Ping Cheng | Shanghai Jiao Tong University (original) (raw)
Papers by Ping Cheng
International Journal of Engineering Science, 1992
... is (r )sm 0. (26) rr The tangential velocity is then given by d 1. i . v=[!+, si 3r r2) 1 + ,... more ... is (r )sm 0. (26) rr The tangential velocity is then given by d 1. i . v=[!+, si 3r r2) 1 + , sin 6 rl (27) It follows that v 2 sin 6 near the ... 4. Variation off'(r) with r. 262 I. POP and P. CHENG where R = (r 1)1 a. For the outer flow region, we have (r)=r(l+2a)+(a2) (29) Substituting equation (28 ...
International Communications in Heat and Mass Transfer, 1985
The problem of natural convection about a cone embedded in a porous medium at high Raylelgh numbe... more The problem of natural convection about a cone embedded in a porous medium at high Raylelgh numbers is analyzed based on the boundary layer approximation and the Darcy's law. Local similarity solutions are obtained for a truncated cone with the prescribed wall temperature or surface heat flux being a power function of distance from the leading edge. It is shown that at a location near the leading edge, the solution behaves like that of an incllned plate. At a location far downstream of the truncated cone, the solution approaches that of a full cone where similarity solutions exist.
Fluid Dynamics Research, 1993
... Pop et ai, Transient free convection composite tangential velocity are therefore given by V/,... more ... Pop et ai, Transient free convection composite tangential velocity are therefore given by V/, = - 2(r*/Ra)1 '2 ( ?y erfc W - e "2 ) sin 0 - ^f^/Ras'-n-(- \ V'Tt ,./ - 2(r*/7tRa/2i'I" - + (r*/Ra)((i+ 3^2)erfc(^- ^.c "^sin^ -(?*Ra)1 ^(( -^lf^^)erfc(^7 -:--(i+ 8^)e "'')sin^ ' 3 ^ Tt / + =(f*/Ra)3'-' M"- + i ...
Journal of Micromechanics and Microengineering, 2012
Sessile droplet oscillations in electrowetting on dielectric with a coplanar-electrode configurat... more Sessile droplet oscillations in electrowetting on dielectric with a coplanar-electrode configuration are studied experimentally under the actuation of ac voltage with different frequencies. It was found that the experimental resonance frequencies and the number of lobes at different resonance modes agree reasonably well with a previous linear analysis. Oscillations of contact width and droplet height are in-phase at resonance modes
Journal of Heat Transfer, 2005
The objective of this review is to provide a summary of modeling and experimental research effort... more The objective of this review is to provide a summary of modeling and experimental research efforts on transport phenomena in proton exchange membrane fuel cells (PEMFCs). Several representative PEMFC models and experimental studies in macro and micro PEMFCs are selected for discussion. No attempt is made to examine all the models or experimental studies, but rather the focus is to elucidate the macro-homogeneous modeling methodologies and representative experimental results. Since the transport phenomena are different in different regions of a fuel cell, fundamental phenomena in each region are first reviewed. This is followed by the presentation of various theoretical models on these transport processes in PEMFCs. Finally, experimental investigation on the cell performance of macro and micro PEMFC and DMFC is briefly presented.
International Journal of Heat and Mass Transfer, 2013
EHD effects on bubble nucleation and its subsequent growth dynamic on a small heater in pool boil... more EHD effects on bubble nucleation and its subsequent growth dynamic on a small heater in pool boiling of R113 are investigated experimentally in this paper. The small heater, 5 mm  5 mm in size, is made of an ITO film consisting of Pyrex glass and ITO-coatings. A non-uniform electric field is generated by a vertical needle at high potential and the small heater at low potential as electrodes. A high-speed camera is used to record the changing shape of a single R113 vapor bubble during its nucleation and its subsequent rise from the small heater at different heat fluxes with and without an externally imposed electric field. Effects of electric field strength and imposed heat flux on the bubble growth time, waiting time, departure frequency, dynamic contact angle and movement of triple contact line are presented. It is found that the electric field enhances nucleate boiling heat transfer of a single R113 bubble in the present experiment.
