Heat Transport Processes Research Articles

Numerical analysis of nonlinear time‐fractional fluid models for simulating heat transport processes in porous medium

AbstractHybrid nanomaterials offer potential scope for increasing numerous novel applications when engineered to deliver availably functional properties. In the current assessment, a novel fractional constitutive relationship for buoyance‐driven flow and heat transfer has been developed in order to control the flow and heat transfer behavior. The fluid flow is produced by a permeable moving surface and is exposed to thermal radiation along with an applied magnetic field. This study employed the SiO2/MoS2 hybrid nanoparticles with different mass ratios in water as the base fluid. Moreover, the Darcy expression characterizes the porous spaces with variable porosity and permeability. Governing fractional PDEs are nonlinear and solved numerically with finite‐difference discretization and the L1‐ algorithm. The results show that heat transfer rate enhanced 8% by enhancing the thermal fractional parameter. It is also found that the combination of two nanoparticles in water significantly contributes to heat transfer compared to the presence of a single particle. Further, thermal radiation significantly contributes to heat transfer in fluid flow. Not surprisingly, hybrid particles have excellent performance at high loads and diverse velocity cases.

The effects of various flame retardants on the combustion of polypropylene: Combining optical diagnostics and pyrolysis fragment analysis

The assessment of the efficacy and mode of action of flame retardants in polymers requires a thorough knowledge of the coupling of the presence of chemical inhibitors with the underlying heat and mass transport processes. In this experimental work, we combine a thermal decomposition analysis with optical combustion diagnostics in different test environments to gain a comprehensive understanding of the relevant sub-processes and demonstrate how this approach provides future opportunities for the research regarding the mode of action of flame retardants. Four different composites of polypropylene (PP) and 10 wt% of selected flame retardants as well as neat PP are prepared. Flame retardants include pentaerythritol spirobis(methylphosphonate) (PSMP), zinc diethylphosphinate (DEPZn), aluminum hydroxide (i.e. aluminum trihydrate, ATH) and ammonium polyphosphate (APP). The released substances in the gas phase are investigated by using thermogravimetric analysis coupled to Fourier-transform infrared spectroscopy (TGA-FTIR), and the burning behavior regarding carbon monoxide concentration and heat release rate (HRR) is studied in cone calorimeter experiments. The ignition and combustion of flame retarded micrometer-sized particles of PP are experimentally investigated in a laminar flat flame burner by means of simultaneous scanning planar laser-induced fluorescence of OH radicals (OH-PLIF) and diffuse back-illumination (DBI) at a repetition rate of 10 kHz. Particles with gas-phase activity show a decreased normalized OH signal intensity during combustion. A dependency of the dimensionless flame radius on the particle size is found which can be linked to the faster heating and pyrolysis of smaller particles compared to large particles and agglomerations. Eventually, the interaction with an external premixed flame and the subsequent extinction of self-sustaining flames of polymer sticks is investigated using OH-PLIF in an adapted horizontal burning test suited for the application of optical diagnostics. This approach allows to link the findings of investigations encompassing multiple scales, resulting in a thorough understanding of both polymer chemistry and combustion dynamics in flame retarded polymers.

Radiative flow of rheological material considering heat generation by stretchable cylinder

Background and objectiveMagnetohydrodynamic effect has various industrial applications in crystal growth, manufacturing, nuclear reactor cooling, mineral casting, polymer extrusion, cable coating, metallurgy, liquid--metal cooling etc. In view of these application here we addressed the magnetohydrodynamic radiative Reiner-Rivlin fluid flow by stretching cylinder. Consideration of heat generation and magnetic field scrutinizes the heat transport process. Modeling for binary chemical reaction is presented. MethodologyGoverning nonlinear ordinary systems through suitable transformation are obtained. The set of non-dimensional systems are computed for local similar solution by ND-solve method. ConclusionsTemperature, fluid flow and concentration have been analyzed. Computations for coefficient of skin friction, temperature gradient and solutal transport rate are organized. Magnetic field outcome for velocity and temperature is not similar. Enhancement in fluid flow versus curvature variable is found. Reduction occurs in fluid friction and velocity for Reiner-Rivlin liquid variable. Thermal field versus Prandtl number is decayed. Outcomes for magnetic field and radiation on temperature are alike. An augmentation of concentration is seen for curvature variable. Concentration versus reaction variable is decreased. Nusselt number for radiation and magnetic field is not similar. Large approximation of reaction variable boosts up mass transport rate.

