Heat Mechanisms Research Articles

Solute dispersion in micropolar-Newtonian fluid flowing through porous layered tubes with absorbing walls

The physical mechanism of heat and mass transfer in solute dispersion in a two-fluid model of the blood flow through porous layered tubes with absorbing walls has been studied in the present work. For a more realistic representation of the blood flow in microvessels, the two-fluid approach is employed by considering the fluid in which the blood particles like RBCs, WBCs, and platelets are suspended as a micropolar fluid in the core region and the cell-free layer of plasma as Newtonian fluid in the peripheral region. A thin Brinkman layer mathematically governed by the Brinkman equation replicates the mechanical aspects of the porous layer near the tube wall. Either no-spin or no-couple stress condition at the micropolar-Newtonian fluid interface has been taken in to account to compare our findings with previous studies and the stress-jump condition of Ochoa-Tapia and Whitaker (J.A. Ochoa-Tapia and S. Whitaker, Int. J. Heat Mass Transfer 38 (1995) 2635–2646) is employed at the fluid-porous interface. A uniform magnetic field has also been applied in the transverse direction of the flow pattern to understand some of the clinically relevant aspects of blood flow in the cardiovascular system. Analytical expressions for the velocity and temperature field are used to obtain the expressions for diffusion coefficients and mean concentration by following the method of Sankarasubramanian and Gill (R. Sankarasubramanian and W.N. Gill, Proc. R. Soc. London. Ser. A 333 (1973) 115–132), to analyze the solute dispersion process in fluid flowing through tubes with wall reactions. The effect of plasma layer thickness, radiation parameter, coupling number, micro-rotation, thermal conductivity, Hartmann number, and permeability on the diffusion coefficients and mean concentration of the miscible species are discussed and depicted graphically. The multi-motivational work with the combination of a porous layer near the wall and heat transfers may leave a significant impact on drug delivery through the blood vessels for the treatment of cardiovascular diseases.

Intensification of foam technology by the energy of the electrohydrothermal power field. Part 3. Investigation of the processes of heat and mass transfer in the foam system under the influence of EHTPF

As a result of thermal expansion in the foam mass of the gas phase, which acts as a sealing component in a closed volume, excessive internal pressure is generated and fields of pressure, temperature, and moisture content are formed. Particular flows of liquid arising from these fields are directed from the center to the perforated walls of the form with a distance beyond it. In EHTPF, there are three partial flows of moisture that make up a single flow in the mass. Thus, self-compaction is accompanied by heat and mass transfer processes. At low temperatures, moisture moves in the material in the form of a liquid, and at high temperatures, in the form of vapor. The density of the total moisture flow can be represented as the sum of the densities of private flows. An analytical study of the mechanism of heat and mass transfer flows allows one to analyze the behavior of the foam mass during heatpower treatment and to choose the best conditions for it.

A mathematical model to examine the heat transport features in Burgers fluid flow due to stretching cylinder

In this article, a new mathematical modelling is presented for the flow of Burgers fluid induced by a stretching cylinder in the presence of magnetic field. Moreover, the mechanisms of heat and mass transport are also examined by using the law of conservation of energy with Fourier’s and Fick’s laws for thermal and solutal energy, respectively. The ordinary differential equations (ODEs) are attained from partial differential equations by making the use of dimensionless similarity transformations. The homotopic approach is being adopted to solve the developed ODEs. The influences of different physical parameters on velocity, thermal and concentration profiles are pondered through graphs and physical behavior of these parameters is enlightened with the realistic verdicts. The basic physical intimation of pertained results is that the temperature and solutal curves of Burgers liquid show the enhancing trend for larger scales of relaxation time parameter $$\left( \beta _{1}\right)$$ and for material parameter of Burgers fluid $$\left( \beta _{2}\right)$$ while, opposing behavior is being observed for retardation time parameter $$\left( \beta _{3}\right)$$ . Moreover, it is assessed that the concentration rate and solutal boundary layer thickness decline with an intensification in Lewis number (Le). Also, it is noted that the temperature distribution enhances/declines with higher values of heat source and sink parameter, respectively.

