External Heat Source Research Articles

Solution of a Half-Space in Generalized Thermoelastic Problem in the Context of Two Models Using the Homotopy Perturbation Method

This paper estimated the problem of one-dimensional generalized thermoelastic half-space in medium considering two models: the Lord and Shulman (LS) model and the Dual-Phase-Lag (DPL) model. We assumed that the surface of the half-space was free from traction force and under an exponentially varying external heat source at the boundary with time. The technique of homotopy perturbation has been applied to find the approximate solution for the interactions of thermoelasticity with the applied boundary condition. The effect of a heat source that varies with the time and the free traction force are investigated for the temperature, displacement, and stress. The numerical results obtained are presented graphically to show the influence of the new external parameters. The results obtained illustrate the strong impacts on the displacement, temperature, and stress with the variations in the two models as well as the relaxation time parameter. The results show the agreement between the present results and the previous obtained results of the phenomenon and applicable, especially in biology, acoustics, engineering, and geophysics.

Evidence of Electron Heating by Alpha Particles in JET Deuterium-Tritium Plasmas.

The fusion-born alpha particle heating in magnetically confined fusion machines is a high priority subject for studies. The self-heating of thermonuclear fusion plasma by alpha particles was observed in recent deuterium-tritium (D-T) experiments on the joint European torus. This observation was possible by conducting so-called "afterglow" experiments where transient high fusion yield was achieved with neutral beam injection as the only external heating source, and then termination of the heating at peak performance. This allowed the first direct evidence for electron heating of plasmas by fusion-born alphas to be obtained. Interpretive transport modeling of the relevant D-T and reference deuterium discharges is consistent with the alpha particle heating observation.

Similarity rules for inductive radio frequency plasmas with thermohydrodynamic coupling effects

We demonstrate similarity rules for inductively coupled plasmas with thermohydrodynamic coupling effects using two-dimensional fluid simulations and theoretical analyses of the gas flow and heat transfer equations. The results confirm the validity of conventional similarity laws, e.g., the similarity relation for electron density, which can be violated by the nonlinear gas heating effects from exothermic and endothermic reactions. The nonlinear gas heating can obviously perturb the invariance of spatial distributions of the gas flow velocity, resulting in the electron density decreasing nonproportionally with different scaling factors. Adding an external heat source can mitigate the violation of the gas temperature scaling law, thus maintaining the validity of similarity relations to some extent. In addition, two kinds of scaling relations for excited-state argon atoms are identified with and without the consideration of nonlinear collisions.

Enhanced single-loop control of a moving bed temperature swing adsorption CO2 capture process

Using a model in gPROMS, we study a Zeolite 13X-based moving bed temperature swing adsorption (MBTSA) process designed to capture CO2 from a coal-fired power plant. Two enhanced single-loop control strategies were compared to a proportional-integral configuration for variations in power plant load, control variable setpoints, flue gas CO2 concentration and external heat source temperature. Measurement delays were also investigated. Adaptive adjustment of controller parameters with system load gave smoother and narrower manipulated variable profiles and efficient CO2 recovery setpoint tracking. The controller gain is the most important parameter for adaptive tuning. A combined feedback and feedforward scheme showed improved control of the regenerated sorbent temperature, possibly due to better decoupling of the higher-level control loops. When delays were considered, the investigated strategies significantly outperformed the reference case for CO2 recovery control. The results demonstrate that the MBTSA process can be efficiently controlled for several disturbances and changes in operation.

