In plant living tissue, water can flow across cells by different paths, through cell membranes (transcellular path) and plasmodesmata (symplastic path), or through the continuous cell walls matrix (apoplastic path). The relative contribution of these three paths in living tissue is currently unclear and could vary according to species, tissue developmental stage or physiological conditions. Experiments suggested that apoplastic water movement predominates during transpiration. The objective of this study was to investigate the hydraulic process of cellulose cell wall pathway. The effective pore diameter for water flow through the primary wall matrix is between 2 and 20nm. Inside the cell wall polymer porous, there exist hydrophilic/hydrophobic crystal surfaces based on structure anisotropic. Besides, hydrogen bonding and electrostatic interaction and van der Waals (vdW) dispersion force play an important role in water transport inside the Nano cellulose porous. Therefore, the molecular dynamics simulation was applied to reveal the molecular mechanism of surface boundary effect together with various driving force during water passing through cellulose cell wall matrix Nano channel.
{"title":"Molecular Mechanism of Water Transport Through Cellulose Cell Wall Matrix","authors":"Jiaqi Sun, Xinrong Zhang","doi":"10.1115/mnhmt2019-4031","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4031","url":null,"abstract":"\u0000 In plant living tissue, water can flow across cells by different paths, through cell membranes (transcellular path) and plasmodesmata (symplastic path), or through the continuous cell walls matrix (apoplastic path). The relative contribution of these three paths in living tissue is currently unclear and could vary according to species, tissue developmental stage or physiological conditions. Experiments suggested that apoplastic water movement predominates during transpiration. The objective of this study was to investigate the hydraulic process of cellulose cell wall pathway.\u0000 The effective pore diameter for water flow through the primary wall matrix is between 2 and 20nm. Inside the cell wall polymer porous, there exist hydrophilic/hydrophobic crystal surfaces based on structure anisotropic. Besides, hydrogen bonding and electrostatic interaction and van der Waals (vdW) dispersion force play an important role in water transport inside the Nano cellulose porous. Therefore, the molecular dynamics simulation was applied to reveal the molecular mechanism of surface boundary effect together with various driving force during water passing through cellulose cell wall matrix Nano channel.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"125 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116854631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The high-purity electron-doped manganites Sm1-xCaxMnO3 nanopowder were prepared by the solid-state reaction method, then the bulk material were obtained through granulation, molding, calcining, grinding and polishing. SCMO nanoparticles with 200 nm were obtained by the sol-gal process. The phase and surface morphology of these materials were characterized by X-ray diffraction and Scanning electron microscope and other experiments. The variable resistivity of the bulk materials were measured by two-wire method in the temperature range of 100–420K. The thermal conductivity was measured by the Laser Flash method. The results show that different doping ratios can change the phase transition temperature of the metal-insulation state. The temperature changed from 0 to 50 °C. The TMI could be regulated to room temperature. When the temperature is high than the TMI, it performs as metal state, on the contrary, it performs as an insulating state.
{"title":"Research on Thermal Properties of Insulator-Metal Transition at Room Temperature in Sm1-xCaxMnO3","authors":"Ruxia Chang, Desong Fan, Qiang Li","doi":"10.1115/mnhmt2019-3963","DOIUrl":"https://doi.org/10.1115/mnhmt2019-3963","url":null,"abstract":"\u0000 The high-purity electron-doped manganites Sm1-xCaxMnO3 nanopowder were prepared by the solid-state reaction method, then the bulk material were obtained through granulation, molding, calcining, grinding and polishing. SCMO nanoparticles with 200 nm were obtained by the sol-gal process. The phase and surface morphology of these materials were characterized by X-ray diffraction and Scanning electron microscope and other experiments. The variable resistivity of the bulk materials were measured by two-wire method in the temperature range of 100–420K. The thermal conductivity was measured by the Laser Flash method. The results show that different doping ratios can change the phase transition temperature of the metal-insulation state. The temperature changed from 0 to 50 °C. The TMI could be regulated to room temperature. When the temperature is high than the TMI, it performs as metal state, on the contrary, it performs as an insulating state.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125885503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chundong Xue, Zhong-ping Sun, Yongjiang Li, K. Qin
The emergence of microfluidic droplets offers new opportunities to advance biomedical engineering, food production, and energy storage applications. These applications always involve complex fluids exhibiting obvious non-Newtonian behavior. Droplet generation has been extensively addressed, while the complete understanding of droplet generation in non-Newtonian fluid system is still nascent. Here, we present the study of non-Newtonian droplet generation in a flow-focusing microchannel. Polyethylene oxide aqueous solutions are used as the dispersed phase, while olive oil serves as the continuous phase to induce the generation. The molecular weight of polymer is constant while the concentrations are varied from dilute to semi-dilute regimes that are rarely explored in existing studies. The main features of non-Newtonian droplet generation are first identified, after which the concentration-dependent dripping to jetting transitions are clarified. The effects of shear thinning and elasticity on droplet generation are then separately investigated. We finally propose a scaling relation to predict the primary droplet size with the satellite droplets neglected. These results can not only extend the fundamental theory of droplet microfluidics but also facilitate the practical applications.