Analysing the Effect of Substrate Properties on Building Envelope Thermal Performance in Various Climates

Existing regulations on the thermal efficiency of building envelope assemblies are based on the steady state thermal properties of substrate materials. Heat transfer mechanisms of passive heat curbing methods such as phase change materials and cool materials, which are dynamic in nature, are currently not being accounted for. The effectiveness of thermo-physical and solar radiation properties of building materials (i.e., solid homogeneous layers without air gap) in reducing the heat gain into a building in a hot climate could be well understood with the equivalent thermal resistance (Req) concept. A simple and easy-to-use mathematical derivation (i.e., to estimate the instantaneous heat flux across an envelope assembly) is proposed in this paper to understand the mechanism of equivalent R-value (i.e., reciprocal of thermal transmittance, U-value) due to solar radiation properties of passive substrate materials. The model is validated against field experiments carried out at two apartment units of a residential building. The Req due to high outer surface solar radiation properties (i.e., by applying a cool coating) is dynamic as it varies with the weather conditions. The effect of a substrate material’s solar radiation and thermo-physical properties on the overall roof thermal performance is investigated using the Req model for four cooling dominated climates around the globe, having different diurnal conditions and sky temperatures. Increasing the outer surface’s solar reflectance (from 10% to 80%) reduces net heat gain through the flat roof during both daytime and nighttime. In contrast, adding only thermal resistance (from 5 mm to 75 mm thick polyurethane) or volumetric heat capacity (by adding 5 mm thick phase change material) to the building envelope brings down heat gain during the day, but not in the night. Thermal insulation is found to be the second effective property, followed by thermal mass irrespective of different diurnal conditions and sky temperatures across the climates.

Atmospheric and Land Surface Contributions to Heatwaves: An Australian Perspective

AbstractHeatwaves are associated with prolonged hot conditions that accompany a quasi‐stationary anticyclone. This is a consequence of different heat mechanisms including subsidence, horizontal heat advection, and sensible heating from the land surface. Understanding the relative contribution of each of these heat mechanisms is important for improving the predictability of heatwaves. However, the evolution of heatwaves can vary depending upon antecedent conditions, and therefore, it is necessary to examine the role of both atmospheric processes and land surface conditions together. Using a regional climate model, we simulate five heatwaves that occurred over different parts of Australia. Using Lagrangian back‐trajectories to inform the atmospheric flow preceding each of the heatwave events, we perturb the evaporative fraction where and when the flow enters the boundary layer. We aim to understand the role of land surface energy partitioning on two of the heat mechanisms and identify under what circumstances it has limited influence on a heatwave. We find that the sensitivity to changes in land surface energy partitioning varied considerably between the events. Advection was critical by either enhancing the accumulation of heat into the affected location or for dissipating the event by ventilating the region with cooler air. Convective precipitation was triggered when increasing the evaporative fraction due to a warm atmosphere and more moisture supplied by the land surface. Finally, the contribution of each of the heat mechanisms varied between the events due to atmospheric and land surface processes and therefore generalizing the contribution of these mechanisms to heatwaves should be avoided.

Thermodynamic characteristics of moxa floss and its biological effects and therapeutic mechanism on osteoarthritis rats

Moxa floss is the main material of moxibustion, which plays a therapeutic role through the thermal effect of combustion. In this paper, TG/DSC thermal analysis method was used to study the characteristic parameters of combustion heat of moxa floss produced in Qichun, and the thermal therapeutic effect and mechanism of moxibustion were studied through moxibustion OA animal model. The results show that the combustion process of moxa floss can be divided into three stages: drying, combustion oxidation and carbonization, and ash burnout. The combustion properties of moxa floss are between herbaceous and woody, and tend to be woody, with flammable, slow and lasting combustion characteristics. Moxibustion can relieve the pathological state of knee joint synovium to a certain extent, reduce knee joint swelling and blood stasis in OA rats, reduce interstitial edema, and improve local inflammation. The mechanism and target point of moxibustion treatment for OA may be up-regulating TRPM3 gene to activate ion channels, affecting calcium metabolism and reducing OA swelling degree; down-regulation of GAPDH affects glucose metabolism of knee synovial cells and mediates anti-inflammatory effect. Down-regulation of pain-related gene MMP24 is helpful to relieve OA pain. Up-regulation of CTNNB1 activates Wnt/β-catenin signaling pathway and affects differentiation and regeneration of OA chondrocytes. This study reveals the pyrolysis characteristics of moxa floss for the first time and discusses the biological effect and possible mechanism of moxibustion heat, providing new ideas for the quality evaluation of moxa floss and the mechanism of moxibustion therapy.