Proton Exchange Membrane Fuel Cell as an Alternative to the Internal Combustion Engine for Emission Reduction: A Review on the Effect of Gas Flow Channel Structures

Proton exchange membrane fuel cells are a new energy technology with great potential due to advantages such as high efficiency and no pollution. The structure of the gas flow channels has a profound impact on the overall performance of the fuel cell. Different flow channel geometries have their own advantages and disadvantages, and a good understanding of the influence of these structures on performance can provide a reference for the design and improvement of flow channel geometries in various application contexts. Numerical models can be used as a reasonable and reliable tool to evaluate the influence of operating and structural parameters on cell performance and service time by simulating the transport processes of substances and heat as well as electrochemical reactions inside the fuel cell and can be used for the optimisation of cell design. This paper reviews the recent models of proton exchange membrane fuel cells, summarises and analyses the effect of gas flow channels on fuel cells, and organises and concludes efficient design of flow channel structures to enhance PEMFC performance in terms of the cross-section shape, length, width, number of flow channels, and baffle position.

Effects of pumping power on oxygen transport and performance of proton exchange membrane fuel cell

BackgroundPumping power (PP), determined by the resistance of the gaseous reactants flowing in flow fields, significantly affects the net output power density of proton exchange membrane fuel cells (PEMFCs), especially on the air-cooled PEMFCs. No previous studies on the oxygen transport performance of PEMFCs operated at high PPs are available. Novel flow channels are needed to serve the PEMFC applications with intermediate PP. MethodsThe fluid flow, heat, and mass transport processes in a steady-state PEMFC were simulated using a three-dimensional, two-phase, and non-isothermal model, with the oxygen concentration distributions, its interfacial fluxes, and the so-yielded pressure difference and electric current density being reported. Three flow fields were studied: parallel, serpentine, and a novel bamboo shape. Significant findingsThere is a threshold PP above which the current density reaches a plateau, counterbalanced by the increasing resistance built up by water accumulation at the cathode. Both the threshold PP and the maximum current density of the serpentine flow field (0.8 W, 1.83 A cm−2) are higher than those of the parallel flow field (0.1 W, 1.71 A cm−2) since the governing oxygen transport for the former depends on the convection and for the latter, the diffusion. A bamboo shape flow field has been proposed to compensate for the drawback of high PP needed for the serpentine flow field. The threshold PP is reduced to 0.5 W, with a maximum current density of 1.78 A·cm−2. The parallel flow field can be applied at a high mass flow rate and low PP scenario; at a low mass flow rate and high PP case, the serpentine flow field can be applied; in between, the bamboo flow field can be applied to be an appropriate alternative.

A comprehensive pyrolysis model for lignocellulosic biomass particles with a special emphasis on the anisotropic characteristics

The porous and fibrous structural tissue of lignocellulosic biomass serves as a transport channel for water and nutrients along the growth direction, indicating a highly anisotropic nature of biomass. The anisotropies of the thermal and structural properties of biomass have substantial influences on particle-scale reactions, transport processes, and morphological evolution during thermal conversions. An in-depth investigation of the anisotropic characteristics of these physicochemical phenomena in pyrolysis benefits in the understanding of biomass gasification and combustion processes. In this study, a comprehensive 2D axisymmetric mathematical model is developed to quantitatively analyze the pyrolysis behaviors of a cylindrical wood particle with or without anisotropy. Correlative unsteady energy and mass conservation equations are combined with a multistep kinetic model of biomass devolatilization. To improve the numerical descriptions of volatiles flowing in a porous biomass matrix, the constitutive equations of the Brinkman equation and dusty gas model are adopted. Moreover, a binary differential equation is used to calculate the simultaneous changes in the pore structure and shrinkage of the wood particles. When considering anisotropy, validations of the model against literature data demonstrate that it can reliably predict the intraparticle temperature profiles, weight loss, and particle shrinking degree of lignocellulosic biomass. Using this model, the coupling effects of multi-physical fields and reactions inside pyrolyzing wood particles are explored. It is revealed that the anisotropic characteristics of biomass influence not only the orientations of intraparticle heat and mass transport processes but also their mechanisms, resulting in varying degrees of secondary reactions and particle shrinkage.

