The Dufour and Soret effects on the unsteady twodimensional magnetonyaro dynamics （MHD） doublediffusive free convective flow of an electrically conducting fluid past a vertical plate embedded in a nonDarcy porous me...The Dufour and Soret effects on the unsteady twodimensional magnetonyaro dynamics （MHD） doublediffusive free convective flow of an electrically conducting fluid past a vertical plate embedded in a nonDarcy porous medium are investigated numeri cally. The governing nonlinear dimensionless equations are solved by an implicit finite difference scheme of the CrankNicolson type with a tridiagonal matrix manipulation. The effects of various parameters entering into the problem on the unsteady dimension less velocity, temperature, and concentration profiles are studied in detail. Furthermore, the time variation of the skin friction coefficient, the Nusselt number, and the Sherwood number is presented and analyzed. The results show that the unsteady velocity, tem perature, and concentration profiles are substantially influenced by the Dufour and Soret effects. When the Dufour number increases or the Soret number decreases, both the skin friction and the Sherwood number decrease, while the Nusselt number increases. It is found that, when the magnetic parameter increases, the velocity and the temperature decrease in the boundary layer.展开更多
The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective bound...The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.展开更多
This article studies the Soret and Dufour effects on the magnetohydrody- namic （MHD） flow of the Casson fluid over a stretched surface. The relevant equations are first derived, and the series solution is constructe...This article studies the Soret and Dufour effects on the magnetohydrody- namic （MHD） flow of the Casson fluid over a stretched surface. The relevant equations are first derived, and the series solution is constructed by the homotopic procedure. The results for velocities, temperature, and concentration fields are displayed and discussed. Numerical values of the skin friction coefficient, the Nusselt number, and the Sherwood number for different values of physical parameters are constructed and analyzed. The convergence of the series solutions is examined.展开更多
Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall ...Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall current and constant heat flux. It is considered that the porous plate is subjected to constant heat flux. The obtained non-dimensional, non-similar coupled non-linear and partial differential equations have been solved by explicit finite difference technique. Numerical solutions for velocities, temperature and concentration distributions are obtained for various parameters by the above mentioned technique. The local and average shear stresses, Nusselt number as well as Sherwood number are also investigated. The stability conditions and convergence criteria of the explicit finite difference scheme are established for finding the restriction of the values of various parameters to get more accuracy. The obtained results are illustrated with the help of graphs to observe the effects of various legitimate parameters.展开更多
A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equati...A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equations (PDE) are transformed to a system of dimensionless non-similar coupled PDEs. The transformed, non-similar conservations equations (momentum balance equation, energy balance equation and concentration balance equation) are then solved using a numerical approach known as explicit finite difference method (EFDM). Basically EFDM introduced for the unsteadiness in the momentum, temperature, and concentration fluid fields is based on the time dependent fluid velocity, temperature and concentration of the boundary surface. During the course of discussion, it is found that the various parameters related to the problem influence the calculated resultant expressions. The computed numerical solution results for the velocity, temperature, and concentration distribution with the effect of various important dimensionless parameters (Grashof number, Modified Grashof number, Prandtl number, Schmidt number, Soret number, Dufour number, chemical reaction parameter and inclination parameter) entering into the problems are critically analyzed and discussed graphically. It can be seen that two physical phenomena chemical reaction and thermal diffusion can greatly effect on the boundary layer fluid flows through an inclined plate.展开更多
The effect of chemical reaction on free convection heat and mass transfer for a non-Newtonian power law fluid over a vertical flat plate embedded in a fluid-saturated porous medium has been studied in the presence of ...The effect of chemical reaction on free convection heat and mass transfer for a non-Newtonian power law fluid over a vertical flat plate embedded in a fluid-saturated porous medium has been studied in the presence of the yield stress and the Soret effect. The governing boundary layer equations and boundary conditions are cast into a dimen- sionless form by similarity transformations, and the resulting system of equations is solved by a finite difference method. The results are preSented and discussed for concentration profiles, as well as the Nusselt number and the Sherwood number for various values of the parameters, which govern the problem. The results obtained show that the flow field is influenced appreciably by the presence of the chemical reaction parameter γ the order of.the chemical reaction parameter m, the Soret number St, the buoyancy ratio N, the Lewis number Le, and the dimensionless rheological parameter Ω.展开更多
