Heat Transport Processes Research Articles

Numerical approach for the modified heat transport process under improved Darcian and nonlinear mixed convective effects

Analysis regarding heat transport subjected to non-Darcian media has increased in science and technological utilization. Typical applications comprise grain storage, nuclear waste discarding, production of crude oil, pollution in groundwater, porous insulation, and several others. This motivates us to demonstrate the heat transport phenomenon in the viscous fluid's flow deformed by a linearly stretchable surface submerged in Darcy-Forchheimer porous medium. Properties of heat transfer are elaborated with nonlinear mixed convection and Cattaneo-Christov heat model. Slip phenomenon is implemented at the wall surface. The governing equations are achieved in dimensionless form through appropriate transformations. Numerical solutions are constructed through shooting scheme along with 4–5 order Runge-Kutta Fehlberg technique. Graphical behaviors of velocity field and liquid temperature are constructed through various physical parameters. Results witnessed that decrement occurs in velocity field for dominant behavior of velocity slip parameter while it enhances for dominant nonlinear mixed convection parameter.

Heat flow characteristics and thermal resistance model for soil-rock mixtures during freezing-thawing processes: Damping properties

As a special heterogeneous geological material, soil-rock mixtures are widely distributed in nature and used in civil engineering. Heat flow is one of the most significant factors affecting the development of water balance and redistribution, ground temperature evolution, and heat transport processes in cold regions. This study explores the heat flow characteristics and generalized thermal resistance model for soil-rock mixtures during freezing-thawing processes. A series of freezing-thawing experiments for soil-rock mixtures with different rock contents (i.e., 10%, 25%, and 40%) were conducted. The effects of rock content and water–ice phase transition on heat flux during the freezing-thawing processes were analyzed, and the damping properties of heat flow for soil-rock mixtures during freeze–thaw cycles were found and illustrated. Subsequently, a generalized thermal resistance model for soil-rock mixtures was proposed and discussed. The results show that the freezing-thawing processes and rock content significantly influence the heat flux and soil temperature of the soil-rock mixtures. Regardless of rock content, the sums of heat flux in freezing and thawing stages all firstly decreased, and then gradually tends to be stable with freeze–thaw cycles. Besides, the reduction of volumetric unfrozen water content increases with the freeze–thaw cycles, and the amplitude of unfrozen water reduction for sample with high rock content is larger than that with low rock content. Additionally, owing to the effect of the latent heat released by water/ice phase transition and thermal sensitive property of rock, the variation of heat flow for soil-rock mixtures presents damping property in the stages without completely freezing, and the variation of heat flow exhibits reversed damping property in the post-freezing stages due to the denser structure and ice crystal growth. Furthermore, based on the thermal resistance in series, characteristics of water–ice phase transition, and thermal sensitive property of rocks, a new generalized thermal resistance model of soil-rock mixtures during freezing-thawing processes is proposed.

Effect of noble gases on the transport and thermodynamic characteristics of microchannel reforming reactors for hydrogen production

Noble gases can offer the advantages of high selectivity in steam reforming processes with especially great potential for hydrogen production, but the underlying cause for process intensification has not yet been identified. Calculations are performed to investigate the effect of helium or argon gases on the transport and thermodynamic characteristics of a microchannel reactor for hydrogen production. Dimensionless Nusselt and Sherwood number analyses are carried out and the thermodynamic properties of the reaction mixture are determined in order to effectively control the heat and mass transport processes with increasing precision. The heat and reaction phenomena in the reactor system are studied in order to understand the underlying cause for the improvements in transport performance. Enthalpy analysis is performed and the evolution of energy in the chemical processes is discussed based upon reaction heat flux. The results indicate that the noble gas offers the advantages of process intensification due to enhanced heat and mass transport. Additionally, the noble gas can be utilized to enhance conversion behavior while maintaining the reaction rate. Furthermore, the transport properties can be effectively controlled and manipulated, thereby serving as a means for improving the effectiveness of convection at the catalyst surface. Additional advantages include the ability to avoid the problem inherent in thermal management, thereby providing nearly isothermal operation and thus suppressing undesirable side reactions. Finally, the reforming process is characterized for purposes of demonstration or explanation by thermodynamic parameters, including temperature, specific heat, specific enthalpy, sensible enthalpy, and mean molecular weight.

