Thermal Load Research Articles

Investigations on Microstructure, Mechanical, and Wear Properties, with Strengthening Mechanisms of Al6061-CuO Composites

Metal matrix composites (MMCs) reinforced with Copper Oxide (CuO) and Aluminum (Al) 6061 (Al6061) alloys are being studied to determine their mechanical, physical, and dry sliding wear properties. The liquid metallurgical stir casting method with ultrasonication was employed for fabricating Al6061-CuO microparticle-reinforced composite specimens by incorporating 2–6 weight percent (wt.%) CuO particles into the matrix. Physical, mechanical, and dry sliding wear properties were investigated in Al6061-CuO MMCs, adopting ASTM standards. The experimental results show that adding CuO to an Al6061 alloy increases its density by 7.54%, hardness by 45.78%, and tensile strength by 35.02%, reducing percentage elongation by 40.03%. Dry wear measurements on a pin-on-disc apparatus show that Al6061-CuO MMCs outperform the Al6061 alloy in wear resistance. Al6061-CuO MMCs’ strength has been predicted using many strengthening mechanism models and its elastic modulus through several models. The strengthening of Al6061-CuO MMCs is predominantly influenced by thermal mismatch, more so than by Hall–Petch, Orowan strengthening, and load transfer mechanisms. As the CuO content in the composite increases, the strengthening effects due to dislocation interactions between the matrix and reinforcement particles, the coefficient of thermal expansion (CTE) difference, grain refinement, and load transfer consistently improve. The Al6061-CuO MMCs were also examined using an optical microscope (OM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) before and after fracture and wear tests. The investigation shows that an Al6061-CuO composite material with increased CuO reinforcement showed higher mechanical and tribological characteristics.

Exploring Biomaterial-Based CoolRoofs: Empirical Insights into Energy Efficiency and CO2 Emissions Reduction

The Cool Roof concept, known for its efficiency in summer due to high temperatures during this period, employs a light coating that covers the roof to prevent the absorption of heat and maintain lower indoor temperatures. This study integrates a chemical component with biomaterials to enhance performance and reduce CO2 emissions. The composition investigated in this research is recognized for its durability and ability to lower outside temperatures, thereby mitigating the urban heat island effect. This experimental study evaluates the sustainability of CoolRoofs in a cold room located in Signes, France. Temperature measurements are conducted from 25 September 2023 to 27 July 2024, both with and without the coating, to assess energy performance and CO2 emissions. The selection of the building type ensures optimal performance in both summer and winter. Results show that the maximum outside and inside surface temperatures for a Cool Roof are 48.7 °C and 25.6 °C, respectively, compared to 72.9 °C and 32.2 °C for an uncoated roof. Additionally, implementing a CoolRoof reduces thermal load through the cold room by 56%, while CO2 emissions can be reduced by up to 27.31 kg CO2/m2 over a 20-year period. This study presents a solution for enhancing energy and environmental performance year-round using a resilient composite.

Principles of ensuring thermal stability in innovative technology of periclase-spinel refractories

This article presents the results of research on the structural-phase regularities and behavior of periclase-spinel refractories under high-gradient thermal loads. The findings from the analysis of structural-phase variability in the refractory samples are used to achieve the desired thermal resistance. Based on the investigation of the subsolidus structure of the MgO–FeO–Al2O3–TiO2 system, predictions were made regarding the characteristics of solid-phase exchange reactions, considering the existence of solid solutions with various types of crystal structures in specific areas of the system. This enabled the application of new principles for ensuring thermal stability in the developed periclase-spinel refractories, specifically through organizing a fragmented, micro-cracked structure by combining solid-phase exchange reactions with the establishment of mobile equilibrium upon reaching stationary-state temperatures. An additional feature is the possibility of phase invertibility of solid spinel solutions, including changes in the type of spinel structure, in particular quandilite. Physicochemical research methods confirmed the enhanced ability of the material to flexibly adapt its phase composition and microstructure to thermal loads. The feasibility of these principles for achieving the structural-phase adaptability of the material to thermal shocks was validated by electron microscopy analysis.

