Heat Phenomena Research Articles

Thermal, Lighting and IAQ Control System for Energy Saving and Comfort Management

The present work proposes a simulation and control framework for home and building automation, focusing on heating, ventilating, and air conditioning processes. Control systems based on different advanced control architectures and different control policies are simulated and compared, highlighting control performances, and energy-saving results in terms of CO2 emissions reduction. Heat, lighting, and natural ventilation phenomena were modelized through first-principles and empirical equations, obtaining a reliable and flexible simulation framework. Energy-consuming and green energy-supplying renewable sources were integrated into the framework, e.g., heat pumps, artificial lights, fresh air flow, and natural illuminance. Different control schemes are proposed, based on proportional–integral–derivative advanced control architectures and discrete event dynamic systems-based supervisors; different control specifications are included, resulting in a multi-mode control system. The specifications refer to energy savings and comfort management, while minimizing overall costs. Comfort specifications include thermal comfort, lighting comfort, and a good level of indoor air quality. Simulations on different scenarios considering various control schemes and specifications show the reliability and soundness of the simulation and control framework. The simulated control and energy performances show the potential of the proposed approach, which can provide energy-saving results greater or equal to 6 [%] (in each season) and 19 [%] (in one year) with respect to more standard approaches.

Shape Effect of Nanoparticles on Nanofluid Flow Containing Gyrotactic Microorganisms

In this paper, we discussed the effect of nanoparticles shape on bioconvection nanofluid flow over the vertical cone in a permeable medium. The nanofluid contains water, Al2O3 nanoparticles with sphere (spherical) and lamina (non-spherical) shapes and motile microorganisms. The phenomena of heat absorption/generation, Joule heating and thermal radiation with chemical reactions have been incorporated. The similarity transformations technique is used to transform a governing system of partial differential equations into ordinary differential equations. The numerical bvp4c MATLAB program is used to find the solution of ordinary differential equations. The interesting aspects of pertinent parameters on mass transfer, energy, concentration, and density of the motile microorganisms’ profiles are computed and discussed. Our analysis depicts that the performance of sphere shape nanoparticles in the form of velocity distribution, temperature distribution, skin friction, Sherwood number and Motile density number is better than lamina (non-spherical) shapes nanoparticles.

A Computational Study of Magneto-Convective Heat Transfer Over Inclined Surfaces With Thermodiffusion

In this article, the ocean energy generator system is analysed. The need for sustainable renewable energy systems is continually growing, given the situation of the world’s energy supplies. Numerous similar systems, including photovoltaic solar collectors, biomass, and wind turbines are used for energy generation. The ocean energy generator system uses the magnetohydrodynamics transformation concept to convert kinetic energy to electrical energy. Similar to conventional generators, an ocean generator requires an applied magnetic field to generate current, making it a critical component of the system. To optimize the performance and efficiency of ocean generators, various devices utilizing superconducting magnets have been developed, including Hall current generators, rotating channels, rotating disc magnetohydrodynamics generators, and helicoid generators. However, these systems also involve complex heat, momentum, and mass transfer, which can be better understood through mathematical modeling. The similarity transformation are introduced to transform the mathematical model from partial differential equation system to ordinary differential equation system. By adopting this approach, the numerical solution is significantly simplified while still preserving numerous crucial physical aspects of the studied heat and material transport phenomena. The physical characteristics of sea waves are governed by the three variables of seawater: temperature, salinity, and pressure. Small dispersed particles also affect the generation of hydroelectric power from surface water. The behaviour of velocity, temperature, and salinity profile is observed for the variations of different parameters such as magnetic, Grashof number and heat source. The system is converted into an optimization problem and solved by a neural network procedure. The solutions are compared with reference solutions for validation. The errors, performance, testing and training data are also presented graphically. The data is typically visualized using histograms, line graphs, and other visual aids. This allows for easier comprehension and analysis of the data.

