ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels最新文献

{"title":"Improved Boiling Heat Transfer in Dry Etched Microchannels With Laser Structured Surfaces","authors":"A. Sitar, M. Crivellari, J. Schillé, S. Mauersberger, U. Löschner, I. Golobič","doi":"10.1115/ICNMM2018-7726","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7726","url":null,"abstract":"The currently available microchannel fabrication techniques ranging from various etching methods and micro electrical discharge machining to laser microfabrication have some apparent advantages and weaknesses when compared one to another. Manufacturing process should satisfy several important criteria: diversity of the working material, the minimal fabricated feature size, the capability of 3D structuring, the precision and surface quality, maximum aspect ratio, the production costs, etc. This study focuses on combining the benefits of dry etching and laser structuring of a silicon substrate in order to produce microchannels with a capability of an improved heat transfer during boiling. The microchannels with a minimal cross section of 50×50 μm were etched in silicon and afterwards laser structuring was employed in order to make surface topography more appropriate for boiling heat transfer. The laser treatment resulted in micron sized cavities at the bottom of the microchannels, which lowered the temperature of the onset of boiling and improved the heat transfer during flow boiling. The performed combination of manufacturing methods proved to be complementary and cost effective.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122021586","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}

{"title":"Water-Silicone Oil Two-Phase Flow Hydrodynamics in a Square Glass Microchannel","authors":"Zan Wu, A. Svensson, J. Qian, B. Sundén","doi":"10.1115/ICNMM2018-7661","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7661","url":null,"abstract":"This work visualized water-silicone oil two-phase flow patterns both at the inlet cross-junction and in the main square microchannel with a channel width of 400 μm. Tubing/threading, dripping and jetting were identified at the inlet junction while annular, slug and droplet flows were categorized in the main microchannel at 50 mm downstream of the junction. Flow patterns were represented in terms of superficial velocities and dimensionless numbers. Compared to water-silicone oil flow, addition of surfactant sodium dodecyl sulfate (SDS) in water, with a dilute SDS concentration of 1000 ppm, narrows the dripping regime and widens the jetting regime at the inlet junction, while narrows the slug flow regime and widens the droplet flow regime in the main microchannel. A decrease in dynamic interfacial tension due to SDS addition is supposed to be the reason for such a flow pattern modification. Besides, for slug flow, the slug length can be scaled as a power law of the flow rate ratio and the Capillary number of the organic phase. The slug velocity is linearly dependent on the bulk average velocity for both cases with and without SDS addition.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129456974","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}

{"title":"Droplet Deformation and Breakup due to Shear Flow and Electric Field in a Confined Geometry","authors":"Rattandeep Singh, S. S. Bahga, Amit Gupta","doi":"10.1115/ICNMM2018-7641","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7641","url":null,"abstract":"In this work, the behavior of a spherical droplet suspended in a confined shear flow and subjected to an external electric field has been investigated. The continuous and dispersed fluids are treated as leaky dielectrics. The subsequent flow has been computed numerically using a low spurious current, multi-component lattice Boltzmann method coupled with a leaky dielectric model. The numerical model has been validated by analyzing droplet deformation due to shear flow and electric field separately. The results obtained are shown to be in good agreement with earlier published analytical solutions. Droplet elongation predicted by our simulations rises with increase in the electric field strength. Beyond a threshold value of electric field, breakup of droplet into smaller droplets is observed. Droplet breakup in case of fluids with equal viscosity is observed at low electric field strength as compared to low viscosity ratio drops.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123152438","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}

{"title":"Effect of By-Pass on the Heat Transfer Coefficient During Density Wave Oscillations in a Horizontal Mini-Channel","authors":"M. Fernandino, C. Dorao","doi":"10.1115/ICNMM2018-7684","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7684","url":null,"abstract":"Two phase flow instabilities and in particular density wave oscillations, DWO, are strongly dependent on the internal and external characteristics of the system. Although significant work has been done investigating the characteristics of the stability of the oscillations, the effect of the oscillations on the heat transfer coefficient demands further research. In this work, the influence of a parallel bypass to the test section on the heat transfer coefficient during density wave oscillations is studied. It is observed that in the case of small amplitude DWO the influence of the bypass is negligible, while for the case of large amplitude DWO that reach conditions of flow reversal the heat transfer coefficient can be enhanced. This fact is attributed to cold liquid entering at the outlet of the test section from the bypass preventing the dryout of the wall at high qualities.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123821457","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}