The transient growth due to non-normMity is investigated for the Poiseuille- Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = -0.1, it is found that a large ...The transient growth due to non-normMity is investigated for the Poiseuille- Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = -0.1, it is found that a large transient growth can be obtained by the non-normal interaction of the two least-stable-modes, i.e., the upstream and downstream modes, which determine the linear critical boundary curves for small Reynolds numbers. The transient growth is so strong that the optimal energy amplification factor G（t） is up to 10^2 - 10^3. While for positive separation factors such as ψ = 0.1, the transient growth is weak with the order O（I） of the amplification factor, which can even be computed by the least-stable-mode. However, for both cases, the least-stable-mode can govern the long-term behavior of the amplification factor for large time. The results also show that large Reynolds numbers have stabilization effects for the maximum amplification within moderate wave number regions. Meanwhile, much small negative or large positive separation factors and large Rayleigh numbers can enlarge the maximum transient growth of the pure streamwise disturbance with the wavenumber α= 3.14. Moreover, the initial and evolutionary two-dimensional spatial patterns of the large transient growth for the pure streamwise disturbance are exhibited with a plot of the velocity vector, spanwise vorticity, temperature, and concentration field. The initial three-layer cell vorticity struc- ture is revealed. When the amplification factor reaches the maximum Gmax, it develops into one cell structure with large amplification for the vorticity strength.展开更多
Double-diffusive stationary and oscillatory instabilities at the marginal state in a saturated porous horizontal fluid layer heated and salted from above are investigated theoretically under the Darcy＇s framework for...Double-diffusive stationary and oscillatory instabilities at the marginal state in a saturated porous horizontal fluid layer heated and salted from above are investigated theoretically under the Darcy＇s framework for a porous medium. The contributions of Soret and Dufour coefficients are taken into account in the analysis. Linear stability analysis shows that the critical value of the Darcy-Rayleigh number depends on cross-diffusive parameters at marginally stationary convec- tion, while the marginal state characterized by oscillatory convection does not depend on the cross-diffusion terms even if the condition and frequency of oscillatory convection depends on the cross-diffusive parameters. The critical value of the Darcy-Rayleigh number increases with increasing value of the solutal Darcy-Rayleigh number in the absence of cross- diffusive parameters. The critical Darcy-Rayleigh number decreases with increasing Soret number, resulting in destabiliza- tion of the system, while its value increases with increasing Dufour number, resulting in stabilization of the system at the marginal state characterized by stationary convection. The analysis reveals that the Dufour and Soret parameters as well as the porosity parameter play an important role in deciding the type of instability at the onset. This analysis also indicates that the stationary convection is followed by the oscillatory convection for certain fluid mixtures. It is interesting to note that the roles of cross-diffusive parameters on the double-diffusive system heated and salted from above are reciprocal to the double-diffusive system heated and salted from below.展开更多
This study presents a generalized two-dimensional model for evaluating the stationary hygro-thermo-mechanical response of laminated shell structures made of advanced materials.It introduces a generalized kinematic mod...This study presents a generalized two-dimensional model for evaluating the stationary hygro-thermo-mechanical response of laminated shell structures made of advanced materials.It introduces a generalized kinematic model,enabling the assessment of arbitrary values of temperature variation and mass concentration variation for the unvaried configuration at the top and bottom surfaces.This is achieved through the Equivalent Layer-Wise description of the unknown field variable using higher-order polynomials and zigzag functions.In addition,an elastic foundation is modeled utilizing the Winkler-Pasternak theory.The fundamental equations,derived from the total free energy of the system,are solved analytically using Navier’s method.Then,the Fourier-based generalized differential quadrature numerical method is adopted to efficiently recover the through-the-thickness distribution of secondary variables in agreement with the hygro-thermal loading conditions.The formulation is applied in some examples of investigation where the response of panels of different curvature and lamination schemes is evaluated under external hygro-thermal fluxes and prescribed values of temperature and moisture concentration.In addition,this study investigates the effect of the hygro-thermal coupling due to Dufour and Soret effect.The present formulation is verified to be a valuable tool for reducing computational effort and determining the effect on the mechanical response of laminated structures in a thermal and hygrometric environment.展开更多
Thermally chargeable supercapacitors(TCSCs)have unique advantages in the collection,conversion,and storage of thermal energy,contributing to the development of new strategies for thermal energy utilization.2D MXene ma...Thermally chargeable supercapacitors(TCSCs)have unique advantages in the collection,conversion,and storage of thermal energy,contributing to the development of new strategies for thermal energy utilization.2D MXene materials are predicted to be highly promising new thermoelectric materials.Here,we report a self-assembled flexible Ti_(3)C_(2)T_(x) MXenebased TCSC device,using prepared Ti_(3)C_(2)T_(x) MXene as the capacitor electrode and a NaClO_(4)/PEO gel as the electrolyte.We also explore the working mechanism of the TCSCs.The fabricated Ti_(3)C_(2)T_(x)-based TCSCs exhibit an excellent Seebeck coefficient of 11.8 mV∙K^(−1) on average and maintain good cycling stability under various temperature differences.Demonstrations of multiple practical applications show that Ti_(3)C_(2)T_(x) MXene-based TCSC devices are excellent candidates for self-powered integrated electronic devices.展开更多
The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical a...The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical applications for thermoelectrics is the high cost from both materials and manufacturing.Recently,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature gradient.The charging voltage is internally from the ionic Seebeck effect of the electrolyte between two electrodes.Hence electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric materials.Most ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic materials.This emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic thermodiffusion.In this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application developments.We present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.展开更多