International Journal of Heat and Mass Transfer, 2020
Boiling is a ubiquitous process in many applications including power generation, desalination, an... more Boiling is a ubiquitous process in many applications including power generation, desalination, and high-heat flux electronic cooling. At the same time, boiling is a complicated physical process involving hydrodynamics and interfacial heat and mass transfer on multiple scales. One of the key limiting factors of boiling is the critical heat flux (CHF), beyond which a vapor blanket forms on the heating surface and catastrophic device burnout occurs. Yet, detailed understanding of the mechanism that triggers CHF remains elusive. In this paper, we elucidate the CHF mechanism by studying the evolution of wet/dry region on the heater surface using lattice Boltzmann simulations. We incorporate the equation of state for real gases in the liquid-vapor phase change model for direct numerical simulation of the CHF phenomenon. The results of this framework clarify the difference between the triggering mechanism of CHF and film boiling by analyzing the pool boiling curve. We demonstrate that the heat flux of the wet region on the heater surface increases while the wet area fraction decreases with superheat, leading to the CHF. We show that a vapor recoil force due to the interfacial heat and mass transfer plays an important role for the evolution of wet area fraction and therefore contributes to the occurrence of a second transition regime and CHF. Compared with previous CHF models which treat CHF as an isolated point on the boiling curve, this work elucidates the triggering mechanism of CHF from a perspective of the dynamic evolution of the wet/dry region with increasing superheat, which could potentially serve as a guideline for future CHF enhancement designs.
Research, 2020
Conductive hydrogels with high stretchability can extend their applications as a flexible electro... more Conductive hydrogels with high stretchability can extend their applications as a flexible electrode in electronics, biomedicine, human-machine interfaces, and sensors. However, their time-consuming fabrication and narrow ranges of working temperature and working voltage severely limit their further potential applications. Herein, a conductive nanocomposite network hydrogel fabricated by projection microstereolithography (P μ SL) based 3D printing is proposed, enabling fast fabrication ability with high precision. The 3D printed hydrogels exhibit ultra-stretchability (2500%), hyper-antifreezing (-125°C), extremely low working voltage (<100 μ V), and super cyclic tensile stability (1 million cycles). The hydrogel-based strain sensor can probe both large-scale and tiny human motions, even with ultralow voltage of 100 μ V at extremely low temperature around −115°C. It is demonstrated that the present hydrogels can be used as a flexible electrode for capturing human electrophysiolog...
Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental i... more Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental interest for a number of engineering applications. Examples include thermal technologies for remediation of contaminated subsurfaces, the extraction of geothermal energy from vapor-dominated reservoirs, and the assessment of high-level nuclear waste repositories. A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while th...
1st International Conference on Microchannels and Minichannels
A simultaneous visualization and measurement study has been carried out to investigate flow boili... more A simultaneous visualization and measurement study has been carried out to investigate flow boiling of water in the 8 parallel silicon microchannels heated from below. It is found that there are two large-amplitude/long-period oscillating boiling modes exist in microchannels depending on the amounts of heat flux and mass flux. When the outlet water temperature is at saturation temperature and the wall temperatures are superheated, while the inlet water temperature is still subcooled, a Liquid/Two-phase Alternating Flow (LTAF) mode appears in the microchannels. This LTAF mode disappears when the inlet temperatures reaches the saturation temperature. As the heat flux is further increased such that the outlet water is superheated while the inlet water temperature is oscillating between subcooled and saturation temperature, a Liquid/Two-phase/Vapor Alternating Flow (LTVAF) mode begins. During these two unstable boiling modes, there are large-amplitude and long-period oscillations of wat...
Nanostructured Materials for Next-Generation Energy Storage and Conversion, 2019
A perfect absorber, with pyramidal nanostructures made of a natural hyperbolic material, for sola... more A perfect absorber, with pyramidal nanostructures made of a natural hyperbolic material, for solar energy harvesting is proposed in this chapter. A numerical investigation is first carried out for regularly arranged bismuth telluride (Bi2Te3, an anisotropic and natural hyperbolic material) pyramidal nanostructures placed on top of a Ag substrate, and the metamaterial is submerged in water. The calculated results show that the absorptance of the absorber exceeds 99.9% in the wavelength range of 300–2400 nm. The underlying mechanisms are revealed by the electric field and power dissipation density distribution in the absorber. It is found that the slow light effect in the type-II hyperbolic region (300–1000 nm) and the gradient index effect in the long wavelength range (1000–2400 nm) contribute to the perfect absorption of the solar energy for the proposed absorber. Effects of geometry parameters of nano-pyramids and the substrate on optical properties of the proposed absorber are illustrated. In addition, a rough surface with sharp nanostructures made of Bi2Te3 is also numerically studied. Based on simulation results of rough Bi2Te3 surface, samples with nanostructures made of Bi2Te3 are experimentally manufactured and optical properties of the samples are measured by using an integrating sphere with a grating monochromator. The absorptance of the samples can be as high as 97.5%, and the lowest absorptance of the sample is still higher than 94% in the wavelength range of 380–1800 nm. Moreover, other samples are also fabricated and studied to validate underlying mechanisms of the perfect absorption of solar energy. The results of the present study open a new revenue for effectively harvesting solar energy by using metamaterials with nanostructures made of natural hyperbolic materials submerged in water.