Design of Edge Computing System for Photovoltaic Panel Hot Spot Detection Based on Machine Learning

The hot spot effect of photovoltaic panel refers to the local heating phenomenon caused by the photovoltaic panel being covered, which not only seriously affects the power generation efficiency of photovoltaic panel, but also is one of the most important factors threatening the service life of photovoltaic panel. In this paper, an edge computing system was designed to detect hot spot effect based on real-time sensing data such as current, voltage and illuminance. The system consists of three parts: data acquisition side, data processing side and data display side. The hot spot detection algorithm model based on machine learning is deployed on the edge side, which can detect the degree of hot spot effect and locate the hot spot according to the sensor data of each photovoltaic panel in real time. Additionally, this system could push the data to the cloud management platform and each user terminal to realize remote operation and maintenance.

Evaluating the effects of photovoltaic module heating during electroluminescence inspection

The application of electroluminescence imaging of photovoltaic modules increased in the last years, due to the reliable and detailed identification of degradation and failures. In future plants the time-consuming connection of power supplies could be overcome by use of inverters with bi-directional functionality, allowing backpowering of connected module strings directly. Temperature influences the open-circuit voltage of photovoltaic modules and must therefore be considered during backpowering. This work investigates the heating due to backpowering of photovoltaic modules of different types during electroluminescence inspection. The temperature increase until saturation is estimated by energy balance calculations and experimentally verified to be around 20 °C, with resulting voltage drops of up to 3 V. Further, these changes have an effect on the recorded luminescence intensity: a decrease of the electroluminescence signal intensity between beginning of backpowering and reaching saturation temperature is shown. For application of the results to a real-world scenario, the electroluminescence window of an electroluminescence-ready inverter is introduced, giving the boundaries of current and voltage that can be supplied. Combined with a simulation of the dark current–voltage curves of a connected photovoltaic module string, the electroluminescence inspection possibilities are visualized. Finally, the applicability of this heating phenomenon for snow melting is discussed.

A SIMPLE STUDY OF JOULE HEATING EFFECT IN ARGON DBD REACTOR

Study of the gas heating phenomenon due to the heat joule effect in plasma created by an argon dielectric barrier discharge (DBD) reactor operating under treatment surface and medical sterilization conditions is essential to find the optimum of DBD discharge functioning. The present investigation of the influence of gas heating on argon discharge characteristics was executed by a one-dimensional fluid model. The gas temperature development in the DBD discharge was determined by the heat conduction equation. To consider the joule heating effect, the heat transport equation was solved along the gap distance of discharge. The results obtained from the coupling of a 1D fluid model with the heat conduction equation allowed us to calculate the gas temperature profile of argon in the DBD and plasma physical characteristics such as the densities of charged particles, the voltages, the electric field, and the coefficient rate of the ionization, attachment, and recombination in order to analyze the gas temperature development in argon DBD.

Caputo–Fabrizio fractional model of MHD second grade fluid with Newtonian heating and heat generation

In this research article the heat transfer of generalized second grade fluid is investigated with heat generation. The fluid flow is analyzed under the effects of Magneto hydrodynamics over an infinite vertical flat plate. The Newtonian heating phenomenon has been adopted at the boundary. For this purpose the problem is divided into two compartments i.e. momentum equation and energy equations. Some specific dimensionless parameters are defined to convert the model equations into dimensionless system of equations. The solutions for dimensionless energy and momentum equations are obtained by using the Laplace transform technique. From obtained results by neglecting magneto hydrodynamic effects and heat source some special case are achieved which are already published in literature. The case for which the fractional parameter approaches to the classical order is also discussed and it has been observed that it is convergent. Finally, the influences of different physical parameters are sketched graphically. It has been observed that for increasing values of Prandtl number the velocity and temperature decreases, for increasing values of Grashof number the velocity of the fluid increases. Also it has been investigated that for increasing values of fractional parameter the velocity and temperature of the fluid increases.