Enhancing sustainable energy conversion: Comparative study of superheated and recuperative ORC systems for waste heat recovery and geothermal applications, with focus on 4E performance

This study investigates the 4E performance of small-scale (<100 kW), low-temperature (<179 °C) Organic Rankine Cycle (ORC) technology, comparing two distinct configurations using different working fluids and heat sources. The work utilizes experimental methods to analyse the efficiency of the ORC systems, focusing on variables such as evaporation temperature and pressure drop across the heat exchanger. Various working fluids and heat sources are tested to evaluate their impact on performance using CoolProp libraries.The results reveal that the ideal evaporation temperature for maximizing overall performance and efficiency is between 140 and 150 °C. Higher pressure drop across the heat exchanger improves heat transfer, thermal efficiency, and power output, but increases pumping requirements and reduces overall effectiveness. Among the tested heat sources, the Dynalene SF exhibits the best performance, followed by therminol T72, T66, geothermal water, and Paratherm HE. The most suitable working fluids for commercial ORC units are R245fa and hexamethyldisiloxane (MM), providing excellent thermodynamic properties and low environmental impact. Comparatively, the superheated ORC system using R245fa outperforms the MM, achieving higher net efficiency (7.29%), greater network generation (20.29%), and improved exergy efficiency (20.54%). The economic viability of the recuperative system is evident from the Levelized Cost of Electricity (LCOE) range of 12.4–14.5 (cents/kWh), with an average Total Installed Cost (TIC) of 354.5 k$. These results showcase the system's competitiveness in providing cost-effective electricity generation, reaffirming its potential as a financially viable option for sustainable energy solutions.The objective is to explore the use of Organic Rankine Cycle (ORC) technology as an alternative to steam Rankine cycle for low-power and lower-temperature applications. Specifically, the study focuses on ORC systems with external heat sources, including geothermal, solid fuels and waste heat recovery (WHR).The novelty of this article lies in its updated analysis of the techno-economic-environmental feasibility of ORC systems for different applications, which goes beyond previous studies. It provides a systematic evaluation and comparison specifically tailored to small-scale and low-temperature operating conditions. The aim is to promote the integration of these two systems in various sectors, particularly for countries undergoing an energy transition. This emphasis on the technical aspects and the specific focus on small-scale and low-temperature conditions make this study unique and valuable in advancing the understanding and application of ORC technology.

Friction stir powder additive manufacturing of Al 6061 alloy: Enhancing microstructure and mechanical properties by reducing thermal gradient

Additive manufacturing of Al alloys by fusion-based processes often leads to higher thermal gradients along the build direction resulting in anisotropy, and solidification-related defects such as porosity, hot-cracking, and lack of inter and intra-layer fusion. Therefore, this paper focuses on solid state multi-layer manufacturing of Al 6061 alloy by friction stir powder additive manufacturing (FSPAM) process and enhancing its microstructure and mechanical properties through reduction of thermal gradient along the build direction by maintaining the substrate close to its artificial aging temperature using external heat source in a close-loop with it. The continuous dynamic recrystallization along with reduced thermal gradient led to homogenous microstructure, fine and equiaxed grains of Al 6061 alloy multi-layer deposition. The inherent compressive forces in FSPAM process promoted intimate contact among the powder particles presenting 0.19% porosity. Energy dispersive spectroscopy showed absence of agglomeration of alloying elements due to better mixing of feedstock material beneath the tool. Phase analysis revealed presence of Al and hardening phase Mg2Si with slight shifting of peaks towards higher angle indicating compressive residual stresses. Tensile properties and microhardness of Al 6061 alloy are closer to AA6061-T4 and better than AA6061-O alloy. Reduced thermal gradient contributed to minimal variations in microhardness (8.8%) along the build direction. Fracture morphology analysis exhibited a significant number of dimples indicating ductile nature of Al 6061 alloy with 16.7% elongation. The study presented a new approach for manufacturing Al alloys using their feedstock in powder form and with improved microstructure and mechanical properties.

Defects influence photocatalytic NOCM product selectivity by controlling photogenerative carriers

Photocatalytic Non-oxidative coupling of methane (NOCM) is a green method to convert methane into high value-added products such as ethane and ethylene by using photogenerated electron-holes. Compared with oxidative coupling of methane (OCM), besides C2 products, H2 is also produced in NOCM process. However, the effect of the photogenerative carriers on the yield and selectivity of photocatalytic NOCM products is still unclear. We tested Au1-ZnO/TiO2 synthesized by NaBH4 reduction and photodeposition in a flowing gas reactor at atmospheric pressure without external heat source. The Au1-ZnO/TiO2-N sample showed a superior C2H6 yield of 0.015 mmol/h accompanied by a small amount of H2 production (1.32 μmol/h). Meanwhile, Au1-ZnO/TiO2-p120 sample shows much higher H2 yield (0.012 mmol/h) and a lower C2H6 yield (4.96 μmol/h). Through varies characterizations, we demonstrated that the selectivity of C2H6 and H2 are highly related to photogenerative carriers. We propose that defects affect the degree of peroxidation in photocatalytic NOCM by controlling the concentration of photogenerated holes.