{"title":"Thermal Performance of Micro-Jet Impingement Device With Parallel Flow, Jet-Adjacent Fluid Removal","authors":"T. Bandhauer, David Hobby, C. Jacobsen, D. Sherrer","doi":"10.1115/ICNMM2018-7665","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7665","url":null,"abstract":"In a variety of electronic systems, cooling of various components imposes a significant challenge. A major aspect that inhibits the performance of many cooling solutions is the thermal resistance between the chip package and the cooling structure. Due to its low thermal conductivity, the thermal interface material (TIM) layer imposes a significant thermal resistance on the chip to cooling fluid thermal path. Advanced cooling methods that bypass the TIM have shown great potential in research and some specialty applications, yet have not been adopted widely by industry due to challenges associated with practical implementation and economic constraints. One advanced cooling method that can bypass the TIM is jet impingement. The impingement cooling device investigated in the current study is external to the integrated circuit (IC) package and could be easily retrofitted onto any existing microchip, similar to a standard heatsink. Jet impingement cooling has proven effective in previous studies. However, it has been shown that jet-to-jet interference severely degrades thermal performance of an impinging jet array. The present research addresses this challenge by utilizing a flow path geometry that allows for withdrawal of the impinging fluid immediately adjacent to each jet in the array.\u0000 In this study, a jet impingement cooling solution for high-performance ICs was developed and tested. The cooling device was fabricated using modern advanced manufacturing techniques and consisted of an array of micro-scale impinging jets. A second array of fluid return paths was overlain across the jet array to allow for direct fluid extraction in the immediate vicinity of each jet, and fluid return passages were oriented in parallel to the impinging jets. The following key geometric parameters were utilized in the device: jet diameter (D = 300μm), distance from jet to impinging surface (H/D = 2.5), spacing between jets (S/D = 8), spacing between fluid returns (Sr/D = 8), diameter of fluid returns (Dr/D = 5). The device was mounted to a 2cm × 2cm uniformly heated surface which produced up to 165W and the resulting fluid-to-surface temperature difference was measured at a variety of flow rates. For this study, the device was tested using single-phase water. Jet Reynolds number ranged from 300–1500 and an average heat transfer coefficient of 13,100 W m−2 K−1 was achieved at a Reynolds number of only Red = 305.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"141 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116536175","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}

{"title":"Electrokinetic Dispersion in Field Amplified Sample Stacking","authors":"Kaushlendra Dubey, Amit Gupta, S. S. Bahga","doi":"10.1115/ICNMM2018-7703","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7703","url":null,"abstract":"In this work, we performed an experimental study of electrohydrodynamic effects on the dispersion of sample ions in field amplified sample stacking (FASS). A typical FASS experiment involves a streamwise electrical conductivity gradient collinear to the applied electric field to enhance the sample stacking. Earlier studies on FASS have focused on how the conductivity gradient sets a non-uniform electro-osmotic flow which causes the dispersion. However, the coupling of the electric field with conductivity gradient leads to a destabilizing electric body force and generates unstable flow. This work demonstrates that generated body force influences the dynamics of FASS. We present a scaling analysis to show that at high fields, electrohydrodynamic effects play a vital role in sample dispersion. To justify our scaling arguments, we performed experiments at varied electric fields which shows that at high electric fields maximum concentration enhancement is lowered significantly. To ensure the EHD effects on the dynamics of FASS, we have also performed experiments with suppressed EOF conditions.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"126 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128064195","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}

{"title":"Visualization of Two-Phase Flow in 3D Printed Polycarbonate Pulsating Heat Pipe With Aluminum Substrate","authors":"T. Arai, M. Kawaji, Yasushi Koito","doi":"10.1115/ICNMM2018-7677","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7677","url":null,"abstract":"A pulsating heat pipe (PHP) is a passive device with a good heat transport capability compared to other heat pipes. This paper describes an experimental investigation of a PHP with a serpentine channel fabricated by using a 3-D printer. The configuration of the flow channels in the PHP was close to that of commercially available PHPs made entirely of aluminum. To improve the heat transport capability and enable flow visualization, an aluminum plate was used on one side as the heat-transfer surface, on which transparent flow channels were fabricated by a 3-D printer and a polycarbonate filament. The interface between the aluminum plate and polycarbonate flow channel was cemented with a heat-resistant glue to ensure long term sealing. HFE-7000 was used as a working fluid. Oscillating two-phase flow in the PHP was observed with a high-speed digital video camera and transient surface temperatures at evaporator, insulator and condenser sections were measured by fine diameter thermocouples. The two-phase flow and thermal characteristics of the PHP at different heater power levels are presented.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128121877","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}