Advanced Photonics 2017 (IPR, NOMA, Sensors, Networks, SPPCom, PS), 2017
A numerical study has been carried out on optical properties of an absorber made of a natural ani... more A numerical study has been carried out on optical properties of an absorber made of a natural anisotropic hyperbolic material, subject to normally incident light. The proposed absorber, consisting of an array of pyramidal nanostructures, made from bismuth telluride (Bi2Te3, a hyperbolic medium) on the top of a smooth substrate, is submerged in water. The designed absorber was numerically studied by using finite-difference time-domain (FDTD) method and rigorous coupled-wave analysis (RCWA) method. Numerical results show that such an absorber has a perfect absorptance for solar energy in a broadband wavelength range of 300 - 2400 nm by combining the slow-light effect and gradient index effect together. The unique optical property of such absorber contributes to the potential application in solar energy harvesting.
Advances in Heat Transfer, 2006
... in conventional channels, meso (mini) heat exchangers are more compact and lighter in weight ... more ... in conventional channels, meso (mini) heat exchangers are more compact and lighter in weight for a ... The quality of the print depends on the size of the drops and drop velocity ... low-temperature heat pipes because of its compatibility with water and other low-temperature working ...
Chinese Journal of Chromatography, 2007
Sample stacking in capillary electrophoresis is one of the effective techniques to concentrate sa... more Sample stacking in capillary electrophoresis is one of the effective techniques to concentrate sample species, thus improving the detection sensitivity. A 1 -D mathematical model, including the electrical potential distribution equation, the buffer concentration equation, as well as the sample electromigration and diffusion equation, is developed through proper simplifications and assumptions to study the sample stacking process in capillary electrophoresis. These coupled governing equations are solved using finite element method (FEM). The variations of the buffer concentration and the electrical field strenthe distribution with time as well as the electrical potential distribution in capillary during sample stacking are obtained. The sample stacking and the sample diffusion after stacking as well as the separation process of sample cations and anions are presented. It is found that the best stacking effect occurs near the entrance where the species have not been separated well. With the development of time, the stacking effect deteriorates while the distance between the positively and negatively charged particles becomes larger, and the separation effect becomes better. The effect of buffer concentration ratio on sample stacking is also analyzed. It is found that the relationship between sample stacking effect and the buffer concentration ratio is not linear and the maximum stacking effect is achieved within less time and migration distance when the buffer concentration ratio is higher because of the stronger electrical field strength in sample plug region. It is anticipated that the numerical model developed in this paper is helpful for the design and optimization of sample stacking devices.
Journal of Heat Transfer, 2017
Results of lattice Boltzmann (LB) simulations of macroscale effects (heating modes, heater size, ... more Results of lattice Boltzmann (LB) simulations of macroscale effects (heating modes, heater size, and saturation temperature) as well as microscale effects (wettability and roughness) on saturated pool boiling from superheated horizontal surfaces are summarized in this paper. These effects on pool boiling curves from natural convection through nucleate boiling to critical heat flux (CHF) and from transition boiling to film boiling are illustrated. It is found that macroscale effects have negligible influence on nucleate boiling heat transfer, and Rohsenow's correlation equation fits well with the simulated nucleate boiling heat transfer on smooth hydrophilic and hydrophobic horizontal surfaces. Both macroscale and microscale effects have important influence on critical heat flux and transition boiling heat transfer.