Solar thermo-photo catalytic hydrogen production from water with non-metal carbon nitrides

Thermo-photo catalytic water splitting for hydrogen generation is a promising method for cascade utilization of full-spectrum solar energy. Herein, two g-C3N4 catalysts were synthesized using a hard-template method with different precursors (melamine for M-CN and cyanamide for C-CN) to investigate the synergistic effect between photo and thermal energies in thermo-photo catalysis. The hydrogen production rates via different pathways, including thermo-photo catalysis (TPC), thermal catalysis (TC), and photocatalysis (PC), were investigated. Results showed that the hydrogen generation rates of M-CN and C-CN catalysts via the TPC pathway at 60 °C under full-spectrum irradiation were 808.4 μmol g−1 h−1 and 1932.9 μmol g−1 h−1, respectively, which were both higher than the sum of the hydrogen production rates via TC and PC pathways, indicating the coupling effect between the photoelectric and photothermal effects of light. The thermo-photo synergy with thermal energy converted from photothermal effect is stronger than that with thermal energy from an external heat source. The mechanism of the synergistic effect was characterized by photoelectrochemical experiments, revealing that higher temperatures promote the separation and migration of charge carriers, providing a microscopic explanation for the improved hydrogen production rate of thermo-photo catalysis.

A Joule-heated carbon nanofiber aerogel-supported catalyst for hydrogen production via methanol steam reforming

Copper (Cu)-containing catalysts are preferable in the methanol steam reforming (MSR) process because of their abundant sources, low cost, and high low-temperature activities. During operation, Cu-containing catalysts are typically heated by an external heat source and are most commonly used in their macroscopic powdered form, leading to uneven temperature distributions, nonuniform mass/heat transfer, slow heating rates, and difficult replacement. These issues must therefore be addressed in the design of specific catalysts for the MSR reaction. Herein, a three-dimensional Joule-heated carbon nanofiber aerogel (CNFA)-supported catalyst (Cu/CNFA-op10) was prepared by a facile one-pot method and followed by the catalytic evaluation. It was found that the even temperature distribution, effective heat/mass/electron transfer, and uniform distribution of the Cu nanoparticles, were responsible for the excellent catalytic activities. In addition, the deactivation of the CNFA-supported catalyst was also found and caused by the aggregation and sintering of Cu0/+ nanoparticles, the deposition of amorphous carbon on the surface of active sites, and the chemical state transition of the active particles. In this proof-of-concept demonstration, the high catalytic activity of the Joule-heating-driven catalyst provides a novel strategy for further designing and fabricating 3D monolithic catalysts related to the MSR reaction.

Fractional simulations for mixed convection flow of hybrid nanofluids due to inclined channel with chemical reaction and external heat source features

The present continuation investigates an unsteady mixed free convective flow of magnetohydrodynamics hybrid nanofluid due to inclined porous plates. The copper, aluminum, aluminum oxide, and gold nanoparticles are utilized to enhance the thermal importance of water-based fluid. The flow is moving through the plates in the existence of a magnetic field. The influences of Newtonian heating, thermal radiation, as well as a chemical reaction on the fluidflow is also examined. The dimensionless equations are fractionalized by the well-known time-fractional operators i.e. Caputo–Fabrizio (CF) and Atangana – Baleanu (AB). The semi-analytical solution to the problem is attained via the Laplace transform. Stehfest, and Tzou,s algorithms are exploited to acquire inverse Laplace transform. A comparison of different numerical schemes computed via Stehfest and Tzou algorithm has been validated and confirmed. The achieved results are clarified by graphical demonstrations and tables.

