External Heat Source Research Articles

Finite element analysis for ternary hybrid nanoparticles on thermal enhancement in pseudo-plastic liquid through porous stretching sheet

Thermal performance can be enhanced due to the mixing of nanoparticles in base fluid. This research discusses the involvement of ternary hybrid nanoparticles in the mixture of pseudo-plastic fluid model past over a two dimensional porous stretching sheet. Modelling of energy equation is carried out in the presence of external heat source or sink and viscous dissipation. The flow presenting equations and derived in Cartesian coordinate system under usual boundary layer theory in the form of complex coupled partial differential equations (PDEs). The derived PDEs have been converted into corresponding ordinary differential equations (ODEs) with the engagement of suitable transformation. The engineers, scientists and mathematicians have great interest in the solution of differential equations because to understand the real physics of the problem. Here, finite element scheme has been used to approximate the solution of the converted problem. The contribution of several emerging parameters on solution have been displayed through graphs and discussed. It is recommended that the finite element method can be engaged to approximate the solution of nonlinear problems arising in modelling the problem in mathematical physics.

Valorization of corncob through torrefaction process

Corncobs is a waste of post-harvest corn processing that has great potential to be used as a source of renewable solid fuel. Its high moisture and volatile solids content produces a lot of smoke when corncob is burned, so it is rarely used as fuel. This study aims to improve the quality of corncob fuel through the torrefaction process. The corncob was naturally dried using sunrays for two days and cut into pieces of 1-3 cm in size. The torrefaction process was carried out using a cylindrical rotary reactor which operated at a speed of 30 RPM and was heated using an external heat source. The variations of torrefaction time were 30, 40, and 60 minutes. The parameters to be observed included moisture content, ash content, volatile content, calorific value, and hydrophobicity of materials. The results showed that the torrefaction process improved the quality of corncobs as seen from an increase in calorific value, an increase in hydrophobicity. In this study, the calorific value of the torrefied corncobs was 18.89 MJ/kg to 21.61 MJ/kg, which was higher than the caloric value of the non-torrefied corncobs of 17.66 MJ/kg. The torrefied corncobs are also more hydrophobic and absorb less water than the non-torrefied corncobs.

The controls on the thermal evolution of continental mountain ranges

AbstractThis paper examines the controls on the thermal evolution of continental mountain ranges and investigates how pressure (P) and temperature (T) estimates from metamorphic rocks can be used to reconstruct the thermal histories of orogenic belts. We show that one‐dimensional models can approximate the temperature structure of most continental mountain belts, and find that the metamorphic conditions typical of such tectonic settings can most easily be achieved by thickening of the mid‐ to upper‐crust above a rigid lower crustal substrate. Homogeneous thickening of the entire lithosphere can only result in these conditions under unusual circumstances. This result implies that thickening above rigid lower crust has been the dominant mode of mountain‐building preserved in the rock record. In this situation, modest rates of vertically distributed internal radiogenic heating (1±0.5 μW/m3) are able to produce typical metamorphic conditions and timescales, without the requirement for an external source of heat. In a given model, peak temperature conditions for rocks originally positioned closely in depth (e.g. 5 km apart) occur at times that can be separated by over 10 Myr, highlighting the spectrum of ages and conditions that can be produced by a single geometrically simple mountain‐building event. The direction of approach in P–T space towards the highest‐T conditions experienced by a rock (i.e. the curvature of the P–T loop) is the most diagnostic feature that allows the thermal and tectonic history of a mountain belt to be estimated, highlighting the importance of determining prograde P–T paths. Combining estimates of the peak‐T conditions with multiple other sources of information (e.g. the timescales of metamorphism or the initial crustal thickness) can also allow the reconstruction of the mountain range evolution under most circumstances. Many configurations of continental mountain‐building result in rocks transiently passing through regions with low average thermal gradients (e.g. 10–15°C/km), suggesting that such gradients should not be used to infer the presence of subduction. Analysis of existing P–T loops from the 3.2 Ga metamorphism in the Barberton terrane suggests that mountain‐building processes at that time and place were similar to those in present‐day mountain ranges, implying that large regions of rigid continental lithosphere were already in existence, and were underthrusting the margins of mountain ranges.