The Role of Thermal Analysis in Engine Fin Design: Insights and Perspectives

Objective: The study aims to address the significance of fins in enhancing the heat transfer rate of engine cylinders and highlight their applications and advancements in various fields. Methods: Thermal analysis of fins using ANSYS Workbench is an invaluable tool for engineers and researchers in determining and optimizing the heat transfer characteristics of finned structures. ANSYS Workbench provides a comprehensive platform for evaluating the performance of fins in various applications using simulations of computational fluid dynamics (CFD) and finite element analysis (FEA). With ANSYS Workbench, it is possible to assess the thermal behaviour of fins under a variety of conditions, such as variable boundary conditions and thermal loads. Some significant recent patents on Engine fin are also discussed in this review article. Results: Fins are designed to maximize contact with the surrounding air or coolant, thereby facilitating engine heat transfer to the surrounding environment. Engineers can enhance heat dissipation capabilities by considering parameters such as fin geometry, density, material selection, and manufacturing techniques while minimizing associated drawbacks. Conclusion: The numerous applications of fins highlighted in this review article will encourage researchers to find novel strategies to improve heat transfer by employing fins for use in a variety of sectors.

Discontinuous Pulse Width Modulation Strategy for Single-phase Five-level T-type NPC Inverter considering Symmetric Thermal Loadings of Power Devices

Discontinuous Pulse Width Modulation Strategy for Single-phase Five-level T-type NPC Inverter considering Symmetric Thermal Loadings of Power Devices

Evaporator Evaluation as a Heat Exchanger in Refrigeration Systems at Constant Thermal Load and Fouling Factor

Heat exchangers are widely used in various industrial installations, one of which is their use in air conditioning systems. In the design process of heat exchangers, the main focus is to determine the dimensions of the device. This is done to determine the performance of the heat exchanger, where the calculation is based on a constant thermal load and a constant fouling factor. When the heat exchanger is first operated, the mass flow rate of the cooling fluid must be lower than the design point to maintain a constant cooling load. However, the conditions for the formation of deposits on the surface of the heat exchanger cannot be known. Therefore, designing a heat exchanger with a constant fouling factor is less realistic.

Mechanical Properties of Novel Hybrid Bamboo Fibre/Aluminium Mesh Reinforced Polymer Composite

Bamboo fibres are one of the sustainable lignocellulosic resources explored for polymer composites in recent years. Research has shown that bamboo fibres have the potential to be used in a variety of critical applications. Nevertheless, bamboo fibres are susceptible to thermal and hygroscopic loads, and their mechanical properties are limited by the unequal interfacial strength and varying fibre dimensions. Implementing hybrid procedures or incorporating alternative materials, such as aluminium metal, is strongly advised to address this issue. Thus, this study investigates the tensile and flexural performances of the hybrid bamboo fibre/aluminium expanded mesh-reinforced polymer composites. The composites were fabricated using epoxy resin reinforced with bamboo fibre, and an aluminium expanded mesh sheet was constructed using a vacuum infusion process utilising various stacking sequences and mesh sizes. The test findings indicated that the composite material exhibited tensile stress values ranging from 27 to 34 MPa and a corresponding tensile strain value between 1.1% and 1.6%. The flexural strength and strain values were measured within the range of 44 Mpa to 59 Mpa and 2.2% to 3.2%, respectively. ANOVA analysis showed that both stacking sequences and mesh size significantly affected the tensile performances of the composites, while only stacking sequences affected the flexural performance significantly. Overall, a hybrid composite of bamboo fibre and aluminium mesh is well-suited as a substitute material in industries requiring exceptional mechanical properties.