Aeroelastic tailoring of composite rudder skin considering variable angle tow laminates by a hybrid backtracking search-JAYA-Sine Cosine Algorithm

Flutter is a typical dynamic instability phenomenon of the wing or rudder structure. Besides, the phenomenon of aerodynamic heating will be quite significant and temperature can rise rapidly with the increase of the flight speed, thermal flutter characteristics should be taken into consideration for the rudder structure of supersonic vehicle. To improve the thermal flutter characteristics of the rudder structure and meet the design requirements of a lightweight structure, this article optimizes the variable stiffness laminates of the skin on the premise of keeping the thickness of the skin unchanged, so as to improve the critical flutter speed of the rudder. A novel intelligent optimization algorithm named BJASCA, which is a hybrid algorithm coupling of Backtracking Search Algorithm, Sine Cosine Algorithm, and JAYA Algorithms is proposed in this article to improve the efficiency of structural optimization and this algorithm shows obvious advantages in searching global optima compared with several other algorithms. The finite element model and aerodynamic model of the rudder are established to calculate the critical flutter speed. The results represent that the rudder structure optimized by the BJASCA algorithm shows better flutter characteristics and the critical flutter speed can be increased by 76.4% compared with the un-optimized structure.

The impacts of shape factor and heat transfer on two-phase flow of nano and hybrid nanofluid in a saturated porous medium

The focus of this article is to obtain the effect of shape factor of the hybrid nanoparticles on the convective heat and mass transference of two immiscible fluids in an inclined duct by employing the perturbation technique. The hybrid nanoparticle of Carbon Nanotube & Sodium alginate is being used with Silicon oil as the base fluid to study the heat and mass phenomena due to the soret effect, viscous dissipation, Darcy and Thermal diffusion. The physical flow problem is then modelled into a set of differential equations. The system of equations is solved analytically to obtain various graphical and numerical results for analyzing the impact of various material parameters on velocity and thermal field. The heat transfer rate and skin friction analysis for the flow dynamics are also investigated. It is observed that the shape factor enhances the fluid flow and temperature distribution. In specific lamina shape particles have better performance comparatively, significance of the soret number can also be observed.

Analysing the role of land use and land cover changes in increasing urban heat phenomenon in Chandannagar city, West Bengal, India

Analysing the role of land use and land cover changes in increasing urban heat phenomenon in Chandannagar city, West Bengal, India

Fundamental Understanding of Heat and Mass Transfer Processes for Physics-Informed Machine Learning-Based Drying Modelling

Drying is a complex process of simultaneous heat, mass, and momentum transport phenomena with continuous phase changes. Numerical modelling is one of the most effective tools to mechanistically express the different physics of drying processes for accurately predicting the drying kinetics and understanding the morphological changes during drying. However, the mathematical modelling of drying processes is complex and computationally very expensive due to multiphysics and the multiscale nature of heat and mass transfer during drying. Physics-informed machine learning (PIML)-based modelling has the potential to overcome these drawbacks and could be an exciting new addition to drying research for describing drying processes by embedding fundamental transport laws and constraints in machine learning models. To develop such a novel PIML-based model for drying applications, it is necessary to have a fundamental understanding of heat, mass, and momentum transfer processes and their mathematical formulation of drying processes, in addition to data-driven modelling knowledge. Based on a comprehensive literature review, this paper presents two types of information: fundamental physics-based information about drying processes and data-driven modelling strategies to develop PIML-based models for drying applications. The current status of physics-based models and PIML-based models and their limitations are discussed. A sample PIML-based modelling framework for drying application is presented. Finally, the challenges of addressing simultaneous heat, mass, and momentum transport phenomena in PIML modelling for optimizing the drying process are presented at the end of this paper. It is expected that the information in this manuscript will be beneficial for further advancing the field.