Dissipative Lorentz force influence on mass flow over a micro‐cantilever sensor sheet under magnetic Ohmic heating

AbstractThe novelty and main aim of the present numerical analysis is to explore the magneto‐thermo‐fluid characteristic features of incompressible, time‐dependent electrically conducting second‐grade fluid flow about a micro‐cantilever sensor sheet suspended in a squeezed regime between two parallel plates under the influence of Lorentz force field and viscous dissipation effects. Pertaining to this physical situation, the primitive forms of produced coupled nonlinear partial differential equations are rendered to non‐dimensional ordinary differential equations through appropriate scaling transformations. The resultant coupled nonlinear boundary value physical problem is solved by deploying a robust BVP4C Matlab function. The key features of the emerged different fluid flow parameters are documented in terms of extensive graphical visualization and tabular discussion. The current numerical investigation showed that, the increasing second‐grade fluid parameter significantly decreases the flow field and enhances the thermal and mass diffusion fields. Magnifying permeable velocity number decreases the velocity and increases the heat and concentration transport process. The thermal distribution over a sensor region is boosted with increasing Eckert number through viscous dissipation and magnetic Ohmic heating. Further, the elevating squeezing number decreases the skin friction and enhancing second‐grade fluid number boosted the skin‐friction coefficient. In addition to this, the increasing Schmidt and squeezing parameters decreases the local Sherwood number. Finally, a reasonable agreement between the present numerical solutions with the former results is presented.

Computational assessment of MHD Carreau tri-hybrid nano-liquid flow along an elongating surface with entropy generation : A comparative study

This research looks at the incompressible, viscous, steady-state laminar stagnation-point-flow of a Carreau ternary-hybrid nano-liquid towards a convectively heated expanding surface, taking into account first-order slippage and Ohmic dissipation. Viscous dissipation and the effects of Lorentz forces are also considered. It is discussed how thermal radiation and heat absorption/generation contribute to the heat transport process. Minimizing entropy during the transport of a Carreau ternary hybrid nano-liquid has also been studied. In addition, convective circumstances are used conceptually in the numerical solution of the current model. tiny-particles of silver (Ag), molybdenum disulfide (MoS2), and multi-wall carbon nanotubes (MWCNT) are analyzed in this work’s flow study. As a base fluid, carboxymethyl cellulose (CMC-water) is used. With the use of appropriate similarity trans-formations, the standard model equations are transformed into dimensionless form. Finding solutions for momentum and heat fields using the Runge–Kutta-Fehlberg technique and a shooting strategy. The figures depict a wide range of characteristics, including fluid flow velocity, temperature, skin friction, the Nusselt number, entropy minimization, and the Bejan number. Key results from the present model include the fact that the velocity curve flattens down as Weissenberg number increases.

Convective Versus Conductive Heat Flow in The Central Alberta Part Of The Western Canada Sedimentary Basin