Thermally chargeable supercapacitors can collect low-grade heat generated by the human body and convert it into electricity as a power supply unit for wearable electronics.However,the low Seebeck coefficient and heat-...Thermally chargeable supercapacitors can collect low-grade heat generated by the human body and convert it into electricity as a power supply unit for wearable electronics.However,the low Seebeck coefficient and heat-to-electricity conversion efficiency hinder further application.In this paper,we designed a high-performance thermally chargeable supercapacitor device composed of ZnMn_(2)O_(4)@Ti_(3)C_(2)T_(x)MXene composites(ZMO@Ti_(3)C_(2)T_(x) MXene)electrode and UIO-66 metal–organic framework doped multichannel polyvinylidene fluoridehexafluoro-propylene ionogel electrolyte,which realized the thermoelectric conversion and electrical energy storage at the same time.This thermally chargeable supercapacitor device exhibited a high Seebeck coefficient of 55.4 mV K^(−1),thermal voltage of 243 mV,and outstanding heat-to-electricity conversion efficiency of up to 6.48%at the temperature difference of 4.4 K.In addition,this device showed excellent charge–discharge cycling stability at high-temperature differences(3 K)and low-temperature differences(1 K),respectively.Connecting two thermally chargeable supercapacitor units in series,the generated output voltage of 500 mV further confirmed the stability of devices.When a single device was worn on the arm,a thermal voltage of 208.3 mV was obtained indicating the possibility of application in wearable electronics.展开更多
An unsteady viscous fluid flow with Dufour and Soret effect,which results in heat and mass transfer due to upward and downward motion of flexible rotating disk,has been studied.The upward or downward motion of non rot...An unsteady viscous fluid flow with Dufour and Soret effect,which results in heat and mass transfer due to upward and downward motion of flexible rotating disk,has been studied.The upward or downward motion of non rotating disk results in two dimensional flow,while the vertical action and rotation of the disk results in three dimensional flow.By using an appropriate transformation the governing equations are transformed into the system of ordinary differential equations.The system of ordinary differential equations is further converted into first order differential equation by selecting suitable variables.Then,we generalize the model by using the Caputo derivative.The numerical result for the fractional model is presented and validated with Runge Kutta order 4 method for classical case.The compared results are presented in Table and Figures.It is concluded that the fractional model is more realistic than that of classical one,because it simulates the fluid behavior at each fractional value rather than the integral values.展开更多
A mathematical model for the steady,mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a micropolar fluid in the presence of Soret and Dufour effects is presented.The non-linear g...A mathematical model for the steady,mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a micropolar fluid in the presence of Soret and Dufour effects is presented.The non-linear governing equations and their associated boundary conditions are initially cast into dimensionless forms using local similarity transformations.The resulting system of equations is then solved numerically using the Keller-box method.The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation.The non-dimensional velocity,microrotation,temperature and concentration profiles are displayed graphically for different values of coupling number,Soret and Dufour numbers.In addition,the skin-friction coefficient,the Nusselt number and Sherwood number are shown in a tabular form.展开更多
Thermally chargeable supercapacitors(TCSCs)have offered exceptional energy-converting efficiency for absorbing human epidermal heat and generating and storing electrical energy,which then realize continuous power supp...Thermally chargeable supercapacitors(TCSCs)have offered exceptional energy-converting efficiency for absorbing human epidermal heat and generating and storing electrical energy,which then realize continuous power supply to electronic devices,such as sensors and wearable electronic products,in a wide range of practical significance.Here,we proposed a flexible TCSC by attaching binder-free Ti_(3)C_(2)T_(x) MXene@PPy electrodes on both ends of the H_(3)PO_(4)@P(AM-co-AA-co-AYP K^(+))hydrogel electrolyte,which exhibits a large thermal power of 35.2 mV K^(−1) at 50%relative humidity and maximum figure of merit of 2.1.The high performances of the fabricated devices can be attributed to the tunable electrical,thermodynamic,thermoelectric,and mechanical properties of the hydrogel electrolyte by adjusting the acid content and the proportion of zwitterionic compound AYP K^(+)in the hydrogel,and the high photothermal conversion efficiency and electrochemical performance of the electrodes.Moreover,the stable and outstanding thermofvoltage output(∼200 mV)under different time scenarios of the TCSC makes it possible to drive a strain sensor,accomplishing the objectives of a human activity monitor.展开更多
The influences of Soret effect and Dufour effect on the natural convectionand heal and mass transfer for a porous enclosure were investigated by means of the penalty finiteelement method. Numerical results indicate th...The influences of Soret effect and Dufour effect on the natural convectionand heal and mass transfer for a porous enclosure were investigated by means of the penalty finiteelement method. Numerical results indicate that the Soret and Dufour effects have significantinfluences on heat and mass transfer in the presence of large temperature gradient and concentrationgradient.展开更多
