Heating Schedule Research Articles

Study on Evolution Behavior of Carbides in Industrial‐Grade American Iron and Steel Institute M35 High‐Speed Steel Produced by Electroslag Remelting

In order to optimize the heating schedule before forging and improve the breaking and deformation effects of carbides in high‐speed steel, it is of great significance to study the transformation of M2C carbides at high temperatures. The evolution of carbides in the industrial‐grade American Iron and Steel Institute M35 steel produced by electroslag remelting (ESR) is analyzed and observed using thermodynamic calculations and experimental methods. The results indicate that the carbides in the ESR ingot are mainly MC and M2C, and the microstructures of M2C carbides with the highest volume fraction are lamellar and brain like. As the heating temperature increases and holding time prolongs, the lamellar M2C carbides gradually transform into MC and M6C carbides, accompanied by protrusion, dissolution, separation, and spheroidization of the microstructure, until significant coarsening occurs at 1180 °C for 90 min. The newly transformed carbides are embedded and stacked with each other, occupying the original position of M2C carbides. Based on the theories of Gibbs free energy and atomic diffusion, the evolution mechanism of M2C carbides is discussed. Ultimately, the appropriate heating schedule is proposed, and it is validated by combining the characteristics of carbides after forging.

ASSESSMENT OF THE LEVEL OF ENERGY EFFICIENCY OF A SCHOOL TAKING INTO ACCOUNT THE USE OF LOCAL RENEWABLE ENERGY SOURCES

Energy efficiency is one of the key topics that have become very relevant in recent years. In buildings, as the final consumers of energy, the greatest potential for energy saving is concentrated. And at the same time, an important component of energy efficiency is the optimal use of energy resources, where the lion's share falls on the consumption of thermal energy. In this context, heating schedules become an important tool for achieving this goal. In this article, the authors investigate the energy efficiency of different heating and ventilation modes for a school located in two climatic zones of Ukraine: I (Kyiv) and II (Odesa). Using the Design-Builder software, which is based on the EnergyPlus model, the authors model five intermittent modes for the heating and ventilation system. The authors also compare the energy efficiency of different heat sources: a boiler on biofuel, a heat pump and a solar panel. It was found that the introduction of heating modes according to the schedules allows to reduce energy consumption for heating by 10 % to 20 % depending on the mode and climatic zone, and the use of renewable energy sources based on the introduction of intermittent heating and ventilation modes for the school shows efficiency at 79 %-80 %. The authors also analyze the impact of thermomodernization of enclosing structures on the energy efficiency of buildings. The conclusion on the introduction of intermittent heating modes for non-insulated buildings is an extremely effective measure for energy saving, and the impact of the measure on energy saving of the building will be noticeable even after thermal insulation. The implementation of all improvements allows reducing energy consumption for heating by 90 %.

A multilevel optimization approach for daily scheduling of combined heat and power units with integrated electrical and thermal storage

Renowned for their remarkable overall efficiencies ranging from 70% to 90%, combined heat and power systems stand as a pivotal strategy for optimizing energy consumption by capitalizing on the synergistic relationship between electricity and thermal energy production. However, achieving optimal performance in combined heat and power systems remains a formidable challenge due to the intricate interplay of numerous variables. This paper presents a novel approach to daily scheduling optimization for combined heat and power units, focusing on the integration of electrical and thermal storage systems and meticulous consideration of security constraints. The optimization of combined heat and power unit scheduling introduces a mixed-integer nonlinear programming challenge, replete with deterministic and random variables. Addressing this complexity requires resilient solutions. In this study, we employ a multilevel optimization technique, transforming the problem into a bilevel structure. The initial step involves mapping operating parameters and minimizing costs through a water cycle optimization algorithm, laying a robust foundation for combined heat and power unit operation. Subsequently, we immerse ourselves in the realm of stochastic contingency scenarios, acknowledging the myriad uncertainties inherent in real-world systems. To empirically validate the efficacy of our proposed algorithm, extensive simulations are conducted on IEEE 18-bus and 24-bus test systems that emulate practical power networks. The results unequivocally showcase the power of our approach in navigating the complexities of optimal CHP unit planning. This paper's contributions lie in its innovative multilevel optimization technique, adeptly addressing both deterministic and stochastic aspects, ultimately paving the way for increased energy efficiency and enhanced system reliability in practical applications.

