Optimal Heat Research Articles

Quick Prediction of Complex Temperature Fields Using Conditional Generative Adversarial Networks

Abstract Qualified thermal management is an important guarantee for the stable work of electronic devices. However, the increasingly complex cooling structure needs several hours or even longer to simulate, which hinders finding the optimal heat dissipation design in the limited space. Herein, an approach based on conditional generative adversarial network (cGAN) is reported to bridge complex geometry and physical field. The established end-to-end model not only predicted the maximum temperature with high precision but also captured real field details in the generated image. The impact of amount of training data on model prediction performance was discussed, and the performance of the models fine-tuned and trained from scratch was also compared in the case of less training data or using in new electronic devices. Furthermore, the high expansibility of geometrically encoded labels makes this method possible to be used in the heat dissipation analysis of more electronic devices. More importantly, this approach, compared to the grid-based simulation, accelerates the process by several orders of magnitude and saves a large amount of energy, which can vastly improve the efficiency of the thermal management design of electronic devices.

A Rome district transition towards optimal and sustainable heat and power generation

In this work, a specific district of Rome energy metabolism has been studied to reduce the carbon footprint of electric and thermal energy generation. Two scenarios were investigated, one “ex-ante” with the district as it was, fully dependent on the national grid for electricity and methane-fuelled boilers for heating. And an “ex-post” scenario with the buildings retrofitted with more efficient thermal insulation, LED lights, photovoltaic panels and trigeneration systems. The energy metabolism of the district was modelled in TRNSYS in both cases. For the ex-post scenario, the digital twin implemented a control logic for energy flows with several functionalities including prioritizing the power flow, setting rules and boundaries on the operation of the co-generators, preventing batteries from overcharging/discharging. The sizing of PV panels, batteries, and cogeneration units in the ex-post scenario was optimized in terms of both energy and economic performance using a Python library with the Non-dominated Sorting Genetic algorithm (NSGA-II). In the ex-post scenario, the optimal energy system delivers significant reductions in energy costs and CO2 emissions. The energy transition results in a decrease in purchased electricity of 68.2%, CO2 emissions by 56% and generation costs by 48.9%. The Levelized Cost Of Energy (LCOE) of the district is estimated to be 196 €/MWh.

Thermal performance analysis of oriented MHD convective flow and entropy production of hybrid nanofluids in a cavity induced by semicircles at different radii ratios

AbstractThe current study numerically treats the magnetic field impacts on the natural convection flow and entropy generation in a square cavity filled with hybrid nanofluid and induced by two isothermally heated semicircles at the bottom and left walls of the cavity. The cavity is filled by hybrid nanofluid (titanium oxide/silver‐water) and oriented under different inclination angles with the applied magnetic field. The simulations in this study were executed via a home‐made code written in the FORTRAN programing language. The numerical methodology considered to solve the coupled equations of continuity, momentum, energy, and entropy generation equations with the associated boundary conditions is the finite volume method and the full multigrid acceleration. Various wake parameters are considered in this research study, namely, the inclination angle of the cavity (α), the magnetic field inclination (γ), the Hartmann number (Ha), the Rayleigh number (Ra), the volume fraction of the hybrid nanofluid (ϕ) and the internal semicircles radii ratio (β). The major findings issued from the impact of these parameters on the fluid flow and heat transfer characteristics reveal that heat transfer and entropy generation are a decreasing function of the Hartmann parameter. Moreover, the total entropy generation is intensified by 85.23% from Ra = 103 to Ra = 106 for Ha = 10, by 85.818% for Ha = 50 and 83.813% for Ha = 100. Besides, the flow magnitude is found decreasing with increasing the radii ratio β of the semicircles. It is also found that optimal heat transfer rates deducted from the variation of average Nusselt number versus Ra for different volume fractions of the hybrid nanoparticles are obtained for the extreme values of the pertinent parameters (β = 1, ϕ = 8%, Ra = 106). Hence, the present work offers a useful tool and a parametric study for the research community and engineers on the design and optimization of thermal management systems used in a variety of industrial applications, such as heat exchangers, nuclear reactors, and energy systems.