ВЛИЯНИЕ РАДИАЦИОННОГО ТЕПЛООБМЕНА НА ИНТЕНСИФИКАЦИЮ ТЕПЛОПЕРЕНОСА В ТОНКОПЛЕНОЧНОЙ ТЕПЛОВОЙ ИЗОЛЯЦИИ

Актуальность исследования обусловлена тем, что тепловая защита оборудования и трубопроводов играет важную роль при проведении энергосберегающих мероприятий на энергетических объектах различного назначения, а рост уровня потерь тепла или холода при транспортировке энергоносителей является причиной создания новых подходов к энергосберегающим мероприятиям при выполнении теплоизоляционных работ. Известно, что основным методом снижения потерь тепловой энергии при ее транспортировке и хранении является применение высокоэффективных теплоизоляционных материалов. Таким материалом является тонкопленочная тепловая изоляция. Уникальные теплофизические характеристики тонкопленочных теплоизоляционных покрытий позволяют использовать их в различных энергетических системах и оборудовании. Несмотря на это технологии применения тонкопленочных теплоизоляционных покрытий к настоящему моменту времени не получили развития. Это объясняется рядом причин, основными из которых являются: недостаток знаний о физических свойствах и механизмах процессов тепломассопереноса в тонкопленочных теплоизоляционных покрытиях. Цель: исследование кондуктивно-конвективно-радиационного теплопереноса в слое тонкопленочной тепловой изоляции с учетом разнородности свойств микросфер и связующих веществ. Объект: цилиндрический слой тонкопленочного теплоизоляционного покрытия. На внутренней и внешней поверхностях теплоизоляционного покрытия поддерживаются постоянные температуры. Геометрия тонкопленочного теплоизоляционного покрытия представляла собой связующее вещество и полые микросферы. Исследования проводились для слоя теплоизоляции толщиной 0,33 мм. Температура на внутренней и внешней поверхностях изоляции принималась в соответствии с экспериментальными данными. Предполагалось, что слой тонкопленочной теплоизоляции на 62 % состоит из микросфер диаметром 50 мкм и на 38 % из связующего вещества. Рассматривались два типа полых микросфер с толщинами стенок: 5 и 2 мкм. Методы. Решение поставленной задачи получено методом конечных элементов. Использовалась аппроксимация Галеркина, неравномерная конечно-элементная сетка. Параметры элементов сетки выбирались из условий сходимости решения. Увеличение числа элементов расчетной сетки проводилось с использованием метода Делоне. Результаты. Установлены величины тепловых потоков в слое тонкопленочной тепловой изоляции при наличии радиационного теплообмена. На основании сопоставления результатов численного моделирования теплопереноса в слое тонкопленочной тепловой изоляции, выполненного с использованием кондуктивно-конвективной модели теплопереноса, с результатами для кондуктивно-конвективно-радиационной модели установлено, что расхождение между ними не превышает 0,1 % и объясняется погрешностями численных расчетов. По этой причине в практических расчетах можно использовать более простую кондуктивную модель теплопереноса.

Characteristic analysis of heat loss in multistage counter-flow paddy drying process

Drying is one of the most important and high-energy consumption unit operations in post-harvest treatment and storage of paddy, and heat loss is a major factor affecting drying efficiency and energy consumption of paddy drying process. To reveal the heat loss characteristics of paddy drying system, a multistage counter-flow drying process of industrial scale dryer was designed based on the conservations of energy and mass, thermodynamics theory and mechanisms of heat and mass transfer. And variation characteristics of heat loss in multistage counter-flow paddy drying process were investigated using psychrometric chart. Meanwhile, parameters of heat and mass transfer were used to analyse the experimental results of heat loss in multistage counter-flow drying. Results indicated that the method of analysing the variation characteristics of heat loss by using psychrometric chart was feasible, and heat losses of drying system were significantly affected by paddy properties, state parameters of drying medium and flow state. Furthermore, the specific heat losses of paddy warming, evaporated water vapour warming, exhaust and other were respectively in ranges of 75.33–238.92 KJ/kg, 2.61–4.67 KJ/kg, 54.34–757.76 KJ/kg and 33.44–236.28 KJ/kg. In high temperature drying segment, the maximum heat losses of the first high temperature drying chamber and other high temperature drying chambers were the heat loss of paddy warming and other heat loss, respectively. The maximum heat loss in all low temperature drying chambers was the heat loss of exhaust, and the heat loss for evaporated water vapour warming was the smallest in any drying chamber. Additionally, energy-saving measures were proposed based on the heat loss characteristics in industrial scale dryer.