EFFECT OF CERAMIC MATRIX COMPOSITES ON THE THERMAL EFFICIENCY OF A POWER GENERATION TURBINE

Abstract Ceramic Matrix Composites (CMCs) offer higher allowable temperatures and reduced weight, making them an attractive prospect for parts in the hot section of a gas turbine engine. As CMCs are increasingly adapted into aero and land-based engines, there is a need to quantify the performance increase based on potential for reduced cooling and increased firing temperatures. In this work, two hot section components – the first stage turbine vane and tip shroud (outer casing above the blade) - of a mid-sized power generation engine were modeled. Informed approximations about part geometry and cooling architectures were made to determine cooling requirements of each part. Thermal boundary conditions for the turbine tip shroud and turbine vane were generated as a function of coolant mass flow rate using data from literature and applied to a 2D finite element analysis model to determine maximum temperatures for both metallic and ceramic materials. A gas turbine cycle model was developed to simulate the performance of a mid-sized power generation turbine, and used to determine increase in efficiency due to reduction in cooling requirement for the CMC part. Potential reduction in chargeable cooling seen for the tip shroud was between 0.09% and 0.4% of the compressor mass flow rate, which corresponds to an increase in thermal efficiency between 0.11% and 0.45%. A similar analysis of the turbine vane resulted in a cooling reduction of 10.71% at the maximum thermal load considered which corresponds to a 3.4% increase in thermal efficiency.

Post fire flexural behavior of mild steel based cold-formed built-up beams exposed to elevated temperature

The use of back-to-back built-up channel beams in cold-formed steel (CFS) structures is steadily rising. The growing demand for CFS sections as a cost-effective design solution has driven the development of these CFS built-up sections. Despite this, there has been limited research on the performance of mild steel (MS) based CFS at high temperatures, particularly regarding its flexural behavior. This study thoroughly explores the behavior of MS-based CFS beams with different spans under high temperatures, followed by cooling with air or water. It assesses the impact of thermal loading and evaluates the effectiveness of these cooling methods. Experimental findings are validated and analyzed in conjunction with Finite Element Modeling (FEM) using ABAQUS and the Direct Strength Method (DSM). The study also conducts a parametric analysis to determine how the varying span that affects flexural capacity of beam. Among beams heated to the same temperature, those cooled with water exhibit slightly lower load capacities than those cooled with air. The maximum load observed is 91.21 kN for the reference specimen, while the minimum load is 39.82 kN for the specimen heated for 90 min and cooled with water, resulting in a 78.45% difference between these values. Additionally, as heating duration increases, ductility of beam also increases. Various failure modes are observed based on different heating and cooling conditions across different beam spans. This study offers valuable insights into the performance of MS-based CFS beams under thermal stress and different cooling conditions, providing important data for structural design and safety in construction.

A PROBLEM IN FRACTIONAL ORDER THERMO-VISCOELASTICITY THEORY FOR A POLYMER MICRO-ROD WITH AND WITHOUT ENERGY DISSIPATION

A new study has been developed that considers the size-dependent interaction between viscoelastic deformation and thermal fields, incorporating the fractional heat conduction law with and without energy dissipation. The model is used for a particular one-dimensional problem involving a polymer micro-rod of arbitrary length experiencing three different types of thermal loading without the presence of any heat source. The study uses Laplace transforms and numerical inversion to examine how fractional order, nonlocal elasticity, and nonlocal thermal conduction impact thermal dispersion and thermo-viscoelastic response. Comparative numbers demonstrate the effects of various parameters. Findings demonstrate that nonlocal thermal and viscoelastic characteristics have a significant impact on all recorded field values, offering possible suggestions for the creation and assessment of thermal-mechanical attributes in nanoscale devices.