The integration of ionic power generation with solar-driven water evaporation presents a promising solution to the critical global problems of freshwater scarcity and clean energy deficiency.In this work,a scalable no...The integration of ionic power generation with solar-driven water evaporation presents a promising solution to the critical global problems of freshwater scarcity and clean energy deficiency.In this work,a scalable normal temperature chemical vapor deposition(CVD)method is applied for the first time to the fabrication of a cellulose@polypyrrole(CC@PPy)membrane with efficient ionic power generation performance.The excellent ionic power generation is intimately related to the water and thermal gradients across the membrane,which not only induces fast water evaporation but also synergistically promotes the transport of counterions in charged nanochannels,and the corresponding mechanism is attributed to the streaming potential resulting from the ionic electrokinetic effect and the ionic thermoelectric potential originating from the Soret effect.Under one sun illumination,the CC@PPy film can produce a sustained voltage output of~0.7 V and a water evaporation rate up to 1.67 kg m^(−2)h^(−1)when an adequate water supply is available.This study provides new methods for the scalable fabrication of ionic power generation membranes and a design strategy for high-performance solar power generators.展开更多
Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the ...Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the free surface.The pool is heated from the outer cylinder with high solutal concentration and cooled at the inner cylinder with low solutal concentration.The asymptotic solution is obtained in the core region in the limit as the aspect ratio,which is defined as the ratio of the depth to the width of the pool,goes to zero.The comparison with the previous work certifies that the asymptotic solution is right and believable.The influences of the solutal capillary force,the buoyant force,the Soret effect and the geometric parameters on the fluid flow are analyzed.展开更多
Ionic thermoelectricity(i-TE),as a new energy conversion and storage technology,has been widely discussed by the academic community.As one of the representatives of low-grade thermal energy recovery,i-TE has made rema...Ionic thermoelectricity(i-TE),as a new energy conversion and storage technology,has been widely discussed by the academic community.As one of the representatives of low-grade thermal energy recovery,i-TE has made remarkable progress and become an influential research direction in the energy field.Among them,thermoelectric ionogels have a wide range of applications in the field of energy recovery and utilization due to their excellent flexibility,stability,and thermoelectric conversion ability,providing many application possibilities for such materials.The development of highly efficient and stable ionic thermoelectric devices is largely dependent on the development of new materials and structural designs.This paper focuses on the recent strategies for improving the efficiency of thermoelectric conversion in the field of ionic thermoelectric gels,including new methods for material design,structural optimization,and innovative developments in the application of thermoelectric materials.The evaluation indicators of thermoelectric conversion efficiency are discussed,including ionic thermal voltage,ionic conductivity and power output,ductility,and self-healing properties.Additionally,various application devices based on thermoelectric materials with excellent thermoelectric conversion properties are highlighted.Further,different challenges and strategies that need to be addressed are presented in the hope of providing inspiration and guidance for the commercialization of i-TE.展开更多
During the past decade,there has been extensive research toward the possibility of exploring magnesium and its alloys as biocompatible and biodegradable materials for implantable applications.Its practical medical app...During the past decade,there has been extensive research toward the possibility of exploring magnesium and its alloys as biocompatible and biodegradable materials for implantable applications.Its practical medical application,however,has been limited to specific areas owing to rapid corrosion in the initial stage and the consequent complications.Surface coatings can significantly reduce the initial corrosion of Mg alloys,and several studies have been carried out to improve the adhesion strength of the coating to the surfaces of the alloys.The composition of hydroxyapatite(HAp)is very similar to that of bone tissue;it is one of the most commonly used coating materials for bone-related implants owing to favorable osseointegration post-implantation.In this study,HAp was coated on Mg using nanosecond laser coating,combining the advantages of chemical and physical treatments.Photothermal heat generated in the liquid precursor by the laser improved the adhesion of the coating through the precipitation and growth of HAp at the localized nanosecond laser focal area and increased the corrosion resistance and cell adhesion of Mg.The physical,crystallographic,and chemical bondings were analyzed to explore the mechanism through which the surface adhesion between Mg and the HAp coating layer increased.The applicability of the coating to Mg screws used for clinical devices and improvement in its corrosion property were confirmed.The liquid environment-based laser surface coating technique offers a simple and quick process that does not require any chemical ligands,and therefore,overcomes a potential obstacle in its clinical use.展开更多
文摘The Dufour and Soret effects on the unsteady twodimensional magnetonyaro dynamics （MHD） doublediffusive free convective flow of an electrically conducting fluid past a vertical plate embedded in a nonDarcy porous medium are investigated numeri cally. The governing nonlinear dimensionless equations are solved by an implicit finite difference scheme of the CrankNicolson type with a tridiagonal matrix manipulation. The effects of various parameters entering into the problem on the unsteady dimension less velocity, temperature, and concentration profiles are studied in detail. Furthermore, the time variation of the skin friction coefficient, the Nusselt number, and the Sherwood number is presented and analyzed. The results show that the unsteady velocity, tem perature, and concentration profiles are substantially influenced by the Dufour and Soret effects. When the Dufour number increases or the Soret number decreases, both the skin friction and the Sherwood number decrease, while the Nusselt number increases. It is found that, when the magnetic parameter increases, the velocity and the temperature decrease in the boundary layer.