AIP Conference Proceedings, 2007
Recent visualization and measurements results on flow boiling of water and condensation of steam ... more Recent visualization and measurements results on flow boiling of water and condensation of steam in a single microchannel, carried out at Shanghai Jiaotong University, is summarized in this paper. For flow boiling of water, experiments were conducted in a single microchannel with a trapezoidal cross-section having a hydraulic diameter of 186 mum and a length of 30 mm. A boiling
Heat Transfer: Volume 3, 2003
ABSTRACT
International Journal of Engineering Science, 1992
... is (r )sm 0. (26) rr The tangential velocity is then given by d 1. i . v=[!+, si 3r r2) 1 + ,... more ... is (r )sm 0. (26) rr The tangential velocity is then given by d 1. i . v=[!+, si 3r r2) 1 + , sin 6 rl (27) It follows that v 2 sin 6 near the ... 4. Variation off'(r) with r. 262 I. POP and P. CHENG where R = (r 1)1 a. For the outer flow region, we have (r)=r(l+2a)+(a2) (29) Substituting equation (28 ...
International Communications in Heat and Mass Transfer, 1985
The problem of natural convection about a cone embedded in a porous medium at high Raylelgh numbe... more The problem of natural convection about a cone embedded in a porous medium at high Raylelgh numbers is analyzed based on the boundary layer approximation and the Darcy's law. Local similarity solutions are obtained for a truncated cone with the prescribed wall temperature or surface heat flux being a power function of distance from the leading edge. It is shown that at a location near the leading edge, the solution behaves like that of an incllned plate. At a location far downstream of the truncated cone, the solution approaches that of a full cone where similarity solutions exist.
Fluid Dynamics Research, 1993
... Pop et ai, Transient free convection composite tangential velocity are therefore given by V/,... more ... Pop et ai, Transient free convection composite tangential velocity are therefore given by V/, = - 2(r*/Ra)1 '2 ( ?y erfc W - e "2 ) sin 0 - ^f^/Ras'-n-(- \ V'Tt ,./ - 2(r*/7tRa/2i'I" - + (r*/Ra)((i+ 3^2)erfc(^- ^.c "^sin^ -(?*Ra)1 ^(( -^lf^^)erfc(^7 -:--(i+ 8^)e "'')sin^ ' 3 ^ Tt / + =(f*/Ra)3'-' M"- + i ...
Journal of Micromechanics and Microengineering, 2012
Sessile droplet oscillations in electrowetting on dielectric with a coplanar-electrode configurat... more Sessile droplet oscillations in electrowetting on dielectric with a coplanar-electrode configuration are studied experimentally under the actuation of ac voltage with different frequencies. It was found that the experimental resonance frequencies and the number of lobes at different resonance modes agree reasonably well with a previous linear analysis. Oscillations of contact width and droplet height are in-phase at resonance modes
Journal of Heat Transfer, 2005
The objective of this review is to provide a summary of modeling and experimental research effort... more The objective of this review is to provide a summary of modeling and experimental research efforts on transport phenomena in proton exchange membrane fuel cells (PEMFCs). Several representative PEMFC models and experimental studies in macro and micro PEMFCs are selected for discussion. No attempt is made to examine all the models or experimental studies, but rather the focus is to elucidate the macro-homogeneous modeling methodologies and representative experimental results. Since the transport phenomena are different in different regions of a fuel cell, fundamental phenomena in each region are first reviewed. This is followed by the presentation of various theoretical models on these transport processes in PEMFCs. Finally, experimental investigation on the cell performance of macro and micro PEMFC and DMFC is briefly presented.
International Journal of Heat and Mass Transfer, 2013
EHD effects on bubble nucleation and its subsequent growth dynamic on a small heater in pool boil... more EHD effects on bubble nucleation and its subsequent growth dynamic on a small heater in pool boiling of R113 are investigated experimentally in this paper. The small heater, 5 mm  5 mm in size, is made of an ITO film consisting of Pyrex glass and ITO-coatings. A non-uniform electric field is generated by a vertical needle at high potential and the small heater at low potential as electrodes. A high-speed camera is used to record the changing shape of a single R113 vapor bubble during its nucleation and its subsequent rise from the small heater at different heat fluxes with and without an externally imposed electric field. Effects of electric field strength and imposed heat flux on the bubble growth time, waiting time, departure frequency, dynamic contact angle and movement of triple contact line are presented. It is found that the electric field enhances nucleate boiling heat transfer of a single R113 bubble in the present experiment.