Performance of photovoltaic panels with different inclinations under uniform thermal loading

Integrating photovoltaic (PV) panels with different tilt angles in building envelopes or roofs is widely employed for environmental sustainability. However, little is known about the influence of different tilt angles on the thermal failure of the photovoltaic façades or roofs in fire conditions. A total of 15 four-edge shielded PV panels (300 × 300 × 4.7 mm3), with five different inclinations of 0°, 15°, 30°, 45° and 60°, were heated to fail using a uniform radiant panel. Measurements were taken to track glass thermal breakage, surface temperatures, incident heat flux and failure characteristics. The glass fracture and pyrolysis of the internal thermoplastic materials were observed under thermal radiation. The average breakage time of glass in PV panels showed an increasing trend with increasing inclination of the PV panels. Moreover, when the PV panels were tilted beyond 30°, the time to failure increased more significantly. The maximum temperature difference and heat flux that the PV panels can withstand were primarily measured within the range of 61–84 °C and 8–15 kW/m2, respectively. Finally, the test results were simulated by a finite element method (FEM) model, calculating the heat transfer and thermal stress of PV panels: the average errors concerning temperature distributions and failure times were smaller than 15 % compared with the experimental results.

Structural characterization of a suspension bridge by mapping the temperature effects on strain response based on neural network models

AbstractMapping the structural responses based on main loads to characterize signature of complex structures with high-dimensional features is a determinant factor for structural health monitoring (SHM). Current technological advances contribute to the optimization of data analysis, aiming to make the process less demanding in terms of time and computational demand. Machine learning (ML) models became popular due to their capacity to estimate structural behaviour based on the measurements gathered by the SHM systems. This work proposes a methodology supported by Neural Networks (NN) for the characterization and prediction of the structural behaviour based on thermal loads and structural responses. By comparing the observed values and predicted outcomes from the NN, it is possible to identify measuring errors, new trends or pattern variations that need further assessment. A sensitivity analysis is also proposed to confirm the model robustness and to characterize the influence of the temperature on the structural responses. The case study is the 25 de Abril’s bridge, located in Lisbon, Portugal.

Study on the effect of variable laser power on residual stress distribution in laser directed energy deposition of Ti6Al4V

In the laser directed energy deposition (LDED) process, cyclic thermal stress loading induces significant temperature variations on the surface and subsurface of the workpiece during repeated heating, leading to the formation of residual tensile stress during cooling. This adversely affects the mechanical properties of the parts, causing deformation and defects. In this study, a heat transfer model and a three-dimensional stress model were established based on finite element analysis. A variable laser power (VLP) deposition strategy was proposed to dynamically simulate the temperature and stress fields of Ti6Al4V titanium alloy under different deposition strategies. The model was validated by collecting substrate temperature variations using thermocouples and measuring residual stress with an X-ray diffractometer (XRD). Experimental results showed that the temperature error between the simulation and the experiment ranged from 6.25 % to 10.12 %, with an average stress simulation error of 6.92 %. Among the four strategies, the samples using the VLP strategy showed a reduction in the average substrate temperature by 12.68 % to 15.08 % compared to the other three strategies. The maximum principal stress in the layer was reduced by 7.8 % to 32.14 %, and the residual stress distribution was more uniform in all directions. The microstructure of the deposition layer further indicated that the VLP strategy improves residual stress distribution and leading to better deposition quality.

AN AERODYNAMIC INVESTIGATION OF A HIGH-PRESSURE TURBINE USING ROTOR CASING STATIC PRESSURE MEASUREMENTS AT ENGINE REPRESENTATIVE CONDITIONS WITH DIFFERENT TIP DESIGNS, TIP GAPS AND INLET TEMPERATURE PROFILES