Enhanced heat transfer rate on the flow of hybrid nanofluid through a rotating vertical cone: a statistical analysis

The recent study needs the optimal conditions for maximizing heat transfer rate with minimizing energy consumption. This is a basic objective of several industries in their production processes along with in improving the efficiency in electronic gadgets. Therefore, hybrid nanofluid plays an important role in enhancing heat transport phenomena. The current study investigates the improved heat transfer properties of a water-based hybrid nanofluid containing Al2O3 and Cu nanoparticles flowing through a rotating vertical cone embedded in a porous medium. The convective flow is enhanced by a magnetic field and thermal radiation, contributing to the complexity of the flow dynamics. However, the dimensional physical quantities are transformed to non-dimensional parameters by the implementation of suitable similarity rules. Furthermore, the transformed equations are numerically solved using a fourth-order Runge-Kutta shooting method. Henceforth, to get the optimal heat transfer rate, a robust statistical technique called response surface methodology (RSM) and for the validation a hypothetical test is organized by using analysis of variance. The parametric behavior is conducted via graphs and the physical description is presented briefly. Further, the major outcomes of the study are: both the particle concentrations attenuate the axial velocity whereas the fluid temperature enhances significantly. Increasing radiative heat augments the heat transport phenomena and the observation reveals that the case of hybrid nanofluids overrides the case of nanofluids.

Effect of forming parameters on the corrosion performance of retrogression- and warm-formed AA7075 alloy sheets

ABSTRACT Retrogression forming (RF) and warm forming (WF) are used to remedy formability limitations of high-strength precipitation-hardened AA7075 alloy sheets. RF is a thermomechanical treatment combining retrogression heat treatment and the forming of initially peak-aged T6 temper. WF is a thermomechanical treatment of initially pre-aged temper. The present work examines the corrosion performance of retrogression- and warm-formed AA7075 alloy sheets by determining the optimal pre-aging temperature (80°C or 100°C), forming temperature (room temperature, 150–200°C), strain rate (1, 0.1, or 0.01 s−1), and heating rate (1.1 or 20°C·s−1) for conventional slow and novel fast-forming technologies. Several alternating- and direct-current electrochemical tests were administered, including electrochemical impedance spectroscopy, potentiodynamic polarization, and linear polarization resistance. Results showed that the corrosion performance (i.e., passive film and corrosion-resistant properties) of formed AA7075 sheets was directly proportional to pre-aging and WF temperatures, inversely proportional to the RF temperature, and mildly affected by strain/forming rate and heating rate during forming.

Impact of Heat Treatment on the Mechanical Properties and Fracture Morphology of Ti555211 Alloy.

Heat treatment is important for optimizing the strength performance and improving the toughness of titanium alloys. In this study, we investigated the impact of three heat treatment methods (β-annealing, double annealing, and solid-solution and aging treatment) on the mechanical properties and fracture morphology of Ti555211 titanium alloy. The results show that after β-annealing treatment, the alloy retains a high strength, while showing almost no ductility, and no yield strength. The alloy after double annealing has a high elongation rate (~54%) and lower strength. After solid-solution and aging heat treatment, the alloy was able to retain both high strength and a certain degree of ductility. The optimal heat-treatment process is solid-solution treatment at 820 °C/2 h and aging at 560 °C/12 h, which results in a maximum tensile strength of 1404 MPa and an elongation rate of 11%.

Optimum heating time for warm forming of AA7075 aluminum alloy in T6 condition

Optimum heating time for warm forming of AA7075 aluminum alloy in T6 condition

Booster heat pump with drop-in zeotropic mixtures applied in ultra-low temperature district heating system