Alberta, Canada, T6H 5X2. A detailed study of the hydrogeological and geothermal regimes in the Phanerozoic sequence of the Western Canada Sedimentary Basin was carried out for the Swan Hills and Cold Lake areas in central Alberta. The study was based on the examination, processing and interpretation of information from 6276 wells distributed over a total area of 39,500 km². The information processed refers to stratigraphic picks, chemistry of formation waters, drill stem tests and bottom hole temperatures. As a result, every stratigraphic unit is defined in terms of geometry and lithology, and characterized by appropriate hydraulic and thermal parameters. A sequence of eight major aquifer groups separated by eight aquitards and two aquicludes was identified. The fluid flow in the Paleozoic aquifers is mainly horizontal and regional in nature, being driven by the difference in hydraulic potential between the high areas in the foothills and the lowland areas in the prairies. The fluid flow in the Cretaceous aquifers is of regional to intermediate type, with a significant downward component. The fluid flow in the aquitards is vertical. The very low permeability of the strata is reflected in flow velocities on the order of magnitude of 1 cm/a and less. Dimensional analysis of heat transport processes in each hydrostratigraphic unit shows that convective heat transfer is negligible with respect to conductive heat transfer. The respective values of the Peclet number for heat flow in porous media areas are less than 10-2. In the Swan Hills and Cold Lakes areas the flow of the terrestrial heat flux from the crystalline Precambrian basement of the sedimentary basin to the atmosphere is controlled by the geometry and the changes in the thermal properties of the formations in the basin. The geothermal gradients for individual layers vary from 17 mK/m for sandstone units to 42 mK/m for shales. The integral geothermal gradient of the entire sedimentary column varies between 22 mK/m and 36 mK/m. The areal distribution of the integral geothermal gradient shows a strong correlation with stratigraphy and lithology.

Peristalsis for MHD hybrid nanomaterial through asymmetric channel

Objective here is to address impacts of MHD hybrid nanofluids (Fe2O3+Cu/H2O) on peristaltic transport in asymmetric channel. Porous space is taken. Analysis is constructed in the presence of radiation, dissipation, convection and Hall current. Further velocity and thermal slip boundary constraints are considered. Lubrication approach is employed to simplify the dimensionless forms of equations. Quantities of interest are described numerically. The shooting method is used to solve the governing differential systems employing Mathematica. Outcomes of Hartman number, Hall effect, permeability parameter, Grashof number and radiation parameter are analyzed graphically. Result indicates that temperature decreases by increasing the strength of nanomaterials. Axial velocity decays in the presence of Hartman number. Analysis of heat transport process is evaluated using tabulated values. Results show that heat process improved for Hartman number while the opposite behavior observed for Hall current.

Temperature-dependent surface tension model in many-body dissipative particle dynamics with energy conservation

As a hybrid method, many-body dissipative particle dynamics with energy conservation (MDPDe), promises to simulate heat transport process with free surface fluids. However, the temperature-dependent surface tension cannot be modelled accurately in MDPDe so far, which greatly limits its further applications. In the present study, semi-empirical relationships between the attractive coefficient and temperature obtained by mapping with real liquids (i.e., water, ethylene glycol and benzaldehyde) are introduced into MDPDe. The simulation results are validated by comparing with the relevant experimental, theoretical and numerical results, respectively. The improved MDPDe model in the present work opens the door to study various thermocapillary phenomena with free surface fluids at mesoscopic scale.

Non-Hermitian Chiral Heat Transport.

Exceptional point (EP) has been captivated as a concept of interpreting eigenvalue degeneracy and eigenstate exchange in non-Hermitian physics. The chirality in the vicinity of EP is intrinsically preserved and usually immune to external bias or perturbation, resulting in the robustness of asymmetric backscattering and directional emission in classical wave fields. Despite recent progress in non-Hermitian thermal diffusion, all state-of-the-art approaches fail to exhibit chiral states or directional robustness in heat transport. Here we report the first discovery of chiral heat transport, which is manifested only in the vicinity of EP but suppressed at the EP of a thermal system. The chiral heat transport demonstrates significant robustness against drastically varying advections and thermal perturbations imposed. Our results reveal the chirality in heat transport process and provide a novel strategy for manipulating mass, charge, and diffusive light.