ЕНЕРГОСПОЖИВАННЯ ШКОЛИ В УМОВАХ НЕПОВНОЇ ЗАЙНЯТОСТІ ДЛЯ РІЗНИХ РЕЖИМІВ ОПАЛЕННЯ ПРИМІЩЕНЬ

The challenges facing the Ukrainian education system, particularly in light of demo-graphic changes and the impact of war, are examined in this research. It highlights the poten-tial for optimizing the operation modes of school buildings under conditions of partial occu-pancy to reduce energy consumption and ensure comfortable conditions for students. Energy modeling analysis using DesignBuilder software shows that the configuration of classrooms significantly impacts the energy efficiency of buildings. The best results for energy efficiency were achieved with rooms stacked on top of each other, outperforming the variant with three rooms on the middle floor by 22.3%, and mixed configurations by 8.5% and 16%. This efficiency is due to minimized contact with unheated premises and maximized solar heat gains. However, without appropriate building upgrades, the use of limited spaces may not provide adequate comfort conditions in colder periods. For the rooms studied (45-48m^2), the required heating device capacity to maintain comfortable conditions varies from 7.5 to 10.5 kW, depending on the level of insulation, which is 3-5 times more than the standard capacity for such spaces. Providing comfortable conditions without upgrading the heating system in cold periods is unfeasible, even with high levels of building insulation and a constant heating schedule. Therefore, implementing partial use of school buildings, despite their high potential for en-ergy savings, cannot satisfy student comfort needs without corresponding improvements. Future research could provide a foundation for developing comprehensive strategies for managing school spaces, considering variable building usage conditions and ensuring an optimal combination of energy efficiency, cost-effectiveness, and comfort for students and staff. The findings can be useful for school administrations, local educational authorities, and policymakers in education and energy efficiency. Further studies are suggested to explore the impact of internal wall insulation, increased heating device capacity, and heating uncondi-tioned rooms to a certain temperature level on energy efficiency and comfort conditions in occupied spaces.

Increased Penetration of Renewable Energy using Demand Side Management: Immersion Heater Analysis

This paper examines the potential for Demand Side Management and Dynamic load shifting to increase the theoretical limit imposed on Wind Energy integration. This limit is determined by the financial implications of wind energy curtailment. The following analysis uses the heating schedule of a domestic immersion water heater to show that price driven demand flexibility can increase this limit while offering financial benefits to the consumer. Furthermore, the increased use of wind generated electricity and a minimal increase in overall demand results in reduced consumption of conventionally generated electricity.

Applicability performance evaluation of cascade heat pump for building electrification in winter

This study aimed to evaluate the performance of indoor air heating and domestic hot water supply using a cascade heat pump system. The focus was on using existing heat pump equipment to satisfy system requirements in the context of building retrofitting. The experimental setup was located in nearly net-zero experimental building of the South Korea. The system was configured to heat air in the low-cycle heat pump and supply hot domestic water in the high-cycle heat pump. The study compared three operational modes: a low-cycle-only mode; a hot water-only mode; and a combined mode. While low-cycle-only mode and hot-water-only mode fulfilled the required condition with 3.94–5.38 COP and 60 °C hot water temperature with a flow rate of 15.8 LPM separately, the combined mode failed to reach the target air temperature fulfilling only hot water temperature. In conclusion, the system demonstrated satisfactory performance when heating indoor air and providing hot water separately. However, the indoor heating performance declined when both functions were operated simultaneously. To address this issue, possible solutions could include revising the system operation logic to better align with heating and domestic hot water usage schedules or altering the refrigerant flow path.