The pursuit of sustainable district heating solutions has driven a growing interest in ultra-low temperature district heating (ULTDH) systems, where booster heat pumps (BHPs) play a pivotal role despite challenges posed by their efficiency limitations under large temperature glide conditions. This paper investigates the potential of drop-in R-1234yf/R-32 zeotropic mixtures in BHPs compared to a baseline R-134a system, within the context of a ULTDH framework. This study focused on the viability of the mixtures of R-1234yf/R-32 with the composition ratio of 80 %/20 % and 90 %/10 %. The investigation reveals disparities in compressor efficiency and heat exchanger pressure drop at the component level. Device-level analysis unveils increased COP for R-1234yf/R-32 mixtures, alongside with maximum second-law efficiencies reaching 0.32. A remarkable enhancement in heating capacity up to 58 % was found. System-level analysis demonstrated exergetic efficiencies and identified preferable district heating temperatures. Exergetic efficiencies of 0.47, 0.55, and 0.59 were achieved for domestic hot water preparation at district heating supply temperatures of 30 °C, 35 °C, and 40 °C, with a subsequent shift in optimal district heating temperatures as central heating station efficiency decreased. Temperature profile analysis underscored challenges stemming from excessive subcooling, highlighting the need for configuration refinements.

Study of the Effects on the Strengthening Mechanism and Wear Behavior of Wear-Resistant Steel of Temperature Controlling in Heat Treatment.

To improve the wear resistance of the materials used for blades in engineering machinery, this study focused on the microstructural characteristics, mechanical properties, and wear behavior of HB500 grade wear-resistant steel developed using an optimized heat treatment system. To improve the temperature uniformity of the heat treatment furnace, the method of cyclic heating was used to heat the components. Carefully designing the quenching equipment, such as using a cross-shaped press, was employed to enhance the quenching effect and reduce the deformation of the steel plates. The crystal orientation analysis revealed a uniform and fine-grained microstructure, primarily characterized by plate-type tempered martensite, which indicated a good hardenability. The microstructure observations showed that the width of martensite is approximately 200 nm, with a significant presence of dislocations and carbides. Tensile tests and multi-temperature gradient impact tests indicated superior mechanical properties compared to similar grade wear-resistant steels, including a Rockwell hardness of 53, tensile strength of 1610 MPa, yield strength of 1404 MPa, and total elongation around 12.7%. The results of friction and wear experiments indicate that the wear rate decreases as the load increases from 100 N to 300 N, demonstrating an excellent wear resistance under a large load. Observations of the worn surfaces indicated that the wear mainly involved adhesive wear, fatigue wear, and oxidative wear. The properties' improvements were attributed to microstructure refinement and precipitation strengthening. This study indicates that designing a heat treatment system to control temperature uniformity and stability is feasible.

Numerical study of anisotropic scattering and solar radiation impact on liquid droplet radiator performance

The Liquid Droplet Radiator (LDR), a lightweight frameless radiant heat rejection system, is widely regarded as the optimal heat rejection solution for megawatt-scale space nuclear power systems. The LDR dissipates heat to space through its droplet layer, which plays a crucial role in determining its radiative rejection capacity. Radiation beams undergo a series of emission, scattering, and absorption processes within the layer before being emitted into space. Prior studies typically assume isotropic scattering in this process. However, this study develops a three-dimensional model for the LDR’s droplet layer based on Mie theory and Monte-Carlo methods to investigate the impact of anisotropic scattering and solar radiation. Our calculations reveal that the working fluid exhibits strong forward anisotropic scattering characteristics. Under the anisotropic assumption, the heat rejection capability of the LDR is 27–33 % higher compared to the isotropic assumption. Regarding the temperature distribution within the LDR, under the anisotropic assumption, the layer’s temperature is 6 K lower at the XY boundary surface and 3 K higher at the layer median, as opposed to the isotropic assumption. We introduce the concept of the probability of a light beam escape to elucidate the distinct beam transmission mechanisms and temperature distribution. When the distance between the LDR and the sun is in the vicinity of 1 AU, the impact of solar radiation on the LDR’s ability to operate is on the scale of 1E-5, which is almost negligible. This study lays down a theoretical groundwork for calculating the heat rejection capacity during the LDR design phase.