Evaluation of extractive distillation using efficiency correlation and experimental data

In order to evaluate the behavior of extractive distillation columns efficiency was used the correlation developed by Barros & Wolf, which considers the mass and heat transfer parameters, based on the physical and thermal characteristic of ideal and non-ideal liquid mixtures. The results obtained from Barros & Wolf correlation efficiency were compared with the experimental data obtained by Meirelles. For all cases studied, the solvent used to separate each mixture, reflect on the efficiency values in extractive distillation column. Those factors are more strongly when the interaction between the liquid and vapor phase in the column promote the turbulence, factor predominant on mass and heat transference. The correlation used here shows good approximation when the data from this correlation were compared with that from real profile data obtained by Meirelles, for extractive distillation column. The precision of this correlation is due the mass and heat phenomenon are involved in real process and the behavior efficiency along of distillation column is similar that described in the literature. For this, due the high complexity associated with carried out experiment in laboratory, the correlation used here can be explore to evaluate the profile of extractive distillation operations.

Parametric Analysis of a Solar Water Heater Integrated with PCM for Load Shifting

Integrating a solar water heater (SWH) with a phase change material (PCM)-based latent heat storage is an attractive method for transferring load from peak to off-peak hours. This transferring load varies as the physical parameters of the PCM change. Thus, the aim of this study is to perform a parametric analysis of the SWH on the basis of the PCM’s thermophysical properties. A mathematical model was established, and a computation code was developed to describe the physical phenomenon of heat storage/release in/from the SWH system. The thermal energy stored and the energy efficiency are used as key performance indicators of the new SWH–PCM system. The obtained numerical results demonstrate that the used key performance indicators were significantly impacted by the PCM thermo-physical properties (melting temperature, density, and latent heat). Using this model, various numerical simulations are performed, and the results indicate that, SWH with PCM, 20.2% of thermal energy on-peak periods load is shifted to the off-peak period. In addition, by increasing the PCM’s density and enthalpy, higher load shifting is observed. In addition, the PCM, which has a lower melting point, can help the SWH retain water temperature for a longer period of time. There are optimal PCM thermo-physical properties that give the best specific energy recovery and thermal efficiency of the SWH–PCM system. For the proposed SWH–PCM system, the optimal PCM thermo-physical properties, i.e., the melting temperature is 313 K, the density is 3200 kg/m3, and the latent heat is 520 kg/kg.

Analysis of Soret-Dufour theory for energy transport in bioconvective flow of Maxwell fluid

The present research aims to investigate the effect of binary chemical reaction, thermophoretic velocity, Soret-Dufour, and Joule heating phenomena on the unsteady bio-convected Maxwell fluid flow. The flow is caused by a horizontal stretchable cylinder in the presence of a porous medium. The impact of Lorentz force on flow and heat transport is also investigated here. The whole phenomenon is modeled in the form of partial differential equations (PDEs) and this system is transformed into similar (ODEs) in view of flow similarity analysis. The numerical method (bvp4c) is utilized for the outcomes of temperature, concentration, and micro-organism distributions in the flow of Maxwell fluid. It is perceived that the porosity parameter enhances the temperature, concentration, and micro-organism profile. Bio-convected Peclet number declines the micro-organism profile. Moreover, the temperature field is the decreasing function of the higher thermophoretic parameter.

An analysis of past and future heatwaves based on a heat-associated mortality threshold: towards a heat health warning system