Abstract A rotating High-Pressure (HP) turbine, in modern aircraft engines, is subjected to high cyclic thermal and mechanical loads. Shroudless turbines experience high heat loads on the rotor tip and casing, which makes them one of the life-limiting components for an engine. If the rotor tip starts to erode, then the tip clearance increases which increases the over-tip leakage flow, resulting in reduced stage efficiency and ultimately, the engine lifetime. The Oxford Turbine Research Facility (OTRF) is a high- speed rotating transient test facility that allows unsteady aerodynamics and heat transfer measurements, at engine representative conditions. This paper presents an experimental investigation, of the HP turbine rotor casing aerodynamics, performed in the OTRF. Steady and unsteady casing static pressure measurements were acquired, using pneumatic lines and high-frequency response (∼ 100 kHz) Kulite pressure transducers respectively. The single-stage HP turbine consisted of cooled vanes (featuring film and trailing edge slot cooling), and uncooled rotor blades. Three different tip designs (two squealers and one flat) were tested, at two tip gaps, and with two inlet temperature profiles that included a spatially uniform total temperature profile and an engine representative HP turbine inlet total temperature profile. In parallel, a numerical investigation of the experimental test cases is presented using unsteady Computational Fluid Dynamics (CFD) predictions. The experimental results from this study provide a unique dataset to validate numerical models.

Multivariate stochastic generation of meteorological data for building simulation through interdependent meteorological processes

In recent years, the uncertainty of weather conditions and the impact of future climate change on building energy assessment has received increasing attention. As an important part of these studies, several types of methods for generating stochastic meteorological data have also been developed. Since solar radiation drops to zero at night, unlike the continuous 24-hour data for elements such as temperature and humidity, this has posed challenges for previous research to fully account for the simultaneity among multiple elements. Therefore, this study proposes a framework for meteorological data generation: First, perform multivariate time series modeling of meteorological data of air temperature, solar radiation and absolute humidity at 12:00 of each day of a typical year based on the S-vine copula method and simulating daily series data at 12:00 for 365 days. Then, based on the probability of change of each element evaluated from the historical meteorological observation data, the daily series data at 12:00 were expanded to 24 h, after which the yearly stochastic weather data were obtained. The analysis of 30 years of stochastic data generated by this method, compared with the original data, reveals that air temperature and solar radiation closely match the original distribution characteristics, except for a minor deviation in the absolute humidity’s kurtosis. Furthermore, the comparison of thermal load distributions for office buildings shows that the original data curve falls within the range of the generated data. This suggests that the generated data includes more information about uncertainty but still keeps the original data’s characteristics.

Simulation-based design: minimizing energy consumption in residential buildings through optimal thermal insulation

Purpose This study aims to optimize the energy consumption of residential buildings in mild and humid climates. It investigates the use of thermal insulation to reduce thermal load through energy simulation analysis. Design/methodology/approach A residential building located in Rasht city, Iran (a mild and humid climate zone), is simulated using DesignBuilder software. Subsequently, the minimum thermal resistance for external walls and roof is analyzed along with its impact on building energy consumption and carbon emissions. Findings The simulation results indicated a 26.5% reduction in heat loss through the walls and a 14.2% reduction through the roof due to optimal thermal insulation. Furthermore, optimal insulation led to a 19.2% reduction in cooling system energy use, a 12% reduction in heating system energy use and a combined 15.3% reduction in total energy consumption for cooling and heating. Originality/value This optimization process leads to several benefits: reduced costs associated with thermal and cooling energy losses in buildings, improved building performance against atmospheric factors and, ultimately, a reduction in energy consumption across the building industry. This research can be valuable to various stakeholders, including the construction industry and building sector, municipalities and engineering systems, building owners and contractors and environmental organizations. By implementing these findings, they can improve the state of modern building insulation and achieve greater energy efficiency.

Short-cycle borehole thermal energy storage: Impact of thermal cycle duration on overall performance

Borehole thermal energy storage arrays are a common form of seasonal underground energy storage which relies on the thermal mass of subsurface rock or sediment to store hot or cold thermal energy. However in practice, typical seasonal operation seldom leads to cyclic energy recovery factors greater than 50%–60% due to significant thermal losses during prolonged periods between consecutive charges. In this paper, the impact of short cycle operation (down to a few days) on energy recovery and overall performance is investigated. Analytical and numerical models are used to estimate energy recovery as a function of cycle length for a typical array and for two distinct charging and discharging scenarios (constant temperature or thermal charge load), which is novel and has not been done before. The results show that shorter cycle duration yields increased recovery factors and storage capacity, which is ascribed to a greater rate of charge to rate of thermal loss ratio. In particular, short-cycle operation at the scale of days unlocks recovery factors in excess of 85 %. The results, supported by a numerical subsurface analysis of the temperature distribution, also show that the recovery efficiency increases with time as losses approach, but never fully reach, a steady-state.