Numerical analysis of hydromagnetic mixed convective flow in an internally heated vertical porous layer using thermal nonequilibrium model

AbstractThe inertial and viscous effects on mixed hydromagnetic convection in a vertical porous channel using a local thermal nonequilibrium model with uniformly distributed internal sources are analyzed. The flow in the porous medium is described by the Brinkman–Forchheimer extension of Darcy's momentum equation. The vertical rigid boundaries are maintained at constant but different temperatures and a uniform magnetic field is applied across the porous layer. The governing equations are solved numerically by the finite element method and analytically by the perturbation method. The influence of governing parameters on the flow variables and heat transfer is discussed. An extensive study designates that an increase in the Darcy number enhances the velocity distribution due to increased permeability of the medium while the opposite trend is observed with increasing Hartmann number due to the increased retarding nature of Lorentz force. The presence of an external heat source has a notable impact on the temperature gradient of the fluid, which results in an increase in temperature distribution and thermal state of the fluid. A quantitative increase in heat transfer coefficient results in an increase of fluid temperature toward the electrically nonconducting wall, and as the fluid moves toward the electrically conducting wall the fluid temperature decreases. The results indicate that the Nusselt number declines with an increase in the solid internal heat generation parameter.

An underground anaerobic digester with permissible temperature fluctuations: A parametric study

Many digesters are now abandoned or idle due to high thermal control requirements. Providing a suitable temperature range as well as low temperature fluctuations is essential for the efficient operation of anaerobic digesters. The present study aims to design an un-heated un-insulated cylindrical underground cow manure digester so that it works under permissible thermal conditions during winter. The investigation is carried out by using an in-house code based on the finite difference method and is conducted for Tehran, Iran. The results show that a proper adjustment of design parameters (including burial depth, diameter-to-height ratio and substrate initial temperature) leads to permissible thermal conditions during the whole winter without the need for any external heat source (i.e., only through heat exchange with the surrounding soil). It is observed that for a digester volume of πm3, burial depths of shallower than 5 m and diameter-to-height ratios of lower than 1/2 can lead to undesirable thermal conditions (that is, local temperatures outside the psychrophilic range of 10 °C-20 °C, or temperature fluctuations above 1°C/day). The results also reveal that undesirable temperature fluctuations, which mostly occur during the first day of operation, can be efficiently eliminated through the proper setting of the substrate initial temperature.

Numerical analysis of heat transfer in ring spinning

Improving ring spinning efficiency and yarn quality is still challenging due to the sliding friction heat generated by the ring/traveler system, which limits the traveler speed and the yarn production rate. In this study, a finite element model based on the external heat source method was first used to explore the heat transfer process of the ring/traveler system. The reliability of the model was verified empirically. Subsequently, the validated model was used to analyze the effect of the model parameters on the temperature of the ring/traveler system. The results confirm that the high-temperature region of the ring and the traveler was concentrated on their contact area. More specifically the maximum temperature of the traveler was 159.2°C, which was almost three times the maximum temperature of the ring (62.6°C). In addition, smaller frictional coefficient and yarn tension, larger contact area and heat absorption rate, and better thermal conductivity can reduce the high local temperature of the ring/traveler system. Among them, yarn tension, friction coefficient, and heat absorption rate have a significant influence on the system temperature, especially for the small traveler. The developed model is also available for different fiber types and yarn counts which can be used for a comprehensive investigation of the heat transfer in ring spinning processes. The model and results of this study offer a theoretical basis for further optimizing the ring/traveler system and improving the productivity of ring spinning.

