Heat Problem Research Articles

Improved long pulse excitation infrared nondestructive testing evaluation.

In this paper, an improved long-pulse excitation infrared nondestructive testing method is proposed, and a homogeneous pulse thermography (HPT) system is built. Based on the proposed new pulse excitation system, the problem of uneven heating in pulsed infrared non-destructive testing (NDT) has been effectively improved, and the signal-to-noise ratio of thermal images has been improved. Finally, the results of the experimental analysis and discussion show that the improved pulsed infrared NDT system greatly improves the defect detection rate and the reliability of the quantitative analysis of defect depth compared with the traditional pulsed detection system.

Analysis of Heuristic Optimization Technique Solutions for Combined Heat-Power Economic Load Dispatch

Thermal power plants use coal as a fuel to create electricity while wasting a significant amount of energy as heat. If the heat and power plants are combined and used in cogeneration systems, it is possible to reuse the waste heat and hence enhance the overall efficiency of the power plant. In order to minimize production costs while taking system constraints into account, it is important to find out the optimal operating point of power and heat for each unit. Combined heat and power production is now widely used to improve thermal efficiency, lower environmental emissions, and reduce power generation costs. In order to determine the best solutions to the combined heat and power economic dispatch problem, several traditional as well as innovative heuristic optimization approaches were employed. This study offers a thorough analysis of the use of heuristic optimization techniques for the solution of the combined heat and power economic dispatch problem. In this proposed work, the most well-known heuristic optimization methods are examined and used for the solution of various generating unit systems, such as 4, 7, 11, 24, 48, 84, and 96, taking into account various constraints. This study analyzes how various evolutionary approaches are performed for various test systems. The heuristic methodologies’ best outcomes for various case studies with restrictions are contrasted.

Cooling as social practice: Heat mitigation and the making of communal space in Jakarta's informal settlements

The rise of Urban Heat Island (UHI) is harming people across megacities in the world. In Jakarta, the informal settlements are most affected due to the lack of adequate infrastructure to deal with the heat. The heat problem in the informal settlements was primarily exacerbated by overcrowding and a lack of access to cooling infrastructures. In this paper, we observe how residents of the informal settlements take on a cooling practice collectively. Our study is situated in five urban kampongs located in the most populated sub-districts (kelurahan) in Jakarta. Nine months of ethnographic fieldwork were conducted to unpack the residents' endeavor to mitigate the heat problem. To explicate the process and the role of these cooling facilities, we use the notion of social practice comprising three fundamental elements: competence, material, and meaning. “Social practice” aptly characterizes how the residents in each kampong worked together to build cooling places that also function as communal spaces. Our research discovered that despite limited resources and technical competence, each kampong recognized the necessity of communal spaces to maintain their cooling practices. These measures enabled them to engage in cooling practices while building social relationships through chilling outdoors. By demonstrating the capacity of residents in the informal settlements for constructing vernacular forms of cooling infrastructure, this paper offers a pluralistic view of heat mitigation in megacities of the Global South.

Polarisation of decayless kink oscillations of solar coronal loops

Decayless kink oscillations of plasma loops in the solar corona may contain an answer to the enigmatic problem of solar and stellar coronal heating. The polarisation of the oscillations gives us a unique information about their excitation mechanisms and energy supply. However, unambiguous determination of the polarisation has remained elusive. Here, we show simultaneous detection of a 4-min decayless kink oscillation from two non-parallel lines-of-sights, separated by about 104∘, provided by unique combination of the High Resolution Imager on Solar Orbiter and the Atmospheric Imaging Assembly on Solar Dynamics Observatory. The observations reveal a horizontal or weakly oblique linear polarisation of the oscillation. This conclusion is based on the comparison of observational results with forward modelling of the observational manifestation of various kinds of polarisation of kink oscillations. The revealed polarisation favours the sustainability of these oscillations by quasi-steady flows which may hence supply the energy for coronal heating.

Cooling Energy Benefits of Increased Green Infrastructure in Subtropical Urban Building Environments

Due to urban warming, the energy demand for cooling buildings is rising. The current study used CitySim (building energy model) to estimate the cooling energy requirements for 40 buildings in downtown Dubai using high-resolution climate data from weather research and forecasting (WRF) coupled with the single layer urban canopy model (SLUCM). Simulating the four mitigation scenarios allowed for the examination of the reduction in cooling load caused by the addition of greenery at a rate ranging from 25% to 100%. The insulated building’s cooling demand reduced by a maximum of 13.89% under 100% GI (M4). Scenario M4 resulted in a reduction of 4.6 kWh/m2 and 3.1 kWh/m2 for the non-insulated and insulated low-rise residential buildings, respectively, while the high-rise buildings saw a reduction of 3.09–4.91 kWh/m2 for the non-insulated and 2.07–3.09 kWh/m2 for the insulated buildings. This study offers a potential remedy to deal with the problem of urban heating in subtropical environments.