Research on the Indoor Physical Characteristic of the Ceiling of China National Aquatics Center under the Demand of Olympic Games

In the practice of the Beijing Olympic Winter Games in 2022 for the renovation and reuse of the 2008 Olympic legacy venues, PVC film-based clips integrated with the black coated fabric were employed as a shielding material, to reduce the influence of sunlight under the ethylene tetrafluoroethylene (ETFE) air pillow ceiling system and maintain a good and stable indoor environment. Based on winter outdoor meteorological parameters, we measured the temperature; solar irradiance; and illuminance of the playing field, as well as the upper and lower surfaces of the ceiling enclosure and its internal cavity. Meanwhile, a simulation of the indoor environment before and after the shielding was carried out. The distribution and transmission mechanism of light, humidity, and heat in the venue were studied. It was found that the shielding material can block more than 98% of the sunlight and solar radiation; and after the addition of shielding material, the temperature of the playing field changes throughout the day about 1 °C. The difference between the surface temperature under the ceiling and the indoor temperature is about 3 °C, which is not easy to condense. The physical characteristics of the shielding of the roof enclosure structure are revealed, and the shading and heat insulation performance of it is verified, so that the venue meets the requirements of the Olympic Winter Games in the indoor environment.

Assessment of future climate change impacts on water-heat-salt migration in unsaturated frozen soil using CoupModel

The transport mechanisms of water, heat, and salt in unsaturated frozen soil, as well as its response to future climate change are in urgent need of study. In this study, western Jilin Province in north-eastern China was studied to produce a model of coupled water-heat-salt in unsaturated frozen soil using CoupModel. The water, heat, and salt dynamics of unsaturated frozen soil under three representative concentration pathway (RCP) scenarios were simulated to analyze the effects of future climate change on unsaturated frozen soil. The results show that water, heat, and salt migration are tightly coupled, and the soil salt concentration in the surface layer (10 cm) exhibits explosive growth after freezing and thawing. The future (2020–2099) meteorological factors in the study area were predicted using the Statistical Downscaling Model (SDSM). For RCP2.6, RCP4.5, and RCP8.5 scenarios, future temperatures during the freeze-thaw period increased by 2.68°C, 3.18°C, and 4.28°C, respectively; precipitation increased by 30.28 mm, 28.41 mm, and 32.17 mm, respectively; and evaporation increased by 93.57 mm, 106.95 mm, and 130.57 mm, respectively. Climate change will shorten the freeze-thaw period, advance the soil melting time from April to March, and enhance water and salt transport. Compared to the baseline period (1961–2005), future soil salt concentrations at 10 cm increased by 1547.54 mg/L, 1762.86 mg/L, and 1713.66 mg/L under RCP2.6, RCP4.5, and RCP8.5, respectively. The explosive salt accumulation is more obvious. Effective measures should be taken to prevent the salinization of unsaturated frozen soils and address climate change.

Self-consistent method to extract non-linearities from pulsating star light curves – I. Combination frequencies

ABSTRACT Stellar pulsation is a common phenomenon and is sustained because of coherent driving mechanisms. When pulsations are driven by heat or convective mechanisms, it is usual to observe combination frequencies in the power spectra of the stellar light-curves. These combination frequencies are not solutions of the perturbed stellar structure equations. In dense power spectra from a light-curve of a given multiperiodic pulsating star, they can compromise the mode identification in asteroseismic analyses, and hence they must be treated as spurious frequencies and removed. In this paper, a method based on fitting the set of frequencies that best describes a general non-linear model, like the Volterra series, is presented. The method allows these frequencies to be extracted from the power spectrum, thereby improving the frequency analysis and enabling hidden frequencies to emerge from what was initially considered as noise. Moreover, the method yields frequencies with uncertainties several orders of magnitude smaller than the Rayleigh dispersion, which is sometimes used as if it were an error when identifying combination frequencies. Furthermore, it is compatible with the classical counting cycles method, the so-called O-C method, which is valid only for mono-periodic stars. The method creates the possibility of characterizing the non-linear behaviour of a given pulsating star by studying in detail the complex generalized transfer functions on which the model is based.