Analysis of curing conditions effect on refractory calcium aluminate phosphate cement and concrete hydration (review)

A literature review and analysis of the effect of curing conditions on refractory calcium aluminate phosphate cement and concrete (CAPC) hydration were conducted. It was shown that temperature, as well as H2O requirement, are the most important variables requiring control during the installation of refractory­concrete linings because it influences the sensitivity of these materials to all processing steps including mixing, placement, curing, and heatup. The above requirements have a sequential effect on the service life and performance of a refractory­concrete lining bonded with CAPC; that is, the strength degradation resulting from structural defects caused by improper placement will be amplified by the use of poor curing practices and of nonuniform and excessively rapid heating. The processing variables that must be controlled during installation and initial heatup of CAPC­bonded concretes are H2O requirement; placement method; curing time, temperature, humidity; and heating rate and schedule. It was shown how the resultant hydrated CAP phases contribute to developing hydraulic bonds at ambient temperatures. It emphasizes the correct use of curing, drying, and firing procedures to avoid structural defects relating to the transition of hydrated phases and gels. Permeable crystalline phases are then developed that maximize structural stability and ensure safe heating of monolithic linings. The concretes obtained retain their volume integrity when subjected to prolonged periods of cyclic heating and cooling; can be used for refractory applications at 1700 °C exhibit sufficient strength of lining 40 MPa.

Potential environmental and human health menace of spent graphite in lithium-ion batteries

The growing demand for lithium-ion batteries for portable electronics and electric vehicles results in a booming lithium battery market, leading to a concomitant increase in spent graphite. This research investigated the potential impacts of spent graphite on environmental and human health using standardized toxicity extraction and Life Cycle Impact Assessment models. The spent graphite samples were classified as hazardous waste due to the average nickel content of 337.14 mg/L according to Chinese regulations. Besides, cadmium and fluorine were the other elements that exceeded the regulations threshold. Easily ignored aluminum and heavy metal cobalt are other harmful elements according to the results of Life Cycle Impact Assessments. All the metallic harmful elements mainly exist in a transferable state. Thermogravimetry infrared spectrometry coupled with mass spectrometry was employed to recognize the emitted gases and explore gas emission behavior. Inorganic gases of CO, H2S, SO2, SO3, oxynitride, HCl, and fluoride-containing gases were detected. Sulfur-containing gases released from spent graphite were contributed by the residual sulfuric acid after leaching. The correlation between the evolution of emitted gases and the heating schedule was established simultaneously. The research comprehensively illustrates the pollution of spent graphite and provides assistance for the design of green recycling schemes for spent graphite.

Manufacturing Process of Low‐Contamination Titanium Foam as Implant Material for Cranioplasty Based on Replica Technique

The article investigates the development of a manufacturing route for highly porous titanium foams suitable for craniofacial surgery applications, particularly in cranioplasties. The study focuses on the polyurethane replication method for foam production and emphasizes reducing residual gas content, as it significantly affects the mechanical properties and suitability for approval of the foams. Various factors such as starting materials, solvent debinding, heating schedules, and hydrogen atmosphere are analyzed for their impact on residual gas content. It is shown that significant reductions in residual gas content can only be achieved by reworking each step of the process. A combination of initial solvent debinding of the PU template with dimethyl sulphoxide, reduction of suspension additives, use of coarser Gd. 1 powders, and an integrated debinding and sintering process under partial hydrogen atmosphere achieves a significant reduction in residual gas content. This way, the potential for producing titanium foams that comply with relevant standards for craniofacial implants is demonstrated.

Multi-dimension day-ahead scheduling optimization of a community-scale solar-driven CCHP system with demand-side management

Demand-side management (DSM) can transfer the dynamic fluctuations of load to match the renewable energy sources and realize the interaction of source-load. In most existing combined cooling heating and power (CCHP) system scheduling, user-side and system-side resources are independently optimized to achieve optimum economic performances without efficiently combining resources. In this paper, the devices with adjusted loads on the system-side and the user-side are integrated to construct generalized energy storage (GES) model, including traditional flexible resources, batteries, electric vehicles, cooling and heating load response, and electro-to-thermal conversion devices. Then, the GES model is integrated into the system for optimization including economy, load fluctuation, energy efficiency, and exergy efficiency. A case study demonstrates the application of the proposed method. The scheduling results of four DSM cases under different objectives are comprehensively obtained and compared. The optimized schemes are assessed in multi-dimension decision-making method and the effects of objective weights on decision results are analyzed. The simulation results illustrate that the load variation is decreased by 54% to obtain a smooth electrical load, resulting in the stable operation of equipment and improving the security and stability of the CCHP system. The exergy efficiency, energy efficiency, and economy performances through the DSM optimization are improved by up to 8.7%, 2.5%, and 2.4%, respectively. The system optimized with the objective of load fluctuation achieves the highest score in the TOPSIS decision-making scenarios and has the best comprehensive performance.