A compact jet array impingement cooling system driven by integrated piezoelectric micropump

Thermal management has become a bottleneck for high-power electronics due to high heat flux. Liquid cooling has been developed as an effective way to dissipate the heat of electronic devices. However, the existing liquid cooling systems are mostly too bulky to be applied in the miniaturized devices with very limited installation space. In this work, by integrating jet impingement cooling with piezoelectric micropump, we proposed a compact liquid cooling system that simultaneously enables high heat removal capability and tiny volume. The functions of jet array impingement cooling and coolant pumping are realized in a single component with an external dimension of 40 mm × 40 mm × 10 mm. The thermal performance of the system was investigated by experiments. The results show that the convective heat transfer coefficient achieves 20572 W·m−2·K−1 at a heat flux of 91.5 W/cm2. And the electric power consumption of the system is only 0.023 W under a heat load of 200 W (50 W/cm2). Simulations, which agree well with experiments, were further employed to study the transient heat transport process. This novel jet impingement cooling system driven by integrated piezoelectric micropump is compact and efficient, which provides a promising solution for the thermal management of high-power, miniaturized electronic devices.

How temperatures derived from fluid flow and heat transport models impact predictions of deep geothermal potentials: the “heat in place” method applied to Hesse (Germany)

One key aspect in the energy transition is to use the deep geothermal energy stored in sedimentary basins as well as in igneous and metamorphic basement rocks. To estimate the variability of deep geothermal potentials across different geological domains as encountered in the Federal State of Hesse (Germany), it is necessary to understand the driving processes of fluid flow and heat transport affecting subsurface temperature variations. In this study, we quantify the stored energy in a set of geological units in the subsurface of Hesse with the method of “heat in place” (HIP, sensu Muffler and Cataldi in Geothermics 7:53–89, 1978)—HIP is one proxy for the geothermal potential of these units controlled by their temperature configuration as derived from a series of coupled 3D thermo-hydraulic numerical models. We show how conductive, advective and convective heat transport mechanisms influence the thermal field and thereby the HIP calculations. The heterogeneous geology of the subsurface of Hesse ranges from locally outcropping Paleozoic basement rocks to up to 3.8 km thick Cenozoic, porous sedimentary deposits in the tectonically active northern Upper Rhine Graben. The HIP was quantified for five sedimentary layers (Cenozoic, Muschelkalk, Buntsandstein, Zechstein, Rotliegend) as well as for the underlying basement. We present a set of maps allowing to identify geothermally prospective subregions of Hesse based on the laterally varying thermal energy stored within the units. HIP is predicted to be highest in the area of the northern Upper Rhine Graben in the Cenozoic unit with up to 700 GJ text {m}^{-2} and in the Rotliegend with up to 617 GJ text {m}^{-2}. The calculations account for the variable thicknesses and temperatures of the layers, density and heat capacity of the solid and fluid parts of the rocks as well as porosity.

Improvement of natural convection simulation based on energy conservation dissipative particle dynamics

Energy conservation dissipative particle dynamics (eDPD) is a mesoscale numerical simulation method of studying the heat transport process. In previous studies, when the Boussinesq assumption was introduced into the eDPD system to study the natural convection, the system was generally considered to be incompressible, and the effect of the thermal expansion of the eDPD system itself on the simulation results was often neglected, which would cause errors in the simulation. In the present study, the thermal expansion characteristic of the eDPD system is first investigated, and the thermal expansion coefficient <i>β</i> of the eDPD system is obtained by eDPD simulation. Then, based on the thermal expansion characteristic of the eDPD system itself, the natural convection is simulated with different values of Rayleigh number <i>Ra</i> and different geometries, specifically, square cavity, concentric rings, and eccentric rings, and reasonable temperature and velocity fields are obtained, and they are in agreement with the simulated results by the finite volume method (FVM). The error between the eDPD simulation, in which the natural convection is driven by thermal expansion of the eDPD system itself, and FVM simulated result is considerably smaller than the errors observed in previous studies where Boussinesq assumption was directly adopted to simulate natural convection phenomena while neglecting the thermal expansion effect of eDPD system. It is shown that the effect of the eDPD system’s own thermal expansion characteristic needs to be considered when introducing the Boussinesq assumption in the eDPD system, and further, the calculation of the <i>Ra</i> number is modified in this paper.