Numerical Solution of the Inverse Problem of Heating of a Solid Body by Laser Radiation

Numerical Solution of the Inverse Problem of Heating of a Solid Body by Laser Radiation

On the Error in Determining the Protective Layer Boundary in the Inverse Heat Problem

On the Error in Determining the Protective Layer Boundary in the Inverse Heat Problem

Numerical investigations of new low‐order explicit last stage diagonal implicit Runge–Kutta schemes with the finite‐element method

AbstractInitial value problems can be solved efficiently by means of Runge–Kutta algorithms with adaptive step size control. Diagonally implicit Runge–Kutta (DIRK) methods are the most popular class among the diverse family of Runge–Kutta algorithms. In this paper, the novel class of low‐order explicit last‐stage diagonally implicit Runge–Kutta (ELDIRK) methods are explored, which combine implicit schemes with an additional explicit evaluation as an explicit last stage. ELDIRK Butcher tableaus are used to control embedded RK methods to obtain solutions of different orders. The lower‐order solution is obtained by classical implicit RK stages and the higher‐order solution is obtained by additional explicit evaluation. As a result, a significant reduction in computational cost is achieved by skipping the iterative solution of nonlinear systems for the additional step. The examination of the heat problem and the use of the innovative Butcher tableau in the finite‐element method are the main contributions of this work. Thus, it is possible to establish adaptive step size control for the new low‐order embedded methods based on an empirical method for error estimation. Two‐dimensional simulations are used to show an appropriate algorithm for the ELDIRK schemes. The new Runge–Kutta schemes' predictions of higher‐order convergence are confirmed, and their successful outcomes are illustrated.

Plasma Ion Bombardment Induced Heat Flux on the Wafer Surface in Inductively Coupled Plasma Reactive Ion Etch

Plasma plays an important role in semiconductor processes. With the recent miniaturization and integration, the control of plasma became essential for success in the critical dimension of a few nanometers and etch narrow and deep holes with their high aspect ratios. Recently, the etching process has reached physical limitations due to a significant increase in wafer surface temperature under the elevated amount of RF power, affecting not only the warpage phenomenon, but also etching uniformity and etching profiles. Therefore, the plasma characteristics are identified using an invasive single Langmuir probe (SLP) for wafer temperature diagnosis. Optical data is obtained through a non-invasive optical emission spectroscopy (OES) and the plasma parameters are derived to compare and verify with the SLP. Two variables, electron temperature and electron density, are substituted for the heat flux formula to derive the heat flux according to the location. Using a wafer-type temperature sensor, the trends of the derived heat flux values towards wafer chuck were investigated. This study presents a method to calculate heat flux values in real time, anticipate wafer temperatures, and potentially illuminate existing ion heating problems.

An Unsupervised Machine Learning-based Algorithm for Detecting Weak Impulsive Narrowband Quiet Sun Emissions and Characterizing Their Morphology

The solar corona is extremely dynamic. Every leap in observational capabilities has been accompanied by unexpected revelations of complex dynamic processes. The ever more sensitive instruments now allow us to probe events with increasingly weaker energetics. A recent leap in the low-frequency radio solar imaging ability has led to the discovery of a new class of emissions, namely weak impulsive narrowband quiet Sun emissions (WINQSEs). They are hypothesized to be the radio signatures of coronal nanoflares and could potentially have a bearing on the long standing coronal heating problem. In view of the significance of this discovery, this work has been followed up by multiple independent studies. These include detecting WINQSEs in multiple data sets, using independent detection techniques and software pipelines, and looking for their counterparts at other wavelengths. This work focuses on investigating morphological properties of WINQSEs and also improves upon the methodology used for detecting WINQSEs in earlier works. We present a machine learning-based algorithm to detect WINQSEs, classify them based on their morphology, and model the isolated ones using 2D Gaussians. We subject multiple data sets to this algorithm to test its veracity. Interestingly, despite the expectations of their arising from intrinsically compact sources, WINQSEs tend to be resolved in our observations. We propose that this angular broadening arises due to coronal scattering. Hence, WINQSEs can provide ubiquitous and ever-present diagnostic of coronal scattering (and, in turn, coronal turbulence) in the quiet Sun regions, which has not been possible until date.