{"title":"Non-Newtonian Droplet Generation in a Flow-Focusing Microchannel","authors":"Chundong Xue, Zhong-ping Sun, Yongjiang Li, K. Qin","doi":"10.1115/mnhmt2019-4196","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4196","url":null,"abstract":"\u0000 The emergence of microfluidic droplets offers new opportunities to advance biomedical engineering, food production, and energy storage applications. These applications always involve complex fluids exhibiting obvious non-Newtonian behavior. Droplet generation has been extensively addressed, while the complete understanding of droplet generation in non-Newtonian fluid system is still nascent. Here, we present the study of non-Newtonian droplet generation in a flow-focusing microchannel. Polyethylene oxide aqueous solutions are used as the dispersed phase, while olive oil serves as the continuous phase to induce the generation. The molecular weight of polymer is constant while the concentrations are varied from dilute to semi-dilute regimes that are rarely explored in existing studies. The main features of non-Newtonian droplet generation are first identified, after which the concentration-dependent dripping to jetting transitions are clarified. The effects of shear thinning and elasticity on droplet generation are then separately investigated. We finally propose a scaling relation to predict the primary droplet size with the satellite droplets neglected. These results can not only extend the fundamental theory of droplet microfluidics but also facilitate the practical applications.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125332199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Topological phonon polaritons (TPhPs) are highly localized edge modes that can achieve a strong confinement of electromagnetic waves and are topologically protected to be immune to impurities and disorder. In this paper, we theoretically study the topological phonon polaritons (TPhPs) in one-dimensional (1D) dimerized silicon carbide (SiC) nanoparticle (NP) chains, as an extension of the celebrated Su-Schrieffer-Heeger (SSH) model. We analytically calculate the band structure and complex Zak phase for such chains by taking all near-field and far-field interactions into account. It is found that the 1D dimerized chain supports nontrivial topological states as long as the dimeriza-tion parameter β > 0.5 and the long-range interactions are weak, although the system is non-Hermitian. By analyzing the distribution of eigenmodes and their participation ratios (PRs), we comprehensively study the effects of disorder on the band structure and midgap modes. We reveal that such TPhPs are very robust under high-degree disorders and even enhanced by the disorder. Through a finite-size scaling analysis, we show this enhancement can be attributed to Anderson localization scheme. These topological phonon polaritonic states provide an efficient interface for thermal radiation control in the mid-infrared.
{"title":"Topological Phonon Polaritons for Thermal Radiation Control","authors":"B. X. Wang, C. Y. Zhao","doi":"10.1115/mnhmt2019-4002","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4002","url":null,"abstract":"\u0000 Topological phonon polaritons (TPhPs) are highly localized edge modes that can achieve a strong confinement of electromagnetic waves and are topologically protected to be immune to impurities and disorder. In this paper, we theoretically study the topological phonon polaritons (TPhPs) in one-dimensional (1D) dimerized silicon carbide (SiC) nanoparticle (NP) chains, as an extension of the celebrated Su-Schrieffer-Heeger (SSH) model. We analytically calculate the band structure and complex Zak phase for such chains by taking all near-field and far-field interactions into account. It is found that the 1D dimerized chain supports nontrivial topological states as long as the dimeriza-tion parameter β > 0.5 and the long-range interactions are weak, although the system is non-Hermitian. By analyzing the distribution of eigenmodes and their participation ratios (PRs), we comprehensively study the effects of disorder on the band structure and midgap modes. We reveal that such TPhPs are very robust under high-degree disorders and even enhanced by the disorder. Through a finite-size scaling analysis, we show this enhancement can be attributed to Anderson localization scheme. These topological phonon polaritonic states provide an efficient interface for thermal radiation control in the mid-infrared.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"286 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122866685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrokinetic energy conversion being a promising clean energy production technology utilizes the electric double layer (EDL) in a nanochannel to convert hydrodynamic energy to electrical power. The previous research mainly focuses on the electrokinetic energy conversion in straight nanochannels. In this work, we perform a systematic investigation of electrokinetic energy conversion in a conical nanochannel. For this purpose, a multiphysical model consisting of the Planck-Nernst-Poisson equation and Navier-Stokes equation was formulated and solved numerically. Particularly, we discover various regulation effects in the electrokinetic energy conversion in conical nanochannels that the energy conversion characteristics (streaming potential, streaming current and I-V characteristics) are different for a forward pressure difference and a backward pressure difference of the same magnitude. These regulation effects are found to be caused by the conicity of channel. Then the effects of the channel conicity, applied pressure difference and the surface charge density on the performance of electrokinetic energy conversion are discussed in details. It is generally shown that the regulation effects are enhanced by increasing the conicity, pressure difference and surface charge density. The conclusions from this work can serve as important reference and guidelines for the design and operation of electrokinetic energy conversion devices.