Triggering ambient polymer-based Li-O2 battery via photo-electro-thermal synergy

The limited stability and the excessive dependence on external heating sources restrict the development of polymer-based solid-state Li-O2 batteries. Herein, we propose a multifunctional composed cathode with the photo-electro-thermal synergy to achieve a PEO-based solid-state Li-O2 (PSS Li-O2) battery operating at room temperature. The multifunctional composed cathode consists of the traditional black TiO2 photocatalyst and carbon cloth (b-TiO2/CC). The b-TiO2/CC harvests a full spectrum of sunlight, besides the photo-generated electrons and holes enhancing reaction kinetics during discharging and charging processes, though converting solar energy into heat to achieve self-heated replace on external. The photo-electro-thermal synergy-triggered PSS Li-O2 battery establishes a low overpotential of 0.26 V and long durability of up to 90 cycles, which is a breakthrough for PEO-based Li-O2 batteries operating at room temperature. A flexible PSS Li-O2 battery is constructed and exhibits superior flexibility and mechanical stability. The mechanism of the photo-electro-thermal synergy provides a new strategy for PSS Li-O2 batteries and advances the high-efficiency utilization of solar energy in portable devices.

Thermally radiative flow of Williamson nanofluid containing microorganisms with applications of heat source and activation energy

This theoretical thermal continuation deals with the radiative flow of Williamson nanofluid subject to the inclusion of microorganisms. The further modification in the bio-convective model is done by incorporating the heat source/sink and activation energy phenomenon. The motivation for the choice of Williamson nanofluid is referred to multidisciplinary rheological impact which may enhance the heating phenomenon upon inclusion of nanoparticles. A bidirectional moving surface is the source of inducing flow patterns. The governing expressions which result via thermal model are numerically simulated with a shooting scheme. The impact of flow parameters is identified for velocity change, heat transfer rate, concentration, and microorganism profile. Moreover, the numerical results in terms of different tables are framed out for observing the fluctuated pattern of heat transfer, concentration impact, and microorganism change. The outcomes simulated from the model reflect that a lower velocity rate is results for the velocity ratio parameter. The external heat source attributed the enhancement of heat transfer. Moreover, the concentration profile improves with activation energy and convection constant.

Solving two-dimensional bioheat optimal control problem in solid and vessel domain by pseudospectral discretization

In this paper, an optimal control problem subject to an energy transfer equation in thermally significant blood vessel coupled with the Pennes governing equation is solved. The proposed dynamical system is modeled by a system of conduction-reaction and convection-conduction equations. Chebyshev–Gauss–Lobatto (CGL) and Legendre–Gauss–Lobatto (LGL) points are applied to discretize optimal control problem. Then, the problem transferred into a quadratic programming problem using domain decomposition and matching the solution and its first derivative across the related interfaces. The Tikhonov regularization method is used to compute the optimal regularization parameter for the objective function. Some theories have been discussed to prove that the discrete problem has a solution and it is also consistent with the continuous problem. Numerical results are compared and numerical convergent is shown. Optimal and non-optimal external heat source is compared and it is shown that the mathematical modeling is effective in saving the external heat energy. Numerical results show that by this process of heating at the final time, the temperature is very close to the desired temperature without damaging the vessel domain. Numerical results and corresponding graphs are depicted.

Derivation of Liouville-like equations for the n-state probability density of an open system with thermalized particle reservoirs and its link to molecular simulation

A physico-mathematical model of open systems proposed in a previous paper (Delle Site and Klein 2020 J. Math. Phys. 61 083102) can represent a guiding reference in designing an accurate simulation scheme for an open molecular system embedded in a reservoir of energy and particles. The derived equations and the corresponding boundary conditions are obtained without assuming the action of an external source of heat that assures thermodynamic consistency of the open system with respect to a state of reference. However, in numerical schemes the temperature in the reservoir must be controlled by an external heat bath otherwise thermodynamic consistency cannot be achieved. In this perspective, the question to address is whether the explicit addition of an external heat bath in the theoretical model modifies the equations of the open system and its boundary conditions. In this work we consider this aspect and explicitly describe the evolution of the reservoir employing the Bergmann–Lebowitz statistical model of thermostat. It is shown that the resulting equations for the open system itself are not affected by this change and an example of numerical application is reviewed where the current result shows its conceptual relevance. Finally, a list of pending mathematical and modelling problems is discussed the solution of which would strengthen the mathematical rigour of the model and offer new perspectives for the further development of a new multiscale simulation scheme.

