Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean...Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.展开更多
In this study,?a 2-D MHD free convection incompressible electrically induced boundary layer analysis on a water/nano-fluidic mixture. The ODE solution is numerically analyzed with a Runge-Kutta model as the thermophys...In this study,?a 2-D MHD free convection incompressible electrically induced boundary layer analysis on a water/nano-fluidic mixture. The ODE solution is numerically analyzed with a Runge-Kutta model as the thermophysical properties on a magnetic variation as well as temperature ranges of buoyancy effects on the T and V profiles and the wall force friction on the flow is also studied. The temperature and velocity gradients have a significant differential change is been observed in this study.展开更多
The present study discusses the thermal performance of the receiver tube,which contains a wall with various fin shapes in the parabolic trough collector.Inserted fins and bulge surfaces of the inner wall of the receiv...The present study discusses the thermal performance of the receiver tube,which contains a wall with various fin shapes in the parabolic trough collector.Inserted fins and bulge surfaces of the inner wall of the receiver tube increase the turbulent fluid flow.In pursuance of uniform distribution of heat transfer,various fin shapes such as square-shape,circle-shape,triangle-shape,and combined square-circle shapes were inserted,examined,and compared.A study of the temperature differences and fluid flow is meaningful for this project therefore finite volume method was used to investigate heat transfer.Also,hybrid Nano-Fluid AL_(2)O_(3-)CuO,TiO_(2-)Cu,and AgMgO were applied to increase thermal diffusivity.When the combined square-circle-shaped fin was inserted,the thermal peak of fluid flow in the receiver tube was lower than the other studied fin shapes by almost 1%.Besides,the hybrid nano-fluid Ag-MgO Syltherm-oil-800 has lower thermal waste in comparison to others by more than 3%.展开更多
In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the move...In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.展开更多
The torsional characteristics of single walled carbon nanotube(SWCNT) with water interactions are studied in this work using molecular dynamics simulation method. The torsional properties of carbon nanotubes(CNTs) in ...The torsional characteristics of single walled carbon nanotube(SWCNT) with water interactions are studied in this work using molecular dynamics simulation method. The torsional properties of carbon nanotubes(CNTs) in a hydrodynamic environment such as water are critical for its key role in determining the lifetime and stability of CNT based nano-fluidic devices. The effect of chirality, defects and the density of water encapsulation is studied by subjecting the SWCNT to torsion. The findings show that the torsional strength of SWCNT decreases due to interaction of water molecules and presence of defects in the SWCNT. Additionally,for the case of water molecules encapsulated inside SWCNT, the torsional response depends on the density of packing of water molecules. Our findings and conclusions obtained from this paper is expected to further compliment the potential applications of CNTs as promising candidates for applications in nano-biological and nano-fluidic devices.展开更多
Biodiesel obtained from mustard seed is found to be a promising alternative for petroleum diesel fuel owing to its similarity in physical and chemical properties. In this work, TiO2nano-fluid which acts as an oxygen b...Biodiesel obtained from mustard seed is found to be a promising alternative for petroleum diesel fuel owing to its similarity in physical and chemical properties. In this work, TiO2nano-fluid which acts as an oxygen buffer during combustion was added to mustard oil biodiesel(MOBD) to study its effect on emission characteristics of MOBD. TiO2nano-fluid can provide high surface energy during the course of combustion and reduces the limitations of neat biodiesel. A four-stroke, multi-cylinder,water-cooled, diesel engine was used in the experiments and was fueled with diesel, neat MOBD and MOBD with TiO2nanoparticles at 100 ppm(MOBDT100), 200 ppm(MOBDT200) and 300 ppm(MOBDT300). Experimental results revealed that the TiO2nanoparticles had positive effect on the emission characteristics of MOBD as it acted as an oxidation buffer. MOBDT300 showed a reduction in HC, CO and smoke emissions as compared to pure MOBD.In addition, NOxemissions were also reduced by the catalytic activity of the TiO2nanoparticles which reduce the peak combustion temperature. Therefore, TiO2nano-fluid had a positive effect on reducing the emissions associated with neat biodiesel.展开更多