Fractional melting process in inclined containers using (NePCM) and hybrid nanoparticles

Using substances of high latent heat such as phase change materials is a perfect technique in the energy storage units. Additionally, examining the heat transport and melting process for these materials is beneficial for a wide variety of solar-related applications. Therefore, this study aims to examine the time-dependent fractional melting process within inclined containers filled with Nanoparticles-enhanced Phase-Change Materials (NePCM) via the model of the enthalpy-porosity. The used NePCM is octadecane and the fractional derivatives are considered for all the time-dependent variables, namely, velocities, temperature and liquid fraction. The Caputo definition is applied to estimate the non-integer derivatives and the fractional order takes the values between 0.75 and 0.95. The solution methodology is depending on the Finite Volume technique with SIMPLE approach. The range of the Fourier number is between 0.05 and 0.4 and the resulting data is presented in terms of melting interface, liquid fraction, streamlines, isotherms and heat transfer rate. The main findings revealed that the influences of order of the fractional derivatives more significant at the higher values of the Fourier number and the melting interface points move towards the heated wall as order of the fractional derivatives is reduced. Also, at higher values of the fractional derivative's order (0.9), the maximizing of inclination angle causes a diminishing in the rate of the heat transfer.

Thermal Conductivity and Thermal Diffusivity of Tremolite at High Temperature and Pressure and Implications for the Thermal Structure of the Venusian Lithosphere

AbstractThermal conductivity (κ) and thermal diffusivity (D) of tremolite were measured at up to 2.5 GPa and 1,373 K using the transient plane‐source method in a multi‐anvil apparatus. Thermal conductivity and thermal diffusivity of tremolite decrease monotonically before dehydration (<1,173 K) and increase significantly after dehydration. Tremolite exhibits positive pressure dependence before dehydration. Heat capacity (C) of tremolite calculated fromκandDshows a positive pressure dependence and is controlled by an almost constant thermal expansion coefficient (α) with temperature. Conductive heat transport and radiative heat transport dominate the heat transport process before dehydration, and the significant increase in thermal conductivity after dehydration is attributed to convective heat transport. A compositional model of the Venusian lithosphere composed of a basaltic crust and peridotite mantle with or without tremolite was established. The thickness of the Venusian lithosphere with or without tremolite for Venus was calculated by combining the heat flow (from 20 to 80 mW/m2) at a certain depth (from 5 to 25 km) of crust, ranging from 24.4 to 184.6 km.

Heat transport in magnetohydrodynamic physiological blood flow through a constricted artery

AbstractIn this paper, we study how the magnetohydrodynamic (MHD) pulsatile flow of blood and heat transfer works through a constricted artery with a flexible wall. The human circulatory network consists of veins and arteries that sometimes contain constrictions, allowing the impact of the applied magnetic field on flow fields to be observed. The walls of the flowing medium are considered to be a function of time. The flowing blood is hypothesized as shear‐thinning fluid, emulating Yeleswarapu's viscosity replica. Additionally, we consider the energy equation to understand the impact of a magnetic field on heat transfer rates for such flows. The vorticity transport equation along with the stream function equation is obtained using the vorticity–stream function technique. Numerical solutions of the governing nonlinear MHD equations and energy equation in addition to physically pertinent flow conditions were achieved by adapting a finite difference scheme. Considerable attention has been paid to ensure an accurate comparison between the current and previous results. The two sets of numbers appear to match closely. For an even deeper understanding of the flow and heat transport process, the effects of height of stenosis and diverse physiological parameters on time‐averaged wall shear stress (TAWSS), rate of heat transport, and so on are explored in depth through their graphical depiction. In the vicinity of the constriction, it is observed that the separation becomes longer with increasing constriction height. Higher magnetic force strength leads to a reduction in separation length. Newtonian fluids transfer heat more rapidly in their narrowing regions and downstream than fluids with non‐Newtonian behavior.