基金the Higher Education Commission of Pakistan (HEC) for the financial support through Indigenous program
文摘The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.
基金supported by the Deanship of Scientific Research (DSR) of King Abdulaziz University of Saudi Arabia
文摘This article studies the Soret and Dufour effects on the magnetohydrody- namic （MHD） flow of the Casson fluid over a stretched surface. The relevant equations are first derived, and the series solution is constructed by the homotopic procedure. The results for velocities, temperature, and concentration fields are displayed and discussed. Numerical values of the skin friction coefficient, the Nusselt number, and the Sherwood number for different values of physical parameters are constructed and analyzed. The convergence of the series solutions is examined.
文摘Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall current and constant heat flux. It is considered that the porous plate is subjected to constant heat flux. The obtained non-dimensional, non-similar coupled non-linear and partial differential equations have been solved by explicit finite difference technique. Numerical solutions for velocities, temperature and concentration distributions are obtained for various parameters by the above mentioned technique. The local and average shear stresses, Nusselt number as well as Sherwood number are also investigated. The stability conditions and convergence criteria of the explicit finite difference scheme are established for finding the restriction of the values of various parameters to get more accuracy. The obtained results are illustrated with the help of graphs to observe the effects of various legitimate parameters.
文摘A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equations (PDE) are transformed to a system of dimensionless non-similar coupled PDEs. The transformed, non-similar conservations equations (momentum balance equation, energy balance equation and concentration balance equation) are then solved using a numerical approach known as explicit finite difference method (EFDM). Basically EFDM introduced for the unsteadiness in the momentum, temperature, and concentration fluid fields is based on the time dependent fluid velocity, temperature and concentration of the boundary surface. During the course of discussion, it is found that the various parameters related to the problem influence the calculated resultant expressions. The computed numerical solution results for the velocity, temperature, and concentration distribution with the effect of various important dimensionless parameters (Grashof number, Modified Grashof number, Prandtl number, Schmidt number, Soret number, Dufour number, chemical reaction parameter and inclination parameter) entering into the problems are critically analyzed and discussed graphically. It can be seen that two physical phenomena chemical reaction and thermal diffusion can greatly effect on the boundary layer fluid flows through an inclined plate.
文摘The effect of chemical reaction on free convection heat and mass transfer for a non-Newtonian power law fluid over a vertical flat plate embedded in a fluid-saturated porous medium has been studied in the presence of the yield stress and the Soret effect. The governing boundary layer equations and boundary conditions are cast into a dimen- sionless form by similarity transformations, and the resulting system of equations is solved by a finite difference method. The results are preSented and discussed for concentration profiles, as well as the Nusselt number and the Sherwood number for various values of the parameters, which govern the problem. The results obtained show that the flow field is influenced appreciably by the presence of the chemical reaction parameter γ the order of.the chemical reaction parameter m, the Soret number St, the buoyancy ratio N, the Lewis number Le, and the dimensionless rheological parameter Ω.
基金Project supported by the National Natural Science Foundation of China(Nos.11172049 and11472060)
文摘The transient growth due to non-normMity is investigated for the Poiseuille- Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = -0.1, it is found that a large transient growth can be obtained by the non-normal interaction of the two least-stable-modes, i.e., the upstream and downstream modes, which determine the linear critical boundary curves for small Reynolds numbers. The transient growth is so strong that the optimal energy amplification factor G（t） is up to 10^2 - 10^3. While for positive separation factors such as ψ = 0.1, the transient growth is weak with the order O（I） of the amplification factor, which can even be computed by the least-stable-mode. However, for both cases, the least-stable-mode can govern the long-term behavior of the amplification factor for large time. The results also show that large Reynolds numbers have stabilization effects for the maximum amplification within moderate wave number regions. Meanwhile, much small negative or large positive separation factors and large Rayleigh numbers can enlarge the maximum transient growth of the pure streamwise disturbance with the wavenumber α= 3.14. Moreover, the initial and evolutionary two-dimensional spatial patterns of the large transient growth for the pure streamwise disturbance are exhibited with a plot of the velocity vector, spanwise vorticity, temperature, and concentration field. The initial three-layer cell vorticity struc- ture is revealed. When the amplification factor reaches the maximum Gmax, it develops into one cell structure with large amplification for the vorticity strength.