Quantifying transport and electrocatalytic reaction processes in a gastight rotating cylinder electrode reactor via integration of Computational Fluid Dynamics modeling and experiments

Understanding the complexity of the multiple processes of mass, momentum, charge, and heat transport, and how these affect reaction kinetics at the electrode/electrolyte interface is one of the major challenges in the field of energy and catalysis. The rapid and rational scale-up of electrocatalytic systems to industrial scales require a detailed understanding of nonlinear transport-reaction processes, accessible only through the building of multi-physics models that capture with high fidelity the complexity of real-world devices. The gastight rotating cylinder electrode (RCE) reactor is a promising lab-scale tool that can decouple transport from intrinsic kinetics to generate data for first-principle models useful in the design of industrial, electrochemical reactors. Computational Fluid Dynamics (CFD) studies have previously been used to investigate the bulk flow in RCE reactors for simple corrosion and electroplating processes. However, the quantification of changes in local concentration within the viscous layer where catalysis takes place requires capturing the correct flow conditions inside the hydrodynamic boundary layer near the surface of the electrode. This requires simulations with spatial resolution in the nm and μm scale and temporal resolutions between ms and s scales that are similar to the timescales for reactions on the electrode surface. In this study, experimental electrocatalysis is combined with CFD modeling to elucidate and parameterize the hydrodynamics in a gastight RCE reactor. CFD simulations of the electrochemical ferricyanide reduction reaction under mass transport limited conditions are used to evaluate the validity of the CFD model parameters by comparing calculated dimensionless mass transport descriptors to dimensionless correlations obtained experimentally. Justifications for assumptions and details of the simulation methods used in this study are presented to provide a detailed understanding of the effect that each model parameter has on the ability to accurately simulate electrocatalysis in RCE systems. The simulation methodology reported here is a first step towards the development of multi-scale models for the study of transport dependent electrocatalytic processes, such as the electrochemical transformation of CO2 to fuels and chemicals.

Simulation of Heat Flow in a Synthetic Watershed: The Role of the Unsaturated Zone

Future climate forecasts suggest atmospheric warming, with expected effects on aquatic systems (e.g., cold-water fisheries). Here we apply a recently published and computationally efficient approach for simulating unsaturated/saturated heat transport with coupled flow (MODFLOW) and transport (MT3D-USGS) models via a synthetic three-dimensional (3D) representation of a temperate watershed. Key aspects needed for realistic representation at the watershed-scale include climate drivers, a layering scheme, consideration of surface-water groundwater interactions, and evaluation of transport parameters influencing heat flux. The unsaturated zone (UZ), which is typically neglected in heat transport simulations, is a primary focus of the analysis. Results from three model versions are compared—one that neglects UZ heat-transport processes and two that simulate heat transport through a (1) moderately-thick UZ and (2) a UZ of approximately double thickness. The watershed heat transport is evaluated in terms of temperature patterns and trends in the UZ, at the water table, below the water table (in the groundwater system), and along a stream network. Major findings are: (1) Climate forcing is the product of infiltration temperatures and infiltration rates; they combine into a single heat inflow forcing function. (2) The UZ acts as a low-pass filter on heat pulses migrating downward, markedly dampening the warming recharge signal. (3) The effect of warming on the watershed is also buffered by the mixing of temperatures at discharge points where shallow and deep flow converge. (4) The lateral extent of the riparian zone, defined as where the water table is near land surface (<1 m), plays an important role in determining the short-term dynamics of the stream baseflow response to heat forcing. Runoff generated from riparian areas is particularly important in periods when rejected infiltration during warm and wet periods generates extra runoff from low-lying areas to surface water.