Currently,nanofluid is a hot area of interest for researchers.The nanofluid with bioconvection phenomenon attracted the researchers owing to its numerous applications in the field of nanotechnology,microbiology,nuclea...Currently,nanofluid is a hot area of interest for researchers.The nanofluid with bioconvection phenomenon attracted the researchers owing to its numerous applications in the field of nanotechnology,microbiology,nuclear science,heat storage devices,biosensors,biotechnology,hydrogen bomb,engine of motors,cancer treatment,the atomic reactor,cooling of devices,and in many more.This article presents the bioconvection cross-diffusion effects on the magnetohydrodynamic flow of nanofluids on three different geometries(cone,wedge,and plate)with mixed convection.The temperature-dependent thermal conductivity,thermal diffusivity,and Arrhenius activation energy applications are considered on the fluid flow with melting phenomenon.The flow is analyzed under thermal and solutal Robin’s conditions.The problem is formulated in the mathematical formulation of partial differential equations(PDEs).The similarity transformations are applied to diminish the governing nonlinear coupled boundary value problems into higher-order non-linear ordinary differential equations(ODEs).The resulting expressions/equation numerically tackled utilizing the famous bvp4c package by MATLAB for various interesting parameters.The results were physically and numerically calculated through graphics and tables for the velocity field,energy distribution,nanoparticles concentration,and microorganisms profile for numerous parameters.From the obtained results,we discern that the transfer of heat and mass coefficient is high over a plate and cone in the flow,respectively.The velocity profile is reduced via a larger magnetic parameter.Temperaturedependent thermal conductivity enhances the thermal field.Larger thermophoresis enhanced the concentration of nanoparticles.The microorganisms’Biot number boosts the microorganism’s profile.展开更多
Recent studies carried out in terms of viscous flow and heat transfer of nano-fluids on the non-linear sheets. In this paper, detailed studies to understand the characteristics such as viscous flow and heat transfer o...Recent studies carried out in terms of viscous flow and heat transfer of nano-fluids on the non-linear sheets. In this paper, detailed studies to understand the characteristics such as viscous flow and heat transfer of nano-fluids under the influence of thermal radiation and magnetic fields are studied using Keller-Box method. Various governing parameters affecting the viscous flow and heat transfers are drawn based on quantitative results. The raise in temperature affected the velocity to a negative value;however, the same observation was made even for the increasing magnetic field. The impact of radiation parameter is proportional seems to be proportional to temperature and it is observed to be inversely proportional with concentration.展开更多
Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due...Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due to their outstanding thermal characteristics.In this work,the published investigations on the preparation and characterization of nano-fluids have been discussed at first.Furthermore,the key thermo-physical properties of nano-fluids,such as thermal conductivity,viscosity,specific heat and density have been summarized.Finally,the performance enhancements in different types of refrigeration systems by using nano-fluids have been reviewed.It is concluded that nano-fluids as refrigerant,lubricant or secondary fluid have wide potential application in refrigeration systems.展开更多
An analytical approximation for the similarity solutions of the two-and three-dimensional stagnation slip flow and heat transfer is obtained by using the homotopy analysis method. This method is a series expansion met...An analytical approximation for the similarity solutions of the two-and three-dimensional stagnation slip flow and heat transfer is obtained by using the homotopy analysis method. This method is a series expansion method, but it is different from the perturbation technique, because it is independent of small physical parameters at all. Instead, it is based on a continuous mapping in topology so that it is applicable for not only weakly but also strongly nonlinear flow phenomena. Convergent [m,m] homotopy Padé approximants are obtained and compared with the numerical results and the asymptotic approximations. It is found that the homotopy Padé approximants agree well with the numerical results. The effects of the slip length and the thermal slip constant β on the heat transfer characteristics are investigated and discussed.展开更多
基金Project supported by the Fundamental Research Fund for the Central Universities of Chinathe Research Project for Independently Cultivate Talents of Hebei Agricultural University (Grant No.ZY2023007)。
文摘Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.