Thermohydraulics of Alkaline Liquid-Metal Coolant: A Retrospective-Perspective Look

Sixty years of experience in mastering alkaline liquid metals jointly with industry institutes, the Academy of Sciences, and engineering design agencies developing Nuclear Power Facilities (NPF) has culminated in the development of the scientific foundations for their use in nuclear power and the scientific substantiation of the hydraulic parameters and highly efficient technological processes ensuring successful operation of fundamentally new NPF. The primary directions of research were the hydrodynamics of and heat transfer in channels with complicated shapes and in nominal and deformed fuel-rod assemblies, including the blocking of flow sections, and the mechanisms of turbulent heat and mass transfer, interchannel mixing of the coolant, and the hydrodynamics of collector systems in reactors and heat-exchange equipment. Significant attention was devoted to heat exchange in intermediate heat-exchangers and steam generators of reactor facilities and the boiling and condensation of liquid metals. Questions concerning the generalization and experimental thermophysical databases, development of heat pipes, thermophysics of thermionic converters, high-temperature space NPF, and thermonuclear plants were examined. Future studies resulting from the need to improve the safety, cost-effectiveness, and reliability of developed nuclear power facilities are formulated.

Pea Gβ subunit of G proteins has a role in nitric oxide-induced stomatal closure in response to heat and drought stress.

Heterotrimeric G proteins consisting of Gα, Gβ and Gγ subunits act as downstream effectors to regulate multiple functions including abiotic stress tolerance. However, the mechanism of Gβ-mediated heat and drought tolerance is yet to be established. To explore the role of Pisum sativum Gβ subunit (PsGβ) in heat and drought stress, transgenic tobacco plants overexpressing (OEs) PsGβ were raised. Transgenic plants showing ectopic expression of PsGβ performed better under heat and drought stress in comparison with vector control plants. The seed germination, relative water content (RWC) and nitric oxide (NO) induction in the guard cells of transgenic plants were significantly higher in contrast to control plants. PsGβ promoter was isolated and several stress-responsive elements were identified. The change in Gβ expression in response to heat, methyl jasmonate (MeJA), abscisic acid (ABA), drought and salt confirms the presence of heat, low temperature and drought-responsive elements in the PsGβ promoter. Also, heat and drought stress caused the release of NO-induced stomatal closure in the leaves of transgenic tobacco plants OEs PsGβ. The better performance of transgenic plant OEs PsGβ is also attributed to the improved photosynthetic parameters as compared with control plants. These findings suggest a role of PsGβ in the signalling pathway leading to NO-induced stomatal closure during heat and drought stress.

Role of Variable Conductance on Heat and Mass Transport Mechanism Using Generalized Theory

Abstract Fourier law of heat conduction, its analog Fick's first law, and Newton's law of viscosity are classical laws that are not capable of exhibiting memory effects. Conservation laws based on these classical laws do not give predictions about memory effects on the transport phenomena. Recently, proposed novel laws are called Cattaneo–Christov heat flux. Models are based on the generalization of classical laws of heat conduction, mass diffusion, and Newton's law of viscosity. This investigation considers this generalized theory to model the impact of relaxation phenomenon on the transport of momentum, heat, and mass in Maxwell fluid (viscoelastic fluid) of temperature-dependent viscosity and thermal conductivity in the presence of temperature-dependent mass diffusion coefficients. It is observed from the simulations that memory effects play a key role in controlling momentum, thermal and concentration boundary layer thicknesses. It is also noted that the rate of diffusion of heat and mass has shown an increasing trend when thermal conductivity and mass diffusion coefficients are increased via rise in temperature of the fluid. The generative chemical reaction on the transport of specie relative to the impact on the transport of specie when it is compared with the impact of destructive chemical reaction on the transport of specie.