Study of the effect of magnetic field characteristics on Rayleigh-Taylor instability with density gradient layers

Inertial confinement fusion (ICF) is a possible path of fusion technology for fusion ignition, but during the implosion of a magnetized plasma target by compression, the magnetic Rayleigh-Taylor (R-T) instability similar to that at the interface of the denser and less dense phases can arise when the plasma is subjected to gravitational and magnetic forces, which in turn affect the confinement characteristic and the process of fusion burn. In this study, the R-T instability of two phases in the presence/ absence of a magnetic field in a two-dimensional rectangular duct is simulated based on the MHD model adopted in ANSYS FLUENT. The simulation results show that the R-T instability is substantially weakened for the case with an Atwood number of 0.29 where a constant (DC) magnetic field is imposed in the opposite direction to the gravitational acceleration, meanwhile, a strong countercurrent flow, which occurs near the side walls, enhances the heat and mass transport process, which is related to the M-shape velocity profile formed in the flow channel. Besides, when a DC magnetic field perpendicular to the direction of the gravitational acceleration is introduced, the R-T instability vanishes from the initial moment to the end. When a sinusoidal wave form of varying (AC) magnetic field is introduced, the R-T instability is substantially facilitated. The evolutions of the interface and pressure field distribution are significantly correlated with the change in intensity and direction of the AC magnetic field. After about one cycle of the magnetic field's variation, the density gradient layers in the vertical direction are entirely converted to a density stratification in the horizontal direction with the denser phase occupying the region near the sidewalls of the duct, and ever since then, the R-T instability disappears completely. These findings can provide supports for the design of nuclear fusion devices and magnetic fields.

The activation energy in the radiative flow of fourth-grade nanomaterial with convective conditions

The fourth-grade nanomaterial over a stretched permeable surface is intended in this article. The heat transport process is analyzed by thermal radiation and viscous dissipation. Convective heat-mass conditions at the surface are imposed. The Boungiorno model is utilized for nanofluid description. Furthermore, activation energy is accounted for. Flow expressions (PDEs) are modeled by the implementation of boundary layer approximations. These PDEs are expressed to ODEs by means of appropriate transformations. A technique, namely, OHAM is executed for solution development. Quantities of interest (skin fraction, velocity, Nusselt number, temperature, concentration, and Sherwood number) are evaluated for the influential variables. An increasing trend for velocity () is observed for increasing fourth-grade fluid parameters in the case of negative injection parameters, while an inverse behavior is noted for positive values of injection parameters. Eckert number and radiation increase heat transfer rate, while a decreasing trend is observed against higher Brownian and thermophoresis parameters.

A novel passive polymer-sorbent thermal battery for low-temperature energy applications: A numerical feasibility study

Sorption thermal energy storage (STES) systems offer great potential for meeting the growing energy needs and increasing the use of renewable energy resources. However, the complexity and large-scale of current STES technologies lead to relatively low-efficiency systems, severely limiting their widespread implementation. To address this challenge, this study presents a novel and compact smart-polymer sorbent (SPS) thermal battery with passive material-enabled mechanisms for controlled low-temperature thermal energy storage applications. A numerical model is established to investigate the coupled heat and mass transport processes underlying the working behavior of the SPS battery. It is also used to reveal the interdependence of the two processes and the limiting factors for the battery's thermal performance. The heating performance of several SPS battery designs was studied as an example, focusing on their application for cold environment thermal protection. Moreover, the influence of various design parameters was examined, including sorbent selection, void fraction, relative humidity, gate thickness, and gate-to-sorbent area, along with their implications to the coupled mass-heat transport processes. The results revealed that diffusion-based mass transport is the limiting process affecting the SPS battery thermal performance. The numerical simulation results also indicated that the sorbent selection should consider their low recharge temperature (40 °C–100 °C) and less pronounced temperature-dependent adsorption behavior to maximize the heating performance of the SPS battery. In addition, the SPS battery heating efficiency could be enhanced by increasing the sorbent void fraction to 0.35, relative humidity (RH) to 40 %, and gate-to-sorbent area to 60 % while decreasing the gate thickness to 0.1 μm effectively, which facilitate the diffusion-controlled mass transport process. Lastly, a single layer SPS battery is beneficial for thermal regulation at low temperatures; however, using distributed battery designs had a significant thermal performance enhancement benefit of 90 % compared to the single layer design. Hence, our study reveals the complex coupling effects of the heat and mass transport processes within the proposed SPS battery and provides insights and guidance (e.g., materials selections and SPS design) for engineering emergent small-scale passive STES applications.