Heating Industrial Buildings with Heat Pump Air Systems: Is It Always the Most Advantageous Option?

According to extant Italian legislation implementing the Renewable Energy Directive, the mandatory renewable quota for a new building is 60% referring to a single service (e.g., heating during winter) or to multiple services (e.g., heating during winter and air conditioning during summer), depending on which services are actually present. The obligation to satisfy this minimum value often leads heating and ventilation plant designers to provide heat pump systems in industrial buildings, typically air/water or direct expansion type coupled with air terminals (air heaters or ventilation units) or radiant floors. The question is: Is this always the most advantageous option for industrial buildings? A typical industrial building was modeled by Trnsys® in two different climates. Based on the calculated thermal heating loads, the condensing radiant tubes and heat pump coupled with the air heaters systems were analyzed through dynamic simulation, evaluating their performance from an energy, environmental impact, and economic point of view. The analysis carried out revealed that a heat pump system is not always the most advantageous solution depending on the climate, the characteristics of the building (less or more thermal insulation, which corresponds to existing buildings rather than new ones), and the size of the photovoltaics system eventually installed on the roof.

A Novel Day-Ahead Optimization-Oriented Low-Carbon Economic Scheduling Scheme for Integrated Energy Systems

As the global energy structure undergoes transformation and the low-carbon development process continues to advance, integrated energy systems have progressively emerged as crucial technical support for achieving sustainable development. In this paper, a joint-day optimal scheduling model is put forward considering the existence of dispatchable resources in community integrated energy systems (CIES). The aim is to cut down the system operation cost and enhance energy utilization efficiency. This model is founded on the concept of energy hubs and combines the shiftable, transferable, and reducible characteristics of demand-side flexible loads. It includes gas turbine power generation systems, energy storage, as well as wind and solar renewable resources. System operation cost and carbon trading cost are comprehensively taken into account, and ultimately, the CIES low-carbon economic dispatch model with the lowest total cost as the optimization objective is established. The Yalmip toolbox and Cplex solver are employed to solve the model. The optimization results of flexible electric and thermal loads participating in dispatching under different scenarios are analyzed through simulation. The economic benefits of electric and thermal independent dispatching are compared and analyzed, and the economic benefits of electric and thermal coupled dispatching are verified. The study reveals that the rational scheduling of user-side flexible loads can notably reduce operating costs, lower the load peak-to-valley difference and carbon emissions, and boost the comprehensive economic and environmental benefits of the system.

Assessment of merits and demerits of perpendicular and slanted photovoltaic/thermal facades

This study compares the thermal and electrical energy production potential and wind load assessment of perpendicular versus slanted photovoltaic (PV) facades. The goal is to identify the optimal facade orientation for societal adoption based on energy efficiency and wind load considerations. Using Hybrid RANS/LES models, the aerodynamic performance and energy yield of both orientations are analyzed under varying angles and environmental conditions. The findings show that while the slanted façade is better designed to capture solar irradiance, it produces 4 to 8 % less energy than the perpendicular façade and yields approximately 2 % less exergy efficiency due to wind regime. However, the slanted design reduces wind load by 9.8 %, enhancing structural stability. The maximum thermal energy output of 217 kW is recorded from the perpendicular façade at a wind speed of 1 m/s, while the slanted façade generates a peak electrical power of 68 kW at 8 m/s wind speed. Overall, the perpendicular façade underscores more efficient in equal weather conditions, making it a sustainable choice for PV installation. These results provide valuable insights for architects, engineers, and policymakers in optimizing PV facade design for urban environments.