Decentralized mixed-integer optimization for robust integrated electricity and heat scheduling

Electric power systems (EPSs) and district heating networks (DHNs) are always independently operated and dispatched but also coupled with each other at the interfaces of combined heat and power (CHP) generation, whereas the existing distributed scheduling methods for the integrated electricity and heat system (IEHS) under uncertainty are computationally expensive in practical applications. To handle this problem, this paper proposes a novel decentralized mixed-integer optimization method for robust coordination involving multiple stakeholders. Firstly, a centralized two-stage robust optimization (RO) scheduling model is installed for the IEHS considering the scheduling economy under the nominal scenario and the adjustment feasibility against uncertainty. Secondly, the Fourier-Motzkin elimination equivalently projects the second-stage feasible region of the two-stage RO scheduling model onto the first-stage optimization, thereby producing a concise centralized RO scheduling model in a mixed-integer linear programming (MILP) formulation. Finally, a dual decomposition algorithm derives the decentralized solution to the resulting MILP-type RO model with guaranteed convergence and optimality. This avoids setting up a coordination center for distributed scheduling. Case testing for two IEHSs validates that the computational efficiency of the proposed method is several tens of times speedup than the traditional distributed RO method with guaranteed solution optimality.

Impact of the Limited Heat Source Capacity on Indoor Temperature and Energy Consumption in Serial nZEB Residential Buildings across the Baltic Region

This paper is dedicated to research of the impact of the limited heat source capacity on indoor temperature and energy consumption in serial nZEB residential buildings. This is an innovative aspect as it explores the potential design simplification for different locations, allowing for cost optimization and quicker construction timelines. The objective of this paper is to examine the impact of limited heat source capacity by utilizing thermal mass and optimizing the ventilation operation. Numerical results demonstrate that incorporating thermal mass increases heating energy consumption by up to 1%. The study addresses the impact of limited heating capacity on indoor temperatures and the need to manage ventilation’s impact during peak temperatures using simulation software IDA ICE. The study reveals that a limited heating capacity reduces energy consumption up to 2.6%, but may result in lower indoor temperatures. By optimizing ventilation strategies, energy consumption can be reduced from 2.4% to 4.4% compared to the suboptimal solution, and from 2.8% to 6.5% compared to the initial case. Parametric analysis reveals optimal ventilation operation change-over point at an outdoor temperature of −17 °C during winter. The research provides practical recommendations for adjusting heating schedules, selecting appropriate heating capacities and implementing optimal ventilation strategies.

Long-term experimental study of price responsive predictive control in a real occupied single-family house with heat pump

The continuous introduction of renewable electricity and increased consumption through electrification of the transport and heating sector challenges grid stability. This study investigates load shifting through demand side management as a solution. We present a four-month experimental study of a low-complexity, hierarchical Model Predictive Control approach for demand side management in a near-zero emission occupied single-family house in Denmark. The control algorithm uses a price signal, weather forecast, a single-zone building model, and a non-linear heat pump efficiency model to generate a space-heating schedule. The weather-compensated, commercial heat pump is made to act smart grid-ready through outdoor temperature input override to enable heat boosting and forced stops to accommodate the heating schedule. The cost reduction from the controller ranged from 2-17% depending on the chosen comfort level. The experiment demonstrates that load shifting is feasible and cost-effective, even without energy storage, and that the current price scheme provides an incentive for Danish end-consumers to shift heating loads. However, issues related to controlling the heat pump through input-manipulation were identified, and the authors propose a more promising path forward involving coordination with manufacturers and regulators to make commercial heat pumps truly smart grid-ready.