Simulating the heat transfer behaviour in a fluidized bed by a combined thermal model in the CFD-DEM coupling

The exchange of mass and heat transport in fluidized beds is a complicated and extensive topic, making it a rich field for scientific and industrial applications. This numerical research implements the CFD-DEM coupling to investigate the transport of heat energy in a fluidized bed. A numerical test compares the numerical and analytical results for a single particle in a column. Two cases of heating and cooling are compared. The numerical results present well adequacy with the analytical results. The development of fluidized bed units, within fluidized bed units is vital to improving the designs of these units. Therefore, three methods of column heating, including base heating, walls heating, and as well as walls and base heating, have been proposed in the simulations. The results reveal that the fluid inlet velocity increase during the fluidized beds' heating process is invalid. Thus, the fluid's proper inlet velocity and imposed temperature are crucial in the heating process for the fluidized beds since the particles need to provide time for the heat transport process.

Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC.

Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a microstructure model of CL was first reconstructed using images acquired by Nano-computed tomography (Nano-CT) of a real sample of CL. Then, the multiphysics dynamic distribution (MPDD) simulation, which is inherently a multiscale approach made of a combination of pore-scale and homogeneous models, was conducted on the reconstructed microstructure model to compute the corresponded heat and mass transport, electrochemical reactions, and water phase-change processes. Considering a computational domain with the size of 4 um and cube shape, this model consisting of mass and heat transport as well as electrochemical reactions reached a stable solution within 3 s as the convergence time. In the presence of sufficient oxygen, proton conduction was identified as the dominant factor determining the strength of the electrochemical reaction. Additionally, it was concluded that current density, temperature, and the distribution of water all exhibit similar distribution trends, which decrease from the interface between CL and the proton-exchange membrane to the interface between CL and the gas-diffusion layer. The present study not only provides an in-depth understanding of the mass and heat transport and electrochemical reaction in the CL microstructure, but it also guides the optimal design and fabrication of CL components and structures, such as improving the local structure to reduce the number of dead pores and large agglomerates, etc.

Effect of the spacing on forced convection heat transfer for flow around a row of heated square cylinders

This work reports impact of spacing on forced convection heat transmission for flow around the row of heated square cylinders for s/d = 1.0 to 8.0 at Re = 80, Ri = 0, and Pr = 0.71. The thermal lattice Boltzmann method (TLBM) is used to perform numerical analysis. The focus is to explore heat transfer physics and to comprehend influence of spacing on transitions in heat transfer through signals of the Nusselt number. Synchronous, quasi-periodic, and chaotic heat transfer regimes have been documented here as a function of the spacing between cylinders. The contribution of modulation frequency to the cylinder Nusselt number signals and their power spectra are used to assess these heat transfer regimes. The distinguishing feature of a synchronous heat transfer regime (s/d = 6.0 to 8.0) is development of independent heat wakes behind cylinders with a single frequency in Nusselt number signal. In quasi-periodic heat transfer regimes, thermal blobs coalesce directly downstream of the cylinder at a short distance. In a chaotic heat transfer regime, due to small spacing between cylinders, thermal blobs merge immediately behind cylinders leading to chaotic heat transfer between the cylinders just like a jet. It is noticed that average cylinder Nusselt number recognized by all cylinders grows as spacing reduces. It is important to note that at 6.0 ≤ s/d ≤ 8.0 the transfer of heat is dominated by the presence of a single frequency in the Nusselt number signal while at 3.0 ≤ s/d ≤ 5.0 another frequency is called secondary frequency appears in the signal which dominates at low s/d = 1.0. The most important discovery from current numerical research is that heat transfer method is unsteady and periodic in nature. The unsteadiness in the heat transport process can be explained through transient variation of Nusselt number.