Investigation of quadratically stratified squeezed Casson fluid flow with slip features over a convectively heated surface

There are diverse engineering and industrial related dynamical systems where the dissipative phenomenon in non-Newtonian fluids have given great significance. Example includes aerodynamics heating process, flows of polymer processing (injection molding, extrusion, etc.), and flow of fluid in small devices under associated heat transport process. Here, this attempt presents an analytical study of the squeezing mechanism. The squeezed material is presented utilizing the Casson incompressible fluid model. Viscous dissipation impacts along with convective surface conditions are retained in this study. A slip and stratification analysis in respect of unsteady flow, heat and mass transfer is performed in this attempt. The governing equations under the squeezing process are made first simplified and then transformed into dimensionless form using the similarity variables. Here, homotopic technique has been implemented in order to solve the dimensionless equations. Outcomes of velocity, heat, and mass transport mechanisms are discussed graphically in detail against pertinent parameters. In this analysis the heat and mass transport increases with increasing thermal and solutal Biot number, however the velocity decrements near the sheets as the slip parameter increases. Moreover, study concludes that squeezing mechanism intensifies the flow velocity. Phenomenon of squeezing experiences numerous industrial related processes such as mechanisms of lubrication, engine cooling system, designing permeable surfaces to minimize drag, etc., Force of drag is decreased further because of squeezing parameter. Therefore, because of low drag force, minimum amount of energy related resources can be utilized.

Bubble-induced oscillating flow in microbubble emission boiling under highly subcooled conditions

Microbubble emission boiling (MEB), a phenomenon that occurs under highly subcooled boiling conditions, can achieve a high heat flux beyond critical heat flux. MEB has been observed to differ from nucleate boiling and is always accompanied by the emission of microbubbles from an oscillating bubble. The heat transfer mechanism of MEB differs from that of nucleate boiling and remains elusive. In this study, we measure the behaviour of a vapour bubble and its induced liquid flow simultaneously during subcooled boiling using the high-speed two-phase particle image velocimetry method. Different from nucleate boiling, we observe a rapid oscillating flow outside the bubble that constantly attaches on the heating surface in MEB. The spatially and temporally averaged velocity magnitude values under this oscillating flow, and their dependency on liquid subcooling and heat flux, are quantified. Then we derive a scaling law for the heat transfer of MEB as a function of Péclet and Jacob numbers. With such correlations, we suggest that the oscillating flow induced by bubble oscillations is important to MEB, thus elucidating a different heat transport process from nucleate boiling.

Vieta-Lucas Collocation Technique for Examination of the Flow of Casson Fluid over a Slippery Stretching Sheet Which Is Impacted by Thermal Slip, Ohmic Dissipation, and Variable Thermal Conductivity

This work aimed to present the influence of the magnetic field and Ohmic dissipation on the non-Newtonian Casson fluid on a vertical stretched sheet to numerically solve the problem. Here, the variable thermal conductivity is taken as a linear function of temperature. Electric fields, thermal slip, and viscous dissipation effects are taken into consideration. A collection of physical conditions on the sheet’s enclosing wall and the momentum and heat transport processes are expressed as partial differential equations (PDEs). Some of the similarity transformations are used to convert the collection of PDE into a system of ordinary differential equations. This system is numerically treated by implementing the Vieta-Lucas spectral collocation method. Some observations are made for the investigation of method convergence. The effect of some different parameters on the velocity and temperature profiles is graphically represented. Additionally, this area of study has significant practical applications in a variety of industries, including paper production, thermal power generation, nuclear reactors, cooling of metallic sheets, glass fiber, and lubrication.

Multi-dimensional characteristics of upward bubbly flows in a vertical large-size square channel