Assessment of the thermal energy flexibility of residential buildings with heat pumps under various electric tariff designs

With the electrification of the heating sector in Europe, there is increased pressure to reduce stress to the electric grid from increased demand. Understanding the flexibility potential of the current building stock, including both efficient buildings as well as less efficient buildings, will be vital to assess the efficacy of demand-side strategies such as time-varying pricing in enabling shifts in consumer heat demand.The aim of this study is to assess the thermal flexibility potential of residential buildings with electric heating under different tariffs, and the effect of these tariffs on heating expenditure and electricity consumption. To accomplish this, a resistance–capacitance heat demand model was integrated into a linear optimization model set to find the lowest cost heating schedule for a consumer under four different tariff designs.The results indicate that time-varying tariffs can be effective in enabling shifts in the heat consumption, although the additional cost savings due to the flexibility provided by an efficient building envelope is limited (1% to 4.65% additional reduction in cost savings). The results suggest that potential flexibility is price sensitive and a function of the alignment of price and heating demand. Measures such as capacity tariffs should be considered to avoid preheating surges.

Scenario-based fuel-constrained heat and power scheduling of a remote microgrid

This manuscript suggests elephant clan optimization (ECO) algorithm to solve heat and electric power scheduling of a remote microgrid (MG) for three different scenarios considering fuel constraints. ECO algorithm is a populace-based method motivated by the elephants’ behaviour and their societal organization. MG comprises diesel generators (DGs), small hydro power plants (SHPPs), wind turbine generators (WTGs), solar micro-cogeneration (SMC) unit, biomass-fuel-fired micro-cogeneration (BMC) unit, battery energy storage system (BESS), plug-in electrical vehicles (PEVs) and thermal energy storage system (TESS). BMC units and SMC units are incorporated alternately into the MG. Numerical results of a typical system are compared with those obtained from self-organizing hierarchical particle swarm optimizer with time-varying acceleration coefficients (HPSO-TVAC) and grey wolf optimization (GWO). It is seen from the evaluation that ECO offers superior solution.

DeepValve: Development and experimental testing of a Reinforcement Learning control framework for occupant-centric heating in offices

Space heating controls in offices usually follow static schedules detached from actual occupancy, which results in energy waste by unnecessarily heating vacant offices. The uniqueness of stochastic occupancy profile and thermal response time of each office are two main challenges in hard-programming a transferrable control logic that can adapt space heating schedule to the occupancy profile. This study proposes a Reinforcement Learning-based control framework (called DeepValve) that learns by itself how to adapt the space heating schedule to the occupancy profile in each office to save energy while maintaining comfort. All the aspects of the proposed framework (design, training, hardware setup, etc.) are centered on ensuring that it can be implemented on many offices in practice. The methodology includes three main steps: training on a wide variety of simulated offices with real-world occupancy data, month-long tests on three simulated offices, and day-long experimental tests in an environmental chamber. Results indicate that the agent can quickly adapt to new offices and save energy (40% reduction in total temperature increment) while maintaining occupant comfort. The results highlight the importance of occupant-centric control in offices.

Direct dating of overprinting fluid systems in the Martabe epithermal gold deposit using highly retentive alunite