Entropy optimized flow of Sutterby nanomaterial subject to porous medium: Buongiorno nanofluid model

Owing to enhanced thermal impact of nanomaterials, different applications are suggested in engineering and industrial systems like heat transfer devices, energy generation, extrusion processes, engine cooling, thermal systems, heat exchanger, chemical processes, manufacturing systems, hybrid-powered plants etc. The current communication concerns the optimized flow of Sutterby nanofluid due to stretched surface in view of different thermal sources. The investigation is supported with the applications of external heat source, magnetic force and radiative phenomenon. The irreversibility investigation is deliberated with implementation of thermodynamics second law. The thermophoresis and random movement characteristics are also studied. Additionally, first order binary reaction is also examined. The nonlinear system of the governing problem is obtained which are numerically computed by s method. The physical aspects of prominent flow parameters are attributed graphically. Further, the analysis for entropy generation and Bejan number is focused. It is observed that the velocity profile increases due to Reynolds number and Deborah number. Larger Schmidt number reduces the concentration distribution. Further, the entropy generation is improved against Reynolds number and Brinkman parameter.

Temperature response spatiotemporal correlation model of heat transfer system

For a linear heat transfer system, the unit step response of the temperature field to any system inputs, such as internal and external heat sources, is specific. This means that there is a definite temperature response correlation between any spatial points in the system spatiotemporally, which is independent of the system inputs. It is significant to achieve a quantitative description of the temperature response spatiotemporal correlation between the spatial points for solving the temperature field reconstruction problem of the heat transfer system with unknown inputs. In this paper, a temperature response spatiotemporal correlation model (RSTCM) of the heat transfer system is established originally to reveal the inherent quantitative relationship between the responses of any system spatial points theoretically. Firstly, an external description of the spatiotemporal mapping relationship of the heat transfer process is established according to the heat transfer equations. Furthermore, a basic RSTCM form is proposed and a response spatiotemporal correlation matrix is determined with the help of the external description. Finally, considering the ill-posed characteristic of the response spatiotemporal correlation problem, the regularization technology is employed to transform the original problem into a well-pose problem and to provide a response spatiotemporal correlation matrix with regularization. Effectiveness of the RSTCM is verified by the existing heat transfer experimental data. Besides, adaptability of the proposed model is demonstrated by the achieved numerical experiment results on a two-dimensional heat transfer system.

Review and Design Overview of Plastic Waste-to-Pyrolysis Oil Conversion with Implications on the Energy Transition

Plastics are cheap, lightweight, and durable and can be easily molded into many different products, shapes, and sizes, hence their wide applications globally, leading to increased production and use. Plastic consumption and production have been growing since its first production in the 1950s. About 4% of global oil and gas production is being used as feedstock for plastics, and 3–4% is used to provide energy for their manufacture. Plastics have a wide range of applications because they are versatile and relatively cheap. This study presents an in-depth analysis of plastic solid waste (PSW). Plastic wastes can be technically used for oil production because the calorific value of the plastics is quite comparable to that of oil, making this option an attractive alternative. Oil can be produced from plastic wastes via thermal degradation and catalytic degradation, while gasification can be used to produce syngas. Plastic pyrolysis can be used to address the twin problem of plastic waste disposal and depletion of fossil fuel reserves. The demand for plastics has continued to rise since their first production in the 1950s due to their multipurpose, lightness, inexpensiveness, and durable nature. There are four main avenues available for plastic solid waste treatment, namely, reextrusion as a primary treatment, mechanical treatment as secondary measures, chemical treatment as a tertiary measure, and energy recovery as a quaternary measure. The pyrolysis oil has properties that are close to clean fuel and is, therefore, a substitute to fresh fossil fuel for power generation, transport, and other applications. The study showed that plastic wastes pyrolysis offers an alternative avenue for plastic waste disposal and an alternative source of fossil fuel to reduce the total demand of virgin oil. Through plastic pyrolysis, plastic wastes are thermally converted to fuel by degrading long-chain polymers into small complex molecules in the absence of oxygen, making it a technically and economically feasible process for waste plastic recycling. The process is advantageous because presorting is not required, and the plastic waste can be directly fed without pretreatment prior to the process. Products of plastic pyrolysis are pyrolysis oil, a hydrocarbon-rich gas, with a heating value of 25–45 MJ/kg, which makes it ideal for process energy recovery. Hence, the pyrolysis gas can be fed back to the process to extract the energy for the process-heating purpose, which substantially reduces the reliance on external heating sources.