International Journal of Heat and Mass Transfer, 2020
Boiling is a ubiquitous process in many applications including power generation, desalination, an... more Boiling is a ubiquitous process in many applications including power generation, desalination, and high-heat flux electronic cooling. At the same time, boiling is a complicated physical process involving hydrodynamics and interfacial heat and mass transfer on multiple scales. One of the key limiting factors of boiling is the critical heat flux (CHF), beyond which a vapor blanket forms on the heating surface and catastrophic device burnout occurs. Yet, detailed understanding of the mechanism that triggers CHF remains elusive. In this paper, we elucidate the CHF mechanism by studying the evolution of wet/dry region on the heater surface using lattice Boltzmann simulations. We incorporate the equation of state for real gases in the liquid-vapor phase change model for direct numerical simulation of the CHF phenomenon. The results of this framework clarify the difference between the triggering mechanism of CHF and film boiling by analyzing the pool boiling curve. We demonstrate that the heat flux of the wet region on the heater surface increases while the wet area fraction decreases with superheat, leading to the CHF. We show that a vapor recoil force due to the interfacial heat and mass transfer plays an important role for the evolution of wet area fraction and therefore contributes to the occurrence of a second transition regime and CHF. Compared with previous CHF models which treat CHF as an isolated point on the boiling curve, this work elucidates the triggering mechanism of CHF from a perspective of the dynamic evolution of the wet/dry region with increasing superheat, which could potentially serve as a guideline for future CHF enhancement designs.
Research, 2020
Conductive hydrogels with high stretchability can extend their applications as a flexible electro... more Conductive hydrogels with high stretchability can extend their applications as a flexible electrode in electronics, biomedicine, human-machine interfaces, and sensors. However, their time-consuming fabrication and narrow ranges of working temperature and working voltage severely limit their further potential applications. Herein, a conductive nanocomposite network hydrogel fabricated by projection microstereolithography (P μ SL) based 3D printing is proposed, enabling fast fabrication ability with high precision. The 3D printed hydrogels exhibit ultra-stretchability (2500%), hyper-antifreezing (-125°C), extremely low working voltage (<100 μ V), and super cyclic tensile stability (1 million cycles). The hydrogel-based strain sensor can probe both large-scale and tiny human motions, even with ultralow voltage of 100 μ V at extremely low temperature around −115°C. It is demonstrated that the present hydrogels can be used as a flexible electrode for capturing human electrophysiolog...
Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental i... more Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental interest for a number of engineering applications. Examples include thermal technologies for remediation of contaminated subsurfaces, the extraction of geothermal energy from vapor-dominated reservoirs, and the assessment of high-level nuclear waste repositories. A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while th...
1st International Conference on Microchannels and Minichannels
A simultaneous visualization and measurement study has been carried out to investigate flow boili... more A simultaneous visualization and measurement study has been carried out to investigate flow boiling of water in the 8 parallel silicon microchannels heated from below. It is found that there are two large-amplitude/long-period oscillating boiling modes exist in microchannels depending on the amounts of heat flux and mass flux. When the outlet water temperature is at saturation temperature and the wall temperatures are superheated, while the inlet water temperature is still subcooled, a Liquid/Two-phase Alternating Flow (LTAF) mode appears in the microchannels. This LTAF mode disappears when the inlet temperatures reaches the saturation temperature. As the heat flux is further increased such that the outlet water is superheated while the inlet water temperature is oscillating between subcooled and saturation temperature, a Liquid/Two-phase/Vapor Alternating Flow (LTVAF) mode begins. During these two unstable boiling modes, there are large-amplitude and long-period oscillations of wat...
Nanostructured Materials for Next-Generation Energy Storage and Conversion, 2019
A perfect absorber, with pyramidal nanostructures made of a natural hyperbolic material, for sola... more A perfect absorber, with pyramidal nanostructures made of a natural hyperbolic material, for solar energy harvesting is proposed in this chapter. A numerical investigation is first carried out for regularly arranged bismuth telluride (Bi2Te3, an anisotropic and natural hyperbolic material) pyramidal nanostructures placed on top of a Ag substrate, and the metamaterial is submerged in water. The calculated results show that the absorptance of the absorber exceeds 99.9% in the wavelength range of 300–2400 nm. The underlying mechanisms are revealed by the electric field and power dissipation density distribution in the absorber. It is found that the slow light effect in the type-II hyperbolic region (300–1000 nm) and the gradient index effect in the long wavelength range (1000–2400 nm) contribute to the perfect absorption of the solar energy for the proposed absorber. Effects of geometry parameters of nano-pyramids and the substrate on optical properties of the proposed absorber are illustrated. In addition, a rough surface with sharp nanostructures made of Bi2Te3 is also numerically studied. Based on simulation results of rough Bi2Te3 surface, samples with nanostructures made of Bi2Te3 are experimentally manufactured and optical properties of the samples are measured by using an integrating sphere with a grating monochromator. The absorptance of the samples can be as high as 97.5%, and the lowest absorptance of the sample is still higher than 94% in the wavelength range of 380–1800 nm. Moreover, other samples are also fabricated and studied to validate underlying mechanisms of the perfect absorption of solar energy. The results of the present study open a new revenue for effectively harvesting solar energy by using metamaterials with nanostructures made of natural hyperbolic materials submerged in water.