文摘In this study,?a 2-D MHD free convection incompressible electrically induced boundary layer analysis on a water/nano-fluidic mixture. The ODE solution is numerically analyzed with a Runge-Kutta model as the thermophysical properties on a magnetic variation as well as temperature ranges of buoyancy effects on the T and V profiles and the wall force friction on the flow is also studied. The temperature and velocity gradients have a significant differential change is been observed in this study.
文摘The present study discusses the thermal performance of the receiver tube,which contains a wall with various fin shapes in the parabolic trough collector.Inserted fins and bulge surfaces of the inner wall of the receiver tube increase the turbulent fluid flow.In pursuance of uniform distribution of heat transfer,various fin shapes such as square-shape,circle-shape,triangle-shape,and combined square-circle shapes were inserted,examined,and compared.A study of the temperature differences and fluid flow is meaningful for this project therefore finite volume method was used to investigate heat transfer.Also,hybrid Nano-Fluid AL_(2)O_(3-)CuO,TiO_(2-)Cu,and AgMgO were applied to increase thermal diffusivity.When the combined square-circle-shaped fin was inserted,the thermal peak of fluid flow in the receiver tube was lower than the other studied fin shapes by almost 1%.Besides,the hybrid nano-fluid Ag-MgO Syltherm-oil-800 has lower thermal waste in comparison to others by more than 3%.
基金supported by the National Natural Science Foundation of China(Grant Nos.61378083 and 11672229)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+2 种基金the Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110,14JS106,14JS107,and 2013SZS03-Z01)the Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project(Grant No.2016ZDJC-15)
文摘In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate and analyze the characteristics of single bio-molecules. To accurately and flexibly control the movement of single molecule within micro-/submicro-fluidic channels, the characteristics of current signals at the initial stage of the flow are systematically studied based on a three-electrode system. The current response of micro-/submicro-fluidic channels filled with different electrolyte solutions in non-continuous external electric field are investigated. It is found, there always exists a current reversal phenomenon, which is an inherent property of the current signals in micro/submicro-fluidics Each solution has an individual critical voltage under which the steady current value is equal to zero The interaction between the steady current and external applied voltage follows an exponential function. All these results can be attributed to the overpotentials of the electric double layer on the electrodes. These results are helpful for the design and fabrication of functional micro/nano-scale fluidic sensors and biochips.
文摘The torsional characteristics of single walled carbon nanotube(SWCNT) with water interactions are studied in this work using molecular dynamics simulation method. The torsional properties of carbon nanotubes(CNTs) in a hydrodynamic environment such as water are critical for its key role in determining the lifetime and stability of CNT based nano-fluidic devices. The effect of chirality, defects and the density of water encapsulation is studied by subjecting the SWCNT to torsion. The findings show that the torsional strength of SWCNT decreases due to interaction of water molecules and presence of defects in the SWCNT. Additionally,for the case of water molecules encapsulated inside SWCNT, the torsional response depends on the density of packing of water molecules. Our findings and conclusions obtained from this paper is expected to further compliment the potential applications of CNTs as promising candidates for applications in nano-biological and nano-fluidic devices.
文摘Biodiesel obtained from mustard seed is found to be a promising alternative for petroleum diesel fuel owing to its similarity in physical and chemical properties. In this work, TiO2nano-fluid which acts as an oxygen buffer during combustion was added to mustard oil biodiesel(MOBD) to study its effect on emission characteristics of MOBD. TiO2nano-fluid can provide high surface energy during the course of combustion and reduces the limitations of neat biodiesel. A four-stroke, multi-cylinder,water-cooled, diesel engine was used in the experiments and was fueled with diesel, neat MOBD and MOBD with TiO2nanoparticles at 100 ppm(MOBDT100), 200 ppm(MOBDT200) and 300 ppm(MOBDT300). Experimental results revealed that the TiO2nanoparticles had positive effect on the emission characteristics of MOBD as it acted as an oxidation buffer. MOBDT300 showed a reduction in HC, CO and smoke emissions as compared to pure MOBD.In addition, NOxemissions were also reduced by the catalytic activity of the TiO2nanoparticles which reduce the peak combustion temperature. Therefore, TiO2nano-fluid had a positive effect on reducing the emissions associated with neat biodiesel.