Application of an Improved Ridgelet Process Neural Network for Predicting the Temperature Rise of Rotor Structure Optimization

To solve the negative-sequence temperature-rise problem of large equipment under asymmetric operating conditions, this paper optimizes the structure of the main components and adopts an improved process neural network to conduct online analysis and calculate the operating data, achieving the accurate prediction of the equipment heating status. Firstly, taking a 300 MW generator that urgently needs equipment improvement as the research object, the typical asymmetric accident characteristics that have occurred in recent years and the main influencing factors of negative-sequence heating of the rotor are analyzed. The influence of the rotor damping structure and shaft length on the temperature-rise change is explored. Secondly, a tent map is introduced to enhance the distribution uniformity of the population in the search space to enhance the global convergence of niche genetic algorithms. Numerical experiments and field experiments show that the improved algorithm, which is applied to optimize the parameters of the ridgelet process neural network, has good temperature-rise prediction performance. Finally, the influence of the rotor length and number of pole damping bars on the negative-sequence heating problem under different negative-sequence component ratios is examined, which provides useful references for the structural optimization and asymmetric operation state prediction of large equipment.

Performance of discretely mounted metal foam heat sinks in a channel with nanofluid

Solving the heating problem of electronic systems, whose performance and power consumption increase with the developing technology, has been the common research topic of many researchers today. In this context, conventional cooling methods should be improved by using innovative materials to achieve more effective cooling performance. In this study, metal foam heat sinks (Al-6101) with pore densities of 10 and 40 pore per inch were utilized instead of commercially finned surfaces used in electronic cooling applications, and their effects on thermal and pressure performance were investigated. The experiments were carried out under steady state conditions. As the coolants, the deionized water (base fluid) and CuO-H2O nanofluids which was prepared with different concentrations and surfactant additive, were used. The volumetric flow rates of the fluids were chosen in range of 17.6 L/h − 76.5 L/h and the heat fluxes were selected in range of 3267 W/m2 − 5400 W/m2. The effect of each parameter on heat transfer was investigated with 5 different prepared nanofluids. The following experiments were carried out by using metal foam heat sinks and the nanofluid (w/w, 0.1% CuO/2% PEI-H2O) where the best results were obtained. The obtained results were compared with the base fluid. With the use of 10 and 40 pore per inch metal foam heat sinks together with the base fluid, an improvement in the mean convection heat transfer coefficient between 11.1% and 22.2% was achieved at all heat fluxes and volumetric flow rates compared to the empty surface (surface without metal foams). When nanofluid (w/w, 0.1% CuO/2% PEI-H2O) was used together with metal foam heat sinks, an improvement changing between 26.3% and 42.5% was recorded. When the effect of all parameters used in the experiment were examined, the best results in terms of thermal performance were obtained when nanofluid with w/w, 0.1% CuO/2% PEI-H2O content and 10 pore per inch metal foam heat sinks were used together. Results suggest that the use of nanofluid together with metal foam will satisfy the economy and power consumption requirements of cooling electronic systems.

An inverse problem for semilinear equations involving the fractional Laplacian

Our work concerns the study of inverse problems of heat and wave equations involving the fractional Laplacian operator with zeroth order nonlinear perturbations. We recover nonlinear terms in the semilinear equations from the knowledge of the fractional Dirichlet-to-Neumann type map combined with the Runge approximation and the unique continuation property of the fractional Laplacian.

Performance analysis of heat and mass transfer, thermodynamic and economic of high gravity direct contact evaporation system

Based on the problem of low heat and mass transfer efficiency and low heat utilization rate in the process of efficient utilization and treatment of low-grade waste heat, the high gravity direct contact evaporation (HG-DCE) system driven by industrial waste heat is proposed. The heat and mass transfer properties in HG-DCE process were studied by simulated with hot water and air at room temperature, and the thermodynamic and economic properties were further analyzed in detail. Results showed that the evaporation intensity of the HG-DCE system could reach 1523 kg/(m3·h), and the volume heat and mass transfer coefficients could reach 270.77 kW/(m3·°C) and 12.23 kg/(m3·s), respectively. According to the established analysis models of entropy generation and exergy loss, the rule of irreversibility of system was obtained, and the highest exergy efficiency was higher than 90.0 % at the gas-liquid mass ratio of 1:1. Simultaneously, the evaporation heat of system accounted for 40.0 % of the supplied heating enthalpy, and the evaporation cost about 0.094 $/kg could be easily achieved. The perfect performance and advantages of HG-DCE system were further confirmed, which provided a new method for using low grade heat for seawater desalination and wastewater treatment.