Advanced Photonics 2017 (IPR, NOMA, Sensors, Networks, SPPCom, PS), 2017
A numerical study has been carried out on optical properties of an absorber made of a natural ani... more A numerical study has been carried out on optical properties of an absorber made of a natural anisotropic hyperbolic material, subject to normally incident light. The proposed absorber, consisting of an array of pyramidal nanostructures, made from bismuth telluride (Bi2Te3, a hyperbolic medium) on the top of a smooth substrate, is submerged in water. The designed absorber was numerically studied by using finite-difference time-domain (FDTD) method and rigorous coupled-wave analysis (RCWA) method. Numerical results show that such an absorber has a perfect absorptance for solar energy in a broadband wavelength range of 300 - 2400 nm by combining the slow-light effect and gradient index effect together. The unique optical property of such absorber contributes to the potential application in solar energy harvesting.
Advances in Heat Transfer, 2006
... in conventional channels, meso (mini) heat exchangers are more compact and lighter in weight ... more ... in conventional channels, meso (mini) heat exchangers are more compact and lighter in weight for a ... The quality of the print depends on the size of the drops and drop velocity ... low-temperature heat pipes because of its compatibility with water and other low-temperature working ...
Chinese Journal of Chromatography, 2007
Sample stacking in capillary electrophoresis is one of the effective techniques to concentrate sa... more Sample stacking in capillary electrophoresis is one of the effective techniques to concentrate sample species, thus improving the detection sensitivity. A 1 -D mathematical model, including the electrical potential distribution equation, the buffer concentration equation, as well as the sample electromigration and diffusion equation, is developed through proper simplifications and assumptions to study the sample stacking process in capillary electrophoresis. These coupled governing equations are solved using finite element method (FEM). The variations of the buffer concentration and the electrical field strenthe distribution with time as well as the electrical potential distribution in capillary during sample stacking are obtained. The sample stacking and the sample diffusion after stacking as well as the separation process of sample cations and anions are presented. It is found that the best stacking effect occurs near the entrance where the species have not been separated well. With the development of time, the stacking effect deteriorates while the distance between the positively and negatively charged particles becomes larger, and the separation effect becomes better. The effect of buffer concentration ratio on sample stacking is also analyzed. It is found that the relationship between sample stacking effect and the buffer concentration ratio is not linear and the maximum stacking effect is achieved within less time and migration distance when the buffer concentration ratio is higher because of the stronger electrical field strength in sample plug region. It is anticipated that the numerical model developed in this paper is helpful for the design and optimization of sample stacking devices.
Journal of Heat Transfer, 2017
Results of lattice Boltzmann (LB) simulations of macroscale effects (heating modes, heater size, ... more Results of lattice Boltzmann (LB) simulations of macroscale effects (heating modes, heater size, and saturation temperature) as well as microscale effects (wettability and roughness) on saturated pool boiling from superheated horizontal surfaces are summarized in this paper. These effects on pool boiling curves from natural convection through nucleate boiling to critical heat flux (CHF) and from transition boiling to film boiling are illustrated. It is found that macroscale effects have negligible influence on nucleate boiling heat transfer, and Rohsenow's correlation equation fits well with the simulated nucleate boiling heat transfer on smooth hydrophilic and hydrophobic horizontal surfaces. Both macroscale and microscale effects have important influence on critical heat flux and transition boiling heat transfer.
AIP Conference Proceedings, 2007
Recent visualization and measurements results on flow boiling of water and condensation of steam ... more Recent visualization and measurements results on flow boiling of water and condensation of steam in a single microchannel, carried out at Shanghai Jiaotong University, is summarized in this paper. For flow boiling of water, experiments were conducted in a single microchannel with a trapezoidal cross-section having a hydraulic diameter of 186 mum and a length of 30 mm. A boiling
Heat Transfer: Volume 3, 2003
ABSTRACT