基金support received from UGC, DSA-I in the Department of Mathematics, the University of Burdwan
文摘Double-diffusive stationary and oscillatory instabilities at the marginal state in a saturated porous horizontal fluid layer heated and salted from above are investigated theoretically under the Darcy＇s framework for a porous medium. The contributions of Soret and Dufour coefficients are taken into account in the analysis. Linear stability analysis shows that the critical value of the Darcy-Rayleigh number depends on cross-diffusive parameters at marginally stationary convec- tion, while the marginal state characterized by oscillatory convection does not depend on the cross-diffusion terms even if the condition and frequency of oscillatory convection depends on the cross-diffusive parameters. The critical value of the Darcy-Rayleigh number increases with increasing value of the solutal Darcy-Rayleigh number in the absence of cross- diffusive parameters. The critical Darcy-Rayleigh number decreases with increasing Soret number, resulting in destabiliza- tion of the system, while its value increases with increasing Dufour number, resulting in stabilization of the system at the marginal state characterized by stationary convection. The analysis reveals that the Dufour and Soret parameters as well as the porosity parameter play an important role in deciding the type of instability at the onset. This analysis also indicates that the stationary convection is followed by the oscillatory convection for certain fluid mixtures. It is interesting to note that the roles of cross-diffusive parameters on the double-diffusive system heated and salted from above are reciprocal to the double-diffusive system heated and salted from below.
基金funded by the Project PNRR M4C2—Innovation grant DIRECT:Digital twIns foR EmergenCy supporT—CUP F83C22000740001.
文摘This study presents a generalized two-dimensional model for evaluating the stationary hygro-thermo-mechanical response of laminated shell structures made of advanced materials.It introduces a generalized kinematic model,enabling the assessment of arbitrary values of temperature variation and mass concentration variation for the unvaried configuration at the top and bottom surfaces.This is achieved through the Equivalent Layer-Wise description of the unknown field variable using higher-order polynomials and zigzag functions.In addition,an elastic foundation is modeled utilizing the Winkler-Pasternak theory.The fundamental equations,derived from the total free energy of the system,are solved analytically using Navier’s method.Then,the Fourier-based generalized differential quadrature numerical method is adopted to efficiently recover the through-the-thickness distribution of secondary variables in agreement with the hygro-thermal loading conditions.The formulation is applied in some examples of investigation where the response of panels of different curvature and lamination schemes is evaluated under external hygro-thermal fluxes and prescribed values of temperature and moisture concentration.In addition,this study investigates the effect of the hygro-thermal coupling due to Dufour and Soret effect.The present formulation is verified to be a valuable tool for reducing computational effort and determining the effect on the mechanical response of laminated structures in a thermal and hygrometric environment.
基金supported by National Natural Science Foundation of China(62474019)Beijing Natural Science Foundation(L223006).
文摘Thermally chargeable supercapacitors(TCSCs)have unique advantages in the collection,conversion,and storage of thermal energy,contributing to the development of new strategies for thermal energy utilization.2D MXene materials are predicted to be highly promising new thermoelectric materials.Here,we report a self-assembled flexible Ti_(3)C_(2)T_(x) MXenebased TCSC device,using prepared Ti_(3)C_(2)T_(x) MXene as the capacitor electrode and a NaClO_(4)/PEO gel as the electrolyte.We also explore the working mechanism of the TCSCs.The fabricated Ti_(3)C_(2)T_(x)-based TCSCs exhibit an excellent Seebeck coefficient of 11.8 mV∙K^(−1) on average and maintain good cycling stability under various temperature differences.Demonstrations of multiple practical applications show that Ti_(3)C_(2)T_(x) MXene-based TCSC devices are excellent candidates for self-powered integrated electronic devices.
基金support by the French National Research Agency through grant ANR-19-CE300012by the European Research Council(ERC)through grant No.772725。
文摘The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical applications for thermoelectrics is the high cost from both materials and manufacturing.Recently,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature gradient.The charging voltage is internally from the ionic Seebeck effect of the electrolyte between two electrodes.Hence electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric materials.Most ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic materials.This emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic thermodiffusion.In this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application developments.We present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.