On heat and mass transfer using evaporating self-rewetting mixtures in microchannels

Evaporation heat and mass transfer in open microchannels was investigated using pure liquids (ethanol, deionized water and butanol), an ordinary (non-self-rewetting) mixture (5% v/v ethanol/water mixture) and a self-rewetting fluid (5% v/v butanol/water mixture). The applied heating power ranged from 0 mW to 282.76 mW (giving heat fluxes from 0 W/m2 to 4501 W/m2) with wall temperatures ranging from 24 °C to 95 °C. When the microchannel had no external heating, diffusion was found to be the main mechanism of mass transfer. With external heating, the diffusion model underestimated the experiment results, and buoyancy-driven convection may account for this. Evaporation rates remain high for the self-rewetting fluid even when the meniscus recedes significantly (by 6 times the inner diameter) in the microchannel under heating conditions. Additionally, the self-rewetting fluid showed the highest conduction rate in the axial direction in high heating power conditions. Meniscus-wall contact angles and flow visualizations were obtained for various heating rates. The “contact angle shift” phenomenon of the self-rewetting fluid was observed. Marangoni-induced convection in the microchannel accounts for the mechanism of better heat and mass transfer as well as the “contact angle shift” phenomenon for the self-rewetting fluid.

Defect-rich honeycomb-like nickel cobalt sulfides on graphene through rapid microwave-induced synthesis for ultrahigh rate supercapacitors

Nickel cobalt sulfides (NCS) are regarded as potential energy storage materials due to the versatile valent states and rich electrochemical activity, but their sluggish synthesis process and inferior rate performance hinder them from large-scale application. Herein, microwave-induced strategy has been employed for efficient synthesis of honeycomb-like NCS/graphene composites, which are explored as ultrahigh rate battery-type electrodes for supercapacitors. Due to the internal heat mechanism, the synthesis time of NCS by microwave could be shortened from hours to minutes. Density functional theory was simulated to uncover the interfacial effect between NCS and graphene, and the resulted Schottky barrier is in favor of enhancing redox activity and capacity. Ultimately, the obtained defect-rich nickel cobalt sulfides/graphene with thermal treatment (NCS/G-H) could exhibit a high specific capacitance of 1186 F g−1 at 1 A g−1 and sustain 89.8% capacity even after the increase of current density over 20 times, which is much superior to bare NCS and NCS/graphene. Furthermore, the assembled NCS/G-H hybrid supercapacitor delivers supreme energy density of 46.4 Wh kg−1, and retains outstanding long-term stability of 89.2% after 10 k cycles. These results indicate that the synthesized NCS/G-H by time-saving microwave-induced liquid process could be served as high rate materials for supercapacitors.

Flow of Oldroyd-B Fluid over a Rotating Disk Through Porous Medium with Soret–Dufour Effects

A study of Darcy flow of magnetized Oldroyd-B fluid over a rotating porous disk is analyzed. The heat and mass transport mechanism are analyzed with the significant features of thermal diffusion (Soret) and diffusion thermo (Dufour). Additionally the influence of chemical reaction is also considered on solutal field. The Von Karman transformations are used and in order to obtain the similarity equations which are then integrated numerically on $$\left[ 0,\infty \right) $$ through BVP Midrich technique in Maple. The results are given through graphical structure and tabular form. A brief parametric survey is conducted against velocity fields, temperature and concentration distributions in the form of graphs. The corresponding heat transfer rate and wall concentration gradient are displayed through tables with different physical effects. The comparison tables are presented to assure the validity of our numerical scheme with the past outcomes. It is revealed that the velocity fields decline with the effect of porosity parameter. The heat transfer rate rises significantly with diminishing value of Soret number.