{"title":"Electrokinetic Energy Conversion in Conical Nanochannels: Regulation Effect due to Conicity","authors":"Fang Qian, Deng Huang, Wenyao Zhang, Wenbo Li, Qiuwan Wang, Cunlu Zhao","doi":"10.1115/mnhmt2019-4132","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4132","url":null,"abstract":"\u0000 Electrokinetic energy conversion being a promising clean energy production technology utilizes the electric double layer (EDL) in a nanochannel to convert hydrodynamic energy to electrical power. The previous research mainly focuses on the electrokinetic energy conversion in straight nanochannels. In this work, we perform a systematic investigation of electrokinetic energy conversion in a conical nanochannel. For this purpose, a multiphysical model consisting of the Planck-Nernst-Poisson equation and Navier-Stokes equation was formulated and solved numerically. Particularly, we discover various regulation effects in the electrokinetic energy conversion in conical nanochannels that the energy conversion characteristics (streaming potential, streaming current and I-V characteristics) are different for a forward pressure difference and a backward pressure difference of the same magnitude. These regulation effects are found to be caused by the conicity of channel. Then the effects of the channel conicity, applied pressure difference and the surface charge density on the performance of electrokinetic energy conversion are discussed in details. It is generally shown that the regulation effects are enhanced by increasing the conicity, pressure difference and surface charge density. The conclusions from this work can serve as important reference and guidelines for the design and operation of electrokinetic energy conversion devices.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123463261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xunyan Yin, Min-li Bai, Chengzhi Hu, Jizu Lv, Yubai Li
Molecular dynamics simulation is performed to investigate the rapid boiling of nanofluid with the variation nanoparticle wettabilities above hydrophobic surface. Four fluids are selected: base fluid (fluid 1), nanofluid with nanoparticle wettability less than (fluid 2), equal tofluid 3) and greater than (fluid 4) surface wettability. It should be noted that nanoparticle is deposited on the surface in this paper. Results show that nanofluid responds rapid boiling faster than base fluid. For fluid 4, the efficiency in heat transfer is enhanced due to the improvement of surface wettability. While for fluid 2 and 3, the surface wettability is deteriorated by the depositional nanoparticle. The heat flux is strengthened, but argon temperature and evaporation number reduce, and thus fluid 2 and 3 are not beneficial for heat transfer.