Heatwaves can have severe impacts on human health extending from illness to mortality. These health effects are related to not only the physical phenomenon of heat itself but other characteristics such as frequency, intensity, and duration of heatwaves. Therefore, understanding heatwave characteristics is a crucial step in the development of heat-health warning systems (HHWS) that could prevent or reduce negative heat-related health outcomes. However, there are no South African studies that have quantified heatwaves with a threshold that incorporated a temperature metric based on a health outcome. To fill this gap, this study aimed to assess the spatial and temporal distribution and frequency of past (2014 – 2019) and future (period 2020 – 2039) heatwaves across South Africa. Heatwaves were defined using a threshold for diurnal temperature range (DTR) that was found to have measurable impacts on mortality. In the current climate, inland provinces experienced fewer heatwaves of longer duration and greater intensity compared to coastal provinces that experienced heatwaves of lower intensity. The highest frequency of heatwaves occurred during the austral summer accounting for a total of 150 events out of 270 from 2014 to 2019. The heatwave definition applied in this study also identified severe heatwaves across the country during late 2015 to early 2016 which was during the strongest El Niño event ever recorded to date. Record-breaking global temperatures were reported during this period; the North West province in South Africa was the worst affected experiencing heatwaves ranging from 12 to 77 days. Future climate analysis showed increasing trends in heatwave events with the greatest increases (80%—87%) expected to occur during summer months. The number of heatwaves occurring in cooler seasons is expected to increase with more events projected from the winter months of July and August, onwards. The findings of this study show that the identification of provinces and towns that experience intense, long-lasting heatwaves is crucial to inform development and implementation of targeted heat-health adaptation strategies. These findings could also guide authorities to prioritise vulnerable population groups such as the elderly and children living in high-risk areas likely to be affected by heatwaves.

Tribological performance of (Cr,Al)N+Mo:W:Sg in fluid-free friction regime

Highly loaded contacts in fluid-free-friction regime of uncoated gears lead to early system failures due to frictional heat and wear phenomena such as overheating, fretting as well as wear. A possibility for reducing friction and wear is the incorporation of solid-lubricants such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) by applying physical vapor deposition (PVD) coatings. For this purpose, a (Cr,Al)N hard matrix was modified with Mo, W and S in a graded coating architecture (Cr,Al)N+Mo:W:Sg. Furthermore, coating analyses as well as tribological analyses of (Cr,Al)N+Mo:W:Sg coated 16MnCr5E specimens were conducted in fluid-free friction regime by varying the Hertzian contact pressure between 400 MPa ≤ pH ≤ 1300 MPa against uncoated 100Cr6 counter parts in a pin-on-disc (PoD) tribometer. The results show a high friction and wear reduction independent from Hertzian pressures in fluid-free friction regime. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses of the formed tribofilm prove a chemical composition of oxidic and sulfidic bindings of Mo and W. W forms sulfide-bonded mixed oxide WOmSn but not WS2 opposite to Mo which forms MoxOy and MoS2 within the tribofilm. Based on these results, synergistic effects between WOmSn, MoxOy and MoS2 were assumed.

Toward establishing the presence or absence of horizons in coalescing binaries of compact objects by using their gravitational wave signals

The quest for distinguishing black holes (BH) from horizonless compact objects using gravitational wave (GW) signals from coalescing compact binaries can be helped by utilizing the phenomenon of tidal heating (TH), which leaves its imprint on binary waveforms through the horizon parameters. We investigate the effects of TH on GWs to probe the observability of the horizon parameters, mainly using Fisher matrix analysis to determine the errors and covariances between them. The horizon parameters are defined as $H_1$ and $H_2$ for the two binary components, with $H_{1,2} \in [0,1]$, and combined with the component masses and spins to form two new parameters, $H_{\rm eff5}$ and $H_{\rm eff8}$, to minimize their covariances in parameter estimation studies. In this work, we add the phase contribution due to TH in terms of $H_{\rm eff5}$ and $H_{\rm eff8}$ to a post-Newtonian waveform and examine the variation of their measurement errors with the binary's total mass, mass ratio, luminosity distance, and component spins. Since the Fisher matrix approach works well for high signal-to-noise ratio, we focus mainly on third-generation (3G) GW detectors Einstein Telescope and Cosmic Explorer and use LIGO and Virgo for comparison. We find that the region in the total binary mass where measurements of $H_{\rm eff5}$ and $H_{\rm eff8}$ are most precise are $\sim 20 - 30M_\odot$ for LIGO-Virgo and $\sim 50 - 80M_\odot$ for 3G detectors. Higher component spins allow more precise measurements of $H_{\rm eff5}$ and $H_{\rm eff8}$. For a binary situated at 200 Mpc with component masses $12M_\odot$ and $18M_\odot$, equal spins $\chi_1=\chi_2=0.8$, and $H_{\rm eff5}=0.6$, $H_{\rm eff8}=12$, the 1-$\sigma$ errors in these two parameters are $\sim 0.01$ and $\sim 0.04$, respectively, in 3G detectors. We substantiate our results from Fisher studies with a set of Bayesian simulations.