基金supported by the National Natural Science Foundation of China(52273256)Beijing Municipal Natural Science Foundation(L223006)Beijing Institute of Technology Research Found Program for Young Scholars.
文摘Thermally chargeable supercapacitors can collect low-grade heat generated by the human body and convert it into electricity as a power supply unit for wearable electronics.However,the low Seebeck coefficient and heat-to-electricity conversion efficiency hinder further application.In this paper,we designed a high-performance thermally chargeable supercapacitor device composed of ZnMn_(2)O_(4)@Ti_(3)C_(2)T_(x)MXene composites(ZMO@Ti_(3)C_(2)T_(x) MXene)electrode and UIO-66 metal–organic framework doped multichannel polyvinylidene fluoridehexafluoro-propylene ionogel electrolyte,which realized the thermoelectric conversion and electrical energy storage at the same time.This thermally chargeable supercapacitor device exhibited a high Seebeck coefficient of 55.4 mV K^(−1),thermal voltage of 243 mV,and outstanding heat-to-electricity conversion efficiency of up to 6.48%at the temperature difference of 4.4 K.In addition,this device showed excellent charge–discharge cycling stability at high-temperature differences(3 K)and low-temperature differences(1 K),respectively.Connecting two thermally chargeable supercapacitor units in series,the generated output voltage of 500 mV further confirmed the stability of devices.When a single device was worn on the arm,a thermal voltage of 208.3 mV was obtained indicating the possibility of application in wearable electronics.
文摘An unsteady viscous fluid flow with Dufour and Soret effect,which results in heat and mass transfer due to upward and downward motion of flexible rotating disk,has been studied.The upward or downward motion of non rotating disk results in two dimensional flow,while the vertical action and rotation of the disk results in three dimensional flow.By using an appropriate transformation the governing equations are transformed into the system of ordinary differential equations.The system of ordinary differential equations is further converted into first order differential equation by selecting suitable variables.Then,we generalize the model by using the Caputo derivative.The numerical result for the fractional model is presented and validated with Runge Kutta order 4 method for classical case.The compared results are presented in Table and Figures.It is concluded that the fractional model is more realistic than that of classical one,because it simulates the fluid behavior at each fractional value rather than the integral values.
文摘A mathematical model for the steady,mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a micropolar fluid in the presence of Soret and Dufour effects is presented.The non-linear governing equations and their associated boundary conditions are initially cast into dimensionless forms using local similarity transformations.The resulting system of equations is then solved numerically using the Keller-box method.The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation.The non-dimensional velocity,microrotation,temperature and concentration profiles are displayed graphically for different values of coupling number,Soret and Dufour numbers.In addition,the skin-friction coefficient,the Nusselt number and Sherwood number are shown in a tabular form.
基金This work was supported by the Beijing Natural ScienceFoundation(L.223006)Beijing Institute of Technol-ogy Research Found Program for Young Scholars.
文摘Thermally chargeable supercapacitors(TCSCs)have offered exceptional energy-converting efficiency for absorbing human epidermal heat and generating and storing electrical energy,which then realize continuous power supply to electronic devices,such as sensors and wearable electronic products,in a wide range of practical significance.Here,we proposed a flexible TCSC by attaching binder-free Ti_(3)C_(2)T_(x) MXene@PPy electrodes on both ends of the H_(3)PO_(4)@P(AM-co-AA-co-AYP K^(+))hydrogel electrolyte,which exhibits a large thermal power of 35.2 mV K^(−1) at 50%relative humidity and maximum figure of merit of 2.1.The high performances of the fabricated devices can be attributed to the tunable electrical,thermodynamic,thermoelectric,and mechanical properties of the hydrogel electrolyte by adjusting the acid content and the proportion of zwitterionic compound AYP K^(+)in the hydrogel,and the high photothermal conversion efficiency and electrochemical performance of the electrodes.Moreover,the stable and outstanding thermofvoltage output(∼200 mV)under different time scenarios of the TCSC makes it possible to drive a strain sensor,accomplishing the objectives of a human activity monitor.
基金This work was supported by the National Natural Science Foundation of China.(Grant No:59806008)
文摘The influences of Soret effect and Dufour effect on the natural convectionand heal and mass transfer for a porous enclosure were investigated by means of the penalty finiteelement method. Numerical results indicate that the Soret and Dufour effects have significantinfluences on heat and mass transfer in the presence of large temperature gradient and concentrationgradient.
基金supported by the National Natural Science Foundation of China(Grant Nos.52162012,52262014,22308074,22368019)Key Research and Development Project of Hainan Province(Grant Nos.ZDYF2022SHFZ053)+1 种基金Science and Technology Innovation Talent Platform Fund for South China Sea New Star of Hainan Province(Grant No.NHXXRCXM202305)Open Research Project of State Key Laboratory of Marine Resource Utilization in South China Sea(Grant No.MRUKF2023020).