Thermal Integration of Solid Oxide Electrolysis Cell Systems with External Heat Sources to Maximize Heat Recuperation and Exergetic Efficiency

The purpose of this study is to explain the basis of thermal integration and to investigate the effects of internal and external thermal integration on the whole system performance. The basic concept of the thermal integration of SOEC system is presented while considering internal heat recuperation and coupling with external heat sources. By using temperature-heat transfer analysis, the procedure to design the optimal thermal integration of the SOEC system is described. Based on the proposed system, a parametric study with respect to stack operating conditions (i.e., stack inlet temperature, air utilization, steam conversion, hydrogen fractions) is conducted in order to elucidate their effect on the system level performance. Then, the effects of external heat sources such as steam injection, indirect heat transfer with hot fluids and heat supply by an electrical heater are examined, with pinch analysis and exergetic performance evaluation.

Load Regulation Strategies of Solid Oxide Electrolysis System Coupled with External Heat Sources

Solid oxide electrolysis system requires electrical and thermal energy. Five scenarios are defined according to various cases of external heat sources coupling and electrical energy sources. Three methods are proposed to track variations in electrical or thermal load, including constant flow rate (F method), constant steam utilization (Us method) and constant cell operating voltage (V method). Through system process simulation, the applicability of three methods in different scenarios is explored to obtain load regulation strategies. In the scenario coupled with low-temperature heat and intermittent power and the scenario with no heat coupling, the F method is preferred at high loads and the V method is preferred at low loads, while it is the opposite in the scenario coupled with high-temperature heat and intermittent power. The V method is preferred at low loads in the scenario coupled with low-temperature heat and high loads in the scenario coupled with high-temperature heat.

A New Mode of a Natural Convection Solar Greenhouse Dryer for Domestic Usage: Performance Assessment for Grape Drying

It is known that the natural convection (NC) solar drying process is a simple and cheap method for drying foodstuffs, but it is not preferable for common users in the case of drying high-moisture content agro-products due to the slow rate of drying. Meanwhile, the forced convection (FC) drying process is most appropriate for such products, but its economic feasibility may be affected due to high initial and maintenance costs. Therefore, the present study proposed a controlled natural convection (CNC) drying mode using a solar greenhouse dryer (SGD) for drying grapes with two types of cover materials, glass and Plexiglas, through intermittent operation with a PV system to save energy as a simple and inexpensive domestic dryer instead of the common forced convection SGD and the conventional natural convection SGD. The obtained results of the new CNC drying mode using a Plexiglas SGD showed a higher drying rate than the NC drying mode and are close to the FC drying mode using the same cover material. The initial moisture content of the grapes was reduced from 5.91 g water/g dry matter to the final moisture content of 0.15 g water/g dry matter within 12 h and 15 h for the CNC and NC drying modes, respectively, using the Plexiglas SGD. Moreover, the thermal drying efficiency for the two mentioned drying modes was 12.5 and 9.7%, respectively. The Page model was found to be the most appropriate model to predict the kinetics of the SGD in all drying modes, regardless of the cover type. The new CNC drying mode using the Plexiglas SGD achieved the lowest cost per kg of dried grapes (1.26 USD/kg), the highest total saved costs over the lifespan of the dryer (USD 245.46) and the shortest payback period (1.08 years) compared to the other two dryers, NC-SGD and FC-SGD. Generally, the CNC-SGD had good performance over the NC-SGD because it is not affected by the fluctuation in the volume, velocity and direction of the inlet ambient air/wind during drying grapes as a high-moisture content product without external heating sources or complicated parts. Thus, the proposed drying system has the advantage in terms of simplicity, cheapness and saving energy compared to FC-SGD.