{"title":"System and Component Transport Considerations of Micro-Pin Based Solar Receivers With High Temperature Gaseous Working Fluids","authors":"B. Fronk, S. A. Jajja","doi":"10.1115/ICNMM2018-7614","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7614","url":null,"abstract":"This paper explores the interactions between micro-pin concentrated receiver designs with overall solar thermal energy system performance, with different operating conditions, working fluid, and required materials of construction. A 320 MW thermal plant coupled to a 160 MW electric sCO2 Brayton cycle is considered as the baseline. The circulating fluid enters the receiver at 550°C, and leaves at 720°C. The thermal storage/power block are located 150 m from the receiver at the base of the receiver tower. A resistance network based thermal and hydraulic model is used to predict heat transfer and pressure drop performance of the micro-pin receiver. This output of this model is coupled to a system level model of the pressure loss and compressor power required in the remainder of the high temperature gas loop. Overall performance is investigated for supercritical carbon dioxide and helium as working fluids, at pressures from 7.5 to 25 MPa, and at delivery temperatures of 720°C. The results show that by modifying pin depth and flow lengths, there are design spaces for micro-pin devices that can provide high thermal performance without significantly reducing the overall solar thermal system output at lower operating pressures. Use of lower pressure fluids enables lower cost materials of construction in the piping and distribution system, reducing the cost of electricity.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134544458","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}

{"title":"Modeling of Flow Distribution in Proton Exchange Membrane Fuel Cell","authors":"Omid Babaie Rizvandi, S. Yeşilyurt","doi":"10.1115/ICNMM2018-7658","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7658","url":null,"abstract":"Analysis and design of flow fields for proton exchange membrane fuel cell (PEMFC) require coupled solution of the flow fields, gas transport and electrochemical reaction kinetics in the anode and the cathode. Computational cost prohibits the widespread use of three-dimensional models of the anode and cathode flow fields, gas diffusion layers (GDL), catalyst layers (CL) and the membrane for fluid flow and mass transport. On the other-hand, detailed cross-sectional two-dimensional models cannot resolve the effects of the anode and cathode flow field designs. Here, a two-dimensional in-plane model is developed for the resolution of the effects of anode and cathode flow channels and GDLs, catalyst layers are treated as thin-layers of reaction interfaces and the membrane is considered as a thin-layer that resist the transfer of species and the ionic current. Brinkman equations are used to model the in-plane flow distribution in the channels and the GDLs to account for the momentum transport in the channels and the porous GDLs. Fick’s law equations are used to model transport of gas species in the channels and GDLs by advection and diffusion mechanisms, and electrochemical reactions in the CL interfaces are modeled by Butler-Volmer equations. Complete features of the flow in the channels and inlet and outlet manifolds are included in the model using resistance relationships in the through-plane direction. The model is applied to a small cell having an active area of 1.3 cm2 and consisting of 8 parallel channels in the anode and a double serpentine in the cathode. Effects of the anode and cathode stoichiometric ratios on the cell performance and hydrogen utilization are investigated. Results demonstrate that for a sufficiently high cathode stoichiometric ratio enough, anode stoichiometric ratio can be lowered to unity to obtain very high hydrogen utilization and output power.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122220574","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}

{"title":"Mechanisms Underlying Foam-Based Electronucleation of Hydrates","authors":"Palash V. Acharya, Denise Lin, V. Bahadur","doi":"10.1115/ICNMM2018-7721","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7721","url":null,"abstract":"Nucleation of clathrate hydrates at low temperatures is constrained by very long induction (wait) times, which can range from hours to days. Electronucleation (application of an electrical potential difference across the hydrate forming solution) can significantly reduce the induction time. This work studies the use of porous open-cell foams of various materials as electronucleation electrodes. Experiments with tetrahydrofuran (THF) hydrates reveal that aluminum and carbon foam electrodes can enable voltage-dependent nucleation, with induction times dependent on the ionization tendency of the foam material. Furthermore, we observe a non-trivial dependence of the electronucleation parameters such as induction time and the recalescence temperature on the water:THF molar ratio. This study further corroborates previously developed hypotheses which associated rapid hydrate nucleation with the formation of metal-ion coordination compounds. Overall, this work studies various aspects of electronucleation with aluminum and carbon foams.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121363263","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}