Reconfigurable, Stretchable Strain Sensor with the Localized Controlling of Substrate Modulus by Two-Phase Liquid Metal Cells.

Strain modulation based on the heterogeneous design of soft substrates is an effective method to improve the sensitivity of stretchable resistive strain sensors. In this study, a novel design for reconfigurable strain modulation in the soft substrate with two-phase liquid cells is proposed. The modulatory strain distribution induced by the reversible phase transition of the liquid metal provides reconfigurable strain sensing capabilities with multiple combinations of operating range and sensitivity. The effectiveness of our strategy is validated by theoretical simulations and experiments on a hybrid carbonous film-based resistive strain sensor. The strain sensor can be gradually switched between a highly sensitive one and a wide-range one by selectively controlling the phases of liquid metal in the cell array with a external heating source. The relative change of sensitivity and operating range reaches a maximum of 59% and 44%, respectively. This reversible heterogeneous design shows great potential to facilitate the fabrication of strain sensors and might play a promising role in the future applications of stretchable strain sensors.

Pretreatment methods to enhance solubilization and anaerobic biodegradability of lignocellulosic biomass (wheat straw): Progress and challenges

Agro-waste (wheat straw) is considered most effective (heating value 16 MJ/kg) for energy recovery through anaerobic digestion (AD). However, the complex lignocellulosic structure obstructs their biotransformation and is a rate-limiting step of the AD process. The pretreatment of agro-waste could remove the physical and chemical barriers and accelerate the downstream AD process. The physical pretreatments (mechanical, thermal, sonication) improve the biodegradation kinetics of wheat straw (>50% and can reach up to 92%) but require more energy. High external or internal heat sources may lead to the formation of recalcitrant compounds, i.e., furan derivatives from cellulose. Chemical pretreatment is effective for rapid reaction rate but is uneconomical due to high chemical cost. It may produce toxic intermediary products, and hinder microbial activities in AD. The ionic liquids are emerging chemical pretreatment and are renewable, recoverable, difficult to oxidize, and bio-based salts. The chemical pretreatment induces cellulose loss up to 59% and lignin up to 69%, while the bio-degradability is as high as 88.3%. In biological pretreatment, bacterial pretreatment is superior to fungal and algal pretreatments, and also helps in the substrate bio-degradation during AD. The FTIR, TGA-DTG, XRD, and SEM technologies can validate the efficiency of the pretreatment method, such as modifications in lignocellulosic functional groups, mass loss, crystal feature, surface topography, and morphology of lignocellulosic biomass. Different mathematical models, especially the modified Gompertz model, are employed to facilitate the insight into the AD research. Energy use and balance are necessary for the pretreatment process to figure out the real synergic effects rather than aiming to achieve enhanced methane production.

Electro‐responsive shape‐memory composites obtained via dual‐curing processing

AbstractIn this work, electro‐responsive shape‐memory actuators were developed by incorporating a conductive heater in a dual‐curing thiol‐acrylate‐epoxy shape‐memory polymer (SMP). A conductive heater, consisting of an electrically conductive silver‐ink track printed on Kapton® substrate, was assembled to the SMP, taking advantage of the dual‐curing processing. The shape‐memory effect (SME) was activated by the heat dissipated by the Joule effect in the conductive track. Boron nitride agglomerates were dispersed in the thiol‐acrylate‐epoxy layers to increase thermal conductivity and achieve faster shape‐recovery. A thermoelectric control unit was developed to control the shape recovery of the electro‐responsive actuators and provide different activation strategies. The electrically activated SME was investigated and compared to a traditional SME based on an external heating source given by the dynamic mechanical analyzer (DMA) apparatus. Electro‐responsive actuators were found extremely faster than the conventional SMPs based on external heating. The fastest recovery was obtained by the 15% boron nitride actuator, which recovered the 100% of the original shape in only 8 s. The thermoelectric controlling device provided an optimal control of the shape recovery speed based on the pulse width modulation of the heating current under the application of a low voltage (5 V).