Abstract. The Martabe gold deposits in Sumatra formed in a shallow crustal epithermal environment associated with intermediate mafic intrusions adjacent to an active right-lateral wrench system. Gas/fluid temperatures reached 200–350 ∘C. The structural geology suggests episodic switches in stress orientations during a Plio-Pleistocene seismotectonic evolution. Different mineralisation events may have been associated with oscillations in this earthquake cycle, so samples containing alunite were collected for 40Ar / 39Ar geochronology to constrain the timing. 39Ar diffusion experiments were performed to constrain variation in argon retentivity. The age spectra were produced by incremental step-heating with heating times chosen so similar percentages of 39Ar gas release occurred during as many steps as possible. This ensured the detail necessary for analysis of the complex morphology of these spectra by applying the method of asymptotes and limits, which enabled recognition of different growth events of alunite in overprinting fluid systems. It was possible to provide estimates as to the frequency of individual events and their duration. The heating schedule also ensured that Arrhenius data populated the inverse temperature axis with sufficient detail to allow modelling. Activation energies were between 370–660 kJ mol−1. Application of Dodson's recursion determined closure temperatures that range from 400–560 ∘C for a cooling rate of 100 ∘C Ma−1. Such estimates are higher than any temperature to be expected in the natural system, giving confidence that the ages represent the timing of growth during periods of active fluid movement and alteration: a hypothesis confirmed by modelling age spectra using the MacArgon program. We conclude that gold in the Purnama pit resulted from overprinting fluid rock interactions during very short mineralisation episodes at ∼2.25 and ∼2.00 Ma.

Study on Hot Tensile Deformation Behavior and Hot Stamping Process of GH3625 Superalloy Sheet

Hot tensile tests of the GH3625 superalloy were carried out under the temperature range of 800-1050 °C and strain rates of 0.001, 0.01, 0.1, 1, and 10 s-1 on a Gleeble-3500 metallurgical processes simulator. The effect of temperature and holding time on grain growth was investigated to determine the proper heating schedule of the GH3625 sheet in hot stamping. The flow behavior of the GH3625 superalloy sheet was analyzed in detail. The work hardening model (WHM) and the modified Arrhenius model, considering the deviation degree R (R-MAM), were constructed to predict the stress of flow curves. The results showed that WHM and R-MAM have good prediction accuracy by evaluating the correlation coefficient (R) and the average absolute relative error (AARE). Additionally, the plasticity of the GH3625 sheet at elevated temperature drops with the increasing temperature and decreasing strain rate. The best deformation condition of the GH3625 sheet in the hot stamping is in the range of 800~850 °C and 0.1~10 s-1. Finally, a hot stamped part of the GH3625 superalloy was produced successfully, which had higher tensile strength and yield strength than the as-received sheet.

A simple methodology based on numerical analysis for the drying curve design of a castable lined steel ladle

Energy efficiency is closely linked to industry goals of reducing environmental impacts, where selecting the best heating curve has a great effect on the total energy consumption, costs, and CO2 emission, especially for refractory castable lining equipment. By using numerical modeling, this work analyses the effects of the temperature and heating rate for thermal treatment profiles comprising a single dwell time. Based on the results attained, a single plateau at 350 °C proved not to be useful for lower thickness castable lining (10 cm) as the resistance ratio peak had already reached high values near the beginning of the dwell time. Increasing the castable wall thickness up to 30 cm requires even more complex profiles than the ones presented. In addition to analysing pressure build-up behavior, this work compared the energy efficiency associated with each of the heating curve cases analyzed, providing a methodology for heating schedule selection.

Crystallization kinetics and structural studies of Li1.25Al0.5Ge1.5P2.75Mo0.25O12 (LAGPM) glass/glass-ceramics based solid state electrolyte

The crystallization kinetics and structural behaviour of Li1.25Al0.5Ge1.5P2.75Mo0.25O12 (LAGPM) glass/glass-ceramics system have been investigated. Glass was prepared by melting the calcined initial charges at 1450 °C using conventional quenching technique. From model free crystallization kinetics, the value of activation energy obtained was 165 kJ mol−1. The nature of nucleation and the dimension of growth of the NASICON crystal were estimated from the kinetics parameters. This glass was converted to glass-ceramics using suitable heat schedule as per DTA data. X-ray diffraction analysis confirmed the formation of desired NASICON phase along with AlPO4 as minor phase. Raman spectroscopy and EXAFS studies showed that molybdenum ions moved to the desired tetrahedral sites in glass-ceramic. The dimension of the crystal growth was clearly seen in SEM image of LAGPM glass-ceramics sample. Impedance spectroscopy was carried out to evaluate the dc ionic conductivity (σdc) of LAGPM glass-ceramics based solid electrolyte. The value of σdc evaluated from the Nyquist plot was found as ∼4.64 × 10−4 S.cm−1 at room temperature.