{"title":"Molecular Dynamics Simulation of Boiling Behavior of Nanofluid With Various Wettability Nanoparticle on Hydrophobic Surface","authors":"Xunyan Yin, Min-li Bai, Chengzhi Hu, Jizu Lv, Yubai Li","doi":"10.1115/mnhmt2019-4164","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4164","url":null,"abstract":"\u0000 Molecular dynamics simulation is performed to investigate the rapid boiling of nanofluid with the variation nanoparticle wettabilities above hydrophobic surface. Four fluids are selected: base fluid (fluid 1), nanofluid with nanoparticle wettability less than (fluid 2), equal tofluid 3) and greater than (fluid 4) surface wettability. It should be noted that nanoparticle is deposited on the surface in this paper. Results show that nanofluid responds rapid boiling faster than base fluid. For fluid 4, the efficiency in heat transfer is enhanced due to the improvement of surface wettability. While for fluid 2 and 3, the surface wettability is deteriorated by the depositional nanoparticle. The heat flux is strengthened, but argon temperature and evaporation number reduce, and thus fluid 2 and 3 are not beneficial for heat transfer.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124462268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiang Chun, Tingting Hao, Yansong Chen, Yingjie Zheng, Xuehu Ma, Z. Lan
Droplet impact phenomena and thin liquid film flow are widespread in nature, industrial production and daily life. The spreading characteristics and temperature evolution of the liquid film after droplet impact are the key controlling factors in many industrial heat transfer processes. Constructing a thin micro-nano structured superhydrophilic surface on a metal surface is a promising approach to achieving heat transfer enhancement. Therefore, in this paper, we experimentally investigated the hydraulic characteristics and temperature distribution evolution of water droplet impact on cold superhydrophilic surface using high-speed imaging and infrared thermal imaging techniques. During the droplet spreading on superhydrophilic surface, there is an inertial-force-dominant rapid spreading regime followed by the friction-dominant slow spreading regime. It is observed that a precursor film forms in the radial direction. The results show that the droplet spreading diameter is positively correlated with the We number, increasing as the weber number becomes larger. The spreading diameter decreases as the wall temperature decreases, but the effect of temperature is not obvious compared with that of impact weber number. For temperature evolution, a low temperature center area forms at the impact center and a ring-shaped high temperature zone is observed first for droplet impact on cold superhydrophilic surfaces. Along spreading radial direction, the temperature distribution shows an uphill to downhill curve with its gradient inverted in sign near the high temperature zone. Then the high temperature ring disappears and the liquid film temperature shows a monotonically decreasing trend along the radial direction. The duration time of high temperature ring shortens with the increase of We number and decrease of wall temperature. Meanwhile, in order to reveal the reasons for the formation of special temperature distribution, CFD numerical simulation is adopted to analyze the mechanism of ring-shaped high temperature zone’s formation. CFD numerical simulation demonstrates that the temperature evolution law is in good agreement with the experiment results. The temperature distribution of high temperature ring is caused by uneven distribution of the liquid film thickness due to the superwetting properties of superhydrophilic surface. This work is of great significance for further understanding and provides new sights of the liquid film flow on superhydrophilic surface in heat transfer process. Furthermore, it has certain reference significance for the spray and heat transfer process in engineering practice.
{"title":"The Spreading Characteristics and Temperature Evolution of Droplet Impact on Cold Superhydrophilic Surface","authors":"Jiang Chun, Tingting Hao, Yansong Chen, Yingjie Zheng, Xuehu Ma, Z. Lan","doi":"10.1115/mnhmt2019-4041","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4041","url":null,"abstract":"\u0000 Droplet impact phenomena and thin liquid film flow are widespread in nature, industrial production and daily life. The spreading characteristics and temperature evolution of the liquid film after droplet impact are the key controlling factors in many industrial heat transfer processes. Constructing a thin micro-nano structured superhydrophilic surface on a metal surface is a promising approach to achieving heat transfer enhancement. Therefore, in this paper, we experimentally investigated the hydraulic characteristics and temperature distribution evolution of water droplet impact on cold superhydrophilic surface using high-speed imaging and infrared thermal imaging techniques. During the droplet spreading on superhydrophilic surface, there is an inertial-force-dominant rapid spreading regime followed by the friction-dominant slow spreading regime. It is observed that a precursor film forms in the radial direction. The results show that the droplet spreading diameter is positively correlated with the We number, increasing as the weber number becomes larger. The spreading diameter decreases as the wall temperature decreases, but the effect of temperature is not obvious compared with that of impact weber number. For temperature evolution, a low temperature center area forms at the impact center and a ring-shaped high temperature zone is observed first for droplet impact on cold superhydrophilic surfaces. Along spreading radial direction, the temperature distribution shows an uphill to downhill curve with its gradient inverted in sign near the high temperature zone. Then the high temperature ring disappears and the liquid film temperature shows a monotonically decreasing trend along the radial direction. The duration time of high temperature ring shortens with the increase of We number and decrease of wall temperature. Meanwhile, in order to reveal the reasons for the formation of special temperature distribution, CFD numerical simulation is adopted to analyze the mechanism of ring-shaped high temperature zone’s formation. CFD numerical simulation demonstrates that the temperature evolution law is in good agreement with the experiment results. The temperature distribution of high temperature ring is caused by uneven distribution of the liquid film thickness due to the superwetting properties of superhydrophilic surface. This work is of great significance for further understanding and provides new sights of the liquid film flow on superhydrophilic surface in heat transfer process. Furthermore, it has certain reference significance for the spray and heat transfer process in engineering practice.