Gas-liquid two-phase flows frequently occur in various flow channels in engineering systems with heat and mass transport processes. The channel geometry affects thermo-fluid behavior generally. Extensive research is done on gas-liquid two-phase flows in circular and annular channels with a wealth of local two-phase flow measurement data. Square channels are used in various engineering disciplines, but there has only been limited experimental research on two-phase flows in square channels with local flow parameter measurements. For two-phase flow analyses in square channels, knowledge of the flow characteristics and model validation against some key parameters, such as the drift-flux parameters and the interfacial area concentration, is crucial. An experiment for upward bubbly flows was conducted in a large square channel with an inside cross-section of 0.136 × 0.136 m. A four-sensor optical probe and a hot-film anemometer were used to measure local two-phase flow parameters at 66 points in an octant symmetric triangular cross-section at three axial locations. The measured two-phase flow parameters were the void fraction, axial gas velocity, axial liquid velocity, interfacial area concentration, and bubble Sauter mean diameter. The flow characteristics through flow development were investigated based on the local measurement data. The local measurement data directly determined the drift-flux parameters through their definitions. The distribution parameters determined through experimentation could be reproduced by the existing correlation for large circular pipes indicating that the flow characteristics in large square channels may be similar to those in large circular pipes. Based on existing drift-flux correlations for large circular pipes, the void fractions in the current experiment could be fairly predicted. Furthermore, the interfacial area concentrations could be predicted by existing correlations with reasonable accuracy.

The nonlocal electron heat transport under the non-Maxwellian distribution in laser plasmas and its influence on laser ablation

The electron heat transport plays an important role in laser driven inertial confinement fusion. For the plasmas created by intense laser, the traditional Spitzer–Härm theory cannot accurately describe the electron heat transport process mainly due to two physical effects. First, the electron distribution function would significantly differ from the Maxwellian distribution because of the inverse bremsstrahlung heating. Second, the long mean free paths of heat carrying electrons relative to the temperature scale length indicate that the electron heat flux has the nonlocal feature. In 2020, we have developed a nonlocal electron heat transport model based on the non-Maxwellian electron distribution function (NM-NL model) to describe the electron heat flux in laser plasmas. Recently, this model is successfully incorporated into our radiation hydrodynamical code RDMG. In this article, we numerically investigated the electron heat flux in laser plasmas, especially the nonlocal feature of heat flux and the influence of the non-Maxwellian distribution. The influence of electron heat transport on laser ablation is also discussed. The simulated plasma conditions based on different electron heat transport models are presented and compared with experiments. Our results show that the nonlocal feature of heat flux and the influence of non-Maxwellian distribution function are considerable in plasmas heated by intense lasers.

The criterion of planar instability in alloy solidification under varying conditions: A viewpoint from free energy

In alloy solidification, the transport processes of heat and solute result in morphological instability of the interface, forming different patterns of the solidification structure and determining the mechanical properties of components. As the first observable phenomenon of morphological instabilities, planar instability influences the subsequent stages significantly, deserving in-depth investigations. In this paper, the planar instability in alloy solidification under varying conditions is studied. First, the dynamical evolution of the planar instability is performed by the theoretical model and the phase-field model, respectively. Second, to represent the history-dependence of solidification, varying parameters are adopted in the simulations. Then, the criterion of planar instability under varying conditions is discussed. This paper considers that the critical parameters of planar instability are the excess free energy at the interface and the corresponding interfacial energy. Finally, to validate the criterion, comparisons between the phase-field and theoretical models are carried out, showing good consistency. Moreover, solidification processes with different preferred crystallographic orientations are performed, demonstrating the effect mechanism of the excess free energy and interfacial energy on planar instability. The idea of the interfacial energy influencing the planar instability could be applied to investigating other patterns induced by interfacial instability.

Drying Drops of Colloidal Dispersions.

Drying drops of colloidal dispersions have attracted attention from researchers since the nineteenth century. The multiscale nature of the problem involving physics at different scales, namely colloidal and interfacial phenomena as well as heat, mass, and momentum transport processes, combined with the seemingly simple yet nontrivial shape of the drops makes drying drop problems rich and interesting. The scope of such studies widens as the physical and chemical nature of dispersed entities in the drop vary and as evaporation occurs in more complex configurations. This review summarizes past and contemporary developments in the field, emphasizing the physicochemical and hydrodynamical principles that govern the processes occurring within a drying drop and the resulting variety of patterns generated on the substrate.

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.