Effect of heat treatment on microstructure and mechanical properties of 18Ni-350 maraging steel fabricated by Wire and Arc Additive Manufacturing

An 18Ni-350 maraging steel single wall structure was fabricated using Wire Arc Additive Manufacturing (WAAM). Due to the rapid cooling and cyclic heating, elements such as Ni, Ti, and Mo were segregated within the single wall, resulting in a microstructure characterized by coarse primary dendrites and secondary dendrites. Various heat treatment were devised for the samples, encompassing Solution Treatment (ST), Solution + Aging Treatment (SAT), and Direct Aging Treatment (DAT). The findings revealed that elemental segregation persisted when the ST temperature was below 1050 °C, but disappeared when it exceeded 1150 °C, withthe microstructure transitioning from dendritic to equiaxed grains. ST resulted in the decrease of microhardness and tensile strength, but an enhancement in elongation. The effect of DAT was unsatisfactory for the improvement of mechanical properties while SAT could significantly improve them. Transmission Electron Microscope (TEM) analysis showed that a uniform distribution of Ni3Ti and Ni3Mo strengthening phases was formed in the martensitic matrix after SAT. The ultimate tensile strength of the sample reached 2163 ± 42 MPa under the optimal heat treatment condition (SAT 1150 °C-1 h + 480 °C-6 h).

Numerical and experimental study of thermography parameters for inspection of composites repaired by CFRP patches

ABSTRACT Considering the ever-increasing importance of composite patches applied to repair or reinforce composite structures, radical health monitoring of these patches seems inescapable. Thermography method is one of the most influential non-destructive methods applied to inspect the repaired structures. Since there are many parameters influencing defects detection in repaired composite structures, extracting the most influential method to determine these parameters is significantly important. In the present study, a repaired carbon fiber reinforced plastic (CFRP) composite structure having defects of different dimensions, types and features located in different depths, is investigated by experiment and finite element simulations to assess the influence of the experimental parameters, like the thermal excitation pulse duration and the best image frame. In thermal simulation, two criteria, maximum thermal variations versus time and path length, are developed to derive the most optimum heating duration and the best thermal frames. The obtained results are validated through defining direct and diagonal paths passing through defects demonstrated on thermography images and thermal map images. The average error of thermal variations on different paths displayed on thermography and simulation images is less than 4.5 percent which confirms the correspondence of obtained results of both mentioned methods.

A computational search for the optimal microelectronic heat sink using ANSYS Icepak

The efficient thermal management of microelectronic devices is crucial for their reliability and performance. Heat sinks, particularly those with inline and staggered fin arrangements, are vital in achieving this goal. This study leverages the advancements in computational fluid dynamics (CFD) software to explore the optimal heat sink design for microelectronic devices. While prior research has extensively investigated heat sink design, this work offers novelty by employing ANSYS Icepak software for simulations. This approach enables a comprehensive thermal performance and pressure drop analysis for two distinct fin cross-sections. The study investigates heat sink assemblies housed within a confined space, simulating a realistic operating environment for microelectronic devices. The heat sink is designed to cool a single heat source (chip) mounted on a substrate board. In this paper, two types of fin sections, circular and conical, are studied for two types of fin configurations, inline (IA) and staggered (SA), which are analysed with 36 fins in each case. Each fin is constructed from aluminium and has specified dimensions. Air serves as the cooling fluid within the cabinet, dissipating heat generated by the chip. When comparing the performance of circular pin and cone fins at the same power and mass flow rate, the results indicated that the maximum temperature for circular pin fins is 0.46% of the maximum temperature for cone fins, and they have a higher pressure drop, especially for staggered arrangements. Moreover, the maximum temperature for staggered arrangements is lower than that for inline configurations by a factor of up to 1.17% and 2.035% for circular fins and cone pin fins, respectively. This article focuses on a deep understanding of the design of microelectronic cooling systems. It aims to continuously improve pressure and thermal efficiency by maintaining the minimum limits of pressure drop within the confined space and obtaining the optimal configuration for efficient heat dissipation.