文摘The integration of ionic power generation with solar-driven water evaporation presents a promising solution to the critical global problems of freshwater scarcity and clean energy deficiency.In this work,a scalable normal temperature chemical vapor deposition(CVD)method is applied for the first time to the fabrication of a cellulose@polypyrrole(CC@PPy)membrane with efficient ionic power generation performance.The excellent ionic power generation is intimately related to the water and thermal gradients across the membrane,which not only induces fast water evaporation but also synergistically promotes the transport of counterions in charged nanochannels,and the corresponding mechanism is attributed to the streaming potential resulting from the ionic electrokinetic effect and the ionic thermoelectric potential originating from the Soret effect.Under one sun illumination,the CC@PPy film can produce a sustained voltage output of~0.7 V and a water evaporation rate up to 1.67 kg m^(−2)h^(−1)when an adequate water supply is available.This study provides new methods for the scalable fabrication of ionic power generation membranes and a design strategy for high-performance solar power generators.
基金supported by the National Natural Science Foundation of China (Grant No 51176209)
文摘Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the free surface.The pool is heated from the outer cylinder with high solutal concentration and cooled at the inner cylinder with low solutal concentration.The asymptotic solution is obtained in the core region in the limit as the aspect ratio,which is defined as the ratio of the depth to the width of the pool,goes to zero.The comparison with the previous work certifies that the asymptotic solution is right and believable.The influences of the solutal capillary force,the buoyant force,the Soret effect and the geometric parameters on the fluid flow are analyzed.
基金supported by research grants from the National Key R&D Program of China(grant no.2023YFB4704000)National Natural Science Foundation of China(NSFC+3 种基金grant no.52203211)Fundamental Research Funds for the Central Universities,China(grant no.2024CDJZCQ-005)Exceptional Young Talents Project(grant no.cstc2021ycjh-bgzxm0334)Financial support(grant no.IDH2203003Y)from Fudan University。
文摘Ionic thermoelectricity(i-TE),as a new energy conversion and storage technology,has been widely discussed by the academic community.As one of the representatives of low-grade thermal energy recovery,i-TE has made remarkable progress and become an influential research direction in the energy field.Among them,thermoelectric ionogels have a wide range of applications in the field of energy recovery and utilization due to their excellent flexibility,stability,and thermoelectric conversion ability,providing many application possibilities for such materials.The development of highly efficient and stable ionic thermoelectric devices is largely dependent on the development of new materials and structural designs.This paper focuses on the recent strategies for improving the efficiency of thermoelectric conversion in the field of ionic thermoelectric gels,including new methods for material design,structural optimization,and innovative developments in the application of thermoelectric materials.The evaluation indicators of thermoelectric conversion efficiency are discussed,including ionic thermal voltage,ionic conductivity and power output,ductility,and self-healing properties.Additionally,various application devices based on thermoelectric materials with excellent thermoelectric conversion properties are highlighted.Further,different challenges and strategies that need to be addressed are presented in the hope of providing inspiration and guidance for the commercialization of i-TE.
基金This work was supported by a National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)[grant number 2020R1A2C2010413]Korea Research Council[grant number NRF-2021K1A3A1A74095929]+1 种基金KIST project[grant number 2E31641]KU-KIST Graduate School of Converging Science and Technology Program.
文摘During the past decade,there has been extensive research toward the possibility of exploring magnesium and its alloys as biocompatible and biodegradable materials for implantable applications.Its practical medical application,however,has been limited to specific areas owing to rapid corrosion in the initial stage and the consequent complications.Surface coatings can significantly reduce the initial corrosion of Mg alloys,and several studies have been carried out to improve the adhesion strength of the coating to the surfaces of the alloys.The composition of hydroxyapatite(HAp)is very similar to that of bone tissue;it is one of the most commonly used coating materials for bone-related implants owing to favorable osseointegration post-implantation.In this study,HAp was coated on Mg using nanosecond laser coating,combining the advantages of chemical and physical treatments.Photothermal heat generated in the liquid precursor by the laser improved the adhesion of the coating through the precipitation and growth of HAp at the localized nanosecond laser focal area and increased the corrosion resistance and cell adhesion of Mg.The physical,crystallographic,and chemical bondings were analyzed to explore the mechanism through which the surface adhesion between Mg and the HAp coating layer increased.The applicability of the coating to Mg screws used for clinical devices and improvement in its corrosion property were confirmed.The liquid environment-based laser surface coating technique offers a simple and quick process that does not require any chemical ligands,and therefore,overcomes a potential obstacle in its clinical use.
