions. Numerical results are investigated in terms of the inter-story drifts, the residual drifts, the floor acceleration and the yield mechanisms. The structure's performance corresponds well with the target performance levels.

Construction of a Simple Domeless Net Radiometer for Demonstrating Energy Balance Concepts in a Laboratory Activity

Even though energy balance concepts are fundamental to solutions of problems in a number of disciplines in the agricultural and life sciences, they are seldom demonstrated in a laboratory activity. Here, we introduce a simple domeless net radiometer to demonstrate how the surface temperature of an object aboveground is regulated by the properties of the surfaces and environmental conditions. The device is based on the early designs of all-wave net radiometers and is composed of a foam disc with its opposing surfaces coated with either white or black paint. Temperatures of the disc’s surfaces are monitored using thermocouple temperature sensors. Using a combination of solar irradiance, albedo of the ground surface, air temperature, and wind speed measurements, the temperatures of the disc’s surfaces can be calculated by means of an energy balance model. We found good agreement between calculated and measured temperatures. In addition to demonstrate important physical concepts under natural outdoor conditions, we believe that the proposed laboratory activity will benefit students by allowing them to gain some experience and practical skills in working with environmental sensors, programming data acquisition systems, and analyzing data. Stimulating students’ creativity as well as developing their analytical and problem-solving skills is another goal of the proposed activity.