基金This work is financially supported by the Government College University,Faisalabad and Higher Education Commission,Pakistan.
文摘Currently,nanofluid is a hot area of interest for researchers.The nanofluid with bioconvection phenomenon attracted the researchers owing to its numerous applications in the field of nanotechnology,microbiology,nuclear science,heat storage devices,biosensors,biotechnology,hydrogen bomb,engine of motors,cancer treatment,the atomic reactor,cooling of devices,and in many more.This article presents the bioconvection cross-diffusion effects on the magnetohydrodynamic flow of nanofluids on three different geometries(cone,wedge,and plate)with mixed convection.The temperature-dependent thermal conductivity,thermal diffusivity,and Arrhenius activation energy applications are considered on the fluid flow with melting phenomenon.The flow is analyzed under thermal and solutal Robin’s conditions.The problem is formulated in the mathematical formulation of partial differential equations(PDEs).The similarity transformations are applied to diminish the governing nonlinear coupled boundary value problems into higher-order non-linear ordinary differential equations(ODEs).The resulting expressions/equation numerically tackled utilizing the famous bvp4c package by MATLAB for various interesting parameters.The results were physically and numerically calculated through graphics and tables for the velocity field,energy distribution,nanoparticles concentration,and microorganisms profile for numerous parameters.From the obtained results,we discern that the transfer of heat and mass coefficient is high over a plate and cone in the flow,respectively.The velocity profile is reduced via a larger magnetic parameter.Temperaturedependent thermal conductivity enhances the thermal field.Larger thermophoresis enhanced the concentration of nanoparticles.The microorganisms’Biot number boosts the microorganism’s profile.
文摘Recent studies carried out in terms of viscous flow and heat transfer of nano-fluids on the non-linear sheets. In this paper, detailed studies to understand the characteristics such as viscous flow and heat transfer of nano-fluids under the influence of thermal radiation and magnetic fields are studied using Keller-Box method. Various governing parameters affecting the viscous flow and heat transfers are drawn based on quantitative results. The raise in temperature affected the velocity to a negative value;however, the same observation was made even for the increasing magnetic field. The impact of radiation parameter is proportional seems to be proportional to temperature and it is observed to be inversely proportional with concentration.
基金National Natural Science Foundation of China(No.51906013)The Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture,China(JDYC20200316)。
文摘Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due to their outstanding thermal characteristics.In this work,the published investigations on the preparation and characterization of nano-fluids have been discussed at first.Furthermore,the key thermo-physical properties of nano-fluids,such as thermal conductivity,viscosity,specific heat and density have been summarized.Finally,the performance enhancements in different types of refrigeration systems by using nano-fluids have been reviewed.It is concluded that nano-fluids as refrigerant,lubricant or secondary fluid have wide potential application in refrigeration systems.
基金Supported by the National Natural Science Foundation of China (Grant No.10872129)
文摘An analytical approximation for the similarity solutions of the two-and three-dimensional stagnation slip flow and heat transfer is obtained by using the homotopy analysis method. This method is a series expansion method, but it is different from the perturbation technique, because it is independent of small physical parameters at all. Instead, it is based on a continuous mapping in topology so that it is applicable for not only weakly but also strongly nonlinear flow phenomena. Convergent [m,m] homotopy Padé approximants are obtained and compared with the numerical results and the asymptotic approximations. It is found that the homotopy Padé approximants agree well with the numerical results. The effects of the slip length and the thermal slip constant β on the heat transfer characteristics are investigated and discussed.