Pengujian Peluahan Sebagian Menggunakan Rogowski Coil Inti Ferit dan Non Ferit dengan Variaasi Lilitan Sebanyak 10 Lilitan

Partial Discharge is one of the phenomena that occurs in the electric power system, which is characterized by the phenomenon of heat which will disrupt the insulation system. If this phenomenon is left for a long time, it will disrupt the process of distributing electricity, even stopping the process of distributing electricity. Partial discharge testing can be tested in 2 ways, namely conventional using coupling and conventional using electromagnetic methods, optical methods, acoustic methods, and chemical methods. Moisture testing in part in this study uses a non-conventional method with the electromagnetic method. The electromagnetic method used is the Rogowski Coil with ferrite and non-ferrite cores. Each Rogowski Coil core has an inner diameter of 1.2 cm, an outer diameter of 2.5 cm, a height of 2.5 cm and a total of 10 turns. The results of the partial sweat test show that the non-ferrite core Rogowski Coil responds faster than the ferrite core Rogowski Coil. As for the sensitivity level of the second core used for partial discharge testing, it can be seen that the Rogowski Coil with a ferrite core is more sensitive than the non-ferrite core with a sensitivity value of 11.63%.

Cattaneo–Christov heat flux model and multiple slip effect on carbon nanofluid over a stretching sheet in a Darcy–Forchheimer porous medium

AbstractIn several biotechnological processes, multiple slips are the most paramount, such as blood pumping from the heart to different body components, endoscopy treatment, pabulum distribution, and the heat transport phenomenon regulation. In the current research, we have studied the multiple slips, Darcy–Forchheimer, and Cattaneo–Christov heat flux model on a stretching surface exposed to magnetic carbon nanotube nanofluid. We have additionally included a heat source or sink, a chemical reaction for manipulating the heat and mass transport phenomena. The resulting governing partial differential equations have been transformed into ordinary differential equations. With the Runge–Kutta–Fehlberg fourth–fifth‐order procedure, the transformed governing equations are numerically solved. Numerical solutions for different parameters for velocity, temperature, and concentration profiles (Eckert number, velocity slip, thermal slip, mass slip, etc.) are highlighted. Graphical and numerical results for the various parameters in the modeled problem have been outlined. The present numerical results are compared with the published ones for some limiting cases. The slip has been found to control the flow of the boundary layer.

Current and temperature-rise effect of contact condition for connection terminals in UHVDC converter stations

The heating phenomenon of connector terminals in converter stations has become increasingly common, it has become a serious safety hazared affecting the operation of UHV lines. This paper determined the overlapping model of Al plate-Al plate based on the heating phenomenon of connector terminals in converter stations, conducted the tests which included disassembly and assembly contact surface roughness impact test, pressing force impact test, operation impact test, electric composite grease impact test, anti-loosening measure impact test. Analyzed the main influencing factors of current and temperature-rise for connector terminals heating, and analyzed the influence rule of each factor for current and temperature-rise of connector terminals. Test shows that: bolt tightening torque and electric composite grease was the main influencing factors for current and temperature-rise of connector terminals, and bolt tightening moment was the first main factor, bolt looseness and the performance degradation of electric composite grease directly causes an increase in the contact resistance and temperature rise level of the connector terminals.