The inhibition of warm advection on the southward expansion of sea ice during early winter in the Bering Sea

Recent observations demonstrate that the Bering Sea exhibits a substantial positive trend of sea ice area increment (ΔSIA, difference in SIA between the current and preceding months) in January contrasted to the considerable negative sea ice area (SIA) trend from 1979 to 2020, and the ΔSIA is unrelated to the local wind field anomaly. To better understand the January ΔSIA variability and its physical characteristics, we explore two distinct empirical orthogonal function (EOF) modes of sea ice concentration increments. EOF1 features a reduction in sea ice concentration (SIC) in the south of St. Lawrence Island. EOF2 is characterized by the rise of SIC surrounding St. Lawrence Island. EOF1 is related to the well-known physical process of December strong poleward heat transport in mixed layer depth. During the southward expansion of sea ice, the multiyear variation of the December SST tendency mostly relies on warm advection in the Bering Sea shelf rather than net air-sea heat flux, and the abnormal northeast wind in December no longer plays the role of a dynamic process dominating the ice area expansion, but generates a stronger poleward heat transport in the Bering Sea shelf to inhibit the southward development of sea ice in the later stage. The two physical processes together result in oceanic poleward heat transport regulating the Bering Sea SIA in competition with atmospheric forcing in early winter. Since PC1 (principal component (PC) time series for EOF1) has a high correlation of -0.76 with the maximum SIA in the Bering Sea, it can be used as the prediction index of the Bering Sea maximum SIA.

Activation Energy Performance through Magnetized Hybrid Fe3O4–PP Nanofluids Flow with Impact of the Cluster Interfacial Nanolayer

The current work investigated the mass and heat transfer of the MHD hybrid nanofluid flow subject to the impact of activation energy and cluster interfacial nanolayer. The heat transport processes related to the interfacial nanolayer between nanoparticles and base fluids enhanced the base fluid’s thermal conductivity. The tiny particles of Fe3O4 and PPy were considered due to the extraordinary thermal conductivity which is of remarkable significance in nanotechnology, electronic devices, and modern shaped heat exchangers. Using the similarity approach, the governing higher-order nonlinear coupled partial differential equation was reduced to a system of ordinary differential equations (ODEs). Fe3O4–PPy hybrid nanoparticles have a considerable influence on thermal performance, and when compared to non-interfacial nanolayer thermal conductivity, the interfacial nanolayer thermal conductivity model produced substantial findings. The increase in nanolayer thickness from level 1 to level 5 had a significant influence on thermal performance improvement. Further, the heat and mass transfer rate was enhanced with higher input values of interfacial nanolayer thickness.

Human body radiation area factors for diverse adult population.

Radiation accounts for a significant fraction of the human body and environment heat exchange and strongly impacts thermal comfort and safety. The direct radiative exchange between an individual and a source or sink can be quantified using the effective (feff) and projected radiation area factors (fp). However, these factors have not been quantified for half of the population of the USA with an above-average body mass index (BMI). Here, we address this gap by developing thirty male and thirty female computational manikin models that cover the 1 to 99 percentile variation in height and BMI of adults in the USA. The radiative simulations reveal that the feff and the fp angular distributions are nearly independent of gender, height, and BMI. Appreciable relative differences from the average models only emerge for manikins with BMI above 80th percentile. However, these differences only occur at low zenith angles and, in absolute terms, are small as compared to variations induced by, for example, the zenith angle increase. We also use the manikin set to evaluate whether the body shape impacts the quality of human representation with several levels of geometrical simplification. We find that the "box/peg" body representation, which is based on the hemispherical fp average, is independent of the body shape. In turn, the fp distributions averaged over the azimuth angle range, representing the rotationally symmetric humans, are only impacted to the same degree as for the anatomical manikins. We also show that the anatomical manikins can be closely approximated by the multi-cylinder and sphere representation, at least from a radiation perspective. The developed anatomical manikin set is freely available and can be used to compute how body shape impacts a variety of external heat transport processes.