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"11 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125643403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The lab on a chip is of great value in the analytical chemistry, biology and pharmacy. So that it is very important to study the formation and control of droplet in chips. The fluid flowing under the condition of dynamic liquid film is researched innovatively in this paper. Its inspiration is derived from bionics (fish skin, etc.), which has a broad application prospect in reducing the resistance in water and weakening the heat transfer. Dynamic liquid film refers to the dynamic thin liquid layer with the hydrophilic property on the surface of wall under the pressure of outside fluid flow. The insolubility between liquid film and fluid creates a relatively stable flowing environment. In this paper, the formation and influencing factors of the droplet in the microfluidic chip are studied by the Lattice Boltzmann method (LBM), and the flow and heat transfer characteristics of fluid in microchannel is studied with microfluidic chip as the carrier under the condition of insoluble dynamic liquid film existing on the wall surface. LBM has certain advantages in boundary processing, parallel operation and tracing phase interface automatically. Using SC model of LBM (for two component flow), the process of formation and movement of the droplet in microfluidic chip are simulated numerically after verified by Laplace‘s law. The result shows that the hydrophobic characteristics between the discrete phase and the wall surface and increased flow rate of the continuous phase will decrease the droplets’ volume and increase the producing frequency. In addition, the fluid flow in the microchannel is simulated under the condition of insoluble dynamic liquid film on the wall surface. The simulation result shows that when the fluid flow rate increases, the friction loss decreases and the heat transfer capacity decreases with the existence of the liquid film. The lower the dissolution trend between fluid and liquid film is, the greater the variation trend of fluid parameters will be. By comparing the results of experiment and simulation, the consistent results are obtained.
{"title":"Study on the Flow and Heat Transfer Characteristics of Micro-Scale Droplets and Fluid on Dynamic Liquid Film Condition by Lattice Boltzmann Method","authors":"Yichao He, Yan Li, Z. Ding, Han Yuan, N. Mei","doi":"10.1115/mnhmt2019-4214","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4214","url":null,"abstract":"\u0000 The lab on a chip is of great value in the analytical chemistry, biology and pharmacy. So that it is very important to study the formation and control of droplet in chips. The fluid flowing under the condition of dynamic liquid film is researched innovatively in this paper. Its inspiration is derived from bionics (fish skin, etc.), which has a broad application prospect in reducing the resistance in water and weakening the heat transfer. Dynamic liquid film refers to the dynamic thin liquid layer with the hydrophilic property on the surface of wall under the pressure of outside fluid flow. The insolubility between liquid film and fluid creates a relatively stable flowing environment. In this paper, the formation and influencing factors of the droplet in the microfluidic chip are studied by the Lattice Boltzmann method (LBM), and the flow and heat transfer characteristics of fluid in microchannel is studied with microfluidic chip as the carrier under the condition of insoluble dynamic liquid film existing on the wall surface. LBM has certain advantages in boundary processing, parallel operation and tracing phase interface automatically. Using SC model of LBM (for two component flow), the process of formation and movement of the droplet in microfluidic chip are simulated numerically after verified by Laplace‘s law. The result shows that the hydrophobic characteristics between the discrete phase and the wall surface and increased flow rate of the continuous phase will decrease the droplets’ volume and increase the producing frequency. In addition, the fluid flow in the microchannel is simulated under the condition of insoluble dynamic liquid film on the wall surface. The simulation result shows that when the fluid flow rate increases, the friction loss decreases and the heat transfer capacity decreases with the existence of the liquid film. The lower the dissolution trend between fluid and liquid film is, the greater the variation trend of fluid parameters will be. By comparing the results of experiment and simulation, the consistent results are obtained.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122215706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Velocity slip and temperature jump at the solid-liquid interface are important phenomena in microchannel heat transfer. A comprehensive mathematical model considering both velocity slip condition and temperature jump at the solid-liquid interface is developed to understand the mechanisms of heat and mass transfer during thin-film evaporation in this paper. The model structure is established based on the lubrication theory, Clausius-Clapeyron equation and Young-Laplace equation. To better formulate the film evaporation process, three dimensionless parameters representing the effects of slip length coefficient, temperature jump and wall superheat degree respectively, are introduced in the present model. The analytical solution provides insight of film thickness and heat transfer characteristics for the evaporating thin film. It shows that as the slip length and temperature jump coefficient decrease, the length of evaporating thin film region is shortened and the location of maximum heat flux moves closer to the initial evaporating point. The effect of slip condition on heat flux is small, but the increase of temperature jump can reduce the peak heat flux significantly. Furthermore, the analysis on the three thermal resistances which are caused by temperature jump, conduction through liquid film and evaporation on liquid-vapor interface result in a better understanding for effective heat transfer during thin-film evaporation.