Investigation of thermal performance of Maxwell hybrid nanofluid boundary value problem in vertical porous surface via finite element approach

The study of thermo-physical characteristics is essential to observe the impact of several influential parameters on temperature and velocity fields. The transportation of heat in fluid flows and thermal instability/stability is a charming area of research due to their wider applications and physical significance because of their utilization in different engineering systems. This report is prepared to study thermal transportation in Maxwell hybrid nanofluid past over an infinite stretchable vertical porous sheet. An inclusion of hybrid nanofluid is performed to monitor the aspects of thermal transportation. Keeping in mind the advantages of thermal failure, non-Fourier theory for heat flux model is utilized. Aspects of external heat source are also considered. The mathematical formulation for the considered model with certain important physical aspects results in the form of coupled nonlinear PDEs system. The obtained system is reduced by engaging boundary layer approximation. Afterwards, transformations have been utilized to convert the modeled PDEs system into ODEs system. The converted nonlinear ODEs system is then handled via finite element method coded in symbolic computational package MAPLE 18.0. Grid independent survey is presented for the validation of used approach and the comparative analysis has been done to confirm the reliability of obtained solution. The obtained solution is discussed and physical aspects have been explored and recorded against numerous involved influential variables. Motion into hybrid nanoparticles and nanoparticles becomes slow down versus higher values of Forchheimer and Darcy’s porous numbers. Thermal growth is enhanced for the case of hybrid nano-structures rather than for case of nanofluid. Thickness regarding momentum layer is dominated for hybrid nanoparticles rather than case of nanoparticles.

Numerical simulation of three‐phase‐lag bio‐heat transfer model for generalized coordinate system amidst thermal ablation

AbstractVarious heat transmits models exhibit a thermal response in the tissue during thermal therapies. In the present work, we proposed a three‐phase‐lag (TPL) bio‐heat‐transmitting model including an external laser heating term amidst thermal treatment for the generalized coordinate system. The TPL model is based on the law of heat conduction containing heat flux, temperature gradient, and thermal displacement gradient terms. The solution is determined by implementing a discretization scheme of finite difference in the company of the Runge–Kutta (4,5) technique to examine the temperature repercussion throughout the thermal treatment of the tumor. In addition to this, the impact of various parameters such as phase lag in heat flux, temperature gradient, thermal displacement gradient, the heat generated because of blood perfusion, metabolism, and external heat source term is studied. A comparison has been shown graphically during the thermal treatment. The temperature profile is studied for different coordinate systems, and results are discussed. Moreover, validation has been made of the TPL model used in this paper with the experimental results. Thus the outcomes achieved from this study are purposeful in the therapeutical field, especially for oncologists.

Investigation of phase-change materials for interior temperature regulation in public transport

Abstract Regulating the indoor temperature of public transport on hot sunny days is a prime concern, as both the external and internal heat sources play an active role in heat gain. Experimental studies have been carried out on a bus model using sodium sulphate decahydrate as a phase-change material (PCM) that is placed in between the ceiling and the roof. Studies are conducted on a sunny day and also for different cases of external (300-W surface heater) and internal (25-W light bulb) heat sources. The results show that PCM, in the presence of an external heat source, can help to keep the indoor temperature lower and delay the time period for increasing the temperature by absorbing heat during the phase change. On the other hand, the presence of the internal heat source contributes to a detrimental effect on the indoor temperature, which gradually increases with the elapse of time. With the combination of the external and internal heat sources, it is found that the internal heat source plays a dominating factor to raise the indoor temperature. It is revealed from the experimental results that a 12.7-mm single layer and a single PCM are not enough to counter the internal heat of 25 W unless the thickness of the PCM layer is increased to delay the increase in the indoor temperature. An additional PCM layer with a lower melting temperature could be placed at the inner portion of the ceiling to have effective thermal-energy storage by absorbing the substantial heat gain from the internal heat sources.