Closed‐Loop Control of Front Speed During Frontal Polymerization of Dicyclopentadiene—A Numerical Study

AbstractThe application of closed‐loop control to enforce a target front speed during frontal polymerization (FP) of dicyclopentadiene under various initial and boundary conditions is demonstrated. Uncontrolled propagation of FP reactions can result in frontal quenching due to heat loss, unstable front propagation, material overheating, spontaneous pattern formation, and heterogenous cured material properties. These disadvantageous properties of FP limit its use to cases with highly controlled initial and boundary conditions. It is shown with results in simulation that these problems can be mitigated in three ways through the application of closed‐loop control. First, it is shown that a target front speed can be enforced by locally controlling the temperature field during FP via an external heat source. Second, it is shown that this method prevents unstable front propagation and quenching despite adverse initial and boundary conditions. Third, it is shown that this method minimizes cure time and energy consumption compared to bulk heating.

Thin Film Thermoelectric Generators for Powerful Applications

The power output of thin film thermoelectric generators (TEG) is not sufficient for large scale applications and is mainly used for low power applications. A thin-film TEG for high-power applications based on a new structure is proposed. The proposed new structure of the TEG ensures the mutual arrangement of flat thermocouples on a thin-film substrate of each layer with the formation of areas of hot and cold junctions, to which heat is efficiently supplied and removed, respectively. Layers are superimposed on each other and stacked in a package. TEGs generate electricity both from the heat of the sun and external heat sources. TEG, due to the high density of thermocouples that generate electricity on the substrates of many layers, generates sufficient power for their use in high-power applications and can be used in various fields as an autonomous source of electricity. Substrates and thermocouples are made of thin films. It is possible to manufacture them in nanoscale.

Parametric Optimization of a Truncated Conical Metal Hydride Bed Surrounded by a Ring of PCM for Heat Recovery.

Metal hydride (MH) hydrogen storage needs an external heat source to release the stored hydrogen. To enhance the thermal performance of MHs, the incorporation of phase change materials (PCM) is a way to preserve reaction heat. This work proposes a new MH-PCM compact disk configuration (i.e., a truncated conical MH bed surrounded by a PCM ring). An optimization method is developed to find the optimal geometrical parameters of the MH truncated cone, which is then compared to a basic configuration (i.e., a cylindrical MH surrounded by a PCM ring). Moreover, a mathematical model is developed and used to optimize the heat transfer in a stack of MH-PCM disks. The optimum geometric parameters found (bottom radius of 0.2, top radius of 0.75 and tilt angle of 58.24) allow the truncated conical MH bed to reach a faster heat transfer rate and a large surface area of higher heat exchange. Compared to a cylindrical configuration, the optimized truncated cone shape enhances the heat transfer rate and the reaction rate in the MH bed by 37.68%.

Mechanisms responsible for the onset of selective laser flash sintering of 8‐YSZ

AbstractSelective laser flash sintering (SLFS) is a variation of flash sintering where the only external heat source is a scanning laser. The scanning laser locally heats a region of the sample between two electrodes, initiating measured current flow at a threshold electric field and laser energy density. This study focuses on understanding how charge transport occurs during stage I SLFS in 8 mol% yttria stabilized zirconia. Two potential charge transport mechanisms are considered: (1) a continuous current moving along a hot line between electrodes and (2) charge transported in a discrete bundle within a hot spot, localized to the area under the laser beam. Two laser scan patterns are employed to experimentally determine how charge is transported during stage I SLFS. Numerical modeling is used to estimate the temperatures at which SLFS initiates, which allows the calculation of charge carrier densities and mobilities relevant for the onset of SLFS. Results demonstrate that both a discrete bundle of charges and continuous flow of charge carriers contribute to the current at the onset of SLFS.