Comprehending adsorption of methylethylketone and toluene and microwave regeneration effectiveness for beaded activated carbon derived from recycled waste bamboo tar

ABSTRACT Beaded activated carbons (BACs) were derived from waste bamboo tar through carbonization (500°C for 2 hr) followed by physical activation using carbon dioxide (800–900°C for 2–4 hr). The adsorbent was examined for their physical and chemical properties, adsorption capacities toward methylethylketone (MEK) and toluene, and regenerabilities under microwave heating. It was found that the maximum total surface area reached for bamboo-tar-derived BAC after physical activation was 1364 m2 g−1, and more than 95% of the area was attributed to the microporous structures. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models were applied to the adsorption isotherm fitting, and the minimum R2 for each model was 0.986, 0.915, and 0.943, respectively. The isosteric heats of adsorption calculated based on D-R parameters for methylethylketone and toluene were 44.04 to 51.50 and 45.88 to 73.27 KJ mol−1, respectively. They were slightly over the range of physisorption and increased with adsorbate loading, which might be related to the micropore filling mechanism. Microwave regeneration under 600 W of power output removed most of the adsorbate (>93.03%) within 8 min. The results of this study are intended to benefit future study on waste-derived adsorbent in environmental applications. Implications Recycling waste bamboo tar for the novel adsorbent preparation is shown feasible in this study. Beaded activated carbon (BAC) synthesized from this waste bamboo tar possessed a high specific surface area, which aided in the capturing of volatile organic compounds (VOCs). Three adsorption isotherms, Langmuir, Freundlich, Dubinin-Radushkevich (D-R) models can be applied in interpreting the experimental adsorption data, providing information on adsorption heat and possible adsorption mechanism. A potential microwave regeneration method for BAC is tested, showing high desorption efficiencies with minimum heel formation. These findings can provide a new pathway for waste bamboo tar management and VOC abatement using adsorbents.

Atmospheric stability and collapse on tidally locked rocky planets

Context.Over large timescales, a terrestrial planet may be driven towards spin-orbit synchronous rotation by tidal forces. In this particular configuration, the planet exhibits permanent dayside and nightside, which may induce strong day-night temperature gradients. The nightside temperature depends on the efficiency of the day-night heat redistribution and determines the stability of the atmosphere against collapse.Aims.To better constrain the atmospheric stability, climate, and surface conditions of rocky planets located in the habitable zone of their host star, it is thus crucial to understand the complex mechanism of heat redistribution.Methods.Building on early works and assuming dry thermodynamics, we developed a hierarchy of analytic models taking into account the coupling between radiative transfer, dayside convection, and large-scale atmospheric circulation in the case of slowly rotating planets. There are two types of these models: a zero-dimensional two-layer approach and a two-column radiative-convective-subsiding-upwelling model. They yield analytical solutions and scaling laws characterising the dependence of the collapse pressure on physical features, which are compared to the results obtained by early works using 3D global climate models (GCMs).Results.The analytical theory captures (i) the dependence of temperatures on atmospheric opacities and scattering in the shortwave and in the longwave, (ii) the behaviour of the collapse pressure observed in GCM simulations at low stellar fluxes that are due to the non-linear dependence of the atmospheric opacity on the longwave optical depth at the planet’s surface, (iii) the increase of stability generated by dayside sensible heating, and (iv) the decrease of stability induced by the increase of the planet size.

Existence of dual solutions for wedge flow of magneto-Williamson nanofluid: A revised model

This communication intends to elaborate the mechanism of heat and mass transport of an unsteady stagnation point flow of Williamson nanofluid past a wedge subject to magnetohydrodynamics (MHD), thermophoresis and Brownian motion effects. In this study, the flow equations with magnetic parameter is incorporated especially in the Williamson fluid flow case. The appropriate transformations are used to convert the governing partial differential equations into ordinary differential equation and then solved numerically by using shooting scheme with fourth order Runge-Kutta-Fehlberg method in MATLAB software. The influence of wedge angle parameter, the local Weissenberg number, unsteadiness parameter, magnetic parameter, suction parameter, the Biot number, thermophoresis and Brownian motion parameter on dimensionless velocity, temperature and nanoparticle concentration fields as well as skin friction coefficient and local Nusselt number are rigorously demonstrated and discussed. This study also elaborates the critical range of velocity ratio parameter and suction parameter, for the existence of dual branch of solutions. The obtained results show that Biot number enhances the fluid temperature and concentration. Further, the suction parameter is an increasing function of rate of heat transfer. Furthermore, the analysis suggests that the upper branch solution is stable and physically possible.