Spatial matching relationship of dual heat sources in electromagnetic heating of pipes

• Dual heat sources reduce the probability of latent defects in electromagnetic heating. • The mechanism of the interference of dual heat sources on the induced magnetic field. • Reveal the spatial matching relationship of dual heat sources under moving conditions. In medium-frequency heat treatment, it is difficult to thoroughly heat the interior of welds of heavy-wall pipes, and blind zones of heating or overheating zones with latent defects are very readily present. To solve the electromagnetic-heating-induced latent defects, we researched the mode of heat transfer inside the welds with heat sources under motion conditions to determine the temperature field evolution, spatial magnetic field distribution, and spatial matching relationship in cases of dual heat sources interfering with each other, tangential to each other, and not interfering with each other. With the increase in the axial spacing between the internal and external heat sources, the magnetic field intensity at the middle of the thickest part of the welding seam on the steel pipe increased and then decreased. When the heat sources interfered with each other, the temperature rise at the weld center from electromagnetic heating was no longer fast after the Curie point was reached. The induced magnetic field heating concentration positions shifted toward both sides of the weld center. The latent defect area was reduced by 18.7 mm 2 when the spacing between the internal and external heat sources was 19 mm. This study explores the dual-heat-source interaction mechanism for the first time in the heat treatment of pipes to minimize the blind zones of heating and overheating zones.

Mathematical modelling of the effect of gaseous plasma on microorganisms on surfaces

For the targeted adjustment of parameters of gaseous plasma used for treatment of surfaces polluted with various pathogenic microorganisms, mathematical modelling of the process of an unsteady heat transfer in a plate (flat substrate) under the action of an external heat source is carried out. The effect of gaseous plasma on microorganisms located on the steel plates was experimentally studied with the purpose of sterilization of the surface. In this case, the biophysical effect of plasma combines the action of three phenomena on microorganisms: active ions, electric field and ultraviolet irradiation.

Dissimilar use of an external heat source for thermoregulation by shrews from different geographic regions

Ambient temperature has a substantial influence on the thermoregulation costs of small mammals due to their high surface-to-volume ratio. Shrews are among the smallest of mammals and have adopted different behavioral and physiological strategies to deal with cold temperatures. In this study, we assessed the use of an external heat source in the thermoregulatory strategy of two Crocidurinae species, Crocidura russula and C. suaveolens, and one Soricinae species, Sorex araneus. Crocidura russula inhabits western Europe and is better adapted to a Mediterranean climate; C. suaveolens inhabits central Europe; and S. araneus inhabits northern Europe and is better adapted to a Palearctic climate. We predicted that C. russula (most southern species) would spend larger amounts of time using an external heat source because it is the most cold-sensitive species, while S. araneus (most northern species) would spend less time using an external heat source or not respond to it. Shrews were experimentally tested in captivity inside a terrarium where they had access to a heat rock, which could be turned off (cold) or on (heated), depending on treatment. Our results confirmed our initial prediction: C. russula was the species that spent significantly more time on the heated rock, followed by C. suaveolens. Only a quarter of S. araneus individuals spent large amounts of time on the heat rock, which suggests this thermoregulation strategy is not generally adopted by this species, but may be rather associated with some individual personalities. We also analyzed the influence of the heat rock on rewarming from heterothermy, but heterothermy was not different between rock treatments. Overall, our results show that shrew species use external heat sources for thermoregulation according to their sensitivity to cold.

Oscillatory Blood Flow and Embolitic Plaque Effect Through a Microchannel with Metabolic Heat and Magnetic Field

An attempt was made to investigate an embolitic plaque effect on blood flow through a microchannel and the impact of the magnetic field, metabolic heat, and external heat source on improving blood flow. To address the aforementioned objectives, mathematical models were developed for blood flow and heat transfer with a source. The governing models were scaled using the dimensionless quantities, and the plaque area was derived from Dominguez [28], in which it was incorporated into the governing equations. The governing equations were further reduced to ordinary differential equations using the perturbation method, and the subsequent ordinary differential equations were solved using the method of undermined coefficients, and the constants obtained with the help of the matrix method using the boundary conditions. Furthermore, simulation was carried out to study the effect of the pertinent parameters using Wolfram Mathematica, a computational software. From the simulated results, it is seen that the entering parameters such as magnetic field parameter, the Reynolds number, Womersley number, oscillatory frequency parameter, and permeability parameter all affect the blood velocity and temperature profiles, showing significant impactful results that are useful to both mathematicians and clinicians.