Modeling and research on high-frequency AC heating system for lithium-ion battery based on bidirectional buck-boost topology

Lithium-ion battery (LIB) performance decreases in cold climates, preheating is necessary to improve the output power and life decay of low-temperature LIB. At present, a variety of internal alternative current (AC) heating methods are used to achieve fast and temperature-consistent heating. However, existing AC heating devices are constrained by the problems of changing the battery structure, and also need for an additional power supply to power the battery, which have effect on the battery life. Meanwhile, the conventional model is not suitable for AC preheating simulation, especially at high frequencies. Under above scenarios, a high-frequency AC heating method using a bidirectional boost converter is designed and a high-frequency thermoelectric model based on lithium-ion transmission is developed. In the paper, the proposed high-frequency AC heating structure and thermal-electrical coupling model are verified by experimental results to test the validity of different AC heating frequencies, which solves the lack of comprehensive theoretical and experimental verification in the field of high-frequency AC heating. The experimental results show that increasing the AC heating frequency at the same current multiplicity can significantly increase the heating rate. An optimal frequency is acquired, the optimal heating rate can reach 4.65 K/min at 800 Hz without affecting the service life of the battery. The high-frequency AC heating method provides a new solution framework for the LIB performance enhancement in cold climates.

Investigation of heat transfer performance and enhancement mechanisms of supercritical carbon dioxide in PCHE with fractal airfoil fins

A fractal structure featuring symmetric/asymmetric airfoil fins is embedded within the smooth channels of the printed circuit heat exchanger (PCHE), significantly enhancing its heat transfer performance. In this study, a horizontally installed two-layer channel configuration is examined, with hot CO2 flowing through the upper channel and cold CO2 through the lower channel. Two distinct airfoil fin designs, namely NACA 0021 symmetric and NACA 4822 asymmetric, are tested for their channel reinforcement effect. The numerical analysis reveals that channels equipped with these fins exhibit substantially improved heat transfer compared to smooth channels. Notably, the comprehensive evaluation index for the asymmetric airfoil fin channel is enhanced by a factor ranging from 1.05 to 3.76. Moreover, despite a modest increase in pressure drop, indicated by a dimensionless friction factor of 0.67–1.31, the heat transfer performance remains superior. Crucially, optimal heat transfer does not rely solely on high fluid flow rates but instead demands an apt flow matching between the hot and cold fluid channels.

The Effect of Basic Building Materials and Their Paving Shapes on the Thermal Performance of Walls in Iraqi Residential Buildings

ABSTRACT Iraq's high climatic temperature affects buildings' thermal performance, leading to increased electrical energy consumption due to population growth. Researchers are exploring methods to reduce this consumption, such as heat gain reduction, heat transfer prevention, thermal insulators, high-thermal resistance materials, positive building design, useful orientation, and clean energies. The study investigates solar heat transfer in Iraqi air-conditioned spaces using nine models to analyze the impact of building elements on residential walls and their cross-section shape. The aim is to determine the best model for the Iraqi climate and the optimal approach for achieving optimal solar heat transfer. The study reveals that Model A has negative thermal performance, while Model C and I offer superior thermal performance. Model C offers 47.34% energy savings and Model I 43.99%, aligning with the global trend for green buildings and low energy expenditure in Iraqi residential units.

Crystallographic study on microstructure evolution and mechanical properties of coarse grained heat affected zone of a 500 MPa grade wind power steel

The effect of different welding heat inputs on the microstructure and mechanical properties of the simulated coarse grained heat affected zone (CGHAZ) of high-strength wind power steel with yield strength of 500 MPa has been investigated using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Charpy impact tests have demonstrated that there exists an optimum heat input of ∼20 kJ/cm that allows optimum impact toughness to be obtained for the CGHAZ. It was shown that this is related to the refined bainitic structure and the highest density of high-angle grain boundaries (HAGBs) with misorientation angle of more than 45°. In crystallographic visualization studies, it was shown that the weakest variant selection occurs for the bainite transformation in the optimal heat input, leading to the highest density of HAGBs with each Closed-packet group containing two or three Bain groups and showing a staggered arrangement structure. The contribution that can effectively deflect and prevent crack propagation during impact experiments has to come from the block boundary. However, it was also found that the center segregation induced by C and Mn reduces the low-temperature impact toughness of the core sample before and after simulated welding, and affects the fluctuations of impact toughness and fatigue performance of simulated CGHAZ. Mn segregation can have a genetic effect on the welding heat affected zone, inducing a lower temperature martensitic transformation, which in turn leads to a decrease in low-temperature toughness and fatigue crack arrest performance.