{"title":"Mechanisms of Heat and Mass Transfer for Thin-Film Evaporation With Velocity Slip and Temperature Jump","authors":"Xiu Xiao, C. Yan, Yulong Ji","doi":"10.1115/mnhmt2019-4213","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4213","url":null,"abstract":"\u0000 Velocity slip and temperature jump at the solid-liquid interface are important phenomena in microchannel heat transfer. A comprehensive mathematical model considering both velocity slip condition and temperature jump at the solid-liquid interface is developed to understand the mechanisms of heat and mass transfer during thin-film evaporation in this paper. The model structure is established based on the lubrication theory, Clausius-Clapeyron equation and Young-Laplace equation. To better formulate the film evaporation process, three dimensionless parameters representing the effects of slip length coefficient, temperature jump and wall superheat degree respectively, are introduced in the present model. The analytical solution provides insight of film thickness and heat transfer characteristics for the evaporating thin film. It shows that as the slip length and temperature jump coefficient decrease, the length of evaporating thin film region is shortened and the location of maximum heat flux moves closer to the initial evaporating point. The effect of slip condition on heat flux is small, but the increase of temperature jump can reduce the peak heat flux significantly. Furthermore, the analysis on the three thermal resistances which are caused by temperature jump, conduction through liquid film and evaporation on liquid-vapor interface result in a better understanding for effective heat transfer during thin-film evaporation.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134430010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhi-chuan Sun, Yang Luo, Junye Li, Wei Li, Jingzhi Zhang, Zhengjiang Zhang, Jie Wu
The manifold microchannel heat sink receives an increasing number of attention lately due to its high heat flux dissipation. Numerical investigation of boiling phenomena in manifold microchannel (MMC) heat sinks remains a challenge due to the complexity of fluid route and the limitation of numerical accuracy. In this study, a computational fluid dynamics (CFD) approach including subcooled two-phase flow boiling process and conjugate heat transfer effect is performed using a MMC unit cell model. Different from steady-state single phase prediction in MMC heat sink, this type of modeling allows for the transient simulation for two-phase interface evolution during the boiling process. A validation case is conducted to validate the heat transfer phenomenon among three phases. Besides, this model is used for the assessment of the manifold dimensions in terms of inlet and outlet widths at the mass flux of 1300 kg/m2·s. With different ratios of inlet-to-outlet area, the thermal resistances remain nearly stable.
{"title":"Numerical Investigation of Flow Boiling in a Manifold Microchannel Heat Sink With Conjugate Heat Transfer","authors":"Zhi-chuan Sun, Yang Luo, Junye Li, Wei Li, Jingzhi Zhang, Zhengjiang Zhang, Jie Wu","doi":"10.1115/mnhmt2019-4042","DOIUrl":"https://doi.org/10.1115/mnhmt2019-4042","url":null,"abstract":"\u0000 The manifold microchannel heat sink receives an increasing number of attention lately due to its high heat flux dissipation. Numerical investigation of boiling phenomena in manifold microchannel (MMC) heat sinks remains a challenge due to the complexity of fluid route and the limitation of numerical accuracy. In this study, a computational fluid dynamics (CFD) approach including subcooled two-phase flow boiling process and conjugate heat transfer effect is performed using a MMC unit cell model. Different from steady-state single phase prediction in MMC heat sink, this type of modeling allows for the transient simulation for two-phase interface evolution during the boiling process. A validation case is conducted to validate the heat transfer phenomenon among three phases. Besides, this model is used for the assessment of the manifold dimensions in terms of inlet and outlet widths at the mass flux of 1300 kg/m2·s. With different ratios of inlet-to-outlet area, the thermal resistances remain nearly stable.","PeriodicalId":331854,"journal":{"name":"ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130707557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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