Some problems of heat and mass transfer during the operation of engineering systems in multiphase environments

Three types of problems related to problems of heat and mass transfer in the soil are considered. The first class of problems deals with the diagnostics of damage of underground pipelines by thermal fields on the soil surface. The second type studies the dynamics of changes in the temperature of a geothermal reservoir depending on the temperature of the water entering this reservoir and the pressure gap between injection and production wells. The third-type problems consider the propagation of non-stationary thermal fields in the soil from operated engineering systems in the permafrost. The main attention is paid to long-term forecasting of the propagation of non-stationary thermal fields in the frozen soil between operating production wells of northern oil and gas fields. In problems of the first two classes, which served as a basis for the development of problems of the third type, water filtration in the soil is considered, and thermal fields propagate in single-phase media. The third-class problems take into account possible phase transitions in the soil when describing non-stationary thermal fields in permafrost soils, leading to Stefan-type problems. Accounting for water migration for the specific third-type problems on the determination of the radius of frozen soil thawing from production wells in northern oil and gas fields does not significantly affect this process since lateral water migration above the groundwater level is minimal. Therefore, only the latent heat of the initial water content is taken into consideration. This paper discusses a mathematical model containing the most significant physical and climatic data affecting the distribution of thermal fields in permafrost rocks and presents the results of numerical calculations.

Solving multi-dimensional inverse heat problems via an accurate RBF-based meshless technique

Solving multi-dimensional inverse heat problems via an accurate RBF-based meshless technique

Global well-posedness to the 3D Cauchy problem of nonhomogeneous heat conducting magnetohydrodynamic equations with large oscillations and vacuum

We consider the Cauchy problem of nonhomogeneous heat conducting magnetohydrodynamic equations with vacuum in R3. Based on delicate energy estimates, we establish the global existence and uniqueness of strong solutions under some smallness condition. Moreover, we also derive large-time decay rates of the solution. In particular, our smallness condition is independent of any norms of the initial data except the upper bound of the initial density.

Fuel constrained combined heat and power dispatch problem using marine predators algorithm

Fuel constrained combined heat and power dispatch problem using marine predators algorithm

Distribution of radiation heat flux on a plane receiver produced by a multi-quartz lamps heating system for thermal-structural tests

High heat flux generated by quartz lamps can be employed to provide a simulated aerodynamic heating environment for thermal-structural tests on spacecraft. To provide a general numerical solution for radiant heating problems and to investigate the properties of radiation heat flux distributions generated by quartz lamp heaters, a quartz lamp array radiation model is proposed based on Monte Carlo method (MCM). The performance of this numerical model, including result uncertainty and computation time, has been examined. The model is validated through the design and execution of experiments under various radiation intensities. Good agreements between the numerical and experimental results indicates the accuracy and stability of the numerical model for predicting radiation heat flux over a target plane. Then, the impact of various factors on the uniformity and efficiency of radiation dispersal are explored. The results indicate that increasing heater-receiver distance is an efficient strategy for improving radiation uniformity. The reflector is a crucial device for increasing heater efficiency. The edge effect reduces the heat flux within a 10 cm radius of filament ends. A neighboring lamp interval of less than 5 cm is an excellent choice for avoiding radiation troughs and increasing the heater's efficiency.

Electrostatic wave propagation and self-streaming effect in an electron-hole plasma

Electrostatic nonlinear waves which transfer energy through the semiconductor are investigated. A quantum hydrodynamic plasma system composed of self-streaming electrons and holes is examined. The basic equations are reduced to one evolution equation called a modified nonlinear Schrödinger (mNLS) equation. The stability and instability regions are studied with respect to the wavenumber and different plasma effects such as degenerate pressure, Bohm potential, and collisions. The mNLS equation is solved analytically to obtain three kinds of nonlinear envelope wave packet modes. It is found that there are different regions of stability and instability depending on various quantum effects. The electrons’ and holes’ self-streaming velocity is studied and manipulated for the three types of nonlinear envelope waves ‘dark soliton, bright soliton, and rogue wave’. The dark envelope wave packet is generated in a stable region. When the electrons and holes streaming velocities become faster, the wave amplitude becomes taller and the pulses have higher frequency. The bright envelope wave packet exists in the unstable region. For low streaming velocities, the rogue wave amplitude becomes shorter, however, when the streaming velocities reach a critical value the amplitude increases suddenly six times. The self-heating could be produced as the tunneling electrons and holes exchange their energy with the lattice, which may decrease the lifetime of the semiconductors. The present results are helpful in realizing the physical solution to the intrinsic heating problem in semiconductors.