Double diffusive thermogravitational convection in a convex U-shaped porous chamber filled with radiative ternary hybrid nanoliquid

This research deals with the intricate dynamics of double diffusive thermogravitational convection within a convex U-shaped porous chamber and sheds light on the use of a radiative ternary hybrid nanoliquid. In this configuration, the lower flat boundary is assumed to be thermally hot and densely concentrated while the curved lateral boundaries remain cold and dilute. The other boundaries of the enclosure are kept under adiabatic conditions. The governing Navier–Stokes equations along with thermal and species equations are effectively solved by employing a higher order compact technique. The developed in-house program has been rigorously verified against experimental and computational benchmark results. The research meticulously examines the impact of several pivotal parameters, including the Lewis number (1≤Le≤20), buoyancy ratio (0≤N≤10), Darcy number (10−4≤Da≤10−2), Rayleigh number (104≤Ra≤106), volumetric heat source/sink coefficient (−10≤q≤10), radiation parameter (1≤Rd≤5), aspect parameter of the U-shaped chamber (0.2≤AR≤0.6), and solid particles concentration (0.0≤ϕthnp≤0.04) of the ternary hybrid nanofluid. The findings are eloquently portrayed through graphical representations by showcasing streamlines, iso-solutals, isotherms, and the dimensionless Nusselt (Nuavg) and Sherwood (Shavg) parameters. Our investigation demonstrates that the ternary hybrid nanofluid outperforms both hybrid and mono nanofluids in facilitating double diffusion processes. Moreover, optimal heat transfer efficiency is achieved under conditions characterized by an aspect ratio of AR = 0.2, Rayleigh number Ra=106, Darcy number Da=10−2, buoyancy ratio N = 10, Lewis number Le = 1, and solid volume fraction ϕthnp=0.04.

Multi-factor coupling optimization of heat recovery effectiveness in a transcritical CO2 heat pump

In the background of energy shortage and climate change, transcritical CO2 heat pump(HTP) technology has attracted lots of attention because of its energy-saving and environmentally friendly advantages. In this research, an experimentally verified simulation model of transcritical CO2 HTP is established to investigate multi-factor coupling optimization of heat recovery effectiveness(ηIHX). First, the coupling optimization mechanism of ηIHX and discharge pressure(pdis) is analyzed. Moreover, this research explores the influence of ηIHX on heating capacity, power consumption, discharge temperature(tdis), and internal heat exchanger(IHX) cost, and further proposes a comprehensive heat recovery index to optimize the above factors. Based on this index the optimal heat recovery effectiveness(ηIHX,opt) for each operating condition is obtained. Also, a failure boundary for the coupling optimization of the ηIHX is also indicated. In addition, the optimal discharge pressure(pdis,opt) prediction correlation for different ηIHXs is proposed, which can be used for heat recovery effectiveness collaborative optimization control. Finally, a general method for evaluating IHX is provided. Taking Xi'an as an example, the optimal heat recovery area(AIHX,opt) of this HTP system is 0.42m2, with which the optimized HTP system operates safely at extreme operating conditions, resulting in an annual lucre of 1,211 CNY.

Exploring Urban Sustainability: The Role of Geology and Hydrogeology in Numerical Aquifer Modelling for Open-Loop Geothermal Energy Development, the Case of Torino (Italy)

This research examines the integration of geological and hydrogeological data in numerical aquifer model simulations, with a particular focus on the urban area of Torino, Italy. The role of groundwater resources in urban sustainability is analysed. The objective is to integrate open-loop geothermal plants into the district heating network of IREN S.p.A. Two case studies are examined: the Torino Nord area and the Moncalieri area, both of which host district heating plants. The work entails the collection and analysis of data from a variety of sources, including geognostic surveys and permeability tests, in order to construct a three-dimensional numerical model of the surface aquifer. Models were built using the public MODFLOW 6 (model of groundwater flow) code and calibrated using PESTHP (High Performance of Model Independent Parameter Estimation and Uncertainty Analysis). Results indicate the potential of urban aquifers as renewable energy sources and the necessity of comprehensive geological and hydrogeological assessments for optimal ground water heat pump (GWHP) system installation. This paper emphasises the significance of sustainable water management in the context of climate change and urbanisation challenges.